Elemental composition of aquaculture fish from West Bengal, India: nutrition versus food safety.

Aquaculture production continues to grow in West Bengal, where on average people consume 8.2 kg capita-1 of fish each year, and an extensive mosaic of aquaculture ponds has developed along the River Hugli as clay pits are repurposed. The adjacent brickworks and industry (especially tanneries) are a source of environmental pollution, with potential for bioaccumulation of potentially harmful elements (PHEs) in fish farmed in these ponds. Fish from aquaculture present an opportunity to meet food sufficiency in West Bengal; however, an investigation to assess their effectiveness for micronutrient supply balanced against food safety is required. Five ponds close to industrial brick manufacture (urban) and three from rural areas were assessed for the degree of pollution within their pond sediments and waters. Fish were also sampled from each location including a subset from the market in Kolkata to determine the concentrations of PHEs in their fish muscle tissue. Dietary intake and PHE loading were calculated for four fish species to evaluate their nutrient content with respect to recommended daily intakes for adults, e.g. calcium (Ca), potassium (K), magnesium (Mg), iron (Fe), zinc (Zn) and selenium (Se), and to establish whether the provisional maximum tolerable intakes (PMTIs) are exceeded for PHEs, e.g. aluminium (Al), arsenic (As), mercury (Hg), chromium (Cr), tin (Sn), copper (Cu) and lead (Pb). Preliminary results suggest that aquaculture is making an important contribution to nutrition, with fish being a good source of Se. However, in contrast to small wild-caught fish, aquaculture fish in the present study were poor sources of Fe, Ca and Zn. The fish also made substantial contributions (> 10%) to the PMTI of Hg and As. Therefore, there is an urgent need for ongoing monitoring and an expanded sampling programme, as well as research into approaches which might improve the nutritional quality of the farmed fish.

Impact of silver nanoparticles on benthic prokaryotes in heavy metal-contaminated estuarine sediments in a tropical environment.

Little knowledge is available about the potential impact of commercial silver nanoparticles (Ag-NPs) on estuarine microbial communities. The Hugli river estuary, India, is susceptible to heavy metals pollution through boat traffic, and there is the potential for Ag-NP exposure via effluent discharged from ongoing municipal and industrial activities located in close proximity. This study investigated the effects of commercial Ag-NPs on native microbial communities in estuarine sediments collected from five stations, using terminal restriction fragment length polymorphism (T-RFLP) technique. An increase in the number of bacteria in consortium in sediments was observed following exposure to Ag-NPs. In general microbial communities may be resistant in estuarine systems to the antimicrobial effects of commercial Ag-NPs, but key microorganisms, such as Pelobacter propionicus, disappeared following exposure to Ag-NPs. In conclusion, the T-RFLP analysis indicated that Ag-NPs have the potential to shape estuarine sediment bacterial community structure.

Arsenic speciation in polychaetes (Annelida) and sediments from the intertidal mudflat of Sundarban mangrove wetland, India.

This paper documents the concentration of total arsenic and individual arsenic species in four soft-bottom benthic polychaetes (Perenereis cultifera, Ganganereis sootai, Lumbrinereis notocirrata and Dendronereis arborifera) along with host sediments from Sundarban mangrove wetland, India. An additional six sites were considered exclusively for surface sediments for this purpose. Polychaetes were collected along with the host sediments and measured for their total arsenic content using inductively coupled plasma mass spectrometry. Arsenic concentrations in polychaete body tissues varied greatly, suggesting species-specific characteristics and inherent peculiarities in arsenic metabolism. Arsenic was generally present in polychaetes as arsenate (As(V) ranges from 0.16 to 0.50 mg kg(-1)) or arsenite (As(III) ranges from 0.10 to 0.41 mg kg(-1)) (30-53 % as inorganic As) and dimethylarsinic acid (DMA(V) <1-25 %). Arsenobetaine (AB < 16 %), and PO(4)-arsenoriboside (8-48 %) were also detected as minor constituents, whilst monomethylarsonic acid (MA(V)) was not detected in any of the polychaetes. The highest total As (14.7 mg kg(-1) dry wt) was observed in the polychaete D. arborifera collected from the vicinity of a sewage outfall in which the majority of As was present as an uncharacterised compound (10.3 mg kg(-1) dry wt) eluted prior to AB. Host sediments ranged from 2.5 to 10.4 mg kg(-1) of total As. This work supports the importance of speciation analysis of As, because of the ubiquitous occurrence of this metalloid in the environment, and its variable toxicity depending on chemical form. It is also the first work to report the composition of As species in polychaetes from the Indian Sundarban wetlands.

Trace metal bioaccumulation by soft-bottom polychaetes (Annelida) of Sundarban Mangrove Wetland, India and their potential use as contamination indicator.

Bioaccumulation of trace metals in four soft-bottom polychaetes along with the host sediments was recorded from the intertidal regions of Indian Sundarban mangrove wetland. The enrichment of Mn (maximum 730 mg kg⁻¹) and Zn (maximum 320 mg kg⁻¹) was recorded for all the polychaetes followed by Cr, Cu, As, Co, Ni and Pb, showing sharp variations between the species. However, concentrations of Sn and Hg were very low with small variations between the species. An overall high bioconcentration factor (BCF) was recorded in the capitellid worm Mastobranchus indicus. The results of the investigation indicate the possibility of developing a standard test protocol for bioaccumulation by polychaetous annelids.

Quantification and source identification of polycyclic aromatic hydrocarbons in core sediments from Sundarban mangrove wetland, India.

The distribution and potential sources of 16 polycyclic aromatic hydrocarbons (PAHs) in sediment cores (<63 microm particle size) of the Sundarban mangrove wetland, northeastern coast of Bay of Bengal (India), were investigated by gas chromatography coupled to mass spectrometry. The total concentrations of 16 PAHs ( summation operator(16)PAHs) ranged from 132 to 2938 ng/g, with a mean of 634 ng/g, and the sum of 10 out of 16 priority PAHs ( summation operator(10)PAH) varied from 123 to 2441 ng/g, with a mean of 555 ng/g, and the 5 carcinogenic PAHs (benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, and dibenz[a,h]anthracene) accounted for 68-73% of the priority PAHs. Maximum concentrations of the sediment core were obtained at subsoil depth of 12-16 cm. The prevalence of four to six aromatic ring PAHs and cross-plots of specific isomer ratios such as phenanthrene/anthracene, fluoranthene/pyrene, and methylphenanthrenes/phenanthrene suggested the predominance of wood and coal combustion sources, the atmospheric deposition, and surface runoff to be the major transport pathways. A good correlation existed between the benzo[a]pyrene level and the total PAH concentrations, making this compound a potential molecular marker for PAH pollution. Total TEQ (S) (carc) values calculated for samples varied from 6.95 ng/g TEQ (S) (carc) to 119 ng/g TEQ (S) (carc) , with an average of 59 ng/g dry weight TEQ (S) (carc) . The baseline data can be used for regular monitoring, considering the industrial and agricultural growth around this coastal environment.

Acid leachable trace metals in sediment cores from Sunderban Mangrove Wetland, India: an approach towards regular monitoring.

The paper presents the first document to identify the enrichment pattern of acid leachable trace metals (ALTMs) such as Fe, Mn, Cr, Cu, Ni, Pb, Cd, Co, Mo, Ag, As and Ba and their relationship with sediment quality parameters (pH, organic carbon, carbonates and texture) in core sediments (<63 microm particle size) from Indian Sunderban mangrove wetland, formed at the estuarine phase of the river Hugli (Ganges). Textural analysis reveals an overall predominance of mud. The results indicate that the change in pH values causes coagulation and precipitation of ALTMs. Fe and Mn have fairly close distribution patterns of enrichment in surface layers which might be ascribed to early diagnetic processes. The most prominent feature of ALTMs is the enrichment of Fe, Mn, Cr, Cu, Ni, Pb, and Ba in the surface-subsurface layers in the sediment cores, which is mainly attributed to the intense industrial and agricultural activities as well as drainage of untreated domestic sewage to this coastal region. The ALTMs also indicate their association with organic carbon and Fe-Mn oxyhydroxides. The enrichment is well--supported by the correlation, grouping and clustering of ALTMs in statistical analyses. Anthropogenic Factor values indicated ALTMs enrichment for all trace metals due to intense anthropogenic activities. Overall higher values of ALTMs in sediments in comparison to other Indian coastal regions indicate that they are mainly due to the uncontrolled anthropogenic activities in this mangrove estuarine complex. Statistical analyses suggest that five ALTMs (Cu, Pb, As, Mo, Ba) are attached to the organic particles and the clustering of elements separately also indicates that they are from external source. The result of the present study suggests the need for a regular monitoring program which will help to improve the quality of this potential wetland.

An assessment of mercury loading in core sediments of Sunderban mangrove wetland, India (a preliminary report).

This is a preliminary report on total mercury (T(Hg)) in core sediments (<63 microm particle size) of Sunderban mangrove wetland, northeastern part of the Bay of Bengal, India. Cold vapor atomic absorption spectrometry (CVAAS) was used for T(Hg) determination. The concentration varies from 9.8 to 535.1 ppb (ngg(-1)). Results revealed variations over premonsoon and postmonsoon month at different core depth, as well as in studied three sampling stations, located at the site of three rivers: Hugli River (S(1)), Matla River (S(2)) and Bidyadhari River (S(3)). Elevated concentration of T(Hg) in subsurface layer (4-8 cm) of the core at S(2) is attributed to remobilization of mercury from deeper sediment (32-36 cm). Positive correlation is present between total Hg and clay content. Based on index of geoaccumulation (I(geo)) and Effects-Range Low (ER-L) value (150 ppb) it is considered that the sediments are till now unpolluted. As a consequence, there is less chance of ecotoxicological risk to organisms living in studied sediments. Two statistical methods were applied to determine T(Hg) anomalies. Box plot method showed one extreme and three outliers in S(1) at postmonsoon season. Two extremes were found at S(2) at 4-8 and at 32-36 cm in premonsoon period. In S(3) there was no anomaly by box plot method. MAD method was more sensitive than box plot method and T(Hg) anomaly was detected at 12-16 cm in S(3) during postmonsoon season. The data reported are useful baselines for T(Hg) in Sunderban mangrove wetland, India and would be of help in future sediment quality studies.

Occurrence, distribution and possible sources of organochlorine pesticide residues in tropical coastal environment of India: an overview.

Organochlorine pesticides (OCPs) are an important potential component of chemical pollutants used extensively for agriculture and sanitation purposes in India as these are comparatively cheap and effective. These persistent organic compounds such as HCH isomers, DDT and its metabolites are the predominant chemical contaminants found along the Indian coast and thus constitute both alluring and grave areas of scientific research. Our objective in the paper is to provide a comprehensive account of the distribution of organochlorine pesticides in biotic and abiotic compartments of the Indian coastal environment, make some comments on their environmental sources, their movement through the food chain and possible ecotoxicological risk of health in biota including humans. The prevalent HCH, DDT and HCB concentrations differ markedly in eastern and western coast of India reflecting differing agricultural and other usage and their ultimate input into the coastal environment by several rivers and the bioturbation activities of macrozoobenthos (bivalve mollusks, polychaetous annelids, etc.). In several cases, the DDT levels exceeded the effects range-low (ER-L) and could thus cause acute biological impairments, in comparison with the sediment quality guidelines. Contributions of DDT metabolites (DDT, DDD and DDE residues) vary in different Indian coastal regions predominated by pp'-DDT and pp'-DDD. Measured concentrations of HCHs were lower than DDTs that might be due to higher water solubility, vapor pressure and biodegradability of the latter. HCH and DDT residues in fish in India were lower than those in the temperate countries indicating a lower accumulation in tropical fish, which might be related to rapid volatilization of this insecticide in the tropical environment. The concentrations of other chlorinated pesticides (aldrin, dieldrin, eldrin, methoxychlor, endosulfan sulphate) were lower and not generally of great concern.

Organochlorine pesticide residues in sediment cores of sunderban wetland, northeastern part of Bay of Bengal, India, and their ecotoxicological significance.

This paper presents the first comprehensive report of the organochlorine pesticide residues (OCs) such as hexachlorocyclohexane isomers (HCHs), dichlorodiphenyltrichloroethane and its six metabolites (DDTs), and hexachlorobenzene (HCB) in core sediments (<63-microm particle size) from the Indian Sunderban wetland. The pooled mean values of the mass fraction of SigmaHCHs, HCB, and SigmaDDTs in the sediments were 0.05-12, 0.05-1.4, and 0.05-11.5 ng g(-1) dry weight, respectively. The vertical distribution of pesticides reveals an erratic pattern. The concentration of four isomers of HCHs reveals a heterogenic distribution where gamma-HCH (lindane) and beta-HCH shared the dominant part. The mass fraction of HCB did not show any sharp spatial variation. The prevailing sequence of DDT metabolites indicates an active degradation of the parent compound in the sediments and/or inputs of already degraded pp'DDT to the region. Peak concentrations of HCH isomers and DDT metabolites have the potential to induce ecotoxicological impact as per the sediment quality guidelines.

Distribution and possible source of trace elements in the sediment cores of a tropical macrotidal estuary and their ecotoxicological significance.

The paper presents the first document regarding concentration, distribution and possible sources of selected trace elements (Cu, Fe, Mn, Zn, Cr, Co, Ni, Pb, Al, B and Ba) in core sediments (<63 micro particle size) from the lower stretch of Hugli (Ganges) estuary, northeast coast of Bay of Bengal by ICP-AES and EDXRF to evaluate geochemical processes influencing their distribution and possible environmental consequences. The levels of elements showed a wide range of variations in different core depths, in upper and lower intertidal zones as well as among three sampling stations. The most interesting feature of the study is the downward increase of concentrations of majority of the elements reaching overall maximum values at a depth of 20-28 cm in upper littoral zone of the site located in the extreme downstream stretch of the estuary. Values of organic carbon showed very strong positive correlations with most of the elements as revealed by correlation matrix (r) values. The interelemental relationship revealed the identical behavior of element during its transport in the estuarine environment. The overall variation in concentration can be attributed to differential discharge of untreated effluents originating from industrial, agricultural, and aquacultural sources as well as from domestic sewage along with the fishing and boating activities. The resulting compositional dataset was tested by principal component analyses and cluster analyses. Pollution load index (PLI) and index of Geoaccumulation (Igeo) revealed overall low values but the enrichment factors (EFs) for Pb were typically high for all the stations. The mean concentrations of Zn and to some extent Cu exceeded the Effects Range-Low (ER-L) values in the majority of the cases indicating that there may be some ecotoxicological risk to organisms living in sediments. The concentration of the trace elements reported in this work is useful as baselines for comparison in future sediment quality studies.