Application of manures to mitigate the harmful effects of electrokinetic remediation of heavy metals on soil microbial properties in polluted soils

Abstract

Ethylenediaminetetraacetic acid (EDTA) used with electrokinetic (EK) to remediate heavy metal-polluted soils is a toxic chelate for soil microorganisms. Therefore, this study aimed to evaluate the effects of alternative organic chelates to EDTA on improving the microbial properties of a heavy metal-polluted soil subjected to EK. Cow manure extract (CME), poultry manure extract (PME) and EDTA were applied to a lead (Pb) and zinc (Zn)-polluted calcareous soil which were subjected to two electric intensities (1.1 and 3.3 v/cm). Soil carbon pools, microbial activity, microbial abundance (e.g., fungal, actinomycetes and bacterial abundances) and diethylenetriaminepentaacetic acid (DTPA)-extractable Pb and Zn (available forms) were assessed in both cathodic and anodic soils. Applying the EK to soil decreased all the microbial variables in the cathodic and anodic soils in the absence or presence of chelates. Both CME and PME applied with two electric intensities decreased the negative effect of EK on soil microbial variables. The lowest values of soil microbial variables were observed when EK was combined with EDTA. The following order was observed in values of soil microbial variables after treating with EK and chelates: EK + CME or EK + PME > EK > EK + EDTA. The CME and PME could increase the concentrations of available Pb and Zn, although the increase was less than that of EDTA. Overall, despite increasing soil available Pb and Zn, the combination of EK with manures (CME or PME) mitigated the negative effects of using EK on soil microbial properties. This study suggested that the synthetic chelates such as EDTA could be replaced with manures to alleviate the environmental risks of EK application.

Differential magnitude of rhizosphere effects on soil aggregation at three stages of subtropical secondary forest successions

“…Soil pH may regulate soil aggregation through influencing plant growth, metal ion solubility, microbial activity, and clay dispersion (Haynes and Naidu 1998;Tahmasbian et al 2017). Consistently, our analyses reported that changes of soil pH were tightly related to variations of soil aggregate MWD (Table 2; Fig.…”

Changes in organic matter composition caused by EDTA washing of two soils contaminated with toxic metals

“…It is known that SOC decreases in long-term PTM-polluted soils (Viventsova et al 2005), but soil washing of contaminated soils may also have negative effects on SOM. Many studies have reported that after soil washing with Na 2 EDTA, the SOM did not change (Zupanc et al 2014;Tahmasbian et al 2017;Hosseini et al 2018). Sometimes, changes in SOC are difficult to investigate because these changes occur slowly and are relatively small compared to the vast SOC pool size, but some of the soil C fractions, such as humic acids, are more sensitive than the total SOC (Slepetiene et al 2011).…”

Changes in Organic Matter Composition Caused by EDTA Washing of two Soils Contaminated with Toxic Metals

“…It is known that SOC decreases in long-term PTM-polluted soils (Viventsova et al 2005), but soil washing of contaminated soils may also have negative effects on SOM. Many studies have reported that after soil washing with Na 2 EDTA the SOM did not change (Zupanc et al 2014; Jelusic et al 2014;Hu et al 2014;Tahmasbian et al 2017;Hosseini et al 2018). Sometimes changes in SOC are di cult to investigate because these changes occur slowly and are relatively small compared to the vast SOC pool size, but some of the soil C fractions, such as humic acids, are more sensitive than the total SOC (Slepetiene et al 2011).…”