Submitted to: Proceedings of the 7th International Conference on Biogeochemistry of Trace Elements
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2003
Publication Date: 6/20/2003
Citation: Van Pelt, R.S., Chavez, J.A., Ketterer, M.E., Zobeck, T.M., Gill, T.E. 2003. Sediment deposition in an attic near a region of dust provenance: implications for historic regional dust, radionuclide, and trace element dispersion and deposition patterns. Proceedings of the 7th International Conference on Biogeochemistry of Trace Elements. Interpretive Summary: Fugitive dust from agricultural operations and denuded landscapes provides a hazard to commerce, human health, and environmental health. Recently, there has been considerable public debate concerning the Total Daily Maximum Loads (TMDL) of leached and eroded nutrients and trace elements entering the waterways of our nation. Little attention has been directed to quantifying the contribution of nutrients and trace elements to watersheds and coastal estuaries that are inputs arriving on aerosol dusts. The Southern Great Plains (SGP) is an area that is largely internally drained and thus does not contribute much to the TMDL of waterways from the usual processes of leaching and water erosion. The SGP is however an area from which dust generated during wind erosion events may be transported hundreds of kilometers on the prevailing winds and deposited over millions of hectares of watersheds or directly into streams, lakes, and coastal estuaries. Recently, the establishment of air quality sampler networks in many areas of the U.S.A. have allowed estimates of local inputs from atmospheric aerosols. Much less is know concerning the inputs to these ecosystems or the respirable hazards to human health that existed prior to the establishment of these networks. We initiated this study to determine whether or not readily available dust samples collected from attics in the region could be used to estimate past trends of dust, nutrient, and trace element fluxes.
Technical Abstract: Fugitive dust emission is a common result of wind erosion in semi arid areas. Recently, research on dust transport, dispersion, and deposition has focused on the nutrients, chemicals, and pathogens that are often transported on dust particles. While many techniques exist for quantifying present day atmospheric load and deposition, there is little information available concerning historic patterns of dust generation, transport, and characteristics. Undisturbed ventilated attics offer an archive of dust that dates back to the time the structure was constructed. We collected dust samples in a second-story attic dating back to 1954 and located several kilometers from the nearest eroding farm fields in Big Spring, TX. Big Spring is located at the southern end of the Southern High Plains, a regionally important dust source area. A total of 13 samples were collected from measured attic floor areas at 1.1 m intervals from the upwind gable to a distance of 13.7 m into the center of the rectangular building. The samples were dried at 60 deg. C, sieved through a 60 mesh screen to remove building debris and macro-biological materials, weighed, and split on a spinning riffler to provide uniform samples for analyses. Calculations of total deposition expressed as kg/sq. m, particle size analysis using a Beckmann-Coulter laser/PID instrument, carbon and nitrogen contents, and ICP/MS analysis for 239+240 Pu have been performed on the samples. Patterns of total deposition as a function of increasing distance from the gable vent matched a simple exponential decay function with a coefficient of determination (COD) of 0.996 and median particle diameter decrease with increasing distance from the vent matched the same exponential decay function with a COD of 0.951. Carbon and 239+240 Pu concentrations increased with distance from the vent and fit the same exponential decay function with negative slope parameters and CODs of 0.964 and 0.898, respectively. Since these patterns are similar to the deposition patterns noted in regional dispersion and dry deposition of aeolian dust, it would appear that this attic and others like it offer archives of not only the aeolian dust passing through and being deposited in the immediate location but also of areas several kilometers downwind as well. From the physical and chemical characteristics of this dust, it may be possible to obtain historic estimates of contaminant fluxes into downwind regions.