Simulation of pesticide runoff at Rosemaund Farm (UK) using the SoilFug model

A validation exercise of the SoilFug model using field runoff data from Rosemaund Farm (UK) is described. A comparison has been made of modelled and measured concentrations of several pesticides in surface water and soil during and after specific rain events following application. The field experiments were designed to obtain data on rainfall, outflows of water, pesticide application rates and concentrations in soil and water. The results were satisfactory for the undissociated pesticides (atrazine, carbofuran, dimethoate, isoproturon, lindane, simazine and trifluralin), whose concentrations in water were mostly predicted within an order of magnitude of measured data. The results for the dissociated pesticides (dichlorprop, MCPA, mecoprop) were less satisfactory, giving generally much higher predicted concentrations in water. The use of the SoilFug model is suggested for the calculation of predicted environmental concentrations (PECs) in water, since it generally produces acceptable results from a relatively small set of input data, most of which is generally available.     

Buffer zone widths for honeybees from ground and aerial spraying of insecticides

The relative field hazards of insecticides to honeybees have been estimated by considering intrinsic toxicity levels and field application rates. This approach is extended here to a consideration of buffer zones downwind of sprayed areas by estimating the distance at which bees would encounter an LD(50) dose from spray drift. 'LD(50) distances' are determined for both ground and aerial spraying of ground crops in Britain using published data on spray deposition under various weather conditions. For ground spraying at low wind speeds (< or =3 m s(-1)), this zone of risk is up to 5 m for the great majority of compounds. Aerial spraying in unstable atmospheric conditions appears to produce drift deposits of about the same order of magnitude as from ground spraying at wind speeds of about 4 m s(-1), with maximum LD(50) distances of < or =40 m for chlorpyrifos, fenitrothion and triazophos. For aerial spraying in stable atmospheric conditions these distances would be much greater. Pieris brassicae larvae are contrasted with honeybees in their relative sensitivities to insecticides and consequent LD(50) distances.     

Artificial sweat enhances dermal transfer of chlorpyrifos from treated nylon carpet fibers

The dermal transfer and absorption of 14C-ring-chlorpyrifos from nylon carpet fibers was measured in skin penetration-evaporation cells with excised pig skin. Prior to application, synthetic sweat was applied to skin in half of the cells. Radioactivity was measured in receptor fluid, dermis, epidermis, tape stripping samples, and vapor trap samples during a 24-h period. The sum of radiolabel recovered from the dermis and receptor fluid represented the absorbed dose. There was no significant difference (p > 0.05) in percutaneous absorption between cells that received the synthetic sweat application and "dry" cells (1.3 +/- 0.3% of applied dose). There was significantly more (p < 0.05) radiolabel recovered from tape stripping (5.4 +/- 2.1 vs. 2.8 +/- 0.6%) and in the epidermis (4.5 +/- 0.8 vs. 3.1 +/- 0.3%) from cells that received the synthetic sweat application, which indicated synthetic sweat facilitated transfer of chlorpyrifos from a treated substrate to the skin surface. The measured value for percutaneous absorption of chlorpyrifos agreed with the value predicted from an empirical model previously developed for nitro compound-containing soil.     

Biosolids-amended soils: Part I. Effect of biosolids application on soil quality and ecotoxicity.

Investigations of potential risk from biosolids generally indicate that land application does not threaten human or ecosystem health, but questions continue to arise concerning the environmental effects of this practice. This research project was initiated to evaluate ecotoxicity resulting from the amendment of soils with biosolids from municipal wastewater treatment plants. Toxicity was evaluated using standard tests, including earthworm mortality, growth, and reproduction; seedling germination and root elongation; microbial respiration; and nematode mortality and reproduction. Nineteen municipal wastewater treatment plants were identified to participate in an initial screening of toxicity, and five were chosen for a more detailed evaluation. In addition, two soils with historically high applications of high-metal biosolids were evaluated. Contaminants examined were zinc, copper, nickel, chromium, arsenic, cadmium, lead, and coplanar polychlorinated biphenyls (PCBs). Single applications had no effect on soil metal concentrations. Coplanar PCBs were not detectable in any of the soils or biosolids. All target organisms were sensitive to reference toxicants. Limited toxicity was observed in a small number of the amended soils, but no patterns emerged. Approximately one-half of the negative effects of biosolids on bioindicators could be attributed to routine properties, such as slight depression of pH and/or elevated salinity. None of the accumulated metal concentrations were excessive, and most would not be considered elevated. These observations suggest that current regulations for application of biosolids to soils are providing adequate ecosystem protection.     

Enantioselective biodegradation of mecoprop in aerobic and anaerobic microcosms

Natural attenuation of mecoprop has been studied by determining changes in enantiomeric fraction in different redox environments down gradient from a landfill in the Lincolnshire limestone. Such changes could be due to differential metabolism of the enantiomers, or enantiomeric inversion. In order to confirm the processes occurring in the field, microcosm experiments were undertaken using limestone acclimatised in different redox zones. No biodegradation was observed in the methanogenic, sulphate-reducing or iron-reducing microcosms. In the nitrate-reducing microcosm (S)-mecoprop did not degrade but (R)-mecoprop degraded with zero order kinetics at 0.65 mg l(-1)day(-1) to produce a stoichiometric equivalent amount of 4-chloro-2-methylphenol. This metabolite only degraded when the (R)-mecoprop disappeared. In aerobic conditions (S)- and (R)-mecoprop degraded with zero order kinetics at rates of 1.90 and 1.32 mg l(-1)day(-1) respectively. The addition of nitrate to dormant iron-reducing microcosms devoid of nitrate stimulated anaerobic degradation of (R)-mecoprop after a lag period of about 20 days and was associated with the production of 4-chloro-2-methylphenol. Nitrate addition to sulphate-reducing/methanogenic microcosms did not stimulate mecoprop degradation. However, the added nitrate was completely utilised in oxidising sulphide to sulphate. There was no evidence for enantiomeric inversion. The study reveals new evidence for fast enantioselective degradation of (R)-mecoprop under nitrate-reducing conditions.     

Methodology for estimating soil carbon for the forest carbon budget model of the United States, 2001

The largest carbon (C) pool in United States forests is the soil C pool. We present methodology and soil C pool estimates used in the FORCARB model, which estimates and projects forest carbon budgets for the United States. The methodology balances knowledge, uncertainties, and ease of use. The estimates are calculated using the USDA Natural Resources Conservation Service STATSGO database, with soil dynamics following assumptions based on results of site-specific studies, and area estimates from the USDA Forest Service. Forest Inventory and Analysis data and national-level land cover data sets. Harvesting is assumed to have no effect on soil C. Land use change and forest type transitions affect soil C. We apply the methodology to the southeastern region of the United States as a case study.     

Microcosm studies of microbial degradation in a coal tar distillate plume

Investigation of a groundwater plume containing up to 24 g l(-1) phenolic compounds suggested that over a period of nearly 50 years, little degradation had occurred despite the presence of a microbial community and electron acceptors within the core of the plume. In order to study the effect of contaminant concentration on degradation behaviour, laboratory microcosm experiments were performed under aerobic and anaerobic conditions at four different concentrations obtained by diluting contaminated with uncontaminated groundwater. The microcosms contained groundwater with total phenols at ca. 200, 250, 660 and 5000 mg l(-1), and aquifer sediment that had been acclimatised within the plume for several months. The microcosms were operated for a period of 390-400 days along with sterile controls to ascertain whether degradation was microbially mediated or abiotic. Under aerobic conditions, degradation only occurred at concentrations up to 660 mg l(-1) total phenols. At phenol concentrations below 250 mg l(-1) a benzoquinone intermediate, thought to originate from the degradation of 2,5-dimethylphenol, was isolated and identified. This suggested an unusual degradative pathway for this compound; its aerobic degradation more commonly proceeding via catecholic intermediates. Under anaerobic conditions, degradation only occurred in the most dilute microcosm (total phenols 195 mg l(-1)) with a loss of p-cresol accompanied by a nonstoichiometric decrease in nitrate and sulphate. By inference, iron(III) from the sediment may also have been used as a terminal electron acceptor, in which case the amount of biologically available iron released was calculated as 1.07 mg Fe(III)/g of sediment. The study shows that natural attenuation is likely to be stimulated by dilution of the plume.     

New indicator approaches for effective urban air quality management

Measurements of urban air quality at monitoring stations in developed countries have frequently involved the criteria gaseous pollutants, particulates, hazardous air pollutants, perceived air quality and relevant meteorological conditions. Large numbers of indicators have therefore been established to quantify emissions, concentrations and environmental and human health impacts of each of these groups of substances. To simplify the data for management, several indicators have been grouped together to form urban air quality indices but the weightings of individual variables is contentious. In industrialising and developing countries, data may be limited and traditional air pollutant indicators cannot often be constructed. The emphasis therefore has to be placed on the development of policy-relevant indicators, such as Response Indicators that reflect different policy principles for regulating air pollutant emissions. Indices that quantify the air quality management capabilities and capacities at the city level provide further useful decision-relevant tools. Four sets of indices, namely, 1. air quality measurement capacity, 2. data assessment and availability, 3. emissions estimates, and 4. management enabling capabilities, and a composite index to evaluate air quality management capability, were constructed and applied to 80 cities. The indices revealed that management capability varied widely between the cities. In some of the cities, existing national knowledge on urban air quality could have been more effectively used for management. It was concluded that for effective urban air quality management, a greater emphasis should be given, not just to monitoring and data capture programmes, but to the development of indicators and indices that empower decision-makers to initiate management response strategies. Over-reliance on restricted, predetermined sets of traditional air quality indicators should be avoided.     

The role of perceived system knowledge in predicting appraisal reactions,job satisfaction,and organizational commitment

There is a very large research base in Applied Psychology on the importance of affective reactions on organizational functioning. Likewise, performance appraisal has been a heavily researched area within the field. The present field studies attempt to bridge our understanding of these two areas by studying the relationship between performance appraisal process variables and employee affective reactions. In particular, the current studies examine the effects of a relatively new performance appraisal variable, Perceived System Knowledge (Williams and Levy, 1992), on appraisal reactions and job attitudes. In both studies, there was a strong relationship between employees' levels of perceived system knowledge and their appraisal reactions and job attitudes. In Study 1, when controlling for performance rating, PSK was positively related to appraisal reactions, job satisfaction, and organizational commitment. The findings from Study 1 were replicated in the second study which employed a longitudinal design. In addition, Study 2 found a relationship between PSK and fairness perceptions. Implications for these results and suggestions for approaching performance appraisal from an organizational perspective are proposed. © 1998 John Wiley & Sons, Ltd.