Identifying the factors that influence the heavy metal contents of soil could reveal the sources of soil heavy metal pollution.In this study,a categorical regression was used to identify the factors that influence soil heavy metals.First,environmental factors were associated with soil heavy metal data,and then,the degree of influence of different factors on the soil heavy metal contents in Beijing was analyzed using a categorical regression.The results showed that the soil parent material,soil type,land use type,and industrial activity were the main influencing factors,which suggested that these four factors were important sources of soil heavy metals in Beijing.In addition,population density had a certain influence on the soil Pb and Zn contents.The distribution of soil As,Cd,Pb,and Zn was markedly influenced by interactions,such as traffic activity and land use type,industrial activity and population density.The spatial distribution of soil heavy metal hotspots corresponded well with the influencing factors,such as industrial activity,population density,and soil parent material.In this study,the main factors affecting soil heavy metals were identified,and the degree of their influence was ranked.A categorical regression represents a suitable method for identifying the factors that influence soil heavy metal contents and could be used to study the genetic process of regional soil heavy metal pollution.
Jun YangJingyun WangPengwei QiaoYuanming ZhengJunxing YangTongbin ChenMei LeiXiaoming WanXiaoyong Zhou
Adding organic amendments to stimulate the biodegradation of pesticides is a subject of ongoing interest. The effect of sewage sludge on the bioremediation of dichlorodiphenyltrichloroethane（DDT） and hexachlorocyclohexane（HCH） contaminated soil was investigated in bench scale experiments,and intermittent aeration strategy was also used in this study to form an anaerobic–aerobic cycle. Bioremediation of DDT and HCH was enhanced with the addition of sewage sludge and the intermittent aeration. The removal rates of HCH and DDT were raised by 16.8%–80.8% in 10 days. Sewage sludge increased the organic carbon content from 6.2 to218 g/kg,and it could also introduce efficient degradation microbes to soil,including Pseudomonas sp.,Bacillus sp. and Sphingomonas sp. The unaerated phase enhanced the anaerobic dechlorination of DDT and HCH,and anaerobic removal rates of β-HCH,o,p′-DDT and p,p′-DDT accounted for more than 50% of the total removal rates,but the content of α-HCH declined more in the aerobic phase.
Qi LiangMei LeiTongbin ChenJun YangXiaoming WanSucai Yang
