含盐农村生活污水灌溉对土壤微生物的影响

为探究农村生活污水中盐分对土壤养分及细菌、真菌的影响，以《农田灌溉水质标准》(GB 5084—2021)中含盐浓度标准限值1 g/L为中位数，设置ZCK (0 g/L)、ZRW(raw water) (0.2 g/L)、ZW1 (0.5 g/L)、ZW2 (0.8 g/L)、ZW3 (1.2 g/L)、ZW4 (1.6 g/L)、ZW5 (2.0 g/L)共7个不同盐分梯度处理试验，并采用高通量测序技术分析土壤细菌及真菌群落微生物组成等. 结果表明:①土壤全盐量与土壤总氮、总磷、有机质含量均呈极显著负相关. ②灌溉盐度在0~2 g/L内，其中Na+含量与细菌Chao1指数、Shannon-Wiener指数均呈极显著负相关(P<0.01)，全盐量、Ca2+含量均与真菌Shannon-Wiener指数、Chao1指数、ACE指数呈显著正相关(P<0.05). ③整体来看，土壤细菌以变形菌门(Proteobacteria)、放线菌门(Actinobacteria)、酸杆菌门(Acidobacteria)、绿弯菌门(Chloroflexi)为优势菌门，以Arthrobacter、RB41、Gaiella、Rubrobacter、Sphingomonas为优势属. 土壤真菌以子囊菌门(Ascomycota)、被孢霉门(Mortierellomycota)、担子菌门(Basidiomycota)为优势菌门，以Mortierella、Neocosmospora、Metarhizium、Chaetomium为优势属. ④ Mg2+、Cl?为影响土壤40 cm深度处细菌优势菌门的主要盐基离子，其贡献率表现为Mg2+>Cl?，真菌优势菌门无显著影响因子. 研究显示:高含盐(>1 g/L)会显著降低土壤细菌的Shannon-Wiener指数，显著增加土壤真菌的Shannon-Wiener指数与Chao1指数，并且显著影响土壤细菌群落的相对丰度；含盐生活污水灌溉下土壤细菌功能预测代谢通路多为膜运输、氨基酸代谢、碳水化合物代谢；真菌功能预测多以腐生营养型与病例营养型为主. 

Effects of Rural Domestic Sewage Irrigation with Different Salinity on Soil Microorganisms

In order to explore the effect of salinity on soil nutrient bacteria and fungi under different saline rural sewage irrigation, this study uses the Salinity Standard for Agricultural Irrigation Water Quality (GB 5084-2021) as the median and sets seven different salinity gradients, namely ZCK (0 g/L), ZRW (Raw water) (0.2 g/L), ZW1 (0.5 g/L), ZW2 (0.8 g/L), ZW3 (1.2 g/L), ZW4 (1.6 g/L), ZW5 (2.0 g/L). High-throughput sequencing technologies were used to study the effect of salt on soil bacteria, fungi diversity and community composition structure. The results showed that: (1) Total salt in soil showed an significantly negative correlation with soil total nitrogen, total phosphorus and organic matter. (2) The irrigation salinity was within 0-2 g/L, and sodium ion was significantly negatively correlated with the bacterial Chao1 index and Shannon-Wiener index (P<0.01). Total salt and calcium ions were significantly positively correlated with fungal Shannon-Wiener index, Chao1 index and ACE index (P<0.05). Low salinity (<1 g/L) irrigation had no significant effect on soil bacteria Shannon-Wiener, Chao1 and ACE index. High salinity (>1 g/L) significantly reduced the Shannon-Wiener index of soil bacteria, and both high and low salinity concentrations had a significantly positive correlation with the Shannon-Wiener index of soil fungi (P<0.01). (3) Overall, soil bacteria were dominated by Proteobacteria, Actinobacteria, Acidobacteria, and Chloroflexi, and the dominant genera were Arthrobacter, RB41, Gaiella, Rubrobacter and Sphingomonas. Soil fungi were dominated by Ascomycota, Mortierellomycota and Basidiomycota and the dominant genera were Mortierella, Neocosmospora, Metarhizium and Chaetomium. Compared with low salinity irrigation, high salinity irrigation significantly increased the relative abundance of soil Actinobacteria, Gaiella and Sphingomonas, and significantly reduced the relative abundance of Acidobacteria, Rubrobacter and RB41. (4) Magnesium and chloride ions in soil were the main ions affecting the dominant phyla of bacteria in 40 cm soil, the contribution of magnesium ion was higher than chloride, and fungi dominant phyla had no significant impact factor. The research shows that: high salinity (>1 g/L) can significantly reduce Shannon-Wiener index of the soil bacteria. For the soil fungi, high salinity (>1 g/L) significantly increase Shannon-Wiener index and Chao1 index. Magnesium ions and chloride ions in base ions are the main factors affecting the dominant phyla of bacteria. High salinity (>1 g/L) of the sewage irrigation can significantly affect the relative abundance of soil microbial communities. The metabolic pathways of soil bacteria under saline domestic sewage irrigation are membrane transport, amino acid metabolism and carbohydrate metabolism. Fungal function prediction is mainly saprophytic and case trophic.