| As a class of emerging contaminations?ECs?,dimethylsiloxanes has gained increasing attention because of their persistence,long-range transmission,estrogenic effects and biomanification.Due to their unique properties and broad usage in urban life,dimethylsiloxanes can be slowly released into urban environment during production and application.As a result,dimethylsiloxanes were expected to accumulate in urban dust.The occurrence,and spatial distribution of dimethylsiloxanes in urban dust is still in need of further research.With these questions,sampling urban dust associated dimethylsiloxanes in national scale were conducted.The components of PDMS 200?were identified and their percentages were quantified based on a new established method.In addition,the analytical method were developed to measure dimethylsiloxanes in urban dust.The primary results were listed in the following:?1?GC-MS was used to identify the components of PDMS 200?,combined with Kovac index.14 linear dimethylsiloxanes?L5-L18?and 1 cyclic dimethylsiloxane?D7?were identified in PDMS200?.The“effective carbon number?ECN?concept”was applicable for responses of dimethylsiloxanes in FID.Based on GC-FID,a new quantification method for compounds in PDMS 200 fluid was established used to calculate the content of individual dimethylsiloxane in PDMS 200 fluid.Compared with the results from external standard method,internal standard method and normalization method,the new quantification method was more accurate and stable.?2?The analysis method of dimethylsiloxanes in urban street dust using GC-MS was developed.The instrument detection limits for cyclic dimethylsiloxanes?D3-D8?and linear dimethylsiloxane?L3-L16?were 2.02-2.4 ng mL-1 and 0.68-1.67 ng mL-1,respectively.The instrument quantification limits of cyclic dimethylsiloxane?D3-D8?were 3.05-3.36 ng mL-1 and those of linear dimethylsiloxanes?L3-L16?were1.02-2.28 ng mL-1.The linear ranges of D3-D8 and L3-L5 were 2.5-500 ug L-1;linear ranges of L6-L16were of 100-10000 g L-1 expressed by PDMS200?.The recoveries of D3-D8 and L3-L16 were57.7±0.6-96±6.86%and 78.1±5.7-95.1±8.8%,respectively.?3?The detection rates of cyclic dimethylsiloxane and linear dimethylsiloxane were48.6%-92.6%and 23.6%-100%,respectively.The detection rates of dimethylsiloxane with low molecular weight and high molecular weight was low,while those of dimethylsiloxane with medium molecular weight was high.The average content of total dimethylsiloxane in urban street dusts ranged from11.28 to 2907.61 ng g-1 dw;the average content of cyclic dimethylsiloxane ranged from ND to 1156.95 ng g-1 dw;and the average content of linear dimethylsiloxane ranges from 11.28 to 2907.61 ng g-1 dw.The"agglomeration"of dimethylsiloxanes in three altitudes?0-500 m,750-1250 m and 1700-2500 m?was observed.In addition,the distribution of total dimethylsiloxane content?median?is different in different climatic types.?4?The average contents of 20 target pollutants in urban road dusts on national scale were L16(324.48 ng g-1 dw),D7(159.73 ng g-1 dw),L15(7.20 ng g-1 dw),L10(61.55 ng g-1 dw),L12(46.32 ng g-1dw),D8(42.69 ng g-1 dw),D6(37.97 ng g-1 dw),D5(34.16 ng g-1 dw),L13(27.77 ng g-1 dw),L11(25.94ng g-1 dw),L9(23.69 ng g-1 dw),L14(22.84 ng g-1 dw),L8(17.78 ng g-1 dw),D4(15.19 ng g-1 dw),D3(15.15 ng g-1 dw),L5(7.20 ng g-1 dw),L7(6.53 ng g-1 dw),L6(2.58 ng g-1 dw),L3(<1.03 ng g-1 dw)and L4(0.74 ng g-1 dw).D7 was the most aboundant specie in cyclic dimethylsiloxanes,while L15 and L16showed high percentages in linear dimethylsiloxanes.In addition,the concentration of target pollutants in this study was independent of size and TOC of urban dust. |
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