Ground water geochemistry of Ballia district, Uttar Pradesh, India and mechanism of arsenic release.

Threat to human health worldwide due to the natural contamination of arsenic in ground waters has led to extensive studies on factors controlling the distribution of arsenic and conditions leading to arsenic mobilization in different arsenic contaminated areas. Another aspect of the arsenic crisis, especially in South Asia, is the degree of spatial variability of ground water arsenic concentrations. Thus it becomes necessary to study the source and the processes involved in arsenic mobilization into ground water under such conditions. An arsenic contaminated area namely, Ballia district of UP was chosen for this study. A set of 56 samples were collected from India Mark II hand pumps (30-33 m depth) thrice in a year namely pre-monsoon (April '07), monsoon (July '06) and winter seasons (December '06). Nine samples were also collected from deep bore well hand pumps (66-75 m) to study the difference in geochemistry with the shallow pumps. Various water quality parameters like As(III), As(V), sulfate, nitrate, phosphate, bicarbonate, ammonia, were determined. Arsenic concentrations ranged from 0 to 468 microg L(-1) in ground water collected from depths of 30-33 m. In the deeper wells (66-75 m), arsenic concentrations ranged from 12 to 20 microg L(-1). Most samples contained both As(III) and As(V) and the concentration of As(III) was generally equal/higher than As(V). Not much variation of arsenic concentration was observed when sampled in summer, monsoon and winter seasons. Correlation studies among various water quality parameters revealed that reductive dissolution of FeOOH was the most probable mechanism for release of arsenic.

Evaluation of two commercial field test kits used for screening of groundwater for arsenic in Northern India.

In this study two relatively new arsenic field kits, namely Wagtech Digital Arsenator (WFTK) and Chem-In Corp field test kit (CFTK) for arsenic were evaluated. The response of the two field test kits to known standards (Both As(III) and As(V)) is detailed. In addition around 157 arsenic-contaminated field samples obtained from various locations of Ballia and Kanpur districts, U.P., India were tested using the two kits and the results were compared with the laboratory-based colorimetric method (silver diethyldithiocarbamate method, SDDC). The concentration of arsenic in the 157 samples ranged from 0 to 468 microg l(-1). WFTK is seen to be suitable for measuring arsenic concentration <5-100 microg l(-1) using the digital meter. CFTK was not able to detect As(V) and its usage is cautioned in Uttar Pradesh where As(V) is seen to occur in appreciable concentrations. The Pearson's correlation between the silver diethyldithiocarbamate method and WFTK was found to be 0.87 and for the corresponding correlation with CFTK was 0.41 in the concentration range used in this study. Spearman's rank correlation coefficients comparing the WFTK and CFTK to laboratory measurements in the concentration range of 0-100 microg l(-1) were 0.95 (p<0.001) and 0.64 (p<0.001) respectively.

Current knowledge on the distribution of arsenic in groundwater in five states of India.

Testing of groundwater used for drinking for arsenic has been undertaken more widely by state governments in several states of India in recent years with the support of UNICEF. Available data for five states are collated in this paper and this provides the most up-to-date picture of areas known to be affected by arsenic in groundwater in the Indian portion of the Ganges-Brahmaputra river basin. In West Bengal, water from 132,262 government installed handpumps in 8 districts has been tested and overall 25.5% of samples were found to contain arsenic at concentrations greater than 50 microgL(-1) and 57.9% at concentrations greater than 10 microgL(-1). On the banks of the Brahmaputra in Assam, to date, samples from 5,729 government handpump sources in 22 districts have been tested for arsenic. Overall, samples from 6.3% of sources were found to contain arsenic at concentrations greater than 50 microgL(-1) and 26.1% at concentrations greater than 10 microgL(-1). In Bihar, on the River Ganges upstream of West Bengal, 66,623 sources from 11 districts have been tested and water samples from 10.8% of sources were found to contain arsenic at concentrations greater than 50 microgL(-1) and 28.9% at concentrations greater than 10 microgL(-1). Upstream of Bihar in Uttar Pradesh, home of the Taj Mahal, to date water samples from 20,126 government-installed handpump sources have been tested. As a result 2.4% of the samples tested were found to contain arsenic at concentrations greater than 50 microgL(-1) and 21.5% at concentrations greater than 10 microgL(-1). Finally in one district of Jharkhand, lying on the Ganges alluvial plain between Bihar and West Bengal, 9,007 sources have been tested and water samples from 3.7% of sources were found to contain arsenic at concentrations greater than 50 microgL(-1) and 7.5% at concentrations greater than 10 microgL(-1). State governments have adopted different sampling strategies and these are described in this paper. Testing is ongoing in several states and the complete picture is yet to emerge in some areas.

Proton Irradiation Facility and space radiation monitoring at the Paul Scherrer Institute.

The Proton Irradiation Facility (PIF) has been designed and constructed, in cooperation between Paul Scherrer Institute (PSI) and European Space Agency (ESA), for terrestrial proton testing of components and materials for spacecraft. Emphasis has been given to generating realistic proton spectra encountered by space-flights at any potential orbit. The facility, designed in a user-friendly manner, can be readily adapted to the individual requirements of experimenters. It is available for general use serving also in testing of radiation monitors and for proton experiments in different scientific disciplines. The Radiation Environment Monitor REM has been developed for measurements of the spacecraft radiation conditions. Two instruments were launched into space, one into a Geo-stationary Transfer Orbit on board of the STRV-1b satellite and one into a Low Earth Orbit on the Russian MIR station. The next generation of monitors (SREMs--Standard REMs) is currently under development in partnership of ESA, PSI and Contraves-Space. They will operate both as minimum intrusive monitors, which provide radiation housekeeping data and alert the spacecraft when the radiation level crosses allowed limits and as small scientific devices measuring particle spectra and fluxes. Future missions as e.g. INTEGRAL, STRV-1c and PROBA will be equipped with new SREMs.

The fate of diphenyl sulphide, diphenyl sulphoxide and diphenyl sulphone in the rat.

Radiolabelled [UL-14C]-diphenyl sulphide, [UL-14C]-diphenyl sulphoxide and [UL-14C]-diphenyl sulphone were administered by gavage (1.0 mmol/kg body weight) to adult male Wistar rats following an overnight fast. For all compounds, faeces were the major route of excretion of radioactivity (50%). Urinary elimination (40%) was similar during the first (19%) and second (16%) days and a small amount of radioactivity (6%) was found within the carcass after four days. From urinary and faecal data, metabolism occurred via ring hydroxylation with subsequent conjugate formation. Oxidation of the sulphur to form the sulphoxide and sulphone also took place; a small amount of sulphoxide reduction was apparent but no sulphone reduction was found. No evidence for exclusion of the sulphur was obtained, and it appeared unlikely that extensive cleavage of the ring structures occurred.

Rôle of bile in the elimination of dipropyl sulphone from the male rat.

Following oral administration of [35S]-dipropyl sulphone to male Wistar rats (4.24 mmol/kg body wt), the only radioactive component subsequently found in the blood and bile was the sulphone. Biliary excretion played an important rôle in the elimination of this compound, with 16% of the dose excreted during the first twenty-four hours and 33% passing through the bile duct over a two day period. Bile/plasma concentration ratios remained constant during the first day (c. 46-fold), suggesting that a concentration process was taking place and that active transport of this low molecular weight compound (150 Da) into the bile was occurring.

Fate of dipropyl sulphone in rat.

1. Dipropyl [35S]-sulphone was administered by gavage (4.24 mmol/4 ml/kg body weight) to the adult male Wistar rat following an overnight fast. 2. Urine was the major route of excretion (83%) with more radioactivity appearing during the second day (47%) than the first (28%). Only small amounts were found in the faeces (10%). Biliary excretion played an important role with substantial amounts of the dose (33%) passing through the bile duct during 0-48 h. A near total recovery was achieved suggesting that only small amounts (2%) may have been lost as volatile components. 3. Metabolism was limited, the majority (> or = 98%) of the sulphone being recovered unchanged. Oxidation of the sulphur with the formation of inorganic sulphate was the only pathway observed.

Distribution of dipropyl [35S]-sulphoxide in the rat.

Dipropyl [35S]-sulphoxide was administered by gavage (4.24 mmol/kg body weight) to adult male Wistar rats and the placement of radioactivity about the animal examined at 4, 8 and 12 hours post-dosing. Widespread and diffuse distribution throughout soft tissues was observed with the largest amounts of radioactivity being found within the liver (3.2% dose at 4 h) and kidney (1.3% dose at 4 h). Activity levels declined over the 12 hour experimental period. This distribution pattern is discussed and compared with results previously reported for dimethyl sulphoxide.

Fate of dipropyl sulphide and dipropyl sulphoxide in rat.

1. Dipropyl [35S]-sulphide and dipropyl [35S]-sulphoxide were administered by gavage (4.24 mM/4 ml/kg body wt) to adult male Wistar rats following an overnight fast. 2. Urine was the major route of excretion for both compounds, with more radioactivity appearing during the second day (c. 43%) than the first (c. 26%). Only small amounts were found in the faeces (c. 5%). Biliary excretion played an important role with substantial amounts of the dose (c. 25%) passing through the bile duct during 0-48 h. Following ingestion of the sulphide large quantities of radioactivity (18%) were detected in exhaled air. Near total recoveries were achieved for both compounds, although 13% of the radioactivity remained within the carcass 3 days after administration of the sulphoxide. 3. Absorption and elimination half-lives were in the region of 5 and 8 h, respectively, for both compounds, with the sulphoxide plasma profile showing a prolonged plateau region. 4. Metabolism was limited to oxidation of the sulphur with the formation of the sulphoxide and sulphone, and trace amounts of inorganic sulphate.