Fluoride in weathered rock aquifers of southern India: Managed Aquifer Recharge for mitigation

Climatic condition, geology, and geochemical processes in an area play a major role on groundwater quality. Impact of these on the fluoride content of groundwater was studied in three regions—part of Nalgonda district in Telangana, Pambar River basin, and Vaniyar River basin in Tamil Nadu, southern India, which experience semi-arid climate and are predominantly made of Precambrian rocks. High concentration of fluoride in groundwater above 4 mg/l was recorded. Human exposure dose for fluoride through groundwater was higher in Nalgonda than the other areas. With evaporation and rainfall being one of the major contributors for high fluoride apart from the weathering of fluoride rich minerals from rocks, the effect of increase in groundwater level on fluoride concentration was studied. This study reveals that groundwater in shallow environment of all three regions shows dilution effect due to rainfall recharge. Suitable managed aquifer recharge (MAR) methods can be adopted to dilute the fluoride rich groundwater in such regions which is explained with two case studies. However, in deep groundwater, increase in fluoride concentration with increase in groundwater level due to leaching of fluoride rich salts from the unsaturated zone was observed. Occurrence of fluoride above 1.5 mg/l was more in areas with deeper groundwater environment. Hence, practicing MAR in these regions will increase the fluoride content in groundwater and so physical or chemical treatment has to be adopted. This study brought out the fact that MAR cannot be practiced in all regions for dilution of ions in groundwater and that it is essential to analyze the fluctuation in groundwater level and the fluoride content before suggesting it as a suitable solution. Also, this study emphasizes that long-term monitoring of these factors is an important criterion for choosing the recharge areas.     

Assessment of groundwater pollution in West Delhi, India using geostatistical approach

The exploration, exploitation, and unscientific management of groundwater resources in the National Capital Territory (NCT) of Delhi, India have posed a serious threat of reduction in quantity and deterioration of quality. The objective of the study is to determine the groundwater quality and to assess the risk of groundwater pollution at Najafgarh, NCT of Delhi. The groundwater quality parameters were analyzed from the existing wells of the Najafgarh and the thematic maps were generated using geostatistical concepts. Ordinary kriging and indicator kriging methods were used as geostatistical approach for preparation of thematic maps of the groundwater quality parameters such as bicarbonate, calcium, chloride, electrical conductivity (EC), magnesium, nitrate, sodium, and sulphate with concentrations equal or greater than their respective groundwater pollution cutoff value. Experimental semivariogram values were fitted well in spherical model for the water quality parameters, such as bicarbonate, chloride, EC, magnesium, sodium, and sulphate and in exponential model for calcium and nitrate. The thematic maps of all the groundwater quality parameters exhibited an increasing trend of pollution from the northern and western part of the study area towards the southern and eastern part. The concentration was highest at the southernmost part of the study area but it could not reflect correctly the groundwater pollution status. The indicator kriging method is useful to assess the risk of groundwater pollution by giving the conditional probability of concentrations of different chemical parameters exceeding their cutoff values. Thus, risk assessment of groundwater pollution is useful for proper management of groundwater resources and minimizing the pollution threat.     

Biophysical and socioeconomic characterization of a water-stressed area and simulating agri-production estimates and land use planning under normal and extreme climatic events: a case study

This study aims in linking the biophysical and socioeconomic data base layers with the technical coefficients or simulation models for agri-production estimates and land use planning under normal and extreme climatic events, and exploring the resource and inputs management options in village Shikohpur, Gurgaon district located in the northwest part of India. The socioeconomic profile of Shikohpur is highly skewed with mostly small and marginal farmers. Though the areas under wheat in Shikohpur are increasing, the productivity is declining or remaining stagnant over the years. Most of the area during kharif season (June-September) remains fallow. Pearl millet based cropping systems (pearl millet-mustard and pearl millet-wheat) are predominant. Soils are mostly loamy sand to sandy loam with average of 70-80% sand content. Organic C content in soil is less than 0.3%, due to high prevailing temperature with little rainfall and also intensive agriculture followed in this region. Though the annual average seasonal rainfall in Gurgaon did not have much variation over the years, occurrence of extreme climate events has increased in the last two decades. The crop intensity is low and the water table is declining. Water and nitrogen production functions were developed for the important crops of the region, for their subsequent use in scheduling of the inputs. InfoCrop, WTGROWS and technical coefficients were used for crop planning and resource management under climate change and its variability, extreme events, limited resource availability and crop intensification. These will help in disseminating necessary agro-advisories to the farmers so that they will be able to manipulate the inputs and agronomic management practices for sustained agricultural production under normal as well as extreme climatic conditions.     

Improved photocatalytic efficiency of TiO2 by doping with tungsten and synthesizing in ionic liquid: precise kinetics-mechanism and effect of oxidizing agents

Environmental Science and Pollution Research - The degradation of nitroaromatics/toxic energetic compounds contaminated water is a major cause of concern. W-doped TiO2 nanoparticles (NPs) were...     

Ultra-structural observations on the lymphoid organs of the freshwater catfish, Clarias batrachus (Linnaeus)

Light microscopic and ultra-structural studies of the lymphoid tissues such as blood immunocytes, spleen and pronephros of the freshwater catfish, Clarias batrachus, were carried out. The peripheral blood showed nucleated erythrocytes, total leucocytic count (TLC) more than that observed in mammalian blood and leucocytes with morphological appearance similar to the mammalian white blood cells (WBCs). The spleen and pronephros showed presence of numerous lymphocytes, monocytes and nucleated red blood cells (RBCs) along with hemosiderin-containing macrophages. The morphology of lymphoid organs of the catfish has been discussed in light of the evolution of the immune system in this class of vertebrates.     

Assessment of water quality using cluster analysis in coastal region of Mumbai, India

The coastal water quality of Mumbai is deteriorating due to various point and non-point wastewater sources. Hence, it is desirable to monitor coastal water quality for various water-related activities like bathing, contact water sports, recreation, and commercial fishing. The objective of this paper is to assess the seasonal water quality on the basis of seawater standards. Based on water-quality analysis of 17 seafronts and beaches, most of the parameters were exceeding the standards. The statistical cluster analysis was carried out for evaluating impact of wastewater and sewage discharges. The hierarchical cluster analysis resulted into three clustered groups, namely less polluted, moderately polluted, and highly polluted sites with similar characteristics of water quality. Mahim was found to be worst-affected beach due to incoming organic load from the Mithi river in comparison to other seafronts and beaches. Unaccounted sources of sewage and wastewater should be identified and rerouted through sewerage system by improving collection efficiency, treatment, and proper disposal for achieving designated receiving water quality standards.     

Possible cause of inhibition of seed germination in two rice cultivars by heavy metals Pb2+ and Hg2+

Seeds of two rice cultivars (Oryza sativa) cv. PR-116 and Pant Dhan-12 subjected to heavy metal lead (Pb²⁺) and mercury (Hg²⁺) exposure showed an inhibition in germination percentage, shoot and root length, and lower fresh and dry weight after 7 days. Both Pb²⁺ and Hg²⁺ inhibited the solubilization process of starch due to reduction in α-amylase activity, which is also evident from greater starch content and reduced soluble carbohydrate content of endosperms of treated seeds of the two cultivars. Mercury was more tolerated by Pant Dhan-12 when grown under in vitro culture medium containing 2% sucrose. The inhibitory effect of Pb²⁺ on embryo growth was not only abolished but also accelerated by 2% sucrose. The inhibitory effect, however, was not significantly blocked in Hg²⁺-treated embryos grown in vitro in sucrose containing medium. Embryos did not grow normally in a medium devoid of sucrose in either case. Data indicated that Pb²⁺ inhibited germination and seedling growth by impairing the solubilization of endosperm starch without markedly affecting the embryo, while Hg²⁺ inhibited germination and seedling growth by damaging the embryo itself.     

Performance evaluation of a decentralized wastewater treatment system in India

A Decentralized Wastewater Treatment System (DEWATS) provides an economically feasible and efficient wastewater treatment solution especially in developing countries. It has an enormous potential for developing a sustainable environmental sanitation system. In this study, the treatment efficiency of eight DEWATS plants was evaluated in the state of Maharashtra, India, for their performance in terms of selected physico-chemical parameters of the wastewater. Although the efficiency of some of the plants was lower than that reported in literature, the effluent quality of all the plants was within the permissible discharge limits of the Central Pollution Control Board for all the parameters. Comprehensive assessment of Plant I was carried in terms of its technical and socio-economic aspects. Moreover, LCA tool has been utilized to evaluate the environmental impacts of the operation stage of DEWATS. The midpoint, CML 2001 (April 2015) methodology was adopted, in which 11 impact categories were considered. From the life cycle impact assessment and interpretation, the main impacts are identified as releases of COD, P-PO₄^3?, and N-NH₄⁺ to water bodies and disposal of sludge. Due to negligible energy consumption, the operation stage was found to be less damaging to the environment. It was concluded that DEWATS can be a good alternative for treating wastewater with negligible energy and chemical consumption.

     

Persistence and vertical distribution of termiticide fipronil in modified ground board test

Fipronil termiticide belongs to phenyl-pyrazole class of chemical compounds. It has broad-spectrum activity particularly against house hold pests such as cockroaches, mosquitoes, locusts, ticks, and fleas at both larval and adult stages. At high dosage it can be used to control subterranean termites in building foundations. To evaluate long term efficacy against termites the persistence and vertical distribution of fipronil was studied under natural weather conditions of Dehradun, India. Fipronil was applied at four concentrations i.e. 0.05, 0.1, 0.25 and 0.5% a.i ha⁻¹ by drenching 17 × 17 in.² plot prepared as per modified ground board test. Soil samples were collected after 22, 38 and 56 months of treatment up to the depth of 75 cm. The soil core was cut into five distinct sections i.e. 0–15, 15–30, 30–45, 45–60 and 60–75 cm depth. The residues were extracted by shaking 20 g soil sample with acetone. The acetone extract was concentrated and cleaned-up over florisil column. Fipronil residues were estimated on GLC at 220, 260, and 300°C oven, injector and detector temperature respectively. Fipronil was found to persist beyond 56 months after application. Two metabolites viz. desulfinyl and sulfide-fipronil were detected in sampling after 22 months of application that also dissipated with time. Fipronil residues were found up to 60 cm depth. The residues in deeper layers dissipate slowly with time and after 56 months of treatment residues were detected only up to 30 cm depth.     

Persistence and Dissipation Kinetics of Spiromesifen in Chili and Cotton

In a field study carried out at three different locations, the dissipation of spiromesifen on cotton and chili was studied and its DT₅₀, and DT₉₉ were estimated at each location. Spiromesifen was sprayed on chili at 96 and 192 g a.i. ha⁻¹ and cotton at 120 and 240 g a.i. ha⁻¹. Samples of chili fruits were drawn at 0, 1, 3, 5, 7, 10, 15, 21, 30 days after treatment and that of cotton seed and lint at first picking and harvest. Soil samples were drawn 30 days after treatment from 0 to 15 and 15 to 30 cm layer. Quantification of residues was done on GC–MS in Selected Ion Monitoring (SIM) mode in mass range 271–274 m/z. The LOQ of this method was found 0.033 μg g⁻¹, LOD being 0.01 μg g⁻¹. The DT₅₀ of spiromesifen when applied at recommended doses in chili fruits was found to be 2.18–2.40 days. Ninety-nine percent degradation was found to occur within 14.5–16.3 days after application. Residues of spiromesifen were not detected in cotton seed and lint samples at the first picking. In soil, no residues of spiromesifen were detectable 15 days after treatment.