Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400045, PR China.
Key Laboratory of Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing 400045, PR China.
Sci Total Environ. 2018 Sep 15;636:1408-1415. doi: 10.1016/j.scitotenv.2018.04.378. Epub 2018 May 5.
The fungicide chlorothalonil (CHT) has been widely used in the tea orchard due to its high-efficiency and sterilization. It has been reported that repeated application of CHT inhibits soil nitrification process. However, the acute impact of CHT on soil denitrification and associated NO emissions is unclear. This study evaluated nitrate (NO) removal, denitrifying gene abundance and denitrifying enzyme activity of tea orchard soil after a 72-h-exposure to CHT. It was found that increasing CHT from 5 to 25 mg kg suppressed the NO removal efficiency from 74.6% to 54.1%, but increased NO emissions from 23.1% to 94.8%. Following treatment with 25 mg kg of CHT, the abundances of the nirK, nirS and nosZ genes were reduced by 31.6%, 22.1%, and 50.7%, respectively. Alternatively, the declines of the electron transport system activity (ETSA) value and adenosine triphosphate (ATP) content suggested that CHT had an inhibitory effect on microbial metabolism. Enzyme activity studies further revealed that the decrease of nitrate reductase (NAR), nitrite reductase (NIR) and nitric oxide reductase (NOR) activities was the main reason for the suppression of denitrification by CHT. Furthermore, positive correlations were observed between denitrifying reductase activity and the intracellular metabolism, indicating that the decrease in microbial metabolism should also be responsible for the inhibitory effect of CHT on the denitrifying process. Overall, it was found that the acute exposure of soil to CHT could inhibit the denitrification process and significantly increase NO emissions, which might result in destruction of the soil nitrogen cycle and exacerbation of global warming.
杀菌剂百菌清（CHT）由于其高效和杀菌作用而被广泛应用于茶园。据报道，重复使用 CHT 会抑制土壤硝化过程。然而，CHT 对土壤反硝化及其相关的 NO 排放的急性影响尚不清楚。本研究评估了 CHT 暴露 72 小时后茶园土壤的硝酸盐（NO）去除、反硝化基因丰度和反硝化酶活性。结果发现，CHT 浓度从 5 增加到 25mg/kg 会抑制 NO 去除效率从 74.6%降至 54.1%，但会使 NO 排放从 23.1%增加到 94.8%。用 25mg/kg 的 CHT 处理后，nirK、nirS 和 nosZ 基因的丰度分别降低了 31.6%、22.1%和 50.7%。此外，电子传递系统活性（ETSA）值和三磷酸腺苷（ATP）含量的下降表明 CHT 对微生物代谢有抑制作用。酶活性研究进一步表明，硝酸盐还原酶（NAR）、亚硝酸盐还原酶（NIR）和一氧化氮还原酶（NOR）活性的降低是 CHT 抑制反硝化作用的主要原因。此外，反硝化还原酶活性与细胞内代谢呈正相关，表明微生物代谢的降低也应是 CHT 抑制反硝化过程的原因之一。总的来说，发现土壤中 CHT 的急性暴露会抑制反硝化过程并显著增加 NO 排放，这可能导致土壤氮循环的破坏和全球变暖的加剧。
