Recovery of acetylcholine esterase activity of Drawida willsi (Oligochaeta) following application of three pesticides to soil

The recovery of acetylcholine esterase (AChE) activity of a dominant crop field earthworm (Drawida willsi, Michaelsen) was investigated under laboratory conditions following the application of two recommended agricultural (single and double) doses of butachlor (1.1 and 2.2 mga.i.kg(-1) dry soil), malathion (2.2 and 4.4 mga.i.kg(-1) dry soil) and carbofuran (1.1 and 2.2 mga.i.kg(-1) dry soil) to the soil. A sharp decline in the AChE activity of D. willsi was observed up to 9 and 12 days following treatment of carbofuran and malathion in both single and double doses, respectively, whereas very little inhibition was noticed in case of butachlor. D. willsi worms took 45 and 75 days to resume normal AChE activity after exposure to both single and double doses of malathion and carbofuran, respectively. Earlier [Soil Biol. Biochem. 31 (1999) 363-366], [Ph.D. thesis, Sambalpur University, Orissa, India, 2003] and [Pedobiologia (spl. issue), in press] reported that D. willsi takes 75-90 days and 90-105 days to resume normal growth and reproduction following application of both single and double agricultural doses of malathion and carbofuran, respectively. On the basis of the present and previous studies, we strongly suggest that the time gap between the first and second application of malathion, irrespective of single and double dosage, should be at least 90 days, whereas it should be at least 105 days for carbofuran. Butachlor was found to be very toxic, suppressing growth, sexual maturation and cocoon production of D. willsi at both single and double doses [Ph.D. thesis, Sambalpur University, Orissa, India, 2003]. We therefore suggest that application of organochlorine pesticides like butachlor should be avoided as far as possible to ensure maintenance of good soil health.     

Rainwater conservation and recycling by optimal size on-farm reservoir

Hydrologic and economic analysis of the on-farm reservoir (OFR) was carried out in rainfed rice–mustard cropping systems in Eastern India followed by 2 years of field experiments in 1999 and 2000. The average contribution (average of 2 years) of direct rainfall and surface runoff from the diked crop fields contributed, respectively, about 79.5 and 20.5% to the total OFR inflow. The average contribution of evaporation loss, seepage and percolation loss and supplemental irrigation from the OFR contributed, respectively, about 10.0, 31.2 and 58.8% to the total OFR outflow. There was an average increase of rice yield of 44.0% over the rainfed rice because of application of 8.4 cm supplemental irrigation from the OFR. Thus, with an application of 4.5 cm supplemental irrigation from the OFR, 15.40% increase of mustard yield was recorded in 1999. Economic analysis indicated average net profit of Rs. 700 (US$ 1 = Rupees (Rs.) 44.75 in Indian currency) from a farm area of 800 m². Average values of benefit–cost ratio, internal rate of return and pay back period of the OFR irrigation system were evaluated as 1.17, 14.8%, and 16 years, respectively. The study reveals that the OFR irrigation in small landholders is economically feasible system for rainwater harvesting and providing supplemental irrigation in rainfed farming system.     

Runoff and soil loss from steep slopes treated with low cost bioengineering measures

Soil loss and surface runoff patterns were studied in erosion plots developed on manmade steep slopes (60 percent) over three years (1997–2000) in which rainfall ranged from 1338.4 to 1429.2 mm/year. Surface runoff and soil loss was examined under three different rainfall intensity classes. Runoff was mainly controlled by the rainfall distribution pattern on the seasonal scale. The soil loss was influenced by runoff during the first year. Both soil loss and runoff were reduced due to bioengineering measures in the first year irrespective of species planted. In the third year, combined effects of growth of grasses on protected plots, soil compaction and sediment exhaustion was noticed on runoff and soil loss. This was reflected by reduction in the runoff and soil loss from untreated and treated plots. In the high intensity class, reduction in runoff in treated plots was about 50 percent in three years and reduction in soil loss ranged between 94–95 percent in all plots. Physical treatment with brushwood structures was more efficient in erosion control in the low intensity class.     

Studies on the ability of water hyacinth (Eichhornia crassipes) to bioconcentrate and biomonitor aquatic mercury

Water hyacinth (Eichhornia crassipes, Mart solms) plants were employed to assess bioconcentration and genotoxicity of aquatic mercury. Plants were exposed to water contaminated with mercuric chloride (MC) or phenyl mercuric acetate (PMA) at 0.001 to 1.0 mg litre(-1), or mercury contaminated effluent from a chloralkali plant for various periods of 4 t0 96 h. Root samples taken after 4, 8, 12, 24, 48, 72 and 96 h of exposure were analysed for bioconcentration of mercury spectrophotometrically, and the root meristems were fixed in aceto-ethanol for cytological analysis to determine the frequencies of cells with micronuclei (MNC). Ethyl methane sulfonate and tap water served as positive and negative controls, respectively. The results indicated that bioconcentration of mercury in root tissue was both time- and concentration-dependent, providing evidence that water hyacinth is a good absorbant of aquatic mercury. The frequency of root meristematic cells with MNC followed a concentration-response. The findings indicate the potential of water hyacinth plants for in situ monitoring and for mitigation of aquatic mercury pollution.     

A comparison of biochemical responses to oxidative and metal stress in seedlings of barley, Hordeum vulgare L

Biochemical responses on the bases of activities of antioxidant enzymes; peroxidase, catalase, superoxide dismutase and glutathione reductase as well as estimations of total protein, lipid peroxidation and thiols in the form of protein, non-protein, glutathione and phytochelatin measured in growing seedlings of barley, Hordeum vulgare L., from Day 2 through 8 were compared following treatment of seeds for 2 h with oxidative agents, paraquat 5 x 10(-5), 10(-4), 10(-3) M, H2O2 10(-3), 5 x 10(-3), 10(-2) M and a metal salt, CdSO4 10(-5), 10(-4), 10(-3) M. A significant induction of all antioxidant enzymes along with an increase in the levels of protein, lipid peroxidation and glutathione was noted in response to oxidative stress, CdSO4 induced significant peroxidase and catalase activities but not superoxide dismutase. In a marked contrast from oxidative stress, CdSO4 decreased glutathione reductase activity as well as glutathione levels but increased phytochelatin level. The differential biochemical responses thus underlined the crucial involvement of glutathione and phytochelatin in the oxidative and metal-induced adaptive responses, respectively.     

Monitoring and assessment of mercury pollution in the vicinity of a chloralkali plant. II Plant-availability, tissue-concentration and genotoxicity of mercury from agricultural soil contaminated with solid waste assessed in barley (Hordeum vulgare L.)

Barley (Hordeum vulgare L.) was used to assess plant-availability, tissue-concentration and genotoxicity of mercury from the solid waste deposits of a chloralkali plant. Seeds of H. vulgare, presoaked in distilled water, were allowed to germinate and grow on agricultural soil mixed with solid waste containing 2550+/-339 mg Hg kg(-1) at different proportions (0.75, 1.5, 2.5 and 5%). Plants raised from germinating seeds on uncontaminated agricultural soil served as controls. On day 7, germination counts and seedling heights were recorded. The concentration of mercury in soil, and plant tissue (dry weight) were determined at different stages of plant growth from day 7 till maturity and harvest. The availability of mercury from the soil was assessed by extracting mercury at a range of pH values (2-6) and by chemical methods. The embryonic shoots excised at 36 h of germination were subjected to cytological analysis to determine mitotic index and frequency of mitoses with chromosomal aberrations. The pollen mother cells from anthers of young M1-spikes were analysed to score meiotic aberrations. Subsequently, the pollen fertility and seed set were determined. Furthermore, M2-seedlings were analysed for chlorophyll-deficient mutations. The cytogenetic analysis revealed the effects of mercury on the mitotic and meiotic chromosomes which were significantly correlated with soil-mercury. The bioconcentration of mercury in aerial tissues decreased with the age of the plant. Roots, in particular, were found to concentrate most of the mercury taken up by the plant. At the time of harvest, the bioconcentration of mercury in straw was at a minimum. The accumulation of mercury in grain, which was significant, did not increase with the increase in concentration of mercury in soil but maintained a plateau, indicating a restriction of transport of mercury through the phloem. The unique advantage with the use of Hordeum assay is that, besides assessing the germline toxicity, the assay takes into account the possible contamination of the agricultural food-chain.     

Bioleaching of copper from pre and post thermally activated low grade chalcopyrite contained ball mill spillage

Bioleaching of a low grade chalcopyrite (ball mill spillage material) was tested for copper recovery in shake flasks. The original samples (as received) were thermally activated (600°C, 30 min) to notice the change in physico-chemical and mineralogical characteristics of the host rock and subsequently its effect on copper recovery. A mixed culture of acidophilic chemolithotrophic bacterial consortium predominantly entailing Acidithiobacillus ferrooxidans strain was used for bioleaching studies and optimization of process parameters of both original and thermally activated samples. Mineralogical characterization studies indicated the presence of chalcopyrite, pyrite in the silicate matrix of the granitic rock. Field emission scanning electron microscopy coupled with Energy dispersive spectroscopy (FESEM-EDS) and X-ray Fluorescence (XRF) analysis indicated mostly SiO₂. With pH 2, pulp density 10% w/v, inoculum 10% v/v, temperature 30°C, 150 r·min^-1, 49% copper could be recovered in 30 days from the finest particle size (-1+ 0.75 mm) of the original spillage sample. Under similar conditions 95% copper could be recovered from the thermally activated sample with the same size fraction in 10 days. The study revealed that thermal activation leads to volume expansion in the rock with the development of cracks, micro and macro pores on its surface, thereby enabling bacterial solution to penetrate more easily into the body, facilitating enhanced copper dissolution.     

A study on mountain front recharge by using integrated techniques in the hard rock aquifers of southern India

Mountain front recharge (MFR) is the contribution of mountains to recharge the aquifers in the adjacent basins. The estimation of MFR is essential to obtain a detailed investigation of recharge of the groundwater at the mountain front. This study summarises the current understanding of recharge processes by comparing daily groundwater fluctuation to daily rainfall and identifies the recharge rates. The recharge rates vary with time due to difference in water table depth and travel time. Thus to understand the MFR along the foothills of Courtallam, a total of 14 surface water, rainwater and groundwater samples were collected and measured for stable isotopes. The isotopic data were used to investigate the recharge process and to identify the elevations to recharge. The study findings also suggest that predominantly rainfall along the foothills contributes recharge to the riparian zone (basin block region), whereas foothill regions receive recharge from rainfall over mountain block.     

Impact of bottom trawling on sediment characteristics—a study along inshore waters off Veraval coast, India

The present communication is a study on the impact of bottom trawling on the sediment characteristics along Veraval coast, which is the largest trawler port of India. Experimental bottom trawling was conducted from MFV Sagarkripa at five transects of water depths 15–20 m, 21–25 m, 26–30 m, 31–35 m and 36–40 m in commercial trawling grounds. Trawling was conducted for 12 months in a span of 15 months (September 2005–November 2006) excluding the trawl ban period (June to August). The sediment texture was analysed by pipette analysis and organic matter by wet oxidation method. The variations in organic matter and sediment texture were prominent between the stations selected at different depths. The sedimentary organic matter exhibited variations with different water depths and seasons. The organic matter content decreased with depth. Experimental trawling considerably reduced the organic matter content at all depths. Continued and incessant trawling operation can cause even more drastic reductions, where organic matter (OM) content is already very small. The sand proportion showed depth-wise variation; but seasonal and trawling effect was not significant showing highest values at 36–40 m depth. The silt proportion did not exhibit significant depth-wise variation. The seasonal variation of silt was significant whereas trawling effect imparted to silt was not evident. Trawling has no significant effect on clay concentration. But seasonal variation had great influence on the clay distribution and indicated significantly high depth–season interaction. The sediment of the study area was predominant in silt proportion. It was observed that the seasonal/natural variations were more prominent masking the trawling effect on silt.