Study On Toxicity Effects Of Light Vehicle Exhaust Particulates On Aquatic Organisms

Automobile exhaust is one of the important sources of atmospheric particulates,in recent years,the number of automobiles in China is increasing,which leads to more and more serious automobile exhaust pollution in China.The particulate matter from automobile exhaust discharged into the atmosphere can enter into soil and surface water through dry or wet deposition,which has a certain influence on soil and water ecosystem.At present,most researches focus on the influence of automobile exhaust on soil environment,while there are few researches on the influence of automobile exhaust on aquatic organisms.In order to control automobile exhaust emissions,China has issued the strictest China VI standards in its history and has been implemented in January 2021.After the issuance of the China VI standards,there was no report on the comprehensive comparison between the China?vehicle and the China VI vehicle,therefore,the main content of this study is as follows:(1)The emission of particulate matter and main 64 kinds of semi-volatile organic compounds from the exhaust of the two types of vehicles were analyzed by selecting the China?standards and the China VI standards as the research objects.The toxic effects of particulate matter from two kinds of automobile exhaust on luminescent bacteria were studied.(2)Different driving cycles(New European Driving Cycle and Worldwide Light-duty Test Cycle),different vehicle types(hybrid and gasoline)and the gasoline particle filter(GPF)and GPF-free in China VI were compared and analyzed for conventional pollutants.In addition,the toxic effects of SUV gasoline,SUV hybrid and sedan gasoline on Danio rerio were also studied.(3)Using D.rerio as a model substitute organism,8 interspecies correlation estimation(ICE)models that meet the standards were constructed and screened to predict the toxic effects of automobile exhaust particles on the other 8 species(Danio rerio,Oncorhynchus mykiss,Oryzias sinensis,Oryzias latipes,Pimephales promelas,Daphnia magna,Chironomus plumosus,Cyprinus carpio and Misgurnus anguillicaudatus).According to the species sensitivity distribution(SSD)method derives the water environment ecological safety thresholds of 3 vehicle types.The main conclusions are as follows:(1)The concentration of particulate matter in exhaust gas of China V,China VIa(without GPF)and China VIb(with GPF)vehicles were 8.81,1.73 and 0.78 mg·km^-1,respectively,and the EC₅₀ for luminescent bacteria were 39.34,34.69 and 49.46mg·L^-1.The results showed that the toxicity of China VIa vehicles per unit mass was slightly higher than that of China V vehicles,but the toxicity of VI vehicles per unit driving distance was significantly lower than that of China V vehicles.By comparison,it was found that PAHs and aromatic compounds in automobile exhaust particulate matter may be the main organic substances that lead to the toxicity of automobile exhaust particulate matter to luminescent bacteria.(2)The emission of pollutants from all types of China VI vehicles conforms to the China VI standard.The EC₅₀ of SUV gasoline,SUV hybrid and sedan gasoline to D.rerio were 3.22,4.46 and 5.62 mg·L^-1,respectively.The content of heavy metals in the exhaust particles of the three types of vehicles also showed the same rule:SUV gasoline>SUV hybrid>sedan gasoline.The results showed that the toxicity of particulate matter from automobile exhaust to zebrafish was obviously related to its heavy metal content.Through comparative analysis,it was found that Cu and Mn may be the main toxic heavy metal substance in automobile exhaust particles.(3)SSD method was used to derived the ecological safety thresholds of SUV gasoline vehicle,SUV hybrid vehicle and sedan gasoline vehicle to aquatic organisms,which were 0.57,0.83 and 1.02 mg·L^-1.The exploratory research in this paper is expected to provide a technical reference for the future revision of automobile exhaust emission standards on water ecological safety assessment.