State University of Campinas (UNICAMP), Limeira, SP, Brazil.
Environ Monit Assess. 2023 Oct 16;195(11):1325. doi: 10.1007/s10661-023-11953-9.
Sewage sludge usage as agricultural soil amendment is a well-known practice employed worldwide. However, certain components may pose risks to the soil ecosystem. For a better verification of the potential adverse effects on the soil biota, biological assays have become an indispensable tool for an accurate understanding of the residue's behavior on soil, as well as its potential toxicity. Accordingly, to properly assess the effects of natural tropical soil (Oxisoil) amended with sewage sludge, we conducted toxicological tests with edaphic organisms (Enchytraeus crypticus and Folsomia candida) and microbial biomass (through respirometric assessment). Results indicate that E. crypticus and F. candida present similar reproduction sensitivity behavior to sewage sludge. For the microbiological analysis, the results suggest that microbial activity was stimulated by sludge application. For further evaluation of respiration of the microbial community and CO stabilization values behavior, Ford-Walford modeling was applied and presented limit values for sludge application in soil for 1.5 g kg and 15.0 g kg of, approximately, 55 mg and 88 mg, respectively. CO releases were faster and reached stability within 18 weeks for the soil with higher sludge content (15.0 g kg of dry soil). In contrast, CO releases were slower for the soil with lower sludge content (1.5 g kg of dry soil), and until the experiment's final period (21 weeks) respiration behavior did not reach stability. This study indicates that the stabilized sewage sludge, at the considered recommended application rate, presents a low toxicity risk for the studied bioindicators, being suitable for agricultural use.
污水污泥作为农业土壤改良剂的使用在全球范围内是一种众所周知的做法。然而，某些成分可能会对土壤生态系统构成风险。为了更好地验证对土壤生物区系的潜在不利影响，生物测定已成为准确了解残留物在土壤中的行为及其潜在毒性的不可或缺的工具。因此，为了正确评估添加污水污泥的天然热带土壤（Oxisoil）的影响，我们用土壤生物（真涡虫和华丽砂潜蝇）和微生物生物量（通过呼吸计评估）进行了毒理学测试。结果表明，真涡虫和华丽砂潜蝇对污水污泥的繁殖敏感性表现出相似的行为。对于微生物分析，结果表明，污泥的应用刺激了微生物活性。为了进一步评估微生物群落呼吸和 CO 稳定值行为，应用了 Ford-Walford 模型，并为污泥在土壤中的应用提出了限制值，对于约 55mg 和 88mg 的 1.5g/kg 和 15.0g/kg 的污泥应用，分别为 1.5g/kg 和 15.0g/kg 的污泥应用。对于污泥含量较高的土壤（15.0g/kg 干土），CO 的释放速度更快，在 18 周内达到稳定。相比之下，对于污泥含量较低的土壤（1.5g/kg 干土），CO 的释放速度较慢，直到实验的最后阶段（21 周），呼吸行为才未达到稳定。本研究表明，在考虑的推荐施用量下，稳定的污水污泥对所研究的生物指示剂具有低毒性风险，适合农业使用。
