The Identification And Distribution Study Of Significant Groundwater Volatile Organic Compounds From Typical Contamination Sources In China

As a very important drinking-water source,groundwater is continually under threat from hunman activities.Some volatile organic compounds(VOCs),which are carcinogenic,teratogenic and mutagenic,have been detected frequently from groundwater in China in recent years.It is necessary for us to pay attention to VOCs in groundwater.This study focused on two types of organic contaminant sources,the characteristics of the polluted groundwater around the two sources and the relationship between the two sources.The objectives of this study are to further understand current situation of groundwater organic contamination and provide a theoretical basis for groundwater protection.In this study,two typical groundwater contamination sources(decentralized factory source(DFS)and wastewater-receiving river source(WRRS))were selected,148 groundwater samples were collected from 7 provinces in China,and 56 VOCs were tested in the laboratory.In order to explore the relationship between these two contamination sources and identify the factors that influence VOCs occurrence,some statistics methods were used,such as multinomial logistic regression and Q-Q plot.Main findings are as follows:In 148 groundwater samples,chlorohydrocarbon and BTEX(benzene,toluene,ethylbenzene and xylene)are the most common VOCs,but methyl tert-butyl ether(MTBE)and naphthalene have the highest detection frequencies,which are 62.16% and 50.68%,respectively.Six VOCs exceed their limitation values of standard for groundwater quality of China(Class ?)(DZ/T 0290-2015),the exceeding multiples are from 2.04 to 39.5 and the over-limit ratios are between 1.35% and 10.14%.Samples exceeding the standard are totally from the decentralized factory source.45 VOCs are found in 79 DFS samples and 31 VOCs are found in 69 WRRS samples.Among the detected VOCs,16 VOCs are from the DFS individually and only 2 from the WRRS.The detected VOCs type,concentration and detection frequency of DFS samples are all greater than WRRS samples.WRRS as a secondary contamination source potentially pollutes groundwater after receiving waste water from DFS.29 VOCs are found in both DFS and WRRS samples,12 of them having a detection frequency of >10%.For 10 of the 11 VOCs except for dichloromethane,their concentrations in DFS samples are higher than those in WRRS.9 of the 12 VOCs from two contamination sources show different linear relationships.Each slope k of the linear relationship represent VOC attenuation from DFS to WRRS.The k is closely related to VOC properties and VOC categories.Multinomial logistic regression results indicate that logKow is one of the key influencing factors on VOC detection frequency for DFS,whereas the influencing factors are complex for WRRS.