Land application of organic wastes such as animal manure, municipal wastes, and sewage sludge could alter the soil physical properties. Repeated substantial applications of waste increase the soil organic matter percentage. The available data on effects of waste applications on soil physical properties such as bulk density, water holding capacity at both field capacity and wilting point, and saturated hydraulic conductivity were summarized. Based on data from 12 different sources, 21 soil types, 7 waste types, and 8 crop types, a linear regression analysis of observed increases in soil organic C as a result of waste applications on percent reduction in bulk density indicated a highly significant relationship (r* = 0.69**). The results of an exponential multiple regression analysis of percentage sand and increase in organic C percentage on the percent increase in water holding capacity indicated that approximately 80% of the observed variations in percent increases in water holding capacity, at both field capacity and wilting point, could be attributed to variations in soil texture and soil organic C increases. The data on hydraulic conductivity as well as on infiltration rates are very limited and are not sufficient for quantitative analyses. The limitations of the available data were discussed in terms of identifying future research needs.

Several biogeochemical processes that regulate the removal of nutrients in wetlands are affected by temperature, thus influencing the overall treatment efficiency. In this paper, the effects of temperature on carbon, nitrogen, and phosphorus cycling processes in treatment wetlands and their implications to water quality are discussed. Many environmental factors display annual cycles that mediate whole system performance. Water temperature is one of the important cyclic stimuli, but inlet flow rates and concentrations, and several features of the annual biogeochemical cycle, also can contribute to the observed patterns of nutrient and pollutant removal. Atmospheric influences, including rain, evapotranspiration, and water reaeration, also follow seasonal patterns. Processes regulating storages in wetlands are active throughout the year and can act as seasonal reservoirs of nutrients, carbon, and pollutants.Many individual wetland processes, such as microbially mediated reactions, are affected by temperature. Response was much greater to changes at the lower end of the temperature scale (Ͻ 15°C) than at the optimal range (20 to 35°C). Processes regulating organic matter decomposition are affected by temperature. Similarly, all nitrogen cycling reactions (mineralization, nitrification, and denitrification) are affected by temperature. The temperature coefficient () varied from 1.05 to 1.37 for carbon and nitrogen cycling processes during isolated conditions. Phosphorus sorption reactions are least affected by temperature, with values of 1.03 to 1.12. Physical processes involved in the removal of particulate carbon, nitrogen, and phosphorus are not affected much by temperature.In contrast, observed wetland removals may have different temperature dependence. Design models are oversimplified because of limitations of data for calibration. The result of complex system behavior and the simple model is the need to interpret whole ecosystem data to determine temperature coefficients. Temperature seems to have minimal effect on biochemical oxygen demand (0.900 ϽϽ1.015) and phosphorus (0.995 ϽϽ1.020) removal, and more significant effect on nitrogen removal (0.988 ϽϽ1.16). In colder climates, there may be seasonal slowdown of treatment, which can decrease the overall treatment efficiency of constructed wetlands. Water Environ. Res., 73, 543 (2001).

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In a critical review of pathogen and indicator-organism transformations and transport from land areas receiving organic wastes, microbial die-off was described assuming first-order kinetics. First-order die-off rate constants (k) were calculated from the literature data for various pathogens and indicator organisms. For indicator organisms average die-off.rates were 1.14 day-' (0.08-9.1) for fecal coliforms, and 0.41 day-' (0.05-3.87 day-') for fecal streptococci. For pathogens, the average die-off rates were 1.33 day-' (0.21-6.93) for Salmonella, 0.68 day-' (0.62-0.74 day-~) for Shigella sp., and 1.45 day-' (0.04-3.69 day-') for viruses, respectively. Die-off rates increased approximately two times with a 10°C rise in temperature ($-30°C). Microbial die-off increased with decrease in soil moisture and was minimum in a pH range of 6-7. Correction factors were presented to adjust the k values for the changes in temperature, moisture, and pH. Retention of pathogens and indicator organisms by soil particles was described as. suming a linear isotherm. Retention of microorganisms increased with an increase in clay content of the soil. Major transport processes reviewed were leaching and surface runoff for land areas receiving animal wastes, and pastures and rangeland watersheds where animals distribute waste directly on the land. Some of the important research needs identified include (i) mechanisms involved in the retention of bacteria and viruses by the soil; (ii) measurement of retention coefficients for some important pathogens and indicator organisms, as a function of physico-chemical properties of soil; (iii) processes involved in the transport of bacteria and viruses ' Paper no. 6448 of the Journal Series of the North Carolina Agric. Res. Serv., Raleigh.

Total P is increasing over time in the waters of Lake Okeechobee, Florida, but the concentrations do not correlate with external loads. The objectives of this study were to determine: (i) the P flux from various sediment types within the lake, (ii) the factors that control direction and magnitude of P flux, and (iii) the amount of P associated with various inorganic P phases within the sediment. Phosphorus flux was measured from intact sediment cores taken from eight sites that represent major sediment types and major inflows of Lake Okeechobee at four time periods in 1989–1990. At the same location‐times, dissolved reactive phosphorus (DRP) in porewater was determined using porewater equilibrators and/or sediment cores. Results indicate that P flux from sediments is very sensitive to changes in O2 status of the overlying water, with anaerobic conditions promoting large P fluxes. Despite steep porewater DRP gradients in sediments (varying from 0.1 mg P L−1 at the sediment/water interface to more than 1 mg P L−1 at lower depths), P flux was not regulated by such gradients. Such lack of dependence of P flux on DRP gradients highlights the role redox reactions (involving Fe) can play in P chemistry in the top few centimeters of the sediment. Internal P loads (i.e., flux from bottom sediments) were found to be approximately equivalent to external P loads (≈1 mg P m−2 d−1).