Environmental risks of organic fertilizer with increased heavy metals (Cu and Zn) to aquatic ecosystems adjacent to farmland in the northern biosphere of Japan

• Published in: The Science of the total environment Vol. 884; p. 163861
• Main Authors: Nakamaru, Yasuo Mitsui, Matsuda, Retsushi, Sonoda, Takeshi
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01-08-2023
• Subjects: Composted sewage sludge; Copper; Distribution coefficient; Heavy metal contamination; Leachate; Zinc; SOM; CSS; Heavy metal contamination; Distribution coefficient; Copper; PM; Leachate; Zinc; Composted sewage sludge
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2023.163861

In Abashiri, Hokkaido, northern Japan, composted sewage sludge (CSS) containing a large amount of zinc (Zn) and copper (Cu) is used as fertilizer in agriculture. The local environmental risks of Cu and Zn from such organic fertilizers were studied. The study area, especially the brackish lakes located near the farmlands, is important for inland fisheries. The risks posed by heavy metals to the brackish-water bivalve, Corbicula japonica, was therefore investigated as an example. First, the long-term effect of CSS application in agricultural fields was monitored. Second, using pot cultivation, factors influencing Cu and Zn availability in the presence of organic fertilizers were evaluated under different scenarios of SOM content. In addition, the mobility and availability of Cu and Zn in organic fertilizers were evaluated in a field experiment. In the pot cultivation, both organic and chemical fertilizers increased the availability of Cu and Zn with a decrease in pH, possibly caused by nitrification. However, this decrease in pH was inhibited by higher SOM content, i.e. SOM mitigated the heavy metal risk from organic fertilizer. In the field experiment, potato (Solanum tuberosum L.) was cultivated using CSS and pig manure (PM). As observed in the pot cultivation, the applied chemical and organic fertilizers increased the soil-soluble and 0.1 N HCl-extractable Zn with increased nitrate. Considering the habitat and the LC50 values of C. japonica that were lower than the concentration of Cu and Zn in the soil solution phase, there is no significant risk from heavy metals in the organic fertilizers. However, the Kd values for Zn were significantly lower for CSS or the PM-applied plot in the field experiment soil, indicating a higher Zn desorption rate from organically fertilized soil particles. The potential risk of heavy metals from agricultural lands under changing climate conditions must therefore be monitored carefully.
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•CSS with high Zn and Cu, used as fertilizer, poses environmental risks.•Risks from CSS were studied using pot cultivation and field experiments.•Availability of Cu, Zn can be affected by N mineralization and resulting pH decrease.•Risks from Cu, Zn in CSS can be mitigated by high SOM content soil.•Potential risks of heavy metals from agricultural land must be monitored carefully.