Heavy metal distribution profiles in soil and groundwater near pig farms in China

Intensive pig farming relies on the extensive use of heavy metal additions to feed and this poses a threat to the environment that receives the manure. Pig manure is still continually disposed of improperly and many farms do not possess waste treatment facilities. In this study, two typical pig farms that lacked waste treatment facilities in Beijing, northern China, and two in Hefei, southern China were selected to determine the distributions of Cu, Zn, and Cd in the environment near the farms. Our results indicated that Cu, Zn, and Cd levels were 1.28-36.60, 1.02-19.49, and 1.04-219.56 times their local background values, respectively. The order of frequency of in-dividual metals that could potentially pose ecological risks to soils was Cd > Cu > Zn. All four pig farms were rated as possessing considerable or high risk according to the average contamination degree (C-d). Our RDA result indicated that the heavy metals did not show a significant correlation with the bacterial community composition in the soils. Additionally, groundwater near these pig farms was safe for drinking. Our results indicated that detailed investigations are necessary to determine the extent of heavy metal pollution in soils adjacent to pig farms that lack proper wastewater treatment facilities. This study offers further and deeper insights into the heavy metal pollution from intensive pig farms to the adjacent soils.

Automated summary

Intensive pig farming, which heavily relies on the use of heavy metal additives, poses a threat to the environment. This study analyzed the distributions of Cu, Zn, and Cd near pig farms in Beijing and Hefei, China. The results showed elevated levels of these heavy metals compared to local background values, indicating potential ecological risks. However, no significant correlation was found between heavy metals and bacterial community composition in the soils. The groundwater near these farms was deemed safe for drinking.