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United States Department of Agriculture

Agricultural Research Service

Title: Geophysical Electromagnetic Survey Methods Applied to Agricultural Waste Sites

Authors
item Eigenberg, Roger
item Korthals, Rodney
item Nienaber, John

Submitted to: American Society of Agri Engineers Special Meetings and Conferences Papers
Publication Type: Other
Publication Acceptance Date: July 15, 1996
Publication Date: N/A

Interpretive Summary: Waste management systems are complex and operate under great variability. Each step of a waste management system has the potential for nutrient loss associated with environmental risks. Nutrient flow can be predicted using modeling methods to estimate contamination risk, recognizing that actual conditions may vary substantially from predicted levels. Variability at specific sites occurs as a result of nutrient concentrations, site vulnerability, and/or handling methods. Soil coring and analysis provide measures of contaminant levels but are expensive and time consuming for general surveys of waste handling sites. Less expensive, quicker, but adequate methods are needed for evaluating the relative level of contaminant movement beneath waste management sites. Electromagnetic methods have the potential to fulfill that need and have been assessed near liquid storage ponds. For livestock production systems, such as cattle feedlots, most of the manure is handled in solid rather than liquid form. Therefore, electromagnetic methods need to be evaluated for solids handling areas as well. This report presents survey results from a compost site and a waste storage pond. The methodology shows good potential as a waste site diagnostic tool indicating concentrations of nutrients exceeding thresholds, thereby signaling a need for remedial action.

Technical Abstract: Methods of estimating the environmental impact at waste management sites often involve the need for sophisticated laboratory techniques and extensive sampling machinery (coring machines, etc.) with the risk of altering the system under examination. Noninvasive methods such as electromagnetic (EM) instrumentation offer advantages of relative ease of use with no physical alteration of the site (Brune and Doolittle, 1990). This paper reports the use of EM instrumentation for surveying agronomic and waste treatment sites at locations which had been previously profiled by soil coring for evaluation of nutrients in the soil profile. Surveys were made using a geophysical EM instrument capable of measuring conductivity three to 7.5 meters below the surface of the ground with horizontal or vertical polarization. Two specific sites were analyzed to evaluate the effects of management practices: 1) a composting site with one section in use since 1985 and with expanded operation to another section in 1989, 2) a waste storage pond (operational in 1973) holding precipitation runoff from a cattle feedlot. Correlation analysis between the EM conductivity measurements and chemical analysis at both sites (concentrations of ammonium, nitrate, chloride, and phosphorus) show significant (p<0.05) correlations for the ions while nonionic P did not show a significant correlation. The EM measures were able to distinguish the six year- old site from the ten year-old site (p<0.05). The results indicate that EM methods provide information useful for livestock site surveys of livestock waste management facilities.

Last Modified: 7/22/2014
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