Simulated fate and transport of metolachlor in the unsaturated zone, Maryland, USA.

An unsaturated-zone transport model was used to examine the transport and fate of metolachlor applied to an agricultural site in Maryland, USA. The study site was instrumented to collect data on soil-water content, soil-water potential, ground water levels, major ions, pesticides, and nutrients from the unsaturated zone during 2002-2004. The data set was enhanced with site-specific information describing weather, soils, and agricultural practices. The Root Zone Water Quality Model was used to simulate physical, chemical, and biological processes occurring in the unsaturated zone. Model calibration to bromide tracer concentrations indicated flow occurred through the soil matrix. Simulated recharge rates were within the measured range of values. The pesticide transport model was calibrated to the intensive data collection period (2002-2004), and the calibrated model was then used to simulate the period 1984 through 2004 to examine the impact of sustained agricultural management practices on the concentrations of metolachlor and its degradates at the study site. Simulation results indicated that metolachlor degrades rapidly in the root zone but that the degradates are transported to depth in measurable quantities. Simulations indicated that degradate transport is strongly related to the duration of sustained use of metolachlor and the extent of biodegradation.

Aminobacter ciceronei sp. nov. and Aminobacter lissarensis sp. nov., isolated from various terrestrial environments.

The bacterial strains IMB-1(T) and CC495(T), which are capable of growth on methyl chloride (CH(3)Cl, chloromethane) and methyl bromide (CH(3)Br, bromomethane), were isolated from agricultural soil in California fumigated with CH(3)Br, and woodland soil in Northern Ireland, respectively. Two pesticide-/herbicide-degrading bacteria, strains ER2 and C147, were isolated from agricultural soil in Canada. Strain ER2 degrades N-methyl carbamate insecticides, and strain C147 degrades triazine herbicides widely used in agriculture. On the basis of their morphological, physiological and genotypic characteristics, these four strains are considered to represent two novel species of the genus Aminobacter, for which the names Aminobacter ciceronei sp. nov. (type strain IMB-1(T)=ATCC 202197(T)=CIP 108660(T)=CCUG 50580(T); strains ER2 and C147) and Aminobacter lissarensis sp. nov. (type strain CC495(T)=NCIMB 13798(T)=CIP 108661(T)=CCUG 50579(T)) are proposed.