Chemical characteristics of road dust PM2.5 fraction in oasis cities at the margin of Tarim Basin

In order to understand the compositions characteristics of particulate matter with aerodynamic diameter less than 2.5 μm (PM_2.5) fraction in road dust (RD_2.5) of oasis cities on the edge of Tarim Basin, 30 road dust (RD) samples were collected in Kashi, Cele, and Yutian in the spring, 2018, and RD_2.5 was collected using the resuspension approach. Eight water-soluble ions, 39 trace elements and 8 fractions of carbon-containing species in PM_2.5 were analyzed. Ca²⁺ and Ca were the most abundant ions and elements in RD_2.5 (7.1% and 9.5%). Cl^- in RD_2.5 was affected not only by attributed to saline-alkali soils in oasis cities of the Tarim Basin and dust from Taklimakan Desert but also by human activities. Moreover, the organic carbon/elemental carbon (OC/EC) ratio indicated that carbon components in RD_2.5 in Cele town mainly come from fossil fuel combustion, while those in Yutian and Kashi mainly come from biomass combustion. It is noteworthy that high Ca in RD_2.5 was seriously affected by anthropogenic emissions, and high Na and K contents in RD_2.5 could be derived from soil and desert dust. It was estimated that Cd, Tl, Sn and Cr were emitted from anthropogenic emissions using the enrichment factor. The coefficients of divergence (COD) result indicated that the influence of local emission on road dust emission is greater than that of long-distance transmission. This study is the first time to comprehensively analyze the chemical characteristics of road dust in oasis cities, and the results provides the sources of road dust at the margin of Tarim Basin.     

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.     

Particulate matter exchange between atmosphere and roads surfaces in urban areas

The deposition and the re-suspension of particulate matter (PM) in urban areas are the key processes that contribute not only to stormwater pollution, but also to air pollution. However, investigation of the deposition and the re-suspension of PM is challenging because of the difficulties in distinguishing between the resuspended and the deposited PM. This study created two Bayesian Networks (BN) models to explore the deposition and the re-suspension of PM as well as the important influential factors. The outcomes of BN modelling revealed that deposition and re-suspension of PM10 occurred under both, high-traffic and low-traffic conditions, and the re-suspension of PM2.5 occurred under low-traffic conditions. The deposition of PM10 under low-volume traffic condition is 1.6 times higher than under high-volume traffic condition, which is attributed to the decrease in PM10 caused by relatively higher turbulence under high-volume traffic conditions. PM10 is more easily resuspended from road surfaces compared to PM2.5 as the particles which larger than the thickness of the laminar airflow over the road surface are more easily removed from road surfaces. The increase in wind speed contributes to the increase in PM build-up by transporting particulates from roadside areas to the road surfaces and the airborne PM2.5 and PM10 increases with the increase in relative humidity. The study outcomes provide a step improvement in the understanding of the transfer processes of PM2.5 and PM10 between atmosphere and urban road surfaces, which in turn will contribute to the effective design of mitigation measures for urban stormwater and air pollution.     

某垃圾焚烧厂投产前后周边土壤二英类化合物的分布

为研究垃圾焚烧厂运行对周边土壤二英类化合物（PCDD/Fs）含量的影响,采集了珠三角地区某垃圾焚烧厂投产前和投产后周边土壤样品,分析研究了该垃圾焚烧厂运行对周边土壤中PCDD/Fs含量和组分的变化.结果表明:①2012年（投产前）珠三角地区某垃圾焚烧厂周边土壤PCDD/Fs含量较低,范围为163~591 ng/kg（毒性当量范围为0.198~0.863 ng I-TEQ/kg,I-TEQ为国际毒性当量因子折算的毒性当量值）;2017—2019年（投产后）周边土壤PCDD/Fs含量范围为151~1.75×103 ng/kg（毒性当量范围为0.812~3.88 ng I-TEQ/kg）,与其他研究相比处于较低的水平.②投产后,距该垃圾焚烧厂较近（1.5 km）的采样点（S1）土壤PCDD/Fs含量逐年增长,在较远（5.2 km）但人口较密集的采样点（S3）土壤PCDD/Fs含量整体较高,但呈逐年下降趋势.③投产后,土壤中的17种PCDD/Fs单体组分中,毒性当量贡献率最高的单体为八氯二苯并二英（OCDD）和2,3,4,7,8-五氯二苯并呋喃（2,3,4,7,8-PeCDF）,二者毒性当量贡献率范围为15.7%~45.4%.④在同一采样点土壤PCDD/Fs单体组分年间差异不明显,但同一年份不同采样点差异明显.研究显示,目前该垃圾焚烧厂周边土壤PCDD/Fs含量较低,但仍需要长期监测其可能带来的风险.      

基于底栖动物的松花江流域不同地形分区水质指标阈值研究

为全面了解松花江流域不同地形分区内底栖动物群落对水质指标的响应规律,识别不同分区水质指标指示物种的差异,于2016—2018年对松花江流域97个采样点的水质指标〔EC、ρ（DO）、ρ（COD_Mn）、ρ（NH₃-N）、ρ（TN）、ρ（TP）〕和大型底栖动物群落进行调查分析,采用临界指示物种分析法（threshold indicator taxa analysis,TITAN）分别探讨松花江流域山区、丘陵区和平原区水质指标的生态阈值,当污染物浓度超过负响应阈值时敏感种密度降低,当超过正响应阈值时耐受种也会受到明显影响,底栖动物群落结构会发生显著变化.将TITAN法所得的负响应阈值作为触发底栖动物群落发生变化的最低值,正响应阈值为底栖动物群落的耐受极限值.结果表明:①松花江流域水质指标在不同地形分区内的阈值不同,除ρ（DO）和ρ（COD_Mn）外,其他指标负响应阈值均表现为山区 < 丘陵区 < 平原区,ρ（DO）则表现相反,ρ（COD_Mn）在丘陵区出现最高阈值（5.46 mg/L）、山区出现最低阈值（4.01 mg/L）.除ρ（DO）以外,其他指标的正响应阈值均呈山区 < 丘陵区 < 平原区的趋势,ρ（DO）正响应阈值的变化趋势则与之相反.②松花江流域内超过50%的采样点水质指标值均超过其负响应阈值,超出正响应阈值的采样点比例在6%~40%之间,说明流域受到一定的干扰,但干扰程度不严重.③同一物种在不同地形分区内对水体理化指标的指示方向可能相反.萝卜螺属在丘陵区为ρ（NH₃-N）的正响应指示物种,在平原区则转变为负响应指示物种;短沟蜷属在丘陵区为ρ（TN）和ρ（TP）的正响应物种,在平原区则转变为负响应物种.研究显示,大型底栖动物群落结构的分布特征是影响水质指标阈值指示物种识别的主要原因,而不同分区的自然地理状况、栖境状况和水质状况则是造成大型底栖动物群落结构分布差异的主要因素.      

达里诺尔湖水体DOM荧光特征及其来源解析

达里诺尔湖（简称“达里湖”）是内蒙古自治区高原地区重要的生态屏障,探究达里湖水质状况及污染来源,对加强流域水环境治理、改善水环境质量具有十分重要的意义.于2018年9月及2019年6月对湖水进行采样,并通过三维荧光光谱结合PARAFAC（平行因子分析）模型,探究达里湖水体DOM（溶解性有机质）来源及其与水质的关系.结果表明:①达里湖水体中pH较高,ρ（DOC）（DOC为溶解性有机碳）、ρ（NH₄+-N）、ρ（TP）相对较高,均超过GB 3838—2002《地表水环境质量标准》Ⅴ类水质标准限值.②水体中DOM含4种荧光组分.夏季水体DOM主要分布于河流入湖口附近,其中,类腐殖质荧光组分（紫外区类富里酸和可见区类富里酸）占总组分的62.93%,类蛋白类荧光组分（类色氨酸和类酪氨酸）占总组分的36.07%;秋季水体DOM主要分布于东南侧,其中,类腐殖质荧光组分占总组分的40.52%,类蛋白类荧光组分占总组分的59.48%.③达里湖采样点荧光参数表明,达里湖DOM自生源特征较强,腐殖化程度较低.类腐殖质荧光组分与ρ（DOC）、ρ（Chla）均呈正相关,类色氨酸荧光组分与pH呈正相关,类络氨酸与ρ（DTN）、ρ（NH4+-N）、ρ（DTP）均呈正相关.研究显示,达里湖DOM具有陆源与生物源双重特性,DOM的形成与微生物、细菌、浮游生物的生命活动密切相关.      

厦门市冬季PM2.5污染情境识别及其与气象条件的关系

为研究厦门市冬季不同PM_2.5污染情境与气象条件和气团轨迹路径特征的关系,结合PM_2.5观测数据,使用AGAGE（Advanced Global Atmospheric Gases Experiment）统计方法识别2014—2018年冬季厦门市PM_2.5观测值、基线值和污染值情境,通过气象数据统计和气团后向轨迹聚类对不同PM_2.5污染情境下气象条件和气团轨迹路径特征进行探究.结果表明:①厦门市冬季不同PM_2.5污染情境下,ρ（PM_2.5）及PM_2.5污染值情境时长占比均呈波动中下降的趋势,具体表现为冬季PM_2.5观测值、污染值和基线值情境下,ρ（PM_2.5）平均值分别从2014年的42.2、90.7、16.4 μg/m3降至2018年的26.3、56.9、8.8 μg/m3,冬季PM_2.5污染值情境时长占比从2014年的10.2%降至2018年的3.0%.②冬季PM_2.5污染值情境下气象要素呈低风速、低气压、高温度、高相对湿度的特征.③冬季到达厦门市的气团轨迹路径中,局地路径由于大气条件稳定易累积形成PM_2.5污染;偏北路径和西北路径易从临近省份携带污染物输入导致PM_2.5污染,属于重要的外源污染输入路径;沿海路径和偏西路径均属于清洁路径,但沿海路径易在福建省北部与偏北路径重合形成污染输入,加强了偏北路径的污染物输送能力.研究显示,近年来厦门市冬季PM_2.5污染有明显减弱趋势,但不利的气象条件和外来污染输入仍会造成PM_2.5污染的发生.      

加入SOA示踪的深圳大气PM2.5受体模型源解析

为厘清包括二次有机气溶胶（SOA）在内的深圳市区PM_2.5各种一次和二次来源贡献,本文于2017年9月2日~2018年8月29日在深圳市大学城点位开展PM_2.5样品采集,并进行化学组分和水溶性有机物（WSOM）质谱测量,共获得162组有效数据.观测期间深圳市大气PM_2.5平均质量浓度为26μg/m³,在传统PMF源解析的基础上加入羧基离子碎片（CO₂⁺）作为SOA的示踪物,加入水溶性有机氧（WSOO）用于计算各因子O/C,验证有机物解析效果.结果表明,SOA可以被独立解析出,其O/C明显高于其他一次污染源中有机物;机动车、二次硫酸盐、二次硝酸盐、SOA为最主要的4个源,对PM_2.5质量浓度的贡献分别为25%、23%、17%和10%,船舶、地面扬尘、老化海盐、建筑尘、生物质燃烧、燃煤和工业贡献均在5%以内.各个源的变化特征表明,机动车、二次硫酸盐、二次硝酸盐、SOA等源贡献呈现冬高夏低的季节特征,与冬季季风条件下源自内陆的污染传输密切相关.污染天气时,二次硝酸盐和SOA的贡献增加相对最显著,因此NOx和挥发性有机物是减排的关键.     

基于PCA-SOM的北京市平谷区地下水污染溯源

为了解北京市平谷区地下水污染物来源,以平谷区2010—2018年监测数据为基础,使用PCA(主成分分析法)识别了地下水水质指标因子,使用自组织映射识别了污染物的空间分布.结果表明:通过监测指标间的Pearson检验发现, 平谷区地下水电导率与ρ(Ca2+)(p=0.936)、总碱度与ρ(HCO₃2-)(p=0.981)、ρ(Mg2+)与总硬度(p=0.944)指标之间显著相关.地下水化学类型主要以HCO₃-Ca型为主,其次为HCO₃-Mg型.NH₄+、SO₄2-、Cd、Fe(Ⅱ)、NO₂指标空间分布离散性和差异性较大,存在局部富集现象.通过因子分析法筛选出影响平谷区地下水水质的8个公因子,首要影响因子为溶滤-富集作用(贡献率为22.398%),次要影响因子为农业、养殖业和填埋场等人为活动作用(贡献率为16.533%),雨水下渗作用(贡献率为8.035%)、工业源人为活动(贡献率为7.466%)对地下水也有一定影响.通过比较各指标的SOM(Self-Organizing Map,自组织映射)特征图像和监测井映射特征图像,发现NH₄+受山前地带林业、种植业和平原地带农业、养殖业的双重影响,Na+、Mn受平原地带人为活动的影响;同时,NH₄+、NO₃-、NO₂三者之间及Fe(Ⅱ)与Fe(Ⅲ)之间来源不同,Cd、Al、氰化物三者具有同一来源.研究显示,PCA-SOM(PCA与SOM相结合)可以对地下水化学组分来源进行定性识别与定量分析.      

能源富集区市域经济发展水平空间格局演变——基于晋陕蒙甘宁地区

采用熵权TOPSIS法对我国晋陕蒙甘宁这一典型能源富集区各地级以上城市的市域经济发展水平进行综合评价,进而使用马尔可夫转移概率分析方法和ESDA空间分析方法,探索该地区市域经济发展水平时空分异格局的演化特征,结果显示：（1）该地区的市域经济发展差距在波动中下降;（2）各等级城市在不同时期演化规律截然相反,随时间推移,除低等级之外的各等级城市均表现出较高的等级下降风险;（3）该地区城市的市域经济水平曾存在一定空间负相关,到2015年这种关系则不再显著;（4）该地区呈现以局部为核心区的格局,但西部地区明显趋冷;（5）市域经济系统整体处于耦合协调度较低的状态,发展不平衡、不协调的问题较突出。