Soil enzyme activities and their indication for fertility of urban forest soil

To reveal the biological characteristics of urban forest soil and the effects of soil enzyme on soil fertility as well as the correlation between physicochemical properties and enzyme activities, 44 urban forest soil profiles in Nanjing were investigated. Basic soil physicochemical properties and enzyme activities were analyzed in the laboratory. Hydrogen peroxidase, dehydrogenase, alkaline phosphatase, and cellulase were determined by potassium permanganate titration, TTC (C₁₉H₁₅N₄·Cl) colorimetry, phenyl phosphate dinatrium colorimetry, and anthrone colorimetry, respectively. The result showed that soil pH, organic carbon (C), and total nitrogen (N) had great effects on hydrogen peroxidase, dehydrogenase, and alkaline phosphatase activities in 0–20 cm thick soil. However, pH only had great effect on hydrogen peroxidase, dehydrogenase, and alkaline phosphatase activities in 20–40 cm thick soil. Hydrogen peroxidase, dehydrogenase, and alkaline phosphatase were important biological indicators for the fertility of urban forest soil. Both in 0–20 cmand 20–40 cmsoil, soil enzyme system (hydrogen peroxidase, dehydrogenase, alkaline phosphatase, and cellulase) had a close relationship with a combination of physicochemical indicators (pH, organic C, total N, available K, available P, cation exchange capacity (CEC), and microbial biomass carbon (C_mic)). The more soil enzyme activities there were, the higher the fertility of urban forest soil.     

天津市滨海河流N2O扩散通量及控制因子

河流是大气温室气体重要的排放源.为了探讨天津市典型景观滨海河流N₂O释放空间特征及影响因素,以天津市6条不同土地利用类型的滨海河流为研究对象,通过顶空-气相色谱法测定了N₂O浓度、饱和度和扩散通量.结果表明,天津市不同景观河流N₂O浓度都处于过饱和状态,表现为大气N₂O的源;N₂O浓度、饱和度和扩散通量均值为（23.85±15.20）nmol·L^-1、（309.71±197.38）%和（27.04±16.46）μmol·（m²·d）^-1,范围分别为12.70～115.69 nmol·L^-1、 164%～1 502%和9.17～244.79μmol·（m²·d）^-1.天津市不同土地利用类型河流N₂O浓度和扩散通量具有较大的空间异质性,表现为：排污河>城市河流>郊区河流>农业河流.天津滨海河流N₂     

壬基酚的环境生物地球化学研究进展及对新污染物管理的建议

近年来,我国大气环境、水环境和土壤环境质量得到一定的改善,“碧水蓝天”已经成为常态.但随着持久性有机污染物、内分泌干扰物、抗生素和微塑料等新污染物在环境中不断被检出,新污染物正逐步受到广泛的关注,壬基酚作为一种典型的内分泌干扰物也备受研究人员的关注.系统地概括了我国水体中壬基酚的环境行为和暴露水平,并基于风险商法和联合概率曲线法对壬基酚可能造成的生态风险进行了评估.结果表明,壬基酚对水生生物的毒性效应主要包括急性毒性、生长发育毒性、雌激素效应和繁殖毒性;壬基酚在我国主要流域水体中普遍存在,其浓度平均值在60～1 000 ng·L^-1,浓度最高值可达4 628 ng·L^-1;基于风险商法和联合概率曲线法的风险评估结果表明,壬基酚对我国主要流域里的水生生物均存在一定的风险.最后,总结了目前比较常用的壬基酚处理处置和风险管控技术,比较了国际上内分泌干扰物的监管方法,针对我国在新污染物环境管理中存在的问题,提出了针对性政策建议,研究结果可以为我国新污染物管理和管控提供参考.     

某型飞机4号油箱结构损伤分析及修复评估

目的 某型双座机使用中发现4号油箱存在不同程度结构损伤,分析其损伤原因和制定修理方案。方法 对4号油箱结构状态进行深入检查评估后,从结构损伤过程、载荷情况、设计制造和外场使用等方面综合分析损伤原因。对实际损伤结构进行强度计算和评估,制定结构损伤补强修理方案,并提出修理改进建议。结果 通过分析得出,损伤原因主要是4号油箱局部存在设计制造缺陷,且飞机在作大过载飞行时,4号油箱可能处于满油或大量余油的高负载状态。根据损伤原因制定的修理方案合理可行,通过了静强度校核和评估。结论 基于该损伤结构提出的修理方案通过实际修理验证,能够满足油箱结构强度设计要求,提出的改进建议能够改善飞机疲劳品质。     

工程项目现场安全标志有效性评价

为改善工程项目现场作业安全状况,需要对安全标志的有效性进行评价。通过划分施工人员的认知行为阶段,从人机工程学系统优化的角度构建安全标志有效性评价指标体系,确立指标打分规则,采用网络层次分析法(ANP),运用超级决策(SD)软件确定指标权重、综合评分,并加以示例说明。结果表明:安全标志的有效性受注意阶段的显著性、识别阶段的可理解性、判断阶段的安全倾向性和行为阶段的易遵守性交互影响,其中,安全倾向性权重值最高。     

铜陵市铜尾矿土壤动物群落生态研究

对安徽省铜陵市铜尾矿地6种生境中土壤动物群落进行野外调查和室内分析，研究不同弃置堆放时间的铜尾矿地土壤的动物群落结构及其与尾矿基质理化性质、植被状况等生境条件之间的关系。结果表明，尾矿堆放时间、区位地貌和植被状况的不同，尾矿基质的理化性质发生变化，导致土壤动物的种类组成和数量分布具有明显差异。土壤动物在土体中的表聚性强，绝大部分集中分布于A层(0～5cm)；土壤的物理性质越稳定，土壤动物越丰富；土壤肥力越高，土壤动物越丰富多样。即尾矿地土壤的生境条件越优越，土壤动物群落的物种丰富度越大，个体数量分布越多，群落多样性越高。这些研究结论为尾矿区的生态修复和可持续利用提供了参考依据。     

城市地表汞含量及释放通量影响因素分析

测定了长春市不同类型地表汞含量及其释放通量，分析了地表汞释放通量的影响因素。研究结果表明，不同地表土样的汞含量存在很大的差异；煤炭堆放地和沥青地地表汞含量较高，应引起足够的重视。地表汞释放通量受地表汞含量、地表类型、降水、太阳辐射等因素的影响。降水期间或降水后期地表汞释放通量明显增加。可见，地表汞释放是一个动态过程，随时间和空间而变化。     

Lead biosorption and desorption by intact and pretreated spirulina maxima biomass

In order to search for locally available and untried biomaterials in China with high removal capacity of heavy metals from wastewater, the feasibility of Spirulina maxima as biosorbent for lead removal and recovery from aqueous solution was investigated. The lead biosorption was studied by using intact biomass and pretreated biomass of S. maxima. The effects of operational conditions (e.g. pH, contact time, biomass concentration etc.) on lead biosorption were investigated. The biosorption was solution pH dependent and the maximum adsorption was obtained at a solution pH of about 5.5. The adsorption equilibrium was reached in 60 min. The biosorption followed the Freundlich isotherm model. The maximum removal ratios of lead were about 84% in intact biomass and 92% in pretreated biomass. The lead adsorbed could be desorbed effectively by 0.1 M nitric acid, EDTA and hydrochloric acid. The results in this study indicated that pretreated biomass of S. maxima was a promising candidate for removing lead from wastewater.     

紫外活化甲酸产二氧化碳阴离子自由基还原Cr (VI)的研究

研究高效还原技术是去除废水中Cr（VI）的有效手段,本研究提出了一种新颖有前景的基于紫外（UV）活化甲酸（HCOOH）产还原性二氧化碳阴离子自由基（CO₂^•;-）去除Cr（VI）的方法.通过对比UV、HCOOH、UV/HCOOH三种体系对Cr（VI）还原效率和电子自旋共振（EPR）对体系中自由基的检测研究了其活化原理和还原机制.结果表明UV能显著活化HCOOH产生CO₂^•-（α_H=19.08G,α_N=15.86G,g=2.0036）.此外,试验考察了主要影响因素对Cr（VI）去除效果的影响,包括初始Cr（VI）浓度、甲酸投加量、初始pH值、反应温度、有机污染物以及水中常见阴离子.结果显示当甲酸浓度为40mmol/L,Cr（VI）初始浓度为10mg/L,反应时间在60min内,UV/HCOOH体系对Cr（VI）的去除率能达到100%.在酸性条件下（pH≤3.5）能显著促进Cr（VI）的还原,且Cr（VI）去除效率随着初始HCOOH浓度和反应温度升高而增加.进一步研究表明,该体系下NO₃^-对Cr（VI）的还原有着显著的促进作用,而Cl^-、HCO₃^-和对硝基苯酚（pNP）则有抑制作用.不同温度下Cr（VI）去除率与时间关系的拟合结果表明,当反应时间t³;40min,UV/HCOOH体系去除Cr（VI）过程遵循准一级反应动力学,根据不同温度下对应的反应速率常数k,结合阿伦尼乌斯方程,计算求得准一级反应的活化能为15.9kJ/mol.     

Volatile organic compound emissions from straw-amended agricultural soils and their relations to bacterial communities: A laboratory study

A laboratory study was conducted to investigate volatile organic compound(VOC) emissions from agricultural soil amended with wheat straw and their associations with bacterial communities for a period of 66 days under non-flooded and flooded conditions. The results indicated that ethene, propene, ethanol, i-propanol, 2-butanol, acetaldehyde, acetone,2-butanone, 2-pentanone and acetophenone were the 10 most abundant VOCs, making up over 90% of the total VOCs released under the two water conditions. The mean emission of total VOCs from the amended soils under the non-flooded condition(5924 ng C/(kg·hr)) was significantly higher than that under the flooded condition(2211 ng C/(kg·hr)). One "peak emission window" appeared at days 0–44 or 4–44, and over 95% of the VOC emissions occurred during the first month under the two water conditions. Bacterial community analysis using denaturing gradient gel electrophoresis(DGGE) showed that a relative increase of Actinobacteria, Bacteroidetes, Firmicutes and γ-Proteobacteria but a relative decrease of Acidobacteria with time were observed after straw amendments under the two water conditions. Cluster analysis revealed that the soil bacterial communities changed greatly with incubation time, which was in line with the variation of the VOC emissions over the experimental period. Most of the above top 10 VOCs correlated positively with the predominant bacterial species of Bacteroidetes, Firmicutes and Verrucomicrobia but correlated negatively with the dominant bacterial species of Actinobacteria under the two water conditions. These results suggested that bacterial communities might play an important role in VOC emissions from straw-amended agricultural soils.