Heavy metal residues, releases and food health risks between the two main crayfish culturing models: Rice-crayfish coculture system versus crayfish intensive culture system

High-density culturing with excessive feeding of commercial feed has caused heavy metals pollution to agricultural production system. In this study, the dynamic changes and transfer of heavy metals in rice-crayfish coculture system (RCCS) and crayfish intensive culture system (CICS) within a completed culture cycle were systematically quantified. Our results showed that Cd in feed represented more than 50% of the total Cd input, and the inputs of As and Cr were mainly from irrigation. The residues of As and Pb in RCCS were slightly higher than those in CICS, while the residues of Cd and Cr in RCCS were far fewer than those in CICS. Moreover, the metal pollution index in CICS was 0.781, while it was 0.543 in the RCCS. Furthermore, a large proportion of the Cd and Pb in CICS was released into the external environment through drainage. Notably, the absorption and solidification of heavy metals by straw did not increase the residues of As and Pb in the major components of RCCS in the second year. Compared to CICS, RCCS did not produce many heavy metal residues or cause heavy metal discharge pressure on the external environment, and its food product had a low risk of heavy metal contamination.

Automated summary

Excessive feeding and commercial feed have led to heavy metal pollution in the agricultural production system. This study systematically quantified the dynamic changes and transfer of heavy metals in a rice-crayfish coculture system (RCCS) and a crayfish intensive culture system (CICS). The results showed that RCCS had lower residues of cadmium and chromium compared to CICS, while residues of arsenic and lead were slightly higher. RCCS produced fewer heavy metal residues and had lower heavy metal discharge pressure on the external environment compared to CICS.