聚乳酸微塑料对淡水沉积物氮转化的影响  

Effect of polylactic acid microplastics on nitrogen conversion in freshwater sediments

作　　者：孙爱 冯琴霜 唐炳然 何强[1] 李宏[1] SUN Ai;FENG Qin-shuang;TANG Bing-ran;HE Qiang;LI Hong(Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment,Ministry of Education,College of Environment and Ecology,Chongqing University,Chongqing 400045,China)

机构地区：[1]重庆大学环境与生态学院,三峡库区生态环境教育部重点实验室,重庆400045

出　　处：《中国环境科学》2025年第4期2122-2134,共13页China Environmental Science

基　　金：国家自然科学基金资助项目(52370199);重庆市技术创新与应用发展专项重点项目(CSTB2023TIAD-KPX0092)。

摘　　要：为探究生物可降解聚乳酸微塑料(PLA-MPs)对淡水沉积物中氮转化的影响,构建了室内沉积物体系,分别向淡水沉积物中加入0(对照)、0.05%、0.5%、5%(质量比)的PLA-MPs,并在温度为25℃且光照强度为40μE/(m^(2)·s)的条件下培养45d.结果表明,PLA-MPs的加入导致体系中pH值和溶解氧(DO)浓度显著降低而溶解性有机碳(DOC)浓度显著升高(P<0.05),同时促进CO_(2)和CH4的生成.实验结束时,PLA-MPs的添加使NH_(4)^(+)-N的浓度降低,0.05%和0.5%PLA-MPs处理组,NO_(3)^(-)-N和TN浓度低于对照组(其上覆水TN浓度相比对照组分别下降了68.44%和61.83%).相反,5%PLA-MPs处理组出现TN积累(实验结束时上覆水TN浓度为5.71mg/L)且显著高于对照组(P<0.05).此外,0.5%和5%PLA-MPs处理组沉积物NO_(2)^(-)-N浓度降低并减少了N_(2)O的释放,而0.05%PLA-MPs则与之相反.添加PLA-MPs促进了固氮基因nifH和硝化基因amoA的表达,反硝化基因nirS和nosZ在0.05%和0.5%PLA-MPs处理组富集.而反硝化基因narG丰度仅在0.5%PLA-MPs处理组上调;5%PLA-MPs处理组中narG和nirS基因的丰度下调,nosZ基因的表达呈现先抑制后促进的趋势.研究结果表明,PLA-MPs的加入改变了上覆水及沉积物中的理化性质,促进了固氮和硝化,同时提供碳源增强0.05%和0.5%PLA-MPs处理下的反硝化从而脱氮,但在5%PLA-MPs处理中由于pH过低导致NO_(3)^(-)-N和NO_(2)^(-)-N的还原受到抑制进而使得TN积累.In order to explore the effect of biodegradable polylactic acid microplastics(PLA-MPs)on nitrogen conversion in sediments,a laboratory experimental sediment system was constructed,and 0(control),0.05%,0.5%and 5%(W/W)PLA-MPs were added to freshwater sediments,then the incubation experiment was performed for 45d at 25°C and light intensity of 40μE/(m^(2)·s).The concentration of dissolved organic carbon(DOC)decreased significantly and the concentration of dissolved organic carbon(DOC)increased significantly(P<0.05),and the formation of CO_(2) and CH4 was promoted.At the end of the experiment,the concentration of NH_(4)^(+)-N was reduced by the addition of PLA-MPs,and the concentrations of NO_(3)^(-)-N and TN in the 0.05%and 0.5%PLA-MPs treatment group were lower than those in the control group(compared with the control group,the TN concentrations of the overlying water decreased by 68.44%and 61.83%,respectively).On the contrary,the TN accumulation in the 5%PLA-MPs treatment group was recorded(the TN concentration in the overlying water was 5.71mg/L at the end of the experiment)and was significantly higher than that in the control group(P<0.05).The NO_(2)^(-)-N concentration in the 0.5%and 5%PLA-MPs treatment groups decreased and the release of N_(2)O was reduced,while the concentration of NO_(2)^(-)-N in the 0.05%and 5%PLA-MPs treatment groups was increased.The addition of PLA-MPs promoted the expression of nitrogen-fixing genes nifH and nitrification genes amoA,and the denitrification genes nirS and nosZ were enriched in the 0.05%and 0.5%PLA-MPs treatment groups.However,the abundance of denitrification gene narG was only up-regulated in the 0.5%PLA-MPs treatment group.The abundance of narG and nirS genes in the 5%PLA-MPs treatment group was down-regulated,and the expression of nosZ gene was inhibited but then promoted.The results show that PLA-MPs changes the properties of the overlying water and sediment,promotes nitrogen fixation and nitrification,and provide carbon source to enhance denitrification and denitr

关 键 词：聚乳酸塑料 氮转化 基因 沉积物 

分 类 号：X524[环境科学与工程—环境工程]