Mercury distribution in sediment profiles of six Louisiana Lakes

A study was conducted of six Louisiana Lakes to examine the relationship between sediment properties including mercury content and health advisories associated with mercury levels in fish. Comparison was made between three lakes with health advisories (Black Lake, Chicot Lake, and Henderson Lake) and three lakes where the levels of mercury in fish are below health advisory levels (False River, Lake St. John, and Miller Lake). Three sediment core samples were collected from each lake and sectioned into 2-cm increments to a depth of 20 cm. Sediment properties measured in each depth increment of the sediment profile included total mercury, 137Cs activity (for sedimentation rate), and sediment organic matter content. Of the lakes studied, those lakes that have health advisories for mercury tended to have higher total mercury contents, usually higher sediment organic matter contents, and higher sedimentation rates than sediments in lakes where health advisories for mercury are not issued.