Laurel J. Standley

Organochlorine Pesticides in Stream Mayflies and Terrestrial Vegetation of Undisturbed Tropical Catchments Exposed to Long-Range Atmospheric Transport

We investigated whether biota and sediments in river catchments consisting of primary forest in northwestern Costa Rica are contaminated by atmospheric transport of organochlorine pesticides from nearby regions where their use is intense. We measured organochlorine residues in stream mayflies, as well as in the bark and leaves of trees in catchments of an undisturbed dry tropical forest west of Volcán Orosí and Cerro Cacao (i.e., western catchments), and in tree leaves and bark in partially disturbed rain forest catchments east of Cerro Orosí (i.e., eastern catchments) in a region where agricultural activity is intense. Samples were solvent extracted, purified by silica gel clean-up, and concentrated before analysis by gas chromatography/mass spectrometry. Twelve organochlorine pesticides were detected in samples, including hexachlorocyclohexanes, heptachlor epoxide, endosulfans, DDT, DDE, dieldrin, endrin, endrin aldehyde, and aldrin. Endosulfans dominated the organochlorine signature of mayflies collected in the western catchments and of leaves and bark collected from eastern catchments. Leaves and bark collected in the undisturbed western catchments contained ten-fold lower concentrations of the endosulfans than those collected from the eastern catchments. Hexachlorocyclohexane isomers were dominated by the gamma isomer and were present at comparable levels in samples of leaves and bark collected from both sides of the volcanic ridge. An exception was high residues in bark collected from one eastern catchment, suggesting a local source. Stream mayflies and terrestrial vegetation in the undisturbed dry tropical forest contained substantial quantities of organochlorine pesticides, the most likely source being long- and short-range atmospheric transport.

Maternal Transfer of Chlordane and Its Metabolites to the Eggs of a Stream Mayfly Centroptilum triangulifer.

published in Advance ACS Abstracts, September 15, 1994. Environ. Scl. Technol., Vol. 28, No. 12, 1994 2111

Impact on Water Quality of High and Low Density Applications of Spent Mushroom Substrate to Agricultural Lands

We studied the influence of spent mushroom substrate (SMS) land application on water resources. Four study sites, including mushroom farms with low or high density land applications of SMS, and two controls, an alfalfa field and a woodland, were instrumented with soilwater lysimeters and groundwater monitoring wells. Water samples were collected during the dormant season (winter) and growing season (spring). Samples were analyzed for a number of water quality parameters, including dissolved organic carbon (DOC), dissolved organic nitrogen (DON), ammonia, chloride, nitrate, nitrite, phosphate, sulfate, aluminum, cadmium, calcium, chromium, copper, iron, lead, magnesium, manganese, mercury, nickel, potassium, silicon, sodium, and zinc. Additional analyses were performed for pesticides commonly used in the cultivation of alfalfa or corn, or for insect control, including methomyl, dimethoate, hexazinone, atrazine, diuron and permethrin.All agricultural sites had elevated salt concentrations relative to the wo...