The effect of biochar and compost from urban organic waste on plant biomass and properties of an artificially copper polluted soil

Soil contamination with copper is a global issue, in particular in soils with a history of fertilizers, fungicides or municipal waste amendment. Several remediation techniques have been investigated to reduce the environmental impact of Cu-contaminated soil, including the use of organic amendments such as composts and biochars, which can bound part of the soluble fraction of the metal. The objective of this work is to study the effect of biochar and biochar plus compost addition on copper mobility, soil microbial biomass and growth of different plant species following remediation of a soil spiked with copper (1000 mg Cu kg−1). The contaminated soil was treated with 10 wt% of biochar or biochar plus compost. Different plant species (mustard, cress and ryegrass) were grown in the soil during 4 weeks. A significant reduction on the mobile form of Cu was observed in soils treated with biochar and biochar plus compost. The highest microbial biomass values were obtained in samples treated with biochar plus compost. After cress growth, the microbial biomass of soil treated with biochar plus compost was similar to that of non-polluted soil. The germination test showed increased root length in the amended soils compared to the contaminated soils. With respect to biomass growth of vegetable species in copper polluted soil, only ryegrass presented a satisfactory growth in the contaminated soil without the biochar treatment. For mustard and cress, biomass growth was only observed following biochar addition.