Effects of modified Pb-, Zn-, and Cd- availability on the microbial communities and on the degradation of isoproturon in a heavy metal contaminated soil

The effects of modified heavy metal (HM) availability on the microbial community structure and on the microbe-mediated degradation of herbicide isoproturon (IPU) were evaluated in soil with a long-term HM contamination. The fate of ¹⁴C-ring labelled IPU was investigated for over 60 days under controlled microcosm conditions. Phosphate mineral apatite and a water solution of Pb, Zn, and Cd salts were previously homogeneously mixed into the soil material to reduce and to increase the proportion of bioavailable HM, respectively. The availability of Pb, Zn, and Cd was determined by HM fractionation and plant uptake 110 days after the addition of amendments, shortly before IPU addition. Apatite treatment reduced the availability of HM, but did not affect the microbial biomass and the microbial community structure on the genotype level (total soil DNA-RAPD). However, it changed the microbial community structure on the phenotype level, based on the composition of phospholipid fatty acids (PLFA) at the end of the degradation experiment. The degradation of IPU did not change. In contrast to apatite treatment, HM supplementation increased the bioavailability of Pb, Zn and Cd, which resulted in biomass reduction and changes of microbial community structure on the genotypic (total soil DNA-RAPD) and phenotypic (PLFA) level. Increased bioavailability of HM also significantly reduced the rate of IPU degradation and mineralisation. The total mineralisation over a period of 60 days decreased from 12 to 5% of initial ¹⁴C. Increased HM bioavailability did not influence the degradation pathways and kinetics of IPU.     

EDTA Leaching of Cu Contaminated Soils Using Ozone/UV for Treatment and Reuse of Washing Solution in a Closed Loop

Ozone and UV irradiation were used for oxidative decomposition of EDTA-Cu complexes in washing solution obtained during multi-step leaching of Cu (344,1?±?36.5 mg kg^?1) contaminated vineyard soil with EDTA as a chelant. The released Cu was absorbed from the washing solution on a commercial mixture of metal absorbing minerals, and the treated washing solution then reused for removal of soil residual Cu-EDTA complexes in a closed-loop process. Six consecutive leaching steps (6?×?2.5 mmol kg^?1 of EDTA) removed 38.8 % of Cu from soils, and reduced Cu soil mobility, determined using the toxicity characteristic leaching test (TCLP), by 28.5%. The final washing solution obtained after soil remediation was colourless, with a pH close to neutral (7.5?±?0.2) and with low concentrations of Cu and EDTA (0.51?±?0.22 mg L^?1 and 0.083 mM, respectively). The proposed remediation method has therefore potential not just to recycle and save process water, but also not to produce toxic wastewaters. Soil treatment did not substantially alter the soil properties determined by pedological analysis, and had relatively little impact on soil hydraulic conductivity and soil water sorption capacity.     

Does ivermectin attract earthworms?

Purpose  

Changes in the behavior of earthworms (for example avoidance of a particular substrate) can influence the soil ecosystem. Our aim was to determine whether the earthworms Eisenia fetida and Lumbricus terrestris are able to avoid ivermectin (a veterinary endectocide belonging to the avermectins). A standard avoidance test with earthworms was conducted using standardized Lufa 2.3 soil (Speyer, Germany) and sandy soil provided by Cinkarna Celje (Slovenia).