alkalinit y (mg/ l) - costa rica research experience for ... · health risks in the highlands of...
TRANSCRIPT
HYDRO-GEOCHEMICAL PROCESSES DRIVING ARSENIC CONCENTRATIONS
IN SPRINGS IN THE THE HIGHLANDS OF COSTA RICA
Glen V. C. Aguilar[1], Daniel Riddle[2], Melissa Zapata[3], Kaya Weatherby[4], Peter S. K.
Knappett[3], Kelly Brumbelow[3], Georgianne Moore[3]
University of Guam[1]; Utah Valley University[2]; Texas A&M University[3]; Boston University[4]
Acknowledgements:Funding for this Research Experiences for Undergraduate program is provided by the National Science Foundation’s Division of
Earth Sciences (EAR-1659848).
References:Knappet, Peter, et. al, 2019. “Processes Driving Rising Arsenic Concentrations in an Intensively Pumped Agricultural Basin in
Central Mexico”.
Kibet, J., et. Al, 2016. “The Geochemical Speciation of Hand-dug Well Water of Kakamega County, Kenya”.
• The objectives of this study are to:
1. assess levels of arsenic (As) and fluoride (F)
in drinking water springs as potential human
health risks in the highlands of Costa Rica;
2. investigate the hydro-geochemical processes
driving observed concentrations across this
region.
We hypothesize that in geothermally active areas,
a gradation of springs exist from purely fresh,
meteoric recharge water with low Total Dissolved
Solids (TDS) to geothermal spring water with high
TDS.
Field Analysis
• Locate springs and map coordinates (Garmin
eTrex 30)
• Test water for temperature, pH, specific
conductance, and ORP (YSI 1030 Pro)
• Test water for alkalinity (HACH Model AL-DT)
• Filter and bottle samples for laboratory analysis
• Samples were then stored at 4°C prior to lab
analysis. • Data supports hypothesis that there is a gradient
between freshwater and geothermal water
• Nitrite and nitrate may not adhere to the gradient due to
them not being part of the biosphere
• We will not yet fully understand hydro-geochemical
processes of the system until water isotopes results are
completed
• Further studies and analysis may explain why certain
parameters decrease and specific conductance and
temperature increase
Figure 1: Sample sites in Costa Rica
METHODOLOGY
INTRODUCTION
%𝐶𝐵𝐸 =Σ 𝑐𝑎𝑡𝑖𝑜𝑛𝑠 −Σ |𝑎𝑛𝑖𝑜𝑛𝑠|
Σ 𝑐𝑎𝑡𝑖𝑜𝑛𝑠+Σ |𝑎𝑛𝑖𝑜𝑛𝑠|∗ 100
RESULTS
Lab Analysis
• Anions and cations were analyzed using ion
chromatography (Dionex 500, Thermo-Fischer
Scientific, Waltham, MA).
• Water isotopes δ18O and δ2H were analyzed on
a Picarro cavity ring down system (Picarro Inc.,
Santa Clara, CA).
• Trace elements were analyzed using Inductively
Coupled Plasma Mass Spectroscopy (ICP-MS)
Figure 4: Piper plot showing major ion proportions in
samples.
Equation 1: Charge Balance Error helps us judge the
validity of water analyses. Ideally CBE is ±5%
• Water chemistry of geothermal springs mostly
consist of sodium chloride
• Treated river water and freshwater springs mostly
consist of magnesium bicarbonate
• Box and whisker plots show there is a gradient in
most of the chemical parameters
• Our bivariate plots show that as specific
conductance increase, many chemical parameters
seem to decrease
DISCUSSION CONCLUSION AND FUTURE RESEARCH
Figure 2: The graphs above show the gradient in field measurements and TDS between the different water types
Figure 3: The graphs above show the relationship between the highest correlating parameters
1
10
100
1000
1 10 100 1000 10000Alk
alin
ity (
mg
/L)
Specific Conductance (𝜇S/cm)
CA
TIO
NS
AN
ION
S
1
10
100
1 10 100 1000 10000
Cal
ciu
m (
mg
/L)
Specific Conductance (µS/cm)
1
10
100
1000
1 10 100 1000 10000
Sod
ium
(m
g/L
)
Specific Conductance (µS/cm)
1
10
100
1 10 100 1000
Cal
ciu
m (
mg
/L)
Alkalinity (mg/L)
0.0001
0.001
0.01
0.1
1
10
1 10 100 1000 10000
Lith
ium
(m
g/L
)
Specific Conductance (µS/cm)
RESULTS
Flu
ori
de
(m
g/L)
00.05
0.10.15
0.20.25
0.30.35
0.40.45
0.5
Ch
lori
de
(mg/
L)0
100
200
300
400
500
600
700
Nit
rite
(m
g/L)
00.20.40.60.8
11.21.41.61.8
2
Sulf
ate
(mg/
L)
020406080
100120140160180200
Bro
mid
e (
mg/
L)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
Nit
rate
(m
g/L)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
Ph
osp
hat
e (
mg/
L)
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Lith
ium
(m
g/L)
0
0.5
1
1.5
2
2.5
Sod
ium
(m
g/L)
0
100
200
300
400
500
600
700
800
Am
mo
niu
m (
mg/
L)
0
2
4
6
8
10
12
14
16
Po
tass
ium
(m
g/L)
0
10
20
30
40
50
60
70
Spec
ific
C
on
du
ctan
ce
(µS/
cm)
0
500
1000
1500
2000
2500
3000
3500
Mag
nes
ium
(m
g/L)
0
10
20
30
40
50
60
70
Cal
ciu
m (
mg/
L)
515
25
35
45
55
6575
85
95
Alk
alin
ity
(mg/
L)
30
50
70
90
110
130
150
170
190
OR
P (
mV
)
100150200250300350400450500550600
pH
0
12
3
4
5
6
7
8
9
Figure 5: Sample sites and field sampling in Costa Rica