Biological retention
The sub-function Biological retention relates to the ability of the soil biota in combination with chemical fixation and physical absorption to remove harmful substances from the soil water; these include excess nutrients, metals[1], micro-plastics[2] and pesticides[3]. However, in the case of pesticides, the metabolic products which are generated during the degradation process may in fact be more toxic than the original pesticide applied[3]. There are three key biological processes which support this sub-function: food web assimilation, which predominantly entails microbial assimilation of nutrients into microbial biomass, root foraging, which is focused on the uptake of nutrients for plant growth, and bio-accumulation, which Heikens et al. (2001) [1] related to the feeding strategy of taxonomic groups and the chemical conditions of the soil, such as pH.
[1] Heikens A. et al. 2001. Bioaccumulation of heavy metals in terrestrial invertebrates. Environmental Pollution 113: 385–393.
[2] Huerta Lwanga E et al. 2018. Decay of low-density polyethylene by bacteria extracted from earthworm’s guts: A potential for soil restoration. Science of The Total Environment 624: 753–757.
[3] Fierer N et al. 2021. How microbes can, and cannot, be used to assess soil health. Soil Biology and Biochemistry 153: 108111.