Hydrochemistry of Arsenic-Enriched Aquifer from Rural West Bengal, India: A Study of the Arsenic Exposure and Mitigation Option

The present study aims to understand the hydrochemistry vis-à-vis As-exposure from drinking groundwater in rural Bengal. The characteristic feature of the groundwaters are low Eh (range, ?151 to ?37 mV; mean, ?68 mV) and nitrate (range, 0.01–1.7 mg/l; mean, 0.14 mg/l) followed by high alkalinity (range, 100–630 mg/l; mean, 301 mg/l), Fe (range, 0.99–38 mg/l; mean, 8.1 mg/l), phosphate (range, 0.01–15 mg/l; mean, 0.54 mg/l), hardness (range, 46–600 mg/l; mean, 245 mg/l) and sulphate (range, 0.19–88 mg/l; mean, 7.2 mg/l), indicating reducing nature of the aquifer. The land use pattern (sanitation, surface water bodies, sanitation coupled with surface water bodies and agricultural lands) demonstrates local enrichment factor for As/Fe in groundwater. Among these, sanitation is the most prevailing where groundwater is generally enriched with As (mean, 269 μg/l) and Fe (mean, 9.8 mg/l). Questionnaire survey highlights that ～70% of the villagers in the study area do not have proper sanitation. This demonstrating the local unsewered sanitation (organic waste, anthropogenic in origin) could also cause As toxicity in rural Bengal. In the agricultural lands, higher mean values of alkalinity, phosphate, sulphate, hardness and electrical conductivity was observed, and could be linked with the excessive use of fertilizers for agricultural production. Bio-markers study indicates that the accumulation of As in hair and nail is related with the construction of exposure scenario with time dimension. The strength and weakness of the on-going West Bengal and Bangladesh drinking water supply scenario and achievability towards alternative options are also evaluated.     

Geochemistry of Tungsten and Arsenic in Aquifer Systems: A Comparative Study of Groundwaters from West Bengal, India, and Nevada, USA

The objective of the current study was to estimate the dose in human tissues after inhalation exposure to airborne particulate matter-bound metals at a landfill site. Field measurements have revealed that the 8-h permissible exposure limit set by the Occupational Safety and Health Administration for particulate matter (PM₁₀) was not exceeded for the working personnel at an outdoor weighing facility in the Akrotiri landfill (Chania, Greece). However, PM₁₀ concentrations were exceeding the EU health protection standards (50 μg/m³). Furthermore, dust emanating from landfill operations contains traces of heavy metals due to the nature of materials (e.g., sludge, batteries) which have been deposited over the lifetime of the landfill. In addition, particulate matter-bound metals concentrations at the landfill are enhanced by refuse truck emissions (e.g., exhaust, tire wear dust, brake wear dust, road surface wear dust and resuspension of deposited PM on a road surface) and resuspension from the surface of the composting site. Estimations of particle-bound metals dose in the human body were performed for arsenite (AS^III), lead (Pb) and cadmium (Cd). The Exposure Dose Model (ExDoM) in conjunction with a Physiologically Based PharmacoKinetic (PBPK) model was applied to determine the dose for an adult Caucasian male worker. The ExDoM was used to estimate the human exposure and the deposition, dose, clearance, retention of particulate matter-bound metals in the human respiratory tract and the mass transferred to the gastrointestinal tract and blood. The PBPK model was developed to describe the movement of metals from the blood into the tissues as a blood-flow-limited model. The results showed that after 1 day of exposure to PM_AsIII, the major accumulation occurs in the lung, muscle and liver. In addition, for PM_Pb, the major accumulation occurs in the bone, blood and muscle whereas as regard PM_Cd the major accumulation occurs in the other tissues (the rest of the body), kidney and liver. The results indicate an increased health risk for an adult Caucasian male worker at the landfill site due to exposure to elevated particulate matter concentrations and their associated metallic content.     

Speciation in Chenopodium in West Bengal, India

Two diploid cytotypes of Chenopodiumalbum have earlier been proposed as the probable ancestors ofhexaploid C. album in Gangetic Plainof West Bengal on the basis of cytomorphological data. The present study withthe diploid cytotypes of C. album (onebroad leaved, another narrow leaved), one wild species, C.murale and the hexaploid C.album utilizing parameters like seed protein, isozyme,RAPD, tissue culture along with conventional cytomorphological data supports ourearlier hypothesis of allopolyploid origin of hexaploid C.album. The results indicate that all the three diploidprogenitors have contributed for the evolution of present day semi-cultivatedhexaploid C. album. This study furthersuggests that the diploid cytotypes had been evolved sympatrically.     

Study of the Suitability of Selected Extractants for Determination of Plant-Available Arsenic in Some Inceptisols of West Bengal,India

A study was conducted to assess the suitability of extractants for soil-available arsenic (As) under kharif rice (MTU-7029). Ten soil samples were collected from different locations of varying topography and land-use patterns from Nonaghata-Uttarpara of West Bengal. A pot study with MTU-7029, exposed to varying levels of arsenic (0 to 90 mg kg^?1 of soil), was conducted for two successive years. Eight extractants, namely sodium bicarbonate (NaHCO₃), ammonium acetate (CH₃COONH₄), monopotassium phosphate (KH₂PO₄), hydrochloric acid (HCl) + sulfuric acid (H₂SO₄), ammonium carbonate [(NH₄)₂CO₃], sodium hydroxide (NaOH), malic–citric acid, and ethylenediaminetetraacetic acid (EDTA), were assessed. Soil test and crop uptake correlations revealed that 0.5 M NaHCO₃ was the best extractant. In a lateral study, three soils were collected from a conventional rice field of Nonaghata-Uttarpara, Gotera, and Ghentughachi of West Bengal and sequentially extracted. The results showed that the relative abundance of As fractions were in the order of water-soluble As < Ca As < Al As < amorphous Fe As < crystalline Fe As.     

Boron fertilization effects in processing grade potato on an Inceptisol of West Bengal,India

A 2-year field trial was conducted in processing grade potato cv. Kufri Chipsona-3. The treatments comprised recommended dose of fertilizer (RDF) (200:150:150 N:P₂O₅:K₂O kg ha^?1) with or without boron (B) application (soil and foliar). The results revealed that B fertilization significantly increased tuber number and yield. Three sprays of 0.1% boric acid (at 40, 50 and 60 days after planting) produced the maximum number and yield of tubers and enhanced B uptake in potato tuber, haulm as well as in total plant accounting 85.8, 182.0 and 169.8% more than control, respectively. The same treatment came up with greatest net return and benefit: cost ratio. B fertilization exerted significant influence on available N and B status of post-harvest soil, while the effect was non-significant on available P and K. Results suggest that right dose and method of B application is vital for optimizing tuber yield and B-use efficiency for processing grade potato.     

Arsenic speciation in food and estimation of the dietary intake of inorganic arsenic in a rural village of West Bengal, India

Arsenic (As) species were quantified by HPLC-HG-AFS in water and vegetables from a rural area of West Bengal (India). Inorganic species predominated in vegetables (including rice) and drinking water; in fact, inorganic arsenic (i-As) represented more than 80% of the total arsenic (t-As) content. To evaluate i-As intake in an arsenic affected rural village, a food survey was carried out on 129 people (69 men and 60 women). The data from the survey showed that the basic diet, of this rural population, was mainly rice and vegetables, representing more than 50% of their total daily food intake. During the periods when nonvegetarian foods (fish and meat) were scarce, the importance of rice increased, and rice alone represented more than 70% of the total daily food intake. The food analysis and the food questionnaires administrated led us to establish a daily intake of i-As of about 170 microg i-As day (-1), which was above the tolerable daily intake of 150 microg i-As day (-1), generally admitted. Our results clearly demonstrated that food is a very important source of i-As and that this source should never be forgotten in populations depending heavily on vegetables (mainly rice) for their diet.     

Boron adsorption and desorption in some acid soils of West Bengal,India

Laboratory and greenhouse experiments were conducted to determine the influence of soil properties on adsorption and desorption of boron (B) as well as to estimate the degree of reversibility of adsorption reactions. The utility of Freundlich and Langmuir equations for characterizing the plant availability of applied B in soils was established using soybean [Glycine max (L.) Merr.] as a test crop. The adsorption-desorption study revealed that Fe₂O₃ and clay were primarily responsible for retaining added B in all the 25 different soils under investigation. Organic carbon, pH and cation exchange capacity (CEC) positively influenced the adsorption of B while free Fe₂O₃, organic carbon and clay retarded release of B from these soils. The degree of irreversibility (hysteresis) of B adsorption/desorption increased with increase in organic carbon and CEC of these soils. Freundlich isotherm proved more effective in describing B adsorption in soils as compared to Langmuir equation. The split Langmuir isotherm demonstrated that any of the adsorption maxima, calculated from lower, upper or entire isotherm, could be of practical use. Contrary, bonding energy coefficient, calculated either at lower or higher equilibrium concentration failed to show any practical benefit. Regression models as a function of B application rate and adsorption equation parameters to predict B uptake from applied B, demonstrated the utility of Langmuir and Freundlich equation parameters.     

Boron Fertilization in Sunflower (Helianthus annuus L.) in an Inceptisol of West Bengal,India

This study is a synthesis of information on growth, yield, and boron-use efficiency of hybrid sunflower (cultivar Aditya) in an inceptisol (Gangetic alluvium) of West Bengal, India, under varied proportions of soil and foliar-applied boron. Foliar spray of boron (B), under all circumstances, performed better than soil application of B fertilizers with regard to sunflower seed and total dry-matter yield, B uptake, and B-use efficiencies, while 0.2 percent foliar B spray was associated with greatest B recoveries, B-use efficiencies, and sunflower seed yields in the experimental years.     

Evolution of the Lower Gangetic Plain landforms and soils in West Bengal,India

Three major landforms, Uplands, Old Fluvial/Deltaic Plains and Young Fluvial Plains are identified from the Lower Gangetic Plains of West Bengal, India, on the basis of remote sensing and field studies. Morphologic, quantitative and thermoluminescence studies of soils of the study area have been conducted. Two types of Uplands are recognised: Upland in the west overlain by red soils (autochthonous and allochthonous types) and upland in the north (Barind Tract), characterised by three topographic levels. Aspects of the autochthonous Upland Red Soils (Lower to Middle Pleistocene age) show the ferrugination (ferrisol) phase of development. Soils of the Old Fluvial/Deltaic Plains (6–3 ka) and Lower Level of the Barind Tract have argillic horizons and exhibit the fersiallitisation phase of development. Development of ferrugination and fersiallitisation phases was favored due to the pre-weathered nature of the parent material. Soils of the Old Fluvial/Deltaic Plains, Barind Tract (Lower Level) and Young Fluvial Plains show effects of hydromorphism due to waterlogging in the form of segregations of Fe–Mn oxides/gleying and chloritisation, probably due to ferrolysis in the upper horizons of some of these soils. Neotectonics seems to have affected development of landforms and soils significantly. Due to reactivation of some basement faults in the western region, some tectonic blocks subsided, causing transgression during the Early Pleistocene and at ca. 7 ka. Subsequent uplift of these blocks caused regressions and development of soils on the exposed landscapes. Episodic uplift of the Barind Tract in the northern region may have given rise to three topographic levels. Some faults confine the courses of the Damodar, Ganga and Bhagirathi rivers.     

Arsenic Contamination in Soils Affected by a Pyrite-mine Spill (Aznalcóllar, SW Spain)

On 1998, a settling pond of a pyrite mine in Aznalcóllar (SW Spain) broke open, spilling some 3.6?×?10⁶ m³ of water and 0.9?×?10⁶ m³ of toxic tailings into the Agrio and Guadiamar river basin 40 km downstream, nearly to Doñana National Park. The soils throughout the basin were studied for arsenic pollution. Almost all the arsenic penetrated the soils in the solid phase (tailings) in variable amounts, mainly as a result of the different soil structure. The chemical oxidation of the tailings was the main cause of the pollution in these soils. A study of the relationships between the main soil characteristics and arsenic extracted with different reagents (water, CaCl₂, acetic acid, oxalic–oxalate and EDTA) indicates a direct relationship with the total arsenic concentration. The highest amount of arsenic was extracted by oxalic–oxalate (24%–36% of the total arsenic), indicating the binding with the iron oxides.     

Arsenic in Water,Soil, and Rice Plants in the Indo-Gangetic Plains of Northwestern India

Arsenic (As), which is present in all living tissues, water, and soil, is considered toxic to humans and animals. Because of the presence of arsenic-contaminated sites throughout the world, there is a renewed interest in studying the status of As in water, soil, and plants. Concentrations of As above the permissible limit have been reported in Lower Ganges Plains (West Bengal in India and Bangladesh). The present investigation aimed to examine the concentration of As in water, soil, and rice plants in the Upper/Trans-Ganges Plains covering Punjab in northwestern India. In total, 200 water samples were collected from different locations in Punjab. Corresponding soil, rice grain, and straw samples were collected from the same locations as the water samples had been collected. In addition to deep tube well water (>125 m deep), water samples from shallow hand pumps (<50 m deep) and canals were also collected. The samples were analyzed for total As concentration using an atomic absorption spectrophotometer equipped with a hydride generating system (AAS-HG). The concentration of As in tube well water samples varied from 5.33 to 17.27 μg As L^–1, with about 40% samples having As concentrations greater than the permissible limit (10 μg As L^–1). None of the hand pump and canal water samples had As concentrations greater than permissible limits. The As concentration of surface soils varied from 1.09 to 2.48 mg As kg^–1. There was no trend in the distribution of As with depth of soil. The concentration of As in rice straw varied from 4.05 to 15.06 μg As kg^–1 and that of grain from 1.48 to 6.87 μg As kg^–1. The concentration of As was lower in edible grain than in inedible straw. There was a positive and significant correlation between As concentration in tube well water and As concentration in surface soils. The buildup of As in soils was directly related to the As concentration of tube well waters. There was a significant correlation between As in water and As in plants. However, a nonsignificant correlation existed between As in soil and As in plants. This indicates that plants absorbed more As from irrigation water than that from soil. This also suggests that irrigation with such waters over a longer period of time may have detrimental effects on soil and on plants, animals, and humans. There is thus a need to continuously monitor the As concentration in undergroundwater.     

Screening of Basmati Rice Varieties for their Arsenic Accumulation in Punjab,North-West India

A pot study was conducted to screen different basmati rice varieties for their accumulation of arsenic (As). Different amounts of arsenic (0–800 µg/L) were applied through irrigation water to four basmati rice varieties (Pusa basmati-1121, Pusa Punjab basmati-1509, Punjab basmati-2, and Punjab basmati-3). Highest arsenic concentration was found in the grains of Punjab basmati-3 and lowest in the grains of Pusa Punjab basmati-1509. In all varieties, grain As concentration ranged from 0.038 to 0.288 mg/kg, which was within the permissible limit of 1.0 mg/kg in rice grain recommended by World Health Organization (WHO). In husk, highest As concentration was found in Pusa basmati-1121 and lowest in Punjab basmati-2. Among the four varieties, highest content of As was accumulated in roots and straw of Pusa Punjab basmati-1509, whereas least was accumulated in Punjab basmati-2. The distribution of arsenic among plant parts was found in the order: roots > straw > husk > grain. The mean arsenic concentrations in grain, husk, straw, and root of basmati rice varieties increased with increasing concentration of arsenic in irrigation water. Highest grain yield was obtained in Pusa Punjab basmati-1509 variety due to lesser accumulation of arsenic compared with other varieties. Rice yield, plant height, root weight, straw weight, test weight, effective tiller, and filled grain per panicle decreased with increase in arsenic concentration in irrigated water.     

Spatial variability and concentration of arsenic in the groundwater of a region in Nadia district,West Bengal,India

Arsenic pollution in ground water in India and Bangladesh is considered to be the largest contamination problem in the world. About 15?–?18% of the area of West Bengal, India comes under the threat of arsenic (As) contamination and around 5.36 million people are exposed to this hazard. A detailed isoline map corresponding to variations in arsenic concentration and their spatial distribution was prepared for the study area, which comprised two villages Ghentugachi and Gotera in Nadia district, West Bengal and the total area covered was 808 hectares. The pattern of arsenic contamination was highly irregular and diverse. About 11.2% of the study area was affected most (?>?0.50?mg As l^?1) with sample As values reaching 0.71 and 0.80?mg?l^?1. About 22.5% of the area had As content between 0.20 and 0.50?mg?l^?1 and 33.9% of study area had As content below the WHO guideline of 0.01?mg As/l. Thus the local population living around these areas is vulnerable and exposed to arsenic contamination. None of the water samples exceeded the allowable limit (1.0?mg As l^?1) of As for water used in irrigation purposes. The spatial distribution map helped to determine zones with different As concentrations, making it possible to identify high-risk zones.     

Effect of Drip Fertigation on Yield,Water Use Efficiency,and Nutrients Availability in Banana in West Bengal,India

Field studies were conducted during 2008–2009 and 2009–2010 at the Gangetic alluvial plains of West Bengal, India, to assess the different levels of drip fertigation at variable evaporation replenishment compared to surface irrigation and conventional soil fertilization on yield, water use efficiency, and nutrients availability in plant and ratoon crop of banana. The experiment was laid in an Augmented Factorial Complete Block Design with three replications having three drip irrigation schedules at 50%, 60%, and 70% of cumulative pan evaporation (CPE) and three drip fertigation schedules at 50%, 60%, and 80% of recommended nitrogen, phosphorus, and potassium (NPK) fertilizers with inclusion of conventional surface irrigation at 100% of IW/CPE. The results showed that fruit yield of plant and ratoon crop increased progressively with increasing levels of irrigation water (up to 60% CPE) and NPK fertigation through the drip system. However, maximum fruit yield and water use efficiency of crops was obtained with drip irrigation at 60% CPE with NPK fertigation at 80% of recommended dose. Drip irrigation, as a whole, registered higher fruit yields and water use efficiency with savings of 38.3–41.5% of water compared to surface irrigation. Availability of N, P, and K in soil at vegetative, shooting, and harvesting stages for plant and ratoon crop consistently increased with increasing rate of irrigation water and NPK fertigation through the drip system. Higher availability of macronutrients in soil was recorded with drip irrigation at 70% CPE with 80% of recommended drip NPK fertigation. Overall drip fertigation system improved the available plant nutrients in the soil as compared with traditional surface irrigation.     

Evaluation of Chemical Extraction Methods for Determining Plant-Available Potassium in Some Soils of West Bengal,India

The effectiveness of eight chemical extraction methods was evaluated on 15 Indian soils for the prediction of plant-available potassium (K⁺) to Sudan grass (Sorghum vulgare var. sudanensis) grown in modified Neubauer technique. Average amounts of soil K⁺ extracted were in descending order: Morgan’s reagent > 0.5 M sodium bicarbonate (NaHCO₃) > neutral 1N ammonium acetate (NH₄OAc) > 1N nitric acid (HNO₃) > 0.02 M calcium chloride (CaCl₂) > 0.1N HNO₃ > Bray and Kurtz No.1> distilled water. The highest simple correlation with plant K⁺ uptake was obtained with NH₄OAc-K⁺ (r = 0.866**) and the lowest with CaCl₂-K⁺ (r = 0.45*). To develop the predictive models using stepwise regression, plant K⁺ uptake was used as the dependent variable and the extractable soil K⁺, pH, sand, silt and organic carbon (C) contents as the independent variables. Based on the final R², the NH₄OAc model was found to be the best predictor of plant-available K⁺ in the soils when used along with sand and organic C.     

Arsenic biogeochemistry as affected by phosphorus fertilizer addition,redox potential and pH in a west Bengal (India) soil

This laboratory experiment systematically examines arsenic, iron, and phosphorus solubilities in soil suspensions as affected by addition of phosphorus fertilizer under different redox potential (Eh) and pH conditions. Under aerobic conditions, As solubility was low, however, under moderately reducing conditions (0, − 150 mV), As solubility significantly increased due to dissolution of iron oxy-hydroxides. Upon reduction to − 250 mV, As solubility was controlled by the formation of insoluble sulfides, and as a result soluble As contents significantly decreased. Soluble Fe concentration increased from moderate to highly anaerobic conditions; however, it decreased under aerobic conditions likely due to formation of insoluble oxy-hydroxides. A low pH, 5.5, led to increased soluble concentrations of As, Fe, and P. Finally, addition of P-fertilizers resulted in higher soluble P and As, even though the concentration of As did not increased after an addition rate of 600 mg P kg^− 1 soil.     

Arsenic in Rice Soils and Potential Agronomic Mitigation Strategies to Reduce Arsenic Bioavailability: A Review

Soils used for rice (Oryza sativa L.) cultivation in some areas contain high concentrations of arsenic (As) due to irrigation with groundwater containing As and intensive use of agrochemicals or industrial residues containing As. To restrict rice uptake of As in these soils, approaches to reduce As input and bioavailability must be considered. One approach to reduce As input into rice soils or uptake by rice is cultivating rice under aerobic, intermittent flooding, or alternate wetting and drying (AWD) conditions, rather than in submerged soils, or use of irrigation water low in As. For reducing As bioavailability in soil, aerobic or AWD rice culture and application of biochar, sulfur (S), and/or rice polish to soil are promising. Moreover, use of As-hyperaccumulating plant species (e.g., Pteris vittata L.) in rotation or combinations with favourable plant species (e.g., Azolla, Chlorella, or Nannochloropsis species) can also be promoted, in addition to using rice cultivars that are tolerant to As. Though applications of high doses of phosphorus (P), iron (Fe), and silicon (Si) fertilizers have shown promise in many instances, these methods have to be practiced carefully, because negative effects have also been reported, although such incidents are rare. Major factors affecting As speciation and bioavailability in soil are chemical properties such as redox status, pH, and Fe, P, Si, and S concentrations, physical properties such as texture and organic matter, and biological properties such as methylation activity by soil microorganisms. However, as many of these factors interact, long-term examination under field conditions is needed before measures are recommended for and implemented in farmers' fields.     

Humus Characterization of Humid Tropical Forest,Tea Garden,and Field Crop Soils of West Bengal,India: Chemical,Potentiometric, and Spectroscopic Methods

Humic acids (HA) and fulvic acids (FA) were extracted from tropical humid forest, tea garden, and field crop soils, and their chemical, potentiometric, and spectrophotometric properties were measured. There was less HA than FA in the cultivated soils. The HAs contained more carbon (C) and nitrogen (N) and had greater C/H ratios but lower O (oxygen)/H (hydrogen) ratios than FAs. Cultivated soils had greater total acidity than the forest soil generally because of both —COOH and phenolic-OH. Molecular weights of HA an FA, estimated from intrinsic viscosities, revealed that cultivation had reasonably reduced the molecular weights. The difference in pH (ΔpH) values, corresponding to three-fourths and one-fourth of the pH at final inflexion point showed that they were polyprotic. The longer time required for stability of greater pH of HAs was related to greater degree of stable coiling. The (E₄/E₆), in general, revealed a greater amount of aliphatic moiety rather than aromatic moiety.     

Arsenic Contamination and Dispersion in the Engenho Inlet,Sepetiba Bay,SE, Brazil

Arsenic distribution and dispersion in sediments of the EngenhoInlet and the Sepetiba Bay were investigated in order to evaluate the extent of the contamination caused by a metallurgical plant installed in the Sepetiba Bay watershed. The ore used in the smelting process, the soil around the plant, and ore waste collected inside the plant were also analyzed for As. Very high As concentrations in the stronglyand weakly bound fractions (up to 63 000 and 52 700 μgg^-1, respectively) were found in the ore waste. The soilsalso contained high concentrations of both the strongly andweakly bound fractions (748 and 636 μg g^-1, repectively), although the ore itself contained lower levelsof the two fractions (63 and 13 μg g^-1, respectively).The sediments of the Engenho Inlet had a high degree of contamination (up to 347 μg g^-1) decreasing toward Sepetiba Bay where the lowest concentrations were found (up to 50 μg g^-1). Altough lower concentrations were found in the Sepetiba Bay sediments, they are 5 times higher than the world average. The results showed that there is an As transport from the Engenho Inlet to the Sepetiba Bay. These results suggests that the bay's fish and mollusk stock my be contaminated. This contamination may adversely affect the health of the local population, whose main protein supply is seafood.     

印度喜马拉亚山东南麓大吉岭区之土壤与植物

1945年10月中旬,作者留印三月另一周,曾作三次野外调查,计包括印缅边区、恒河平原及喜马拉雅山东南麓等三区,茲先将大吉岭区调查结果,草成此文