重庆市主城区街道灰尘的污染与风险特征研究

【作者】 李章平；

【导师】 魏世强；

【作者基本信息】 西南大学 ， 农业环境保护， 2012， 博士

【摘要】 街道灰尘是城市生态环境的重要细胞之一,其质量好坏与城市水、大气环境质量、生态环境质量以及人群健康质量等具有较大的关联性。重庆市直辖以来,虽已陆续开展了城市街道灰尘的相关研究工作,但由于起步较晚,许多研究内容尚未深入,特别是街道灰尘中持久性有机物和营养物涉及更少。本文采集了重庆市主城区不同行政区、不同功能区40个典型街道的地表灰尘,分析了灰尘的粒径组成、主要污染物质赋存含量、功能区空间格局,评价了街道灰尘污染物的危害程度,初步分辨了街道灰尘主要污染物的来源,表征了街道灰尘污染物环境风险与健康风险,对于维护重庆市主城区生态环境质量,保障人群健康具有重要的理论指导意义,也可为重庆市“创建国家环境保护模范城市”和“五个重庆”建设中的街道灰尘污染的综合防治提供科学依据。首先,通过多重套筛、比重计和激光散射分析仪器相结合的方法,研究了街道灰尘的粒径分布特征,结果表明重庆市主城区街道灰尘的粒径分布呈双峰趋势,第一众数粒径为0～0.01mm(占36.13%),第二众数粒径为0.1～0.25mm(占28.24%),因此灰尘颗粒运动状态多为悬浮搬运,由此带来的大气颗粒悬浮和对人体呼吸系统的危害,应引起足够重视。在0～0.01mm粒径中,各粒级含量服从正态分布,分布频率最高的粒径范围在338.49～6169.90nm,平均为2496.91nm,且平均粒径分布趋势为工业区>交通区>居民区>商贸区>文教区>农业区>旅游区。其次,通过测试0～0.25mm粒径中的萘(NAP)、苊烯(ANY)、苊(ANA)、芴(FLU)、菲(PHE)、蒽(ANT)、荧蒽(FLT)、芘(PYR)、屈(CHR)、苯并[a]蒽(BaA)、苯并[b]荧蒽(BbF)、苯并[k)荧蒽(BkF)、苯并[a]芘(BaP)、茚苯[1,2,3-cd]芘(IPY)、二苯并[a,h]蒽(DBA)、苯并[g,h,i]苝(BPE)等16种PAHs赋存含量,分析街道灰尘PAHs的空间分布特征,分辨街道灰尘PAHs的来源,表征街道灰尘PAHs的环境风险与健康风险,结果表明：(1)重庆市街道灰尘多环芳烃总浓度(∑16PAHs)含量范围为0.443～19.746mg/kg,平均为4.204mg/kg,处于较低水平。变异系数分析结果显示,风险较高的中高环组PAHs来源较为一致,而风险较低的低环组PAHs来源则较为复杂。(2)重庆市街道灰尘16种PAHs中,比例最高的为4环PAHs(61.75%),其次为3环PAHs(14.80%)与6环PAHs(11.52%)；不同采样点之间、不同行政区之间、不同功能区之间的PAHs组份比例并没有显著差异性。(3)采用多项特征化合物比值参数法,根据隶属度优先原则,重庆市街道灰尘的PAHs主要来自于汽车尾气排放和燃煤燃烧。根据特征化合物比值BaA/CHR,白市驿、南山公园、人和、化龙桥、杨公桥、北碚城南新区、重庆发电厂、井口工业园、枇杷山公园等街道灰尘疑为近距离输送,而澄江、花卉园、西南政法大学、观音桥、西南大学、高家花园、石板坡长江大桥、菜园坝、铜元局等街道灰尘可能更多地来自外源输送,其它测点则可能为混合来源。(4)重庆市街道灰尘PAHs的致癌风险比值∑6PAHs/∑16PAHs范围为9.20%～44.43%,处于较低水平,但具有强致癌性的BaP/∑16PAHs最高达到7.71%,显示出一定的致癌风险,其中以观音桥(∑6PAHs)、(?)岂圣花园(∑6PAHs).朝天门(∑6PAHs)、西南大学(BaP)、石板坡长江大桥(BaP)、西南政法大学(BaP)和菜园坝(BaP)等致癌风险更加明显。街道灰尘综合生态毒性较强,主要毒性物为芴(FLU)、荧蒽(FLT)、菲(PHE)等低环组PAHs。(5)重庆市居民人群各年龄段(婴儿、幼儿、少儿、青年、成年)经手-口摄入街道灰尘PAHs的贡献系数分别为98.13%、99.33%、98.24%、97.78%、97.95%,平均为98.25%,占有绝对优势。然后通过测试0-2.0mm以及0～0.25、0.25～05、0.5～1.0、1.0～2.0mmm粒径中砷(As)、镉(Cd)、铬(Cr)、铜(Cu)、汞(Hg)、镍(Ni)、铅(Pb)、锌(Zn)等8种重金属赋存含量,分析街道灰尘重金属的空间分布特征,探讨街道灰尘重金属的粒径效应,表征街道灰尘重金属的环境风险与健康风险,结果表明：(1)重庆市街道灰尘As、Cd、Cr、Cu、Hg、Ni、Pb、Zn的平均含量分别为12.16、0.31、83.93、78.22、0.16、34.65、73.63和144.69mg/kg,均低于全国同类城市平均水平。不同功能区之间,只有Hg的变异系数达到显著差异,各功能区汞含量依次为商贸区>居民区>交通区>文教区>旅游区=工业区>农业区。(2)灰尘粒径越细,重金属分配比例越高,除Cr外,其它各重金属均以0～0.25mmm粒径的质量分配量占绝对优势；0-0.25mm粒级中,分配比例依次为Cd>As>Ni>Pb>Cu>Hg>Zn>Cr。(3)以主城区深层土壤背景值为评价标准,重庆市街道灰尘污染严重顺序依次为商贸区>工业区>居民区>交通区>旅游区>文教区>农业区,重金属顺序为Hg>Cu>Pb>Cd>Zn>As>Cr>Ni；而以展览会土壤标准为评价标准,得到的污染严重顺序依次为工业区>交通区>居民区>商贸区>文教区>农业区>旅游区,重金属顺序为Cu>Zn>Ni>Pb>As>Cr>Cd>Hg,两种标准评价结果呈现较大的差异。(4)各种重金属经呼吸暴露和皮肤暴露的非致癌风险不大,但经手口暴露途径中,Cr、Pb的非致癌风险较高；不同暴露途径的风险顺序为经手口暴露>皮肤暴露>呼吸暴露,不同人群的风险顺序为儿童>成人,重庆市街道灰尘的主要风险途径是经手口暴露,危害的人群主要是儿童。重金属致癌总风险度为6.52×104,而且Cd、Cr、Ni的致癌风险度均在10-6～10-4范围内,显示较低的致癌风险,对人体造成危害的可能性较小。最后,通过测试0-2.0mmm以及0-0.25mmm、0.25～0.5mm、0.5～1.0mm、1.0-2.0mm粒径中的全氮、全磷和有机质等3种营养物赋存含量,分析街道灰尘营养物的空间分布特征,探讨街道灰尘营养物的粒径效应,表征街道灰尘营养物的潜在环境风险,结果表明：(1)重庆市街道灰尘N、P、有机质含量分别为为1.28g/kg、1.69g/kg和46.98g/kg,且均呈现出强烈的空间变异。不同功能区营养物赋存量分布趋势为旅游区>商贸区>居民区>文教区>农业区>交通区>工业区。(2)与重金属赋存量的粒级效应类似,N、P、有机质等营养物质大绝大多数分配在0～0.25mm粒级中,其中又以全氮分配最多；在0～0.25mm粒级中,营养物质分配比例大小顺序为工业区>居民区>商贸区>交通区>文教区>旅游区>农业区,这与前面的重金属粒径分配排序不太一致。(3)N、P、有机质等营养物质的酸雨浸提量均高于纯水浸提量,对于酸雨严重区域之一的重庆市而言,更应关注由灰尘带来的潜在径流污染风险。以浸提率为考察指标,各功能区的径流污染风险依次为农业区>交通区>工业区>文教区>旅游区>商贸区>居民区。论文的特色之处在于系统分析了重庆市主城区街道灰尘中PAHs、重金属、营养物污染的空间分布特征与粒级效应,表征了街道灰尘中PAHs的健康风险特征、重金属的环境风险与健康风险特征以及营养物污染的潜在环境风险特征,并采用以激光散射分析为主的多重手段,研究了重庆市主城区街道灰尘的粒径分布特征。囿于经费等条件的限制,本研究只采集了2011年典型季节的灰尘样品,只分析了0～0.25mm街道灰尘中的PAHs含量,而没有测试各种粒径中的PAHs含量,进而分析街道灰尘中PAHs的粒级效应。因此,在后续的研究中,需要结合现场多季节采样、卫生学调查、模拟实验等综合方法,研究街道灰尘累积量与主要污染物的时间变化规律,推定重庆市主城区街道灰尘的来源辨析,验证街道灰尘对人群的健康风险和对大气、对地表径流的环境风险途径与测度。更多还原

【Abstract】 As the most important cell of urban eco-system and urban environment, the quality of road dust is related with aquatic, atmospheric and ecological environment including human health. Since establishment of municipality, even though some works had been conducted for understanding the fate of road dust, still no further researches were developed, especially, few reports about the persistence organic pollutants (POPs) and nutrients were found. Thus, studying road dust pollution and risk characteristics in Chongqing main districts is helpful for understanding particle compositions, distinguishing pollution sources, characterized road dust environmental and health risks, which can significantly promote urban eco-environmental quality in Chongqing, and provide theory and guide for human health protection.Through sampling road dust from different functional zones and administration areas in main districts respectively, and combining multiple-sieve, gravimeter and laser-scattering technique, the particle sizes distribution characteristics of road dust was studied. The results showed that two-peak trend was observed in dust particle size distributions, first modal number particle was0～0.01mm (36.13%), and second modal number particle was0.1-0.25mm (28.24%), suggesting that the movement of dust particles can attributed to suspended movement, possibly resulted in jeopardy of human respiratory system due to atmospheric suspended particles, which should not be neglected. In range of0～0.01mm, subgroups of particles distribution complied normal distribution form, the highest distribution frequency was observed in338.49-6169.90nm with average value2496.91nm. In addition, the average particle sizes distribution trend was showed as following order:industrial area> transportation area> residential area> commercial area>cultural and education area> agricultural area> tourist area.Sixteen types of PAHs including naphthalene (NAP), acenaphthylene (ANY), acenaphthene (ANA), fluorine(FLU), phenanthrene (PHE), anthracene (ANT), fluoranthene(FLT), pyrene (PYR), chrysene (CHR), benz(a)anthracene(BaA), benzo[b]fluoranthene (BbF), benzo [k] fluoranthene (BkF), benzo [a]pyrene (BaP), indeno (1,2,3-cd)pyrene (IPY), dibenzo (a,h) anthracene (DBA), benzo (g,h,i)perylene (BPE) in0-0.25mm particle size ranges were measured respectively. The results showed that:(1) total PHAs concentration (∑16PAHs) in road dusts sampled from investigated areas ranged from0.443～19.746mg/kg, average concentration was4.204mg/kg, indicating a lower levels. From variation coefficient, the sources of PAHs in middle-high ring groups, which showed higher risk, were similar, but sources of lower ring groups were complex.(2) In16types of PAHs, concentration ratio was highest in four rings PAHs (61.75%), three rings PAHs (14.80%) second and six rings PAHs (11.52%). Among different sampling locations, administration areas, and functional zones, the component ratio of PAHs didn’t show any significantly different.(3) Though method of multiple special compound ratio based on priority principles, PAHs in road dusts mainly came from car tail gas emission and coal combustion.According special compounds ratio BaA/CHR, dusts in Baishiyi, Nanshan park, Renhe, Hualong bridge, Yanggong bridge, Beibei south new district, Chongqing power station, Jinkou industrial park, Piba Shan park possibly attributed to short distance transportation, but all of dusts sampled from Chenjiang, Southwest university of political science and law, Guanyin bridge, Southwest university, Gaojia Garden, Shibanpo Yangtze River Bridge, Caiyuanba, Tongyuanju may be from exogenous transportation. The rest of sampling location may be from mixing sources.(4) Carcinogenic risk ratio of PAHs (∑6PAHs/∑16PAHs) in road dust ranged from9.20%～44.43%, indicating slight lower level. But strong carcinogenic risk ratio (BaP/E16PAHs) showed highest7.71%, suggesting the carcinogenic risk in a certain degree. Of all sampling location, Guanyin bridge (∑6PAHs), Shengkai Garden (E6PAHs), Chaotianmen (∑6PAHs), Southwest university (BaP), Shibanpo Yangtze River Bridge (BaP), Southwest university of political science and law (BaP) and Caiyuanba(BaP) showed the most clearly carcinogenic risk. Mixing eco-toxicity in road dust was relative higher, and the main toxins were fluorine (FLU), fluoranthene (FLT) and phenanthrene (PHE), which all are low ring group of PAHs.(5) The contribution coefficient of road dust PAHs in different age stages of local people (baby, infant, juvenile, youth and adult) through hand-mouth uptake, were98.13%、99.33%、98.24%、97.78%、97.95%respectively, average value was98.25%, indicating a predominant pathway.Different heavy metals including arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb) and zinc (Zn) in0～2.0mm particle size of road dust, which was subgrouped into0～0.25mm,0.25～05mm,0.5～1.0mm and1.0～2.0mm ranges respectively, were analyzed, and heavy metal spatial distribution pattern in road dust was also investigated. Meanwhile particle size effect of heavy metals was discussed, and corresponding potential environmental risk of heavy metals also was characterized. The results showed that:(1) The average concentration of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in road dust were12.16、0.31、83.93、78.22、0.16、34.65、73.63和144.69mg/kg respectively, which were lower than the average concentrations of peer cities in China. Among different functional zones, only variance coefficient of Hg reached significant level, and the Hg contents order implied commercial area> residential area> transportation area> cultural and education area> tourist area> industrial area> agricultural area.(2) Higher heavy metal distribution ratio was observed in fine particle sizes. Except for Cr, the all heavy metals distribution ratio were predominant in0-0.25mm. In0-0.25mm range, distribution ratio implied as Cd>As>Ni>Pb>Cu>Hg>Zn>Cr.(3) Using the deep soil background values in main districts as assessment standard, the road dust pollution level order was commercial area> industrial area> residential area> transportation area> tourist area> cultural and education area> agricultural area, and corresponding heavy metal order was Hg>Cu>Pb>Cd>Zn>As>Cr>Ni. Meanwhile, using exhibition conference soil standard as assessment reference, the corresponding pollution order was industrial area> transportation area> residential area> commercial area> cultural and education area> agricultural area> tourist area, and heavy metal order was Cu>Zn>Ni>Pb>As>Cr>Cd>Hg with evidently difference.(4) non-carcinogenic risk through respiration and skin exposure was not high, but non-carcinogenic risk of Cr and Pb were higher as compared with the others through hand-mouth exposure. Among different exposure pathways, the risk order was hand-mouth>skin>respiration. In addition, in different age stages of people, risk order was child>adult. In Chongqing, the main risk pathway of road dusts was hand-mouth exposure, and the main risk target is children. The total carcinogenic risk level of heavy metal was6.52×10-5, but the carcinogenic risk of Cd, Cr and Ni ranged from10-6～10-4, suggesting a lower carcinogenic risk, and do not resulted in risk for human health.The total nitrogen (TN), total phosphorus (TP), and organic matter concentrations in0～2.0mm particle size of road dust, which was subgrouped into0～0.25mm,0.25～05mm,0.5～1.0mm and1.0～2.0mm ranges respectively, were analyzed, and nutrients spatial distribution pattern in road dust was also investigated. Meanwhile particle size effect of nutrients was discussed, and corresponding potential environmental risk of nutrients also was characterized. The results showed that:(1) N, P and organic matter contents of road dust in Chongqing main districts were1.28g/kg、1.69g/kg and8g/kg respectively with a evidently spatial variance. The content of nutrients in different functional zones complied the following order:tourist area> commercial area> residential area> cultural and educational area>agricultural area> transportation area> industrial area.(2) Similar to particle size effect of heavy metal contents, most of nutrients including N, P and organic matter were distributed in0-0.25mm ranges, of which total N was highest. In particle size less than0.25mm, the nutrient distribution ranked as industrial area>residential area>commercial area> transportation area> cultural and educational area>tourist area>agricultural area, which was a slight different with heavy metals distribution.(3) Acid rain-extract nutrients were all observably higher than water-extract contents, suggesting that potential runoff pollution risk resulted from road dust should need more attention in Chongqing due to its most serious acid rain pollution in Chongqing. Using extraction rate as investigation index, the rank of potential runoff pollution risks in different functional zones were agricultural area>transportation area>industrial area>cultural and education area>tourist area>commercial area>residential area.This paper highlighted the spatial distribution characteristics of PAHs, heavy metals; nutrients in Chongqing Main districts through systemically analysis, and particle size effect, meanwhile healthy risk characteristics of targeted pollutants were all characterized. Additionally, though multiple techniques including laser-scattering, particle sized distribution in Chongqing main districts were also investigated.Due to the limitation of financial support, in this study only dust samples in typical seasons in2011were collected, and PAHs was analyzed in0-0.25mm ranges of road dust, but no PAH was investigated based on various ranges of particle sizes, which would be helpful for understanding the effect of particle sizes on PAHs changes. Thus, in future studies, more experiments, which are based on sampling in different seasons, hygienics investigation, simulating experiments, are needed for understanding time-scale changing patterns of road dust accumulation, and also the source distinguishing is proposed to speculate on road dust in Chongqing main districts, which validates healthy risk of road dust, and corresponding environmental risk pathway of atmosphere and runoff resulted from road dust.更多还原