NC1187: The Chemical and Physical Nature of Particulate Matter Affecting Air, Water and Soil Quality. (NCR174)

(Multistate Research Project)

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A. The need as indicated by stakeholders.



Agricultural practices affect air, soil, and water quality for both rural and urban communities. The impacts flow both ways. Activities in urban settings affect soil and water quality for rural and agricultural use, while public concern and regulatory authority to protect the environment impel efforts to preserve and improve environmental quality. Efficient management and effective regulation will optimize environmental and health protection without crippling the economy, rural or urban. The focus of Multistate Project NC-1187 is the behavior of particulate matter in size ranges capable of movement through soil, air, and water. Although this encompasses sizes from silt (2 - 50 µm) to the sub-micrometer range, nanoparticles are amongst the most reactive particles in the environment, and advanced analytical methods are needed to study them. Natural nanoparticles in soil, water, and air must be understood to the point that their characteristics and behavior can be controlled so that this natural resource may be more fully utilized.

Agricultural practices also create and disperse synthetic nanoparticles. The environmental abundance of nanoparticles produced by agriculture must be understood and any negative effects mitigated. Echoing this view is that of numerous leaders from government, industry, environment and academia, who have called for extensive research on identifying and assessing the potential risks of nanomaterials to human health and the environment (Service, 2005). According to Roco (2011), nanotechnology will have a $3 trillion impact on the global economy by 2020. The proposed budget of the National Technology Initiative for 2016 is about $1.5 billion, of which $7.3 million is projected for the USDA National Institute of Food and Agriculture (http://www.nano.gov, accessed on 6/7/2015). After the initial exploratory phase, which spanned between 2001 and 2010, the scientific community is immersed in the second phase of nanotechnology development characterized by an increased use of nanotechnology in non-traditional areas such as agriculture (Roco, 2011; Liu and Lal, 2015). Agricultural and food systems poised to benefit from nanotechnology (e.g., Liu and Lal, 2015; Servin et al., 2015), and have the research expertise and infrastructure in the land grant university system to determine the risks and benefits of nanoparticles. Project NC-1187 has been able to extend that expertise and infrastructure to national user facilities that make state of the art instrumentation and computer power available to our focus on particulate matter in air, soil, and water. Continuing this project will allow us to reap the benefits of the contacts we have established and expertise we have gained in the past.

Particulate matter in the air of rural and agricultural regions has a complex array of sources that are both primary (direct emissions) and secondary (formed in the atmosphere from reactions of gaseous chemicals). In order to understand the context of agricultural emissions contributing to particulate matter and the effects of particulate matter on agricultural production, air quality, and climate, more information is critically needed on the primary and secondary particle sources. Chemical tracers can be used to assess the origins and transformations occurring in the atmosphere, and put into context whether aerosols in agricultural regions truly are a result of agricultural activities, or may be due to natural emissions, fossil fuel use or extraction, and other urban or industrial activities. Development and application of novel technologies including the use of synchrotron radiation, field instrumentation, and data analysis approaches are needed by the research community and stakeholders to understand the sources and consequences of this particulate matter.

B. The importance of the work and the consequences if not done.



The reactivity of soils with respect to plant nutrient elements and environmental toxins is to a very great extent dependent on reactions that involve particles with diameters of tens of micrometers or less (silt, clays, microbes, nanoparticles). Because these fine particles in soils are contained in a very complex mixture, it is often difficult to gain a mechanistic understanding of processes governing the retention and mobility of many chemical species in soils by traditional techniques. For example, it is well known that phosphorus is associated with fine particles (Hanley and Murphy, 1970), but the exact chemistry of these particles is not well understood. Recent work has demonstrated the utility of synchrotron x-ray microprobe spectroscopy for the study of the chemistry of P in the fine fraction of soils (Kizewski, et al, 2011). Copper, zinc and lead are enriched in the fine fraction of soil, and particle size is an important factor for the bioaccessibility of these elements (Madrid et al., 2008; Baker et al., 2012; Baker et al., 2014). Ferrihydrite, a common nano-sized iron-bearing mineral in soils, was recently shown to bind tightly to C, more so when it was coprecipitated with ferrihydrite rather than sorbed on ferrihydrite (Chen et al., 2014). The complexation of C with particles in soils is a major mechanism for sequestering C, preventing it from being emitted into the atmosphere.


A mechanistic understanding of the role of particle size in mobility and bioaccessibility requires a detailed understanding of the chemistry of soil particles at a scale that is only possible using advanced spectroscopic and microscopic instruments. Recently questions concerning the environmental fate of nanoparticles arising from agricultural operations and from the manufacture, use or disposal of consumer products have arisen. Little is known about the toxicology and environmental behavior of these particles. These particles are very difficult to study because the particles are < 100 nm. The NC-1187 group is well poised to address the problems presented by the analytical difficulties that nanoparticles present. Our current access to synchrotron sources and the cooperation that has developed among members will serve to help solve the difficult problem of completely characterizing nanoparticles with a focus on their environmental and agricultural impact. Without the combined efforts of the NC_1187 membership, agricultural research is at risk of falling behind in terms of using state-of-the-art instrumentation to solve problems related to particulate behavior in the environment. The availability of nutrients in sustainable systems depends on reactions at particulate surfaces that often must be observed at the microscopic scale. The transport of toxic contaminants is governed by the movement, dissolution, and nucleation of particulate matter. Microscopic and spectroscopic methods are needed to follow such particles, to determine their static and dynamic composition, and to determine their availability to living organisms. The situation may be likened to the current ability to characterize microbial communities in natural systems by the analysis of genetic material. Without the application of molecular tools, we will not have the required knowledge to advance agricultural systems to minimize inputs and contamination while optimizing production and economy.

C. The technical feasibility of the research.



A common thread that runs through much environmental research is the importance of processes that operate simultaneously on different spatial and temporal scales. For instance, major questions surround particulate matter affecting rural air, soil, and water quality. The technical feasibility of applying synchrotron-based methods to a wide range of sample sizes and chemical compositions is amply supported by the current scientific literature. The utilization of a combination of techniques to accomplish full characterization of particles and to relate these properties to behavior in complex systems has become increasingly important and successful. We will extend these tested approaches to agricultural systems.

D. The advantages for doing the work as a multi-state effort.



There are several advantages in doing this project as a multi-state effort. First, particulate matter (PM) is transported across state and regional boundaries by both air and water making it a regional rather than local problem. Second, just as urban PM emissions vary considerably from one metropolitan area to another, we can expect rural PM emissions also vary because livestock industry, crops, farming practices, soils, and water chemistry vary regionally. Third, the central focus of this project (integrated modern instrumentation, including synchrotron microspectroscopy) demands extensive cooperation among members: sharing experience with specific facilities and analytical techniques, and sharing disciplinary expertise (soil, water, and air chemistry, microbiology, physics, etc.). Fourth, this project will promote the use of synchrotron sources to push the envelope in terms of micro-spectroscopic characterization of particles and will integrate synchrotron techniques with other state-of-art-tools provided by national labs and universities (Anderson and Hopmans, 2013; Udawatta et al., 2013). Fifth, project participants will share samples and data for multiple analyses, and will work to produce an integrated investigation sample set or experimental site.

In the past, synchrotron research by soil scientists primarily focused on industrial contaminants, i.e., metals and metalloids. There are many opportunities now with micro-focused techniques to study agricultural contaminants such as metals, elements like carbon and organic matter dynamics which are critical in addressing global climate change, phosphate and other nutrients in soils. This approach will link more basic soil science with applied soil science, particularly in the area of nutrient management. Finally, the members have already established an excellent record of multi-state collaboration.

This project will enhance our ability to assess the impact of micro- and nano-sized particles on processes taking place in agricultural and natural ecosystems by elucidating links between particulate (physical, biological and chemical) properties and their role in the sustainability and productivity of those systems. Research activities coordinated under this project will result in a catalog of physical and chemical properties of particulates related to agriculture production and of evaluations of the rate and transfer mechanisms of particulates through the environment. A greater number of scientists from state agricultural experiment stations will be utilizing the advanced analytical facilities funded by DOE and NSF to address important questions related to environmental protection and agricultural production. This will lead to the development of a better understanding of the behavior of pollutant and nutrient elements and compounds associated with fine particles in soil, water and air.

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