Biogeochemistry of mercury and methylmercury in sediment cores from Sundarban mangrove wetland, India—a UNESCO World Heritage Site

This study was performed to elucidate the distribution, concentration trend and possible sources of total mercury (Hg(T)) and methylmercury (MeHg) in sediment cores (<63 μm particle size; n?=?75) of Sundarban mangrove wetland, northeastern part of the Bay of Bengal, India. Total mercury was determined by atomic absorption spectrometry (AAS) in a Leco AMA 254 instrument and MeHg by gas chromatography-atomic fluorescence spectrometry (GC-AFS). A wide range of variation in Hg(T) (0.032-0.196 μg g(-1) dry wt.) as well as MeHg (0.04-0.13 ng g(-1) dry wt.) concentrations revealed a slight local contamination. The prevalent low Hg(T) levels in sediments could be explained by sediment transport by the tidal Hugli (Ganges) River that would dilute the Hg(T) values via sediment mixing processes. A broader variation of MeHg proportions (%) were also observed in samples suggesting that other environmental variables such as organic carbon and microbial activity may play a major role in the methylation process. An overall elevated concentration of Hg(T) in surface layers (0-4 cm) of the core is due to remobilization of mercury from deeper sediments. Based on the index of geoaccumulation (I (geo)) and low effects-range (ER-L) values, it is considered that the sediment is less polluted by Hg(T) and there is less ecotoxicological risk. The paper provides the first information of MeHg in sediments from this wetland environment and the authors strongly recommend further examination of Hg(T) fluxes for the development of a detailed coastal MeHg model. This could provide more refine estimates of a total flux into the water column.     

Accumulation and risks of polycyclic aromatic hydrocarbons and trace metals in tropical urban soils

The study deals with the combined contribution of polycyclic aromatic hydrocarbons (PAHs) and metals to health risk in Delhi soils. Surface soils (0–5 cm) collected from three different land-use regions (industrial, flood-plain and a reference site) in Delhi, India over a period of 1 year were characterized with respect to 16 US Environmental Protection Agency priority PAHs and five trace metals (Zn, Fe, Ni, Cr and Cd). Mean annual ∑₁₆PAH concentrations at the industrial and flood-plain sites (10,893.2?±?2826.4 and 3075.4?±?948.7 μg/kg, respectively) were ~15 and ~4 times, respectively, higher than reference levels. Significant spatial and seasonal variations were observed for PAHs. Toxicity potentials of industrial and flood-plain soils were ~88 and ~8 times higher than reference levels. Trace metal concentrations in soils also showed marked dependencies on nearness to sources and seasonal effects. Correlation analysis, PAH diagnostic ratios and principal component analysis (PCA) led to the identification of sources such as coal and wood combustion, vehicular and industrial emissions, and atmospheric transport. Metal enrichment in soil and the degree of soil contamination were investigated using enrichment factors and index of geoaccumulation, respectively. Health risk assessment (incremental lifetime cancer risk and hazard index) showed that floodplain soils have potential high risk due to PAHs while industrial soils have potential risks due to both PAHs and Cr.     

Reductive Dechlorination of Tetrachloroethylene by Soil Sulfate-Reducing Microbes under Various Electron Donor Conditions

Biotransformation of tetrachloroethylene (PCE) by soil sulfate-reducing bacteria was investigated using acetate, lactate and methanol as electron donors. Results show that the effectiveness of biotransformation of PCE by soil sulfate-reducing bacterial is dependent upon the type of electron donor used.     

Analysis of the small-scale spatial patterns of free-living marine nematodes from tidal flats in the East Frisian Wadden Sea

Serial samples with a multiple corer were taken in order to understand the small-scale aggregation patterns in the nematode community. A total of 77 species was found in the sample. Fifteen dominant nematode species were examined by means of a dispersion analysis. Only one species (Metachromadora scotlandica) may be considered randomly distributed. A variogram analysis gave no proof of aggregation in that species, but all the other (aggregated) species displayed different spatial patterns: (1) a maximum/aggregation at the sample's margin, (2) two maxima/aggregations in the centre of the sample, (3) aggregation of individuals distributed at random over the entire sample (Metalinhomoeus typicus) and (4) aggregation of individuals distributed at random only in the centre of the sample (Paralinhomoeus ilenensis). These results allow the prognosis that distribution patterns are repetitive in five species (Microlaimus conothelis, M. marinus, Odontophora rectangula, Oncholaimellus calvadosicus, Viscosia rustica). Finally, by means of MDS-ordination (based on cosine similarity) two nematode associations were distinguished: one group represented by diatom-feeders (sensu lato), the other one comprised of DOM-users (sensu lato). Received: 13 May 1998 / Accepted: 15 January 1999     

Use of Ammophila arenaria for Dune Stabilization in South Africa and Its Current Distribution—Perceptions and Problems

Ammophila arenaria (marram or European beach grass) for dune stabilization in South Africa in the past and present, its present distribution in South Africa, and the perceptions of coastal management agencies and the public about its further use. The planting of A. arenaria became the most important means of dune stabilization, by human intervention, along the South African Cape coast in this century. Its modern distribution from the semiarid west coast to the subtropical shores of the Eastern Cape extends through various climatic zones. Although historical data are missing for some areas, there is no indication of its unaided spread. A. arenaria occurs at most sites because of its prior planting. The South African climate appears to affect its vigor. However, concern about the use of the alien grass has been raised since it has proved to be a highly invasive species in other parts of the world, particularly along the North American west coast and in Tasmania. While the CSIR (Council of Scientific and Industrial Research) promotes its use, CNC (Cape Nature Conservation) follows a policy that restricts the use of any alien plant, including A. arenaria, and requests further research on its invasive properties. Although a questionnaire survey shows that stabilization sites featuring large areas of A. arenaria are accepted by the South African public, current coastal management practices need to be analyzed critically. A thorough investigation of the potential invasiveness of A. arenaria on South African coastal dunes will be essential and shed new light on the American A. arenaria problem.     

Sublethal impairment of respiratory control in plaice (Pleuronectes platessa) larvae induced by UV-B radiation, determined using a novel biocybernetical approach

The increasing amount of UV-B radiation (280 to 320 nm) reaching the earth's surface could endanger transparent fish and zooplankton in upper water layers. Previous studies on marine fish eggs and larvae focused mainly on the effects of high, lethal doses of ultraviolet irradiation. Now a sensitive test for accumulated, sublethal impairments of physiological performance has been established. In developing fish larvae (Pleuronectes platessa L.), the respiratory control responses to hypoxia were evaluated by combining a biocybernetical approach and a novel optical test system. Before testing respiratory control behavior, the larvae were irradiated with light containing UV-B (test individuals) or free from it (control individuals). Differences in the physiological reactions of these larvae were detected by biocybernetical analysis (linear systems analysis) of respiratory control. The analysis was based on the evaluation of changes in ventilatory rate caused by sinusoidally modulated partial pressures of ambient oxygen. The ventilatory movements of the larvae were recorded, analyzed and evaluated by video microscopy and digital image processing. After several days of irradiation with moderate UV-B doses or intensities (8.6 kJ m⁻² d⁻¹, corresponding to an irradiance of 0.24 W m⁻² for 10 h), sublethal impairments of respiratory control could be detected in plaice larvae by this method; both the linearity of respiratory control itself and the parameters of linear control behavior were affected by UV-B. Concerning environmental implications, the results must still be interpreted cautiously, because natural irradiation conditions are more complex than the artificial regimen. Our biocybernetical approach will be useful for further studies on sublethal impairments of physiological functions caused by UV-B in fish and other transparent marine or limnic animal groups. In addition, the method could be used to test the sublethal impact of chemical contaminants. Received: 4 November 1997 / Accepted: 6 May 1998     

Phthalates and their metabolites in breast milk--results from the Bavarian Monitoring of Breast Milk (BAMBI)

Phthalates have long been used as plasticizers to soften plastic products and, thus, are ubiquitous in modern life. As part of the Bavarian Monitoring of Breast Milk (BAMBI), we aimed to characterize the exposure of infants to phthalates in Germany. Overall, 15 phthalates, including di-2-ethylhexyl phthalate (DEHP), di-n-butyl phthalate (DnBP), di-isobutyl phthalate (DiBP), di-isononyl phthalate (DiNP), three primary metabolites of DEHP [mono-(2-ethylhexyl) phthalate (MEHP), mono-isobutyl phthalate (MiBP), and mono-n-butyl phthalate (MnBP)], and two secondary metabolites of DEHP were analyzed in 78 breast milk samples. We found median concentrations of 3.9 ng/g for DEHP, 0.8 ng/g for DnBP, and 1.2 ng/g for DiBP, while other parent phthalates were found in only some or none of the samples at levels above the limit of quantitation. In infant formula (n=4) we observed mean values of 19.7 ng/g (DEHP), 3.8 ng/g (DnBP), and 3.6 ng/g (DiBP). For MEHP, MiBP, and MnBP, the median values in breast milk were 2.3 μg/l, 11.8 μg/l, and 2.1 μg/l, respectively. The secondary metabolites were not detected in any samples. Using median and 95th percentile values, we estimated an "average" and "high" daily intake for an exclusively breast-fed infant of 0.6 μg/kg body weight (b.w.) and 2.1 μg/kg b.w., respectively, for DEHP, 0.1 μg/kg b.w. and 0.5 μg/kg b.w. for DnBP, and 0.2 μg/kg b.w. and 0.7 μg/kg b.w. for DiBP. For DiNP, intake values were 3.2 μg/kg b.w. and 6.4 μg/kg b.w., respectively, if all values in milk were set half of the detection limit or the detection limit. The above-mentioned "average" and "high" intake values corresponded to only about 2% to 7%, respectively, of the recommended tolerable daily intake. Thus, it is not likely that an infant's exposure to phthalates from breast milk poses any significant health risk. Nevertheless, other sources of phthalates in this vulnerable phase have to be considered. Moreover, it should be noted that for infants nourished with formula, phthalate intake is of the same magnitude or slightly higher (DEHP) than for exclusively breast-fed infants.     

Soil to leaf transfer factor for the radionuclides ²²⁶Ra, ⁴⁰K, ¹³⁷Cs and ⁹⁰Sr at Kaiga region, India

Transfer factors are the most important parameters required for mathematical modeling used for environmental impact assessment of radioactive contamination in the environment. In this paper soil to leaf transfer factor for the radionuclides ⁴⁰K, ²²⁶Ra, ¹³⁷Cs and ⁹⁰Sr is estimated for Kaiga region in Karnataka state, India. Among the plants in which study is carried out, ²²⁶Ra, ⁴⁰K, ¹³⁷Cs and ⁹⁰Sr activity in leaves of herbaceous plants is higher than that of tree leaves. Soil to leaf transfer factor for ²²⁶Ra, ⁴⁰K, ¹³⁷Cs and ⁹⁰Sr was found to be in the range of 0.03-0.65, 0.32-8.04, 0.05-3.03 and 0.42-2.67 respectively.     

Bisphenol A content in fish caught in two different sites of the Tyrrhenian Sea (Italy)

Bisphenol A (BPA) is an endocrine disruptor (ED) that is abundant in the environment because of its extensive use in human-manufactured products. In this study, the BPA concentration was measured in the muscle and liver of five edible fish, characterized by different habitat and habits, caught in two different sites of the Tyrrhenian Sea (Italy). Our results show that: (i) fish livers are about 2.5 times more polluted than muscle; (ii) fish caught in the Gulf of Naples are more polluted than those from the Latium coasts, ranging from 1.2-fold more for White Bream to 6.6-fold for Grey Mullet; and (iii) the percentages of fish found to be BPA-polluted in the Gulf of Naples ranged from 73% (for Bass) to 90% (for Mullet), while the Latium fish range from 60% (for Bass) to 90% (for Mullet). These data indicate that consumers of fish caught in the Gulf of Naples are at a greater risk for BPA-induced endocrine pathologies compared to those who consume fish caught along the Latium coasts.