Comparison of heavy metal toxicity in life stages (spermiotoxicity, egg toxicity, embryotoxicity and larval toxicity) of Hydroides elegans

A toxicity test was developed to examine the effects of heavy metal contaminants on the early life stages of the marine polychaete. We have studied the effects of metals on fertilization and early development of marine polychaete Hydroides elegans. These heavy metals have often been found in polluted ground and water near industrial discharges, and have therefore been detected from time to time in the food chain. They have been reported to alter various reproduction functions in various animals including marine populations. The toxic effect of mercury, cadmium, lead, nickel and zinc on sperm viability, fertilization, embryogenesis and larvae of H. elegans was examined. We observed that the rate of fertilization decreased when the sperm was incubated with heavy metals. Treatment of eggs with each metal did not prevent fertilization, but delayed or blocked the first mitotic divisions, and altered early embryonic development. All these effects were observed at relatively high concentrations. However, bio-accumulation in sediments and aquatic organisms have been reported. Polychaete eggs may then be in contact with very high concentrations of these heavy metals in areas where these metals are not handled or stocked properly, and then develop into abnormal embryos. In addition to bivalves and sea-urchins, polychaete embryos can provide biological criteria for seawater quality standards taking into account the sensitivity of the invertebrates and their contribution in detection of harmful chemicals with no marked effect on the species. Our results indicate that the early development of H. elegans is highly sensitive to heavy metals and this polychaete can be routinely employed as a test organism for ecotoxicity bioassays in tropical and subtropical regions.     

Economic analysis of biogas and compost projects in a palm oil mill with clean development mechanism in Malaysia

This article is a case study to compare the economic viabilities of biogas generation and compost projects in a palm oil mill in Malaysia with and without clean development mechanism (CDM). Biogas is captured from anaerobic ponds or digester tanks treating palm oil mill effluent (POME) and converted to green renewable electricity for grid connection, while compost is produced from the shredded empty fruit bunch and raw untreated POME. The both technologies were compared by considering the changes of the materials flow and energy balances. A palm oil mill with a capacity of 54?t fresh fruit bunch per hour has the potential to produce either 6.9?GWh of electricity from biogas or fertilizer equivalent to 488?t of nitrogen, 76?t of phosphorus and 1,065?t of potassium per year. The economic analysis for 10?years project term analysis indicated that CDM gave a significant impact and ensured economic viability for both projects with 25?% of internal rate of return (IRR), RM 12.39 million of net present value (NPV) and 3.5?years of payback period (PBP) for biogas project, whereas 31?% of IRR, RM 10.87 million of NPV and 2.9?years of PBP for compost project, respectively. In addition, sensitivity analysis indicated that the profitability of both projects will vary depending on the economic situation, such as electricity price which is based on the government policy, whereas compost price that depend on fertilizer market price with 43?% NPV change in 20?% range of fertilizer value.     

Post tsunami changes in soil properties of Andaman Islands, India

A post tsunami study was conducted to assess the changes in soil properties in the Andaman Island, in India. The present study reported tsunami led conversion of acid soils to saline acid soils and acid sodic soils to acid saline sodic soils in the areas South Andaman inundated during tsunami and permanently receded later and in the low-lying area submerged during high tides. Upon intense leaching acid saline soils and acid saline sodic may further develop typical characteristics of acidic soils and acidic sodic soil, respectively. The soil at Guptapara inundated almost due to tsunami with minimal pyrite oxidation has potential to develop into highly acidic soils upon drainage. The tsunami by and large has modified some depositional layer affecting the salt accumulation to a greater extent and iron to a lesser extent and least to sodicity.     

Risk assessment and chemical decontamination of an oxime carbamate insecticide (methomyl) from eggplant, Solanum melongena L.

Methomyl, S-methyl (EZ)-N-(methylcarbamoyloxy)thioacetimidate, is a systemic insecticide chosen for the management of shoot and fruit borer, Leucinodes orbonalis G. Codex Alimentarious Commission has proposed a maximum residue limit (MRL) of 0.2 mg kg^???1 of methomyl, and there is a need to validate this value on eggplant. First + first-order model can explain the nonlinear dissipation pattern of methomyl conveniently in comparison to first-order kinetics. The preharvest intervals (PHI) of 27.3 and 35.3 days as obtained from first + first-order model for single and double doses would bring down the methomyl residue below MRL in actual practice. The respective half-lives were 6.6 and 7.8 days. On the other hand, first-order model suggests methomyl dissipated with a half-life value around 5 days and proposed PHIs of 6.57 and 8.57 days for single and double doses, which was far from reality. Hence, five different decontamination agents were chosen for the decontamination of methomyl from eggplant. Safety factors such as theoretical maximum daily intake and maximum permissible intake were used to evaluate risk assessment to human health. A 3-day waiting period for the both doses, following conventional agricultural practice and processing factor could not ensure sufficient margin of safety. Subjecting the data to a processing factor of 60% could not bring the residues below the proposed MRL by Codex. Methomyl is not found appropriate and effective for application in eggplant. Either the proposed MRL needs to be revised or good agricultural practice involving methomyl for plant protection in eggplant cultivation is questioned.     

Interaction of free-living marine nematodes in the artificial mangrove environment (southeast coast of India)

Free-living marine nematode diversity was analyzed between Avicennia marina and Rhizophora mucronata mangrove covers of the Vellar Estuary (southeast coast of India). A total of 4,976 specimens of free-living marine nematodes were collected in 56 species. Comparatively, a higher species richness was obtained for A. marina (52 species) than for R. mucronata (44 species), whereas 40 species commonly existed in both mangrove covers. A higher density of nematodes was found in sediments of sandy nature, whereas there was lower total organic carbon compared to silt/clay composition; epigrowth feeders were dominant over the other feeding groups based on organic enrichment in surface sediments. Principal component analysis clearly explained the relationship between the environmental parameters of various months. Higher R values of analysis of similarities revealed significant differences in nematode assemblages between months, and it was quite evident by non-metric multidimensional scaling. Diversity indices showed higher values in the dry months. RELATE analysis explained serial changes in nematode species composition between months, and a relationship between biotic and abiotic variables was clarified using the BIO-ENV procedure. Viscosia spp., Metachromadora spp., Theristus spp., and Sphaerolaimus spp. were candidate species of A. marina leaf interaction by observation.     

Heavy metal enrichment in the seagrasses of Lakshadweep group of islands—A multivariate statistical analysis

An assessment on heavy metal (Al, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb and Zn) accumulation by seven seagrass species of Lakshadweep group of islands was carried out using multivariate statistical tools like principal component analysis (PCA) and cluster analysis (CA). Among all the metals, Mg and Al were determined in higher concentration in all the seagrasses, and their values varied with respect to different seagrass species. The concentration of the four toxic heavy metals (Cd, Pb, Zn and Cu) was found higher in all the seagrasses when compared with the background values of seagrasses from Flores Sea, Indonesia. The contamination factor of these four heavy metals ranged as Cd (1.97–12.5), Cu (0.73–4.40), Pb (2.3–8.89) and Zn (1.27–2.787). In general, the Pollution Load Index (PLI) calculated was found to be maximum for Halophila decipiens (58.2). Results revealed that Halophila decipiens is a strong accumulator of heavy metals, followed by Halodule uninervis and Halodule pinifolia, among all the tested seagrasses. Interestingly, the small-leaved seagrasses were found to be efficient in heavy metal accumulation than the large-leaved seagrass species. Thus, seagrasses can better be used for biomonitoring, and seagrasses can be used as the heavy metal sink as the biomass take usually long term to get remineralize in nature.     

Ecotoxicological effects of trace element contamination in talitrid amphipod Orchestia montagui Audouin, 1826

Environmental Science and Pollution Research - This study deals with the evaluation of trace element bioaccumulation and histological alterations in the hepatopancreas of the supralittoral amphipod...     

Remediation technologies for heavy metal contaminated groundwater

The contamination of groundwater by heavy metal, originating either from natural soil sources or from anthropogenic sources is a matter of utmost concern to the public health. Remediation of contaminated groundwater is of highest priority since billions of people all over the world use it for drinking purpose. In this paper, thirty five approaches for groundwater treatment have been reviewed and classified under three large categories viz chemical, biochemical/biological/biosorption and physico-chemical treatment processes. Comparison tables have been provided at the end of each process for a better understanding of each category. Selection of a suitable technology for contamination remediation at a particular site is one of the most challenging job due to extremely complex soil chemistry and aquifer characteristics and no thumb-rule can be suggested regarding this issue. In the past decade, iron based technologies, microbial remediation, biological sulphate reduction and various adsorbents played versatile and efficient remediation roles. Keeping the sustainability issues and environmental ethics in mind, the technologies encompassing natural chemistry, bioremediation and biosorption are recommended to be adopted in appropriate cases. In many places, two or more techniques can work synergistically for better results. Processes such as chelate extraction and chemical soil washings are advisable only for recovery of valuable metals in highly contaminated industrial sites depending on economical feasibility.     

Occurrence of heavy metals in fish: a study for impact assessment in industry prone aquatic environment around Kolkata in India

A study was conducted during November 2005-October 2006 for determining the heavy metal contamination in surface water and sediments and giving prime thrust to determine the heavy metal concentrations fish samples collected from various points of the river Ganga at different time interval. Fish samples (viz., Channa marulius and Aorichthys seengala) were analyzed for heavy metals using standard laboratory procedures by AAS method. In impact points the annual average values for Cu, Cr, Cd, Pb and Zn were 0.15, 0.04, 0.03, 0.02 and 0.29 ppm, respectively. The concentrations of heavy metals in the riverine water collected from middle point had the order Zn > Cu > Cr > Cd > Pb. The data indicated that copper was maximally accumulated in the riverine sediments whereas least annual average concentration was obtained for lead. The trend of accumulation suggested deposition was maximum for zinc and minimum for cadmium in the muscles of both fish species. Only zinc has shown some significant seasonal variation in relation to metal deposition in fish muscles (minimum in monsoon and maximum in summer). The heavy metal contamination to fish may be due to indiscriminate discharge of polluted and untreated sewage sludge to the river. The heavy metal contents in fish at some places are alarming.