The environmental fate of model chemicals and pesticides in beach sand

Sand beaches are exposed to chemicals present in coastal waters, but almost nothing is known about the environmental fate of chemicals in this ecosystem. Beach sand was exposed to several chemical probes in static microcosms to identify possible strengths and differences among beaches in their ability to degrade pollutants. Methyl p-chlorobenzoate (MCB), 2,4-dinitrotoluene (DNT), and p-nitroanisole (PNA) were degraded with half-lives of 0.86, 35, and 106 hours, respectively. MCB was hydrolyzed to the acid, DNT was partially reduced to the aminonitrotoluenes, and PNA was not appreciably degraded during the experiments. Three different beaches were compared by their ability to degrade the probes; their differences did not strongly influence degradation rates. However, one beach produced the most nitro reduction, suggesting that this location would be more capable than the others in reducing nitro-containing pollutants. Pentachloronitrobenzene (PCNB), chlorthaldimethyl, chlorpyrifos, and endosulfan have been chosen to further investigate the reductive and hydrolytic activity of beach sand. PCNB, chlorthaldimethyl, and chlorpyrifos were not appreciably degraded within 30 hours in the static microcosm, and generally losses were not different from the controls.