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Microbial Quality of the Avon River
The effect of major earthquakes and
subsequent sewage discharges on the quality
of the water and sediments in the Avon River
Follow on study
Prepared as part of scientific services to
Environment Canterbury
by
Elaine Moriarty, Megan Devane
and Brent Gilpin
June 2013
Technical Report
(CSC 13006)
Microbial Quality of the Avon River
The effect of major earthquakes and
subsequent sewage discharges on the quality
of the water and sediments in the Avon River
Follow on study
Water Programme Manager
John Wright
Project Leader Peer Reviewer
Dr Elaine Moriarty Dr Louise Weaver
Client Report
(CSC 13006)
DISCLAIMER
This report or document ("the Report") is given by the Institute of Environmental Science
and Research Limited ("ESR") for the benefit of Environment Canterbury as defined in the
respective Contracts between ESR and above parties, and is strictly subject to the
conditions laid out in those Contracts.
Neither ESR nor any of its employees makes any warranty, express or implied, or assumes
any legal liability or responsibility for use of the Report or its contents by any other person
or organisation.
ACKNOWLEDGMENTS
We would like to acknowledge the cooperation of staff from Environment Canterbury and
Christchurch City Council for contributing to this project.
Avon River post Earthquake – Follow up study June 2013
TABLE OF CONTENTS
1. INTRODUCTION .................................................................................................... 7
1.1. Focus of this report ............................................................................................. 9
1.2. Microorganisms examined in this study ........................................................... 10
1.3. Faecal source tracking ....................................................................................... 10
1.4. Faecal Aging of river water .............................................................................. 11
2. Sampling locations and Sample analysis .............................................................. 11
3. Results ...................................................................................................................... 12
3.1. E. coli in Avon River water .............................................................................. 12
3.2. E. coli in Avon River Sediment ........................................................................ 13
3.3. Bacteriophage in Avon River water .................................................................. 15
3.4. Bacteriophage in Avon River sediment ............................................................ 15
3.5. Bacteriophage in estuarine sediment ................................................................. 15
3.6. Enterococci in estuarine sediment ..................................................................... 17
3.7. Campylobacter spp. .......................................................................................... 18
3.8. Cryptosporidium and Giardia spp. ................................................................... 20
3.9. Comparisons during discharge immediately post-discharge and 2013 ............. 22
3.10. Faecal Source Tracking (FST) in Avon River water and selected sediments ... 24
3.11. Faecal ageing tools for faecal source tracking .................................................. 28
4. Discussion ................................................................................................................ 29
4.1. Microorganisms in river water .......................................................................... 29
4.2. Microorganisms in Sediment ............................................................................ 30
4.3. Faecal Aging ..................................................................................................... 31
5. Conclusion ............................................................................................................... 32
6. References ................................................................................................................ 34
Appendix 3: faecal sterol analysis .................................................................................... 38
Avon River post Earthquake – Follow up study June 2013
LIST OF TABLES
Table 1 Microorganisms tested for in the study................................................................... 10
Table 2 Sampling Sites and abbreviations used. .................................................................. 11
Table 3 Mean levels of microorganisms in the river water during discharge, post-discharge
and the present study ............................................................................................................ 22
Table 4 Mean levels of microorganisms in the sediment during discharge, post-discharge
and the present study ............................................................................................................ 23
Table 5: PCR Markers identified in water samples collected from Avon River March-
April, 2013 ........................................................................................................................... 25
Table 6: Faecal Sterol ratios for Avon River water and sediments ..................................... 26
Table 7: Summary of collated Faecal Source Tracking results in Avon River water and
sediments.............................................................................................................................. 27
Table 8: Specificity of PCR markers used in the Avon River study ................................... 36
Table 9: Interpretation of the presence/absence of the three Human PCR markers ............ 37
Table 10: Raw Data for Faecal Sterols identified in Avon River water and sediments ...... 38
Table 11: Key for interpretation of sterol ratios .................................................................. 39
Avon River post Earthquake – Follow up study June 2013
LIST OF FIGURES
Figure 1 Location of sampling sites ..................................................................................... 12
Figure 2 Concentration of E. coli present in Avon River water, sediment and estuarine
sediment ............................................................................................................................... 14
Figure 3 Concentration of Bacteriophage present in Avon river water, sediment and
estuarine sediment ................................................................................................................ 16
Figure 4 Concentration of enterococci present in estuarine sediment ................................. 17
Figure 5 Concentration of Campylobacter spp. present in Avon river water, sediment and
estuarine sediment ................................................................................................................ 19
Figure 6 Concentration of Cryptosporidium spp. present in Avon river sediment and
estuarine sediment ................................................................................................................ 20
Figure 7 Concentration of Giardia spp. present in Avon river sediment and estuarine
sediment ............................................................................................................................... 21
Figure 8: Faecal aging ratio versus E. coli concentration in Avon River water (2011-2013)
.............................................................................................................................................. 28
Avon River post Earthquake – Follow up study June 2013
EXECUTIVE SUMMARY
The 2010/2011 Christchurch earthquakes resulted in direct sewage discharges to the Avon
River of more than 10,000 cubic meters a day for almost a year. A study (March 2011-
March 2012) was undertaken to use this unusual situation to 1) re-evaluate the validity of
E. coli as an indicator of public health risk following contamination events; 2) to evaluate
the relationship between concentrations of indicator bacteria and pathogens in recreational
water during active sewage discharges, and in the period following cessation of sewage
discharges; and 3) to investigate the potential of riverbed and seabed sediments to act as a
sink for indicator bacteria and pathogens that might then be re-mobilized with disturbance.
The samples for this study were taken during “Active Discharges” of sewage to the Avon
(March 2011-Sept 2011) and “Post Active Discharges” (Sept 2011-Mar 2012). The
findings of this study are reported in “The effect of major earthquakes and subsequent
sewage discharges on the quality of the water and sediments in the Avon River”, Moriarty
et al 2012.
The Current Study (March - May 2013) was undertaken with the following aims:
Evaluate the current state of the water and sediments in the Avon River and
estuarine sites and compare results with those found in the previous 2011-2012
study.
Ensure public health messages are accurately reflecting recent water and sediment
microbial quality.
The key findings of this current study are:
The Boatsheds site has similar water quality to that seen during Active Discharge to
the Avon River. Faecal source tracking tools (FST) have indicated the likely
sources of pollution at the Boatsheds to be wildfowl, with intermittent human
pollution.
The water quality at Kerrs Reach is also polluted with the average E. coli
concentrations close to those seen during Active Discharge (2011). FST results
indicate fresh human inputs as well as wildfowl faeces.
Avon River post Earthquake – Follow up study June 2013
Owles Terrace has seen the greatest improvement in water quality when the levels
of E. coli are compared to those seen During and Post Active Discharge. FST
analysis has reported the source of E. coli as wildfowl.
The results from this study showed a marked decrease in Giardia concentrations in
sediments, which indicates the long term quality of the water is improving.
All sites, except Kerrs Reach, had a decrease in average concentration of all
microorganisms tested for in the sediment.
The two estuarine sediment sites showed significant decrease in indicator microbial
concentrations compared with the During and Post Active Discharge samples
(2011-2012). This indicates that there is no significant health risk related to contact
with the estuarine sediments based on these results.
Recreational contact with the Avon river water, sediment and estuarine sediments,
particularly at Kerrs Reach, may continue to pose health risks, and the public
should continue to minimize ingestion of the water.
Avon River post Earthquake – Follow up study June 2013
ABBREVIATIONS
AC/TC ratio Atypical Coliforms/Total Coliforms
AdV adenovirus
CCC Christchurch City Council
CFU Colony Forming Units
CV Coefficient of variance
CI Confidence interval
FST Faecal source tracking
FWA Fluorescent Whitening Agents
M Magnitude (earthquake)
MfE Ministry for the Environment
MPN Most Probable Number
ND Not detected
NT Not tested
NIWA National Institute of Water and Atmospheric Research
PCR Polymerase Chain Reaction
Avon River Post Earthquake – Follow on study June 2013
1. INTRODUCTION
The Avon River is an intrinsic feature of the urban environment of Christchurch City and
is popular for recreational and tourist activities. The Avon River traverses the city from its
source in the western suburb of Avonhead through Hagley Park and the Central Business
District to the eastern suburbs. It departs the built environment at the northern entrance to
the Avon-Heathcote Estuary before amalgamating with the Heathcote River to flow into
Pegasus Bay.
Urban rivers are susceptible to intermittent impacts from industrial and human effluents. In
addition, animal faecal scats, including wildfowl, may cause deterioration in the quality of
the water. Contamination of water from these faecal sources of pollution can result in
increased risks of microbial diseases. Microbial water quality is measured by enumerating
the presence of the bacteria Escherichia coli, which is common in faecal material. The New
Zealand Microbiological Water Quality Guidelines for Marine and Freshwater
Recreational Areas (MfE, 2003) state that freshwater containing less than 260 E. coli per
100 mL is acceptable.
The Avon River has been monitored at various locations by the Christchurch City Council
(CCC) and Environment Canterbury (ECan) over many years. A 2009 study applied faecal
source tracking tools (faecal sterol analysis, fluorescent whitening agents, and PCR
markers) to better understand contamination (Moriarty and Gilpin, 2009). This study found
that the primary sources of water quality degradation in the Avon River appeared to be
related to wildfowl and possibly dog faecal material. Rainfall resulted in significant
degradation of the microbial water quality of the Avon River due both to wildfowl and dog
faeces being washed into the river, and some low level human sewage inputs from the
sewage system.
Following the major Christchurch earthquake on 22nd
Feb 2011, a study was commissioned
to 1) re-evaluate the validity of E. coli as an indicator of public health risk following
contamination events; 2) to evaluate the relationship between concentrations of indicator
bacteria and pathogens in recreational water during active sewage discharges, and in the
period following cessation of sewage discharges; and 3) to investigate the potential of
Avon River Post Earthquake – Follow on study June 2013
riverbed and seabed sediments to act as a sink for indicator bacteria and pathogens that
might then be re-mobilised with disturbance. Water and sediment samples were collected
from three sites on the Avon River – Antigua Boatsheds, Kerrs Reach and Owles Terrace,
sediment samples from two estuary sites – Penguin Street and Humphreys Drive, and
beach sand from Cave Rock, Sumner. All samples were collected between April 2011 and
March 2012. Samples were tested for the presence of microbial water quality indicators
(E. coli, enterococci, bacteriophage and Clostridium perfringens), potential pathogens
(Campylobacter, Giardia and Cryptosporidium), and faecal source tracking markers (PCR
markers, faecal sterols and fluorescent whitening agents (FWAs)).
The key findings of the previous study were:
After a major faecal contamination event, measurement of E. coli in the waterway
is a suitable indicator for establishing a public health risk. The New Zealand
Microbiological Water Quality Guidelines for Marine and Freshwater
Recreational Areas (MfE, 2003) specify levels of E. coli above 550 per 100 mL as
Action/Red Mode level. In this study E. coli levels in water above 550 were
correlated with an increased likelihood of detection of potential pathogens
including Campylobacter, Giardia and Cryptosporidium. While E. coli could be
detected in sediments throughout the study, levels were generally lower than in the
water suggesting minimal impact of sediment borne E. coli on recreational water
quality monitoring.
Overall, levels of pathogens were lower than may have been expected due to high
levels of groundwater infiltration into the sewage, which acted to dilute
microorganisms present. This was evident by the decreased concentration of
microorganisms and increased volume of raw sewage entering the wastewater
treatment plant. There was also no increase in community levels of infection, which
together with the groundwater infiltration, resulted in lower levels of pathogens in
the sewage entering the Avon River. The health risks were therefore less than may
have been expected.
Giardia was the pathogen found most frequently and at the highest levels. It was
found in water samples where the faecal sources could be attributed to human
sewage and to wildfowl sources. Further study would be needed to assess the
viability and source of these protozoa.
Avon River Post Earthquake – Follow on study June 2013
All the microorganisms tested in this study could be recovered from sediments. The
indicator bacteria Clostridium perfringens accumulated in the sediments, and there
is evidence to support the low level persistence of Cryptosporidium and Giardia in
sediments after cessation of sewage discharges. Bacteriophage and Campylobacter
species do not appear to accumulate in the Avon river sediments. Faecal sterols
and FWAs accumulated in the sediments.
It is well documented that microorganisms can survive for long periods of time in
riverbed sediment. In the event of disturbances of the sediment, it is highly
probable that there could be re-mobilisation of microorganisms, including
pathogens into the water column. Chemical contaminants in the sediment may also
be re-mobilised. Resuspension events, therefore, increase the potential of risk to
human health for those who participate in recreational and work-related activities in
the river environment.
Faecal source tracking tools (Faecal sterols, fluorescent whitening agents and PCR
markers) are valuable for confirming when elevated levels of E. coli are due to
human sources, and when they are the result of inputs from wildfowl, dogs or other
sources. The faecal source tracking markers identified in the water column
represent a snapshot of contamination at the time of sampling. In contrast, the
contamination signature in the underlying sediment is presenting a historical picture
of the impact of pollution inputs to a river system and does not appear to be
correlated with real-time events. There remains a need for assessing the health risks
of water primarily impacted by non-human sources, in particular wildfowl.
1.1. Focus of this report
This report is a follow up to the previous Avon River studies to determine the
concentration of microorganisms in the Avon River water and sediments, and in estuarine
sediments relative to these previous studies. Public health messages relating to
recreational water quality of the city waterways since the publication of the ‘Microbial
Quality of the Avon River’ report (ESR 2012) have referred to the report findings that
indicated some of the pathogens tested had accumulated in the sediments post-quake and
could be re-suspended following disturbance from recreational activity.
Avon River Post Earthquake – Follow on study June 2013
It has been a year since the last sampling occasion in the post-quake study and in order to
ensure that the public health message remains relevant a further study was undertaken to
establish the on-going concentrations of indicators and pathogens present in Avon River
sediments.
1.2. Microorganisms examined in this study
This report describes microbial characterisation of water and sediments from three sites on
the Avon River and sediments from two sites in the Avon/Heathcote Estuary.
Methodological details for analyses of target organisms and full description of the
organisms are described in the previous progress report (Moriarty et al., 2012).
Table 1 Microorganisms tested for in the study
Organisms Water Sediment
E. coli
Yes Yes
enterococci No Estuarine sediment only
Campylobacter spp.
Yes Yes
Bacteriophage
Yes Yes
Cryptosporidium spp.
No Yes
Giardia spp.
No Yes
1.3. Faecal source tracking
A range of faecal source tracking (FST) tools can identify whether faecal pollution is from
human, dog or wildfowl sources (Field and Samadpour, 2007). In this study, FST tools
were applied to a limited number of samples where the concentrations of microorganism
Avon River Post Earthquake – Follow on study June 2013
present warranted further investigation. FST markers evaluated were faecal sterols
(indicative of human and wildfowl sources), fluorescent whitening agents (FWAs)
(indicative of human sources) and PCR-based molecular markers (indicative of human,
wildfowl and dog sources).
1.4. Faecal Aging of river water
A secondary investigation to FST in the Avon River was to explore potential tools that
provide clarity around the aging of the faecal pollution identified in the river. One of the
tools trialled in this study was a faecal aging ratio, which relies on the comparison between
stable indigenous microflora concentrations in the river system and the total coliform
concentrations that rise after a fresh faecal input to the river. The aging ratio is called
AC/TC, which is taken from the numbers of atypical colonies (AC) on the standard method
plate assay for Total Coliforms (TC). The atypical colonies represent the indigenous river
microflora. Ratios of AC/TC are low (< 1 for fresh human sewage; Brion, 2005) because
concentrations of TC are high, and the ratio increases as the faecal input ages and total
coliforms die-off.
2. Sampling locations and Sample analysis
Three sites along the Avon River and three sites within the Avon/Heathcote Estuary were
chosen for analysis (Table 2 and Figure 1) and were sampled three times between March
and April 2013.
Table 2 Sampling Sites and abbreviations used.
Abbreviation used Site Sample type
BS Antigua Boatsheds River water and sediments
KR Kerrs Reach River water and sediments
OT Owles Terrace River water and sediments
PS Penguin St Estuarine sediments
HD Humphreys Drive Estuarine sediments
Avon River Post Earthquake – Follow on study June 2013
Figure 1 Location of sampling sites
3. Results
3.1. E. coli in Avon River water
The concentration of E. coli in Avon river water sediment and estuarine sediment from
April 2011 to April 2013 is shown in Figure 2 and a summary of the data is displayed in
Table 3 and Table 4. At the Boatsheds, the average E. coli concentration in this study
(1,035 cfu per 100 ml) is lower in average concentration compared with the Active
Discharge average concentration (average 1,338per 100 ml) and the Post Discharge
average concentration (1,629 E. coli per 100 ml).
The concentration of E. coli in the water at Kerrs Reach during the 2013 sampling (average
3,523 E. coli per 100 ml) was lower than the average concentration while direct sewage
discharges were occurring (4,600 E. coli per 100 ml). It was significantly higher than the
level recorded following the cessation of sewage discharges at Kerrs Reach
(1,893 E. coli per 100 ml).
Antigua Boatsheds
Kerrs Reach
Owles Terrace
Penguin Street Humphreys Drive
Cave Rock
Penguin Street
Avon River Post Earthquake – Follow on study June 2013
On all three sampling occasions in 2013, Owles Terrace had the lowest concentration of
E. coli relative to the other two upstream sites. The first two samples (650 and 750 E. coli
per 100 ml) were similar in concentration to those seen post sewage discharge. The final
sample (240 E. coli per 100 ml) was the lowest recorded at this site over the period of our
study.
3.2. E. coli in Avon River Sediment
The concentration of E. coli in the sediment at the Boatsheds during the 2013 sampling
(average 132 E. coli per g dry weight) was significantly lower than that during known
sewage discharges (average 1,287 E. coli per g dry weight) and similar to those seen post
discharge (average 250 E. coli per g dry weight).
The concentration of E. coli at Kerrs Reach was significantly different to the other sites
with the highest concentration of E. coli recorded (91, 635 E. coli per g dry weight) over
the course of the two year study. All three 2013 samples were higher than the average
concentration seen during active sewage discharges (2,875) E. coli per g dry weight) and
following the cessation of discharges (5,119) E. coli per g dry weight). It must be noted
due to problems with access to the river at Kerrs Reach the 2nd
and 3rd
sampling of 2013
were taken approximately 50 m downstream of the other samples, close to the last pontoon
in the vicinity of Christ’s College Boat Club.
The concentration of E. coli in the sediment at Owles Terrace appears to be decreasing
over time. The average concentration seen during the 2013 sampling (144 E. coli per g
sediment dry weight), was significantly lower than those during direct discharges
(3,603 E. coli per g dry weight) and following discharges (620 E. coli per g sediment dry
weight).
The two estuarine sites sampled in this study were Penguin St and Humphreys Drive. In
this round of sampling all sediment samples at the estuarine sites contained six or less E.
coli per g of sediment dry weight. These counts were similar to those seen in estuarine
sediments since Nov 2011, when the estuary ceased to be impacted by discharges.
Avon River Post Earthquake – Follow on study June 2013
Figure 2 Concentration of E. coli present in Avon River water, sediment and
estuarine sediment
2011 2012 2013
2011 2012 2013
2011 2012 2013
Mar Apr May
Mar Apr May
Mar Apr May
Avon River Post Earthquake – Follow on study June 2013
3.3. Bacteriophage in Avon River water
Bacteriophage (phage) concentrations were determined as an indicator of the presence of
pathogenic viruses in the samples. Phage were detected on one occasion in 2013 at the
Boatsheds and was at a low level (50 Phage per 100 ml of water). At Kerrs Reach phage
were detected on the first two sampling occasions. These were at concentrations (100 per
100 ml water) similar to those seen post discharge (average 158 phage per 100 ml water)
and significantly lower than during discharges (2263 phage per 100 ml). Phage was
detected once during the 2013 sampling at Owles Terrace (150 phage per 100 ml water).
Phage was intermittently detected at Owles Terrace following cessation of active
discharges (average 33 phage per 100 ml), significantly lower than during active sewage
discharges (2200 phage per 100 ml).
3.4. Bacteriophage in Avon River sediment
Phage was not detected in any of the Avon river sediment samples during the 2013
sampling. Following the cessation of direct sewage discharges (October 2011) phage has
only been detected once at each of the river sediment sampling sites.
3.5. Bacteriophage in estuarine sediment
Phage was detected in one sample from Humphreys Drive and never from the Penguin St
samples during the current 2013 sampling. Over the course of the two year study phage
have been detected on three occasions at Penguin St and once at Humphreys drive. The
concentration detected at Humphreys drive (12.8 phage per g sediment dry weight) was
significantly lower than previously detected at Humphreys Drive during active sewage
discharge (74 phage per g sediment dry weight).
Avon River Post Earthquake – Follow on study June 2013
Figure 3 Concentration of Bacteriophage present in Avon river water, sediment and
estuarine sediment
2011 2012 2013
2011 2012 2013
2011 2012 2013
Mar Apr May
Mar Apr May
Mar Apr May
Avon River Post Earthquake – Follow on study June 2013
3.6. Enterococci in estuarine sediment
The presence of enterococci was analysed for in the estuarine sediment samples taken from
Humphreys drive and Penguin St. The concentration of enterococci present in the sediment
at Penguin St has been steadily decreasing since direct discharges to the estuary ceased.
During discharge the sediment contained an average of 566 enterococci per g of sediment
dry weight, decreasing to 99 enterococci per g dry weight following cessation of
discharges and reducing to 8 enterococci per g dry weight in 2013.
The concentration of enterococci present in the sediment at Humphreys Drive has also
been steadily decreasing since direct discharges to the estuary ceased. During discharge an
average of 330 enterococci per g of sediment dry weight were present, decreasing to 36
enterococci per g dry weight following cessation of discharges and finally 27 enterococci
per g dry weight in 2013.
Figure 4 Concentration of enterococci present in estuarine sediment
2011 2012 2013
Mar Apr May
Avon River Post Earthquake – Follow on study June 2013
3.7. Campylobacter spp.
All water and sediment samples were tested for the presence of Campylobacter spp.. It was
detected on all three sampling occasions at each of the river water sampling sites in 2013.
The concentration in the water ranged from 2.3 to 46 campylobacter MPN (most probable
number) per 100 ml. While numbers at The Boatsheds and Owles Terrace were low, Kerrs
Reach had the highest concentrations (46 mpn per 100 ml on date) seen since sewage
discharges ceased.
In the river sediment samples Campylobacter spp. was detected only in the sediments in
Kerrs Reach during the 2013 sampling. Previously, Campylobacter spp had been detected
in all sediment samples over the course of the study, at low concentrations. The level of
campylobacter detected in the sediment at Kerrs Reach on the second sampling occasion of
2013 (11.08 mpn per g sediment dry weight) was the highest seen throughout the study.
Campylobacter spp was detected again at Kerrs Reach on the final sampling occasion , but
was significantly lower than the previous sample (0.54 mpn per g dry weight).
Campylobacter spp was not detected at any of the estuarine sediment samples sampled in
2013.
All isolates of campylobacter were confirmed by PCR and speciated. Of the 33 isolates
analysed, two were thermotolerant campylobacter, two contained both C. jejuni and
C. coli and the remaining 29 isolates contained C. jejuni only.
Avon River Post Earthquake – Follow on study June 2013
Figure 5 Concentration of Campylobacter spp. present in Avon river water, sediment
and estuarine sediment
2011 2012 2013
2011 2012 2013
2011 2012 2013
Mar Apr May
Mar Apr May
Mar Apr May
Avon River Post Earthquake – Follow on study June 2013
3.8. Cryptosporidium and Giardia spp.
In the 2013 study, only the sediment samples were analyzed for Cryptosporidium and
Giardia spp.. Cryptosporidium spp. were detected at low levels on two occasions at
Penguin St, and all other samples were negative for Cryptosporidium spp.. Giardia spp.
which had previously been detected at very high levels (2,254 cysts per g dry weight
sediment) was detected on three occasions during the 2013 sampling; twice at Penguin St
and once at Kerrs Reach. These samples all contained low concentrations of Giardia spp.
(<1 per g dry weight sediment) and may have come from a number of environmental
sources such as birds, dogs etc.
Figure 6 Concentration of Cryptosporidium spp. present in Avon river sediment and
estuarine sediment
Mar Apr May
2011 2012 2013
Avon River Post Earthquake – Follow on study June 2013
Figure 7 Concentration of Giardia spp. present in Avon river sediment and estuarine
sediment
Mar Apr May Mar Apr May
2011 2012 2013
Avon River Post Earthquake – Follow on study June 2013
3.9. Comparisons during discharge immediately post-discharge and 2013
Table 3 Mean levels of microorganisms in the river water during discharge, post-
discharge and the present study
Organism Time Boatsheds Kerrs Reach Owles Terrace
E. coli
CFU per 100
mL
During
discharge
1,338 4,600 17,975
Post discharge 1,629 1,893 1,493
Current study 1,035 3,523 547
Bacteriophage
PFU per 100
mL
During
discharge
425 2,263 2,200
Post discharge 67 158 33
Current study 17 100 50
Campylobacter
spp.
MPN per 100
mL
During
discharge
2 32 45
Post discharge 3 5 4
Current study 5 32 6
Dates: During discharge: 1st April – 8
th Sept 2011(n=4)
Post discharge: 27th
Sept – March 2012 (n=7)
Current study: March-April 2013 (n=3)
Avon River Post Earthquake – Follow on study June 2013
Table 4 Mean levels of microorganisms in the sediment during discharge, post-
discharge and the present study
Organism Time Boatsheds Kerrs
Reach
Owles
Terrace
Humphreys
Drive
Penguin
St
E. coli
CFU g dw
During
discharge 1,287 2,875 3,603 134 82
Post
discharge 250 5,119 620 48 9
Current study 132 43,661 144 1 3
Bacteriophage
PFU gdw
During
discharge 16 41 41 27 19
Post
discharge 1 2 2 6 0
Current study 0 0 0 0 4
Campylobacter
spp.
g dw
During
discharge 0 2 3 2 1
Post
discharge 1 0 0 0 0
Current study 0 4 0 0 0
enterococci
During
discharge
Not tested
284 330
Post
discharge 366 36
Current study 8 27
Cryptosporidium
spp. gdw
During
discharge 1.0 0.4 0.8 0.2 0.0
Post
discharge 57.3 8.9 4.6 0.0 0.2
Current study 0.0 0.0 0.0 0.3 0.0
Giardia spp.
gdw
During
discharge 23.6 8.6 10.3 0.3 0.0
Post
discharge 431.8 47.1 21.1 0.4 2.1
Current study 0.0 0.3 0.0 0.1 0.0
Dates: During discharge: 1st April – 8
th Sept 2011
Post discharge: 27th
Sept – March 2012 Current study: March-April 2013
Avon River Post Earthquake – Follow on study June 2013
3.10. Faecal Source Tracking (FST) in Avon River water and selected sediments
Faecal source tracking tools (PCR markers, faecal sterols and fluorescent whitening
agents) were applied to all river water samples collected and three sediment samples from
Kerrs Reach and the Boatsheds (Table 5 and Table 6) with final FST interpretations in
Table 7. Additional information on interpretation of FST tools can be found in Appendices
2 and 3.
All of the river water samples analysed by FST tools had elevated levels of E. coli, with
the exception of a sample from Owles Terrace collected on 8th
April, which was below the
alert level for recreational water. All samples contained > 2000 parts per trillion (ppt) of
sterols which is sufficient for interpretation of sterol ratios. FST analysis of river water on
11th
March 2013 identified only wildfowl faecal contamination at the three sites, the
Boatsheds, Kerrs Reach and Owles Terrace. On 25th
March human faecal pollution was
identified in river water at the Boatsheds and Kerrs Reach. In addition, wildfowl faecal
pollution was identified at all three sites. The low level of Human PCR marker BiAdo at
Owles Terrace is suggestive of seagull contamination (Appendix 2) rather than human.
River water analysis on 8th
April identified human contamination at all three sites and
wildfowl pollution at the Boatsheds and Kerrs Reach. Very low levels of Fluorescent
Whitening Agents (FWAs) were also detected in the water samples from the Boatsheds
and Kerrs Reach on 8th
April. The canine PCR marker was not detected in water analysed
in the current study. Faecal sterol analysis of sediment samples (Table 6) reported wildfowl
and plant decay as the likely sources of sterols.
Avon River Post Earthquake – Follow on study June 2013
Table 5: PCR Markers identified in water samples collected from Avon River March-April, 2013
Date
2013
Location PCR markers Interpretation
Genbac3 BiAdo HumM3 BacH
Reischer
GFD
Bird
E2
Duck
DogBac
11-
Mar
Boatsheds ++++ ND ND + + ++ ND wildfowl
Kerrs
Reach
++++ ND ND ND ++ +++ ND wildfowl
Owles
Tce
++++ ND ND ND + ND ND wildfowl
25
Mar
Boatsheds ++++ +++ ND + ++ ++++ ND (aged/low level)
human, wildfowl
Kerrs
Reach
++++ +++ + + + +++ ND human, wildfowl
Owles
Tce
++++ + ND ND ++ ND ND (aged?) low level
human, wildfowl
8-Apr Boatsheds ++++ +++ ND + ++ ++++ ND human, wildfowl
Kerrs
Reach
++++ +++ ND + ND ++ ND human, wildfowl
Owles
Tce
++++ + ND ND ND ND ND aged/low level
human
+ = very weak positive
++ = weak positive
+++ = positive
++++ = strong positive
Avon River Post Earthquake – Follow on study June 2013
Table 6: Faecal Sterol ratios for Avon River water and sediments
Faecal Ratios Human Indicative Ruminant Indicative Wildfowl Indicative Plant
**Interpretation Location
Sample
Type
Date
2013
F1 F2 H3 H1 H2 H4 R3 R1 R2 A1 A2 P1
>0.5* >0.5 >1 >5
% >0.7
>75
% <1
>5
%
<30
% ≥0.30 ≥0.67 >4
Boatsheds water 11-Mar 0.54* 0.42 1.3 3.9 0.35 56.8 15.4 2.9 56.8 0.68 0.61 15.4 wildfowl/plant
decay
Kerrs Reach water 11-Mar 0.25 0.59 1.0 1.3 0.20 50.8 25.8 1.3 50.8 0.61 0.78 25.8 wildfowl/plant
decay
Owles
Terrace water 11-Mar 0.37 0.52 1.7 1.9 0.27 63.6 18.3 1.1 63.6 0.61 0.69 18.3
wildfowl/plant
decay
Boatsheds water 25-Mar 0 . 9 1 1.25 0.9 3.2 0.48 47.4 11.8 3.6 47.4 0.43 0.49 11.8 Wildfowl/plant
decay
Kerrs Reach water 25-Mar 0.69 1.40 1.4 3.1 0.41 58.9 11.8 2.1 58.9 0.41 0.57 11.8 Wildfowl/plant
decay
Owles
Terrace water 25-Mar 0.41 1.02 1.1 1.2 0.29 53.3 11.4 1.1 53.3 0.45 0.67 11.4
Wildfowl/plant
decay
Boatsheds water 8-Apr 1.08 2.22 0.7 4.3 0.52 41.1 5.9 6.1 41.1 0.30 0.45 5.9 #plant decay
Kerrs Reach water 8-Apr 0.28 4.07 1.0 3.4 0.22 50.8 8.8 3.3 50.8 0.19 0.77 8.8 Wildfowl/plant
decay
Owles
Terrace water 8-Apr 1.19 3.03 1.6 4.5 0.54 61.5 6.9 2.8 61.5 0.24 0.42 6.9 plant decay
Kerrs Reach sediment 25-Mar 0.28 1.04 0.5 0.5 0.22 35.4 47.1 1.0 35.4 0.49 0.74 47.1 Wildfowl/plant
decay
Boatsheds sediment 8-Apr 0.58 0.68 1.3 1.6 0.37 56.3 24.3 1.3 56.3 0.56 0.57 24.3 Wildfowl/plant
decay
Kerrs Reach sediment 8-Apr 0.22 0.34 0.6 0.5 0.18 38.5 66.1 0.7 38.5 0.70 0.78 66.1 Wildfowl/plant
decay
*Shading indicates that the sample meets the criteria for that ratio, refer to Appendix 3, Table 11 for explanation of ratio abbreviations
**words in bold suggest the major contributor to pollution as determined by these assays, however, other faecal sources may be
present/dominate that were not targeted. #some evidence for mammalian faecal contamination
Avon River Post Earthquake – Follow on study June 2013
Table 7: Summary of collated Faecal Source Tracking results in Avon River water and sediments
Location Sample
type
Date
2013
E. coli
CFU/100mL
/g dry wtg.
Human PCR markers Non-human PCR
markers Sterols FWAs **Interpretation
BiAdo HumM3 BacH
Reischer Wildfowl Canine
Boatsheds water
11-Mar
1,055 ND ND Weak
Positive Positive ND wildfowl/plant decay NT Wildfowl, plant decay
Kerrs Reach water 5,000 ND ND ND Positive ND wildfowl/plant decay NT Wildfowl, plant decay
Owles
Terrace water 650 ND ND ND Positive ND wildfowl/plant decay NT wildfowl/plant decay
Boatsheds water
25-Mar
900 Positive ND Weak
Positive Positive ND Wildfowl/plant decay NT Human, wildfowl
Kerrs Reach water 1,070 Positive Weak
Positive
Weak
Positive Positive ND Wildfowl/plant decay <0.01
Fresh
human,,wildfowl,
plant decay
Owles
Terrace water 750
Weak
Positive ND ND Positive ND Wildfowl/plant decay NT
wildfowl,
plant decay
Boatsheds water
8-Apr
1,150 Positive ND Weak
Positive Positive ND *plant decay 0.03
Human, wildfowl,
plant decay
Kerrs Reach water 4,500 Positive ND Weak
Positive Positive ND Wildfowl/plant decay 0.03
Human, wildfowl,
plant decay
Owles
Terrace water 240
Weak
Positive ND ND ND ND
low level human,
plant decay NT
(aged?/ low level
human), plant decay
Kerrs Reach sediment 25-Mar 91,600
NT NT NT NT NT Wildfowl/plant decay NT Wildfowl/plant decay
Boatsheds sediment 8-Apr
220 NT NT NT NT NT Wildfowl/plant decay NT Wildfowl/plant decay
Kerrs Reach sediment 19,600 NT NT NT NT NT Wildfowl/plant decay NT Wildfowl/plant decay
Grey shading indicate samples requested by ECan for FST analysis ND = sample analysed and target not detected
*some evidence for weak signal from mammalian indicators NT = sample not analysed
**words in bold suggest the major contributor to pollution as determined by these assays, however, other faecal sources may be
present/dominate that were not targeted.
Avon River Post Earthquake – Follow on study June 2013
3.11. Faecal ageing tools for faecal source tracking
Figure 8 presents the faecal aging ratio of AC/TC plotted against the concentration of E.
coli detected in water at the three Avon River locations over the sampling period March
2011 - April 2013. This sampling regime represents 19 samples analysed at each site.
AC/TC values at the Boatsheds varied between 0.3-5.8 with an arithmetric mean of 1305
CFU/100 mL E. coli. Less variability in AC/TC was seen at Kerrs Reach with all values
<3.0 and a higher mean of 4470 CFU/100 mL E. coli. During discharge at Owles Terrace,
E. coli concentrations were approximately 10 fold higher (mean 30,000 E. coli/100 mL)
compared with post-discharge (mean 1200 E. coli/100 mL) and AC/TC ratios were all
below 0.92 during discharge at Owles Terrace. The two circles in Figure 8 depict during
and post-discharge values for the faecal aging ratio at Owles Terrace and show that post-
discharge, the aging ratio was above 1.2, which was statistically, significantly different to
the aging ratio during discharge (p = <0.001) but only at Owles Terrace. Concentrations of
E. coli during and after discharge were also significantly different at both Kerrs Reach (p =
0.014) and Owles Terrace (p = <0.001) but not the Boatsheds. The significant differences
between faecal aging ratios and E. coli at Owles Terrace, has been accompanied by a
decrease in the faecal sterol concentrations post-discharge.
Figure 8: Faecal aging ratio versus E. coli concentration in Avon River water (2011-2013)
AC/TC faecal aging ratio
0 1 2 3 4 5 6 16
E.
co
li C
FU
/100 m
L
101
102
103
104
105
106
Boatsheds
Kerrs Reach
Owles Terrace
Action level (550 E. coli CFU/100mL)
Alert level (260 E. coli CFU/100 mL)
Samples collected from Owles Terrace prior to discharges ceasing
Samples collected from Owles Terrace post-discharge
Avon River Post Earthquake – Follow on study June 2013
4. Discussion This study was undertaken a year after a comprehensive study of the Avon River water,
sediment, estuarine water and sediment, coastal water and sediment was undertaken. The
aim of this study was to assess the microbial loading of the Avon River water, sediment
and estuarine sediment to ensure accurate public health messages were disseminated.
Table 3 and Table 4 in the report detail the average concentrations of microorganisms
detected in the Avon River water, sediment and estuarine sediment over the course of the
entire study (April 2011-March 2013).
4.1. Microorganisms in river water
The average E. coli concentrations at the Boatsheds have decreased in our current study
compared with during and post Active Discharge. Faecal source tracking analyses at the
Boatsheds suggest wildfowl contamination is present during all sampling periods of the
current study and human faecal pollution was identified in the river water on the last two
sampling occasions. Identification of human contamination may be related to the increased
activity in the area such as dredging of the river bed, construction of new pipelines and
contamination issues adjacent to and upstream of the Boatsheds. These factors may also
contribute to the presence of wildfowl indicators which were identified in both sediment (8
April) and overlying water (all events) at the Boatsheds. Immediately post-quake no
known direct discharges were occurring upstream of the Boatsheds. Since then various
investigations undertaken by CCC have uncovered problems particularly relating to drains
feeding into the Avon (Riccarton Main Drain, Addington Main Drain). Prior to the
September 2010 earthquake, and subsequent sewage discharges, the water quality at the
Boatsheds frequently did not comply with Recreational Water Quality. The source of the
pollution was determined in an ESR Report 2009 (Moriarty et al) to be wildfowl and dog
faeces, with no human pollution detected in the study.
At Kerrs Reach a higher average concentration of E. coli per 100 ml (3,523 cfu) was
detected compared with the post-discharge average concentration of E. coli (1, 629 cfu).
FST analysis identified wildfowl markers in the water and sediment, and human markers
were present in the water on the last two sampling events. A number of overflow events
have occurred in the area in recent times and weed cutting had been undertaken. Several
new water and wastewater pipes have also been laid in the area. All of these activities
Avon River Post Earthquake – Follow on study June 2013
have the potential to add to the microbial loading in the river. As this is still an area where
significant recreational activity takes place, water users should be kept up to date on the
water quality and warning signs erected where appropriate.
Owles Terrace which received significant volumes of direct discharge post-quake has the
lowest concentration of E. coli per 100 ml in the water in this current study. The FST
analyses did not identify human markers in the water at Owles Terrace, except for a weak
signal on the last sampling occasion when strong human indicators were present at both
upstream sites. This site is also tidally impacted so would be expected to have the highest
input of non-sewage impacted sea water compared with other sites.
Water and sediment samples were analysed for bacteriophage. At all three sites
concentrations have decreased significantly to very low levels at or just above our limit of
detection (50 PFU per 100 ml). In our previous report we signalled that bacteriophage
show promise as indicators of Campylobacter presence. Results from this study are
inconclusive, and it will be a potential correlation we will continue to monitor in our
studies.
Campylobacter concentrations in the river water samples were similar throughout the study
at the Boatsheds, with the current study having the highest average concentration per
100 ml. At Kerrs Reach the concentration decreased following the cessation of discharges,
but has increased significantly again in the final sampling round. This may be due to a high
number of wildfowl in the area and continual sewage pipe repairs which may lead to
discharges to the river. Owles Terrace which had the highest average concentration of
campylobacters during discharge has remained relatively low since discharges ceased.
4.2. Microorganisms in Sediment
In terms of microorganisms present in riverbed and estuarine sediment, the most
significant finding was at Kerrs Reach. Here the sediments were 15 times more
contaminated with E. coli than during active discharges. This may be a build-up of E. coli
over time in the sediments due to known (and unknown) discharges to the river. The
Boatsheds had reduced on average by 47% since the post discharge study and Owles
Terrace by 77%. Levels in the two estuarine sediment sites are low and do not warrant any
concerns.
Avon River Post Earthquake – Follow on study June 2013
Bacteriophage at all but one site (Penguin St.) had no detectable phage present in the
current sampling round. Penguin St was the only site found to contain phage, and this was
at a low level. Campylobacter was only detected at one site (Kerrs Reach) in the current
study and had the highest average concentration when compared to the two previous
sampling timeframes. In our previous study we noted that Bacteriophage and
Campylobacter do not appear to accumulate in the Avon River sediments and both
microorganisms have short survival times after discharge to the river system. These
findings support this hypothesis and highlight that the Campylobacter would have been
recently deposited in the sediment.
Cryptosporidium was only detected at one sediment sampling site – Humphreys Drive.
The concentrations were very low and do not warrant any public health concern. Giardia
which had previously been very high (2,254 cysts per gram) at the Boatsheds was not
detected there on this current sampling round. It was however detected at a low level at
Kerrs Reach (0.8 per gram) and Penguin St (<0.2 per gram). The concentrations seen were
significantly lower than those recorded during discharges due to the lack of fresh inputs
and in the sampling period immediately after them. The decrease may also be related to
the dredging of the riverbed which may have removed sediment where the giardia were
concentrated.
Enterococci were analysed in the two estuarine samples (Humphreys Drive and Penguin
St) and found to have decreased significantly compared with results during active
discharges. Penguin St was higher than Humphreys Drive but there was also evidence of
significant vehicular traffic on the sands and demolition activity which may have added to
the microbial loadings of the sediments.
4.3. Faecal Aging
The river water was tested for the faecal aging ratio of AC/TC (Atypical colonies/ Total
Coliforms). This ratio compares normal microflora concentrations in the river with the
total coliform concentrations from faecal inputs. Lower ratios of AC/TC with high TC
concentrations, suggest more recent faecal inputs. According to Brion (2005), fresh inputs
to river systems are observed when the AC/TC ratio is 5 or less with fresh human sewage
reporting values of less than 1.0 as observed at Owles Terrace during continuous sewage
Avon River Post Earthquake – Follow on study June 2013
discharges (Figure 8). Influx from stormwater drains of aged human inputs increases the
ratio up to 5.0 making it difficult to distinguish from other animal/bird inputs. AC/TC
values derived from wildfowl faecal inputs have not been studied specifically, but
agricultural inputs to river systems have been reported as having AC/TC values of
approximately 10 (Nieman and Brion et al. 2003). The ratios of AC/TC were, in general,
below 6.0 throughout the study even during the 2013 sampling, except for one sample at
Owles Terrace on 25th
March, 2013 which was 15.8. The low AC/TC values suggest that
this river system is subjected to on-going inputs of faecal material, which from the FST
data is not exclusively human derived. In conclusion, at these three sites on the Avon
River, the AC/TC values and FST results suggest that the river has been continually
impacted by recent faecal inputs from human and non-human sources. AC/TC ratio values
of approximately 20 and above indicate a healthier water quality environment (Brion,
2005), which has a reduced risk to human health and is more suitable for recreational
activities.
5. Conclusion
The results of this follow up study on the Avon River water, sediment and estuarine
sediment highlight the on-going water quality issues. The Boatsheds at Antigua St
continues to have poor water quality similar to the levels measured throughout the active
discharges and post discharges. Historically, the water quality at the Boatsheds has been
poor and this continues to be the case. FST tools have indicated the likely sources of
pollution at the Boatsheds to be wildfowl, with intermittent human pollution. The water
quality at Kerrs Reach is also unsatisfactory in terms of public health risk with the average
E. coli concentration close to those seen during active sewage discharges. FST results
indicate fresh human inputs as well as wildfowl faeces at this site. Finally, Owles Terrace
has seen the greatest improvement in water quality post-discharge with the final sample
(240 E.coli per 100 ml) below alert level for the recreational water guidelines 260 E. coli
per 100 ml), and FST reporting the source of E. coli as wildfowl.
Post cessation of direct discharges to the Avon, the sediments of the river contained a
significant number of protozoa. The results from this study showed a marked decrease in
concentration, which indicates improvements for the long term quality of the water. At
Avon River Post Earthquake – Follow on study June 2013
Kerrs Reach the highest concentration of E. coli per g of sediment was detected. FST
determined the source as wildfowl. It should be noted that the 2nd
and 3rd
sampling of this
study, sediment and water samples were taken further downstream at Kerrs Reach than
previously sampled due to problems accessing the original sampling location. The two
estuarine sediment sites showed significant decrease in microorganisms tested compared
with previous sampling and do not warrant any public health concern based on the
organisms analysed in this study.
As the Avon River is used year round for recreational activity, users should be kept
updated with the water quality, particularly at the Boatsheds where a number of people
unfamiliar with the water quality of the Avon have recreational contact with it. Due to the
low levels of Giardia and Campylobacter spp. present in the sediment, care should always
be advised in relation to disturbance of the sediments, especially at Kerrs Reach, due to the
high concentration of E. coli.
Avon River Post Earthquake – Follow on study June 2013
6. References Brion, G.M., 2005. The AC/TC bacterial ratio: a tool for watershed quality management.
Journal of Water and Environment Technology 3(2), 271- 277.
Moriarty, E.M., and Gilpin, B.J., 2009. Faecal Tracking in the Avon River, Christchurch.
CSC Report Number FW09075.
Moriarty, E.M., Devane, M.L., Williamson, W., Gilpin, B.J., 2012. Microbial Quality of
the Avon River, the effect of major earthquakes and subsequent sewage discharges
on the quality of the water and sediments in the Avon River. Progress Report. CSC
Report Number FW11043.
Nieman, J. and Brion, G.M., 2003. Novel bacterial ratio for predicting faecal age. Water
Science and Technology 47(3), 45-49.
Ministry for the Environment 2003. Microbiological Water Quality Guidelines for Marine
and Freshwater Recreational Areas. New Zealand: 155
Avon River Post Earthquake – Follow on study June 2013
APPENDIX 1 : REPORT DISTRIBUTION
Copies have been made and distributed to:
Participating Councils
Environment Canterbury - Michele Stevenson
Environment Canterbury - Lesley Bolton-Ritchie
Christchurch City Council - Mike Bourke
ESR
Elaine Moriarty Meg Devane Louise Weaver
Brent Gilpin
CSC Library
Further copies of this report may be obtained from: Dr Elaine Moriarty
Christchurch Science Centre
P O Box 29-181
Christchurch
Avon River Post Earthquake – Follow on study June 2013
Appendix 2
PCR Assays
The specificity of the assays, as tested against known faecal samples is shown below (last
updated May 2013).
Semi-quantitative results are reported on a scale from Extremely Strong Positive down to
Very Weak Positive
Table 8: Specificity of PCR markers used in the Avon River study
Assay Present in faeces from: Low level non-
specificity
Negative in faeces
from:
General
GenBac
Human, Cat, Dog, Cow,
Sheep, Deer, Horse, Goat,
Pig, Rabbit, Possum, Duck,
Swan, Seagull, Canada
Goose Goose, Chicken
(can be low in seagull and
Canada Goose faeces)
Human BiADO Human Seagull Cat, Dog, Cow, Sheep,
Deer, Horse, Goat, Pig,
Rabbit, Possum, Duck,
Swan, Canada Goose,
Chicken
Human
HumM3
Human
Possum Rabbit Cat, Dog, Cow, Sheep,
Deer, Horse, Goat, Pig,
Duck, Swan, Canada
Goose, Chicken
Human BacH Human Cat, Dog, Rabbit,
Possum Chicken Goat Cow, Sheep, Deer, Horse,
Pig, Duck, Swan, Goose,
Canine DogBac Dog Some human
municipal sewage
Human, Cat, Cow, Sheep,
Deer, Horse, Goat, Pig,
Rabbit, Possum, Duck,
Swan, Seagull, Canada
Goose, Chicken
Bird GFD Duck, Swan, Seagull,
Canada Goose, Chicken Human, Cat, Dog, Cow,
Sheep, Deer, Horse, Goat,
Pig, Rabbit, Possum
E2 wildfowl
marker
Duck, Swan, Seagull,
Canada goose, Chicken Pig Human, Cat, Dog, Cow,
Sheep, Deer, Horse, Goat,
Rabbit, Possum
PCR Markers: Specificity testing of sources is an ongoing activity. The detection limit of
these methods is 1.00x103/100 mL.
Avon River Post Earthquake – Follow on study June 2013
Interpreting human indicative assays.
BacH is more sensitive than BiADO which is more sensitive than HumM3. The table below is
a guide to interpreting presence and absence of human indicative markers.
Table 9: Interpretation of the presence/absence of the three Human PCR markers Human
BiADO
Human
HumM3
Human
BacH Interpretation
+ + + Very strong evidence of (fresh)
human faecal contamination
+ ND +
Evidence of human faecal
contamination, but may be lower
levels, aged or partially treated
ND ND +
May be human, dog, cat, rabbit,
chicken. If canine marker absent
then can exclude dog. If wildfowl
marker absent then can exclude
chicken.
ND + +
Possible human, but if ruminant
marker present, may indicate
possum faeces.
+ ND ND
Possible human, but may indicate
aged source as it is hypothesised
that BiAdo may persist longer in the
environment than the other markers.
ND ND ND No evidence of human faecal
contamination. ND = sample was analysed, but the determinant was not detected.
The level of GenBac marker should also be considered when evaluating presence of the other
markers. For example when very high levels of GenBac, but very low levels of human
markers then suggest either other sources more dominant, or that if human markers are
present they are from aged or partially treated sources.
Avon River Post Earthquake – Follow on study June 2013
Appendix 3: faecal sterol analysis
Table 10: Raw Data for Faecal Sterols identified in Avon River water and sediments
Location Boatsheds Kerrs
Reach
Owles
Terrace Boatsheds
Kerrs
Reach
Owles
Terrace Boatsheds
Kerrs
Reach
Owles
Terrace
Kerrs
Reach Boatsheds
Kerrs
Reach
Date (2013) 11-Mar 11-Mar 11-Mar 25-Mar 25-Mar 25-Mar 8-Apr 8-Apr 8-Apr 25-Mar 8-Apr 8-Apr
Sample Type
(Volume/mass
analysed)
Water (4L) Water (3.5L) Water (4L) Water (4L) Water (4L) Water (2.2L) Water (4L) Water (4L) Water (4L) Sediment (1.1 g)
Sediment (1.1 g)
Sediment (1.1 g)
Sterol Name
coprostanol 822 63 103 282 146 57 302 185 165 29 63 25
24-
ethylcoprostanol 625 61 59 313 102 50 433 179 103 53 49 40
epicoprostanol 152 9 24 43 10 13 47 14 23 6 19 6
cholesterol 4877 1500 3018 2555 2212 3247 2204 1680 2012 1000 1894 1266
cholestanol 1514 253 277 311 211 140 280 668 138 102 109 113
24-
methylcholesterol 1233 458 535 793 353 277 578 396 270 666 286 784
24-
ethylepicoprostanol 72 5 13 23 1 9 24 6 7 1 8 9
stigmasterol 797 656 342 459 438 168 467 615 214 1065 182 419
24-ethylcholesterol 9628 1575 1081 3708 1199 570 2575 1578 706 2495 1191 2645
24-ethylcholestanol 1491 104 113 251 73 49 195 44 34 51 72 117
total sterols (ppt) 21211 4684 5565 8738 4745 4580 7105 5365 3672 5468 3873 5424
Avon River Post Earthquake – Follow on study June 2013
Table 11: Key for interpretation of sterol ratios
Ratios indicative of faecal pollution (either human or animal)
F1 coprostanol/cholestanol.. >0.5 indicative of faecal source of sterols
F2 24ethylcoprostanol/ 24-ethylcholestanol. >0.5 indicative of faecal source of sterols.
Human indicative ratios (values exceeding threshold in red)
H3 coprostanol/ 24-ethylcoprostanol Ratio >1 suggests human source
H1 % coprostanol Ratio >5-6% suggests human source
H2 coprostanol/(coprostanol+cholestanol) Ratio >0.7 suggests human source
H4 coprostanol/(coprostanol+24-ethylcoprostanol) Ratio >0.75 suggests human source
Ruminant indicative ratios (values exceeding threshold in blue)
R3 24-ethylcholesterol/24-ethylcoprostanol Ratio <1 suggests ruminant source, ratio >4 suggests plant decay
R1 % 24-ethylcoprostanol Ratio >5-6% suggests ruminant source
R2 coprostanol/(coprostanol+24-ethylcoprostanol) Ratio <30% suggests ruminant source
Avian indicative ratios (values exceeding threshold in orange)
A1 24-ethylcholestanol/(24-ethylcholestanol+24-
ethylcoprostanol+24-ethylepicoprostanol) A1 Ratio >30% suggests avian source AND A2 Ratio >67% suggests avian
source A2 cholestanol/(cholestanol+coprostanol+epicoprostanol)
Plant indicative ratios (values exceeding threshold in orange) P1 24-ethylcholesterol/24-ethylcoprostanol Ratio >4 suggests plant decay
Notes: Note that ratios must be interpreted with consideration to the levels of sterols, and relative to one another. For example H1 is typically also above 5-6% in ruminant faeces. Plant sterols and
mixed sources also have differing effects on sterol interpretations which must be considered.
Conclusions are the best interpretation of sterols in our opinion. Conclusions in bold are highly supported by the sterol data, conclusions in brackets are supported by sterol data with
some variation from pure source, and conclusions in brackets indicate likely source but with lower degree of certainty