W1082: Evaluating the Physical and Biological Availability of Pesticides and Pharmaceuticals in Agricultural Contexts
Statement of Issues and JustificationAgricultural production can result in the contamination of soil, air, and water resources. Identifying and quantifying the physical, chemical, and biological processes that control the behavior of organic chemicals in the environment is imperative for improving management of agrochemicals, minimizing contamination of natural resources, and remediating currently contaminated environments. This research project will address two significant issues: (1) the persistence and availability in the environment (including bioavailability, transport, uptake, and degradation) of pesticides used in agricultural production and (2) the fate of pharmaceuticals in land-applied animal manures and biosolids.
Use of organic chemicals in agricultural production has resulted in contamination of soil, air, and water. To justify their use, chemical technologies must have greater societal benefits than risks. So it is critical that chemicals are employed in ways that minimize future contamination. Remediation of environments currently contaminated with organic chemicals is also an important goal. Evaluating and quantifying the behavior of organic chemicals in soil and water is vital for the development of sound strategies that ensure sustainable agriculture by protecting natural resources.
About 2 billion kilograms of chemicals are used as pesticides each year in the U.S., with agricultural usage accounting for ~77% (Aspelin and Grube, 1999). It is hoped that future pesticide use will decline as a result of improved integrated pest management strategies. Nevertheless, pesticides will remain a mainstay in many production systems. Research is needed to optimize pesticide efficiency with minimal environmental impacts. Newly developed pesticides, many of which are applied at rates one-tenth or less those of conventional pesticides, are often highly toxic to nontarget crops or aquatic organisms; thus, considerable knowledge of the transport and fate of these substances is needed.
The environmental fate of pharmaceutically active substances such as antibiotics and hormones is also a growing concern. Almost half of the 23 million kilograms of antibiotics produced annually in the United States is used for agriculture, with the majority being used as animal-feed additives to promote growth. With increases in the use of antibiotics and hormones in concentrated animal feeding operations and land application of manure, there are concerns that excreted pharmaceuticals will migrate in the environment, with potential impacts on water supplies and the production of antibiotic-resistant microbial populations. Thorough scientific studies of the potential of these organic substances to affect ground and surface waters, their impact on soil microbial communities, and their overall persistence in the environment are in their beginning stages. A better understanding of the environmental fate of antibiotics and hormones is needed to assess the environmental risk involved in releasing animal wastes to the environment.
Other organic chemicals related to agriculture are also of interest. For example, petroleum products are commonly used on farms and "inert" materials (e.g., solvents and emulsifiers) are often present in pesticide formulations. In addition, fundamental studies of the behavior of model organic compounds can help us understand the mechanisms by which more complex compounds interact with solid, solution, and vapor phases in the environment. Both urban and rural sectors of the economy can benefit from basic and applied studies of organic chemicals whether they are used in agricultural production, are used in home gardens and lawn care, or enter the environment through regulated or unregulated waste disposal.
The fate and accumulation of organic compounds and their degradation products are mediated by various -- often tightly coupled -- processes, including advection and diffusion, sorption and desorption, biodegradation, and chemical reactions. These processes occur within and between intimately associated environmental compartments (soil, water, air, and biota). For example, chemical interactions with the soil regulate persistence, release into water and air, and bioavailability, which in turn impact pesticide efficacy, degradation, and off-site transport. Because the interactions between organic chemicals and environmental media are so complex and occur at disparate spatial and temporal scales, research involving environmental pollution requires a multidisciplinary approach. A unique strength of this research project is the collaboration among its members from different scientific disciplines who, outside the committee, do not have sufficient opportunity to communicate with one another. This project provides a forum where specialists in mechanisms of chemical behavior, microbial ecology, transport behavior, mathematical modeling, and field assessment techniques can exchange information gleaned from individual research efforts as well as work on collaborative projects. Such cooperative efforts among research groups representing different kinds of expertise and diverse geographical areas are imperative to develop appropriate management techniques for minimizing environmental contamination and risk.
The long-term goal of this project is to minimize environmental contamination from pesticides, pharmaceuticals, and related organic chemicals. We propose to conduct a cooperative research program that elucidates fundamental mechanisms of chemical behavior and applies this knowledge at multiple spatial and temporal scales. In combination with mechanistic models, the principles of chemical behavior will be incorporated into management models. Research conducted will be useful in the continued development of best management practices for minimizing environmental contamination, as well as in the development of efficient and comparatively inexpensive strategies for remediating contaminated environments. Results of the research conducted by members of this multistate project group will be applicable to both agricultural ecosystems and to urban systems. Thus it will help to fulfill USDA goals to enhance protection of soil and water resources in both agricultural and urban sectors of the economy. By developing better management techniques, the risks of adverse environmental and health effects of chemical technology will be minimized.
A multistate approach is needed to address these issues because the cost of doing research demands a high level of communication among researchers, because comparison and contrast of the behavior of organic chemicals in a variety of soils and local climates is critical to improving predictions of behavior, and because it will help to standardize methodological approaches used to evaluate the fate and transport of pharmaceuticals and pesticides in the environment. Moreover, a concerted multistate effort has the great likelihood of effectively and credibly communicating research results to stakeholders such as the U.S. Environmental Protection Agency, state and federal extension personnel, waste water specialists, agricultural industries, and farmers.
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