Sources, Accumulation and Distribution of Dioxin-like PCBs in the Typical Plants from Yellow River Delta
|Keywords||Plant Dioxin-like PCBs Source Accumulation Distribution law Yellow River Delta|
Polychlorinated biphenyls (PCBs) are a class of persistent organic pollutants (POPs), with persistence, semi-volatile, bioaccumulative, high toxicity characteristics of the Stockholm Convention on Persistent Organic Pollutants (POPs) The provisions of the first control to eliminate one of the 12 categories of pollutants. Dioxin-like polychlorinated biphenyls (DL-PCBs) is the ortho or only one chlorine atom-substituted PCBs, with 12 homologues, is the most toxic PCBs. Although the content of the DL-PCBs in the environment and in biological samples is low, but the toxicity contribution value is greater, in the study of organisms in PCBs, DL-PCBs is more important, is currently a hot area of ??research at home and abroad. This study on the basis of a detailed inspection and systems analysis research at home and abroad to establish plants DL-PCBs analysis method, and further analysis of the content of DL-PCBs and pollution in the Yellow River Delta plant pollutant sources identify, investigate, DL-PCBs accumulated in different plant characteristics and differences, and come to the distribution pattern of the DL-PCBs in the different parts of the plant. (1) Trace DL-PCBs in plant research and analysis methods to establish PCBs analysis of existing plants more interference of impurities target low levels of pollutants present in trace amounts for plant samples DL-PCBs little research, there is an urgent need Create a simple, rapid and specific analytical methods. Therefore, this study from the sample pre-treatment technology optimization to improve the experimental conditions and parameters, the establishment of a simple, rapid plant DL-PCBs analysis methods, can be achieved Qualitative and quantitative analysis of trace DL-PCBs in plant samples. Specific conditions and the results are as follows: pre-treatment of the sample. Soxhlet extraction condition parameters optimization study, the optimal conditions: using of 200mL hexane / acetone (1:1 V / V) mixed solvent, the reflux rate of 4 times / h Soxhlet extraction 20-30g (dry weight) plant. Sample 24h. After extraction the extract was washed with concentrated sulfuric acid / potassium permanganate treatment, and then purified by Florisil column. DL-PCBs in the sample analysis. Weakly polar and the polar dual capillary column chromatography complementary separation techniques combined with DL-PCBs in the GC / MS analysis of samples, the method can be good DL-PCBs and other PCBs isomers and organochlorine pesticide residues interference components separated from each other can be effective analysis of plant samples DL-PCBs. The results showed that 12 kinds of DL-PCBs spiked recoveries between 75.56% -87.42%, the the plant samples parallel measurements of relative standard deviation 3.60% -14.53%, in line with the U.S. EPA standard recovery (70% -140 %) and environmental samples precision relative standard deviation (<20%) requirements. (2) the content of typical plants of the Yellow River Delta in DL-PCBs and sources in order to study the content and source of the DL-PCBs in the Yellow River Delta plant, in October 2006, the Yellow River Delta Imperata (Imperata cylindrical var.major), Reed (of five typical plant Phragmitesaustralis (Cav.) Trin.ex Steud) Suaeda (Suaeda Heteroptera), Tamarix (Tamarixchinensis Lout), willow (Salix matsudanaseedlings Koidz.) and the corresponding DL-PCBs in the soil content were determined. Among them, the range for the content of plants in the total amount of DL-PCBs 575.48-819.23ng/kg, the content ranges of the DL-PCBs homologues 2.32-237.36ng/kg; corresponding plant soil content range of the total amount of DL-PCBs DL-PCBs homologues content range for 147.75-505.58ng/kg 2.48-403.58ng/kg. DL-PCBs content in plants and soils in the Yellow River Delta, whether from the total or with homologues level than reported in the literature in other regions. Through the soil and plants DL-PCBs each with the Department of matter concentration correlation analysis derived plants DL-of PCBs in the concentration and the soil is not significant with related this description in the Yellow River Delta plants DL-of PCBs in the main source is not soil, according to DL- PCBs octanol - air partition coefficient (k oa ) and octanol - water partition coefficient (K ow ) of the range of values, combined with the results of other similar studies, can be judged The atmosphere is the main source. (3) the typical plants of the Yellow River Delta by DL-PCBs accumulation characteristics of three annuals (Imperata, reed, Suaeda) DL-PCBs in the Yellow River Delta and two perennials (Tamarix, willow) body, and the corresponding soil concentration in the analysis and comparison study DL-PCBs in different species of plants in the amount and composition differences illustrate from octanol - air partition coefficient DL-PCBs, homologues type, the classification of plants and growth time The reason for this difference. The main findings are as follows: DL-PCBs accumulated ① different types of plants, the total amount and composition differences Imperata in DL-PCBs total amount (575.48ng/kg) of the lowest in five plant species were no significant differences between the other four plants ; 12 DL-PCBs were detected in all plant sample, wherein only PCB126 accumulation levels between the various plant addition, PCB77, PCB81, PCB114, PCB123 and PCB156 in more than three plants were significantly different, the difference largest PCB81 Tamarix content is the Imperata content 72 times. ② plants DL-PCBs accumulated factors DL-PCBs the K oa accumulation in plants. Through the relationship between log K oa and C plants / C Imperata (four plant reeds, salsa, tamarisk, willow DL-PCBs content Imperata in DL-PCBs content ratio) analysis when logK oa was 8.46 hours, plant C / C Imperata values ??of 2.0-72.3 when logK oa 11.25 the C plants / C Imperata 0.7-1.5. Thus, plants with the octanol - air partition coefficient increases and reduce the accumulation of DL-PCBs interspecies differences in the degree, K oa DL-PCBs accumulation in different plants difference of important factors. Plant type plants accumulated amount of DL-PCBs. By clustering analysis of the 12 DL-PCBs in concentrations of five plant know, five plant, Imperata and the reed accumulation is most similar, because they belong to the same families - Poaceae, so relative to other plants, Imperata and Reed DL-PCBs accumulated the most similar. Of plant tissue different growth time on the accumulation of DL-PCBs characteristics. By plants of DL-PCBs concentration log K oa analysis found, salsa, reed related (p <0.05) in the two, Imperata three kinds of annuals, correlation coefficients were 0.354 0.464,0.390, and perennials in both correlation does not significantly. Thus perennials and annuals can be seen, this is due to the differences perennials in the organization of the different growth time of accumulation of the DL-PCBs accumulation characteristics of the DL-PCBs, the year Health Organization biomass in the whole plant in occupied small proportion of perennials in the concentration of DL-PCBs with log K oa does not reflect the significant correlation. (4) distribution of DL-PCBs in the different tissues of the Yellow River Delta typical plant select annuals Suaeda both perennials willow plant in November 2007 to study pair the Suaeda of ground, underground part and willow leaves Determination of the concentration of DL-PCBs, roots and branches of different growth time to investigate the distribution of different plant tissues DL-PCBs. The ① Suaeda different portion DL-PCBs in the distribution of the experimental results showed that, the The Suaeda aerial parts of the DL-PCBs content was significantly higher than that of the underground part, the total concentration, respectively 1263.33ng/kg and 889.47ng/kg. See in Suaeda different parts of the analysis results from the component of the DL-PCBs homologues, PCB81, 77,123,118,114 in Suaeda ground portion accumulation concentration significantly higher than in the underground portion of the accumulated concentration, while the other 7 no significant difference between the kinds of DL-PCBs homologues, lower chlorinated DL-PCBs easier accumulated in the ground part of the Suaeda. ② the willows different organizations DL-PCBs accumulation distribution law by the determination of the content of DL-PCBs in various organizations in the willow, come to the total content of leaves 3054.64ng/kg a total content 704.28ng/kg, and one hundred twenty-three roots the total content of the four branches were 538.58,770.75,714.65,552.59 ng / kg. The above results can be seen, willow six organizations, DL-PCBs highest total content of leaves; branches in DL-PCBs content order: two branches> three branches> four branches> a twig ; similar to the DL-PCBs content in the root and the three branches significant differences with other organizations. Know that according to the results of each part in the willow DL-PCBs homologues Determination leaves 12 DL-PCBs homologue concentrations were higher than in other parts, branches and roots at all levels in each DL-PCBs homologues did not show significant differences. Factors Affecting ③ DL-PCBs in the distribution pattern of two different plant tissues by DL-PCBs content and plant Suaeda and willows in crude fat content analysis to know, they are not significantly related. DL-PCBs in various parts of Suaeda and willow total content of the plants, the total organic carbon content analysis findings, DL-PCBs and total organic carbon content in the various parts of Suaeda and willow were tested a significant negative correlation, the correlation coefficient -0.661, -0.854 (p <0.05). This is because the DL-PCBs accumulated no the TOC accumulation of fast growth diluted caused TOC portion of high content of DL-PCBs but less trend.