Angus N. Crossan

The effect of vegetation on pesticide dissipation from ponded treatment wetlands: quantification using a simple model.

Field data shows that plants accelerate pesticide dissipation from aquatic systems by increasing sedimentation, biofilm contact and photolysis. In this study, a graphical model was constructed and calibrated with site-specific and supplementary data to describe the loss of two pesticides, endosulfan and fluometuron, from a vegetated and a non-vegetated pond. In the model, the major processes responsible for endosulfan dissipation were alkaline hydrolysis and sedimentation, with the former process being reduced by vegetation and the latter enhanced. Fluometuron dissipation resulted primarily from biofilm reaction and photolysis, both of which were increased by vegetation. Here, greater photolysis under vegetation arose from faster sedimentation and increased light penetration, despite shading. Management options for employing constructed wetlands to polish pesticide-contaminated agricultural runoff are discussed. The lack of easily fulfilled sub-models and data describing the effect of aquatic vegetation on water chemistry and sedimentation is also highlighted.

Sorption and desorption of endosulfan sulfate and diuron to composted cotton gin trash.

This paper investigates the potential use of composted cotton gin trash (CCGT) as a pesticide sorption medium in remediation of contaminated tailwater. CCGT was found to contain a large organic matter fraction (25.22%). Sorption of endosulfan sulfate and diuron, using the batch equilibrium method, was rapid but not limited for the range of applied concentrations, with diuron failing to reach equilibrium after two days. The partition K d and organic carbon partition K(OC) coefficients determined diuron ( Kd = 78; K(OC) = 526) and endosulfan sulfate ( Kd = 1500; K(OC) = 10,111) to reside in the solid phase. Limited desorption of diuron and higher range concentrations of endosulfan sulfate (50-100 microg L(-1)) were quantified. Sorption and desorption resulted from hydrophobic and hydrophilic interactions with the humic components of the compost. CCGT was concluded to have a superior sorption capacity to other sorbents reported in the literature, an assessment that requires field substantiation.

Calculation of Pesticide Degradation in Decaying Cotton Gin Trash

Pesticide residues were measured in stockpiled cotton gin trash (CGT) over a 2-year period. Samples were analysed by GC/MS/MS and interpretation of the results was aided by the presence of DDE residues, remnant from prior DDT use. Fourteen pesticide residues from current agricultural practice were detected in CGT. Several of these, including indoxacarb, profenofos, chlorpyrifos, propargite, bifenthrin, ethion and cyhalothrin, were more persistent than expected on the basis of published data for soil dissipation. The results showed a complex pattern of pesticide residue decay over time because of the simultaneous decomposition of the CGT matrix.

Capitalizing on deliberate, accidental, and GM-driven environmental change caused by crop modification

The transgenic traits associated with the majority of commercial genetically modified crops are focused on improving herbicide and insecticide management practices. The use of the transgenic technology in these crops and the associated chemistry has been the basis of studies that provide evidence for occasional improvement in environmental benefits due to the use of less residual herbicides, more targeted pesticides, and reduced field traffic. This is nicely exemplified through studies using Environmental Impact Quotient (EIQ) assessments. Whilst EIQ evaluations may sometimes illustrate environmental benefits they have their limitations. EIQ evaluations are not a surrogate for Environmental Risk Assessments and may not reflect real environmental interactions between crops and the environment. Addressing the impact cultivated plants have on the environment generally attracts little public attention and research funding, but the introduction of GM has facilitated an expansion of research to address potential environmental concerns from government, NGOs, industry, consumers, and growers. In this commentary, some evidence from our own research and several key papers that highlight EIQ assessments of the impact crops are having on the environment are presented. This information may be useful as an education tool on the potential benefits of GM and conventional farming. In addition, other deliberate, accidental, and GM-driven benefits derived from the examination of GM cropping systems is briefly discussed.

Research and practice: environmental action for improving water quality in cotton catchments since 1990

Abstract. In the modern era, agriculture must seek to be environmentally sustainable, an obligation now considered as a social contract. This demands that its activities do no significant harm, where the natural resources sustaining it are fully safeguarded, but of necessity in the context of profitable agriculture. The requirement to minimise the environmental impact of the necessary agrochemicals and pesticides in waterways is especially demanding. In the past 20 years, the Australian cotton industry has approached this obligation in various ways, needing extensive planning, learning from past experiences, but it can be legitimately claimed, with significant success. This success has been achieved at some cost, requiring large numbers of personnel, time and resources. This review aims to document the strategies that have been employed, how these required effective research management and how the research data generated was applied. To the extent that this complex program of participatory action has succeeded, while also acknowledging some dramatic failures, other areas of agriculture can also benefit by identification of the key factors contributing to success.

Sustaining Action and Optimizing Entropy: Coupling Efficiency for Energy and the Sustainability of Global Ecosystems

Consideration of the property of action is proposed to provide a more meaningful definition of efficient energy use and sustainable production in ecosystems. Action has physical dimensions similar to angular momentum, its magnitude varying with mass, spatial configuration and relative motion. In this article, the relationship of action to thermodynamic processes such as the spontaneous increase in entropy of the second law is explained and the utility of action for measuring changes in energy and material distribution is promoted. In particular, the view that increases in entropy and action are equivalent to disorder is challenged. Given that the development of action states may be assigned an economic value and the various sources of free energy assigned a price, action theory may provide a novel mechanism for the economic allocation of resources. The importance of the diversity and redundancy of energy resources and work processes to optimize action is highlighted.