Fine Particulates Research Articles

Mesophilic bioleaching performance of copper, cobalt and nickel with emphasis on complex orebodies of the Democratic Republic of Congo: a review of dynamic interactions between solids loading, microbiota activity and growth

The copper, cobalt and nickel ores are still currently mined in the world. Its complex mineralogy creates extraction challenges by means of conventional metallurgical methods. Meanwhile, dealing with mesophilic strains in leaching process requires a compromise between solid loading and microbiota activity and growth. That is why, the influence of solid loading with fine or coarse particulates, the cell disturbance during the metal–microbes interactions depending upon the influence of gangue nature as well as metallic ions concentration on bacterial tolerance and the chemical and biological pathways involved in bioleaching mechanism of complex ores are summarised in detail in this paper. The current trends in mechanism research and diverse discovered set of microbiota and bacterial population coupled with bacterial adaptation methods contribute to optimise and improve the metals leaching performance and knowledge. In addition, the different existing complex mineralogical structures elaborate a main indirect mechanism with two different transitory mechanisms, before metal is converted into metal sulphate as wealthily explained in this comprehensive review. More data for cost analysis concomitant with extraction efficiency of metals using mesophilic bioleaching process are needed. However, it does not mean that other options are excluded in order to set a bio-hydrometallurgical chain. In fact, to consider also the concentration and purification of the pregnant leaching solution via phase separation and solvent extraction will be helpful. This obeys to the idea of option trees, where possible options are then systematically gaged with respect to critical criteria.

Detecting asynchrony of two series using multiscale cross-trend sample entropy

We develop a new cross-sample entropy, namely the multiscale cross-trend sample entropy (MCTSE), to investigate the synchronism of dynamical structure regarding two series with potential trends. It incorporates symbolic representation and polynomial fitting trend. Numerical tests illustrated that the newly proposed MCTSE can address the series with various trends well and detect asynchrony between two series more sensitively. The MCTSE is used to analyze the asynchrony between air quality index (AQI) series of Beijing, Changsha and Zhuhai and the series of six air quality impact factors (PM2.5, PM10, $$\hbox {SO}_2$$, CO, $$\hbox {NO}_2$$ and $$\hbox {O}_3$$). We find that the consistency between the AQI series and the two fine particulates series of PM2.5 and PM10 is obviously higher than other four factors series. Comparing the entropy values of these pollution factors between every two cities, we also found that the pollutants in Changsha and Zhuhai are similar in quality, but they are quite different from those in Beijing. These findings help to further explore the similarities and differences in dynamic structure of the AQI series and identify the main pollutant. This has certain reference value for the reduction and control of similar pollutants.

Global and regional model simulations of atmospheric ammonia

Ammonia (NH3) is a basic gas of significant atmospheric interest because of its role in the possible formation of fine particulates and because it is a source of fixed nitrogen in soils and plants. NH3 processing in the atmosphere has been simulated using two 3-D models: the global chemistry transport model, STOCHEM-CRI and the regional coupled meteorological-chemical model, WRF-Chem-CRI. From analysis of STOCHEM-CRI simulations, NH3 removal fluxes of dry deposition (24.6 Tg(N)/yr), wet deposition (20.8 Tg(N)/yr), NH4+ formation (25.6 Tg(N)/yr) and reaction with OH (1.7 Tg(N)/yr) have been calculated, making a global annual average burden of 0.22 Tg(N) and life-time of 1.1 days. The gas-phase loss by OH, NO3 and stabilized Criegee intermediates contribute 2.3%, <1% and < 1%, respectively to the total global loss of tropospheric NH3. The highest concentrations of NH3 are found to be in the region of South and East Asia, which are associated mostly with agricultural NH3 emissions. Loss of surface NH3 by reaction with OH increases by up to 25% along the equator because of the abundances of ozone. Comparison of satellite observations and model results give a better understanding of the temporal and spatial variations of atmospheric NH3 on a global and regional scales. Using the anthropogenic seasonal NH3 emission class in the model gives a poor representation of seasonal NH3. The positive bias in Africa and South America for all seasons is likely due to undetermined sources in the model such as underestimated biomass burning emissions of NH3 adopted in the model. The regional model results over North-West Europe during summer months are biased low compared with the measurements- suggesting either missing sources, or too efficient loss processes in the region.

Development of a Test Set for Motoring Fine Particulate

Development of a Test Set for Motoring Fine Particulate

The transport and mass balance of fallout radionuclides in Brotherswater, Cumbria (UK)

This paper investigates the role of intervening transport processes on lake sediment records of the atmospherically deposited radionuclides 210Pb and 137Cs. Brotherswater is of particular interest to this issue in that its large catchment/lake area ratio and short water residence time are likely to amplify the influence of these processes, both from the catchment and through the water column. Brotherswater is also unique in being the site of two earlier multicore studies that, together with the present study, span a period of 4 decades. Measurements of fallout radionuclides were made on soil cores, suspended sediments and sediment cores, and the results combined with those from earlier studies to construct mass balances for 210Pb and 137Cs in Brotherswater. The results showed that catchment inputs accounted for 63% of 210Pb entering the lake. Further, just 47% of 210Pb entering the water column was delivered to the sediment record. For comparison, in an earlier study at nearby Blelham Tarn with a relatively smaller catchment but longer water residence time it was shown that 47% of 210Pb inputs were delivered via the catchment, 75% of which were delivered to the sediment record. Results from both sites suggest that 210Pb is predominantly transported on fine particulates with a mean particle size of 3–4 μm. Their relatively slow removal from the water column allows them to be transported relatively uniformly throughout the lake and may help account for the fact that simple 210Pb dating models are relatively reliable in spite of the complexities of the transport processes. Mass balance calculations for 137Cs are more complicated because of the variable fallout record. Measurements of 137Cs in the input stream and water column showed that catchment inputs are still significant 30 years after the last significant fallout (Chernobyl). Modelled results showed that catchment inputs delayed the date of peak inputs of weapons test fallout to the lake though by no more than 2 years. Although the results presented here are primarily concerned with fallout radionuclides and their reliability for dating, they also have implications for the use of sediment archives in reconstructing historical records of other atmospherically deposited substances such as trace metals or persistent organic pollutants.

Characteristics of Fine Particulate Matter (PM2.5) over Urban, Suburban, and Rural Areas of Hong Kong

In urban areas, fine particulate matter (PM2.5) associated with local vehicle emissions can cause respiratory and cardiorespiratory disease and increased mortality rates, but less so in rural areas. However, Hong Kong may be a special case, since the whole territory often suffers from regional haze from nearby mainland China, as well as local sources. Therefore, to understand which areas of Hong Kong may be affected by damaging levels of fine particulates, PM2.5 data were obtained from March 2005 to February 2009 for urban, suburban, and rural air quality monitoring stations; namely Central (city area, commercial area, and urban populated area), Tsuen Wan (city area, commercial area, urban populated, and residential area), Tung Chung (suburban and residential area), Yuen Long (urban and residential area), and Tap Mun (remote rural area). To evaluate the relative contributions of regional and local pollution sources, the study aimed to test the influence of weather conditions on PM2.5 concentrations. Thus, meteorological parameters including temperature, relative humidity, wind speed, and wind directions were obtained from the Hong Kong Observatory. The results showed that Hong Kong’s air quality is mainly affected by regional aerosol emissions, either transported from the land or ocean, as similar patterns of variations in PM2.5 concentrations were observed over urban, suburban, and rural areas of Hong Kong. Only slightly higher PM2.5 concentrations were observed over urban sites, such as Central, compared to suburban and rural sites, which could be attributed to local automobile emissions. Results showed that meteorological parameters have the potential to explain 80% of the variability in daily mean PM2.5 concentrations—at Yuen Long, 77% at Tung Chung, 72% at Central, 71% at Tsuen Wan, and 67% at Tap Mun, during the spring to summer part of the year. The results provide not only a better understanding of the impact of regional long-distance transport of air pollutants on Hong Kong’s air quality but also a reference for future regional-scale collaboration on air quality management.

Optical properties, source apportionment and redox activity of humic-like substances (HULIS) in airborne fine particulates in Hong Kong

Humic-like substances (HULIS) account for a considerable fraction of water-soluble organic matter (WSOM) in ambient fine particulates (PM2.5) over the world. However, systemic studies regarding the chemical characteristics, sources and redox activity of HULIS are still limited. In this study, the mass concentration, optical properties, and reactive oxygen species (ROS)-generation potential of HULIS were investigated in PM2.5 samples collected in Hong Kong during 2011–2012, and they all showed higher levels on days under regional pollution than on days under long range transport (LRT) pollution and local emissions. Positive matrix factorization (PMF) analysis was conducted regarding the mass concentration and dithiothreitol (DTT) activity of HULIS. Four primary sources (i.e. marine vessels, industrial exhaust, biomass burning, and vehicle emissions), and two secondary sources (i.e. secondary organic aerosol formation and secondary sulfate) were identified. Most sources showed higher contributions to both the mass concentration and DTT activity of HULIS on regional days than on LRT and local days, except that marine vessels had a higher contribution on local days than the other two synoptic conditions. Secondary processes were the major contributor to HULIS (54.9%) throughout the year, followed by biomass burning (27.4%) and industrial exhaust (14.7%). As for the DTT activity of HULIS, biomass burning (62.9%) and secondary processes (25.4%) were found to be the top two contributors. Intrinsic ROS-generation potential of HULIS was also investigated by normalizing the DTT activity by HULIS mass in each source. HULIS from biomass burning were the most DTT-active, followed by marine vessels; while HULIS formed through secondary processes were the least DTT-active. For the optical properties of HULIS, multiple linear regression model was adopted to evaluate the contributions of various sources to the light absorbing ability of HULIS. Biomass burning was found to be the only source significantly associated with the light absorbing property of HULIS.

Assessing Agreement in Exposure Classification between Proximity-Based Metrics and Air Monitoring Data in Epidemiology Studies of Unconventional Resource Development.

Recent studies of unconventional resource development (URD) and adverse health effects have been limited by distance-based exposure surrogates. Our study compared exposure classifications between air pollutant concentrations and “well activity” (WA) metrics, which are distance-based exposure proxies used in Marcellus-area studies to reflect variation in time and space of residential URD activity. We compiled Pennsylvania air monitoring data for benzene, carbon monoxide, nitrogen dioxide, ozone, fine particulates and sulfur dioxide, and combined this with data on nearly 9000 Pennsylvania wells. We replicated WA calculations using geo-coordinates of monitors to represent residences and compared exposure categories from air measurements and WA at the site of each monitor. There was little agreement between the two methods for the pollutants included in the analysis, with most weighted kappa coefficients between −0.1 and 0.1. The exposure categories agreed for about 25% of the observations and assigned inverse categories 16%–29% of the time, depending on the pollutant. Our results indicate that WA measures did not adequately distinguish categories of air pollutant exposures and employing them in epidemiology studies can result in misclassification of exposure. This underscores the need for more robust exposure assessment in future analyses and cautious interpretation of these existing studies.

Vehicular Particulate Matter (PM) Characteristics Impact Vascular Outcomes Following Inhalation.

Roadside proximity and exposure to mixed vehicular emissions (MVE) have been linked to adverse pulmonary and vascular outcomes. However, because of the complex nature of the contribution of particulate matter (PM) versus gases, it is difficult to decipher the precise causative factors regarding PM and the copollutant gaseous fraction. To this end, C57BL/6 and apolipoprotein E knockout mice (ApoE-/-) were exposed to either filtered air (FA), fine particulate (FP), FP+gases (FP+G), ultrafine particulate (UFP), or UFP+gases (UFP+G). Two different timeframes were employed: 1-day (acute) or 30-day (subchronic) exposures. Examined biological endpoints included aortic vasoreactivity, aortic lesion quantification, and aortic mRNA expression. Impairments in vasorelaxation were observed following acute exposure to FP+G in C57BL/6 animals and FP, UFP, and UFP+G in ApoE-/- animals. These effects were completely abrogated or markedly reduced following subchronic exposure. Aortic lesion quantification in ApoE-/- animals indicated a significant increase in atheroma size in the UFP-, FP-, and FP+G-exposed groups. Additionally, ApoE-/- mice demonstrated a significant fold increase in TNFα expression following FP+G exposure and ET-1 following UFP exposure. Interestingly, C57BL/6 aortic gene expression varied widely across exposure groups. TNFα decreased significantly following FP exposure and CCL-5 decreased in the UFP-, FP-, and FP+G-exposed groups. Conversely, ET-1, CCL-2, and CXCL-1 were all significantly upregulated in the FP+G group. These findings suggest that gas-particle interactions may play a role in vascular toxicity, but the contribution of surface area is not clear.

Effects of PM2.5 on Skeletal Muscle Mass and Body Fat Mass of the Elderly in Taipei, Taiwan

Loss of skeletal muscle mass is common with aging and can cause morbidity and mortality in the elderly. The effects of particulate air pollution on skeletal muscle mass is not known. The study aims to assess the chronic effects of ambient fine particulates (PM2.5) on the body composition of the elderly. From October 2015 to November 2016, a cross-sectional survey on 530 elderly (age > = 65 years) was conducted in the Taipei Basin, Taiwan. The body composition was measured by bioelectrical impedance analysis (InBody 120). One year exposure to air pollution was estimated using the Kriging method at the participant’s residence. Multiple linear regression analysis, after adjustments for demographics and co-pollutants, was used to examine the effects of PM2.5 on body composition indices and force of handgrip. Changes in body composition for an interquartile (1.4 μm/m3) increase in PM2.5 concentration included a 0.4 kg (95% confidence interval (CI): −0.31, −0.58; p < 0.0001) decrease in skeletal muscle mass (2.0%) and a 0.7 kg (95% CI: 0.47, 0.91; p < 0.0001) increase in body fat mass (3.6%). While PM2.5 reduced fat free mass in the upper extremities and trunk, but not in the lower extremities, it increased body fat mass in the three parts. There was no significant effect of PM2.5 on handgrip force. Higher physical activity (versus lower than median) was associated with less detrimental effect of PM2.5 on skeletal muscle mass and body fat mass (p values for interaction term: 0.009 and 0.013, respectively). Long-term PM2.5 exposure is associated with decreased skeletal muscle mass and increased body fat mass in the elderly, which can be ameliorated by physical activity.

Particulate control devices in Kemper County IGCC Project

Southern Company has commissioned a 2 × 1 Integrated Gasification Combined Cycle (IGCC) facility in Kemper County, Mississippi. The plant demonstrated the Transport Integrated Gasification (TRIGTM) technology developed by Southern Company, KBR, and the U.S. Department of Energy (DOE). With a capability of generating up to 524 MW net, the plant also captures CO2 from syngas produced from locally mined Mississippi lignite. Particulate Control Devices (PCDs), designed by Pall Corporation, are a critical component of the TRIGTM gasification process. The PCDs use dry filtration technology to remove essentially all the fine particulates from the syngas before it is sent to downstream processes for further gas clean-up, CO2 capture, and, finally for use in combustion turbines to generate power.The Kemper PCDs are designed to accommodate different types of filter elements for future optimization. The initial installation features the 2.5-meter long iron aluminide (FEAL) filter elements based on the extensive testing experience gained at the Power Systems Development Facility (PSDF). The PCD back-pulse system is equipped with the Coupled Pressure Pulse (CPPTM) blowback technology developed jointly by Pall’s Schumacher Division and Karlsruhe Institute of Technology for online filter element cleaning. It is the first CPPTM application of this scale used for high-pressure, high-temperature filtration in a gasification process. The Kemper facility has achieved integrated operation with production of electricity, CO2, and other by-products from syngas per design specifications. This paper describes the operations, performance, and technical issues of both the PCD and the fines cooling and handling system that were encountered during the installation, unit commissioning, and extended operation with lignite.

Destabilization of fine solids suspended in oil media through wettability modification and water-assisted agglomeration

Removing fine solids suspended in aqueous or oil media is crucial in many chemical, petroleum and environmental engineering processes with ever-increasing demands on improving product quality and meeting waste management standard. In oil industry, the removal of fine mineral solids is required to achieve high-quality oil products but remains a great challenge. This difficulty is due to hydrophobic and oleophilic nature of the mineral matters and small dimension of fine particulates. Here we introduce a two-step agglomeration method to destabilize bitumen-coated silica particles in cyclohexane by simply modifying their surface wettability using the amphiphilic polymer poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEG-PPG-PEG), and then adding a small amount of water to trigger the formation of large particle aggregates. By sedimentation tests, we demonstrate that the two-step method can significantly enhance settling rate of the particles and reduce content of residual solids in the supernatant simultaneously. The underlying physical interaction mechanisms have been investigated using atomic force microscope (AFM) and quartz crystal microbalance with dissipation monitoring (QCM-D). The results suggest that PEG-PPG-PEG can readily adsorb to the bitumen-coated silica surface, thereby altering the surface from hydrophobic to hydrophilic and tuning its interaction with added water drops from repulsion to attraction in cyclohexane. This work provides useful insights into the development of effective strategies of removing suspended fine solids from oil media in petroleum production processes.

Displacement of powders from surface by shock and plasma generated by electrostatic discharge

Fine particulates were removed from a flat surface and cavities by shock/plasma produced by electro-static discharge (ESD). The ESD in air formed by discharging a capacitor between two 1-mm separated pin electrodes. Both irregularly shaped glass and spherical magnesium served as contaminant particulates. The ESD energy and pressure produced by the shock were characterized. Both powders were effectively displaced by the ESD-generated shock and plasma. Displaced particles were de-agglomerated. While glass melted, flammable magnesium powder did not ignite. ESD-generated plasma and shock offer an attractive, inexpensive, and safe alternative to laser shock cleaning methods for removal particulate contaminants from surfaces.

Risks and Causes of Population Exposure to Cumulative Fine Particulate (PM2.5) Pollution in China

AbstractChina's policy on atmospheric pollution is changeable in recent years. The single‐year estimated population exposure to air pollution is widely used in China where has the largest population and the heaviest fine particulate (PM2.5) pollution worldwide. However, the single‐year estimate introduces considerable uncertainty and loses consideration on multiyear cumulative exposure, thus may underestimate the burden of disease and mislead decisions regarding environmental conservation. We thus estimate the cumulative population exposure to PM2.5 pollution from 2000 to 2015. Areas with PM2.5 &gt; 35 μg/m3 within China's territory increased from an average of 39% (2000–2005) to 42% (2006–2015), causing 471.6 million population at 58.8 × 104 km2 were exposed to 16 years' cumulative exposure to PM2.5 &gt; 35 μg/m3. The migrant population contributed a major proportion of the increased population exposure, especially in East China's rapidly urbanizing areas. Cumulative population exposure to air pollution would provide a better understanding on the long‐term health risk and may suggest to a long, stable, and effective environmental protection regulation and policy should be carried out in China.

Chemical composition of dew water at a suburban site in Nanjing, China, during the 2016–2017 winter

A dew condenser was used to collect dew and frost samples to investigate the chemical properties of dew water for comparison with frost, rain and fog in Nanjing, China during the 2016–2017 winter. Twenty-three separate ambient dew samples were collected at a grassland site in suburban Nanjing, China, from 1st November 2016 to 20th January 2017. Six frost samples, two fog water samples and 13 rainwater samples were also collected for comparative study. Cations (Na+, Ca2+, NH4+, K+, and Mg2+), anions (NO3−, NO2−, Cl−, SO42−, and F−) and pH were detected and measured in all wet depositional samples. In addition, seven kinds of water-soluble ions (WSIs) in atmospheric fine particulates (PM2.5) and atmospheric gas (SO2 and NH3) concentrations were investigated. The field study elucidated that dew water resembles frost water, with WSIs ranked in the order of Ca2+> NH4+> Na+> Mg2+> K+ for cations and SO42− > NO3− > Cl− > NO2− > F− for anions. Most dew and frost samples were alkaline and not as acidic as the rainwater and fog water samples. The mean concentrations of various ions and total ionic content (TIC) in the fog samples were the highest, while the ion concentration ranges in the dew, rain and frost samples were similar. The neutralization strength decreased in the order of NH4+>Ca2+>Mg2+>K+ for the fog samples and decreased in the order of Ca2+> NH4+>Mg2+>K+ for the dew, frost and rainwater samples. A high pairwise correlation between K+, Mg2+ and Ca2+ was observed, which means these cations shared a common crustal source. The SO42−, NO2− and Cl− ions were closely correlated, indicating that the ions were released simultaneously from anthropogenic sources. The low and negative correlations among the NO3−, SO42− and NH4+ ions in the dew water and PM2.5 may imply that fine-mode aerosols have little impact on the composition of dew, which means that the dew water component was dominated by coarse-mode aerosols. The NH3 in the atmosphere plays an important role in dew water due to the strong relationship between NH3 and NH4+.

The relationship between anticyclonic anomalies in northeastern Asia and severe haze in the Beijing–Tianjin–Hebei region

Abstract. Haze pollution in the Beijing–Tianjin–Hebei (BTH) region has become increasingly more severe and persistent in recent years. To better understand the formation of severe haze and its relationship with anticyclonic anomalies over northeastern Asia (AANA), this research focused on severe haze over the BTH region occurring in December during 2014–2016 and examined the impacts of AANA. The results indicated that local meteorological conditions were conducive to severe haze (such as weaker surface winds, a stronger temperature inversion, a shallower boundary layer, and higher relative humidity) and were all closely related to AANA. During severe haze episodes, AANA remained strong in the middle upper troposphere, generating anomalous southeasterly winds near the surface. This effect not only promoted the accumulation of pollutants due to the unique topographical conditions in the BTH region but also caused warm advection in lower levels, which was the main cause of the formation and development of a temperature inversion layer. As a synoptic-scale circulation, AANA were accompanied by anomalous vertical motions in the surrounding areas, which weakened the meridional circulation over the BTH region. Intrusions of clean air from upper levels to the surface and downward transport of westerly momentum at mid-levels and upper levels were suppressed, resulting in weaker northerly winds near the surface and a shallower boundary layer. The thermally indirect zonal circulation between the BTH region and western Pacific triggered by AANA provided a persistent source of moisture for the BTH region, which strengthened the development of severe haze by promoting the growth of fine particulates. The advance and retreat of AANA often corresponded with the emergence and dissipation of severe haze, illustrating that AANA could be effective forecast indicators for air quality.

The occupational exposure and ventilation of welding workstations

Welding is a basic technology for joining metallic materials and plastics. The high occupational exposure of welders results from the presence of various harmful factors that accompany welding processes, including the emission of a mixture of fine particulates (dust) and chemical substances (gases) into the working environment. Mechanical ventilation is the main way to reduce the concentration of air pollutants in the areas where welding works are carried. The article presents the characteristics of welding fumes, welding process parameters and methods of air distribution with ventilation devices and installations in rooms with welding workstations.

Field measurements on particle size distributions and emission characteristics of PM10 in a cement plant of China

The particle size distributions (PSDs) and the characteristics of the particulate matter (PM) from cement plants are of importance for the air pollution control strategies. The study focuses on the PSDs and emission characteristics of PM10 in the flue gas from the preheater and in the hot air out from the clinker cooler in a cement plant equipped with a conditioning tower, two raw mills, a gravity settler and two fabric filters. A Dekati low pressure impactor (DLPI) with a cyclone was performed to sample the PM10 at the inlet/outlet of the above devices. The PM10 at the outlet of SP boiler and at the inlet of the gravity settler both present a bi-modal distribution, with a fine mode at 0.1–0.4 μm and a coarse mode at 1.0–5.0 μm. The PM10 emitted from the flue gas and the hot air into the atmosphere both present a tri-modal distribution, with a fine mode at 0.2–0.5/0.06–0.2 μm, a middle mode at 0.5–2.5/0.2–0.6 μm and a coarse mode at 5.0–10.0/3.0–6.0 μm. The mass concentration of PM2.5 increases by 17.74% at the outlet of the raw mill due to the mechanical fragmentation and flow transport. The spraying and cooling of the conditioning tower promote the agglomeration and growth of fine particulates, and reduce the concentration proportion of PM2.5 to PM10 from 89.40 to 70.93%. The emission factors of PM10, PM2.5 and PM1 in the flue gas are 0.017–0.031, 0.005–0.015 and 0.002–0.007 kg/t, respectively; while they are 0.005, 0.003 and 0.001 in the hot air, respectively.

Assessment of source profiles for suspended particulate pollutants in Ibadan, Nigeria using positive matrix factorization

Positive Matrix Factorization receptor model developed by the United States Environmental Protection Agency known as EPA PMF receptor model and reconstructed mass model were applied to air pollution data collected over Ibadan south west Nigeria. The essence was to determine the source profiles responsible for the high pollution level of Ibadan and to compare the sources resolved by these two methods. Particulate matter load was sampled over Ibadan, southwest Nigeria with the aid of low volume Gent air sampler, equipped with the Norwegian Institute for Air Research (NILU) Stacked Filter Unit (SFU). Two separate 47-mm nuclepore filters were mounted on the SFU to collect both fine and coarse particulates separately. Trace elements were determined using instrumental neutron activation analysis (INAA) and energy dispersive x-ray fluorescence (EDXRF) spectrometry. Five factors were resolved each for both fine and coarse fractions using EPA PMF. For the fine fraction, soil dust, vehicular emission, oil combustion, open burning and copper-rich source were the major sources of fine particulates over Ibadan city contributing 42, 16, 10, 22 and 10% respectively to the total aerosol loading over Ibadan. Vehicular emission, continental soil, sea salt, locally generated dust and copper-rich source were the sources identified for the coarse particulates. These contributed 7, 49, 13, 23 and 8% respectively. It was observed that emission from open burning was very high (22%), being the second largest contributor to the fine particulates. Reconstructed mass model showed good agreement with PMF in implicating soil dust as the major contributor of airborne pollutants over Ibadan. There was good correlation between the reconstructed mass and the measured mass with r 2 values of 0.87 and 0.98 for fine and coarse particulates respectively. The result of this work showed that re-suspended soil particulates were the major constituents of airborne particulate matter over Ibadan, with over 70 % contribution to the coarse mass and over 40 % contribution to the fine mass. Keywords: Particulate Matter, Reconstructed mass, Refuse burning, PMF, Receptor model, Composite Variables

Identifying sources and variations of organic matter in an urban river in Beijing, China using stable isotope analysis

Urban river ecosystem has been greatly altered by human activities, especially the input and transformation of allochthonous organic matter (OM) in urban river. Understanding of spatial and temporal variation of OM sources is critical to urban river management. Compared to previous studies, this study mainly focused on the spatial-temporal variations of OM sources in North Canal, an urban river in Beijing. Carbon stable isotopic (δ13C), nitrogen stable isotopic (δ15N), and isotopic multivariate mixture models were used to assess OM sources and their relative contribution. The result showed that autochthonous OM (macrophytes 68%, phytoplankton 16%) was dominant for suspended particulates, while allochthonous OM (C4 plants: 61%–76%; terrestrial soil: 36%–16%) was predominant in benthic fine particulates sediment. The composition of OM sources in suspended particulates and sediment showed a similar spatial pattern. Aquatic macrophytes were the main OM sources in upstream reaches, while terrestrial soil and sewage were the primary OM sources in midstream and downstream. Moreover, aquatic macrophytes and phytoplankton OM were the primary OM sources of main stream, whereas terrestrial soil and sewage were the main OM sources of tributaries. In addition, OM sources composition showed seasonal variations, and the terrestrial erosion caused by rainfall was the crucial factor for various OM sources in different seasons. In wet season, terrestrial soil erosion (24%–56%) and C4 plants (2%–28%) were primary sources of sedimentary OM, while macrophytes (32%–58%) and sewage (10%–42%) were the dominant OM sources in dry season. This study illuminated the effect of the human activities and rainfall on the sources of organic matter in North Canal. The control of sewage effluents and terrestrial soil erosion may be the best way to manage OM in North Canal.