Revealing the changes of bacterial community from water source to consumers tap: A full-scale investigation in eastern city of China

This study profiled the bacterial community variations of water from four water treatment systems, including coagulation, sedimentation, sand filtration, ozonation-biological activated carbon filtration (O₃-BAC), disinfection, and the tap water after the distribution process in eastern China. The results showed that different water treatment processes affected the bacterial community structure in different ways. The traditional treatment processes, including coagulation, sedimentation and sand filtration, reduced the total bacterial count, while they had little effect on the bacterial community structure in the treated water (before disinfection). Compared to the traditional treatment process, O₃-BAC reduced the relative abundance of Sphingomonas in the finished water. In addition, ozonation may play a role in reducing the relative abundance of Mycobacterium. NaClO and ClO₂ had different effects on the bacterial community in the finished water. The relative abundance of some bacteria (e.g. Flavobacterium, Phreatobacter and Porphyrobacter) increased in the finished water after ClO₂ disinfection. The relative abundance of Mycobacterium and Legionella, which have been widely reported as waterborne opportunistic pathogens, increased after NaClO disinfection. In addition, some microorganisms proliferated and grew in the distribution system, which could lead to turbidity increases in the tap water. Compared to those in the finished water, the relative abundance of Sphingomonas, Hyphomicrobium, Phreatobacter, Rheinheimera, Pseudomonas and Acinetobacter increased in the tap water disinfected with NaClO, while the relative abundance of Mycobacterium increased in the tap water disinfected with ClO₂. Overall, this study provided the detailed variation in the bacterial community in the drinking water system.     

On-going nitrification in chloraminated drinking water distribution system (DWDS) is conditioned by hydraulics and disinfection strategies

Within the drinking water distribution system (DWDS) using chloramine as disinfectant, nitrification caused by nitrifying bacteria is increasingly becoming a concern as it poses a great challenge for maintaining water quality. To investigate efficient control strategies, operational conditions including hydraulic regimes and disinfectant scenarios were controlled within a flow cell experimental facility. Two test phases were conducted to investigate the effects on the extent of nitrification of three flow rates (Q = 2, 6, and 10 L/min) and four disinfection scenarios (total Cl₂=1 mg/L, Cl₂/NH₃-N=3:1; total Cl₂=1 mg/L, Cl₂/NH₃-N=5:1; total Cl₂=5 mg/L, Cl₂/NH₃-N=3:1; and total Cl₂=5 mg/L, Cl₂/NH₃-N=5:1). Physico-chemical parameters and nitrification indicators were monitored during the tests. The characteristics of biofilm extracellular polymetric substance (EPS) were evaluated after the experiment. The main results from the study indicate that nitrification is affected by hydraulic conditions and the process tends to be severe when the fluid flow transforms from laminar to turbulent (2300<Re<4000). Increasing disinfectant concentration and optimizing Cl₂/NH₃-N mass ratio were found to inhibit nitrification to some extend when the system was running at turbulent condition (Q = 10 L/min, Re = 5535). EPS extracted from biofilm that was established at the flow rate of 6 L/min had greater carbohydrate/protein ratio. Furthermore, several nitrification indicators were evaluated for their prediction efficiency and the results suggest that the change of nitrite, together with total organic carbon (TOC) and turbidity can indicate nitrification potential efficiently.     

Sources, distribution, and risk assessment of organochlorine pesticides in Nairobi City, Kenya

The distribution and sources of organochlorine pesticides (OCPs) in air and surface waters were monitored in Nairobi City using triolein-filled semipermeable membrane devices (SPMDs). The SPMDs were extracted by dialysis using n-hexane, followed by cleanup by adsorption chromatography on silica gel cartridges. Sample analysis was done by GC-ECD and confirmed by GC–MS. Separation of means was achieved by analysis of variance, followed by pair-wise comparison using the t-test (p≤ 0.05). The total OCPs ranged between 0.018 – 1.277 ng/m³ in the air and <LOD – 1391.000 ng/m³ in surface waters. Based on the results, the means of Industrial Area, Dandora and Kibera were not significantly different (p≤ 0.05), but were higher (p≤ 0.05) than those of City square and Ngong’ Forest. The results revealed non-significant (p≤ 0.05) contribution of long-range transport to OCP pollution in Nairobi City. This indicated possible presence of point sources of environmental OCPs in the city. The water-air fugacity ratios indicated that volatilization and deposition played an important role in the spatial distribution of OCPs in Nairobi City. This indicated that contaminated surface waters could be major sources of human exposure to OCPs, through volatilization. The incremental lifetime cancer risks (ILCR) determined from inhalation of atmospheric OCPs were 2.3745  ×  10^?13 – 1.6845  ×  10^?11 (adult) and 5.5404  ×  10^?13 – 3.9306  ×  10^?11 (child) in the order: Dandora > Kibera > Industrial Area > City Square > Ngong’ Forest. However, these were lower than the USEPA acceptable risks, 10^?6 – 10^?4. This study concluded that atmospheric OCPs did not pose significant cancer risks to the residents.     

2006-2017年四川盆地MODIS气溶胶光学厚度时空变化特征

四川盆地地形复杂、气候特殊,是我国颗粒物污染高发地.为探究四川盆地气溶胶分布和周期变化特征,深入认识气溶胶污染特性及其气候效应,结合卫星遥感探测方法,利用2006-2017年MODIS C006 3 km AOD（气溶胶光学厚度）产品,分析了四川盆地AOD的时空特征.结果表明:①MODIS AOD（MODIS数据反演的气溶胶光学厚度）与太阳光度计CE318观测的AOD、ρ（PM_2.5）、ρ（PM₁₀）线性相关系数分别为0.78、0.77、0.75,表明MODIS C006 3 km AOD产品适用于四川盆地颗粒物污染研究.②四川盆地AOD平均值范围为0.1~1.3,其中,成都平原和四川盆地东南部地区是AOD高值（AOD值>1.0）中心,四川盆地周边高海拔区AOD均小于0.3.③2006-2017年AOD年均值范围为0~2.5,整体呈"倒N型"曲线下降,其峰值和谷值分别出现在2013年和2017年;2013年AOD大于1.0的区域占四川盆地的34.1%,是12 a中颗粒物污染最重的一年;2017年AOD小于0.3的面积占57.1%.④AOD季节性变化呈春季最大、夏季次之、秋季最小的特征.⑤AOD月变化呈"双峰型"波动特征,AOD月均值范围为0~2.5,其中,2-5月AOD月均值均大于0.7,8月AOD月均值为0.6,11-12月AOD月均值均小于0.5.研究显示,四川盆地颗粒物污染防治应以成都平原城市群和四川省南部城市群为主,应重点控制细颗粒物排放,合理安排工业企业的周期性生产强度.      

德州市采暖季环境空气含氮/硫物质的污染及气-粒分配特征

为探究德州市采暖季环境空气中含氮/硫物质的污染特征、气-粒分配规律及影响因素,对2017年11月10日—2018年3月15日德州市市区环境空气监测站在线离子色谱分析仪监测的水溶性离子及气态前体物质量浓度的小时数据进行了分析.结果表明:①德州市环境空气监测站ρ（NO₃-）、ρ（SO₄2-）和ρ（NH₄+）平均值分别为（18.36±18.55）（12.74±10.92）（9.60±8.75）μg/m3,在2018年1月三者均达到最高值;对比PM_2.5及气态含氮/硫物质的质量浓度发现,ρ（PM_2.5）和ρ（SO₂）在2017年12月、2018年1月和2018年2月的月均值均较高,而ρ（SO₂）与ρ（SO₄2-）、ρ（NH₃）与ρ（NH₄+）均在日间（08:00—17:00）出现波峰.②对颗粒态和气态含氮/硫物质质量浓度日均值进行双变量相关分析发现,ρ（SO₄2-）、ρ（NO₃-）、ρ（NH₄+）两两之间的相关系数均高于0.75,表明二次离子的形成机制相似;而ρ（NH₃）、ρ（NO₂）、ρ（NO）、ρ（SO₂）两两之间均不存在显著相关,说明这些气态前体物来自不同的局部排放源.③过剩NH₃指数（F_N）平均值为0.49±0.16,说明采样时段大气处于富氨环境,过剩的NH₃会与气态HNO₃生成NH₄NO₃,因此NO₃-气溶胶的形成主要受HNO₃的影响或限制.④相对湿度是影响ρ（PM_2.5）最重要的气象因素,高湿环境会促进二次离子的转化.研究显示,冬季采暖排放会增加环境空气中含氮/硫物质的质量浓度,气象因素（尤其是相对湿度）对含氮/硫物质的气-粒分配也有一定影响.      

江西定南县离子型稀土尾矿周边水体氮污染状况与分布特征

为探究"稀土王国"江西省赣南地区离子型稀土矿对周边水体环境的影响,以离子型稀土矿分布密集区定南县濂江月子河流域和龙迳河龙头流域为研究对象,综合分析研究区特征污染物ρ（NH₄+-N）空间分布特征,采用相关性分析和主成分分析揭示其主要污染来源及影响因素.结果表明:①离子型稀土矿停产整顿半年后,濂江月子河流域和龙迳河龙头流域ρ（NH₄+-N）超过1.00和2.00 mg/L的采样点分别达72%和68%;pH范围为2.95~7.66,平均值分别为6.23和5.53,水体总体上偏酸性;ρ（TN）、ρ（NH₄+-N）、EC与ρ（NO₃--N）变异系数较大,均介于0.80~1.50之间.②相关性分析结果显示,ρ（NH₄+-N）与ρ（TN）、EC均呈极显著正相关（P < 0.01）;ρ（NH₄+-N）与pH呈显著负相关（P < 0.05）.③流经稀土尾矿区的水体中ρ（NH₄+-N）随距离增加呈现明显的空间梯度分布特征,即距稀土矿区边界200 m处水体中ρ（NH₄+-N）最高（12.20~200.00 mg/L）,其次为1.15 km内（3.69~11.80 mg/L）及3.5 km以上水体（0.80~1.51 mg/L）,矿区周边未受到采矿活动影响的水体中ρ（NH₄+-N）最低（0.03~0.15 mg/L）.④PCA结果表明,2条河流的主要环境影响因子为ρ（TN）、ρ（NH₄+-N）、pH和EC,主要受到周边稀土矿山尾矿的强烈影响.研究显示,离子型稀土矿原位浸矿开采停产半年后,重点小流域水体中ρ（NH₄+-N）高概率超标的现状仍然存在,受稀土开采活动影响较大.建议进一步开展重点小流域NH₄+-N剩余"库容"精算和矿山周边地表水定期监测.      

随机振动响应峰值因子的预计理论研究

简要介绍了超越概率理论、超越频次理论、损伤等效理论和功率谱密度(PSD)的时域拟合理论等4种常见的峰值因子预计理论,并基于三角级数提出了一种新的预计理论。结合试飞加速度数据样本,对比分析超越频次理论、PSD时域拟合理论和三角级数理论的预估精度。研究表明,上述4种常见的预计理论本质上属于统计学理论;PSD时域拟合理论预计的峰值因子波动较大,峰值因子与归一化次数满足高斯分布;三角级数理论的预估精度较高,但缺乏离散峰个数的合理判据。     

海绵城市地块汇水区颗粒污染物的传输

目前我国海绵工程建设多集中在地块汇水区单元内开展,通过多个低影响开发(LID)设施协同完成地表径流水质水量的调控,但基于地块汇水区尺度下城市面源污染的产生和控制效果鲜有报道.本研究比较分析了不同硬化率地块汇水单元内的面源颗粒污染物晴天累积、降雨冲刷、地表径流及径流输出负荷状况.结果表明,地块汇水单元内硬质路面是面源颗粒污染物贡献的最主要的下垫面类型,中硬化率(61.1%)地块和高硬化率(73.6%)地块路面街尘累积量分别约占汇水区单元的88.4%(2.22～12.51 g·m~(-2))和90.1%(4.99～33.43 g·m~(-2)),对径流SS的输出贡献比率分别约为91.7%(0.97～7.34 g·m~(-2))和90.5%(0.92～18.77 g·m~(-2)),降雨径流SS污染负荷占比分别约为95.2%和83.1%,经LID设施处理后输出径流污染负荷约为地表径流的24.0%和40.2%.硬质路面的街尘晴天累积及降雨冲刷以150μm为主,地表径流及输出径流则以50μm粒径段为主,同时地块不透水比例的增加,细粒径(105μm)颗粒物的累积及冲刷分布增大(24.4%和106.4%),而粒径50μm的颗粒物在路面径流中的分布减小(12.4%).屋面的街尘累积、冲刷及降雨径流的粒径分布状况与硬质路面大致相似,但中硬化率地块(1 000μm)和高硬化率地块(250～450μm、45μm)在3个粒径段范围的颗粒物累积和冲刷相较于路面街尘粒径分布明显增加(1 000μm:58.1%和108.5%; 250～450μm:72.9%和41.8%;45μm:59.2%和64.8%).以上结果揭示了颗粒污染物在地块汇水区尺度下的污染全过程(累积-冲刷-输出)分布及LID设施对地块整体SS污染负荷的控制效果,可为地块汇水单元内LID设施工程绩效的科学评估提供重要参考.     

新时代国土整治与生态修复转型思考

针对全球变化影响下的国土空间和生态系统,生态文明建设和国土空间规划是中国在新时代的积极响应,国土整治与生态修复的转型和提升成为必然要求。在介绍国土整治与生态修复概念内涵的基础上,指出中国国土空间生态环境问题的复杂性和生态文明建设的新理念要求决定了国土整治与生态修复的转型。从工作理念、理论基础、技术体系和制度建设等方面,分析了当前国土整治与生态修复工作中存在的不足,主要包括整体综合理念滞后、理论基础体系欠缺、技术支撑相对薄弱、体制机制不尽完善等方面。针对这些不足,提出了新时代国土整治与生态修复转型的路径和策略,主要策略包括强化系统思维、提升理论体系、加强技术支撑、完善机制建设等内容,以期为国土整治与生态修复推进美丽中国建设提供科学依据。     

基于生态系统服务供需关系的广西县域国土生态修复空间分区

国土生态修复是我国土地整治战略发展的需求,其空间分区与管控是实施国土整治与生态修复差别化建设的前提条件。以广西各县市为研究单元,在测算和分析生态系统服务供给量和需求量基础上,利用象限匹配法、双变量局部空间自相关和供需协调度来定量分析生态系统服务供需匹配关系、空间聚集程度和协调关联性,进而探讨和划分广西国土生态修复的空间分区及其管控措施与建议。研究表明：（1）广西各县市生态系统服务供给和需求差异明显。环绕广西的四周山林地和重点生态功能区县生态系统服务供给量较高,大中城市区则较低。生态系统服务需求量自东南向西北逐渐减少。（2）广西生态系统服务供需空间匹配呈现高供高需型、低供高需型、低供低需型、高供低需型四种类型,供需局部空间自相关以高-低或低-高的空间聚集为主,且生态系统服务供需协调度平均值为0.531,处于一般均衡。（3）结合生态系统服务供需匹配四类特征和广西地理环境条件,将广西各县域划分为10个分区,并针对各分区提出差异化整治措施和建议。总体上,生态系统服务高供高需型的区域应以保育为主、培育为辅,防止过度开发;高供低需型的区域以保护为主,提高管理水平;低供高需型的区域应以综合改良为主,提高土地效益;低供低需型的区域应以国土生态重构或重建为主,侧重恢复生态系统。