Study On The Analytical Method, Source Apportion Ment And Distribution Trends Of Dioxin-like And Atropisomeric Polychlorinated Biphenyls(PCBs) In Soils

In this study, on the basis of the review of former researches about the analysis methods, source apportionment approaches and distribution trends in soils, the pretreated method, separation instrument method were studied systematically; The rapid and accurate analysis methods for trace dioxin-like and atropisomeric PCBs in soil samples were set up; The PCBs sampling scheme of soil in the Yellow river delta was worked out and the current status and pollutant characteristic of 12 dioxin-like and 19 atropisomeric PCBs congeners in the soil of modern the Yellow River delta (China) are investigated using the established analysis method; Then the source apportionment of PCBs in soil for the Yellow River delta was carried out by PCA (principal component analysis) model, the types of pollution sources and their contribution percentage were calculated; With the integration of PCBs toxicity, persistence and bio-accumulation, the PCBs pollution was defined as toxicity, persistence and bio-accumulation sub-pollution indexes and total pollution index (PI), the calculation equations were expressed and the evaluation method was built, the evaluation of the PCBs pollution in the modern Yellow River delta was accomplished successfully; The spatial distribution rules of PCBs were determined and the influences of the soil characteristics to the PCBs distribution were studied and the main influencing factors of soil characteristic parameters on PCBs distribution were determined by correction analysis. This study provided a theory basis for the researching of forming transportation, transformation and fating of organic pollution in soil. This dissertation included the following contents and conclusions:①Pretreated technique studies for the extraction of organic pollutants in soil samplesSolhex extraction conditions were optimized in order to achieve effective extraction of organic pollutants. The optimized soxhlex extraction conditions were listed as followed: extraction time was 24h. recycle rate was 3～4 times per hour and the amount of mixture solvent (n-hexane/acetone 1:1V/V) was 200mL/50kg. The extraction effective was determined by 12 dioxin-like PCBs. The average recovery rates of 12 dioxin-like PCBs were in range of 82.6%～109.8%. and the recovery rates RSD of 12 dioxin-like PCBs were in range of 1.1-6.3%. Compared to the supercritical fluid extraction (SFE) studied in our lab which the recoveries of 12 dioxin-like PCBs ranged from 73.0%～129.0% and the method precision is in the rang of 1.0%～10.5%. The conclusion that the Solhex extraction method has obvious advantages on better extraction efficiency, more sample treatment amount and lower pretreated payment were reached.The purification methods employed by US.EPA Method 3665 were studied and the operation conditions were determined. The optimized amount was 20mL for a Florisil column filled with 1000mg,6mL Florisil. In the meantime the recoveries of 12 dioxin-like PCBs of 98% sulfuric acid/potassium permanganate and Florisil column purification methods were in range of 88.0%～112.8% and 94.8%～106.6% individually. These experiments testified that the 98% sulfuric acid/potassium permanganate and Florisil column purification methods are effective and lower lose of target PCBs.②Dual high resolution capillary column HRGC/ECD method for the determination of dioxin-like PCBs in soilA rapid and accurate method has been developed for determination of 12 dioxin-like polychlorinated biphenyls (dl-PCBs) in samples using complementary separation on dual columns system with low and intermediate polarities. Qualitative and quantitative analysis of dl-PCBs were performed by the two retention data on dual capillary gas chromatography with a 63Ni electron capture detection (GC/ECD), the co-elution between 12 dl-PCBs and the bulk PCBs and pesticides was solved. The accuracy of qualitative analysis was confirmed by the gas chromatography mass Spectrometry (GC/MS) using selective ion mode (SIM) technique. The method has been validated: precision was estimated from the relative standard deviation (RSD) of the six duplicate analyses of a soil sample, and the RSDs of 12 dioxin-like PCBs was in ranged of 1.6-14.9%; accuracy was estimated from the recovery of spiked analyses from the soil matrix; The recoveries of target analysts were found to be in the range of 82.0-112.0%; The method detection limits (MDLs) of 12 dioxin-like PCBs were in range of 1.5-3.9ng·kg^-1 . The applications of this analysis method to the determination of dioxin-like and atropisomeric PCBs in dust-deposition, sediment and soil samples from the Yellow River delta has been carried out successfully. The conclusion that this analysis method has higher precision, accuracy and lower MDLs can be reached. This method can be used widely in environmental monitoring and research.③Retention index analysis method studies for the determination of atropisomeric PCBsA new method that determinate the qualification and quantification parameters of 19 PCBs by using PCBs retention indices (RIs) and relative response factors (RFs) databases in literature, a PCBs standard reference (12-dioxin-like PCBs) and 5 of 19 target PCBs congeners with different numbers of chlorine atoms rather than target PCBs standards was proposed. The applicability evaluation and revision method of the PCBs databases were set up; and the database whose RIs or RFs exhibit the best linear relationships with the experimental Rts and RFs of 12 dioxin-like PCBs reference series on temperature programmed capillary columns Rtx-5 column were employed to calculate the Rts and RFs of 19 atropisomeric PCBs congeners under the same analysis condition. 5 of 19 target PCBs congeners with different numbers of chlorine atoms were selected to confirm the quality of the calculated values. The calculated qualification-Rts and quantification-RFs results showed good agreement with the experimental values. The devise equation can decrease the system deviation between analysis system used in literature and in our lab. The proposed method can revise the database in literature increase their application range. The applications of this method to the determination of dioxin-like and atropisomeric PCBs in dust-deposition, sediment and soil samples from the Yellow River delta has been carried out successfully.④Current status and pollution characteristic of 12 dioxin-like and 19 atropisomeric PCBs in the soil of the Yellow River delta (China) are investigated in this paper. The concentrations of the dioxin-like PCBs are found in the range of 108.7 to 2153 ng·kg^-1 dry weigh with an average of 800.5 ng·kg^-1 dry weigh. Thetoxic equivalency (TEQ) in this area varies from 2.3×10^-5 to 9.5×10^-3 ng-TEQ kg^-1 dry weight. While the concentrations of the atropisomeric PCBs are found in the range of 46.8 to 619.3ng·kg^-1 dry weigh. PCB118, the main congener, accounts for 46.7% of the 12 dioxin-like PCBs in the soil samples. More than 60% polychlorinated biphenyls are contributed by Penta-PCBs. According to the TEQ and PCBs standard in soils, combined the total PCBs value calculated by the percentages of the 12 dioxin-like and 19 atropisomeric PCBs in commercial PCBs. the pollution status and toxic contribution of PCBs in the modern Yellow River delta were insignificant. ⑤Source apportionment for PCBs in soils.The environmental statistic analysis method-Principle component analysis (PCA) was employed to achieve source apportionment for PCBs in soil from the Yellow River delta. The result indicated that that there were four types to the contaminate sources affecting the PCBs distribution pattern. The first kind of sources was the most significant and largest influence range. The first type PCBs source was from the sand and mud associated with pollutants which was discharged to the Yellow river by the enterprises along the river, and this water runoff contributes 49.6% of the total contaminant burden in the Delta; The second and third types of PCBs source were just belong to the I and 5 sample sites individually, and we can determined that the sources were point sources which may be from the leakage of capacitors during the oil exploitation, the point sources contribute 15.0% and 10.1% of the total contaminant burden in the Delta individually; The fourth kind of source has widely but less influences is believed to be from the atmospheric dry and wet precipitation, it contributes 8.4% of the total contaminant burden in the Delta. The composition of the principle components were discussed too. The results showed that the composition of the first source was native commercial PCBs application, its composition was correspondence with Arclor 1242; the second composition was similar to Arclor 1221 and Arclor 1242, and the third composition was similar to Arclor 1260. the forth composition was very complicated and it consists of Aroclor1242,1248 and 1260. The results will support the controlling and management of the PCBs pollution.⑥Study of the evaluation method of PCBs pollution in soilAn evaluation method for PCBs pollution in soil was set up for the first time by referring to the conception of pollutant index. The standard value series of total PCBs employed by National guideline and standards office, Canada and the toxicity, persistence, and bio-accumulation transformation indexes were introduced into the evaluation model. With the integration of PCBs toxicity, persistence, and bio-accumulation, three sub-pollution Indexes for PCBs toxicity, persistence, and bio-accumulation and pollution index were defined and the relevant expressions were set up too. Then by the application of the evaluation method the PCBs Pollution Index in the Yellow River delta soil were calculated and the PCBs evaluations in 22 soil sample stations were accomplished successfully, and the quantification results were fit for the qualification method. The result obtained from this method makes people understand the PCBs pollution current status easily, clearly and completely. This evaluation model considered the characteristic differences between congeners scientifically and comprehensively, and should be employed in evaluations of persistent organic pollutants (POPs).⑦The spatial distribution trends of PCBs pollution:The distribution trends of dioxin-like PCBs in soil from modern Yellow River delta were summarized as followed: PCBs trend in the direction of water flow are strongly depends on the sample locations where the sediment characteristics were affected by the time the soil was formed, the locations in upstream of the Delta were slightly polluted, while the highest PCBs concentrations located in the middle part of the Delta, and the higher concentrations of PCBs were at the downstream Delta; in the direction across the river, the closer are the sample stations to the river bed, the higher levels of the dioxin-like PCBs are detected; with the increase of soil depth, the concentrations of the contaminants decreased gradually. The distribution rules of dioxin-like PCBs suggested that the water runoff is the main source of the total contaminant burden in the Delta, and atmospheric precipitation plays an important role.⑧The influence factors of the physic-chemical parameters on the PCBs distribution were determined by correction statistic analysis method: The relationship between the total PCBs concentrations in 22 samples and the composition of soil particles were that the total PCBs concentrations had a greatly significant positive correlation with clay content, while they had a significant negative correlation with sand content and had no correlation with silt content. The relationship between the total PCBs concentrations in 22 samples and the TOC content using similar methods was that the total PCBs concentrations had a significant positive correlation with the TOC content. However the total PCBs concentrations had no correlation relation with dissolved salt content. This result indicated the clay and sand contents of soil practical composition, the TOC content were the main influencing factors on the PCBs distribution.