Influence Of Physical-Chemical Properties And Temperature On Soil/Air Partition Coefficient Of Selected Compounds

The old industrial base in Northeast China is a major heavy industry and commodity grain base.Both manufacturing and agricultural enhanced the possibility of introducing contaminants into soil.Meanwhile,as the three terrestrial oil fields were in this region,the soils near the oil field were badly polluted during the processes of exploitation and transportation of oils.The old industrial base located in the northeastern China,has a long cold winter usually from November to February with the extremely temperature lower than -35℃.The present study was focused on the soil/air partitioning behavior of selected volatile organic compounds(VOCs) and semivolatile organic compounds(SOCs) under a frozen circumstance or in oil-complex contaminated soils.The study comprises of several parts as follows:(1) The soil/air partition coefficient K_SA for TCE was determined in batches in three soils, black soil,paddy field soil,yellow soil,with different organic carbon contents.The results showed that K_SA for TCE increased with organic carbon contents.For the strong temperature-dependence of K_SA,even for a volatile compound,TCE,could be tend to partition into the soil at lower temperature(-14℃,K_SA = 10³).(2) K_SA-values for 66 PCBs congeners(including 27 co-eluting congeners) in Aroclor 1242 were measured by fugacity meter method over -30～30℃.About 600 data were obtained,which ranged 10^4.4～10¹¹.Of all the PCBs tested,plots of log K_SA vs.T¹ exhibited two separate regression lines below and above 0℃,with the slope over 3.82～5.61 and 5.58～6.88 below and above 0℃,respectively.The larger slope below 0℃indicating the greater enhancement of K_SA with a decline of temperatures below 0℃,might caused by the decrease of soil relative humidity(RH) under a frozen circumstance.The slopes of linear regression between log K_SA and log K_OA were close to 1 implying that K_OA was a suitable surrogate for the partitioning properties of present soil.Furthermore two modified Karickhoff-type equations were introduced to fit values of K_SA for PCBs above and below 0℃,respectively.(3) To extend the database for K_SA at sub-zero temperatures,K_SA-values for phenanthrene(Phe),fluoranthene(Flu),α-hexachlorocyclohexane(α-HCH),γ-hexachlorocyclohexane(γ-HCH),trans-chlordane(TC),o,p'-DDE,cis-chlordane(CC) and trans-nonachlor(TN) were also determined by the same method as PCBs over -30～30℃.As observed by PCBs,for these compounds plots of log K_SA vs.T¹ also exhibited two separate regression lines below and above 0℃,with the slope from 4.11 to 4.84 for the PAHs and from 4.75 to 5.65 for the OCs above 0℃.And K_SA became more sensitive to the temperature below 0℃,with the slope from 5.51 to 6.10 for the PAHs and from 6.23 to 9.68 for the OCs. The average slope of linear regression between log K_SA and log K_OA at different temperatures was 0.6 for OCs and K_OA-based Karickhoff equation could be used to roughly estimate the K_SA for OCs.(4) Considering that oil contamination is one of the most important environmental problems in the northeastem China,K_SA for hexachlorobenzene(HCB) was determined in an artificially HCB-oil complex contaminated soil at different oil contents and temperatures.The results showed that the critical separate phase concentration(CSPC) for a crude oil from Liao River oil field in the soil with 1%organic carbon content was about 1000 mg kg^-1.As compared to the natural organic carbon,oil is a supersorbent for HCB,with the ratio of (oil/air partition coefficient)/(organic carbon/air partition coefficient) from 5 to 1 when temperature decreased from 30 to 5℃In conclusion,measurements of K_SA for selected VOCs and SOCs were carried out over a wide relevant temperature range.With the experimental data below 0℃,the partitioning behavior of the selected SOCs was discussed.Meanwhile,the partitioning behavior of SOCs in oil-contaminated soils was also investigated.This work attempts to close the gap of partitioning data at subzero temperatures and thereby expands our understanding of the environmental behavior and fate of organic chemicals in a low-temperature environment.