Methyl mercury in fish—a case study on various samples collected from Ganges river at West Bengal

This study investigated the presence of total mercury (Hg) and organic mercury levels in the muscle of 19 common fresh water fish species captured from river Ganges, West Bengal, India. The total mercury level found in our study may not cause any toxic effect, but the methyl mercury (MeHg) level in some freshwater fish species was surprisingly very high and toxically unacceptable. The results of mercury analysis in various specimens indicated that some fish muscles tended to accumulate high levels of Hg, and approximately 50–84% of Hg was organic mercury. A strong positive correlation between mercury levels in muscle with food habit and fish length (age) was found. Wallago attu possessed the highest amount of organic mercury in their muscle tissues, and it was 0.93 ± 0.61 μg Hg/g of wet weight. Whereas in small-sized fishes Eutropiichthys murius, Puntius sarana, Cirrhinus mrigala, Mystus vittatus or Mystus gulio, and Tilapia mossambicus, it was below the detection limit. Contamination in Catla catla (0.32 ± 0.11), Anguilla bengalensis bengalensis (0.26 ± 0.07 μg Hg/g), Chitala chitala (0.25 ± 0.18), Rita rita (0.34 ± 0.14), and Ompok pabda (0.26 ± 0.04) was also above the 0.25 μg Hg/g of wet weight, the limit set by the PFA for the maximum level for consumption of fish exposed to MeHg. Though in Labeo rohita (0.12 ± 0.03), Mastacembelus armatus (0.17 ± 0.02), Pangasius pangasius (0.12 ± 0.16), Bagarius bagarius (0.12 ± 0.01), and Clupisoma garua (0.1 ± 0.01), concentration was below the recommended level, in Lates calcarifer (0.23 ± 0.0) and Mystus aor (0.23 ± 0.1), it was threatening. Interestingly, a low concentration of Hg was found in post-monsoon samples.     

Shoreline shifting and its prediction using remote sensing and GIS techniques: a case study of Sagar Island,West Bengal (India)

The shoreline position is difficult to predict but the trend of erosion or accretion can be determined by geospatial and statistical techniques which may help in reducing the loss of property. The study aims to assess the shoreline changes and prediction in Sagar Island, a delta of the Ganges, situated in West Bengal, India. Shorelines have been delineated by using Tasseled Cap Transformation techniques from the Landsat MSS (1975), Landsat TM (1989, 1991) and Landsat ETM+ (1999, 2002, 2005, 2008, and 2011) images. The uncertainty was calculated for every year for assessing the positional error related to shoreline extraction. Total shoreline change rate/year has also been calculated and the uncertainty of total shoreline change rate was found ±3.20 m/year. In the present study, End Point Rate (EPR) and Linear Regression (LR) methods have been used for shoreline change rate calculation and prediction of shoreline. Long term (1975–2002) and short term (2002–2011) erosion and accretion rates were calculated for the study area. Sagar is the biggest island of the Sundarban region; so, it was divided into three segments in order to analyze the change on a segment basis. It was observed that the most of erosion occurred in the Segment B (south Sagar). The rate of erosion was ?7.91 and ?7.01 m/year for the periods 1975–2002 and 2002–2011 respectively. The mean shoreline change rate was high in Segment B (South Sagar) with values of ?6.46 m/year (1975–2002) but the rate was decreased into ?5.25 m/year during the later period (2002–2011). The study reveals that most of the southern part of Sagar Island is vulnerable to high rate of shoreline erosion.     

Potential toxicity of flubendiamide in Drosophila melanogaster and associated structural alterations of its compound eye

Flubendiamide, a comparatively new insecticide, is used against lepidopteran insect pests and presumed safe for non-target Drosophila melanogaster (D. melanogaster). In this study, treatment concentrations (0.5, 1, 2 5, 10, and 20 μg/ml) of flubendiamide, lower than agricultural concentrations (rice 50μg/ml or cotton 100 μg/ml), were able to inhibit acetylcholinesterase activity in third instar larvae of D. melanogaster indicating a neurotoxic potential. In addition, larvae exposed to flubendiamide also manifested increased amounts of stress protein hsp70. The larvae expressing such stress response when allowed to emerge as adults displayed severe eye structure deformities found by scanning electron microscopy. These findings indicate a toxic potential for flubendiamide in D. melanogaster.     

Lead and cadmium exposure network in children in a periurban area in India: susceptibility and health risk

Environmental Science and Pollution Research - To investigate the complex Pb-Cd exposure network in school-going children, a thorough investigation of the probable exposure means (diet, water, and...     

Leachate injection using vertical wells in bioreactor landfills

Leachate recirculation or liquid injection in municipal solid waste landfills offers economic and environmental benefits. The key objective of this study was to carry out numerical evaluation of key design variables for leachate recirculation system consisting of vertical wells. In order to achieve the objective, numerical modeling was carried out using the finite-element model HYDRUS-2D. The following design parameters were evaluated by simulating liquid pressure head on the liner and the wetted width of the waste under steady-state flow conditions: (1) hydraulic conductivities of the waste and vertical well backfill; (2) liquid injection rate and dosing frequency; (3) well diameter, screen height and screen depth; and (4) hydraulic conductivity of the leachate collection system, slope of the leachate collection system and spacing of the leachate collection pipes. The key findings of this study are as follows. The well diameter, hydraulic conductivity of the well drainage pack, and screen height and screen depth of the well have very little effect on the wetted width for a given liquid flux. The wetted width and the injection pressure for a given liquid flux decrease with the increase in the hydraulic conductivity of the waste. The pressure head on the liner increases with the decrease in the vertical distance between the bottom of the well screen and the top of leachate collection system. The liquid injection flux increases with the decrease in hydraulic conductivity of the leachate collection system. Unlike sand (k approximately 10(-4)m/s), pea gravel (k approximately 0.01 m/s) resulted in less than 0.3m pressure head on the liner for all simulations carried out in this study.     

Cardiovascular Load During Summer Work of Two Age Groups of Van-Rickshaw Pullers in West Bengal,India

Van-rickshaw is a popular mode of transport of people and merchandise in developing countries. The purpose of this study was to assess the effect of age on cardiovascular load of van-rickshaw pullers in the summer season (March-June) in real situations. In 142 participants, divided into 2 age groups (25-40 and 41-55 years), cardiovascular load was assessed on the basis of working and partial recovery heart rate (HR), predicted maximal HR, working maximal HR, average working HR, percentage of reserved HR, sum of recovery heart beats, percentage of recovery, relative and net cardiac cost, etc. Except for percentage of recovery, all parameters differed significantly between the groups and were significantly correlated with age. As this activity is very stressful, it places a heavy demand on the cardiovascular system. Therefore, age is an important factor for sustainability of the work, especially in a hot environment. Some ergonomic interventions are necessary to reduce cardiovascular load.     

Cloning and expression of α-amylase in E. coli: genesis of a superior biocatalyst for substrate-specific MFC

One of the most practical approaches for establishing a successful microbial fuel cell (MFC) is to fasten the oxidation rate of the substrate by the microorganisms to get quick paced electron transfer between microbes and electrode. A genetically modified Escherichiacoli, overexpressing α-amylase, is constructed and applied as biocatalyst in MFC using starch as substrate. The results are compared with nonrecombinant, native E.coli. The results show better performance for the MFC containing the recombinant strain demonstrated by higher power density (PD), lower resistance, and significant electrochemical activity. Maximum PD has been recorded as 279.04 mW m^?2 compared to 120.33 Mw m^?2 for the MFC operated with nonrecombinant E.coli. The impedance results also suggest the effectiveness of the recombinant strain by lowering the internal resistance by more than half order as compared to the nonrecombinant one. These results affirm that the engineered strain can be used as a superior biocatalyst in contrast to the native strain and by using the technique of genetic alteration; gene of interest can be inserted based on the substrate to be treated. So, this work gives a useful insight for accomplishing successful MFC operation with the use of bacterial stains engineered at the molecular level.     

Effect of acute exposure of acephate on hemocyte abundance in a non-target victim Drosophila melanogaster

Organophosphate insecticide acephate was tested to investigate effects on hemocyte abundance in a non-target dipteran insect Drosophila melanogaster. For this purpose, third-instar larvae were fed on four graded concentrations (2, 4, 6, or 8 μg/ml) acephate for a period of 12 and 24 hr (acute treatment). Control groups were simultaneously maintained for comparison. Relative proportions of plasmatocytes in hemolymph smear were found to fall with increasing concentrations of the test chemical. Similar decreasing trend in population of lamellocytes was also noted after 12 and 24 hr chemical exposure. In contrast to plasmatocytes and lamellocytes, crystal cell number was found to rise with increasing pesticide concentration. Several factors like oxidative stress, apoptosis induction, and mitotic failure might be the cause of reduced plasmatocyte and lamellocyte count. The elevated number of crystal cells in hemolymph smears is directly indicative of high melanin synthesis that assists larvae to combat chemical stress, since melanin is well known for its potential to minimize physical, chemical, and pathogenic stress.     

Structural alterations in compound eye of Drosophila melanogaster in response to sodium fluoride treatment

Sodium fluoride, used as a pesticide in agriculture, is also an ingredient of toothpastes which help to fight dental problems. In this study, Drosophila melanogaster, a non-target organism, is used to explore morphological changes in the adult compound eye as a function of exposure to fluoride at 20, 40, 80, 100 and 150 mg L^?1, using scanning electron microscopy. The experimental concentrations were much lower than the ones used in the studies of the British Association of Community Dentistry. Distinct morphological alterations in the eye of the treated insects revealed ommatidial ridges and disoriented mechanosensory bristles which were most prominent in the 40 and 80 mg L^?1 treatment groups. Since humans and Drosophila share homology in many genes that are involved in developmental pathways, the present findings raise concern on the use of sodium fluoride as a pesticide.     

Relationship of methyl mercury accumulation with lipid and weight in two river cat fish species, Wallagoo attu and Mystus aor, from West Bengal, India

This study focuses on mercury (Hg) bioaccumulation in Indian cat fish, Wallagoo attu and Mystus aor, from different rivers. Methyl mercury (MeHg) concentrations were determined in muscle tissue of two different parts, ventral and dorsal part, of each species and the levels of organic mercury were co-related with lipid content of each part. The MeHg concentrations increased in a linear fashion with both weight and age for these river species. The average concentration of MeHg was found to be 0.93?±?0.60 and 1.26?±?0.62 μg Hg g^?1 (expressed in wet weight basis) for ventral and dorsal parts, respectively in W. attu and this was above the 0.25 μg Hg g^?1 of wet weight, the limit set by the Prevention of Food Adulteration Act for the maximum level for consumption of fish exposed to mercury pollution. In M. Aor the concentration of MeHg was not above the standard limit but threatening, it was 0.22?±?0.07 and 0.23?±?0.08 μg Hg g^?1 (expressed in wet weight basis) in dorsal and ventral parts, respectively.