Method Optimization On Pretreatment Of Soil Sample For The UMU Test And Risk Assessment

Umu test, which also called SOS/Umu test, has many advantages such as simpleness, celerity, sensitivity, cheapness and so on, it has been applied widely to genotoxicity detecting of chemical materials and environmental samples. At present, umu test has been more applied to the genotoxicity detecting of water samples in domestic and overseas, which pretreatment methods are mature and toxicity assessment system also perfect. Whenas the genotoxicity detecting of soil samples is less, corresponding the quick and efficient pretreatment methods of soil samples has many problems. In this paper, we optimized the pretreatment methods of soil samples for the umu test, evaluated the ecological risk and cancered risk of petroleum contaminated soil.(1) Optimization on the pretreatment methods of soil samples for the umu test.Fistly, we researched on the extractive effects of 16 kinds polycyclic aromatic hydrocarbons (PAHs) in petroleum contaminated soils with different extractive methods. We mainly adopted ultrasonic extraction, microwave and surge assisted ultrasonic extraction, soxhlet extraction and so on. Research on ultrasonic method, come out the optimal extraction parameters. It has analysed the extractive effect of direct ultrasonic extraction, microwave assisted ultrasonic extraction and microwave and surge assisted ultrasonic extraction under optimal ultrasonic extraction parameters, and comparing with 72h soxhlet extraction. The results showed that direct ultrasonic extraction has the best extractive effect, which get the most amounts ofΣPAHs and macromolecular PAHs.Secondly, we researched on the extractive effects of PAHs in soil with different solvents, mainly studied five kinds of solvent system, these are hexane, methylene chloride, acetone, hexane mixed with methylene chloride which their volume ratio is 1:1 and acetone mixed with hexane which their volume ratio is 1:1, we researched the extraction of PAHs with the best extraction method that we had got. The results showed that we use methylene chloride as extraction solvent has best extraction effect.Researched on the pretreatment methods of soil samples which applicable to the umu test, we mainly studied three extraction methods: the direct ultrasonic extraction, the optimal combination of microwave and surge assisted ultrasonic extraction and 72h soxhlet extraction. We did umu test with PAHs which extracted and compared their genotoxicity, we obtained that the direct ultrasonic extraction had the most genotoxicity, it can replace 72h soxhlet extraction as the pretreatment method of soil samples for the umu test.(2) Risk assessment on petroleum contaminated soil.We used the best pretreatment method of soil samples for the umu test as the extraction method of PAHs from petroleum contaminated soils of different wells.Fistly, we evaluated the ecological risk of petroleum contaminated soils through studied PAHs in 10 sampling sites of different wells. We investigated the PAHs residues, the results showed that PAHs residues in this aera ranged between 70.8 and 5013.2μg/Kg, the PAHs with more than three rings were the main pollutants, and the detection rate of BAP is 100%. Evaluation with the N. L. Nemerow composite index and the standard for PAHs management of agriculturals soils in Canada showed the ecological risk of soils around working well and the well which stop production shorter time are higher. Many factors have effects on the ecological risk of surface contaminated soils in oilfield, such as the running state, oil well production time and the distance with the pollution.Secondly, we evaluated the cancered risk of petroleum contaminated soils with umu test through analysed the genotoxicity of the PAHs from petroleum contaminated soils of different wells in oilfield, come out the genotoxicity related with the running state and the distance with the pollution. The well abandoned longer time or distanced the pollution farther, the genotoxicity of soils is lower and the cancered risk of area is relative lower.Best ultrasonic extraction compared with traditional soxhlet extraction, it can extrate the objects from soil quickly and efficiently and its'umu test results can reflect the genotoxicity of soil comprehensively, so this method can be used as the new soil sample pretrement method for umu test.