Using Si depletion in aerosol to identify the sources of crustal dust in two Chinese megacities

Depletion of Si in transported dust has been recognized for many years. It can be used to distinguish between transported and local dust in cities, although it rarely has been. Here we use the variations of the Si/Al ratio in 15 months of continuous PM_2.5 samples at Beijing (northern China) and Chongqing (southwestern China) to reveal the seasonal patterns of their dust sources. For both cities, peaks of concentration for Si and Al in PM_2.5 corresponded with minima of Si/Al, and could often be linked to pulsed air flow from deserts to the northwest. With significant depletion (up to 80%) and homogeneous distribution at urban and rural sites, Si/Al showed a clear seasonal evolution, which decreased from spring to summer, increased from fall to winter, and collapsed during Chinese Spring Festival, indicating the dominance of transported dust, local fugitive dust and firework influence, respectively. The low ratios implied that desert dust is a common source during spring at Chongqing, whereas its presence during cold season at Beijing was also more frequent than expected. Failing to recognize the depletion of Si may lead to an overestimate of desert dust by 15%–65% when using the average abundance of Al in crust (6%–8%), as in previous studies. The difference in Si/Al ratio between local and transported dust implies that >60% of the dust at Beijing came from outside the city during the springs of 2004–2006. This result can help resolve the contradictory findings on this topic that have been presented earlier.     

Influences of natural emission sources (wildfires and Saharan dust) on the urban organic aerosol in Barcelona (Western Mediterranean Basis) during a PM event

The urban air quality in Barcelona in the Western Mediterranean Basin is characterized by overall high particulate matter (PM) concentrations, due to intensive local anthropogenic emissions and specific meteorological conditions. Moreover, on several days, especially in summer, natural PM sources, such as long-range transported Saharan dust from Northern Africa or wildfires on the Iberian Peninsula and around the Mediterranean Basin, may influence the levels and composition of the organic aerosol. In the second half of July 2009, daily collected PM₁₀ filter samples in an urban background site in Barcelona were analyzed on organic tracer compounds representing several emission sources. During this period, an important PM peak event was observed. Individual organic compound concentrations increased two to five times during this event. Although highest increase was observed for the organic tracer of biomass burning, the contribution to the organic aerosol was estimated to be around 6?%. Organic tracers that could be related to Saharan dust showed no correlation with the PM and OC levels, while this was the case for those related to fossil fuel combustion from traffic emissions. Moreover, a change in the meteorological conditions gave way to an overall increase of the urban background contamination. Long-range atmospheric transport of organic compounds from primary emissions sources (i.e., wildfires and Saharan dust) has a relatively moderate impact on the organic aerosol in an urban area where the local emissions are dominating.     

Identification of haze-creating sources from fine particulate matter in Dhaka aerosol using carbon fractions

Fine particulate matter (PM_2.5) samples were simultaneously collected on Teflon and quartz filters between February 2010 and February 2011 at an urban monitoring site (CAMS2) in Dhaka, Bangladesh. The samples were collected using AirMetrics MiniVol samplers. The samples on Teflon filters were analyzed for their elemental composition by PIXE and PESA. Particulate carbon on quartz filters was analyzed using the IMPROVE thermal optical reflectance (TOR) method that divides carbon into four organic carbons (OC), pyrolized organic carbon (OP), and three elemental carbon (EC) fractions. The data were analyzed by positive matrix factorization using the PMF2 program. Initially, only total OC and total EC were included in the analysis and five sources, including road dust, sea salt and Zn, soil dust, motor vehicles, and brick kilns, were obtained. In the second analysis, the eight carbon fractions (OC1, OC2, OC3, OC4, OP, EC1, EC2, EC3) were included in order to ascertain whether additional source information could be extracted from the data. In this case, it is possible to identify more sources than with only total OC and EC. The motor vehicle source was separated into gasoline and diesel emissions and a fugitive Pb source was identified. Brick kilns contribute 7.9 μg/m³ and 6.0 μg/m³ of OC and EC, respectively, to the fine particulate matter based on the two results. From the estimated mass extinction coefficients and the apportioned source contributions, soil dust, brick kiln, diesel, gasoline, and the Pb sources were found to contribute most strongly to visibility degradation, particularly in the winter.

Implications: Fine particle concentrations in Dhaka, Bangladesh, are very high and cause significant degradation of urban visibility. This work shows that using carbon fraction data from the IMPROVE OC/EC protocol provides improved source apportionment. Soil dust, brick kiln, diesel, gasoline, and the Pb sources contribute strongly to haze, particularly in the winter.     

Identification of sources contributing to Mid-Atlantic regional aerosol

Source types or source regions contributing to the concentration of atmospheric fine particles measured at Brigantine National Wildlife Refuge, NJ, were identified using a factor analysis model called Positive Matrix Factorization (PMF). Cluster analysis of backward air trajectories on days of high- and low-factor concentrations was used to link factors to potential source regions. Brigantine is a Class I visibility area with few local sources in the center of the eastern urban corridor and is therefore a good location to study Mid-Atlantic regional aerosol. Sulfate (expressed as ammonium sulfate) was the most abundant species, accounting for 49% of annual average fine mass. Organic compounds (22%; expressed as 1.4 x organic carbon) and ammonium nitrate (10%) were the next abundant species. Some evidence herein suggests that secondary organic aerosol formation is an important contributor to summertime regional aerosol. Nine factors were identified that contributed to PM2.5 mass concentrations: coal combustion factors (66%, summer and winter), sea salt factors (9%, fresh and aged), motor vehicle/mixed combustion (8%), diesel/Zn-Pb (6%), incinerator/industrial (5%), oil combustion (4%), and soil (2%). The aged sea salt concentrations were highest in springtime, when the land breeze-sea breeze cycle is strongest. Comparison of backward air trajectories of high- and low-concentration days suggests that Brigantine is surrounded by sources of oil combustion, motor vehicle/mixed combustion, and waste incinerator/industrial emissions that together account for 17% of PM2.5 mass. The diesel/Zn-Pb factor was associated with sources north and west of Brigantine. Coal combustion factors were associated with coal-fired power plants west and southwest of the site. Particulate carbon was associated not only with oil combustion, motor vehicle/mixed combustion, waste incinerator/industrial, and diesel/Pb-Zn, but also with the coal combustion factors, perhaps through common transport.     

A global health problem caused by arsenic from natural sources

Arsenic is a carcinogen to both humans and animals. Arsenicals have been associated with cancers of the skin, lung, and bladder. Clinical manifestations of chronic arsenic poisoning include non-cancer end point of hyper- and hypo-pigmentation, keratosis, hypertension, cardiovascular diseases and diabetes. Epidemiological evidence indicates that arsenic concentration exceeding 50 microg l(-1) in the drinking water is not public health protective. The current WHO recommended guideline value for arsenic in drinking water is 10 microg l(-1), whereas many developing countries are still having a value of 50 microg l(-1). It has been estimated that tens of millions of people are at risk exposing to excessive levels of arsenic from both contaminated water and arsenic-bearing coal from natural sources. The global health implication and possible intervention strategies were also discussed in this review article.     

碳源对反硝化除磷效能及N_2O产生的长期影响

基于碳源对反硝化除磷效能以及N2O产生机制尚未明确的现状,采用厌氧/缺氧/好氧序批式反应器(An/A/O-SBR),考察了碳源(乙酸、丙酸和两者的混合酸(摩尔比为1∶1))对反硝化除磷效能和污泥形态的长期影响。结果发现,混合酸系统脱氮除磷效果最稳定,氮和磷平均去除率分别为67.7%和87.0%;而乙酸和丙酸系统较不稳定,氮和磷平均去除率分别为97.6%、51.0%和41.9%、100.0%。混合酸系统检测到明显的N2O释放,而乙酸和丙酸系统的N2O产率较低。     

硫酸铵作为人工气溶胶模拟尘源的研究

硫酸盐、铵盐等水溶性无机盐粒子是大气气溶胶的重要组成部分,为进一步提高高效过滤器性能测试实验的精度,提出了过滤器测试标准要求外的新的人工尘气溶胶发生液（NH4）2SO4,并通过一系列实验,从相关性、粒谱分布、分散度等方面对其气溶胶粒子能否满足测试气溶胶的要求进行验证分析。实验结果表明,（NH4）2SO4和KCl间的相关系数R2为0.994 78,相关性很好;NaCl、KCl和（NH4）2SO4气溶胶的几何标准差分别为0.88、0.85和0.87,呈单分散且分散程度接近,可很好的满足测试气溶胶要求。还获得了可控参数喷气压力与发生溶液质量浓度对（NH4）2SO4气溶胶粒谱分布的影响规律：随喷气压力的增加,气溶胶粒子的粒径减小,分布集中;而随发生溶液质量浓度的增加,粒径增大,导致分散度增加。质量浓度和喷气压力对（NH4）2SO4和KCl气溶胶粒径和分散度作用规律的一致性进一步表明（NH4）2SO4作为测试气溶胶的可行性。     

The sources and forms of phosphorus in marine aerosol particles and rain from Northern New Zealand

Various forms of phosphorus were measured in marine aerosol particles and rain samples collected from the northern tip of the North Island of New Zealand. Approximately 58 % of the total phosphorus in the aerosol particles was organic and 7 % was soluble in deionized water. The remaining 35 % was not released by treatment with potassium persulfate, and it was defined as a refractory fraction. Stepwise regression analyses suggested that (1) the concentrations of organic phosphorus in the aerosol particles were related to those of sodium, which was regarded as sea salt tracer, (2) the concentrations of water soluble phosphorus were correlated with those of aluminum, which was considered an indicator of crustal material and (3) total phosphorus was derived from the ocean and from the earth's crust. The mass particle-size distribution of the refractory and organic phosphorus combined was similar to that of sodium and aluminum. However, on submicrometer particles the concentrations of all forms of phosphorus appeared to increase relative to those of sodium, suggesting that small particle phosphorus may be derived from a non-marine source, possibly weathered crustal material or wind blown fertilizer. The wet deposition rates for water soluble and organic phosphorus were calculated to be 0.30 and 0.61 μg cm ⁻² y ⁻¹, respectively. The dry deposition of these two forms of phosphorus combined (0.14 μg cm ⁻² y ⁻¹ ) was clearly lower than the wet deposition rate. Total deposition of phosphorus to the site was estimated to be 1.5μgcm⁻²y⁻¹.     

Characteristic number size distribution of aerosol during Asian dust period in Korea

The size-separated number concentrations of aerosols ranging from 0.3 to 25 μm were observed in Seoul and Anmyon Island in the west coast of Korea during Asian dust period in Spring 1998. During the heavy dust period, the number size distributions of aerosols observed in both places were characterized by decreases in small size<0.5 μm and increase in large size between 1.35 and 10 μm. For particles in this range, there was a good correlation between number concentrations observed in both two places. The number of coarse particles >10 μm showed a distinct diurnal variation without a significant change in amplitude, which was more pronounced in Seoul. It suggests that coarse particles were more affected by local sources. Trajectories back in time showed that the air collected in Korea during dust period originated from desert regions in the central part of China. From these results, it was evident that increased particles in the range of 1.35–10 μm during dust source period represented mineral components, which originated possibly from the dust source regions.     

Dissolution and solubility of trace metals from natural and anthropogenic aerosol particulate matter

An open flow reactor is used to simulate the dissolution process of mineral aerosol particles in atmospheric water droplets. Data on dissolution kinetic and solubility are provided for the major trace metals from two kinds of matrix: alumino-silicated and carbonaceous sample. The results emphasise that the metals contained in the carbonaceous aerosols are easier dissolved than in the alumino-silicated particles. The released concentrations are not related to the total metal composition or the origin of particles, but are directly associated with the type of liaisons whereby the metals are bound in the solid matrix. Thus, the metals coming from carbonaceous particles are adsorbed impurities or salts and hence are very soluble and with a dissolution hardly dependent on pH, whereas the metals dissolved from alumino-silicated particles are less soluble, notably the ones constitutive of the matrix network (Fe, Mn), and with a dissolution highly influenced by pH. Consequently, in the regions with an anthropogenic influence, the dissolved concentrations of metals found in the atmospheric waters are mainly governed by the elemental carbon content. Moreover, it appears that the dissolution kinetic of metals is not constant as a function of time. The dissolution rates are very rapid in the first 20 min of leaching and then they are stabilised to lower values in comparison to initial rates. By consequence, the total dissolved metal content is provided after the first 20 min of the droplet lifetime. For this reason, the effects of trace metals on the atmospheric aqueous chemistry and as atmospheric wet input to the marine biota are maximal for "aged" droplets.     

A comparison of microplastic contamination in freshwater fish from natural and farmed sources

Contamination of aquatic systems mainly by urbanization and poor sanitation, deficient or lack of wastewater treatments, dumping of solid residues, and run off has led to the presence of particles, including manmade polymers, in tissues of many marine and freshwater species. In this study, the prevalence of microplastics (MPs) in freshwater fish from farmed and natural sources was investigated. Oreochromis niloticus from aquaculture farms in the Huila region in Colombia, and two local species (Prochilodus magdalenae and Pimelodus grosskopfii), naturally present in surface waters were sampled. Of the particles identified, fragments were the predominant type in the three tissue types (stomach, gill, and flesh) derived from farmed and natural fishes. MicroFT-IR spectroscopy was conducted on 208 randomly selected samples, with 22% of particles identified as MPs based on spectra with a match rate ≥ 70%. A total of 53% of identified particles corresponded to cellophane/cellulose, the most abundant particle found in all fish. Not all fish contained MPs: 44% of Oreochromis farmed fish contained MPs, while 75% of natural source fish contained MPs in any of its tissues. Overall, polyethylene terephthalate (PET), polyester (PES), and polyethylene (PE) were the prevalent MPs found in the freshwater fish. A broader variety of polymer types was observed in farmed fish. The edible flesh part of fish presented the lower prevalence of MPs compared to gill and stomach (gut), with gut displaying a higher frequency and diversity of MPs. This preliminary study suggests that the incidence and type of MPs varies in farmed verses natural fish sources as well as across different tissue types, with significantly less detected within the edible flesh tissues compared with stomach and gill tissues.

     

Secondary organic aerosol production from aqueous photooxidation of glycolaldehyde: Laboratory experiments

Organic particulate matter (PM) formed in the atmosphere (secondary organic aerosol; SOA) is a substantial yet poorly understood contributor to atmospheric PM. Aqueous photooxidation in clouds, fogs and aerosols is a newly recognized SOA formation pathway. This study investigates the potential for aqueous glycolaldehyde oxidation to produce low volatility products that contribute SOA mass. To our knowledge, this is the first confirmation that aqueous oxidation of glycolaldehyde via the hydroxyl radical forms glyoxal and glycolic acid, as previously assumed. Subsequent reactions form formic acid, glyoxylic acid, and oxalic acid as expected. Unexpected products include malonic acid, succinic acid, and higher molecular weight compounds, including oligomers. Due to (1) the large source strength of glycolaldehyde from precursors such as isoprene and ethene, (2) its water solubility, and (3) the aqueous formation of low volatility products (organic acids and oligomers), we predict that aqueous photooxidation of glycolaldehyde and other aldehydes in cloud, fog, and aerosol water is an important source of SOA and that incorporation of this SOA formation pathway in chemical transport models will help explain the current under-prediction of organic PM concentrations.     

Identification of sources of Phoenix aerosol by positive matrix factorization

Chemical composition data for fine and coarse particles collected in Phoenix, AZ, were analyzed using positive matrix factorization (PMF). The objective was to identify the possible aerosol sources at the sampling site. PMF uses estimates of the error in the data to provide optimum data point scaling and permits a better treatment of missing and below-detection-limit values. It also applies nonnegativity constraints to the factors. Two sets of fine particle samples were collected by different samplers. Each of the resulting fine particle data sets was analyzed separately. For each fine particle data set, eight factors were obtained, identified as (1) biomass burning characterized by high concentrations of organic carbon (OC), elemental carbon (EC), and K; (2) wood burning with high concentrations of Na, K, OC, and EC; (3) motor vehicles with high concentrations of OC and EC; (4) nonferrous smelting process characterized by Cu, Zn, As, and Pb; (5) heavy-duty diesel characterized by high EC, OC, and Mn; (6) sea-salt factor dominated by Na and Cl; (7) soil with high values for Al, Si, Ca, Ti, and Fe; and (8) secondary aerosol with SO4(-2) and OC that may represent coal-fired power plant emissions. For the coarse particle samples, a five-factor model gave source profiles that are attributed to be (1) sea salt, (2) soil, (3) Fe source/motor vehicle, (4) construction (high Ca), and (5) coal-fired power plant. Regression of the PM mass against the factor scores was performed to estimate the mass contributions of the resolved sources. The major sources for the fine particles were motor vehicles, vegetation burning factors (biomass and wood burning), and coal-fired power plants. These sources contributed most of the fine aerosol mass by emitting carbonaceous particles, and they have higher contributions in winter. For the coarse particles, the major source contributions were soil and construction (high Ca). These sources also peaked in winter.     

Locations and preferred pathways of possible sources of Arctic aerosol

The chemical composition of particles collected at Alert, Northwest Territories, Canada, show strong, persistent seasonal variations. In a previous study, a 2-way/3-way mixed factor model was performed on the weekly average concentrations of 24 aerosol components measured over the period from 1980 to 1991. The Multilinear Engine (ME), a new mathematical technique, was used to obtain the solution. The two modes of the 2-way model consist of the source composition profiles and mass contributions over the 11 yr, while for the three modes of the 3-way model, source profiles, mass contributions variations over the weeks within a year, and the year-to-year variation over the 11 yr within the measurement period. Five 2-way and two 3-way factors were found to provide a good fit to the data and were easily interpreted. In this investigation, potential source contribution function (PSCF) analysis was applied to the source contributions derived from the ME analysis by incorporating meteorological information in the form of 5-d air parcel back trajectories. The potential locations and/or the preferred pathways of these possible sources were then determined by the PSCF analysis.     

福州市东郊大气气溶胶物理特性及其来源分析

利用GRIMM180环境颗粒物监测仪观测了2012年12月至2013年11月福州市东郊气溶胶数浓度和质量浓度,分析了该地区气溶胶粒子的主要物理特征。结果表明,福州市东郊气溶胶数浓度和质量浓度都有着明显的季节变化特征,冬季最高,夏季最低;与京津冀、长三角和西部大城市相比,福州市东郊气溶胶质量浓度较低,空气质量较好。从PM_(2.5)在PM10中所占比例来看,PM_(2.5)是影响福州市东郊空气质量最主要的因子。在冬季气溶胶数浓度日变化基本呈双峰分布,早晨和傍晚分别出现峰值;夏季呈单峰分布,峰值出现在午后。利用后向轨迹HYSPLIT-4模式,经过聚类分析得到,在春季、秋季和冬季福州市气团输送来源主要是北方内陆和福州本地及邻近地区;而在夏季海洋是气团的主要输送来源。     

Determination of sources of atmospheric aerosol in Copenhagen based on receptor models

A statistical analysis is presented of atmospheric aerosol element composition data collected at five monitoring stations in Copenhagen in 1983. The objective is to identify sources of air pollution, to estimate the variation of total suspended particles (TSP) for the different sources and to calculate the annual average source contribution to TSP. The basis for analysis is the chemical mass balance equations. Factor analysis methods are used to identify major sources of pollution and the contribution from each of the sources to the variation in TSP is estimated by an additional multiple regression. Finally, the influence of serial correlations between daily element contributions is discussed and it is stressed that the result of the analysis is not seriously affected by these correlations.     

Occurrence of alternative flame retardants in indoor dust from New Zealand: indoor sources and human exposure assessment

Due to worldwide restrictions on polybrominated diphenyl ethers (PBDEs), the demand for alternative flame retardants (AFRs), such as organophosphate flame retardants (OPFRs), novel brominated FRs (NBFRs) and hexabromocyclododecanes (HBCDs), has recently increased. Little is known about human exposure to NBFRs and OPFRs and that their levels in dust have been scarcely evaluated worldwide. To increase the knowledge regarding these chemicals, we measured concentrations of five major NBFRs, ten OPFRs and three HBCD isomers in indoor dust from New Zealand homes. Dust samples were taken from living room floors (n=34) and from mattresses of the same houses (n=16). Concentrations (ngg(-1)) of NBFRs were: 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) (<2-175), decabromodiphenyl ethane (DBDPE) (<5-1430), 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (TBB) (<2-2285) and bis(2-ethylhexyl)-3,4,5,6-tetrabromophthalate (TBPH) (<2-640). For OPFRs, concentrations (ngg(-1)) ranged between: tri-ethyl-phosphate (TEP) (<10-235), tri-n-butyl-phosphate (TnBP) (<20-7545), tris-(2-chloroethyl)-phosphate (TCEP) (<20-7605), tris-(1-chloro-2-propyl) phosphate (TCPP) (20-7615), tri-(2-butoxyethyl)-phosphate (TBEP) (50-27325), tris-(2,3-dichloropropyl)-phosphate (TDCPP) (20-16560), tri-phenyl-phosphate (TPhP) (20-35190), and tri-cresyl-phosphate (TCP) (<50-3760). HBCD concentrations fell in the range <2-4100ngg(-1). BTBPE, DBDPE, TBPH, TBEP, and TnBP showed significant positive correlation (p<0.05) between their concentrations in mattresses and the corresponding floor dust (n=16). These data were used to derive a range of plausible exposure scenarios. Although the estimated exposure is well below the corresponding reference doses (RfDs), caution is needed given the likely future increase in use of these FRs and the currently unknown contribution to human exposure by other pathways such as inhalation and diet.     

Concentrations and sources of carbonaceous aerosol in the atmosphere of Summit,Greenland

High-volume PM_2.5 samples were collected at Summit, Greenland for approximately six months from late May through December of 2006. Filters were composited and analyzed for source tracer compounds. The individual organic compounds measured at Summit are orders of magnitude smaller than concentrations measured at other sites, including locations representative of remote oceanic, and remote and urban continental aerosol. The measured tracers were used to quantify the contribution of biomass burning (0.6–0.9 ng C m^?3), vegetative detritus (0.3–0.9 ng C m^?3), and fossil fuel combustion (0.1–0.8 ng C m^?3) sources, 4% of OC total, to atmospheric organic carbon concentrations at the remote location of Summit, Greenland. The unapportioned organic carbon (96%) during the early summer period correlates well with the fraction of water soluble organic carbon, indicating secondary organic aerosol as a large source of organic carbon, supported by the active photochemistry occurring at Summit. To the author's knowledge, this paper represents the first source apportionment results for the polar free troposphere.     

Identification and sources of tarry matter in deposited dust in some Egyptian cities

Tarry matter is one of the minor constituents of deposited dust. It was determined in concentrations of about 0.5% or less in the deposits obtained from five Egyptian cities, namely: Beni-Suef, Minya, Assiut, Sohag and Qena.Qualitative i.r. spectroscopic analysis showed that the major organic constituents of deposited tarry matter are: (a) alkanes (saturated aliphatic hydrocarbons), emitted through the incomplete combustion of fuels; (b) phosphines (organic phosphorous compounds), produced by the anaerobic bacterial action on organic deposits and adsorbed on clay minerals; and (c) silicon hydride, which is one of components of the organo-silicon compounds associated with clay minerals.