Jeremy Reiman, Emily DelDuco, Songjie He and Y. Jun Xu
Trace elements are elements generally found in very low concentrations in the environment. While many of these elements can be found naturally in the Earth’s crust, elevated levels in waterways can pose a serious threat to human and aquatic life. Research has shown that elevated concentrations of certain trace elements can disrupt development and reproduction and even cause death in aquatic plants and animals. Additionally, several trace elements can accumulate in tissues of organisms harvested for human consumption, such as fish or oysters, creating a potential pathway of human exposure to harmful levels.
Elevated levels of trace elements in surface water systems generally occur as a result of industry and mining byproducts and surface water runoff in urbanized areas. The U.S. Environmental Protection Agency and Louisiana Department of Environmental Quality have both established criteria for acceptable levels of trace elements in Louisiana’s waterways with the goal of maintaining the quality of the environment and people’s health.
Over the past several years, LSU AgCenter scientists have conducted studies to determine trace element levels in the Mississippi River and Atchafalaya River. These two river systems discharge approximately 163 cubic miles, or 80 percent of the total discharge, of freshwater into the Gulf of Mexico, delivering massive amounts of elements along the Louisiana coast. The team collects water samples every month and analyzes for more than 20 trace elements. They have not found elevated levels of any trace elements that are of concern to public health.
Average concentrations of boron, phosphorus, strontium and titanium were much greater in the Mississippi River than the Atchafalaya River; however, only boron concentrations were found to be significantly different. All other trace element average concentrations were fairly similar between the two rivers. Both rivers had significantly lower concentrations of boron and strontium during periods of high flow, while titanium concentrations were significantly higher. Arsenic and lithium concentrations in the Mississippi were significantly lower during high flow, while silver concentrations tended to increase with flow in the Atchafalaya River. Vanadium concentrations tended to be greater during periods of high flow in both rivers; however, this difference was not found to be significant. Barium, manganese, phosphorus and zinc concentrations showed negligible variance during various flows within both streams.
In conclusion, trace element concentrations in the Mississippi and Atchafalaya rivers are well within safe ranges. This is excellent news for coastal estuaries downstream and Louisiana anglers. Ongoing testing and continued efforts to reduce the discharge of pollutants into the waterways can continue to safeguard the quality and health of these vital rivers as well as estuaries downstream — all of which benefit state and local economies and our environment.
Jeremy Reiman, Emily DelDuco and Songjie He are graduate students, and Y. Jun Xu is a professor in the School of Renewable Natural Resources.
(This article appears in the fall 2017 issue of Louisiana Agriculture.)
Jeremy Reiman, graduate student in the School of Renewable Natural Resources deploys sampling equipment in the Atchafalaya River Wax Lake Outlet. Photo by Skylar Bue