The influence and risk assessment of multiple pollutants on the bacterial and archaeal communities in agricultural lands with different climates and soil properties

Soil microorganisms play a vital role in maintaining the health of farmland ecosystems. The structures and functions of soil microorganisms are determined by the combined effects of natural and anthropogenic processes. To investigate the influence of anthropogenic contaminants on agricultural soil conditions and their impact on the prokaryote community, we collected agricultural soils from 3 types of villages (industrial, livestock breeding and agricultural) in four regions with typical geoclimatic features. We assessed the influences of changing environmental factors (climatic conditions, soil properties, heavy metal and organic pollutants) on soil bacterial and archaeal communities and their relative contributions. The results showed that differences in soil properties and contaminants between regions were more significant than those between villages of different types. Cu, Zn, Cd, antibiotics and phthalate esters were identified as major pollutants with medium to high level of risk in agricultural soils. The richness and biodiversity index showed no significant differences among regions, while dominant species and community composition were significantly correlated with changing environmental and pollution factors. Major environmental factors explained 65 % of the total variances based on the RDA analysis, with average temperature, precipitation and soil pH identified as the major factors shaping the prokaryote community. Combined pollution explained 20.14 % of total community variances, with moderate levels of pollution stresses being as significant as climatic and soil conditions to community composition. The correlation analysis indicated that different species respond differently to environmental factors. The major groups of functional microbes for N cycling, Nitrososphaeraceae and Nitrospiraceae, were found to be stressed by combined pollution. The Bacillaceae family showed a negative correlation to soil pH and a positive correlation to pollutants, suggesting their resistance to changing environments. The interaction among species and the correlation between environmental factors and multiple pollutants brought significant complexity to the assessment of cocontamination. In general, this study provides insights into the responses of agricultural soil microbial communities to multiple changing factors at a continental scale, which would substantially benefit the soil health assessment and management of agro-ecosystems under global environmental changes.