[Show abstract][Hide abstract] ABSTRACT: Biosolids have been used as amendments on mine degraded soils for in situ immobilization of metals, neutralization, and improvement of nutritional, microbiological, and physical characteristics to reestablish a self-sustaining plant community. Fresh and air-dried biosolids have been used but dried ones are preferred as they are cheaper to transport, contain less pathogens and are much easier to handle. The same efficacy has been assumed for both biosolids. The study evaluated the effects of fresh and air-dried biosolids on physical, chemical and microbiological characteristics of an acidic and metal/As-rich soil of the Puchuncaví valley, central Chile, and on plant yield under laboratory conditions. Two doses of each biosolids were used (50 and 100 ton ha-1, dry weight). Fresh and air-dried biosolids similarly increased organic matter, total nitrogen (N) and available N and phosphorous contents of study soil. However, air-dried biosolids exhibited lower field capacity and higher wilting point, salinity, higher levels of dissolved organic carbon, concentrations of total dissolved copper and zinc, and lower activity of free Cu2+ ions in pore water. Basal respiration was significantly increased by incorporation of biosolids into soils, irrespective of being fresh or air-dried ones. In terms of aerial plant productivity, fresh biosolids and low doses of air-dried biosolids significantly increased this characteristic. However, high doses of air-dried biosolids limited aerial biomass and root cover, probably due to soil salinity and water stress. Therefore, fresh biosolids are suggested for remediation of this mine degraded soils.
[Show abstract][Hide abstract] ABSTRACT: Acidic and metal(oid)-rich topsoils resulted after 34 years of continuous operations of a copper smelter in the Puchuncaví valley, central Chile. Currently, large-scale remediation actions for simultaneous in situ immobilization of metals and As are needed to reduce environmental risks of polluted soils. Aided phytostabilization is a cost-effective alternative, but adequate local available soil amendments have to be identified and management options have to be defined.
Efficacy of seashell grit (SG), biosolids (B), natural zeolite (Z), and iron-activated zeolite (AZ), either alone or in mixtures, was evaluated for reducing metal (Cu and Zn) and As solubilization in polluted soils under laboratory conditions. Perennial ryegrass was used to test phytotoxicity of experimental substrates.
Soil neutralization to a pH of 6.5 with SG, with or without incorporation of AZ, significantly reduces metal (Cu and Zn) solubilization without affecting As solubilization in soil pore water; furthermore, it eliminates phytotoxicity and excessive metal(oid) accumulation in aerial plant tissues. Addition of B or Z to SG-amended soil does not further reduce metal solubilization into soil pore water, but increase As solubilization due to excessive soil neutralization (pH > 6.5); however, no significant As increase occurs in aerial plant tissues.
Simultaneous in situ immobilization of metal(oid) in acidic topsoils is possible through aided phytostabilization.
Full-text · Article · Nov 2011 · Environmental Science and Pollution Research