Material flow analysis shows that soil is a key repository for silver (Ag) from (nano)silver-functionalized consumer products, but the potential effects of Ag toxicity, via Ag⁺ release, on soil microbial communities and their ecosystem services remains largely unknown. We examined the responses of multiple microbial biomarkers to increasing Ag⁺ doses (nine concentrations, 0–2000 mg kg^–1) in nine different soils representing a wide range of soil properties. Analyses included substrate-induced microbial respiration, nine different soil enzyme activities, and quantification of bacterial 16S-rRNA (SSU) and fungal intergenic spacer (ITS) copies. The resulting half-maximal effective concentrations (EC₅₀) for Ag ranged from ∼1 to >500 mg kg ^–1 and showed soil-specific responses, including some hormesis-type responses. Carbon cycle-associated enzyme activities (e.g., cellobiohydrolase, xylosidase, and α/β-glucosidase) responded similarly to Ag. Sulfatase and leucine–aminopeptidase activities (linked to the sulfur and nitrogen cycles) were the most sensitive to Ag. Total organic carbon, and to a lesser extent pH, were identified as potentially useful response predictors, but only for some biomarkers; this reflects the complexity of soil Ag chemistry. Our results show Ag toxicity is highly dependent on soil characteristics and the specific microbial parameter under investigation, but end point redundancies also indicated that representative parameters for key microbial functions can be identified for risk assessment purposes. Sulfatase activity may be an important Ag toxicity biomarker; its response was highly sensitive and not correlated with that of other biomarkers.

中文翻译：

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多种土壤微生物生物标志物的银毒性阈值

物质流分析表明，土壤是（纳米）银功能化消费产品中银（Ag）的重要储存库，但是通过Ag ⁺释放，Ag毒性对土壤微生物群落及其生态系统服务的潜在影响仍然未知。我们在代表多种土壤特性的九种不同土壤中研究了多种微生物生物标记物对增加的Ag ⁺剂量（9种浓度，0–2000 mg kg ^–1）的响应。分析包括底物诱导的微生物呼吸，九种不同的土壤酶活性以及细菌16S-rRNA（SSU）和真菌基因间隔子（ITS）拷贝的定量。产生的最大有效浓度的一半（EC ₅₀）对于Ag，范围从〜1到> 500 mg kg ^–1并显示了土壤特异性反应，包括一些兴奋剂型反应。碳循环相关的酶活性（例如，纤维二糖水解酶，木糖苷酶和α/β-葡萄糖苷酶）与Ag的反应相似。硫酸酯酶和亮氨酸-氨肽酶活性（与硫和氮循环有关）对银最敏感。总有机碳和较小的pH值被认为是潜在有用的反应预测因子，但仅用于某些生物标记物。这反映了土壤银化学的复杂性。我们的结果表明，Ag的毒性高度依赖于土壤特性和所研究的具体微生物参数，但终点冗余还表明，可以确定关键微生物功能的代表性参数以进行风险评估。硫酸酯酶活性可能是重要的Ag毒性生物标志物。