Speciation and spatial distribution of Cr in chromite ore processing residue site,Yunnan,China

Remediation of COPR sites requires the key information including chromium oxidation, speciation and spatial distribution. Samples were gathered from a COPR site in Luliang County in Qujing, Yunnan Province of China. The total Cr, Cr(VI) and chromium species were investigated. Results indicated the concentration of total Cr was between 110.5 and 21,774 mg/kg, and the concentration of Cr(VI) was between 0.1 and 1075 mg/kg. The map of total-Cr and ratio of Cr(VI)/total-Cr(%) showed that the maximum of total-Cr and Cr(VI) appeared in the layers near the surface. In the horizontal direction, the pollution was more serious in the middle and southeast part than that in the west. Additionally, acid extractable chromium increased in the layers at depth from-0.3 to-2.0 m, and it decreased in the deeper layers. There was a trend that the movable Cr(VI) migrated to the deeper layers, and then it turned into Cr(III). Water played an important role for the Cr distribution. Cr(VI) in COPR released to the soil solution after rainfall, and then gravity led the solution down to the deeper layers. After repeated rainfall and leaching,Cr(VI) moved to the deeper soil layers. Due to capillarity and evaporation, Cr(VI) migrated and was enriched at thesurface layer. Therefore, measures on controlling water movement should be taken in the remediation of the COPR site.

Size distribution and source of heavy metals in particulate matter on the lead and zinc smelting affected area

In order to understand the size distribution and the main kind of heavy metals in particulate matter on the lead and zinc smelting affected area, particulate matter （PM） and the source samples were collected in Zhuzhou, Hunan Province from December 2011 to January 2012 and the results were discussed and interpreted. Atmospheric particles were collected with different sizes by a cascade impactor. The concentrations of heavy metals in atmospheric particles of different sizes, collected from the air and from factories, were measured using an inductively coupled plasma mass spectrometry （ICP-MS）. The results indicated that the average concentration of PM, chromium （Cr）, arsenic （As）, cadmium （Cd） and lead （Pb） in PM was 177.3 ± 33.2 μg/m^3, 37.3 ± 8.8 ng/m^3, 17.3 ± 8.1 ng/m^3, 4.8 ± 3.1 ng/m^3 and 141.6 ± 49.1 ng/m^3, respectively. The size distribution of PM displayed a bimodal distribution; the maximum PM size distribution was at 1.1-2.1 μm, followed by 9-10 μm. The size distribution of As, cd and Pb in PM was similar to the distribution of the PM mass, with peaks observed at the range of 1.1-2.1 μm and 9-10 μm ranges while for Cr, only a single-mode at 4.7-5.8 μm was observed. PM （64.7%, As （72.5%）, cd （72.2%） and Pb （75.8%） were associated with the fine mode below 2.1 μm, respectively, while Cr （46.6%） was associated with the coarse mode. The size distribution characteristics, enrichment factor, correlation coefficient values, source information and the analysis of source samples showed that As, Cd and Pb in PM were the typical heavy metal in lead and zinc smelting affected areas, which originated mainly from lead and zinc smelting sources.