Persistence of diflubenzuron and bay sir 8514 in natural and sterile sandy loam and organic soils

Abstract

Disappearance rates of 10 ppm technical diflubenzuron (N(((4‐chloro‐phenyl)amino)carbonyl)‐2,6‐diflurobenzamide, Dimilin^®) and BAY SIR 8514 (2‐chloro‐N(((4‐trifluoromethoxyphenyl)amino)carbonyl)benzamide) applied on quartz sand to natural sandy loam and muck soils were significantly greater than for the corresponding sterilized soils, e.g. 47–51% vs. 68–87% BAY SIR 8514 and 2–12% vs. 80–87% diflubenzuron remaining at 12 wk, indicating that soil microorganisms play a major role in their degradation. Kinetic analysis of the data based on a first order dependence on the insecticide concentration showed that the rate constants for these disappearance reactions decreased with time.     

Statistical evaluation of an agricultural land suitability model

The land evaluation and site assessment (LESA) method has been used extensively in the United States to assess agricultural land suitability for different localities. Despite widespread use, LESA models rarely have been evaluated in a systematic, comprehensive manner. This article discusses development of a LESA system for Hawaii, the first statewide application of the LESA methodology. The empirical model was implemented with a computerized geographic information system (GIS). The system's efficiency, ability to discriminate among land parcels, and robustness to subjective model parameter values are evaluated with statistical analyses and map overlays of GIS data. Results show great potential to simplify the original model specification, primarily through deletion of marginal site assessment factors. System output was generally insensitive to the numeric values selected for model parameters, with exception of the ratio used to combine the land evaluation (LE) and site assessment (SA) component scores. Relative supplies of the differing land attributes measured by the two components must be considered in determining an appropriate LE:SA ratio for a given area.     

ESTIMATING TRANSMISSIVITY AND HYDRAULIC CONDUCTIVITY OF CHICOT AQUIFER FROM SPECIFIC CAPACITY DATA1

ABSTRACT: Specific capacity data obtained from Well Construction reports which are available from USGS offices, can provide useful estimates of tranamissivity (T), and hydraulic conductivity (K), of an aquifer. The Chicot Aquifer in Louisiana is one of the largest sources of fresh ground water in North America. Hydrologic data collected for the Chicot Aquifer indicate that specific capacity tests can be used in estimating local and regional values for T and K, if the Cooper-Jacob equation for transient flow is used with proper corrections for well loss and partial penetration. Where full scale pumping test data are scarce, specific capacity test data that are adequately distributed spatially can be used to map changes in T and K values and can be summarized statistically to indicate applicable regional values. A computer program called “TGUESS” which is available from International Ground Water Modeling Center, Holcomb Research Institute, was used in this study. The contour maps for T and K values are prepared for different well depth intervals to avoid wide variation of values.     

FUNDAMENTAL INVESTIGATION OF GRAVITY CURRENTS WITH VARYING DENSITY1

ABSTRACT: A one-dimensional, gradually varying, non-uniform, flow equation is developed to describe the movement of a variable density gravity current through a reservoir. A linearly decreasing underflow density function is used to investigate the effect of in-reservoir density reduction on typical gravity current flow profiles. Only two types of flow profiles are found to exist for varying density underflows: Type I profiles where the underflow asymptotically approaches a horizontal surface, and Type III profiles where the underflow vertically approaches critical depth. Type I profiles pass through a transitional depth as the underflow density approaches that of the upper layer. Results indicate that a reservoir can be segmented into four distinct spatial regions with well defined flow profile characteristics. The location of these regions allows the sketching of interfacial flow profiles along with identifying the location of transitional depth conditions. Transitional depth conditions are utilized as the logical starting point for Type I flow profile numerical computation. (KEY WORDS: density; fluid flow; reservoirs; hydraulics.)     

UNCERTAINTY ANALYSIS OF BMP EFFECTWENESS FOR CONTROLLING NITROGEN FROM URBAN NONPOINT SOURCES1

ABSTRACT: The effectiveness of urban Best Management Practices (BMPs) in achieving the No-Net-Increase Policy (NNTP), a policy designed to limit nonpoint nitrogen loading to Long Island Sound (US), is analyzed. A unit loading model is used to simulate annual nitrogen exported from the Norwalk River watershed (Connecticut) under current and future conditions. A probabilistic uncertainty analysis is used to incorporate uncertainty in nitrogen export coefficients and BMP nitrogen removal effectiveness. The inclusion of uncertainty in BMP effectiveness and nitrogen export coefficients implies that additional BMPs, or BMPs with a greater effectiveness in nitrogen removal, will be required to achieve the NNIP. Even though including uncertainty leads to an increase in BMP implementation rates or BMP effectiveness, this type of analysis provides the decision maker with a more realistic assessment of the likelihood that implementing BMPs as a management strategy will be successful. Monte Carlo simulation results indicate that applying BMPs to new urban developments alone will not be sufficient to achieve the NNIP since BMPs are not 100 percent effective in removing the increase in nitrogen caused by urbanization. BMPs must also be applied to selected existing urban areas. BMPs with a nitrogen removal effectiveness of 40–60 percent, probably the highest level of removal that can be expected over an entire watershed, must be applied to at least 75 percent of the existing urban area to achieve the NNIP This high rate of application is not likely to be achieved in urbanized watersheds in the LIS watershed; therefore, additional point source control will be necessary to achieve the NNIP     

Compliance with regulations by "swim-with-dolphins" operations in Port Phillip Bay,Victoria, Australia

Managing the activities of commercial wildlife viewing tends to involve either restricting the number of industry participants and/or regulating the activities or industry participants. We report on operator compliance with regulations regarding humans swimming with free-ranging bottlenose dolphins ( Tursiops sp.) in Port Phillip Bay, Victoria, Australia. A total of 128 commercial dolphin-swim trips was studied between September 1998 and April 2000. Four permit conditions were investigated: approach type, swim time, time in proximity of dolphins, and presence of "fetal fold" calves. Results demonstrate noncompliance by operators to all of the four permit conditions studied. Compliance with temporal conditions was poorer than with other conditions. When conducting studies on the extent to which tourism affects cetaceans, investigators should consider whether tourist operations comply with existing regulations or guidelines.     

The effective and environmental half-life of 137Cs at Coral Islands at the former US nuclear test site

The United States (US) conducted nuclear weapons testing from 1946 to 1958 at Bikini and Enewetak Atolls in the northern Marshall Islands. Based on previous detailed dose assessments for Bikini, Enewetak, Rongelap, and Utirik Atolls over a period of 28 years, cesium-137 (137Cs) at Bikini Atoll contributes about 85-89% of the total estimated dose through the terrestrial food chain as a result of uptake of 137Cs by food crops. The estimated integral 30, 50, and 70-year doses were based on the radiological decay of 137Cs (30-year half-life) and other radionuclides. However, there is a continuing inventory of 137Cs and 90Sr in the fresh water portion of the groundwater at all contaminated atolls even though the turnover rate of the fresh groundwater is about 5 years. This is evidence that a portion of the soluble fraction of 137Cs and 90Sr inventory in the soil is lost by transport to groundwater when rainfall is heavy enough to cause recharge of the lens, resulting in loss of 137Cs from the soil column and root zone of the plants. This loss is in addition to that caused by radioactive decay. The effective rate of loss was determined by two methods: (1) indirectly, from time-dependent studies of the 137Cs concentration in leaves of Pisonia grandis, Guettarda specosia, Tournefortia argentea (also called Messerschmidia), Scaevola taccada, and fruit from Pandanus and coconut trees (Cocos nucifera L.), and (2) more directly, by evaluating the 137Cs/90Sr ratios at Bikini Atoll. The mean (and its lower and upper 95% confidence limits) for effective half-life and for environmental-loss half-life (ELH) based on all the trees studied on Rongelap, Bikini, and Enewetak Atolls are 8.5 years (8.0 years, 9.8 years), and 12 years (11 years, 15 years), respectively. The ELH based on the 137Cs/90Sr ratios in soil in 1987 relative to the 137Cs/90Sr ratios at the time of deposition in 1954 is less than 17 years. The magnitude of the decrease below 17 years depends on the ELH for 90Sr that is currently unknown, but some loss of 90Sr does occur along with 137Cs. If the 15-year upper 95% confidence limit on ELH (corresponding to an effective half-life of 9.8 years) is incorporated into dose calculations projected over periods of 30, 50, or 70 years, then corresponding integral doses are 58, 46 and 41%, respectively, of those previously calculated based solely on radiological decay of 137Cs.     

A framework for assessing the sustainability of brownfield developments

In England, the development of urban brownfield sites is a significant planning policy aimed at supporting urban regeneration and protecting the countryside. Brownfield sites are required, in policy, to be developed in a sustainable way. However, determining what this means in practice is unclear. This paper presents a framework for assessing the sustainability of brownfield developments, devised to clarify the stakeholders in land reuse and establish how sustainability can be achieved on reused sites. The framework has been used in research investigating the sustainability of five brownfield developments in England. The performance of the framework in this research is assessed and its potential practical use outlined.     

METABOLIC RESPONSES OF AQUATIC BACTERIAL POPULATIONS TO SELECTED INSECTICIDES1

ABSTRACT: Indigenous bacterial populations from a fresh water reservoir were treated by adding five mg/1 Sevin or Malathion to the water at 23, 28, and 33 C. The degradation of Sevin was evidenced by the increased uptake of O₂ as measured by Warburg manometry. The principal degradation product of Sevin, 1-naphthol, appeared to stimulate metabolic activity of these populations to the same extent as the parent compound. The addition of Malathion to this system appeared, on the other hand, to suppress metabolic activity to some degree. Warburg manometry was shown to be a useful, rapid method for detecting effects of insecticides on aquatic microbial populations.