Pollution Distribution Characteristics and Ecological Risk Assessment of Heavy Metals and Polycyclic Aromatic Hydrocarbons in the River Sediments in Anning, Yunnan Province

BACKGROUND Anning is an important industrial and mining city in the upper reaches of the Yangtze River Economic Belt. It is a fulcrum for economic development and ecological civilization construction in the Central Yunnan New Area. The investigation of geochemical water system sediments and hydrogeology in the Anning area was last performed in the 1970s and the 1980s. In recent years, the impact of human production and life on the ecological environment remains unclear. OBJECTIVES Surface sediment samples from the Anning area were investigated to reveal their pollution status, spatial distribution characteristics, and potential ecological risks of river sediments. METHODS X-ray fluorescence spectroscopy, inductively coupled plasma optical mass spectrometry, gas chromatography-mass spectrometry, and other methods were used to systematically analyze the contents and distribution characteristics of major elements, trace elements, and 16 priority-controlled PAHs. Geoaccumulation index, Hankanson ecological risk index, and sediment quality criteria were used to assess the ecological risk of eight typical heavy metals (As, Cd, Cr, Cu, Ni, Zn, Pb, and Hg) and PAHs. RESULTS Results showed that the heavy metal content in the river sediments from the Anning area was higher than the background values of the national and southern rivers. The spatial distributions of the heavy metals were highly variable and uneven. Additionally, Cd, Hg, and Ad showed medium to severe potential ecological risks. The average content of ∑PAHs was 20856ng/g, and the detection rate of the 16 monomers was ~100%. The overall ecological risk of PAHs was low, and their main sources were petrochemical industry and combustion of petroleum fuels. The major risks of pollutants in the river sediments of the Anning area were mainly concentrated in the vicinity of steel plants and chemical factories in the Tanglangchuan River. CONCLUSIONS This research provides a scientific basis for local governments to strengthen key industrial point source pollution control, and reduce and control industrial sewage discharge.