Chlorinated hydrocarbons in coastal lagoons of the Pacific coast of Nicaragua

A screening for persistent chlorinated hydrocarbons was carried out in Dece mber 1995 in the main coastal lagoons on the Pacific side of Nicaragua, whe re most of the country's agriculture and pesticide use has been taking plac e for decades. Results for a wide range of organochlorine pesticides in lag oon sediments show levels that generally were very low in Estero Real, Este ro 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 consi dered a baseline level for the region. Other compounds such as HCHs, BHC, e ndosulfan, heptachlor, endrin, toxaphene, and aroclors were present in conc entrations even lower, generally below 1 ng g(-1) dry weight. However, sedi ments of the Esteros Naranjo-Paso Cabcallos system at Chinandega district c ontained 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, a nd dieldrin were also present in the sediments of this lagoon system, but i n lower concentrations. The very high concentrations of toxaphene and DDTs in this lagoon are a result of the intensive use of these pesticides in cot ton growing in the district of Chinandega. Due to the long environmental ha lf-lives of these compounds (t1/2 > 10 years in temperate soils), their con centrations in lagoon sediments will likely remain high for years to come. Based on these results, the development of the new shrimp fanning activitie s in the Pacific coastal lagoons should be restricted to selected areas.