Elisabeth Eiche - Academia.edu (original) (raw)

Papers by Elisabeth Eiche

Environmental Science and Pollution Research, 2014

Several regions around the globe are known to have soils highly enriched in Se. Usually, bulk sam... more Several regions around the globe are known to have soils highly enriched in Se. Usually, bulk samples are analysed when characterizing enrichment and mobility of Se in seleniferous soils. In this study, Se concentration and distribution were determined along with other elements on a microscale level in seleniferous soils from Punjab, India, using synchrotron-based X-ray fluorescence (XRF) analysis. Additionally, the mineralogical and geochemical composition of bulk soil material was investigated. Sequential extractions were carried out to gain further insight into preferential Se associations. The objective of this study was to investigate the microscale geochemistry of seleniferous soils in order to be able to deduce information about Se host phases, to characterize the distribution, extent and origin of Se enrichment and to possibly reveal the relevant enrichment processes. Selenium concentrations in the soils vary considerably within tens of micrometers. Thirty times the bulk concentration, the highest Se enrichment was found to be 350 mg/kg. Results show that the primary origin of Se in these soils is probably not from weathering of bedrock or alluvium but rather from an external Se source, like Se-rich irrigation water. Secondary processes like in situ formation of mineral phases, adsorption or transformation to organic species finally lead to an immobilization and fixation of Se in the soils. In this context, reduction of Se oxyanions to elemental Se or to selenide as part of sulfides probably leads to the highest Se enrichment which, however, is mainly spatially confined. Lower Se enrichments are indicated to be due to (co-)precipitation with or adsorption to calcite. Therefore, this extremely heterogeneous distribution of Se must be controlled by small-scale differences in redox and solution chemistry which can develop in small soil structure like micropores or soil aggregates.

The spatial variability of As concentrations in aquifers of the Red River Delta, Vietnam, was stu... more The spatial variability of As concentrations in aquifers of the Red River Delta, Vietnam, was studied in the vicinity of Hanoi. Two sites, only 700 m apart but with very different As concentrations in groundwater (site L: <10 lg/L vs. site H: 170-600 lg/L) in the 20-50 m depth range, were characterized with respect to sediment geochemistry and mineralogy as well as hydrochemistry. Sequential extractions of the sediment were carried out in order to understand why As is released to groundwater at one site and not the other. No major differences were observed in the bulk mineralogy and geochemistry of the sediment, with the exception of the redox state of Fe oxyhydroxides inferred from sediment colour and diffuse spectral reflectance. At site H most of the As in the sediment was adsorbed to grey sands of mixed Fe(II/III) valence whereas at site L As was more strongly bound to orange-brown Fe(III) oxides. Higher dissolved Fe and low dissolved S concentrations in groundwater at site H ($14 mg Fe/L, <0.3 mg S/L) suggest more strongly reducing conditions compared to site L (1-2 mg Fe/L, <3.8 mg S/L). High concentrations of NH þ 4 ($10 mg/L), HCO À 3 (500 mg/L) and dissolved P (600 mg/L), in addition to elevated As at site H are consistent with a release coupled to microbially induced reductive dissolution of Fe oxyhydroxides. Other processes such as precipitation of siderite and vivianite, which are strongly supersaturated at site H, or the formation of amorphous Fe(II)/As(III) phases and Fe sulfides, may also influence the partitioning of As between groundwater and aquifer sands.

Applied Geochemistry, 2000

High concentrations of geogenic As in the groundwaters of south and SE Asia, which are used as dr... more High concentrations of geogenic As in the groundwaters of south and SE Asia, which are used as drinking waters, are causing severe health impacts to the exposed human populations. It is widely accepted that As mobilisation from sediments into these shallow reducing groundwaters requires active metal-reducing microbes and electron donors such as organic matter (OM). Although OM in such Holocene aquifers has been characterised, there is a dearth of data on Pleistocene aquifers from the same areas. Reported here are preliminary studies of OM and microbial communities present in two aquifers, one of Pleistocene and one of Holocene age, with contrasting concentrations of As (viz. Pleistocene: low As <10 μg/L; Holocene: high As up to 600 μg/L) from Van Phuc village in the Red River Delta, Vietnam. Results revealed OM inputs from multiple sources, including potential contributions from naturally occurring petroleum seeping into the shallow aquifer sediments from deeper thermally mature source rocks. Although concentrations vary, no noticeable systematic differences in biomarker distribution patterns within the OM were observed between the two sites. Microbial analyses did not show a presence of microbial communities previously associated with As mobilisation. All clone libraries were dominated by α-, β-, and γ-Proteobacteria not known to be able to reduce Fe(III) or sorbed As(V). Furthermore, representatives of the Fe(III)-reducing genus Geobacter could only be detected at very low abundance by PCR, using highly selective 16S rRNA gene primers, supporting the hypothesis that metal reduction is not a dominant in situ process in these sediments. No correlation between As concentration in groundwater and OM composition nor microbial community in the host sediments was found. This suggests that either (i) As is not being significantly mobilised in situ in these sediments, instead As appears to be mobilised elsewhere and transported by groundwater flow to the sites or (ii) sorption/desorption processes, as implicated by geochemical data from the cores, play a critical role in controlling As concentrations at these sites.► First lipid analysis of Pleistocene aquifer sediments from a groundwater As-prone region. ► No difference in lipids between (As-rich) Holocene and (As-poor) Pleistocene aquifers. ► Lack of in situ microbially mediated As mobilisation in any of the sediments. ► Groundwater As at depth controlled by As mobilisation processes elsewhere.

Journal of Hazardous Materials, 2011

Soil and groundwater samples were collected for bulk elemental analyses in particular for seleniu... more Soil and groundwater samples were collected for bulk elemental analyses in particular for selenium (Se) concentrations from six agricultural sites located in states of Punjab and Haryana in North-West India. Toxic concentrations of Se (45-341 g L −1 ) were present in groundwater (76 m deep) of Jainpur and Barwa villages in Punjab. Selenium enrichments were also found in top soil layers (0-15 cm) of Jainpur (2.3-11.6 mg kg −1 ) and Barwa (3.1 mg kg −1 ). Mineralogical analyses confirmed silicates and phyllosilicates as main components of these soils, also reflected by the high content of SiO 2 (40-62 wt.%), Al 2 O 3 (9-21 wt.%) and K 2 O (2.2-3.2 wt.%). Prevailing intensive irrigation practices in Punjab with Se enriched groundwater may be the cause of Se accumulation in soils. Sequential extraction revealed >50% Se bioavailability in Jainpur soils. Appearance of selenite was observed in some of the batch assays with soil slurries under reducing conditions. Although safe Se concentrations were found in Hisar, Haryana, yet high levels of As, Mo and U present in groundwater indicated its unsuitability for drinking purposes. Detailed biogeochemical studies of Se in sediments or groundwater of Punjab are not available so far; intensive investigations should be started for better understanding of the problem of Se toxicity.

Systematic investigations on seasonal variations in arsenic (As) concentrations in groundwater in... more Systematic investigations on seasonal variations in arsenic (As) concentrations in groundwater in both space and time are scarce for most parts of West Bengal (India). Hence, this study has been undertaken to investigate the extent of As pollution and its temporal variability in parts of Murshidabad district (West Bengal, India). Water samples from 35 wells were collected during premonsoon, monsoon and post-monsoon seasons and analyzed for various elements. Based on the Indian permissible limit for As (50 lg/L) in the drinking water, water samples were classified into contaminated and uncontaminated category. 18 wells were reported as uncontaminated (on average 12 lg/L As) and 12 wells were found contaminated (129 lg/L As) throughout the year, while 5 wells could be classified as either contaminated or uncontaminated depending on when they were sampled. Although the number of wells that alternate between the contaminated and uncontaminated classification is relatively small (14%), distinct seasonal variation in As concentrations occur in all wells. This suggests that investigations conducted within the study area for the purpose of assessing the health risk posed by As in groundwater should not rely on a single round of water samples. In comparison to other areas, As is mainly released to the groundwater due to reductive dissolution of Fe-oxyhydroxides, a process, which is probably enhanced by anthropogenic input of organic carbon. The seasonal variation in As concentrations appear to be caused mainly by dilution effects during monsoon and post-monsoon. The relatively high concentrations of Mn (mean 0.9 mg/L), well above the WHO limit (0.4 mg/L), also cause great concern and necessitate further investigations.

Water research, Nov 30, 2010

A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w... more A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / w a t r e s w a t e r r e s e a r c h 4 4 ( 2 0 1 0 ) 5 5 4 5 e5 5 5 5 0043-1354/$ e see front matter ª

Applied Geochemistry, Nov 30, 2008

The spatial variability of As concentrations in aquifers of the Red River Delta, Vietnam, was stu... more The spatial variability of As concentrations in aquifers of the Red River Delta, Vietnam, was studied in the vicinity of Hanoi. Two sites, only 700 m apart but with very different As concentrations in groundwater (site L: <10 lg/L vs. site H: 170-600 lg/L) in the 20-50 m depth range, were characterized with respect to sediment geochemistry and mineralogy as well as hydrochemistry. Sequential extractions of the sediment were carried out in order to understand why As is released to groundwater at one site and not the other. No major differences were observed in the bulk mineralogy and geochemistry of the sediment, with the exception of the redox state of Fe oxyhydroxides inferred from sediment colour and diffuse spectral reflectance. At site H most of the As in the sediment was adsorbed to grey sands of mixed Fe(II/III) valence whereas at site L As was more strongly bound to orange-brown Fe(III) oxides. Higher dissolved Fe and low dissolved S concentrations in groundwater at site H ($14 mg Fe/L, <0.3 mg S/L) suggest more strongly reducing conditions compared to site L (1-2 mg Fe/L, <3.8 mg S/L). High concentrations of NH þ 4 ($10 mg/L), HCO À 3 (500 mg/L) and dissolved P (600 mg/L), in addition to elevated As at site H are consistent with a release coupled to microbially induced reductive dissolution of Fe oxyhydroxides. Other processes such as precipitation of siderite and vivianite, which are strongly supersaturated at site H, or the formation of amorphous Fe(II)/As(III) phases and Fe sulfides, may also influence the partitioning of As between groundwater and aquifer sands.

Abstract The concentration, distribution, and speciation of selenium in different parts of wheat ... more Abstract
The concentration, distribution, and speciation of selenium in different parts of wheat and Indian
mustard, grown in a seleniferous area in Punjab, were investigated using synchrotron based (XAS)
and classical acid digestion and extraction methods.
The analyses revealed a high Se enrichment in all investigated plant parts, with Se levels in the
range of 133-931 mg/kg (dry weight, dw). Such high Se enrichment is mainly due to the considerable
amounts of easily available Se detected in the soil, which are renewed on a yearly basis to some
extent via irrigation. Speciation analysis in soil and plants indicated selenate and organic Se as major
Se species taken up by plants, with a minor presence of selenite. The analyses also revealed that the
highest Se enrichment occurs in the upper plant parts, in agreement with the high uptake rate and
mobility of selenate within plants. In both wheat and mustard, highest Se enrichments were found in
leaves (387 mg/kg×dw in wheat and 931 mg/kg×dw in mustard). Organic species (dimethylselenide
and methylselenocysteine) were found in different parts of both plants, indicating that an active
detoxification response to the high Se uptake is taking place through methylation and/or
volatilization. The high proportion of selenate in wheat and mustard leaves (47% and 70%,
respectively) is the result of the inability of the plant metabolism to completely transform selenate to
non-toxic organic forms, if oversupplied. Methylselenocysteine, a common Se species in
2
accumulating plants, was detected in wheat, suggesting that, in presence of high Se concentration,
this plant develops similar response mechanisms to accumulator plants.
Keywords
Selenium, speciation, wheat, Indian Mustard, synchrotron, XANES

Environmental Science and Pollution Research, 2014

Several regions around the globe are known to have soils highly enriched in Se. Usually, bulk sam... more Several regions around the globe are known to have soils highly enriched in Se. Usually, bulk samples are analysed when characterizing enrichment and mobility of Se in seleniferous soils. In this study, Se concentration and distribution were determined along with other elements on a microscale level in seleniferous soils from Punjab, India, using synchrotron-based X-ray fluorescence (XRF) analysis. Additionally, the mineralogical and geochemical composition of bulk soil material was investigated. Sequential extractions were carried out to gain further insight into preferential Se associations. The objective of this study was to investigate the microscale geochemistry of seleniferous soils in order to be able to deduce information about Se host phases, to characterize the distribution, extent and origin of Se enrichment and to possibly reveal the relevant enrichment processes. Selenium concentrations in the soils vary considerably within tens of micrometers. Thirty times the bulk concentration, the highest Se enrichment was found to be 350 mg/kg. Results show that the primary origin of Se in these soils is probably not from weathering of bedrock or alluvium but rather from an external Se source, like Se-rich irrigation water. Secondary processes like in situ formation of mineral phases, adsorption or transformation to organic species finally lead to an immobilization and fixation of Se in the soils. In this context, reduction of Se oxyanions to elemental Se or to selenide as part of sulfides probably leads to the highest Se enrichment which, however, is mainly spatially confined. Lower Se enrichments are indicated to be due to (co-)precipitation with or adsorption to calcite. Therefore, this extremely heterogeneous distribution of Se must be controlled by small-scale differences in redox and solution chemistry which can develop in small soil structure like micropores or soil aggregates.

The spatial variability of As concentrations in aquifers of the Red River Delta, Vietnam, was stu... more The spatial variability of As concentrations in aquifers of the Red River Delta, Vietnam, was studied in the vicinity of Hanoi. Two sites, only 700 m apart but with very different As concentrations in groundwater (site L: <10 lg/L vs. site H: 170-600 lg/L) in the 20-50 m depth range, were characterized with respect to sediment geochemistry and mineralogy as well as hydrochemistry. Sequential extractions of the sediment were carried out in order to understand why As is released to groundwater at one site and not the other. No major differences were observed in the bulk mineralogy and geochemistry of the sediment, with the exception of the redox state of Fe oxyhydroxides inferred from sediment colour and diffuse spectral reflectance. At site H most of the As in the sediment was adsorbed to grey sands of mixed Fe(II/III) valence whereas at site L As was more strongly bound to orange-brown Fe(III) oxides. Higher dissolved Fe and low dissolved S concentrations in groundwater at site H ($14 mg Fe/L, <0.3 mg S/L) suggest more strongly reducing conditions compared to site L (1-2 mg Fe/L, <3.8 mg S/L). High concentrations of NH þ 4 ($10 mg/L), HCO À 3 (500 mg/L) and dissolved P (600 mg/L), in addition to elevated As at site H are consistent with a release coupled to microbially induced reductive dissolution of Fe oxyhydroxides. Other processes such as precipitation of siderite and vivianite, which are strongly supersaturated at site H, or the formation of amorphous Fe(II)/As(III) phases and Fe sulfides, may also influence the partitioning of As between groundwater and aquifer sands.

Applied Geochemistry, 2000

High concentrations of geogenic As in the groundwaters of south and SE Asia, which are used as dr... more High concentrations of geogenic As in the groundwaters of south and SE Asia, which are used as drinking waters, are causing severe health impacts to the exposed human populations. It is widely accepted that As mobilisation from sediments into these shallow reducing groundwaters requires active metal-reducing microbes and electron donors such as organic matter (OM). Although OM in such Holocene aquifers has been characterised, there is a dearth of data on Pleistocene aquifers from the same areas. Reported here are preliminary studies of OM and microbial communities present in two aquifers, one of Pleistocene and one of Holocene age, with contrasting concentrations of As (viz. Pleistocene: low As <10 μg/L; Holocene: high As up to 600 μg/L) from Van Phuc village in the Red River Delta, Vietnam. Results revealed OM inputs from multiple sources, including potential contributions from naturally occurring petroleum seeping into the shallow aquifer sediments from deeper thermally mature source rocks. Although concentrations vary, no noticeable systematic differences in biomarker distribution patterns within the OM were observed between the two sites. Microbial analyses did not show a presence of microbial communities previously associated with As mobilisation. All clone libraries were dominated by α-, β-, and γ-Proteobacteria not known to be able to reduce Fe(III) or sorbed As(V). Furthermore, representatives of the Fe(III)-reducing genus Geobacter could only be detected at very low abundance by PCR, using highly selective 16S rRNA gene primers, supporting the hypothesis that metal reduction is not a dominant in situ process in these sediments. No correlation between As concentration in groundwater and OM composition nor microbial community in the host sediments was found. This suggests that either (i) As is not being significantly mobilised in situ in these sediments, instead As appears to be mobilised elsewhere and transported by groundwater flow to the sites or (ii) sorption/desorption processes, as implicated by geochemical data from the cores, play a critical role in controlling As concentrations at these sites.► First lipid analysis of Pleistocene aquifer sediments from a groundwater As-prone region. ► No difference in lipids between (As-rich) Holocene and (As-poor) Pleistocene aquifers. ► Lack of in situ microbially mediated As mobilisation in any of the sediments. ► Groundwater As at depth controlled by As mobilisation processes elsewhere.

Journal of Hazardous Materials, 2011

Soil and groundwater samples were collected for bulk elemental analyses in particular for seleniu... more Soil and groundwater samples were collected for bulk elemental analyses in particular for selenium (Se) concentrations from six agricultural sites located in states of Punjab and Haryana in North-West India. Toxic concentrations of Se (45-341 g L −1 ) were present in groundwater (76 m deep) of Jainpur and Barwa villages in Punjab. Selenium enrichments were also found in top soil layers (0-15 cm) of Jainpur (2.3-11.6 mg kg −1 ) and Barwa (3.1 mg kg −1 ). Mineralogical analyses confirmed silicates and phyllosilicates as main components of these soils, also reflected by the high content of SiO 2 (40-62 wt.%), Al 2 O 3 (9-21 wt.%) and K 2 O (2.2-3.2 wt.%). Prevailing intensive irrigation practices in Punjab with Se enriched groundwater may be the cause of Se accumulation in soils. Sequential extraction revealed >50% Se bioavailability in Jainpur soils. Appearance of selenite was observed in some of the batch assays with soil slurries under reducing conditions. Although safe Se concentrations were found in Hisar, Haryana, yet high levels of As, Mo and U present in groundwater indicated its unsuitability for drinking purposes. Detailed biogeochemical studies of Se in sediments or groundwater of Punjab are not available so far; intensive investigations should be started for better understanding of the problem of Se toxicity.

Systematic investigations on seasonal variations in arsenic (As) concentrations in groundwater in... more Systematic investigations on seasonal variations in arsenic (As) concentrations in groundwater in both space and time are scarce for most parts of West Bengal (India). Hence, this study has been undertaken to investigate the extent of As pollution and its temporal variability in parts of Murshidabad district (West Bengal, India). Water samples from 35 wells were collected during premonsoon, monsoon and post-monsoon seasons and analyzed for various elements. Based on the Indian permissible limit for As (50 lg/L) in the drinking water, water samples were classified into contaminated and uncontaminated category. 18 wells were reported as uncontaminated (on average 12 lg/L As) and 12 wells were found contaminated (129 lg/L As) throughout the year, while 5 wells could be classified as either contaminated or uncontaminated depending on when they were sampled. Although the number of wells that alternate between the contaminated and uncontaminated classification is relatively small (14%), distinct seasonal variation in As concentrations occur in all wells. This suggests that investigations conducted within the study area for the purpose of assessing the health risk posed by As in groundwater should not rely on a single round of water samples. In comparison to other areas, As is mainly released to the groundwater due to reductive dissolution of Fe-oxyhydroxides, a process, which is probably enhanced by anthropogenic input of organic carbon. The seasonal variation in As concentrations appear to be caused mainly by dilution effects during monsoon and post-monsoon. The relatively high concentrations of Mn (mean 0.9 mg/L), well above the WHO limit (0.4 mg/L), also cause great concern and necessitate further investigations.

Water research, Nov 30, 2010

A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w... more A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / w a t r e s w a t e r r e s e a r c h 4 4 ( 2 0 1 0 ) 5 5 4 5 e5 5 5 5 0043-1354/$ e see front matter ª

Applied Geochemistry, Nov 30, 2008

The spatial variability of As concentrations in aquifers of the Red River Delta, Vietnam, was stu... more The spatial variability of As concentrations in aquifers of the Red River Delta, Vietnam, was studied in the vicinity of Hanoi. Two sites, only 700 m apart but with very different As concentrations in groundwater (site L: <10 lg/L vs. site H: 170-600 lg/L) in the 20-50 m depth range, were characterized with respect to sediment geochemistry and mineralogy as well as hydrochemistry. Sequential extractions of the sediment were carried out in order to understand why As is released to groundwater at one site and not the other. No major differences were observed in the bulk mineralogy and geochemistry of the sediment, with the exception of the redox state of Fe oxyhydroxides inferred from sediment colour and diffuse spectral reflectance. At site H most of the As in the sediment was adsorbed to grey sands of mixed Fe(II/III) valence whereas at site L As was more strongly bound to orange-brown Fe(III) oxides. Higher dissolved Fe and low dissolved S concentrations in groundwater at site H ($14 mg Fe/L, <0.3 mg S/L) suggest more strongly reducing conditions compared to site L (1-2 mg Fe/L, <3.8 mg S/L). High concentrations of NH þ 4 ($10 mg/L), HCO À 3 (500 mg/L) and dissolved P (600 mg/L), in addition to elevated As at site H are consistent with a release coupled to microbially induced reductive dissolution of Fe oxyhydroxides. Other processes such as precipitation of siderite and vivianite, which are strongly supersaturated at site H, or the formation of amorphous Fe(II)/As(III) phases and Fe sulfides, may also influence the partitioning of As between groundwater and aquifer sands.

Abstract The concentration, distribution, and speciation of selenium in different parts of wheat ... more Abstract
The concentration, distribution, and speciation of selenium in different parts of wheat and Indian
mustard, grown in a seleniferous area in Punjab, were investigated using synchrotron based (XAS)
and classical acid digestion and extraction methods.
The analyses revealed a high Se enrichment in all investigated plant parts, with Se levels in the
range of 133-931 mg/kg (dry weight, dw). Such high Se enrichment is mainly due to the considerable
amounts of easily available Se detected in the soil, which are renewed on a yearly basis to some
extent via irrigation. Speciation analysis in soil and plants indicated selenate and organic Se as major
Se species taken up by plants, with a minor presence of selenite. The analyses also revealed that the
highest Se enrichment occurs in the upper plant parts, in agreement with the high uptake rate and
mobility of selenate within plants. In both wheat and mustard, highest Se enrichments were found in
leaves (387 mg/kg×dw in wheat and 931 mg/kg×dw in mustard). Organic species (dimethylselenide
and methylselenocysteine) were found in different parts of both plants, indicating that an active
detoxification response to the high Se uptake is taking place through methylation and/or
volatilization. The high proportion of selenate in wheat and mustard leaves (47% and 70%,
respectively) is the result of the inability of the plant metabolism to completely transform selenate to
non-toxic organic forms, if oversupplied. Methylselenocysteine, a common Se species in
2
accumulating plants, was detected in wheat, suggesting that, in presence of high Se concentration,
this plant develops similar response mechanisms to accumulator plants.
Keywords
Selenium, speciation, wheat, Indian Mustard, synchrotron, XANES