Picloram and napropamide sorption as affected by polymer addition and salt concentration

Polymer application to soil is a growing practice to improve soil physical properties and reduce soil erosion. Polymer addition can potentially influence herbicide and pesticide sorption in soil. The one-point distribution coefficient Kd values of two herbicides in the absence and presence of each of 10 polymers (7 polyacrylamides and 3 polysaccharides) were determined by the batch equilibrium method. The results showed that nonionic napropamide [2-(alpha-naphthoxy)-N,N-diethyl propionamide] sorption was essentially unaffected by the presence of any of the polymers. The influence of polymers on anionic picloram (4-amino-3,5,6-trichloropicolinic acid) sorption depends on the charge characteristics of polymers and salt concentrations in the solution. Electrostatic interaction and competition for sorption sites are two primary underlying mechanisms for the polymer influence. At low salt concentration, the increased picloram sorption in the presence of both cationic and anionic polymers was attributed to different electrostatic interactions and polymer partitioning between soil and solution phases. At high salt levels, the presence of polymers had either no influence or a slightly negative influence on the picloram sorption, which was attributed to competition for sorption sites. In field conditions, it is more likely that polymers have no or a slightly negative influence on herbicide sorption due to the presence of salts.     

Spatial and temporal modeling of microbial contaminants on grazing farmlands

This paper introduces an integrated spatial and temporal modeling system developed mathematically for assessing microbial contaminants on animal-grazed farmlands. The model uses fecal coliform, specifically Escherichia coli, as an indicator of fecal contamination and describes the sources, sinks, transport processes, and fate of E. coli contaminants in catchments and associated streams. Spatial features include grazing location, land topography, distance to a nearby stream, and distance through the stream network to the outlet. Temporal features are population dynamics on the land surface, in flow, and on streambeds. The model applies the principles of conservation of mass balance on two different types of pools: grid cells on land surfaces and networked stream segments. The model aims to improve the prediction of the effects of different land management strategies on the fecal contamination of waterways. This is achieved by characterizing the movement of fecal contaminants from land to streams and in-stream mobilization. Processes of attenuation, diffusion, and transport govern the movement. Our study site is a hill land catchment with an area of 140 ha and is used exclusively for animal grazing. The model was calibrated with previous research results, and then tested using the data collected at the outlet of the catchment. The sensitivity of the model predictions was analyzed for different scenarios: effect of stock rate, attenuation rate, and flow volumes. The similar pattern between monitored and predicted E. coli concentration proved that the model captures the key features that control the population dynamics of fecal contaminants. Further experiments are required to expand the model's functionality for covering more mitigation options.     

Landscape metrics and estuarine sediment contamination in the mid-Atlantic and southern New England regions

In a previously published study, quantitative relationships were developed between landscape metrics and sediment contamination for 25 small estuarine systems within Chesapeake Bay. These analyses have been extended to include 75 small estuarine systems across the mid-Atlantic and southern New England regions of the USA. Because of the different characteristics and dynamics of the estuaries across these regions, adjustment for differing hydrology, sediment characteristics, and sediment origins were included in the analysis. Multiple linear regression with stepwise selection was used to develop statistical models for sediment metals, organics, and total polycyclic aromatic hydrocarbons (PAHs). The landscape metrics important for explaining the variation in sediment metals levels (R2 = 0.72) were the percent area of nonforested wetlands (negative contribution), percent area of urban land, and point source effluent volume and metals input (positive contributions). The metrics important for sediment organics levels (R2 = 0.5) and total PAHs (R2 = 0.46) were percent area of urban land (positive contribution) and percent area of nonforested wetlands (negative contribution). These models included silt-clay content (metals) or total organic C (organics, total PAHs) of sediments and grouping by estuarine hydrology, suggesting the importance of sediment characteristics and hydrology in mitigating the influence of the landscape metrics on sediment contamination levels. The overall results from this study are indicative of how statistical models can be developed relating landscape metrics to estuarine sediment contamination for distributions of land cover and point source discharges.     

Do vesicle cells of the red alga Asparagopsis (Falkenbergia stage) play a role in bromocarbon production?

The Rhodophyceae (red algae) are an established source of volatile halocarbons in the marine environment. Some species in the Bonnemaisoniaceae have been reported to contain large amounts of halogens in structures referred to as vesicle cells, suggesting involvement of these specialised cells in the production of halocarbons. We have investigated the role of vesicle cells in the accumulation and metabolism of bromide in an isolate of the red macroalga Asparagopsis (Falkenbergia stage), a species known to release bromocarbons. Studies of laboratory-cultivated alga, using light microscopy, revealed a requirement of bromide for both the maintenance and formation of vesicle cells. Incubation of the alga in culture media with bromide concentrations below 64 mgl(-1) (the concentration of Br(-) in seawater) resulted in a decrease in the proportion of vesicle cells to pericentral cells. The abundance of vesicle cells was correlated with bromide concentration below this level. Induction of vesicle cell formation in cultures of Falkenbergia occurred at concentrations as low as 8 mgl(-1), with the abundance of vesicle cells increasing with bromide concentration up to around 100 mgl(-1). Further studies revealed a positive correlation between the abundance of vesicle cells and dibromomethane and bromoform production. Interestingly, however, whilst dibromomethane production was stimulated by the presence of bromide in the culture media, bromoform release remained unaffected suggesting that the two compounds are formed by different mechanisms.     

Assessing chronic toxicity of bisphenol A to larvae of the African clawed frog (Xenopus laevis) in a flow-through exposure system

A number of currently used industrial chemicals are estrogenic, and therefore have potential to disrupt sexual differentiation in vertebrate wildlife during critical developmental windows. We assessed the effect of larval exposure to bisphenol A (BPA) on growth, development and sexual differentiation of the gonad in the African Clawed frog, Xenopus laevis. Larvae were maintained in flow-through conditions at 22 +/- 1 degrees C and exposed to BPA at mean measured concentrations of 0.83, 2.1, 9.5, 23.8, 100, and 497 microg/l, from developmental stages 43/45-66 (completion of metamorphosis). Each test concentration, plus dilution water control (DWC) and positive control (17beta-estradiol (E2), 2.7 microg/l) employed four replicate test vessels with 40 larvae per tank. Individual froglets were removed from test vessels upon reaching stage 66, and the study was terminated at 90 days. Froglets were dissected and sex was determined by inspection of gross gonadal morphology. Test concentrations of BPA had no effect on survival, growth, developmental stage distributions at exposure days 32 and 62, or mean time to completion of metamorphosis, compared to DWC. Analysis of post-metamorphic sex ratio, determined by gross gonadal morphology, indicated no significant deviations from expected (50:50) sex ratio, in DWC or any BPA test concentration. In contrast, exposure of larvae to (E2) resulted in feminisation, with sex ratio deviating significantly (31% male, replicates pooled). Exposure to BPA in the concentration range 0.83-497 microg/l in flow-through conditions had no observable effect on larval growth, development or sexual differentiation (as determined by gross gonadal morphology) in this study.     

Precaution,uncertainty and causation in environmental decisions

What measures of uncertainty and what causal analysis can improve the management of potentially severe, irreversible or dreaded environmental outcomes? Environmental choices show that policies intended to be precautionary (such as adding MTBE to petrol) can cause unanticipated harm (by mobilizing benzene, a known leukemogen, in the ground water). Many environmental law principles set the boundaries of what should be done but do not provide an operational construct to answer this question. Those principles, ranging from the precautionary principle to protecting human health from a significant risk of material health impairment, do not explain how to make environmental management choices when incomplete, inconsistent and complex scientific evidence characterizes potentially adverse environmental outcomes. Rather, they pass the task to lower jurisdictions such as agencies or authorities. To achieve the goals of the principle, those who draft it must deal with scientific casual conjectures, partial knowledge and variable data. In this paper we specifically deal with the qualitative and quantitative aspects of the European Union's (EU) explanation of consistency and on the examination of scientific developments relevant to variability and uncertain data and causation. Managing hazards under the precautionary principle requires inductive, empirical methods of assessment. However, acting on a scientific conjecture can also be socially unfair, costly, and detrimental when applied to complex environmental choices. We describe a constructive framework rationally to meet the command of the precautionary principle using alternative measures of uncertainty and recent statistical methods of causal analysis. These measures and methods can bridge the gap between conjectured future irreversible or severe harm and scant scientific evidence, thus leading to more confident and resilient social choices. We review two sets of measures and computational systems to deal with uncertainty and link them to causation through inductive empirical methods such as Bayesian Networks. We conclude that primary legislation concerned with large uncertainties and potential severe or dreaded environmental outcomes can produce accurate and efficient choices. To do so, primary legislation should specifically indicate what measures can represent uncertainty and how to deal with uncertain causation thus providing guidance to an agency's rulemaking or to an authority's writing secondary legislation. A corollary conclusion with legal, scientific and probabilistic implications concerns how to update past information when the state of information increases because a failure to update can result in regretting past choices. Elected legislators have the democratic mandate to formulate precautionary principles and are accountable. To preserve that mandate, imbedding formal methods to represent uncertainty in the statutory language of the precautionary principle enhances subsequent judicial review of legislative actions. The framework that we propose also reduces the Balkanized views and interpretations of probabilities, possibilities, likelihood and uncertainty that exists in environmental decision-making.     

Review and assessment of models used to predict the fate of radionuclides in lakes

A variety of models for predicting the behaviour of radionuclides in fresh water ecosystems have been developed and tested during recent decades within the framework of many international research projects. These models have been implemented in Computerised Decision Support Systems (CDSS) for assisting the appropriate management of fresh water bodies contaminated by radionuclides. The assessment of the state-of-the-art and the consolidation of these CDSSs has been envisaged, by the scientific community, as a primary necessity for the rationalisation of the sector. The classification of the approaches of the various models, the determination of their essential features, the identification of similarities and differences among them and the definition of their application domains are all essential for the harmonisation of the existing CDSSs and for the possible development and improvement of reference models that can be widely applied in different environmental conditions. The present paper summarises the results of the assessment and evaluation of models for predicting the behaviour of radionuclides in lacustrine ecosystems. Such models were developed and tested within major projects financed by the European Commission during its 4th Framework Programme (1994-1998). The work done during the recent decades by many modellers at an international level has produced some consolidated results that are widely accepted by most experts. Nevertheless, some new results have arisen from recent studies and certain model improvements are still necessary.     

Photolysis of atrazine and ametryne herbicides in Barbados sugar cane plantation soils and water

The photodegradation kinetics of atrazine (2-chloro-6-(ethylamino)-4-isopropylamino-1,3,5-triazine) and ametryne (2-methylthio-4-ethylamino-6-isopropylamino-s-triazine), in fresh and coastal salt water from Barbados, were measured under irradiation with artificial solar and UV254-radiation. The first-order rate constants were greater for ametryne than for atrazine, and the rates were reduced in seawater relative to fresh water, and in soil slurries relative to fresh water. However, rates were accelerated in the presence of iron(III) at pH 3 due to photo-Fenton type processes. This rate enhancement was reduced at ambient pH values (pH 7-7.5) representative of surface water in Barbados. These results have important implications for the relative persistence of these contaminants in aquatic environments in tropical areas.     

Environmental Health Policy: Analytic “Framing” of the Great Lakes Picture

/ The International Joint Commission (IJC) has overseen the implementation of the Great Lakes Water Quality Agreement between Canada and the United States for 25 years. Part of its mandate has been to facilitate international cooperation among a diversity of stakeholders focusing on the "waters" and the "ecosystem." In the 1970s policy focused on phosphorus reduction and individual contaminants, with some efforts (after 1978) to take an ecosystem (ecological perspectives) approach. In the last 15 years human health effects from (real and perceived) environmental causes have received considerable recognition. By contrast, less concern has been expressed for what is traditionally considered "environment" issues (such as protecting fish species). This shift at the policy level is well illustrated in the manner in which human health is increasingly used as a way for mobilizing environmental agendas. This paper analyzes nine IJC biennial reports to track how the framing of Great Lakes issues has shifted from concern for its waters to concern for human neurobehavior and reproductive systems. Frame analysis is used to conceptualize the controversies that are expressed through the Great Lakes policy documents. The analysis of the reports also reveals a shift in operational frames, used by the IJC to mobilize decision-makers into action.     

The Relationship of Ecosystem Management to NEPA and Its Goals

/ The National Environmental Policy Act of 1969 (NEPA) was intended to promote a systematic, comprehensive, interdisciplinary approach to planning and decisionmaking, including the integration of the natural and social sciences and the design arts. NEPA critics have cited three key shortcomings in its implementation: (1) a lack of engagement with the NEPA process early in the planning process through interdisciplinary collaboration; (2) a lack of rigorous science and the incorporation of ecological principles and techniques; and (3) a lack of emphasis on the Act's substantive goals and objectives. In recent years and independent of NEPA, a policy of ecosystem management has been developed, which represents a fundamental change from a fragmented, incremental planning and management approach to a holistic, comprehensive, interdisciplinary land and resource management effort. We postulate that by incorporating ecosystem management principles in their planning and decisionmaking, federal agencies can address the shortcomings in NEPA implementation and move closer to NEPA's intent. A case analysis of EISs prepared by the USDA Forest Service before and after adopting an ecosystem management approach supports our hypothesis.