Tuesday, November 6, 2007 - 1:45 PM
230-11

Enzyme Activities of Soils Receiving Reclaimed Wastewater Irrigation.

Laosheng Wu, University of California, Riverside, 2208 Geology Building, Department of Environmental Sciences, Riverside, CA 92521, Andrew Chang, University of California, UC Center for Water Resources, Univ. Of California, Riverside, CA 92521, and Weiping Chen, Department of Environmental Sciences, University of California, Riverside, Riverside, CA 92521.

Studies have shown that physical and chemical properties of soils may be significantly changed when they are subjected to long-term wastewater irrigation. It remains uncertain, however, whether or not wastewater may affect the biochemical transformations involved in the cycling of nutrients in soils. Soil enzymes affect the nutrient cycling by catalyzing various transformations of mineral compounds and decomposition of organic debris in soils. In this study, 17 soil enzymes including those associated with the N, C, P, and S cycles and two oxidoreductases (catalases and dehydrogenase) were assayed in soils obtained from five long-term wastewater irrigation sites in southern California. The activities of all 17 soil enzymes assayed were increased by wastewater irrigation. The activities of enzymes involved in N cycling (protease, L-asparaginase, L-glutaminase, amidase, urease, and histidine NH3-lyase), C cycling (cellulose, a-glucosidase, a- galactosudase and invertase) and P cycling (acid and alkaline phosphatase, phosphodiesterase, and inorganic pyrophosphatase) were enhanced by an overall average of 2.22-, 3.12-, and 3.01-fold, respectively. Activities of other soil enzymes such as sulfatase (arylsulfatase) and oxidoreductases (catalases and dehydrogenase) were increased by 2.16- and 4.49-fold, respectively. Overall the activities of the 17 soil enzymes assayed in the wastewater-irrigated sites were 2.88 times greater in comparison to their controls.

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