Response of Enchytraeus crypticus worms to high metal levels in tropical soils polluted by copper smelting

Abstract

Tropical soils from the vicinity of the Mufulira copper smelter (Zambian Copperbelt) were found to contain high levels of metals, particularly in the upper parts of soil horizons. Metal concentrations varied within the ranges: 37-8980 mg Cu/kg, 3-46 mg Co/kg, b 2.5-42 mg Pb/kg, and 16-83 mg Zn/kg. The EDTA extractions indicated that a considerable percentage of the metals were bound in the "labile" fractions of the soil (up to 55% of total Cu concentration, 36% Co, 41% Pb, 30% Zn). The mineralogical investigation of the heavy mineral fraction of the most contaminated soil showed that the Cu is mainly present as Cu-(Fe) sulphides (chalcocite, chalcopyrite), metallic Cu, complex Cu-(Fe) oxides, and Cu-bearing sulphates. To determine the toxicity of these soils, we adopted a standardized OECD reproduction test using Enchytraeus crypticus. The number of reproduced enchytraeids correlated negatively with total Cu and Co concentrations (r = −0.97 and −0.94 at p b 0.001, respectively), and EDTA-extractable Cu (r = −0.89, p b 0.001); whereas no effects of the soil properties (pH, CEC, C org ) were observed. No reproduction was possible in soils with Cu levels N5000 mg/kg. Median effect concentration (EC50) was calculated for total Cu concentration, and corresponded to 351 mg/kg.

Metal bioavailability to Eisenia fetida through copper mine dwelling animal and plant litter, a new challenge on contaminated environment remediation

“…The exchangeable base cations such as calcium (Ca 2þ ), magnesium (Mg 2þ ), sodium (Na þ ) and potassium (K þ ) are associated to effect the CEC values of soil (Rayment and Higginson, 1992) and our earlier study shows a high level of calcium and sodium in mine soil at the same location (Nirola et al, 2015). However, our present study does not show much effect of pH and CEC on earthworm metal uptake, a finding similar to Konecny et al, 2014. With regards to higher electrical conductivity (EC) as in treatments 3 and 4 (CHF and MHF respectively), soil salinity seems to have facilitated bioavailability of metals (Owojori et al, 2008).…”

“…In a study of Konecny et al, 2014 on Enchytraeus crypticus, there was no reproduction in soils with Cu levels >5000 mg/kg. Moreover, the reproduction effect concentration (EC50) was 351 mg/kg, a value within the range of our treatments.…”

Thresholds of arsenic toxicity to Eisenia fetida in field-collected agricultural soils exposed to copper mining activities in Chile

“…Despite of the above-mentioned difficulties in interpreting the results of earthworm tests in field-collected soils, Konečný et al (2014) were successful in determining a metal of prime concern and metals with additional toxic effects to earthworms, in soils containing various metals. Likewise, Nahmani et al (2007a) identified metals that caused toxicity to earthworms exposed to soils containing various metals, based on analysis of metal concentrations in earthworm tissues.…”

REVIEW: Potential roles of soil fauna in improving the efficiency of rain gardens used as natural stormwater treatment systems

“…; Konečný et al . ). Soil fauna may assist with pathogen removal, but their role has not yet been evaluated in these systems.…”