基于绿色制造技术的烤鸭品质特性与安全性研究

本实验比较了传统加工技术与绿色制造技术在烤鸭加工过程中的PM2.5排放量、产品表皮含有的有害物质3,4-苯并芘、12 种杂环胺的含量以及对产品感官品质的影响。结果表明：采用绿色制造技术加工烤鸭时PM2.5的平均排放质量浓度小于200 μg/m3;生产的烤鸭色泽红润鲜亮,经高温灭菌后仍然保持较好的质构,3,4-苯并芘残留量与12 种杂环胺残留总量低于1 μg/kg;传统的烤鸭加工技术PM2.5平均排放质量浓度超过2 000 μg/m3,产品中3,4-苯并芘残留量最高检出量4.25 μg/kg,12 种杂环胺残留总量最高检出量49.95 μg/kg。     

油炸条件对鱼肉中杂环胺与反式脂肪酸形成的影响

研究油炸对草鱼中杂环胺和反式脂肪酸形成的影响,探讨不同油炸温度、油炸时间处理的草鱼中杂环胺生成量和反式脂肪酸的变化规律。结果表明,油炸显著影响杂环胺的种类和含量,鱼肉在150℃油炸,检出Norharman和Harman 2种杂环胺,总量为0.23 ng/g;在210℃时检出4种,总量为9.85 ng/g。210℃油炸20 min的样品中检出6种杂环胺,杂环胺总量达27.09 ng/g。不同油炸时间处理时,油炸20 min的鱼肉样品中反式脂肪酸含量显著增加(p0.05),达0.23 mg/g;并有新的反式脂肪酸tt C18︰2检出。吓在150℃~210℃范围内,油炸温度对草鱼中反式脂肪酸含量的影响不显著。鱼肉样品中反式脂肪酸的种类与油炸用油一致。     

不同产地芝麻所制芝麻油中杂环胺的分析测定

芝麻油可能含有杂环胺9H-吡啶并[3,4-b]吲哚(norharman)和1-甲基-9H-吡啶并[3,4-b]吲哚(harman),为了有效检测芝麻油中杂环胺含量,建立了一种高效液相色谱-荧光检测法(HPLC-FLD),并对不同产地芝麻所制芝麻油中杂环胺含量进行对比。结果表明：所建立的HPLC-FLD能在15 min内实现对芝麻油中杂环胺的测定;在相同炒籽条件下,不同产地芝麻所制芝麻油中杂环胺含量有显著差异(p<0.05),非洲产地的芝麻所制的芝麻油中杂环胺含量(421.87μg/kg)相对高于亚洲产地的(329.32μg/kg),埃塞俄比亚产地的芝麻所制芝麻油中杂环胺含量最高,为720.81μg/kg,而苏丹和中国河南驻马店产地的芝麻所制芝麻油中杂环胺含量较低,分别为236.01μg/kg和239.63μg/kg。综上,芝麻油中杂环胺含量与芝麻原料的选择有关,选择合适的芝麻原料对减控芝麻油中杂环胺、保障芝麻油食用安全具有重要意义。     

远离家常致癌物

正苯并芘含量最高的就是熏烤食品,比如街边销售的碳烤羊肉串、熏鱼、熏肉之类;日常炒菜、油炸、烤肉、烤鱼的时候,也多少会产生一点苯并芘。特别是焦煳的鱼肉类食品,苯并芘含量会相当可观,同时还有杂环胺、丙烯酰胺等其他致癌物、疑似致癌物"济济一堂"。因为这些食物很多人都特别爱吃,对苯并芘等多环芳烃类致癌物也就比较乐于接受,让苯并芘显得比较"家常"和"亲切",尽管它的毒性比三聚氰胺不知大多少倍。不过,日常生活中,烹调加热在所难免,大部分人也不肯放弃油炸食物,该怎么做才能最大程度地减少苯并芘致癌物的危害?1.食用油炸、熏烤食物限量限频     

高效液相色谱-质谱串联法检测中餐常见肉类中杂环胺含量

本文通过优化液液萃取和固相萃取,结合高效液相色谱-质谱串联法对肉制品中的杂环胺进行分析测定。该方法对肉制品中六种杂环胺的检出限和定量限分别低至0.0006 ng/g和0.0021 ng/g。应用该方法研究了常见烹饪方式(烘烤和油炸)对大众餐桌上最常见肉品(鸡肉、猪肉、牛肉、草鱼)中杂环胺形成的影响。结果表明,相同烹饪方式处理的肉制品中杂环胺的生成量随烹饪温度的升高而增加;在相近加工温度下,油炸烹制的肉和鱼会产生较烘烤处理更多的杂环胺。烘烤和油炸烹制的肉制品中含量最高的杂环胺分别是2-氨基-1-甲基-6-苯基咪唑并[4,5-b]吡啶(Ph IP)和2-氨基-3,8-二甲基咪唑并[4,5-f]喹喔啉(Me IQx)。相同烘烤烹制条件下(275℃),烤鸡肉中产生的杂环胺总含量最高,其次是烤猪肉,草鱼和牛肉。275℃下烘烤烹制的鸡肉中检出最高含量的Ph IP(341.15ng/g)。在相同的实验用油炸烹制条件下,油炸肉类和鱼类中杂环胺含量处于相对较低的水平,相互之间略有差异;于200℃的油炸牛肉中检测出最高含量Me IQx (7.44 ng/g)。     

不同加工工序对鸡腿品质特性及杂环胺形成的影响

为探究不同加工工序对鸡腿品质及杂环胺形成的影响,文章选取酱卤肉制品的3种工序(卤煮、油炸-卤煮、卤煮-油炸)加工鸡腿,测定鸡腿中蛋白质、水分、肌酸、肌酸酐、杂环胺的含量及蒸煮损失率、色泽的变化,研究不同工序下酱卤鸡腿品质与杂环胺形成的相关性。结果表明:卤煮-油炸工艺中鸡腿的蒸煮损失率、色差值和肌酸酐含量最高,水分含量最低,生成杂环胺的总量最高,鸡腿表皮中达到7.969 ng/g,鸡腿肉中达到4.701 ng/g;由相关性分析得到,鸡腿皮和鸡腿肉中杂环胺都与肌酸含量呈显著负相关性,与肌酸酐含量呈显著正相关性;3种加工工序下鸡腿表皮中杂环胺含量与ΔΕ呈显著正相关(P0.05),而鸡腿肉中杂环胺含量与水分含量呈显著负相关(P0.05)。因此,建议制作酱卤鸡肉制品以卤煮工艺为主,从而降低产品的损失率;另外,减少使用油炸工序,降低杂环胺生成量。     

联用凝胶色谱净化和超高效液相色谱定量分析植物油中的苯并芘

本研究建立了一种植物油中苯并芘含量的检测方法。植物油通过凝胶色谱净化,采用超高效液相色谱进行检测。结果表明苯并芘标准曲线在0. 50～40. 0 ng/m L范围内具有良好的线形关系,相关系数R2=0. 999 93。苯并芘的方法检出限(S/N=3)为0. 018 g/kg,定量限(S/N=10)为0. 060μg/kg。3个加标浓度下的回收率范围88%～92%,3个浓度水平检测结果的相对标准偏差小于10%。本方法具有操作简便,快速等特点,符合分析要求。     

GC-MS/SIM法测定芝麻香型白酒中3-甲硫基丙醇

建立了利用气相色谱-质谱/选择离子扫描法(GC-MS/SIM)检测芝麻香白酒特征成分3-甲硫基丙醇的方法。样品前处理方法:CH2Cl2萃取、酒样浓缩5倍分析;色谱方法:DB-FFAP(60 m×0.25 mm×0.25μm)毛细管柱,程序升温;SIM方法检测质荷比106和61的离子;采用外标法定量。结果表明:在3-甲硫基丙醇质量浓度为50μg/L~10 mg/L范围,线性回归方程:y=491995x+3561.7,线性相关系数为0.9991;检测限5μg/L,定量限10μg/L。在3-甲硫基丙醇质量浓度为80μg/L,800μg/L和8 mg/L 3个水平下,回收率在83.8%~114.1%之间,日内、日间精密度均小于5%。对5个品牌共21个酒样的3-甲硫基丙醇的检测结果显示:品牌1原酒及商品酒中均未检出3-甲硫基丙醇;品牌2原酒中未检出3-甲硫基丙醇;商品酒S-2-1、S-2-2、S-2-3和S-2-4中3-甲硫基丙醇含量分别为1.4,0.36,1.0,0.66 mg/L;品牌3原酒及商品酒中均未检出3-甲硫基丙醇;品牌4商品酒中未检出3-甲硫基丙醇,原酒中其含量为2.4μg/L;品牌5原酒中未检出3-甲硫基丙醇,商品酒S-5中3-甲硫基丙醇含量为0.24 mg/L。     

烟熏液对卤煮牛肉中9 种杂环胺含量的影响

本实验研究了烟熏液对卤煮牛肉中9 种杂环胺含量的影响。结果显示：鲜牛肉只检测出PHIP、MeIQx 2 种杂环胺,含量只有0.16 ng/g,随着卤煮时间延长,检出杂环胺种类和含量均显著增加（P＜0.05）,卤煮4 h后,9 种杂环胺含量达到21.18 ng/g;添加烟熏液可以显著抑制卤煮牛肉中杂环胺的形成（P＜0.05）,0.05 mg/mL烟熏液可以将卤煮牛肉中杂环胺含量从92.72 ng/g降低到7.35 ng/g,效果显著（P＜0.05）,但是随着烟熏液浓度的增加,对各杂环胺形成的影响不一;烟熏液对卤煮牛肉杂环胺形成的抑制作用可能与其抗氧化性有关。     

加工条件对油条中丙烯酰胺含量的影响

油条在油炸温度160～200℃、油炸时间3～5min时,油条可取得最佳感官特征,同时也是丙烯酰胺产生最多的时段。以菜籽油、大豆油、花生油、玉米油作油炸用油,硫酸铝钾作膨松剂,油条中丙烯酰胺的最高含量不超过150μg/kg;而用棕榈油时,丙烯酰胺的最高含量约为250μg/kg。用0.3%的酵母粉作发酵剂,用棕榈油、花生油炸制的油条中丙烯酰胺最高含量分别达到1589.41和953.60μg/kg,是用硫酸铝钾作膨松剂的油条中丙烯酰胺含量的6.29倍和8.13倍。用泡打粉作膨松剂制得的油条,丙烯酰胺含量明显下降,平均约为50μg/kg。以果葡糖浆作甜味剂的油条中丙烯酰胺含量较蔗糖作甜味剂的油条平均增加约10%。因此,油炸温度160～200℃、油炸时间3～5min,以棕榈油作油炸用油,酵母作发酵剂,果葡糖浆作甜味剂可大大增加油炸面制品中丙烯酰胺含量。     

Household concentrations and exposure of children to particulate matter from biomass fuels in The Gambia

Particulate matter (PM) is an important metric for studying the health effects of household air pollution. There are limited data on PM exposure for children in homes that use biomass fuels, and no previous study has used direct measurement of personal exposure in children younger than 5 years of age. We estimated PM(2.5) exposure for 1266 children in The Gambia by applying the cookhouse PM(2.5)-CO relationship to the child's CO exposure. Using this indirect method, mean PM(2.5) exposure for all subjects was 135 ± 38 μg/m(3); 25% of children had exposures of 151 μg/m(3) or higher. Indirectly estimated exposure was highest among children who lived in homes that used firewood (collected or purchased) as their main fuel (144 μg/m(3)) compared to those who used charcoal (85 μg/m(3)). To validate the indirect method, we also directly measured PM(2.5) exposure on 31 children. Mean exposure for this validation data set was 65 ± 41 μg/m(3) using actual measurement and 125 ± 54 μg/m(3) using the indirect method based on simultaneously-measured CO exposure. The correlation coefficient between direct measurements and indirect estimates was 0.01. Children in The Gambia have relatively high PM(2.5) exposure. There is a need for simple methods that can directly measure PM(2.5) exposure in field studies.     

Optical remote sensing to quantify fugitive particulate mass emissions from stationary short-term and mobile continuous sources: part II. Field applications

Quantification of emissions of fugitive particulate matter (PM) into the atmosphere from military training operations is of interest by the United States Department of Defense. A new range-resolved optical remote sensing (ORS) method was developed to quantify fugitive PM emissions from puff sources (i.e., artillery back blasts), ground-level mobile sources (i.e., movement of tracked vehicles), and elevated mobile sources (i.e., airborne helicopters) in desert areas that are prone to generating fugitive dust plumes. Real-time, in situ mass concentration profiles for PM mass with particle diameters <10 μm (PM(10)) and <2.5 μm (PM(2.5)) were obtained across the dust plumes that were generated by these activities with this new method. Back blasts caused during artillery firing were characterized as a stationary short-term puff source whose plumes typically dispersed to <10 m above the ground with durations of 10-30 s. Fugitive PM emissions caused by artillery back blasts were related to the zone charge and ranged from 51 to 463 g PM/firing for PM(10) and 9 to 176 g PM/firing for PM(2.5). Movement of tracked vehicles and flying helicopters was characterized as mobile continuous sources whose plumes typically dispersed 30-50 m above the ground with durations of 100-200 s. Fugitive PM emissions caused by moving tracked vehicles ranged from 8.3 to 72.5 kg PM/km for PM(10) and 1.1 to 17.2 kg PM/km for PM(2.5), and there was no obvious correlation between PM emission and vehicle speed. The emission factor for the helicopter flying at 3 m above the ground ranged from 14.5 to 114.1 kg PM/km for PM(10) and 5.0 to 39.5 kg PM/km for PM(2.5), depending on the velocity of the helicopter and type of soil it flies over. Fugitive PM emissions by an airborne helicopter were correlated with helicopter speed for a particular soil type. The results from this range-resolved ORS method were also compared with the data obtained with another path-integrated ORS method and a Flux Tower method.     

Source contributions to atmospheric gases and particulate matter in the southeastern United States

A new approach for determining the contributions of emission sources to concentrations of particulate matter and gases is developed using the chemical mass balance (CMB) method and the U.S. EPA's National Emission Inventory (NEI). The approach apportions combined gas-phase and condensed-phase concentrations of individual compounds as well as PM(2.5) mass. Because the NEI is used to provide source emission profiles for CMB analysis, the method generates information on the consistency of the NEI with ambient monitoring data. The method also tracks secondary species to primary source emissions, permitting a more complete accounting of the impact of aggregated source types on PM(2.5) mass concentrations. An example application is presented using four years of monitoring data collected at eight sites in the Southeastern Aerosol Research and Characterization (SEARCH) network. Including both primary and secondary species, area sources contributed 2.0-3.7 μg m(-3) (13-26%), point sources contributed 3.0-4.6 μg m(-3) (22-33%), and mobile sources contributed 1.0-6.0 μg m(-3) (9-42%) to mean PM(2.5) mass concentrations. Whereas the NEI generally accounts for the ambient concentrations of gases and particles, certain anomalies are identified, especially related to carbonaceous compounds and dust.     

Exposure assessment for estimation of the global burden of disease attributable to outdoor air pollution

Ambient air pollution is associated with numerous adverse health impacts. Previous assessments of global attributable disease burden have been limited to urban areas or by coarse spatial resolution of concentration estimates. Recent developments in remote sensing, global chemical-transport models, and improvements in coverage of surface measurements facilitate virtually complete spatially resolved global air pollutant concentration estimates. We combined these data to generate global estimates of long-term average ambient concentrations of fine particles (PM(2.5)) and ozone at 0.1° × 0.1° spatial resolution for 1990 and 2005. In 2005, 89% of the world's population lived in areas where the World Health Organization Air Quality Guideline of 10 μg/m(3) PM(2.5) (annual average) was exceeded. Globally, 32% of the population lived in areas exceeding the WHO Level 1 Interim Target of 35 μg/m(3), driven by high proportions in East (76%) and South (26%) Asia. The highest seasonal ozone levels were found in North and Latin America, Europe, South and East Asia, and parts of Africa. Between 1990 and 2005 a 6% increase in global population-weighted PM(2.5) and a 1% decrease in global population-weighted ozone concentrations was apparent, highlighted by increased concentrations in East, South, and Southeast Asia and decreases in North America and Europe. Combined with spatially resolved population distributions, these estimates expand the evaluation of the global health burden associated with outdoor air pollution.     

甘草黄酮对大气细颗粒物PM2.5引起肺泡巨噬细胞损伤的保护作用

目的:研究甘草黄酮对大气细颗粒物PM2.5(SRM 2786)导致的大鼠肺泡巨噬细胞(NR8383)损伤的保护作用。方法:实验分为对照组、模型组(125 μg/mL SRM 2786)与不同浓度甘草黄酮给药组(3.125、6.25、12.5、25 μg/mL+125 μg/mL SRM 2786),药物作用24 h后分别用MTT法检测细胞存活率、细胞形态观察、酶联免疫法(Elisa)检测细胞上清液肿瘤坏死因子α(TNF-α)、白介素6(IL-6)及白介素1β(IL-1β)的含量、各组细胞NO和ROS释放及细胞中SOD活性和GSH-PX含量。结果:相较于对照组,125 μg/mL SRM 2786诱导可减少细胞贴璧生长且显著降低细胞存活率、SOD活性和GSH-PX含量、提高TNF-α、IL-6及IL-1β三种细胞因子的释放及细胞ROS和NO释放(p<0.01);而3.125~25 μg/mL甘草黄酮可使大部分悬浮细胞重新贴璧且显著提高下降的细胞存活率,显著抑制SRM 2786诱导的炎症细胞因子的释放和ROS释放、显著提高SOD活性及GSH-PX含量(p<0.05或 p<0.01),6.25~25 μg/mL甘草黄酮可显著降低SRM 2786导致的NO释放(p<0.05或p<0.01)。结论:甘草黄酮可显著提高由细颗粒物SRM 2786降低的细胞存活率和提高抗氧化酶活性、抑制炎性因子释放及氧化应激,其机制可能与其抗炎性损伤和氧化损伤有关。     

Chemical speciation of vanadium in particulate matter emitted from diesel vehicles and urban atmospheric aerosols

We report on the development and application of an integrated set of analytical tools that enable accurate measurement of total, extractable, and, importantly, the oxidation state of vanadium in sub-milligram masses of environmental aerosols and solids. Through rigorous control of blanks, application of magnetic-sector-ICPMS, and miniaturization of the extraction/separation methods we have substantially improved upon published quantification limits. The study focused on the application of these methods to particulate matter (PM) emissions from diesel vehicles, both in baseline configuration without after-treatment and also equipped with advanced PM and NO(x) emission controls. Particle size-resolved vanadium speciation data were obtained from dynamometer samples containing total vanadium pools of only 0.2-2 ng and provide some of the first measurements of the oxidation state of vanadium in diesel vehicle PM emissions. The emission rates and the measured fraction of V(V) in PM from diesel engines running without exhaust after-treatment were both low (2-3 ng/mile and 13-16%, respectively). The V(IV) species was measured as the dominant vanadium species in diesel PM emissions. A significantly greater fraction of V(V) (76%) was measured in PM from the engine fitted with a prototype vanadium-based selective catalytic reductors (V-SCR) retrofit. The emission rate of V(V) determined for the V-SCR equipped vehicle (103 ng/mile) was 40-fold greater than that from the baseline vehicle. A clear contrast between the PM size-distributions of V(V) and V(IV) emissions was apparent, with the V(V) distribution characterized by a major single mode in the ultrafine (<0.25 μm) size range and the V(IV) size distribution either flat or with a small maxima in the accumulation mode (0.5-2 μm). The V(V) content of the V-SCR PM (6.6 μg/g) was 400-fold greater than that in PM from baseline (0.016 μg/g) vehicles, and among the highest of all environmental samples examined. Synchrotron based V 1s XANES spectroscopy of vanadium-containing fine-particle PM from the V-SCR identified V(2)O(5) as the dominant vanadium species.     

Estimation of size-resolved ambient particle density based on the measurement of aerosol number, mass, and chemical size distributions in the winter in beijing

Simultaneous measurements of aerosol size, distribution of number, mass, and chemical compositions were conducted in the winter of 2007 in Beijing using a Twin Differential Mobility Particle Sizer and a Micro Orifice Uniform Deposit Impactor. Both material density and effective density of ambient particles were estimated to be 1.61 ± 0.13 g cm(-3) and 1.62 ± 0.38 g cm(-3) for PM(1.8) and 1.73 ± 0.14 g cm(-3) and 1.67 ± 0.37 g cm(-3) for PM(10). Effective density decreased in the nighttime, indicating the primary particles emission from coal burning influenced the density of ambient particles. Size-resolved material density and effective density showed that both values increased with diameter from about 1.5 g cm(-3) at the size of 0.1 μm to above 2.0 g cm(-3) in the coarse mode. Material density was significantly higher for particles between 0.56 and 1.8 μm during clean episodes. Dynamic Shape Factors varied within the range of 0.95-1.13 and decreased with particle size, indicating that coagulation and atmospheric aging processes may change the shape of particles.     

Pollutant concentrations within households in Lao PDR and association with housing characteristics and occupants' activities

The paper presents the results of a study conducted to investigate indoor air quality within residential dwellings in Lao PDR. Results from PM(10), CO, and NO(2) measurements inside 167 dwellings in Lao PDR over a five month period (December 2005-April 2006) are discussed as a function of household characteristics and occupant activities. Extremely high PM(10) and NO(2) concentrations (12 h mean PM(10) concentrations 1275 ± 98 μg m(-3) and 1183 ± 99 μg m(-3) in Vientiane and Bolikhamxay provinces, respectively; 12 h mean NO(2) concentrations 1210 ± 94 μg m(-3) and 561 ± 45 μg m(-3) in Vientiane and Bolikhamxay, respectively) were measured within the dwellings. Correlations, ANOVA analysis (univariate and multivariate), and linear regression results suggest a substantial contribution from cooking and smoking. The PM(10) concentrations were significantly higher in houses without a chimney compared to houses in which cooking occurred on a stove with a chimney. However, no significant differences in pollutant concentrations were observed as a function of cooking location. Furthermore, PM(10) and NO(2) concentrations were higher in houses in which smoking occurred, suggestive of a relationship between increased indoor concentrations and smoking (0.05 < p < 0.10). Resuspension of dust from soil floors was another significant source of PM(10) inside the house (634 μg m(-3), p < 0.05).     

Heterocyclic aromatic amines in cooked hamburgers and chicken obtained from local fast food outlets in the Ottawa region

Heterocyclic aromatic amines (HAAs) are formed in protein-rich foods during high temperature cooking such as frying and grilling. Since most HAAs are potent mutagens and almost all are carcinogenic to laboratory animals, their formation in cooked foods is a health concern. In the present study, 31 cooked hamburgers and six chicken preparations were obtained from various fast food outlets in the Ottawa area and analyzed for HAAs. In the developed procedure, ground-up samples were extracted under both acidic and alkaline conditions, cleaned on SPE cartridges, and the concentrations of various HAAs determined using electrospray ionization LC/MS/MS. Deuterium-labelled internal standards of the three most commonly found HAAs (IQ, MeIQx, and PhIP) in such foods were used for quantitation and recovery correction. Varying levels of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) (0.2–6 μg/kg), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) (0.1–3.5 μg/kg), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) (0.3–6.9 μg/kg), and 7,8-dimethyl-IQx (2-amino-3,7,8-trimethylimidazo[4,5-f]quinoxaline) (0.1–2.9 μg/kg) were detected in most hamburgers, whereas our limited data on the chicken samples (wings, drumsticks, and nuggets) indicated the presence of mainly PhIP (0.1–2.1 μg/kg) and MeIQx (0.1–1.8 μg/kg). Traces of 4,7,8-trimethyl-IQx (<0.1 μg/kg), 3-amino-1,4-dimethyl-5H-pyrido[3,4-b]indole (Trp-P-1) (<0.1–0.3 μg/kg), and 3-amino-1-methyl-5H-pyrido[3,4-b]indole (Trp-P-2) (<0.1–0.8 μg/kg) were also detected in some samples of hamburgers but not in any of the chicken analyzed thus far. Since hamburger is a popular meal among Canadians, regular consumption of such items may contribute substantially to one's dietary intake of HAAs.     

Spatiotemporal aspects of real-time PM(2.5): low- and middle-income neighborhoods in Bangalore, India

We measured outdoor fine particulate matter (PM(2.5)) concentrations in a low- and a nearby middle-income neighborhood in Bangalore, India. Each neighborhood included sampling locations near and not near a major road. One-minute average concentrations were recorded for 168 days during September 2008 to May 2009 using a gravimetric-corrected nephelometer. We also measured wind speed and direction, and PM(2.5) concentration as a function of distance from road. Average concentrations are 21-46% higher in the low- than in the middle-income neighborhood, and exhibit differing spatiotemporal patterns. For example, in the middle-income neighborhood, median concentrations are higher near-road than not near-road (56 versus 50 μg m(-3)); in the low-income neighborhood, the reverse holds (68 μg m(-3) near-road, 74 μg m(-3) not near-road), likely because of within-neighborhood residential emissions (e.g., cooking; trash combustion). A moving-average subtraction method used to infer local- versus urban-scale emissions confirms that local emissions are greater in the low-income neighborhood than in the middle-income neighborhood; however, relative contributions from local sources vary by time-of-day. Real-time relative humidity correction factors are important for accurately interpreting real-time nephelometer data.