填埋场不同深度垃圾土压缩性的室内试验研究

阐述了垃圾土的压缩机理,归纳了国内外垃圾土压缩性指标的研究成果。根据某填埋场3个不同深度的垃圾土试样,在改装后的高压固结仪上进行压缩试验,得到垃圾土的压缩系数a、主压缩指数C、修正主压缩指数C'、压缩模量E以及体积压缩系数m,并对试验结果进行分析。试验结果表明,垃圾土的初始孔隙比随填埋深度的增加而减小,垃圾土的压缩指数随其可降解度和有机质含量的减少而降低,垃圾土具有高压缩性,其压缩性指标与垃圾的组成和填埋深度有关。将得到的压缩性指标与国内外的资料进行了比较,可为填埋场的设计及变形计算提供参考。     

城市土地低碳利用模式的变革及路径

随着城市化进程的加快,城市土地开发利用呈现出膨胀式的扩展,特别是在"高消耗、高排放、高污染"的城市发展模式下,不仅造成社会碳排放量快速增长,而且造成城市土地的"碳汇"功能减弱,致使气候变暖、人居环境日益恶化。论文采用文献分析法和综合归纳法,从城市土地的利用结构、空间布局、利用规模与方向等方面,分析城市土地利用模式所存在的问题,结合城市化发展中的土地资源利用、碳排放、生态环境现状,阐述城市土地低碳利用模式构建的必要性,进而探讨构建城市土地低碳利用模式的路径。认为:应从"减排"和"增汇"两方面着手,培育城市土地低碳利用观念,科学规划城市土地的功能分区,构建生态化土地利用模式,形成"政府主导、市场适应、公众参与"的城市土地低碳利用决策机制与模式,从而变革传统的城市土地利用模式,实现城市建设发展的低碳化。     

Quantitative evaluation of environmental risks of flotation tailings from hydrothermal sulfidation–flotation process

Floatation tailings (FT) are the main by-products of the hydrothermal sulfidation–flotation process. FT (FT₁ and FT₂) were obtained by treating two different neutralization sludges (NS) (NS₁ and NS₂). This paper quantitatively evaluated the environmental risks of heavy metals (Zn, Cd, Cu, Pb, and As) in FT versus NS. The total concentration and leaching rates (R ₂) of heavy metals in FT were much lower than those in NS, demonstrating that the hydrothermal sulfidation–flotation process was able to effectively suppress the mobility and leachability of heavy metals. The BCR-three sequence leaching procedure of FT confirmed that all metals were transformed into more stable forms (residue and oxidizable forms) than were found that in NS. The potential ecological risk index indicated that the overall risks caused by heavy metals decreased significantly from 6627.59 and 7229.67 (very serious risk) in NS₁ and NS₂, respectively, to 80.26 and 76.27 (low risk) in FT₁ and FT₂, respectively. According to the risk assessment code, none of the heavy metals in FT posed significant risk to the natural environment except Zn (with low risk). In general, the risk of heavy metals in FT had been well controlled.     

不同流量分配比对多级A/O工艺去除有机物及脱氮的影响

采用三级A/O工艺分段进水工艺处理低碳源生活污水,考察了进水流量分配比对系统去除有机物、硝化反硝化能力以及去除TN的影响。通过对水质指标沿程监测结果表明,不同流量分配比(4∶3∶3,5∶3∶2,6∶3∶1)对系统去除有机物及硝化效率影响不大,出水COD、氨氮分别均在30 mg/L、1 mg/L以下。但反硝化效果受流量分配比的影响较大,在流量比为5∶3∶2时,有效利用原水中碳源进行反硝化,反硝化效果最好。在流量比为5∶3∶2的情况下,TN出水为5.7 mg/L去除率为82.9%,优于流量分配比为6∶3∶1和4∶3∶3时的脱氮效果。总体而言,分段进水工艺在对碳源的有效利用及能耗节省方面优于单点进水。     

Dechlorination of PCBs in the simulative transformer oil by microwave-hydrothermal reaction with zero-valent iron involved

The conventional hydrothermal reaction with iron powder, NaOH and H₂O as reactants was reported to occur at temperature above 423 K, and iron oxides (Fe₃O₄ and NaFeO₂) and hydrogen were produced. In this study, microwave heating was adopted to take the place of conventional heating to induce the hydrothermal reaction. Under microwave irradiation, NaOH and H₂O absorbed microwave energy by space charge polarization and dipolar polarization and instantly converted it into thermal energy, which initiated the hydrothermal reaction that involved with zero-valent iron. X-ray diffraction (XRD) analysis found Fe₃O₄/NaFeO₂ and confirmed the occurrence of microwave-induced hydrothermal reaction. The developed microwave-hydrothermal reaction was employed for the dechlorination of PCBs. Hexadecane containing 100 mg L⁻¹ of Aroclor1254 was used as simulative transformer oil, and the dechlorination of PCBs was evaluated by GC/ECD, GC/MS and ion chromatography. For PCBs in 10 mL simulative transformer oil, almost complete dechlorination was achieved by 750 W microwave irradiation for 10 min, with 0.3 g iron powder, 0.3 g NaOH and 0.6 mL H₂O added. The effects of important factors including microwave power and the amounts of reactants added, on the dechlorination degree were investigated, moreover, the dechlorination mechanism was suggested. Microwave irradiation combined with the common and cheap materials, iron powder, NaOH and H₂O, might provide a fast and cost-effective method for the treatment of PCBs-containing wastes.     

Column study of Cr(VI) removal by cationic hydrogel for in-situ remediation of contaminated groundwater and soil

Column experiments were conducted for examining the effectiveness of the cationic hydrogel on Cr(VI) removal from groundwater and soil. For in-situ groundwater remediation, the effects of background anions, humic acid (HA) and pH were studied. Cr(VI) has a higher preference for being adsorbed onto the cationic hydrogel than sulphate, bicarbonate ions and HA. However, the adsorbed HA reduced the Cr(VI) removal capacity of the cationic hydrogel, especially after regeneration of the adsorbents, probably due to the blockage of adsorption sites. The Cr(VI) removal was slightly influenced by the groundwater pH that could be attributed to Cr(VI) speciation. The 6-cycle regeneration and reusability study shows that the effectiveness of the cationic hydrogel remained almost unchanged. On average, 93% of the adsorbed Cr(VI) was recovered in each cycle and concentrated Cr(VI) solution was obtained after regeneration. For in-situ soil remediation, the flushing water pH had an insignificant effect on the release of Cr(VI) from the soils. Multiple-pulse flushing increased the removal of Cr(VI) from the soils. In contrast, more flushing water and longer operation may be required to achieve the same removal level by continuous flushing.     

PCDDs and PCDFs in sewage sludges from two wastewater treatment plants in Beijing, China

The levels of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) were analyzed by an isotope-dilution high-resolution mass spectrometric in 16 sewage sludges, sampled from 2004 to 2009, from two municipal wastewater treatment plants (WWTPs) in Beijing. Total toxicity equivalent (TEQ) values were evaluated using the toxicity equivalent factors proposed by International for PCDD/Fs. The I-TEQs for these sewage sludges were from 0.97 to 15.0 pg g⁻¹ dry weight (dw) with a mean value 4.43 pg g⁻¹ dw, indicating that all I-TEQs were below Chinese legislation limit value regulated for agricultural use in soils.The results from limited samples (16 samples) showed that the levels of PCDD/Fs might be correlated with the sludge age. Meanwhile, the temporal trends of PCD/Fs suggested that the I-TEQs may correlate with rainfall in the present study.     

Fenton-双泥SBR工艺深度处理难降解反渗透浓缩液

采用Fenton试剂处理反渗透浓缩渗滤液(简称浓缩液),并探讨了双泥SBR工艺对Fenton处理后浓缩液与人工配水混合处理的可行性.结果表明,Fenton氧化对COD、TN和NH3-N的平均去除率分别为43.5%、22.5%和19.5%.对溶解性有机物(DOMs)的去除率为52.5%,其中胡敏酸(HA)、富里酸(FA)...     

焦化行业SO2排放现状及减排潜力分析

随着钢铁工业的高速发展,高温炼焦已成为中国煤炭资源利用的重要途径之一,与此同时焦化行业SO2排放污染问题越来越引起人们的关注.2007年,全国焦炭产量总计335.53 Mt,其中机械化焦炉产量达305.37 Mt,约占全国焦炭产量的91.01%,焦化行业SO2排放量达181.19 kt.在参考国家制定的焦化行业未来产业...     

Analyzing coastal wetland change in the Yancheng National Nature Reserve,China

Coastal zones provide habitat cores and corridors that maintain the diversity of entire landscapes, and they can form the cornerstone elements of regional conservation strategies. Natural environmental driving factors and excessive anthropogenic activities play important roles in coastal wetland change. Many studies have used remote sensing images to map and assess coastal wetland change on local or regional scales. This paper aims to provide insight into coastal wetland change in the Yancheng National Nature Reserve (YNNR) using remote sensing technology and landscape metrics analysis. The results reveal that grass flat and reed areas have significantly decreased, whereas agriculture fields, aquaculture ponds and built-up areas have continuously increased from 1988 to 2006. The spatial pattern of the coastal landscape has become fragmented and heterogeneous under great pressure from rapid economic development and population growth. The wetland changes have important impacts on natural habitat of the red-crowned cranes. The results of this study provide basic information that is required for developing measures toward a sustainable management and conservation of the YNNR.