The Effects of Heavy Metal Pollution on Collembola in Urban Soils and Associated Recovery Using Biochar Remediation: A Review

Heavy metal pollution in urban soil continues to be a global issue that poses a serious hazard to invertebrates and human lives through oral ingestion and inhalation of soil particles. Though the toxicity of several heavy metals on invertebrates like Collembola has been studied, lead (Pb) and cadmium (Cd) have been extensively studied due to their high toxicity to collembolans. As a ubiquitous soil organism all over the world, collembolans have been used as a model species to study the effects of heavy metals on invertebrate communities. To reduce the effects of heavy metals on ecosystem functions, biotic and abiotic measures have been used for heavy metal remediation; biochar seems to be the most effective approach that not only increases the physical absorption of heavy metals but also indirectly benefits soil organisms. In this study, we briefly reviewed the application of biochar in Pb and Cd polluted soil and showed its potential in soil remediation. Furthermore, we outlined the potentially toxic effects of Pb- and Cd-polluted urban soil on the collembolan species. We searched peer-reviewed publications that investigated: (1) the level of Pb and Cd contamination on urban soil in different cities around the world; and (2) the different sources of Pb and Cd as well as factors influencing their toxicity to collembolan communities. The obtained information offers new perspectives on the interactions and effects between collembolans, Pb, and Cd, and their remediation in urban soils.