Abstract
The study outlines a novel and traceable procedure for inactivating zinc polluted soil (an Anthrosols) adjacent to a former zinc (Zn) ore mine “Orzel Biały” in Bytom (Poland), where the total content of Zn amounted to 3988.0 mg kg−1. This pollution level initiated an inactivation process involving two natural mineral sorbents, i.e., zeolite (Z) and bentonite (B), as well as their five blends (ZeoBen) expressed as ZB: (1) ZB15/85, (2) ZB30/70, (3) ZB50/50, (4) ZB70/30 and (5) ZB85/15. Next, phosphorus (P) as triple superphosphate (TSP, 46% P2O5) was added to individual ZB at rates: 0.25%, 0.5%, 1.0% and 2.0%. All sorbents were added to the Zn polluted soil at 0%, 0.25%, 0.5%, 1.0% and 2.0% (dry weight basis). Treatments (1.0 kg of Zn-polluted soil with ZB sorbents) were aged for 115 days. Data revealed that ZB85/15 with prevailing zeolite caused a Znact inactivation of 66–71%, while zeolite induced 54% and 47% for bentonite. Reactive zinc (Znreac) decreased much more (20%) when zeolite was incorporated at the rate 2.5 g·kg−1 soil, and bentonite was (10%) at the same rate. The application of the sorbent ZB50/50 enriched with triple superphosphate (TSP) raised the stabilization degree for both Zn fractions. The efficiency was significant at the TSP rate of 2.0% of the sorbent and at least the sorbent +TSP of 10 g·kg−1 soil. The cation exchange capacity (CEC) of about 2 cmol(+)·kg−1 controlled the activity −0.50 mmol·dm−3 of either γZnreac or γZnact, hence a very low zinc ionic activity. The use of mineral blends with higher sharing of zeolite is promising for remediating metal-polluted lands in the case of zinc.
Highlights
IntroductionAccording to the United States Environmental Protection Agency (USEPA) [1], natural attenuation is the “use of natural processes to contain the spread of the contamination from chemical spills and reduce the concentration and amount of pollutants at contaminated sites”
The remediation effects of the tested sorbents, i.e., zeolite (Z), bentonite (B) and their blends (ZB): ZeoBen 15/85 (ZB15/85), ZeoBen 30/70 (ZB30/70), ZeoBen 50/50 (ZB50/50), ZeoBen 70/30 (ZB70/30), ZeoBen 85/15 (ZB85/15) (Table 2) were evaluated on the basis of geochemical changes of two Zn forms, (1) active (Znact ), i.e., water-soluble and (2) reactive (Znreac ), for the fractions extracted with 0.11 mole CH3 COOH dm−3
That changes observed with the Znreac fractions may be describing the capacity of the sorbents-treated Zn-polluted soil for inactivating Zn
Summary
According to the United States Environmental Protection Agency (USEPA) [1], natural attenuation is the “use of natural processes to contain the spread of the contamination from chemical spills and reduce the concentration and amount of pollutants at contaminated sites”. It can be termed as intrinsic remediation, bioattenuation and intrinsic bioremediation. In this case, the contaminants are left on site and the naturally occurring processes are left to clean up the site [2]. Natural attenuation may be used at numerous sites, it rarely can be used as a sole treatment process [3]
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