Dynamics of heavy metals and phosphorus in the pore water of estuarine sediments following agricultural intensification in Chao Lake Valley.

Previous research has revealed that agricultural intensification in the Chao Lake Valley since the 1980s has led to significant heavy metal and phosphorus (P) contamination of estuarine sediments in this region. However, the pore water plays a more important role than do sediments in the cycling of nutrients and metals in estuarine ecosystems. Average concentrations of Cd, Cr, Ni, Pb, and P in the pore water of estuarine sediments were 0.634, 3.11, 4.98, 3.98, and 49.9 μg L(-1), respectively. Average diffusive fluxes of these elements from the pore water to overlying water were -0.015, 0.058, 0.768, -0.238, and 20.0 μg m(-2) d(-1), respectively. Compared with similar studies, the values of heavy metal fluxes were low, indicating minimal diffusion between sediments and overlying waters; however, P diffusion from the sediment pore water to overlying water was high, indicating that the sediments may be a direct source of P to overlying water. Since P is a major cause of algal blooming in agricultural estuaries of Chao Lake, the obtained results could be useful in developing effective management strategies to control pollution in the Chao Lake Valley.