Impact of intensive mining on the distribution of heavy metals in water and sediment of Anning River, southwest China.

To investigate the impact of intensive mining on pollution of heavy metals in aqueous environment, water samples and seven sediment profiles adjacent to REE mine, iron mine, and V-Ti magnetite mine at Anning River, southwest China were collected and analyzed. Our study reveals that: (1) no significant pollution in water near mining regions of Maoniuping REE and Lugu iron mines were observed,(2) most outliers of As, Cd, Ni, Pb, Zn, and Cu in water are distributed at sites near towns not mining regions, except Cr that has been detected only in downstream waters near the V-Ti magnetite mine, because Cr was enriched in V-Ti magnetite mine and existed as oxyanions in water so that CrO₄^2- can be preserved longer than heavy metals existing as cations in alkaline water,(3) although these trace elements in sediment profiles indicated significantly decreased recently, most heavy metals in sediment of Anning River were considerably higher than local background values,(4) source identification of heavy metals in sediment near mining regions is complicated, because the natural contribution from undeveloped ore can also increase content of heavy metals in sediment which cannot be directly assigned as anthropogenic activities. [ABSTRACT FROM AUTHOR]