Browsing by Subject "leaching"
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Item Bisphenol A: Should You Be Concerned?(2008-04-08) Tweet, Marysia SusanBisphenol A (BPA) is a raw material primarily used as a monomer in polycarbonate and epoxy resin production. Industry produces more than 6 billion pounds of BPA each year, and it has been used commercially for ~50 years. Polycarbonates are used in infant bottles, plastic dinnerware and storageware, and therefore BPA may leach into human food. According to the Centers for Disease Control and Prevention (CDC), about 95% of Americans contain BPA in their blood. Recent concerns regard the effects of low exposure of BPA on human development and reproduction stemming from experimental evidence that BPA may weakly bind to estrogen receptors. The US NTP held an expert panel Aug 2007 reviewing 500 studies about BPA. The panel expressed “some” concerns that exposure causes neural and behavioral effects in infants and children and “minimal” concerns that it causes early puberty. No major health risks were found. A final statement is pending. The absolute decision regarding the effects of BPA on humans remains debated and is subject for continued studies.Item Plant diversity, CO2 and N influence inorganic and organic N leaching in grasslands(2007) Dijkstra, Feike A; West, Jason B; Hobbie, Sarah E; Reich, Peter B; Trost, JaredIn nitrogen (N)-limited systems, the potential to sequester carbon depends on the balance between N inputs and losses as well as on how efficiently N is used, yet little is known about responses of these processes to changes in plant species richness, atmospheric CO2 concentration ([CO2]), and N deposition. We examined how plant species richness (1 or 16 species), elevated [CO2] (ambient or 560 ppm), and inorganic N addition (0 or 4 g·m−2·yr−1) affected ecosystem N losses, specifically leaching of dissolved inorganic N (DIN) and organic N (DON) in a grassland field experiment in Minnesota, USA. We observed greater DIN leaching below 60 cm soil depth in the monoculture plots (on average 1.8 and 3.1 g N·m−2·yr−1 for ambient N and N-fertilized plots respectively) than in the 16-species plots (0.2 g N·m−2·yr−1 for both ambient N and N-fertilized plots), particularly when inorganic N was added. Most likely, loss of complementary resource use and reduced biological N demand in the monoculture plots caused the increase in DIN leaching relative to the high-diversity plots. Elevated [CO2] reduced DIN concentrations under conditions when DIN concentrations were high (i.e., in N-fertilized and monoculture plots). Contrary to the results for DIN, DON leaching was greater in the 16-species plots than in the monoculture plots (on average 0.4 g N·m−2·yr−1 in 16-species plots and 0.2 g N·m−2·yr−1 in monoculture plots). In fact, DON dominated N leaching in the 16-species plots (64% of total N leaching as DON), suggesting that, even with high biological demand for N, substantial amounts of N can be lost as DON. We found no significant main effects of elevated [CO2] on DIN or DON leaching; however, elevated [CO2] reduced the positive effect of inorganic N addition on DON leaching, especially during the second year of observation. Our results suggest that plant species richness, elevated [CO2], and N deposition alter DIN loss primarily through changes in biological N demand. DON losses can be as large as DIN loss but are more sensitive to organic matter production and turnover.Item Proceedings of the 1st Agricultural Drainage and Water Quality Field Day(2002-08-14) Strock, Jeffrey S.; Baker, Jim; Busman, Lowell; Gupta, Satish; Moncrief, John; Randall, Gyles; Russelle, Michael; Taylor, ElwynnItem Proceedings of the 2nd Agricultural Drainage and Water Quality Field Day(2005-08-19) Strock, Jeffrey S.; Fausey, Norm; Kanwar, Ramesh; Skaggs, Wayne; Gupta, Satish; Moncrief, John