烟气脱硫液中共存离子对汞稳定化的影响

利用湿法烟气脱硫技术(Wet Flue Gas Desulfurization,WFGD)同步除汞被认为是最经济的燃煤烟气脱汞方式,但进入脱硫液的Hg~(2+)易被还原并再次释放进入大气,造成二次污染.针对这一问题,本研究选择了常用的Na2S、三巯基均三嗪三钠盐(TMT)、二硫代氨基甲酸盐(DTC)等系列重捕剂,考察了投加量对Hg~(2+)去除效果的影响,并筛选出了去除效果较好的3种类型重捕剂,探究了脱硫液中主要的阴阳离子(SO_2-4、NO-3、Ca~(2+)、Mg~(2+))及重金属离子等共存离子对Hg~(2+)去除效果的影响.结果表明:Na2S、TMT类重捕剂TMT-18和DTC类重捕剂DTCR-2的去除效果相对较好;SO_2-4、NO-3会抑制TMT-18和Na2S对Hg~(2+)的去除,对DTCR-2稍有促进作用;Ca~(2+)、Mg~(2+)对TMT-18去除Hg~(2+)有促进作用,而对Na2S有抑制作用;重金属离子会抑制重捕剂对Hg~(2+)的去除效果,Cu~(2+)和Pb~(2+)对Hg~(2+)螯合去除效果的影响较Ni~(2+)和Zn~(2+)要大,随着Cu~(2+)和Pb~(2+)浓度的增加,DTCR-2对Hg~(2+)的去除显著降低,Cu~(2+)浓度的影响尤为显著.本研究可为解决Hg~(2+)在脱硫液中的还原再释放及二次污染问题,同时也为湿法烟气脱硫同时脱汞的工业应用提供理论依据.     

两株降解芘的分枝杆菌的筛选鉴定及降解性能

为获得芘降解细菌,从中国南方地区采集了受PAHs严重污染的土壤与污泥样品.利用平板升华法,分离到2个菌株W52和W74.经形态观察、生理生化试验和16S rDNA的序列分析,2个菌株被鉴定为分枝杆菌属(Mycobacterium sp.).在含芘膜的固体平板上培养,W52和W74在23d中降解芘分别达到13.2Iμg和11.8μg.在含芘50mg·L-1和lOOmg·L-1的无机盐液体中培养,2d时W52的芘降解率达57.8%和20.5%.W74达19.2%和4.O%;随着培养时间的延长,芘降解率不断提高;在第10ci时W52的芘降解率分别达到96.3%和82.3%,W74达83.8%和64·5%.在固体和液体条件下降解芘的结果表明,W52降解芘的能力强于W74.鉴于W52和W74末端双加氧化酶中编码a大亚基的nida基因存在明显差异,推断二者降解芘的能力不同与它们的末端双加氧酶有关.     

Sulfur cycle in the typical meadow Calamagrostis angustifolia wetland ecosystem in the Sanjiang Plain, Northeast China

The sulfur cycle and its compartmental distribution within an atmosphere-plant-soil system was studied using a compartment model in the typical meadow Calamagrostis angustifolia wetland in the Sanjiang Plain Northeast China. The results showed that in the typical meadow C. angustifolia wetland ecosystem, soil was the main storage compartment and current hinge of sulfur in which 98.4% sulfur was accumulated, while only 1.6% sulfur was accumulated in the plant compartment. In the plant subsystem, roots and litters were the main storage compartment of sulfur and they remained 83.5% of the total plant sulfur. The calculations of sulfur turnover through the compartments of the typical meadow C. angustifolia wetland ecosystem demonstrated that the above-ground component took up 0.99 gS/m2 from the root, of which 0.16 gS/m2 was translocated to the roots and 0.83 gS/m2 to the litter. The roots took in 1.05 gS/m2 from the soil, subsequent translocation back to the soil accounted for 1.31 gS/m2, while there was 1.84 gS/m2 in the litter and the net transfer of sulfur to the soil was more than 0.44 gS/(m2·a). The emission of H2S from the typical meadow C. angustifolia wetland ecosystem to the atmosphere was 1.83 mgS/(m2·a), while carbonyl sulfide (COS) was absorbed by the typical meadow C. angustifolia wetland ecosystem from the atmosphere at the rate of 1.76 mgS/(m2·a). The input of sulfur by the rainfall to the ecosystem was 4.85 mgS/m2 during the growing season. The difference between input and output was 4.78 mgS/m2, which indicated that sulfur was accumulated in the ecosystem and may cause wetland acidify in the future.     

Evolution of outer bank cell in open-channel bends

Environmental Fluid Mechanics - Understanding the developing mechanism of an outer bank cell is benefit for making full use of its important function to protect the concave bank from erosion in...