W2082: Evaluating the Physical and Biological Availability of Pesticides and Contaminants in Agricultural Ecosystems
Statement of Issues and Justification
Agricultural 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 organic and nanoparticle contaminants applied to soil found in animal manures, biosolids and wastewater.Because of the potential for contamination it is critical that chemicals are employed in ways that minimize contamination risks and that environments currently contaminated with organic chemicals be effectively remediated. 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 through minimizing contamination risks and implementing effective remediation practices. 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). Although it is likely future pesticide use will decline as a result of improved integrated pest management strategies, pesticides will remain a component of 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 as well. The environmental fate of pharmaceutically active compounds (PhACs) such as antibiotics, hormones, drugs and other compounds capable of endocrine disruption is also a growing concern. For example, animal farms in the U.S. are estimated to release 54.5 Mg of hormones per year, most of which (49 Mg) are estrogenic hormones; the remaining 5.5 Mg are androgenic hormones, such as testosterone (Lange et al., 2002; Jacobsen et al., 2005). In addition to animal feeding operations urban wastewater is increasingly being seen as a source of PhACs in soil. Municipal wastewater is used for irrigation in agricultural crop production as well turf operations. Kinney et al (2006) reported that the use of reclaimed wastewater for irrigation of turf resulted in the presence of a number of pharmaceutical compounds in soil although no net accumulation was observed in the top 30 cm. This indicates that natural inactivation and removal of the compounds was occurring through degradation, sorption, or a combination of both. Recent work by members of this committee indicates that both naturally occurring and pharmaceutically based estrogens, as well as a widely used pharmaceutical compound, can accumulate in soils under conditions of wastewater irrigation. Being only a recent area for research, many questions remain concerning the environmental and human health impacts of PhACs and their transformation products existing in soil.
Antibiotics are used in the livestock industry for therapeutic treatment of sick animals, illness prevention (prophylactic use), and to enhance growth rates and increase feed efficiency (Wegener, 2003). Using current drug delivery practices, studies have shown that 30 80% of an antibiotic dose can rapidly pass through the G.I. tract of an animal in an unaltered state (Elmund, et al., 1971; Levy, 1992;). Subsequently, antibiotics present in animal manure are introduced into agricultural ecosystems via land application of animal waste. The presence of these compounds in the environment may adversely impact soil microbial communities, diminish water quality, and increase the spread of antibiotic resistant bacteria (Daughton and Ternes, 1999; Sarmah et al., 2006; Lee et al., 2007; Aga, 2008). The aforementioned concerns highlight the need to mitigate the loss of antibiotics from agroecosystems and maintain environmental quality.
Nanotechnology is a new technology that offers a wide range of applications including consumer products, remediation of contaminated soil and water, medical imaging, and targeted drug delivery. It is projected to become a $1 trillion market by 2015 (Nel et al., 2006). The behavior and effect of nanoparticles in the environment are poorly understood. It is important to determine basic fate and transport characteristics of nanoparticles as well as unintended effects they may have on native biota in order to ensure that nanotechnology implementation can be realized with minimal impact on the environment.
In addition to specific pesticides and contaminants applied to soils 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. 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, 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, pesticide 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 whose research benefits from the opportunity to communicate with one another on a regular basis through this project. 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 and nanoparticles. 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 across a range of agricultural ecosystems. By developing better management techniques, the risks of adverse environmental and health effects of contaminants will be minimized.
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