Heavy metal(loid)s transformation in dust at a lead smelting site

Emitted dust is the major contributor of heavy metal(loid)s in soils located near lead (Pb) smelters, but the mechanisms for transfer of the heavy metal(loid)s in dust are uncertain. The study systematically investigated the geochemical behaviors and liberation mechanisms of heavy metal(loid)s in this process. The results show that Pb, Zn, Cd, and As in two types of dust samples exceeded the allowable standards, and about 80% of Pb and Zn were present in mobile and bioavailable fractions. More than 70% of arsenic in bottom-blowing furnace dust existed in an acid-soluble fraction, while 60% of cadmium in reducing and fuming dust existed in the acid-soluble fraction. Pb isotope results showed that 97.12% of the Pb in the topsoil came from dust emitted during the smelting process. XRD and MLA results illustrated that PbSO₄, ZnSO₄, and CdSO₄ were the major minerals in the dust, while the mineral phases of the topsoil were mainly quartz, calcite, dolomite, and muscovite. Based on a combination of mineralogical investigations and geochemical modelling, our findings suggest that liberation of the Pb, Zn, and Cd was primarily dependent on sulfate minerals under acidic conditions, whereas the liberation of As was related to adsorption by iron hydroxide.

粉塵是鉛冶煉場地土壤重(類)金屬的來源之一，但粉塵中重(類)金屬的遷移轉化機制尚不明確。本文系統研究了此過程中重(類)金屬的地球化學行為和解離機制。實驗結果表明，兩類粉塵樣品中Pb、 Zn、Cd和As的總量和浸出均超過標準，其中，兩類粉塵中約有80%的Pb、Zn為生物可利用態,底吹 爐粉塵中70%以上的As 為弱酸提取態，而還原煙化爐粉塵弱酸提取態的重金屬為Cd，占比為60%。 Pb 同位素結果顯示，表土中97.12%的Pb 來自冶煉過程中排放的粉塵。XRD和MLA結果表明,粉塵 中的主要礦物為PbSO₄、ZnSO₄和CdSO₄，表土中的礦物主要是石英、方解石、白雲石和白雲母。利用 地球化學模型對主要礦物進行擬合發現,在酸性條件下，Pb、Zn和Cd的解離主要依賴於硫酸鹽礦物，而As的解離與氫氧化鐵的吸附作用有關。Copyright © 2024 Central South University.