零价铁-氧化剂联合降解土壤中硝基氯苯及土壤性质变化

硝基氯苯是重要的化工原料和中间体,其在土壤中的不断积累对生态环境和人体健康构成了严重威胁.高级氧化修复技术可以将有机污染物直接或间接矿化为CO_2和H_2O,从而成为近年来研究的重点.本文针对南京某化工厂搬迁遗留的硝基氯苯污染的场地土壤,研究了零价铁还原与氧化剂氧化的联合体系对硝基氯苯的降解率,并对反应过程的中间产物和动力学进行了分析,研究了降解后土壤性质的变化.结果表明,当采用KMnO_4、Fenton试剂、30%H_2O_2和Na_2S_2O_44种氧化剂直接氧化时,土壤中硝基氯苯的降解率分别为75.0%、62.9%、58.1%和41.5%;经零价铁还原1 h后,再施加氧化剂氧化处理,硝基氯苯降解率大幅提高,分别达到91.5%、88.5%、87.4%和70.4%.零价铁还原体系中间产物氯代苯胺浓度4 h时达到最大,施加氧化剂后迅速下降,4 h后下降至最低并维持较稳定水平;硝基氯苯氧化反应在单一氧化剂反应体系符合一级动力学方程,但在零价铁与氧化剂联合反应体系符合二级动力学方程;降解后的土壤性质有较大变化,CEC、TOC和土壤养分显著下降,Eh和EC显著增加,土壤pH除施加Na2S2O4下降显著外,施加KMnO_4、Fenton试剂、30%H_2O_2时下降较小,但同时添加零价铁土壤pH下降显著;土壤全N、全P、全K变化不显著,这些可为修复后土壤的再利用提供数据参考.     

质子化壳聚糖的除磷性能

壳聚糖是一类无毒无害的天然高分子絮凝剂,为了提高壳聚糖在污水处理中的除磷性能,采用硫酸溶液对壳聚糖进行质子化改性;考察了质子化度(硫酸溶液pH值)、吸附时间以及原水pH值对除磷效率的影响。研究结果表明,质子化度越大,总磷去除效率越高;在吸附时间为40～50 min的范围内,总磷去除率最大;原水pH值对质子化壳聚糖的总磷去除效率有明显影响,在质子化度较低时(硫酸溶液pH值≥3),随着原水pH值的增加,总磷去除率降低,在质子化度较高时(硫酸溶液pH值=2),在原水pH=6时,总磷去除率最大;质子化壳聚糖的吸附过程较好地遵循Lagergren准二级动力学模型和Langmuir吸附等温方程,吸附热力学参数ΔH<0,ΔG<0,ΔS<0,吸附过程表现为放热、自发的单分子层化学吸附过程。     

Characteristics and driving factors of marsh changes in Zhalong wetland of China

Zhalong National Nature Reserve in the northeast of China is a large wetland and a habitat of hundreds species of fauna and flora. The rare red-crowned crane is one kind of endangered birds in it. Recently, Zhalong wetland is shrinking and it encounters many problems including occasional fires, bad water quality, human activities, etc. In order to find out a proper way to protect and restore the wetland, this study, using a geographic information system, the global positioning system and remote sensing techniques, analyses the spatial characteristics of the changes in marsh landscape pattern and examines the driving factors for these changes. Data sources include 8 Landsat Thematic Mapper satellite images of Zhalong area in the period of 1986–2002 and the investigation information on site. Based on the analysis of changes of marsh area and annual precipitation during the 16 years, it is found that there is a close correlation between annual precipitation and marsh area. It means that climate is one of driving factors of marsh pattern changes. To understand influences of other kinds of land uses on marsh spatial distribution in Zhalong wetland, this paper analyses the relationship between marsh and different kinds of land uses, such as water surface, residential area, farmland, salina land and grass land, respectively. According to the patch analysis theory, a fragmental index and a fractal dimension of the marsh are calculated with perimeter-area method. The results indicate that the marsh pattern is affected by human activities significantly. In addition, the location alteration of marsh centroid point over the 16 years is studied. The movement trace of marsh centroid point is concerned with different hydrological situation in different areas of the wetland. In summary the characteristics of the marsh landscape pattern evolution during the 16 years are affected by multiple driving factors. The main driving factors are climate, human activities, distribution of other kinds of land uses and hydrological situation in different areas.     

Disinfection and removal of human pathogenic bacteria in arctic waste stabilization ponds

Wastewater stabilization ponds (WSPs) are commonly used to treat municipal wastewater in Arctic Canada. The biological treatment in the WSPs is strongly influenced by climatic conditions. Currently, there is limited information about the removal of fecal and pathogenic bacteria during the short cool summer treatment season. With relevance to public health, the objectives of this paper were to determine if treatment in arctic WSPs resulted in the disinfection (i.e., removal of fecal indicator bacteria, Escherichia coli) and removal of selected human bacterial pathogens from the treated effluent. The treatment performance, with focus on microbial removal, was assessed for the one-cell WSP in Pond Inlet (Nunavut [NU]) and two-cell WSP in Clyde River (NU) over three consecutive (2012–2014) summer treatment seasons (late June-early September). The WSPs provided a primary disinfection treatment of the wastewater with a 2–3 Log removal of generic indicator E. coli. The bacterial pathogens Salmonella spp., pathogenic E. coli, and Listeria monocytogenes, but not Campylobacter spp. and Helicobacter pylori, were detected in the untreated and treated wastewater, indicating that human pathogens were not reliably removed. Seasonal and annual variations in temperature significantly (p < 0.05) affected the disinfection efficiency. Improved disinfection and pathogen removal was observed for the two-cell system in Clyde River as compared to the one-cell system in Pond Inlet. A quantitative microbial risk assessment should be performed to determine if the release of low levels of human pathogens into the arctic environment poses a human health risk.     

生物炭的制备及其镁改性对污染物的吸附行为研究

以小麦和玉米秸秆为原料,于不同温度下制备了生物炭样品,并采用氯化镁(MgCl_2)、乙酸镁(Mg(CH_3COO)_2)和硝酸镁(Mg(NO_3)_2)对秸秆及其生物炭进行改性.通过分析各生物炭产率、pH、元素分析、比表面积、CEC、XRD及FT-IR,探究了生物炭理化性质的变化规律.各样品对氨氮、Pb(Ⅱ)及乙草胺的吸附试验结果表明:小麦秸秆经Mg(CH_3COO)_2改性后得到的生物炭的饱和吸附量最大;对3种吸附质的吸附过程均符合准二级吸附动力学方程;低浓度下吸附过程均可自发进行,对氨氮的吸附符合Langmuir模型且以离子交换作用为主,对Pb(Ⅱ)的吸附符合Freundlich模型且以离子交换作用为主,对乙草胺的吸附符合Langmuir模型且以分配、氢键和π-π电子受体供体作用为主.     

中国农村环境问题根源探析

农村环境问题是中国环境保护面临的又一严峻挑战,深入探讨其成因是解决问题的关键.中国农村环境问题是多方面因素共同作用的结果,但其根本是城乡居民经济水平差距的日趋扩大使农村发展重经济轻环境、城乡环境权益的不平等使农村承担城市转嫁污染而得不到补偿,以及城乡统筹发展过程中未真正将农村与城市平等对待的偏差.     

2019年昆明市一次臭氧污染过程特征及成因分析

针对2019年4月22—26日昆明出现的臭氧污染过程,利用昆明空气质量数据、气象观测数据、NCEP及ERA5再分析资料,综合气象条件、天气形势、外源输送条件,分析本次污染过程的特征及其成因.结果表明：①本次臭氧污染过程O₃浓度呈“单峰型”变化,7：00—8：00出现每日的谷值,13：00—15：00出现每日的峰值.②高温低湿条件利于O₃的形成,温度为24~29 ℃,相对湿度为15%~35%,风向为东南风和西南风时O₃浓度易超标.③此次污染过程中存在O₃的水平和垂直外源输送,在天气系统的作用下,近地层静稳天气导致污染物的积累和生成,并利于将云南以西区域高浓度O₃向昆明上空水平输送;平流层下层-对流层上层的垂直入侵使高层含高浓度O₃的空气向对流层及近地层输送.④HYSPLIT后向轨迹进一步验证,污染过程外源输送的气团来源于云南以西的中低纬度地区,污染物浓度与气团移动路径及天气系统相吻合.     

废旧车用动力电池安全放电研究

在动力电池回收处理流程中,对于发生过进水、过火、碰撞等情况的危险性动力电池需要进行放电安全处理。此外,动力电池从电动汽车上退役时残余电压很高,动力电池单体带电拆解极易发生起火甚至爆炸,拆解前也需要进行放电处理。以退役车用锂离子动力电池单体为研究对象,对比物理放电和化学放电的安全性,考察放电的安全截止电压、戳穿安全阀、电解质浓度对化学放电的影响。结果表明,电池电压值高于1.0 V时,电池拆解会产生火星,极易起火,电压值不高于1.0 V可实现安全拆解。物理放电后电池电压会反弹,拆解时仍有安全风险;化学放电后电池电压不反弹,可实现安全拆解。化学放电时戳穿安全阀并添加5%的Na Cl可满足产业化放电要求,SOC=100%的动力电池放电至安全截止电压需要15.3 h。对于10 Ah以上的动力电池,戳入深度应控制在5 mm以内,10 Ah以内的动力电池不建议戳穿安全阀。     

Measuring technical efficiency associated with environmental investment: does market competition and risk matters in banking sector

Environmental Science and Pollution Research - This paper investigates the impact of several comprehensive risks such as credit risk, capital risk, liquidity risk, and insolvency risks on Pakistani...     

苏州园林水体生态化治理之路探讨

水是苏州园林的重要组成要素,随着城市的迅猛发展,园林水脉割断、水生生态系统不完善,水体自净能力降低,苏州园林的水环境状况受到很大影响。通过对苏州园林传统水环境保护手法的梳理,提出通过改造河池护坡,修复水生生态系统等师法自然的方法,开发纳米气泡法、生态基法等生态新技术,以及加强园林水循环,重塑优美的园林水景观。