Sewage sludge ditch for recovering heavy metals can improve crop yield and soil environmental quality

• Indirect use of sludge in ditches alongside plants was tested in field experiments. • The dried and stabilized sludge in ditches was recovered with heavy metals. • Cd, Pb, Cu and Zn in the planted soil were all in a safe range. • The indirect use of sludge increased plant yield, soil N content and C storage. The treatment and disposal of municipal sewage sludge (MSS) is an urgent problem to be resolved in many countries. Safely using the nutrients within MSS to increase crop yield and enhance the fertility of poor soil could contribute to achieving sustainable development. An indirect use of MSS in ditches alongside Pennisetum hybridum plants was studied in field plots for 30 months and the contents of heavy metals and macronutrients were monitored in soil, sludge and plant samples. We found that the yield of P. hybridum was significantly increased by 2.39 to 2.80 times and the treated plants had higher N content compared with no sludge. In addition, the organic matter (OM) and N contents in the planted soil increased significantly compared with the initial soil. The OM content in the planted soil of the MSS treatment was 2.9 to 5.2 times higher than that with no sludge, and N increased by 2.0 to 3.8 times. However, MSS had no significant effect on the N, P and K contents in the soil at the bottom of the MSS ditch, and the content of heavy metals (Cd, Pb, Cu and Zn) were also within the safe range. Moreover, the moisture content and phytotoxicity of MSS after this indirect use were reduced and the heavy metal contents changed little, which is favorable to the further disposal of recovered MSS. Therefore, this indirect use of MSS is beneficial to agricultural production, soil quality and environmental sustainability.     

Remediation of arsenic contaminated soil by sulfidated zero-valent iron

• Sulfidation significantly enhanced As(V) immobilization in soil by zerovalent iron. • S-ZVI promoted the conversion of exchangeable As to less mobile Fe-Mn bound As. • Column test further confirmed the feasibility of sulfidated ZVI on As retention. • S-ZVI amendment and magnetic separation markedly reduced TCLP leachability of As. In this study, the influences of sulfidation on zero-valent iron (ZVI) performance toward As(V) immobilization in soil were systemically investigated. It was found that, compared to unamended ZVI, sulfidated ZVI (S-ZVI) is more favorable to immobilize As(V) in soil and promote the conversion of water soluble As to less mobile Fe-Mn bound As. Specifically, under the optimal S/Fe molar ratio of 0.05, almost all of the leached As could be sequestrated by>0.5 wt.% S-ZVI within 3 h. Although the presence of HA could decrease the desorption of As from soil, HA inhibited the reactivity of S-ZVI to a greater extent. Column experiments further proved the feasibility of applying S-ZVI on soil As(V) immobilization. More importantly, to achieve a good As retention performance, S-ZVI should be fully mixed with soil or located on the downstream side of As migration. The test simulating the flooding conditions in rice culture revealed there was also a good long-term stability of soil As(V) after S-ZVI remediation, where only 0.7% of As was desorbed after 30 days of incubation. Magnetic separation was employed to separate the immobilized As(V) from soil after S-ZVI amendment, where the separation efficiency was found to be dependent of the iron dosage, liquid to soil ratio, and reaction time. Toxicity characteristic leaching procedure (TCLP) tests revealed that the leachability of As from soil was significantly reduced after the S-ZVI amendment and magnetic separation treatment. All these findings provided some insights into the remediation of As(V)-polluted soil by ZVI.     

柠檬酸与磷共存对土壤吸附镉的影响

以武汉市棕红壤为研究材料,采用室内培养和等温平衡吸附实验,研究了磷和柠檬酸共存下对土壤吸附镉的影响;并模拟干湿交替实验,通过BCR连续提取,研究了不同剂量磷和柠檬酸处理后,经多次干湿交替后镉的形态变化.结果表明,经10 mg·L^-1 CdCl₂溶液处理后的土壤胶体,添加较低质量浓度（40 mg·L^-1）的磷对其吸附镉的影响不明显,而添加磷质量浓度较高（80 mg·L^-1）时可显著提高其对镉的吸附,吸附量较CK处理增加78 g·kg^-1,吸附率提高7.89%;向经40 mg·L^-1磷溶液处理过的土壤胶体中加入柠檬酸,可减弱其对镉吸附,且随柠檬酸浓度增高,抑制效果增加,而且对低剂量磷（40 mg·L^-1）处理的土壤胶体抑制作用更明显,加入1 mmol·L^-1与5 mmol·L^-1柠檬酸后,土壤胶体对镉的吸附率分别降低了30.89%与40.97%;而当磷处理质量浓度较高时,柠檬酸的影响则不显著.周期性的干湿交替显著促进土壤中镉由弱酸提取态及可还原态向可氧化态及残渣态的转变,即磷钝化的镉在柠檬酸的影响下,随干湿交替次数的增加,镉的有效性降低.     

新型防突装置对封隔器胶筒力学性能影响研

为了进一步保证封隔器安全坐封,提高封隔器胶筒的力学性能,基于现有成熟技术,设计了一种新型防突装置,分析了不同防突装置材料和结构参数对封隔器胶筒肩部突出、接触应力、Von Mises应力的影响。结果表明:新型封隔器肩部突出距离相比常规封隔器降低了63.35%,使胶筒不易被破坏,延长了胶筒的寿命;对防突装置材料和结构参数进行优选,选择材料为铝合金,距胶筒端面距离H=2.5mm,厚度B=0.5mm的新型防突装置;新型防突装置的设计与应用为封隔器坐封提供了安全保障。     

干旱区城市化对生态系统碳库的影响——以乌鲁木齐市为例

城市化是影响区域生态系统碳循环的主要原因,也是评估生态系统碳循环的最大不确定因素。论文利用1990与2010年Landsat TM数据,基于V-I-S城市土地覆被模型和决策树分类法,获得乌鲁木齐土地变化时空格局;结合野外实测数据和文献检索得到研究区不同土地覆被类型的土壤与植被碳密度,估算了城市土地变化对生态系统碳库的影响。结果表明：1）1990—2010年间,乌鲁木齐城市不透水地表（impervious surface areas, ISA）以中部南部内部填充与北部扩张的形式约增加62%,主要占用农田（27%）与荒漠（62%）。2）乌鲁木齐市生态系统碳库主体（95%）分布在土壤中,城市土地覆被变化导致约25%的碳库损失,由农田、裸土/残存荒漠以及城市绿地转变为ISA解释了68%的土壤有机碳和63%的植被碳损失量,其空间分布与ISA的扩张相一致。城市植被及其土壤具有较高的碳密度,合理的城市规划可以抵消部分因土地变化而损失的生态系统碳。     

区域用水环境经济综合效率及其影响因素——基于DEA和Malmquist指数模型

仅考虑经济效益而忽略环境损害的水资源利用效率指标不能全面反映区域用水的真实效果.本文基于DEA和Malmquist指数模型,提出区域用水环境经济综合效率(WEEE)概念及其评价方法,分析了2001~2012年河南省主要地市的WEEE及其影响因素.结果表明,研究时段内水资源利用保持了较高经济效率,但环境效率相对较差并由此拉低全省WEEE平均约2%;2012年WEEE未达到DEA有效的地市水资源投入平均冗余率约为18%,COD和NH₃-N平均超排率分别约为49%和49.2%,说明这些地市存在水资源利用低效和水污染物排放较高的问题.通过分析水资源利用的全要素生产率(TFP)发现,技术变化指数在研究时段内下降了2%,是抑制WEEE增长的最主要因素.为了在水资源利用过程中取得更好的环境和经济综合效益,河南省应加大对工农业节水和水污染防治的科技投入,并在严格控制用水总量的同时进一步加强水污染物的减排工作.     

典型山区燃煤型电厂周边土壤重金属形态特征及污染评价

为了揭示毕节金沙电厂周边土壤重金属（Hg、As、Cd、Cr、Cu、Pb和Zn）污染状况,在电厂周围采集了32个土壤表层样品,采用改进的BCR连续提取法进行形态分析,并以Hakanson潜在生态危害指数法、改性灰色聚类法及风险评估编码法（RAC）进行生态风险评估.结果表明：重金属含量变化具有一定的空间变异结构和空间分布特征,除了Cd和Cr的含量平均值低于贵州省土壤平均背景值外,其余重金属含量的平均值均大于该背景值.土壤中的大部分重金属主要以残渣态形式存在,而Cd主要以酸可提取态和可还原态存在,具有很强的环境危害.相关性分析结果显示,Hg与As、Cd表现为极显著相关,而Zn与其余重金属元素相关性都较弱.生态风险评价得出7种重金属的生态风险大小顺序为Cd > Hg > As > Cu > Pb > Zn > Cr,综合潜在生态风险指数（RI）平均值为129.72,处于中等生态风险.通过改性灰色聚类法对土壤重金属污染进行分析评价,表明电厂西面污染明显高于东面,且Hg和Cd为主要污染物;由风险评估编码法得出元素Cd有效态占18.17%,对环境构成中等风险等级,元素Cr和Zn对环境的危害处于低风险状态,元素Hg、Pb、As和Cu处于无风险状态.综合以上研究结果,金沙电厂土壤受到不同程度的重金属污染,应特别重视Hg和Cd这两种重金属污染的治理.     

太湖流域典型河流含氮物消减速率研究

采用自主研发的原位培养装置,开展了太湖流域典型河流水体含氮物消减速率及其影响因素研究.结果表明,总氮和氨氮消减速率呈现显著的空间差异性（P<0.05）,消减速率分别为（280.6±180.0）~（1458.8±725.7）mg/（m³·d）、（35.2±3.7）~（343.6±88.4）mg/（m³·d）,但硝态氮消减速率（44.3±7.6）~（521.2±19.2）mg/（m³·d））无显著的空间差异性（P>0.05）.微生物作用下氮素消减速率为95.0~733.1mg/（m³·d）,分别占含氮物总消减速率和总负荷的12.9%~50.3%和2.0%~13.4%,非微生物作用下氮素消减速率为180.0~996.7mg/（m³·d）,占含氮物总消减速率和总负荷的49.8%~87.0%和7.4%~25.7%,说明污染物进入水体,短期内微生物作用对含氮物消减速率的贡献较低.氮素消减速率与TN、NO₃^-、SS均呈线性相关关系（P<0.05）,说明TN、NO₃^-、SS在一定程度上是氮素消减作用的影响因素.     

中国主要河口海湾富营养化特征及差异分析

针对我国65个沿海河口海湾,基于自然地理数据及2007~2012年水质监测数据,采用箱须图法、聚类分析、相关性分析和主成分分析等方法,探讨河口海湾间富营养化特征、差异性及主要原因.结果表明,大型河口海湾的富营养化状态指标值相对较高,但河口海湾间富营养化响应指标值存在一定差异.DIN、PO₄^3--P和COD是河口海湾富营养化特征的第1主成分,DO和Chl-a是第2主成分,盐度、水深、潮差和面积等是第3主成分,河口海湾水体Chl-a浓度与TN入海量(P<0.01)、DIN(P<0.01)、PO₄^3--P(P<0.05)、流量(P<0.01)、温度(P<0.05)呈显著性正相关,同时与潮差(P<0.05)和盐度(P<0.01)和DO(P<0.01)呈显著性负相关.表明营养盐入海量增多是引起河口海湾一系列富营养化症状的主要因素,但河口海湾自然属性会调节其富营养化状态,造成系统间响应特征的差异.潮差小于2.5m的河口海湾,其营养盐转化效率明显高于潮差大于2.5m的河口海湾.说明河口海湾潮差可通过改变水体滞留时间、垂直混合和光照条件等,调节浮游植物生物量对营养盐的敏感性.此外,与外海的水体交换,海洋生物的捕食,及其他形态营养盐的供给等作用,也会影响河口海湾水体Chl-a的水平.人类活动带来的营养盐输入,以及河口海湾特有的自然属性,共同决定了其富营养化特征的差异和程度.     

三唑磷作用下翡翠贻贝抑制性消减杂交文库构建与分析

采用抑制性差减杂交技术,构建了三唑磷农药急性胁迫下翡翠贻贝雌贝性腺正反向消减杂交cDNA文库.正反向文库共有117个表达序列标签（expressed sequence tags,ESTs）与NCBI数据库中已知功能蛋白具较高同源性,假定蛋白12种,另有195个ESTs未检索到同源序列.正向文库中含有细胞周期蛋白、性激素合成蛋白、DNA修复蛋白、能量代谢相关蛋白等一系列与生殖、应激适应和代谢相关的转录本信息,而反向文库中的差异ESTs主要涉及DNA复制、转录和翻译调控基因以及骨架蛋白.结果表明三唑磷对翡翠贻贝的毒性涉及到生殖调控、能量代谢、应激适应、转录翻译调控等生理代谢的多个方面,正向文库中发现的几种生殖调控基因（细胞周期蛋白、周期蛋白依赖性蛋白激酶、合子DNA复制许可因子、精子特异性蛋白、雌激素硫酸转移酶和卵黄膜卵透明带域蛋白）可能是三唑磷生殖干扰毒性作用过程中的关键基因,这为有机磷农药的生殖毒性探索提供了基础数据.