黄土高原油井开发迹地自然恢复过程土壤酶活性及其化学计量特征

Soil enzyme activity and its stoichiometric characteristics during natural recovery of oil well development site in the Loess Plateau

胞外酶活性是土壤中石油污染物降解的关键环节,也是土壤微生物养分利用的重要指标.为理解石油开发区土壤自然恢复过程中微生物胞外酶介导的生物地球化学循环机制,以黄土高原石油开发形成的油井迹地为研究对象,采集不同自然恢复年限油井迹地土壤,测定土壤的理化性质和β-1,4-葡萄糖苷酶(BG)、亮氨酸氨基肽酶(LAP)、β-1,4-N-乙酰氨基葡萄糖苷酶(NAG)和碱性磷酸酶(ALP)等4种酶活性,分析土壤酶活性和酶计量比的变化及其关键的环境驱动因子.结果表明:(1)土壤总石油烃从恢复1年到恢复20年显著下降了54%;随着恢复年限增加,土壤pH、容重显著下降,而土壤有机碳、全氮、硝态氮显著升高,铵态氮、全磷变化不显著;土壤碳磷比和氮磷比显著升高但碳氮比显著下降.(2)土壤BG活性、酶活性碳氮比和碳磷比显著下降,而NAG、LAP、ALP活性和酶活性氮磷比显著升高;不同恢复年限酶计量学的向量长度和向量角度分别为1.87-1.19°和53.64-47.93°,均随恢复年限显著下降,表明土壤微生物受碳和磷限制程度逐渐减弱.(3)土壤总石油烃、碳氮含量、pH、容重等指标对土壤酶活性及其计量学特征有显著影响,尤其是总石油烃对酶活性和酶计量学变异的解释率分别达到63.7%和79.8%.综上所述,油井迹地土壤自然恢复过程中石油污染物含量显著降低,碳、氮养分不断积累,土壤微生物养分限制状况有所缓解.(图4表3参49)

Extracellular enzyme activity is key for the degradation of petroleum pollutants in the soil and an important indicator of microbial nutrient utilization.To understand the biogeochemical cycle mechanism,mediated by microbial extracellular enzymes,in the natural restoration soil from oil development areas,this study was conducted on oil well development sites,formed by petroleum exploitation,in the Loess Plateau in China.Soil samples were collected from oil well development sites with distinct(natural)recovery years,and the soil physicochemical properties and activities of four soil enzymes were measured,namelyβ-1,4-glucosidase(BG),leucine aminopeptidase(LAP),β-1,4-N-acetylaminoglucosidase(NAG),and alkaline phosphatase(ALP).Besides the changes in soil enzyme activity and enzyme ratio,their key environmental drivers were also explored.The results showed that(1)the total petroleum hydrocarbons(TPH)in soil decreased significantly,by 54%,from 1 year of recovery to 20 years.With increasing restoration years,soil pH and bulk density decreased,whereas soil organic carbon,total nitrogen,and nitrate nitrogen increased.Although ammonium nitrogen and total phosphorus did not change significantly,the soil C:P and N:P ratios increased significantly,whereas the C:N ratio decreased.Additionally,(2)Soil BG,enzyme C:N ratio,and enzyme C:P ratios decreased,whereas the enzymatic activities of NAG,LAP,and ALP,and enzyme N:P ratio increased significantly.The vector length and angle of the enzyme stoichiometric ratio in different recovery years were 1.87-1.19°and 53.64-47.93°,respectively,decreasing significantly with the increase in recovery years,which might suggest that soil microorganisms are progressively less limited by carbon and phosphorus.(3)The soil TPH,carbon and nitrogen contents,pH,and bulk density showed significant effects on soil enzyme activity and enzymatic stoichiometric ratio.The explanatory rates of TPH on enzyme activity and enzyme stoichiometric ratio variation were 63.7%and 79.8%,respectively.In conclusion,the petroleum pollutant content decreased significantly over the years,while carbon and nitrogen accumulated.Furthermore,the limitation of soil microbial nutrients was alleviated during the natural recovery of the soils in oil well development sites.