Dhanwinder Singh

Occurrence and Geochemistry of Arsenic in Groundwater of Punjab, Northwest India

Abstract Arsenic (As) is a deadly poison at high concentrations. It is mysterious in the sense that people are exposed to it most of the time through drinking groundwater, fortunately at much lower concentrations than the deadly levels, and usually without knowing it. Arsenic content in alluvial aquifers of Punjab varied from 3.5 to 688 µg L−1. Arsenic status of groundwater is classified into low (<10 µg L−1), moderate (≥10 to <25 µg L−1), high (≥25 to <50 µg L−1), and very high (>50 µg L−1). In zone I, the concentration of As in groundwater varied from 3.5 to 42 µg L−1 with a mean value of 23.4 µg L−1. On the basis of these limits, only 8% of samples were low, whereas 51 and 41% of the total samples collected from this region fall in the moderate and high As categories. The concentration of As in groundwater of zone II varied from 9.8 to 42.5 µg L−1 with a mean value of 24.1 µg L−1. Arsenic concentration in the alluvial aquifers of the central plain of zone II is 2 and 52% in the low and moderate limits. In this region, 46% of groundwater sites contain high As concentrations. Arsenic concentrations in the aridic southwestern parts are significantly different from other two provinces. The As concentration ranged from 11.4 to 688 µg L−1 with average value of 76.8 µg L−1. Eleven percent of the aquifers of the southwestern region of zone III are in the moderate category, 54% in the high, and 35% in the very high. According to safe As limits (<10 µg L−1), only 3 and 1% of the groundwater samples collected from zones I and II were fit for dinking purposes with respect to As content. In the aridic southwest, zone III, all water samples contained As concentrations greater than the safe limits and thus are not suitable for drinking purposes. The presence of elevated As concentrations in groundwater are generally due to the results of natural occurrences of As in the aquifer materials. The concentration of other competitive oxyanions in waters such as phosphate, sulfate, and borate also depressed the adsorption of As on the sorption sites of aquifer materials and thereby eventually elevate the As concentration in groundwaters. In groundwater of alluvial aquifers of Punjab, released from sulfide oxidation and oxyhydroxide of iron, elevated (>10 µg L−1) concentrations of As were widespread because of high pH (>8.0) and higher concentrations of phosphate, borate, sulfate, and hydroxyl anions. It is conclusively evident that geochemical conditions, such as pH, oxidation–reduction, associated or competing ions, and evaporative environments have significant effects on As concentration in groundwater. These conditions influence how much As is dissolved or precipitated into the water and how much is bound to the aquifer materials or the solid particles in water.

Water Pollution Related to Agricultural, Industrial, and Urban Activities, and its Effects on the Food Chain: Case Studies from Punjab

In Punjab, a northwestern state of India, groundwater is depleting at a fast rate because of its excessive use and mismanagement. Contamination of groundwater and water bodies from geogenic and anthropogenic sources is also becoming a serious problem. Selenium (Se) toxicity is prevalent in 1,000 ha in Hoshiarpur and Nawanshahar districts where about 11 and 4% of groundwater samples were found unfit for drinking and irrigation purposes, respectively. About 9 and 66% groundwater samples of the Ludhiana and Bathinda districts, respectively, had fluoride concentration more than the safe limit of 1 mg l −1. In the Bathinda district, 15–44% of groundwater samples had boron more than the maximum permissible limit of 2 mg l −1. Arsenic concentration in alluvial aquifers of Punjab ranged from 4 to 688 μg l −1, and the majority of them were found unfit for human consumption considering maximum permissible limit of 10 μg l −1. Excessive applications of fertilizers, manures, and agrichemicals to field and vegetable crops lead to nitrate and phosphate leaching and contamination of groundwater and water bodies. In certain situations, nitrates exceed the dangerous level of 10 mg l −1. Industrial effluents, released without any treatment to sewage drains, contain potentially toxic elements in concentrations that are several folds higher than those in domestic sewage water and exceed the maximum permissible limits for their disposal onto agricultural lands. The mean concentrations of Pb, Cr, Cd and Ni in sewage water were, respectively, 21, 133, 700, and 2200 times higher than those in tubewell water. In one study, water of several shallow hand-pumps installed in vicinity of a sewage-water drain had 18, 80, 88, and 210 times higher concentration of Pb, Cr, Cd and Ni, respectively, than in deep tubewell water. A large number of pathogens were observed in tubewells installed for domestic water supply. Possible remediation options for such deplorable situations are discussed in this article.

Monitoring Nutrient Status of Guava Fruit Trees in Punjab, Northwest India through the Diagnostic and Recommendation Integrated System Approach

Abstract The Diagnostic and Recommendation Integrated System (DRIS) was employed for interpreting nutrient analyses of leaf tissue of guava fruit trees (Psidium guajava L.) cultivated in Punjab, northwest India. Standard reference DRIS norms were established for various nutrient ratios and used to compute DRIS indices, which assessed nutrient balance and order of limitation to yield. The DRIS evaluation and sufficiency range approach were equally effective and in agreement for diagnosing deficiencies of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), sulfur (S), manganese (Mn), zinc (Zn), and copper (Cu). The results also show that the position of leaf tissue sampled does not have a major effect on the DRIS diagnosis. Nutrient sufficiency ranges derived from DRIS norms were 1.41–1.65, 0.10–0.17, 0.51–0.97, 1.16–2.12, 0.31–0.51, 0.18–0.28% for N, P, K, Ca, magnesium (Mg), and S and were 105–153, 58–110, 15–29, and 6–16 mg Kg−1 for iron (Fe), Mn, Zn, and Cu, respectively. According to these sufficiency ranges 35, 62, 51, 75, 70, and 68% of samples were sufficient, and 4, 29, 36, 9, 10, and 22% of samples were low in N, P, K, Ca, Mg, and S, respectively. More than 50 and 2% of the guava trees selected for sampling was found to deficient in N and P, respectively. For micronutrients, 15, 6, and 7% of samples were found to be low in Mn, Zn, and Cu.

Diagnosis and recommendation integrated system for monitoring nutrient status of mango trees in submountainous area of Punjab, India

Abstract The Diagnosis and Recommendation Integrated System (DRIS) was used to identify nutrient status of mango fruit trees in Punjab, India. Standard norms established from the nutrient survey of mango fruit trees were 1.144, 0.126, 0.327, 2.587, 0.263, 0.141% for nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S), and 15, 3.5, 145, 155, and 30 mg kg−1, respectively, for zinc (Zn), copper (Cu), iron (Fe), manganese (Mn), and boron (B) in dry matter. On the basis of DRIS indices, 16, 15, 12, 17, and 16% of total samples collected during nutrients survey of mango trees were low in N, P, K, Ca, and Mg, respectively. For micronutrients, 19, 18, 12, 20, and 6% samples were inadequate in Zn, Cu, Fe, Mn, and B, respectively. DRIS‐derived sufficiency ranges from nutrient indexing survey were 0.92–1.37, 0.08–0.16, 0.21–0.44, 1.71–3.47, 0.15–0.37, and 0.09–0.19% for N, P, K, Ca, Mg, and S and 11–19, 1–6, 63–227, 87–223, and 16–44 mg kg−1 for Zn, Cu, Fe, Mn, and B, respectively.

Effect of pH on Zinc Sorption–Desorption by Soils

The objective of this study was to examine the effect of soil pH on zinc (Zn) sorption and desorption for four surface soils from the Canterbury Plains region of New Zealand. Zinc sorption by the soils, adjusted to different pH values, was measured from various initial solution Zn concentrations in the presence of 0.01 M calcium nitrate [Ca(NO3)2]. Zinc desorption isotherms were derived from the cumulative Zn desorbed (µg g−1 soil) after each of 10 desorption periods by sequentially suspending the same soil samples in fresh Zn‐free 0.01 M Ca(NO3)2. Zinc sorption and desorption varied widely with soil pH. Desorption of both native and added Zn decreased continuously with rising pH and became very low at pH values greater than 6.5. The proportion of sorbed Zn that could be desorbed back into solution decreased substantially as pH increased to more than 5.5. However, there were differences between soils regarding the extent of the hysteresis effect.

Variation in Selenium Tolerance, Accumulation, and Growth Parameters of Different Wheat Cultivars

ABSTRACT In a greenhouse experiment, wheat cultivars PDW 291, PBW 550, and TL 2908 were grown in alkaline sandy-loam soil treated with sodium selenate at 0, 2, and 4 mg selenium (Se) kg−1 soil. Selenate-treated wheat plants accumulated greater Se in roots, stems, leaves, and grains and showed growth retardation, snow-white chlorosis, decreased shoot length and chlorophyll, and reduced leaf area and produced less number of grains as compared to control plants. Maximum reduction in these parameters was observed in selenate-treated TL 2908 plants and most of the plants died before maturity with almost no grain formation with 4 mg Se kg−1 soil. Selenium accumulation resulted in decreased reducing sugar, starch, and protein contents in grains whereas total free amino acids increased significantly in all the three cultivars. Selenium accumulation in wheat showed metabolic disturbances and its accumulation in grains was beyond toxic levels, thus making it unfit for consumption.

Direct and Residual Effects of Green Manure and Fertilizer Nitrogen in a Rice-Rapeseed Production System in the Semiarid Subtropics

ABSTRACT Integrating fertilizer nitrogen (FN) with legume green manure (GM) could lead to sustainable and environmentally sound agricultural systems in subtropical-semiarid soils low in organic matter. A six-year replicated field experiment was conducted on a semiarid irrigated Tolewal sandy loam soil (Typic Ustochrepts) in northwest India. The purpose of the experiment was to evaluate the direct and residual effects and cost effectiveness of cowpea (Vigna unguiculata L.) grown as a GM-crop in situ for 45–50 days during either the hot-dry period (May-June) prior to transplanting of rice (Oryza sativa L.) or the mild-rainy season (September-October) prior to seeding of rapeseed (Brassica napus L.) in rice-rapeseed double cropping annual rotations. Rice grain yields with incorporation of 20 t GM ha−1 (GM20) ranged from 3.93 to 5.28t ha−1, which were 48 to 78% greater than the no-N control. Rice yield with 60 kg FN ha−1 (FN60) and GM20 was more than double the control yield and 24% greater than the otherwise optimum rate of 120 kg FN ha−1. Incorporation of 20t GM ha−1 to rapeseed produced 28 to 50% greater yields than the control. Combined application of GM20 with 100 kg FN ha−1 (recommended N rate in this region) further improved the yield potential of rapeseed by 16%. While FN had no residual effects, residual GM produced 9 and 35% greater yields of a succeeding crop due to the supply of N equivalent to 17 and 44 kg FN ha−1 in rice-applied and rapeseed-applied GM, respectively. Nitrogen utilization by the rice-rapeseed system was greater for GM20 than FN, as indicated by greater apparent N recovery by crops of 67% versus 51%. These results suggest that (a) green manuring in rice-rapeseed production systems is cost effective, and (b) under constrained water resources, GM produced during the mild-rainy season and applied to rapeseed is more beneficial than rice-applied GM.

DIAGNOSIS AND RECOMMENDATION INTEGRATED SYSTEM (DRIS) FOR EVALUATING NUTRIENT STATUS OF COTTON (GOSSIPIUM HIRSUTUM)

Diagnosis and Recommendation Integrated System (DRIS) approach was employed to monitor the nutrient status of cotton (Gossipium hirsutum) in southwestern districts of Punjab, North-West India. DRIS norms for macro, secondary and micro nutrients in cotton plant are developed. Considering these DRIS norms, the most limiting nutrient for cotton plant in the region is identified along with the order in which the other nutrients become limiting. The DRIS approach indicated that 11, 3, 8, 5, 2, 4, 2, 3, 6 and 2 percent of the total cotton leaf samples collected were low in nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu), respectively. Leaf tissues of cotton plant were also found to contain high to excessive content of N, P, K, Ca, Mg, S, Fe, Mn Zn and Cu in 11, 7, 15, 19, 25, 18, 66, 33, 9 and 25 percent samples, respectively. DRIS derived sufficiency concentration ranges obtained from survey of cotton fields in this region were 2.22 to 5.20% N, 0.20 to 0.47% P, 1.05 to 2.14% K, 1.66 to 2.86% Ca, 0.34 to 0.57% Mg, 0.65 to 1.11% S, 106 to 172 mg kg−1 Fe, 35 to 68 mg kg−1 Mn, 18 to 33 mg kg−1 Zn, and 5 to 8 mg kg−1 Cu. The results elucidate that DRIS technique can be used for macro, secondary and micro nutrients indexing of cotton crop irrespective of its cultivar.

Effect of Soil Chemical and Physical Properties on Sorption and Desorption Behavior of Lead in Different Soils of India

Lead (Pb) is a non-biodegradable contaminant, present in the environment, especially near lead-based industrial sites, agricultural lands, and roadside soils. Bioavailability of Pb in the soil is controlled by the sorption and desorption behavior of Pb, which are further controlled by the soil chemical and physical properties. In this study, sorption and desorption amounts of Pb in soil were compared with soil physical (sand, silt, clay content) and chemical (pH; electrical conductivity, EC; percent organic carbon, (%OC); cation exchange capacity, CEC) properties. Twenty-six surface soils (0–5cm), expected to vary in physical and chemical properties, were collected from different parts of India and were treated with known concentration of Pb solution (40 μg/L). The amount of Pb sorbed and desorbed were measured and correlated with soil properties using simple linear regressions. Sorption was significantly (p ≤ 0.05) and positively correlated with pH, and %OC; desorption was significantly (p ≤ 0.05) negatively correlated with the same two factors. Stepwise multiple regressions were performed for better correlations. Predicted sorption and desorption amounts, based on multiple regression equations, showed reasonably good fit (R2 = 0.79 and 0.83, respectively) with observed values. This regression model can be used for estimation of sorption and desorption amounts at contaminated sites.

Adsorption of Arsenate on Coarse Loamy Mixed Hyperthermic Fluventic Haplustept Soil of Punjab, Northwest India

A laboratory experiment studied the adsorption of arsenate on coarse loamy mixed hyperthermic Fluventic Haplustept soil of Punjab to serve as cheap materials for removal of arsenic (As) from water with elevated As concentration. The arsenate adsorptions onto soil and soil + iron fillings are described by a two‐region Langmuir isotherm equation; that is, the plots showed two distinct linear portions. The bonding energy and adsorption maxima for arsenate adsorption by soil increased slightly at higher equilibrium temperature of 305 K relative to 280 K in the Langmuir plot for region I but followed an appreciative decline in both parameters for region II. The addition of iron fillings enhanced the adsorption maxima of arsenic soils by 2.5‐fold because of physical adsorption and 4.44‐fold because of chemisorptions or precipitation at weak and strong As concentrations, respectively, in soil–water equilibrated systems. Thus, the results of the present investigation suggest that water withdrawn from shallow aquifer containing elevated As concentrations should be equilibrated with mixtures of soil and iron fillings for removal of As. After an equilibration period, separation of water by decantation or filtration could be used for drinking purposes for humans and domestic animals.