Linking the Agricultural Landscape of the Midwest to Stream Health with Structural Equation Modeling.

Multiple physical and chemical stressors can simultaneously affect the biological condition of streams. To better understand the complex interactions of land-use practices, water quality, and ecological integrity of streams, the U.S.

Trends in metals in urban and reference lake sediments across the United States, 1970 to 2001.

Trends in metals concentrations in sediment cores from 35 reservoirs and lakes in urban and reference settings were analyzed to determine the effects of three decades of legislation, regulation, and changing demographics and industrial practices in the United States on concentrations of metals in the environment. Decreasing trends outnumber increasing trends for all seven metals analyzed (Cd, Cr, Cu, Pb, Hg, Ni, and Zn). The most consistent trends are for Pb and Cr: For Pb, 83% of the lakes have decreasing trends and 6% have increasing trends; for Cr, 54% of the lakes have decreasing trends and none have increasing trends.