Biogenic formation of non-extractable residues from pesticides in soil

在土壤中有机化学物质的微生物循环过程中，经常形成不可提取残留物。对NER形成的研究通常是用放射性同位素标记的示踪化合物进行的，仅限于局部定位和定量分析，但它们的化学成分是未知的。最近，我们可以证明2,4-二氯苯氧乙酸和布洛芬在土壤微生物周转过程中几乎所有的NER都来自微生物生物量，因为降解细菌利用污染物碳进行生物量合成。它们的细胞碎片随后在土壤有机质（SOM）中稳定形成生物NER （bioNER）。目前尚不清楚bioNER是否也在其他结构不同的化合物类别的有机污染物的生物降解过程中形成。因此，农业土壤将与五类常用和新兴农药的标记化合物孵育：有机磷、苯脲、三嗪酮、苯并噻二嗪和芳氧苯氧丙酸。将在活体和非活体SOM池中监测标签的命运，并在较长时间内量化每种化合物的bioNER的形成。此外，从长期渗滤仪研究中获得的含有14c标记的农药残留（如三嗪、苯并噻唑和苯氧丙酸组）的土壤样本也将被分析以确定生物离子的形成。将对结果进行总结，以确定生物有机分子形成所需的微生物代谢条件，并发展一个扩展的风险评估概念，包括土壤中生物有机分子的形成。

During microbial turnover of organic chemicals in soil, non-extractable residues (NER) are formed frequently. Studies on NER formation usually performed with radioisotope labelled tracer compounds are limited to localisation and quantitative analyses but their chemical composition is left unknown. Recently, we could show for 2,4-dichlorophenoxyacetic acid and ibuprofen that during microbial turnover in soil nearly all NER were derived from microbial biomass, since degrading bacteria use the pollutant carbon for their biomass synthesis. Their cell debris is subsequently stabilised within soil organic matter (SOM) forming biogenic NER (bioNER). It is still unknown whether bioNER are also formed during biodegradation of other, structurally different compound classes of organic contaminants. Therefore, agricultural soil will be incubated with labelled compounds of five classes of commonly used and emerging pesticides: organophosphate, phenylurea, triazinone, benzothiadiazine and aryloxyphenoxypropionic acid. The fate of the label will be monitored in both living and non-living SOM pools and the formation of bioNER will be quantified for each compound over extended periods of time. In addition, soil samples from long-term lysimeter studies with 14C-labelled pesticide residues (e.g. triazine, benzothiazole and phenoxypropionic acid group) will be also analysed for bioNER formation. The results will be summarised to identify the metabolic conditions of microorganisms needed for bioNER formation and to develop an extended concept of risk assessment including bioNER formation in soils.