Investigation And Study Of The Soil And Groundwater Contamination Of Service Stations In Different Parts Of China

Soil and groundwater pollution is a major environmental issue facing the world,which not only seriously affects soil quality and land productivity,but also threatens food security,human health and ecological safety.Therefore,environmental remediation has become a key area of science and technology in many countries and regions as well as a necessary technological means to remove contaminants and recover soil ecological function.Gas station pollution is an atypical but widespread problem existing in the field of soil and groundwater remediation,and it should obtain sufficient attention.This research choose the field of soil and groundwater remediation of gas station as research object and investigates soil and groundwater pollution condition of a total of 242 gas stations covering Shaanxi province,Shanxi province,Hebei province,Sichuan province,Jiangsu province and Chongqing city.This report first states the concepts and hazards of gas station pollution and discusses necessity of investigation and remediation of gas station pollution at China integrated with domestic and international research.Then,this report introduces the scope and methods of environmental investigation of gas station,including sampling rationality,sampling methods,analysis parameter and result comparison.This is followed by a summary of investigation data,which includes geographical characteristics,samples characteristics,analysis parameters characteristics,sampling location characteristics,and equipment & material characteristics,meanwhile,the detailed introduction of risk assessment and environmental remediation were providing from the perspective of practice.The results summarized as below:The proportion of domestic gas stations that leaked and has pollution detected is about 48%,and the proportion of domestic gas stations that has no pollution detected is about 52%.The proportion of domestic gas stations with detected pollutants' concentration above referenced standards(called as severely polluted)is about 23%,and the proportion of domestic gas stations with detected pollutants below referenced standards(called as slightly polluted)is about25%.According to previous analysis,gas stations located at areas with relative shallow groundwater surface(Southwestern and Eastern China)have higher proportion to be detected polluted than gas stations located at areas with relative deep groundwater surface(Northwestern China).MTBE can cause odorous even with a very low concentration,which has been listed into potential cancerogenic substance.In terms of MTBE's impact on water quality,America and Australia has started to ban the application of MTBE.It is also suggested that China should reduce or forbidden the use of MTBE.According to the study on Site Concept Model and the summary of ESA on gas stations,construction and operation of gas stations should follow the key points listed below so as to reduce the health risk caused by soil and groundwater pollution:a)Reduce the use of groundwater,especially drinking use.As for gas stations with detected pollutants,it is highly recommended that prevent direct contact with groundwater to block the major exposure pathway of groundwater pollutants;b)Concrete mulch should be well done in gas stations.If any crack or damage happened,repair should be conducted in time and the quality and thickness of concrete should be improved.Ingestion,dermal contact and inhalation of surface soil can be prevented,so do vapor exposure;c)Site selection of gas station should avoid basement or closed/semi-closed space so that in-door accumulation of vapor pollutants can be reduced effectively.The foundation of buildings in gas stations should be strengthened,and the wall should be thickened in order to reduce vapor pollutants entering indoor air.As for remediation of gas stations,engineers should consider the difference between gas stations and other industrial sites,and establish remediation plan in accordance with the real situation.Pollution always happened at safety-sensitive areas,such as tank area and refueling area.Considering the financial lost caused by close down,buildings and facilities in gas stations should be protected during the remediation process.In terms of gas stations where excavation is required,engineers should avoid underground storage tanks and pipeline during excavation to prevent combustion issue.Foundation pit should be treated by ventilation processing to prevent partial accumulation of oil gas.During remediation,engineers should adjust remediation plan in time as remediation processing,adopt multi-plans to conduct remediation,and avoid single remediation plan.Remediation plan should be adjusted in accordance with local hydrogeological conditions.For example,soil vapor extraction(SVE)technology should be priority when it comes to gas stations with sandy soil,but SVE is not suitable when it comes to gas stations with clay soil or relative shallow groundwater surface.