Gunnar Jacks

Occurrence of Arsenic-contaminatedGroundwater in Alluvial Aquifers from Delta Plains, Eastern India: Options for Safe Drinking Water Supply

Abstract Arsenic contamination in groundwater used for drinking purposes has been envisaged as a problem of global concern. Exploitation of groundwater contaminated with arsenic within the delta plains in West Bengal has caused adverse health effects among the population within a span of 8-10 years. The sources of arsenic in natural water are a function of the local geology, hydrology and geochemical characteristics of the aquifers. The retention and mobility of different arsenic species are sensitive to varying redox conditions. The delta plains in West Bengal are characterized by a series of meander belts formed by the fluvial processes comprising different cycles of complete or truncated fining upward sequences (sand-silt-clay). The arseniferous groundwater belts are mainly located in the upper delta plain and in abandoned meander channels. Mineralogical investigations have established that arsenic in the silty clay as well as in the sandy layers occurs as coatings on mineral grains. Clayey sediments i...

Concentration and fractionation of heavy metals in roadside soils receiving de-icing salts

Soil was sampled along two lines of a highway, 0.5 m and 2.5 m from the asphalt surface, and in an infiltration pond for highway runoff. The study area was located in the infiltration area of the reserve water supply for a . community. The concentrations of Cd, Pb and Zn in soil samples from the highway 0.5 m andror in the infiltration pond exceeded guideline values for less sensitive land-use with groundwater protection. The highest Pb concentration y1 . measured 542 mg kg was 34 times the average Pb concentration in soils in Sweden, and exceeded the Swedish guideline value by a factor of almost two. Cadmium in the infiltration pond exceeded the guideline value almost three times. An increased concentration with soil depth for Cd, Pb, Cu, Zn and PAHs in the infiltration pond showed that downward transport had occurred. This was supported by a Pb concentration exceeding the limit for drinking water quality in the groundwater 4.5 m below the soil surface in the infiltration pond. The ESP exchangeable sodium . . percentage in some samples was high enough 10)27% for dispersion of soil colloids to occur. The Tessiers sequential extraction scheme showed that Pb and Zn occurred mostly in association with the oxide bound fraction whereas Cu was mainly associated with the organic fraction, e.g. colloids. Another important fraction for Pb was the carbonate fraction. The study showed that a large part of the Pb, Cu and Zn in roadside soils is vulnerable to leaching when exposed to a high NaCl concentration, reducing conditions or to a lowering in pH. Regression analyses showed that a high concentration of Na predominately displaces Ca of the base cations from the exchange sites in the soil. The highly significant relationships observed between soil properties and chemical fractions of the metals make the result reliable for the fractions that predominate. Q 1998 Elsevier Science B.V. All rights reserved.

Weathering rates and 87Sr/86Sr ratios: An isotopic approach

The 87Sr/86Sr ratios of precipitation, throughfall, groundwater, streamwater and mineral matter were analyzed. Precipitation strontium ratios are around 0.71; throughfall, which is affected by strontium from the mineral soil, has ratios of 0.72–0.73; and shallow groundwater in a drug well and runoff have ratios around 0.73–0.74. There is a tendency for this relationship to be reversed for discharge. Higher ratios are associated with lower discharges. Water from a fracture zone gave the highest value (0.78), approaching the value of the bedrock (around 0.85). A calcium budget, which reflects the mean conditions over a few years, has been calculated. This budget indicates that weathering should be of the order of 8 kg Ca ha−1yr−1 to maintain the pool of exchangeable calcium at a constant level. The major anion in the runoff is suphate, which has entered the system in the form of “acid rain”. Sulphur deposition has been rather constant over the last two decades. If acidification had an effect on weathering of silicates this would have shown up in a tendency of the strontium isotope ratios toward higher values in the soil pool and in runoff water. Thus its seems from the observed ratios that at least a major portion of the excess calcium export resulting from sulphur deposition is taken from the soil pool, resulting in a gradual acidification of the soil.

Hydrogeochemical comparison and effects of overlapping redox zones on groundwater arsenic near the Western (Bhagirathi sub-basin, India) and Eastern (Meghna sub-basin, Bangladesh) margins of the Bengal Basin

Although arsenic (As) contamination of groundwater in the Bengal Basin has received wide attention over the past decade, comparative studies of hydrogeochemistry in geologically different sub-basins within the basin have been lacking. Groundwater samples were collected from sub-basins in the western margin (River Bhagirathi sub-basin, Nadia, India; 90 samples) and eastern margin (River Meghna sub-basin; Brahmanbaria, Bangladesh; 35 samples) of the Bengal Basin. Groundwater in the western site (Nadia) has mostly Ca-HCO(3) water while that in the eastern site (Brahmanbaria) is much more variable consisting of at least six different facies. The two sites show differences in major and minor solute trends indicating varying pathways of hydrogeochemical evolution However, both sites have similar reducing, postoxic environments (p(e): +5 to -2) with high concentrations of dissolved organic carbon, indicating dominantly metal-reducing processes and similarity in As mobilization mechanism. The trends of various redox-sensitive solutes (e.g. As, CH(4), Fe, Mn, NO(3)(-), NH(4)(+), SO(4)(2-)) indicate overlapping redox zones, leading to partial redox equilibrium conditions where As, once liberated from source minerals, would tend to remain in solution because of the complex interplay among the electron acceptors.

Metal contamination at a wood preservation site: characterisation and experimental studies on remediation

The aim of this investigation was to determine the occurrence of As, Cu, Cr and Zn in the soil at an abandoned wood preservation unit and to examine some possible extractants for the contaminants in the soil. The mean As content of the contaminated surface soils (0-10 cm) was 186 mg kg(-1), where as the mean concentrations of Cu, Cr and Zn in soils from the contaminated area were 26, 29 and 91 mg kg(-1), respectively. The elevated As content in the mineral soils is related to adsorption of inorganic As phases in the fine grained fractions, which are characterised by large surface area and high positive surface charge under the current acidic conditions. Cu and Cr were found to be rather mobile, which is reflected in their lower abundance in soils and significant accumulation in sediments in the drainage leaving the area. The fine fraction of the soil (<0.125 mm) has an average metal content increased by nearly 34% as compared to the <2-mm fraction conventionally used for the analysis and assessment of soil contamination. The <2-mm fraction constitutes approximately 65% of the total weight while the fine fraction (<0.125 mm) constitutes approximately 10%. These facts, taken together, are essential for the choice of remediation measures. Oxalate solutions have been tested as extractants for soil remediation. Dark acid oxalate extraction dissolves the amorphous Al- and Fe-oxides and hydroxides and mobilises the adsorbed inorganic As species. Oxalate also acts as a ligand for the cationic heavy metals, releasing them from exchangeable sites. With a three-step sequential leaching, up to 98-99% of the metals could be removed. At lower concentrations and higher pH, the leaching decreased to approximately 70%.

Apatite as a P source in mycorrhizal and non-mycorrhizal Pinus sylvestris seedlings

The objectives of the study are firstly to test the ability of ectomycorrhizal pine seedlings to use apatite as a P source in comparison with non-mycorrhizal pine seedlings and secondly, to determine if there is a relation between exudation of organic acids and the ability to use apatite as a P source. Non-mycorrhizal Pinus sylvestris (L.) seedlings and seedlings ectomycorrhizal with 4 different isolates of ectomycorrhizal fungi were grown for 220 days in sand/peat filled pots with apatite (Ca5(F,OH)(PO4)3) as the sole P source. In an additional experiment, non-mycorrhizal Pinus sylvestris (L.) seedlings and seedlings ectomycorrhizal with 2 different isolates of ectomycorrhizal fungi were grown without any P source for 250 days. All other nutrients were supplied in a balanced nutrient solution.Ectomycorrhizal seedlings grew less than non-mycorrhizal seedlings but ectomycorrhizal seedlings produced a large external mycelium not included in the biomass estimates. All seedlings in the present study had low shoot:root ratios compared to seedlings growing under optimal conditions. All seedlings grown with apatite as P source had higher foliar P concentrations (0.71–2.11 mg/g) than seedlings growing without any P source (0.57–0.75 mg/g) indicating a significant ability to use apatite as a P source. Seedlings colonized by Suillus variegatus and Paxillus involutus had higher concentrations and total contents of P in shoots compared with non-mycorrhizal seedlings, indicating significant improvement of P uptake by these fungi in comparison with non-mycorrhizal seedlings or seedlings colonized Piloderma croceum.No clear relationship between exudation of organic acids and uptake of P was found. Seedlings colonized by S. variegatus reduced the pH of the soil more than seedlings colonized by P. involutus or non-mycorrhizal seedlings. It is suggested that S. variegatus colonization improves the P uptake by reducing the pH of the soil while P. involutus improves P uptake by having a greater ability to absorb dissolved phosphate than non-mycorrhizal roots or roots colonized by the other fungi used in the study.

Geochemical characterisation of shallow aquifer sediments of Matlab Upazila, Southeastern Bangladesh — Implications for targeting low-As aquifers

High arsenic (As) concentrations in groundwater pose a serious threat to the health of millions of people in Bangladesh. Reductive dissolution of Fe(III)-oxyhydroxides and release of its adsorbed As is considered to be the principal mechanism responsible for mobilisation of As. The distribution of As is extremely heterogeneous both laterally and vertically. Groundwater abstracted from oxidised reddish sediments, in contrast to greyish reducing sediments, contains significantly lower amount of dissolved arsenic and can be a source of safe water. In order to study the sustainability of that mitigation option, this study describes the lithofacies and genesis of the sediments within 60 m depth and establishes a relationship between aqueous and solid phase geochemistry. Oxalate extractable Fe and Mn contents are higher in the reduced unit than in the oxidised unit, where Fe and Mn are present in more crystalline mineral phases. Equilibrium modelling of saturation indices suggest that the concentrations of dissolved Fe, Mn and PO(4)(3-)-tot in groundwater is influenced by secondary mineral phases in addition to redox processes. Simulating As(III) adsorption on hydroferric oxides using the Diffuse Layer Model and analytical data gave realistic concentrations of dissolved and adsorbed As(III) for the reducing aquifer and we speculate that the presence of high PO(4)(3-)-tot in combination with reductive dissolution results in the high-As groundwater. The study confirms high mobility of As in reducing aquifers with typically dark colour of sediments found in previous studies and thus validates the approach for location of wells used by local drillers based on sediment colour. A more systematic and standardised colour description and similar studies at more locations are necessary for wider application of the approach.

Groundwater As mobilization in the Bengal Delta Plain, the use of ferralite as a possible remedial measure—a case study

Abstract High As groundwater (50–1600 μg l−1) poses the greatest threat to human health in the Holocene alluvial aquifers of the Bengal Delta Plain (BDP) with increasing global concern in recent years. This study deals with groundwater quality and As mobilization vis-a-vis employing ferralite as a remedial option for removal of As from groundwater. The investigation suggests that Fe-rich As traps undergo degeneration to produce Fe oxyhydroxide (HFO) as coating/precipitation on the fine-grained sediment surface and release redox sensitive species (As, Fe and Mn) as well as PO43− into the groundwater under local reducing conditions. Sediment analysis reveals the presence of AsT (average 17.2 mg/kg), FeT (average 0.93 g/kg) and organic matter (average 7.6 g/kg). Sediment AsT and FeT content cannot validate the presence of high groundwater As/Fe. FeII catalysed FeIII reduction, induced by dissimilatory Fe reducing bacteria liberate the more toxic AsIII than AsV. The release of redox sensitive species (As, Fe and Mn) are the functions of bio-available forms of Fe oxides, concentration and distribution of fresh organic matter and availability of electron donors within the sediment. Further attempt is made to establish the role of ferralite, enriched with natural HFO as an As scavenger. Batch studies demonstrate the competency of the material over the natural/commonly used chemical coagulants generally used for water treatment. The high pHpzc value, 8.5 of ferralite along with the adsorption studies over a wide range of pH elucidate the effectiveness of the material in adsorbing both AsIII and AsV from the well-buffered groundwater. The presence of FeII in the system enhances the As removal process. The Langmuir adsorption isotherm further confirms the merit of ferralite as an efficient As scavenger. The material has been shaped for a fixed bed filter medium to remove As from groundwater (both laboratory and field scale). Ferralite is also cost effective (US

Strontium isotopes in trees as an indicator for calcium availability.

8/metric ton of ferralite with a density 1.17 kg/dm3). Transportation cost for ferralite (from ferralitic bed to the affected area) is US

Risk of Arsenic Exposure from Drinking Water and Dietary Components: Implications for Risk Management in Rural Bengal

16/ton/1000 km whereas US