污染物浓度与土壤粒径对热脱附修复DDTs污染土壤的影响

采集2种不同性质的土壤(黑土和棕壤)作为供试土壤,自配不同污染浓度(棕壤)和不同粒径(黑土)的DDT及其同系物(即DDTs,包括p,p’-DDT,o,p’-DDT,p,p’-DDD和p,p’-DDE)污染土壤,采用热脱附方法,分别对300℃,5个停留时间(10,20,30,40和50 min)下的DDTs总去除率及热处理前后各组分的脱附情况进行研究.结果表明,不同污染水平〔w(DDTs)分别为290.17,498.69和718.69 mg/kg〕的污染土壤中,DDTs的总去除率差异不显著.此外,在整个热处理过程中,污染水平对4种DDT及其同系物在土壤中的去除率也没有显著影响.而土壤粒径(0.25～0.85 mm,0.15～<0.25mm,<0.15 mm)对DDTs的去除率影响显著,粒径越大的土壤越有利于DDTs脱附.单因素方差结果显示,粒径对土壤中p,p’-DDT和p,p’-DDE的脱附和转化有显著影响.

Effects of Different Pollutant Concentrations and Soil Particle Size on Thermal Desorption Efficiency of DDT-Contaminated Soil

Two different soils,black earth and brown earth,were chosen as test samples to prepare soils contaminated with DDT and its homologues(including p,p′-DDT,o,p′-DDT,p,p′-DDD and p,p′-DDE) at different concentration levels(using the brown earth samples) and different particle sizes(using the black earth samples).Thermal desorption technology was used to study the total removal rates of DDTs and removal rates of DDT and its homologues in the contaminated soils at 300 ℃ and five levels of residue time(10,20,30,40 and 50 min).The results showed that there were no significant differences between the removal rates of DDTs in soils with different pollution levels;the w(DDTs) were 290.17,498.69 and 718.69 mgkg.Also,the pollution level had little influence on the removal rates of the four DDTs and their homologues.However,the results suggested that particle size(three levels:0.25-<0.85 mm,0.15-<0.25 mm,<0.15 mm) had considerable impact on the DDT removal rates.The larger the soil particle sizes were,the more DDTs were desorbed.The results of one-way ANOVA testing further indicated that desorption and transformation efficiency of p,p′-DDT and p,p′-DDE largely hinged on soil particle size.