Characteristics of particulate-bound polycyclic aromatic hydrocarbons emitted from industrial grade biomass boilers

Polycyclic aromatic hydrocarbons(PAHs) are carcinogenic or mutagenic and are important toxic pollutants in the flue gas of boilers. Two industrial grade biomass boilers were selected to investigate the characteristics of particulate-bound PAHs: one biomass boiler retro-fitted from an oil boiler(BB1) and one specially designed(BB2) biomass boiler. One coal-fired boiler was also selected for comparison. By using a dilution tunnel system, particulate samples from boilers were collected and 10 PAH species were analyzed by gas chromatography–mass spectrometry(GC–MS). The total emission factors(EFs) of PAHs ranged from 0.0064 to0.0380 mg/kg, with an average of 0.0225 mg/kg, for the biomass boiler emission samples. The total PAH EFs for the tested coal-fired boiler were 1.8 times lower than the average value of the biomass boilers. The PAH diagnostic ratios for wood pellets and straw pellets were similar.The ratio of indeno(1,2,3-cd)pyrene/[indeno(1,2,3-cd)pyrene + benzo(g,h,i)perylene] for the two biomass boilers was lower than those of the reference data for other burning devices, which can probably be used as an indicator to distinguish the emission of biomass boilers from that of industrial coal-fired boilers and residential stoves. The toxic potential of the emission from wood pellet burning was higher than that from straw pellet burning, however both of them were much lower than residential stove exhausts.     

Soil pollution by polycyclic aromatic hydrocarbons: A comparison of two Chinese cities

Soil samples from Huizhou and Zhanjiang, China were analyzed for 16 priority polycyclic aromatic hydrocarbons (PAHs) with harmonized sampling, sample extraction and analysis quantification methods. The concentrations and sources of PAHs in soil samples of the two cities were compared. Almost all of the PAH components were detectable in 103 soil samples. The concentrations of ΣPAHs ranged from 35.40 to 534.5 g/kg in soil samples from Huizhou, and ranged from 9.50 to 6618.00 g/kg in samples from Zhanjiang. Evident differences of concentrations, compositions and sources of PAHs in soils were observed between the two cities. The average concentrations of individual component and the sum of a group of PAHs in soil samples from Zhanjiang were significantly higher than those in Huizhou (P < 0.05). Phe, Flu, Pyr, Bbf and Baa were the dominant PAH components both in soil samples from Huizhou and Zhanjiang. Except for these five components, Bap, I1p, Daa and Bgp were also the dominant PAH components in soil samples from Zhanjiang. Coal combustion and liquid fossil fuel combustion were the same sources of PAHs in the two cities with different contributions, and petroleum played a key role in PAHs release in Zhanjiang.     

Influence of fuel moisture, charge size, feeding rate and air ventilation conditions on the emissions of PM, OC, EC, parent PAHs, and their derivatives from residential wood combustion

Controlled combustion experiments were conducted to investigate the influence of fuel charge size, moisture, air ventilation and feeding rate on the emission factors (EFs) of carbonaceous particulate matter, parent polycyclic aromatic hydrocarbons (pPAHs) and their derivatives from residential wood combustion in a typical brick cooking stove. Measured EFs were found to be independent of fuel charge size, but increased with increasing fuel moisture. Pollution emissions from the normal burning under an adequate air supply condition were the lowest for most pollutants, while more pollutants were emitted when an oxygen deficient atmosphere was formed in the stove chamber during fast burning. The impacts of these factors on the size distribution of emitted particles was also studied. Modified combustion efficiency and the four investigated factors explained 68%, 72%, and 64% of total variations in EFs of PM, organic carbon, and oxygenated PAHs, respectively, but only 36%, 38% and 42% of the total variations in EFs of elemental carbon, pPAHs and nitro-PAHs, respectively.     

Polycyclic aromatic hydrocarbon concentrations, compositions, sources, and associated carcinogenic risks to humans in farmland soils and riverine sediments from Guiyu, China

The concentrations of 16 priority polycyclic aromatic hydrocarbons(PAHs) were measured in 23 farmland soil samples and 10 riverine sediment samples from Guiyu, China, and the carcinogenic risks associated with PAHs in the samples were evaluated. Guiyu is the largest electronic waste(EW) dismantling area globally, and has been well known for the primitive and crude manner in which EWs are disposed, such as by open burning and roasting. The total PAH concentrations were 56–567 ng/g in the soils and 181–3034 ng/g in the sediments.The Shanglian and Huamei districts were found to be more contaminated with PAHs than the north of Guiyu. The soils were relatively weakly contaminated but the sediments were more contaminated, and sediments in some river sections might cause carcinogenic risks to the groundwater system. The PAHs in the soils were derived from combustion sources,but the PAHs in the sediments were derived from both combustion and petroleum sources.     

Distribution and sources of polycyclic aromatic hydrocarbons in the water column of Kongsfjorden, Arctic

Kongsfjorden is known for its characteristic multi-layer water mass formed by the convergence of freshwaters from nearby glaciers and rivers and saline water from the Atlantic and Arctic. The distribution of polycyclic aromatic hydrocarbons (PAHs) in the water column of Kongsfjorden was investigated and their potential sources were analyzed. The total concentrations of 16 PAHs in the surface seawater and river water were in the range of 33.4?79.8 ng/L (mean 48.5 ng/L) and 2.3?201.4 ng/L (mean 126.1 ng/L), respectively. Horizontally, PAHs were mainly concentrated around river estuaries and the glacier front in the dissolved phase. Vertically, the PAHs in the particulate phase followed surface-enrichment and depth-depletion patterns in most stations, with the maximum concentration found at 50 m depth in the central area of Kongsfjorden. The compositions of PAHs in seawater and rivers were similar, with two-ring and tricyclic PAHs comprising the majority of the dissolved and particulate phases. PAHs found in Kongsfjorden waters appeared to be derived from multiple sources such as petroleum and coal combustion. PAHs in the bay mouth of Kongsfjorden were mainly introduced by the West Spitsbergen Current and the Arctic waters, while in the inner bay, atmospheric deposition and local sources were the major contributors. The distribution of PAHs was mainly attributed to the suspended particulate distribution.     

Investigation of polycyclic aromatic hydrocarbons from coal gasification

The hazardous organic pollutants generated from coal gasification, such as polycyclic aromatic hydrocarbons(PAHs), are highly mutagenic and carcinogenic. More researchers have paid particular attention to them. Using air and steam as gasification medium, the experiments of three kinds of coals were carried out in a bench-scale atmospheric fluidized bed gasifier. The contents of the 16 PAHs specified by US EPA in raw coal, slag, bag house coke, cyclone coke and gas were measured by HPLC to study the contents of PAHs in raw coal and the effects of the inherent characters of coals on the formation and release of PAHs in coal gasification. The experimental results showed that the distributions of PAHs in the gasified products are similar to raw coals and the total-PAHs content in coal gasification is higher than in raw coal(except Coal C). The totaI-PAHs contents increase and then decrease with the rise of fixed carbon and sulfur of coal while there has an opposite variation when volatile matters content increase. The quantities of PAHs reduce with the increase of ash content or the drop of heating value during coal gasification.     

Polycyclic aromatic hydrocarbon in urban soil from Beijing, China

Polycyclic aromatic hydrocarbons （EPA-PAHs） in the urban surface soils from Beijing were determined using gas chromatography and mass spectrometry （GC-MS）. It is significantly complementary for understanding the PAHs pollution in soil of integrated Beijing city on the basis of the information known in the outskirts. The total concentration of 16 EPA-PAH was from 0.467 to 5.470 μg/g and was described by the contour map. Compound profiles presented that the 4-, 5- and 6-ring PAHs were major compositions. The correlation analysis showed that PAHs have the similar source in the most sampling sites and BaP might be considered as the indicator of PAHs. Characteristic ratios of anthracene （An）/（An＋ phenanthrene （Phe））, fluoranthene （Flu）/（Flu/ pyrene （Pyr）） and benzo[a]pyrene （BaP）/laenzo[g,h,i]perylene （BghiP） indicated that the PAHs pollutants probably mainly originated from the coal combustion and it was not negligible from vehicular emission. The level of PAHs in our study area was compared with other studies.     

Mixed uncertainty analysis of polycyclic aromatic hydrocarbon inhalation and risk assessment in ambient air of Beijing

This article presents the application of an integrated method that estimates the dispersion of polycyclic aromatic hydrocarbons (PAHs) in air, and assesses the human health risk associated with PAHs inhalation. An uncertainty analysis method consisting of three components were applied in this study, where the three components include a bootstrapping method for analyzing the whole process associated uncertainty, an inhalation rate (IR) representation for evaluating the total PAH inhalation risk for human health, and a normally distributed absorption fraction (AF) ranging from 0% to 100% to represent the absorption capability of PAHs in human body. Using this method, an integrated process was employed to assess the health risk of the residents in Beijing, China, from inhaling PAHs in the air. The results indicate that the ambient air PAHs in Beijing is an important contributor to human health impairment, although over 68% of residents seem to be safe from daily PAH carcinogenic inhalation. In general, the accumulated daily inhalation amount is relatively higher for male and children at 10 years old of age than for female and children at 6 years old. In 1997, about 1.73% cancer sufferers in Beijing were more or less related to ambient air PAHs inhalation. At 95% confidence interval, approximately 272–309 individual cancer incidences can be attributed to PAHs pollution in the air. The probability of greater than 500 cancer occurrence is 15.3%. While the inhalation of ambient air PAHs was shown to be an important factor responsible for higher cancer occurrence in Beijing, while the contribution might not be the most significant one.     

Emissions of parent, nitrated, and oxygenated polycyclic aromatic hydrocarbons from indoor corn straw burning in normal and controlled combustion conditions

Emission factors （EFs） of parent polycyclic aromatic hydrocarbons （pPAHs）, nitrated PAHs （nPAHs）, and oxygenated PAHs （oPAHs） were measured for indoor corn straw burned in a brick cooking stove under different burning conditions. The EFs of total 28 pPAHs, 6 nPAHs and 4 oPAHs were （7.9 ±3.4）, （6.5 ±1.6）×10^-3, and （6.1 ±1.4）×10^-1mg/kg, respectively. Fuel charge size had insignificant influence on the pollutant emissions. Measured EFs increased significantly in a fast burning due to the oxygen deficient atmosphere formed in the stove chamber. In both restricted and enhanced air supply conditions, the EFs of pPAHs, nPAHs and oPAHs were significantly higher than those measured in normal burning conditions. Though EFs varied among different burning conditions, the composition profiles and calculated isomer ratios were similar, without significant differences. The results from the stepwise regression model showed that fuel burning rate, air supply amount, and modified combustion efficiency were the three most significant influencing factors, explaining 72%-85% of the total variations.     

Characterization and distribution of polycyclic aromatic hydrocarbon in sediments of Haihe River, Tianjin, China

In this study sediment samples were collected from 13 sites of Haihe River in Tianjin City, China, sixteen of priority polycyclic aromatic hydrocarbons （PAHs） listed in USEPA were analyzed by means of GC-MS. The total concentrations of PAH ranged from 774.81 to 255371.91 ng/g dw, and two to four rings of PAHs were dominant in sediment samples. Molecular ratios, such as phenanthrene/anthracene, fluoranthene/pyrene and low-molecular-weight PAH/high-molecular-weight PAH, were used to study the possible sources of pollution. It indicated a mixed pattern of parolytic and petrogenic inputs of PAHs in sediments in Haihe River. The petrogenic PAHs may be mainly derived from the leakage of refined products, e.g., gasoline, diesel fuel and fuel oil vehicle traffics or gas stations from urban area. The pyrolytic PAHs might be from the discharge of industrial wastewater and the emission of atmospheric particles from petrochemical factories. In addition, the levels of PAHs in the urban and industrial areas are far beyond the values reported from other rivers and marine systems reported. This situation may be due to polluted discharging from some petrochemical industrial manufactories and worse traffic conditions in Tianjin.     

国内民用燃煤烟气中多环芳烃排放因子研究

模拟国内民用燃煤过程.确定燃煤排放烟气中PAHs的排放因子、PAHs在烟气气相与颗粒相之间的分配、特征排放谱以及不同燃烧方式的影响.结果表明:以15种母体PAHs加和计,燃煤排放因子的变化范围为71～882 mg·k8-1,排放因子和有毒PAHs组份排放量由高至低依次为烟煤、蜂窝煤和无烟煤,主要毒性成份存在于颗粒相中.PAH组份的气-固相分配比例与其饱和蒸汽压存在显著的正相关关系.燃煤类型和燃煤中挥发组份对烟气PAHs排放因子、气-固相分配以及排放谱分布具有决定性作用.另外,不同燃烧方式对燃煤排放因子也有一定影响,缺氧条件会导致排放系数升高.     

民用燃煤烟气中甲基多环芳烃的排放特征

利用全流稀释烟气采样系统,对20个煤/炉组合方式(涉及4种烟煤和1种无烟煤、块煤和蜂窝煤2种燃烧方式、3种北方地区常用的炉灶类型)的燃烧烟气进行了采样和分析,获取了多环芳烃的排放因子数据.针对具有更强“三致”作用的甲基多环芳烃(A-PAHs)的排放特征进行讨论,并与原煤的有机溶剂抽提物进行对比.结果表明,不同煤种和燃烧方式的8种A-PAHs排放因子(EFA-PAHs)差别显著,其中,烟煤在块煤与蜂窝煤两种燃烧方式下的变化范围分别为0.5~1.6mg/kg和63.9~100.1mg/kg,无烟煤以块煤与蜂窝煤燃烧的EFA-PAHs分别为0.1mg/kg和67.3mg/kg;蜂窝煤的平均EFA-PAHs比块煤高约2个数量级,说明作为洁净煤技术被推广使用的蜂窝煤燃烧方式存在“不洁净”的方面,应引起重视.对比原煤抽提物中A-PAHs的变化特征,可知燃煤烟气中的A-PAHs部分来自于煤的受热挥发,具有原煤的一些特征,但是更多的A-PAHs来自于燃烧过程中的高温裂解反应.     

民用燃煤源中多环芳烃排放因子实测及其影响因素研究

民用燃煤是我国目前关注较多的多环芳烃(polycyclic aromatic hydrocarbons,PAHs)排放源.根据我国民用燃煤所涉及的煤种、燃烧方式和炉灶类型,利用全流稀释采样系统对5种不同成熟度的煤种,分别以散块煤和蜂窝煤形式在3种炉灶类型中燃烧产生的烟气进行了采样和分析,初步获取了我国民用燃煤烟气中PAHs排放因子(EFPAHs)的实测数据.结果表明,烟煤的EFPAHs在块煤燃烧方式下的变化范围为1.1～3.9 mg.kg-1,在蜂窝煤燃烧方式下的变化范围为2.5～21.1 mg.kg-1,无烟煤的EFPAHs在块煤与蜂窝煤燃烧方式下分别为0.2 mg.kg-1与0.6 mg.kg-1.在民用燃煤的EFPAHs的各种影响因素中,煤的地质成熟度起主导作用,不同成熟度煤种的EFPAHs差异幅度高达1～2个数量级.其次是燃烧形态(块煤/蜂窝煤),主要表现为同一种地质成熟度的煤在蜂窝煤燃烧方式下排放的PAHs比块煤高2～6倍.炉灶类型的影响最小.     

燃煤污染源多环芳烃的排放规律及其分布特征

在对固定污染源烟道气中多环芳烃污染物采样和分析方法进行研究的基础上,对几种不同的燃煤锅炉和炉灶烟道气中的多环芳烃进行了分析测定和评价实验,并探讨了各种锅炉和炉灶多环芳烃的排放规律和分布特征.     

洛阳市秋冬季PM2.5中多环芳烃的污染特征、来源解析及健康风险评价

本研究于2018年10月4日至2019年1月30日在洛阳市高新和林校2个采样点位同步连续采集秋冬季PM_2.5样品,使用气相色谱-质谱联用仪（GC-MS）对PM_2.5中优先控制的16种多环芳烃（polycyclic aromatic hydrocarbons,PAHs）进行了分析测定.对优良天和污染天PM_2.5中16种PAHs的质量浓度和组成分布特征进行了研究,利用特征比值法和主成分分析法对其主要来源进行了定性解析,并使用苯并［a］芘（BaP）毒性当量法和增量终生致癌风险模型评估了对人体的健康风险.结果表明在采样期内,高新和林校两个采样点的PM_2.5中16种PAHs质量浓度变化范围分别为24.33~90.26 ng·m^-3和23.81~76.99 ng·m^-3.随着PM_2.5污染程度的加重,PAHs浓度明显升高（污染天为优良天的1.3倍）,不同环数PAHs贡献顺序均为：4环（43%~48%） > 5~6环（32%~35%） > 2~3环（20%~22%）.大气中PAHs主要来自于燃烧源,包括燃煤、生物质燃烧以及机动车排放等,其中燃煤对PAHs污染贡献最大（优良天：49.28%~56.38%,污染天：49.44%~60.60%）.BaP毒性当量浓度表明,污染天存在更高的人体健康风险;增量终生致癌风险结果表明,污染天致癌风险高于优良天,成人呼吸暴露风险高于儿童,在研究区域内不同污染水平下健康风险属于可接受水平（<1×10^-6）.     

民用燃煤不同燃烧阶段细颗粒物排放特征

研究了民用燃煤在不同燃烧阶段排放PM_2.5的质量浓度分布特征.结果表明,散煤与正烧炉在旺火阶段排放颗粒物粒径主要集中在0.2μm以下（d₅₀=0.15μm）,加煤和封火阶段在0.2~0.5μm （d₅₀=0.38mm）,质量占比46.6%~68.97%.型煤与正烧炉在各阶段排放的颗粒物均以0.2μm以下颗粒物为主,质量占比44.64%~56.24%.扫描电镜（SEM）观察到燃煤排放PM_2.5为大量超细颗粒物聚集形成的簇团状结构.用碳平衡法计算得到散煤加煤阶段的PM_2.5排放因子为4.72g/kg,分别是旺火和封火阶段的12和11倍.将散煤更换为型煤,能够使得加煤阶段的PM_2.5排放因子减少90.9%,从而显著降低PM_2.5排放.     

民用燃煤不同燃烧阶段细颗粒物排放特征

研究了民用燃煤在不同燃烧阶段排放PM_2.5的质量浓度分布特征.结果表明,散煤与正烧炉在旺火阶段排放颗粒物粒径主要集中在0.2μm以下（d₅₀=0.15μm）,加煤和封火阶段在0.2~0.5μm （d₅₀=0.38mm）,质量占比46.6%~68.97%.型煤与正烧炉在各阶段排放的颗粒物均以0.2μm以下颗粒物为主,质量占比44.64%~56.24%.扫描电镜（SEM）观察到燃煤排放PM_2.5为大量超细颗粒物聚集形成的簇团状结构.用碳平衡法计算得到散煤加煤阶段的PM_2.5排放因子为4.72g/kg,分别是旺火和封火阶段的12和11倍.将散煤更换为型煤,能够使得加煤阶段的PM_2.5排放因子减少90.9%,从而显著降低PM_2.5排放.     

黄淮平原农田土壤中多环芳烃的分布、风险及来源

对227个黄淮平原农田表层土壤样品中16种多环芳烃(PAHs)含量进行了调查,并对其致癌风险和来源等进行了分析.结果表明,有15种PAHs被普遍检出,各单体检出率在23.3%~100%之间(苊烯未检出).土壤中PAHs总量(∑PAHs15)为33.44~1246μg/kg,平均值为152.4±166.2μg/kg,且以4环及4环以上PAHs为主,其中16.7%的样品中PAHs含量达到了污染水平(>200μg/kg),与国内外其他地区相比,黄淮平原农田土壤中PAHs含量处于相对较低水平.黄淮平原农田土壤7种致癌性PAHs毒性当量浓度(TEQBap)占总毒性当量浓度的98.27%,其中苯并(a)芘(Bap)潜在致癌风险最大.同分异构体比值法和主成分分析结果表明黄淮平原农田土壤中PAHs的主要来源是汽油、柴油高温燃烧、以及煤和秸秆燃烧.相关性分析表明有机质含量与∑PAHs15及PAHs单体含量具有显著相关性,表明有机质是影响PAHs在土壤中含量、空间分布及归趋的一个重要因素.     

民用燃料燃烧碳质组分及VOCs排放特征

选取北京市地区典型生物质燃料（玉米芯、玉米秆、黄豆秆、草梗、松木、栗树枝、桃树枝）以及民用煤（烟煤、蜂窝煤）在实验室内进行了模拟燃烧实验,对燃烧产生的颗粒物及气体样品进行采集,采用Model 2001A热/光碳分析仪对不同粒径段颗粒物中的有机碳、元素碳进行测定,采用AgilentGC-MS 5977/7890B气质联用仪对燃烧烟气中的挥发性有机物进行分析.研究表明：除蜂窝煤OC、EC的排放因子在2.5~10μm粒径范围内达到最大,其他8种固体燃料燃烧产生的OC、EC的排放因子最大值均在0~2.5μm粒径范围内.薪柴（栗树枝、桃树枝、松木）、秸秆（玉米芯、玉米秆、黄豆秆、草梗）和民用煤（蜂窝煤、烟煤）3类物质燃烧排放VOCs的物种分类差异较大.薪柴和民用煤燃烧排放的卤代烃以及含氧有机物的质量分数明显高于秸秆的质量分数;在同一类别中VOCs物质分布趋势一致.3种薪柴平均总VOCs的排放系数为2.02g/kg,4种秸秆平均总VOCs的排放系数为6.89g/kg,2种民用煤平均总VOCs的排放系数为2.03g/kg,秸秆类的排放因子最大.玉米芯、玉米秆、黄豆秆和草梗的臭氧生成潜势较高,而栗树枝、桃树枝、松木、烟煤以及蜂窝煤的臭氧生成潜势较低,且分布类似.烯烃类、烷烃类、芳香烃类是固体燃料燃烧臭氧生成潜势贡献较大的VOCs物质.     

安徽省室内降尘中多环芳烃分布及来源解析

采集安徽省内14个采样点的24个室内降尘样品,检测16种多环芳烃(PAHs)含量.结果表明,安徽省不同区域室内降尘中ΣPAHs浓度范围为0.52~89.3 μg/g,平均浓度为20.7 μg/g.降尘中PAHs以5环为主,其次是4环和3环.PAHs组成分析表明,几乎全部样品中PAHs均以高环(4~6环)为主,其高达60.5%~97.0%,仅在4个样品中检出了较高比例的低环PAHs (2~3环).这说明多数室内降尘中PAHs污染由交通运输(汽车和船舶)以及化工厂等高温燃烧排放造成.而安庆、芜湖及六安地区可能存在较严重的石油污染或煤、木材等低温燃烧源污染.公共场所、城市家庭和农村家庭降尘中PAHs的浓度存在明显的差异,总体上呈现:公共场所>城市家庭>农村家庭.异构体分析表明,公共场所和城市家庭内存在混合来源,而农村家庭以燃烧源为主.致癌能力分析表明,城市家庭降尘中的苯并[a]芘当量(BaPE)值略高于农村家庭.公共场所降尘中的BaPE值远大于家庭场所,是农村家庭或城市家庭场所的2倍多.