investigation of selenium and arsenic in soil samples from a long-term field experiment béla...
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Investigation of selenium and arsenic in soil samples from a long-term field experiment
Béla Kovács, Éva Széles,József Prokisch, Zoltán Győri
University of Debrecen, Centre of Agricultural SciencesDepartment of Food Science and Quality Assurance
4032 Debrecen Böszörményi str. 138. Hungary
DebrecenBudapest
Nagyhörcsök
Pecs
We have to study the following goals in this research programme
The behaviour of arsenic and selenium in soil:
total concentration,
available concentration,
leaching,
transformation.
Worldwide variation in Se status(Combs, 2001)
0
50
100
150
200
250
300
350
plasma Seng/ml
country
USAUSAChinaChina (urban)(urban)
VenezuelaVenezuela
FinlandFinland
normal level
HungaryHungary
ChinaChina (Keshan dis. areas)(Keshan dis. areas)
CroatiaCroatia
The applied elements and doses in the long-term field experiment (Nagyhörcsök Experimental Station)
Rate (kg/ha) in spring of 1991 Elements
applied 1 2 3 4
Chemicals used
Al 0 90 270 810 AlCl3
As 30 90 270 810 As2O3/NaAsO2 Ba 0 90 270 810 BaCl2
Cd 30 90 270 810 CdSO4
Cr 0 90 270 810 K2CrO4
Cu 0 90 270 810 CuSO4
Hg 30 90 270 810 HgCl2
Mo 0 90 270 810 (NH4)6Mo7O24
Ni 0 90 270 810 NiSO4
Pb 0 90 270 810 Pb(NO3)2
Se 30 90 270 810 Na2SeO3 Sr 0 90 270 810 SrSO4
Zn 0 90 270 810 ZnSO4
Total element contents of soil samples depending on doses (sampling: 1994)
0
50
100
150
200
250
0 150 300 450 600 750
Dose in 1991 (kg/ha)
Co
nce
ntr
atio
n o
f ele
me
nts
(m
g/k
g)
As
Se
Lakanen-Erviö soluble element contents of soil samples depending on doses (sampling: 1994)
010
20304050
607080
90100
0 150 300 450 600 750
Dose in 1991 (kg/ha)
Con
cent
ratio
n of
ele
men
ts (
mg/
kg)
As
Se
Rate of Lakanen-Erviö soluble and total element contents of soil samples depending on doses (sampling: 1994)
0
10
20
30
40
50
60
0 150 300 450 600 750
Dose in 1991 (kg/ha)
Con
cent
ratio
n of
ele
men
ts (
mg/
kg)
As
Se
Concentration of arsenic depending on duration of field experiment and doses in soil samples
0
10
20
30
40
50
60
70
80
90
100
1991 1992 1994 1997 2000
Year of sampling
Co
nce
ntr
atio
n o
f ars
enic
(m
g/k
g)
30
90
270
810
Plot treated with arsenic (4. level)Plot treated with arsenic (4. level)Nagyhörcsök Experimental StationNagyhörcsök Experimental Station
barley (2000)barley (2000)
Concentration of selenium depending on duration of field experiment and doses in soil samples
0
20
40
60
80
100
120
140
1991 1992 1994 1997 2000
Year of sampling
Co
nce
ntr
atio
n o
f se
len
ium
(m
g/k
g)
30
90
270
810
Plots treated with selenium (4. and 3. levels)Plots treated with selenium (4. and 3. levels)
Nagyhörcsök Experimental StationNagyhörcsök Experimental Station
barleybarley (?!) (2000)(?!) (2000)
Selenium content of treated (the highest level) and control plots in different soil layers (2000)
0
2
4
6
8
10
12
14
16
18
20
0-30
30-60
60-90
100-130
130-160
160-190
200-230
230-260
260-290
soil layer (cm)
con
cen
trat
ion
of S
e (m
g/k
g)
treated plotcontrol plot
Analysis of selenium standards by IC-ICP-MS instrument100 ppb Se-Meth+100 ppb selenite+100 ppb selenate
Detection limits: 0.01 – 0.05 – 0.1 ppb
0
10000
20000
30000
40000
50000
60000
0 5 10 15 20 25 30
time [min]
ICP
-MS
sign
al [c
ps]
Se-methionine
selenite
selenate
(Se(IV), SeO32-)
(Se(VI), SeO42-)
COOH
CHNH2
CH2
CH2
Se CH3
0
10000
20000
30000
40000
0 5 10 15 20 25
Time (min)
ICP
-MS
sig
na
l (c
ps
)
1991 I/1
1991 I/2
1991 I/3
1991 I/4
selenate
selenite
organic selenium forms
Comparison of contents of selenium forms in 1991(I: 1. repetition, 1, 2, 3, 4 doses: 30, 90, 270 and 810 kg/ha)
Fate of selenite in soil (1:10 water extract)Heavy metal load field experiment: Dr. Imre Kádár, Nagyhörcsök
0
100000
200000
300000
400000
500000
600000
700000
800000
900000
1000000
0 10 20duration [min]
ICP
-MS
sig
nal [
CP
S]
0
5000
10000
15000
20000
25000
0 10 20duration [min]
ICP
-MS
sig
nal [
CP
S]
0
5000
10000
15000
20000
25000
0 10 20duration [min]
ICP
-MS
sig
nal [
CP
S]
1993 1993 2003
oxidationselenite
selenate
organic selenium
Conclusion: selenite will be oxidised in soil to selenate selenate more available for plants (it is analogous to sulphate) risk of leaching
selenite
selenate
0
20000
40000
60000
80000
100000
120000
0 5 10 15 20
duration (min)
ICP
-MS
sig
nal
(cp
s)
0-30 cm
30-60 cm
60-90 cm100-130 cm
130-160 cm
160-190 cm
200-230 cm230-260 cm
Comparison of contents of selenium forms in 2000 from different layers
selenite
selenate
organic selenium forms
AcknowledgementsAcknowledgements
• Dr. Imre Kádár (RISSAC)• Hungarian Scientific Research
Fund (OTKA T38450)• István Széchenyi Scholarship
Thank you for your attention!Thank you for your attention!
AsAs
Se As
Se
Separation of selenium ions by High Performance Liquid Chromatography – Inductively Coupled Plasma Mass
Spectrometer hyphenated system (HPLC-ICP/MS)
High Performance Liquid Chromatography (HPLC) column: IC-AN1 anion exchanger
Inductively Coupled Plasma Mass Spectrometer (ICP-MS)
Eluent: Phtalic-acid-Tris buffer
Other information Different levels of the selected metal salts (13) were added
to plots once at starting year (1991) and were mixed into the ploughed layer (0-20 cm)
The treatments were arranged in a split-plot design with replications (2)
These experimental plots are cultivated with commonly used agrotechnics, chemical fertilizers are added yearly to ensure sufficient macronutrient (NPK) supply
Composite soil samples consisting of 20 subsamples are collected yearly from the ploughed layer of each plot
To check the vertical movement of these pollutants, samples are also taken from the subsoil of plots with the highest level of added metal salts in some years (1993, 1996, 2000)
Type of soil in the experiment : calcareous loamy chernozem
Plot treated with cadmium (4. level)Plot treated with cadmium (4. level)Nagyhörcsök Experimental StationNagyhörcsök Experimental Station
Plot treated with lead (4. level)Plot treated with lead (4. level)
Nagyhörcsök Experimental StationNagyhörcsök Experimental Station
Plots treated with molybdenum (1. and 4. levels)Plots treated with molybdenum (1. and 4. levels)Nagyhörcsök Experimental StationNagyhörcsök Experimental Station
Nagyhörcsök Experimental Stationplant and soil samples
- The experiment includes: 4 levels in duplicate, i.e. 8 plots, each with a size of 21 m2.- Experimental plants: maize (1991), carrot (1992), potato (1993), peas (1994), red beet (1995), spinach (1996), wheat (1997), sunflower (1998), sorrel (1999), barley (2000), rape (2001), poppy (2002), wheat (2003), alfalfa (2004), alfalfa (2005)
- Soil sampling and analyses on soil samples: 1991: 0-20 cm soil layer of the plots, 1993: "mobile" fraction in the 0-20, 20-40, 40-60 cm soil layers from plots with the highest level of added metal salts, 1996: "mobile" and "total" fractions in the 0-30, 30-60, 60-90 cm soil layers from plots with the highest level of added metal salts. 2000: As: 0-20, 20-40, 40-60, 60-90 cm soil layers from plots with the highest level of added metal salts, Se: 0-30, 30-60, 60-90, 100-130, 130-160, 160-190, 200-230, 230-260, 260-290 cm from plots with the highest level of added metal salts.
Results considering plant analysesResults considering plant analyses1.Owing to the highest level of arsenic treatment, the quantity of crop of each
applied plant decreased in each year. However arsenic content was not increased in different parts of plants, it was about 1-2 mg/kg concentration range. Arsenic is not mobile in the soil-plant system. From the applied plants, peas and spinach were the most sensitive affected by arsenic. Presumably the applied arsenite (As(III)) is transformed to arsenate (As(V)) which is the more toxic species.2. The destroying effect of Se does not decrease with years, and what is more
the effect of Se increases. Presumably the applied Na-selenite form is transformed to the more toxic Ca-selenate, it is oxidized among those soil conditions. We have to determine the concentration of different selenium species (selenite and selenate) in soil samples during our research. Similarly to Mo, Se is extremely mobile, the plant parts contain many hundreds mg/kg of selenium accompanied toxic symptoms. High applied concentration of selenium destroys even weed-plants recently also.
The arsenic and selenium caused decrease of yield of different plants owing to the fitotoxic effect between 1991-1997: - maize seed: As and Se - red beet root: Se - carrot root: As and Se - spinach leaf: As and Se - potato tuber: As and Se - wheat seed: As and Se - peas seed: As and Se