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Polychlorinated biphenyl compounds (PCBs) were analyzed in sediments and clams’ soft tissues from sampling sites in the Mekong River delta from the border with Cambodia to the coast of South China Sea. Concentrations of 13 individual PCB congeners are reported. Median concentration of ΣPCB congeners was 0.279 ng g−1 dry weight (range 0.106–2.016 ng g−1 dry weight) in sediments, and 5.20 ng g−1 dry weight (range 1.89–19.37 ng g−1) in clams. Distribution and bioaccumulation of PCBs in the delta are discussed. It is concluded that in the Mekong River delta PCB concentrations were generally lower than in other regions of Vietnam and their likely sources have been waste discharges from repair workshops and other facilities in the delta cities. [ABSTRACT FROM AUTHOR]

A mussel tissue homogenate, labelled IAEA-142, was used as an intercomparison sample for the analyses of organochlorine pesticides, polychlorinated biphenyls (PCBs) and petroleum hydrocarbons. The sample material was analysed by 95 laboratories in 54 countries, which represents the widest participation ever obtained in an interlaboratory comparison exercise for synthetic organic contaminants in marine samples. The results reported by the laboratories show that there are still some difficulties with the accurate determination of organic contaminants such as pesticides and polycyclic aromatic hydrocarbons (PAHs). More consistent interlaboratory results were obtained for PCB congeners. Nevertheless, in this exercise many laboratories reported results in close agreement and, after statistical screening of the data, consensus values were obtained for the concentration of several analytes in this sample. These results allowed for assigning reference concentration values for these analytes and, thus, the sample IAEA-142 can be used as a reference material for quality control of data in the determination of chlorinated compounds and petroleum hydrocarbons in biological samples. Furthermore, with respect to the matrix type and contaminants certified this sample is unique in the collection of reference materials available today. [ABSTRACT FROM AUTHOR]

Analyses of pesticide residues in sediments, water and biota of the Altata - Ensenada del Pabellon coastal lagoon system in Sinaloa, Mexico, showed the presence of organochlorine and organophosphorus compounds. For all the compounds analysed, concentrations in sediments were higher near the points of water discharge from ponds and drainage from the agricultural area. Among the organochlorines, total DDTs displayed the largest sedimentary reservoir, followed by total endosulfans and chlorpyrifos. In sediments, as well as in biota, pp'-DDT concentrations were lower than those of DDT metabolites, which confirms the reduction in the previous massive use of this compound in agriculture. Endosulfan is currently used in the region and endosulfan residues in lagoon sediments attained levels considered to be toxic to meiofauna, therefore constituting an ecological risk to lagoon ecosystems. There was a large sedimentary reservoir of chlorpyrifos but its ecotoxicological risk is difficult to assess due to lack of adequate comparative data. Nevertheless, concentrations of chlorpyrifos which approach acute toxic levels for shrimp were recorded in lagoon water. This suggests that drainage from agricultural fields during high runoff may, on occasion, cause mass mortality of shrimp and fish. Organophosphorus pesticides are widely regarded to degrade very rapidly in aquatic systems. Experimental research performed with 14C-labelled chlorpyrifos and parathion has shown that they may be stabilised for relatively long periods of time through sediment-water partitioning. This extension of their environmental half-lives increases their potential for impacting on coastal ecosystems. Since organophosphorus pesticides are highly toxic for aquatic organisms at concentrations generally lower than organochlorines, their presence in the lagoon water and sediment is a matter for much concern. The increased use of tropical coastal lagoons for shrimp and fish farming requires the implementation of environmental management practices to protect these ecosystems from the impact of agricultural activities. Environmental management aims to preserve the ecosystem integrity of these coastal lagoons and, through improving the water quality, to allow the development of aquaculture and reduce human exposure to pesticide residues in food. [ABSTRACT FROM AUTHOR]

A world-wide interlaboratory comparison exercise was organised using a lagoon sediment as sample material (IAEA-417) for the analyses of chlorinated pesticides, PCB congeners and petroleum hydrocarbons. The sample material was analysed by 97 laboratories from 46 countries, representing a rather wide distribution for such an interlaboratory comparison exercise. Whereas quite variable results were reported for most chlorinated pesticides, more consistent interlaboratory results were obtained for PCB congeners and polycyclic aromatic hydrocarbons (PAHs). Nevertheless, many laboratories reported results in sufficiently close agreement that after statistical screening of the data, consensus values were obtained for the concentration of several analytes in this sediment sample. The results allow reference concentration values to be assigned for several analytes. Thus, the sediment sample IAEA-417 can be used as a reference material for quality control of data in the determination of chlorinated compounds and petroleum hydrocarbons in moderately polluted sediments [ABSTRACT FROM AUTHOR]

A screening for persistent chlorinated hydrocarbons was carried out in December 1995 in the main coastal lagoons on the Pacific side of Nicaragua, where most of the country's agriculture and pesticide use has been taking place for decades. Results for a wide range of organochlorine pesticides in lagoon sediments show levels that generally were very low in Estero Real, Estero Padre Ramos, and estuary of San Juan del Sur. For example, total DDTs in these lagoons averaged 4.5 +/- 3.4 ng g-1 dry weight, which may be considered a baseline level for the region. Other compounds such as HCHs, BHC, endosulfan, heptachlor, endrin, toxaphene, and aroclors were present in concentrations even lower, generally below 1 ng g-1 dry weight. However, sediments of the Esteros Naranjo-Paso Caballos system at Chinandega district contained pesticide residues in much higher levels, attaining maximum values of 1,420 ng g-1 and 270 ng g-1 dry weight, respectively, for toxaphene and total DDTs. Other compounds such as aroclors, chlordane, endosulfan, and dieldrin were also present in the sediments of this lagoon system, but in lower concentrations. The very high concentrations of toxaphene and DDTs in this lagoon are a result of the intensive use of these pesticides in cotton growing in the district of Chinandega. Due to the long environmental half-lives of these compounds (t1/2 > 10 years in temperate soils), their concentrations in lagoon sediments will likely remain high for years to come. Based on these results, the development of the new shrimp farming activities in the Pacific coastal lagoons should be restricted to selected areas. [ABSTRACT FROM AUTHOR]