Source identification of atmospheric PCBs in Philadelphia/Camden using positive matrix factorization followed by the potential source contribution function

The concentrations of gas-phase polychlorinated biphenyls (PCBs) in the atmosphere of the Camden, NJ, USA are elevated by as much as 20 times over regional background. These high PCB levels are a concern because they lead to atmospheric deposition loadings of PCBs to the tidal Delaware River that exceed the entire total maximum daily load (TMDL). Two models were applied to the atmospheric PCB concentration data from Camden in an attempt to identify the PCB source types and regions. Positive matrix factorization (PMF) was used to identify the source types. Four factors were identified which are thought to represent sources such as volatilized Aroclors and particle-phase PCBs. The potential source contribution function (PSCF) model was then used to identify the geographic source regions by examining the origination points for air parcels that result in high PCB concentrations at the Camden receptor site. The PSCF model for ΣPCBs indicates PCB source regions throughout the Philadelphia–Camden metro area, including portions of both Pennsylvania and New Jersey. The PSCF plots for the resolved PMF factors suggest that factors 1–4 show fewer distinct source regions, indicating that their sources are diffuse and/or lie very close to the receptor site. The PSCF plots for factors 2 and 3 reveal very different source regions. Factor 2 primarily arises from the city of Philadelphia, whereas factor 3 originates in southern New Jersey and south of Philadelphia. This study demonstrates the utility of the combined PMF/PSCF approach in identifying atmospheric PCB source types and regions.     

A study on the potential sources of air pollutants observed at Tjörn,Sweden

The Potential Source Contribution Function (PSCF) receptor model combines both chemical and meteorological information. In this study, PSCF was employed to identify the potential source emission regions for aerosol compositions measured at Tjörn, Sweden (58.01 °N, 11.36 °E). PSCF was for the first time applied on a European scale. One hundred and fifty-two four-day air parcel backward trajectories were combined with concentrations of sixteen elements determined in 33 coarse and fine aerosol samples. The observations were made between February 17 and March 26, 1985. The modeling results of the heavy metals V, Pb, Zn, and As are presented and compared with available emission inventory data. A number of known industrialized regions in the former USSR and Europe are found of high potential to be the emission source areas. These areas are in good agreement with the known emission information. The PSCF maps of total sulfur, Non-Seasalt-Sulfur (N.S.S.) and chlorine are also presented. High potential regions in the Arctic area exist in the PSCF map for total sulfur wheres they do not occur in that for N.S.S.     

Long-range potential source contributions of episodic aerosol events to PM10 profile of a megacity

This paper evaluates possible long-range source contributions to the PM₁₀ profile of Istanbul, Turkey. A novel method for classifying PM₁₀ episodic events resulting from long-range transport, as opposed to local ones, was implemented. Hourly PM₁₀ mass concentrations from ten stations distributed throughout Istanbul during the year 2008 were used for this purpose. Hourly backward trajectories for the arrival of air masses to the center of Istanbul for the year 2008 were calculated using the HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) model. Significant episodes from these backward trajectories were selected and employed in Potential Source Contribution Function (PSCF) analysis to estimate the possible contribution of long-range PM₁₀ transport (LRPMT) to observed PM₁₀ concentrations. The PSCF results showed significant seasonal variations. Based on the results obtained, PM₁₀ concentrations observed in Istanbul during summer and autumn are not heavily affected by LRPMT. Mediterranean countries, especially those of the central part of northern Africa (northern Algeria and Libya) are the most significant potential PM₁₀ contributors to Istanbul's atmosphere during springtime. During winter, Balkan countries, including the Aegean part of Turkey, Greece, Bulgaria, Serbia, and Croatia, as well as northern Italy, eastern France, southern Germany, Austria and the eastern part of Russia, were the most important LRPMT source regions for high PSCF values.     

Development and application of three-dimensional potential source contribution function (3D-PSCF)

A potential source contribution function (PSCF) can indicate the source areas of high air pollutant concentrations using backward trajectories. However, the conventional two-dimensional PSCF (2D-PSCF) cannot consider the emission and transport height of air pollutants. That missing information might be critical because injection height varies depending on the source type, such as with biomass burning. We developed a simple algorithm to account for the height of trajectories with high concentrations and combined it with the conventional PSCF to devise 3D-PSCF. We demonstrate the applicability of the 3D-PSCF by applying it to particulate PAH data collected from September 2006 to August 2007 in Seoul. We found variation in the results from 3D-PSCF with threshold heights from 3,000 to 1,500 m. Applying 2,000 m as the threshold height in the PSCF calculation most clearly determined the possible source areas of air pollutants from biomass fuel burning that were affecting the air quality in Seoul.     

Estimation of source locations of total gaseous mercury measured in New York State using trajectory-based models

Ambient gaseous phase mercury concentrations (TGM) were measured at three locations in NY State including Potsdam, Stockton, and Sterling from May 2000 to March 2005. Using these data, three hybrid receptor models incorporating backward trajectories were used to identify source areas for TGM. The models used were potential source contribution function (PSCF), residence time weighted concentration (RTWC), and simplified quantitative transport bias analysis (SQTBA). Each model was applied using multi-site measurements to resolve the locations of important mercury sources for New York State.PSCF results showed that southeastern New York, Ohio, Indiana, Tennessee, Louisiana, and Virginia were important TGM source areas for these sites. RTWC identified Canadian sources including the metal production facilities in Ontario and Quebec, but US regional sources including the Ohio River Valley were also resolved. Sources in southeastern NY, Massachusetts, western Pennsylvania, Indiana, and northern Illinois were identified to be significant by SQTBA. The three modeling results were combined to locate the most important probable source locations, and those are Ohio, Indiana, Illinois, and Wisconsin. The Atlantic Ocean was suggested to be a possible source as well.     

Validation of trajectory statistical methods

A number of works have been trying to validate various trajectory statistical methods (TSMs), mostly through subjective comparison with known sources. Here in a more comprehensive and quantitative approach three trajectory statistical methods (potential source contribution function (PSCF), concentration field method (CF), and redistributed concentration field method (RCF)) were subjected to two validation approaches: validation with virtual and real sources under idealised conditions, where the effects of dispersion and removal of the trace substance are excluded, and comparisons with the EMEP SO₂ emission inventory under realistic conditions.The best performance was achieved in an idealised situation with about 78% common spatial variance between the EMEP emission inventory and the trajectory statistical reconstruction of the EMEP emission inventory with the RCF method, whereas the real world experiments for SO₂ on an European scale resulted in a much lower performance with 33% common spatial variance between the EMEP SO₂ emission inventory and the trajectory statistical reconstruction with the PSCF method.The experiments suggest that the limitation of the accuracy and spatial range of TSMs are rooted in the simplified transport process described just by trajectory paths. If one links these limitations with the concept of the mean residence time of the considered trace substance, a temporal and spatial scope can be deduced, within which the effect of the simplification of the transport process is restricted and useful information can be expected from TSMs. The lower values of the mean residence time for SO₂ range from 9 to 17 h, which were deduced from the decay approach, where an exponential decay, respectively, removal of SO₂ was built into the trajectory statistical procedure. The values derived from the optimum real world validation experiment place the upper range of the mean residence time to about 60 h or 2.5 days. Both figures are within the range of mean residence times for SO₂ cited in literature. Through the validation experiments of this work the rule of thumb, not to trust TSMs beyond the mean residence time of the substance, has become palpable. Nevertheless TSMs and related methods are computationally fast procedures, which deliver first hints on potential source areas, if applied within the frame of the mean residence time of the considered substance.     

Source identification and trends in concentrations of gaseous and fine particulate principal species in Seoul, South Korea

Ambient measurements were made using two sets of annular denuder system during the four seasons (April 2001 to February 2002) and were then compared with the results during the period of 1996-1997 to estimate the trends and seasonal variations in concentrations of gaseous and fine particulate matter (PM2.5) principal species. Annual averages of gaseous HNO3 and NH3 increased by 11% and 6%, respectively, compared with those of the previous study, whereas HONO and SO2 decreased by 11% and 136%, respectively. The PM2.5 concentration decreased by -17%, 35% for SO4(2-), and 29% for NH4+, whereas NO3- increased by 21%. Organic carbon (OC) and elemental carbon (EC) were 12.8 and 5.98 microg/m(-3), accounting for -26 and 12% of PM2.5 concentration, respectively. The species studied accounted for 84% of PM2.5 concentration, ranging from 76% in winter to 97% in summer. Potential source contribution function (PSCF) analysis was used to identify possible source areas affecting air pollution levels at a receptor site in Seoul. High possible source areas in concentrations of PM2.5, NO3-, SO4(2-), NH4+, and K+ were coastal cities of Liaoning province (possibly emissions from oil-fired boilers on ocean liners and fishing vessels and industrial emissions), inland areas of Heibei/Shandong provinces (the highest density areas of agricultural production and population) in China, and typical port cities (Mokpo, Yeosu, and Busan) of South Korea. In the PSCF map for OC, high possible source areas were also coastal cities of Liaoning province and inland areas of Heibei/Shandong provinces in China. In contrast, high possible source areas of EC were highlighted in the south of the Yellow Sea, indicating possible emissions from oil-fired boilers on large ships between South Korea and Southeast Asia. In summary, the PSCF results may suggest that air pollution levels in Seoul are affected considerably by long-range transport from external areas, such as the coastal zone in China and other cities in South Korea, as well as Seoul itself.     

Transport patterns and potential sources of total gaseous mercury measured in Canadian high Arctic in 1995

Trajectory cluster analysis and the potential source contribution function (PSCF) model have been used to investigate the source–receptor relationship for the total gaseous mercury (TGM) measured in the Canadian High Arctic (Alert, 82.5°N, 62.3°W) during 1995. Cluster analysis of 10-day back-trajectories in 1995 shows that the synoptic flows arriving at Alert are dominated by the air masses from the north. Long-range transport only occurs in the cold seasons while summertime flows tend to circulate in the Arctic Ocean. The potential source regions identified by the PSCF modeling include Eurasia and populated areas in the North America and Europe. Based on the modeling results, it is suggested that the elevated TGM concentrations found in the Arctic summer should be of geological origins, mainly from the evasion of volatile Hg⁰ from earth's surfaces. In the autumn and winter, mercury is transported to the receptor site from remote anthropogenic sources. The preferred sources of TGM in the spring cannot be clearly determined due to the Arctic springtime mercury depletion, which significantly reduces the number of trajectories contributing to PSCF values. Using TGM data of higher temporal resolution improves the sensitivity of the PSCF modeling results.     

Estimation of source apportionment and potential source locations of PM2.5 at a west coastal IMPROVE site

Particle composition data for PM_2.5 samples collected at Kalmiopsis Interagency Monitoring of Protected Visual Environments (IMPROVE) site in southwestern Oregon from March 2000 to May 2004 were analyzed to provide source identification and apportionment. A total of 493 samples were collected and 32 species were analyzed by particle induced X-ray emission, proton elastic scattering analysis, photon-induced X-ray fluorescence, ion chromatography, and thermal optical reflectance methods. Positive matrix factorization (PMF) was used to estimate the source profiles and their mass contributions. The PMF modeling identified nine sources. In the Kalmiopsis site, the average mass was apportioned to wood/field burning (38.4%), secondary sulfate (26.9%), airborne soil including Asian dust (8.6 %), secondary nitrate (7.6%), fresh sea salt (5.8%), OP-rich sulfate (4.9%), aged sea salt (4.5 %), gasoline vehicle (1.9%), and diesel emission (1.4%). The potential source contribution function (PSCF) was then used to help identify likely locations of the regional sources of pollution. The PSCF map for wood/field burning indicates there is a major potential source area in the Siskiyou County and eastern Oregon. The potential source locations for secondary sulfate are found in western Washington, northwestern Oregon, and the near shore Pacific Ocean where there are extensive shipping lanes. It was not possible to extract a profile directly attributable to ship emissions, but indications of their influence are seen in the secondary sulfate and aged sea salt compositions.     

Source Identification and Trends in Concentrations of Gaseous and Fine Particulate Principal Species in Seoul,South Korea

Abstract

Ambient measurements were made using two sets of annular denuder system during the four seasons (April 2001 to February 2002) and were then compared with the results during the period of 1996–1997 to estimate the trends and seasonal variations in concentrations of gaseous and fine particulate matter (PM_2.5) principal species. Annual averages of gaseous HNO₃ and NH₃ increased by 11% and 6%, respectively, compared with those of the previous study, whereas HONO and SO₂ decreased by 11% and 136%, respectively. The PM_2.5 concentration decreased by ～17%, 35% for SO₄ ^2?, and 29% for NH₄ ⁺, whereas NO₃ ^? increased by 21%. Organic carbon (OC) and elemental carbon (EC) were 12.8 and 5.98 μg/m^-3, accounting for ～26 and 12% of PM_2.5 concentration, respectively. The species studied accounted for 84% of PM_2.5 concentration, ranging from 76% in winter to 97% in summer.

Potential source contribution function (PSCF) analysis was used to identify possible source areas affecting air pollution levels at a receptor site in Seoul. High possible source areas in concentrations of PM_2.5, NO₃ ^?, SO₄ ^2?, NH₄ ⁺, and K⁺ were coastal cities of Liaoning province (possibly emissions from oil-fired boilers on ocean liners and fishing vessels and industrial emissions), inland areas of Heibei/Shandong provinces (the highest density areas of agricultural production and population) in China, and typical port cities (Mokpo, Yeosu, and Busan) of South Korea. In the PSCF map for OC, high possible source areas were also coastal cities of Liaoning province and inland areas of Heibei/Shandong provinces in China. In contrast, high possible source areas of EC were highlighted in the south of the Yellow Sea, indicating possible emissions from oil-fired boilers on large ships between South Korea and Southeast Asia. In summary, the PSCF results may suggest that air pollution levels in Seoul are affected considerably by long-range transport from external areas, such as the coastal zone in China and other cities in South Korea, as well as Seoul itself.     

基于遗传算法的大气污染总量控制新方法

提出一种利用遗传算法进行大气污染总量控制的新方法,并以柳州市SO2总量控制为例说明这种方法的具体运用.遗传算法具备自适应全局搜索寻优特点,从控制点浓度推算源强分布,该源强分布满足总量控制的根本要求.该方法的具体实现是:将区域内各污染源的排放量编码为染色体,让染色体群体在模拟的进化环境下按生物进化规律进行优胜劣汰的自然选择,经过若干代的进化,最终得到的最优个体即代表最佳的源强分布.研究结果表明,这种方法是有效的和可行的.     

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.     

Critical loads for Finnish lakes: comparison of three steady-state models

Three simple steady-state water-chemistry models are used to calculate critical loads of sulfur for lakes in Finland. Because of the high concentrations of organic matter in Finnish lakes, the influence of organic anions on the calculation of critical loads has been given special attention. The first two methods are well known ion-balance methods which have been used in many previous lake-acidification studies. The third method, developed for this study, includes the numerical solution of equilibrium equations for organic anions, inorganic carbon species and inorganic monomeric aluminum. The original pH and aluminum concentration of the lakes are estimated with this model, and a method to estimate the original acid neutralizing capacity (ANC) by simulating a Gran-titration is also tested on the lake data. Uncertainty in the predictions is estimated by varying the most critical model parameters.     

The use of conditional probability functions and potential source contribution functions to identify source regions and advection pathways of hydrocarbon emissions in Houston,Texas

In this study, we demonstrate the utility of conditional probability functions (CPFs), potential source contribution functions (PSCFs), and hierarchical clustering analysis (HAC) to identify the source region and transport pathways of hydrocarbons measured at five photochemical assessment monitoring stations (PAMS) near the Houston Ship Channel from June to October 2003. In contrast to scatter plots, which only show the pair-wise correlation of species, commonality in CPF figures shows both correlation and information on the source region of the species in question. In this study, we use over 50 hourly volatile organic compound (VOC) concentrations and surface wind observations to show that VOCs with similar CPF patterns likely have common transport pathways. This was established with the multivariate technique, which uses the hierarchical clustering analysis to define clusters of VOCs having similar CPF patterns. This method revealed that alkenes, and in particular those with geometric isomers such as cis-/trans-2-butene and cis-/trans-2-pentene, have similar CPF patterns and hence, a common area of origin. The alkane isomers often show CPF patterns among themselves, and similarly, aromatic compounds often show similar patterns. We also show how calculated trajectory information can be used in the PSCF analysis to produce a graphic picture that identifies specific geographic areas associated with a given VOC (or other pollutant). The use of these techniques in the chemically and meteorologically complex environment of Houston, Texas, suggests its further utility in other areas with relatively simpler conditions.     

Source apportionment of fine particles utilizing partially speciated carbonaceous aerosol data at two rural locations in New York State

A source apportionment study was conducted at two rural locations, Potsdam and Stockton, to assess the in-state/out-of-state sources of PM_2.5 and Hg in New York State. At both locations, samples were collected between November 2002 and August 2005 and analyzed for fine PM mass and its chemical constituents. The measured chemical constituents included elements, cations, anions, organic and elemental carbon (OC and EC), black carbon (BC), and water-soluble short-chain (WSSC) organic acids. Positive matrix factorization (PMF) was applied to the measured concentrations and eight and seven factors were resolved at Potsdam and Stockton, respectively. Four factors were resolved in common between the two locations including secondary sulfate, secondary nitrate, secondary OC, and a crustal factor. The factor profiles of mixed industrial and motor vehicle factors resolved at Potsdam were different compared with the corresponding profiles for these factors at Stockton. A resuspended road salt factor was identified at Potsdam, while an aged sea salt factor was identified at Stockton. At Potsdam, a wood smoke factor was also resolved. Among the resolved factors, secondary sulfate was the highest contributor to the measured mass at both sites. Potential source contribution function (PSCF) analysis indicated the Ohio River Valley region as a common potential source region for this factor at both locations. For the secondary nitrate factor, at Potsdam PSCF analysis indicated the Midwestern US (NO_x emissions), and the US farm belt (ammonia emissions) as potential source regions, while at Stockton, the Midwestern US (power plant NO_x emissions) was indicated as a major potential source region.     

Identification of sources of pollutants in precipitation measured at the mid-Atlantic US coast using potential source contribution function (PSCF)

Potential source contribution function (PSCF) was employed to study the source receptor relationships for 14 chemical species (Mn, SO₄²⁻, Zn, Al, Fe, Cu, Cr, Ni, Cd, NO₃, NH₄⁺, K⁺, Mg²⁺,and Pb) found in precipitation collected at Lewes, Delaware. This study identified areas of the Eastern United States as possible emission source areas that could have contributed to the 14 element concentrations observed at Lewes. The identified regions in the Eastern United States generally coincide well with known emission source areas. The likely emission sources for these chemical species include oil- and coal-fired power plants, incinerators, motor vehicles, and iron and steel mills.     

Chemical characteristics and source apportionment of PM<Subscript>2.5</Subscript> using PCA/APCS,UNMIX, and PMF at an urban site of Delhi,India

The present study investigated the comprehensive chemical composition [organic carbon (OC), elemental carbon (EC), water-soluble inorganic ionic components (WSICs), and major & trace elements] of particulate matter (PM_2.5) and scrutinized their emission sources for urban region of Delhi. The 135 PM_2.5 samples were collected from January 2013 to December 2014 and analyzed for chemical constituents for source apportionment study. The average concentration of PM_2.5 was recorded as 121.9 ± 93.2 μg m^?3 (range 25.1–429.8 μg m^?3), whereas the total concentration of trace elements (Na, Ca, Mg, Al, S, Cl, K, Cr, Si, Ti, As, Br, Pb, Fe, Zn, and Mn) was accounted for ～17% of PM_2.5. Strong seasonal variation was observed in PM_2.5 mass concentration and its chemical composition with maxima during winter and minima during monsoon seasons. The chemical composition of the PM_2.5 was reconstructed using IMPROVE equation, which was observed to be in good agreement with the gravimetric mass. Source apportionment of PM_2.5 was carried out using the following three different receptor models: principal component analysis with absolute principal component scores (PCA/APCS), which identified five major sources; UNMIX which identified four major sources; and positive matrix factorization (PMF), which explored seven major sources. The applied models were able to identify the major sources contributing to the PM_2.5 and re-confirmed that secondary aerosols (SAs), soil/road dust (SD), vehicular emissions (VEs), biomass burning (BB), fossil fuel combustion (FFC), and industrial emission (IE) were dominant contributors to PM_2.5 in Delhi. The influences of local and regional sources were also explored using 5-day backward air mass trajectory analysis, cluster analysis, and potential source contribution function (PSCF). Cluster and PSCF results indicated that local as well as long-transported PM_2.5 from the north-west India and Pakistan were mostly pertinent.     

The aerosol at Barrow,Alaska: long-term trends and source locations

Aerosol data consisting of condensation nuclei (CN) counts, black carbon (BC) mass, aerosol light scattering (SC), and aerosol optical depth (AOD) measured at Barrow, Alaska from 1977 to 1994 have been analyzed by three-way positive matrix factorization (PMF3) by pooling all of the different data into one large three-way array. The PMF3 analysis identified four factors that indicate four different combinations of aerosol sources active throughout the year in Alaska. Two of the factors (F1, F2) represent Arctic haze. The first Arctic haze have factor F1 is dominant in January–February while the second factor F2 is dominant in March–April. They appear to be material that is generally ascribed to long-range transported anthropogenic particles. A lower ratio of condensation nuclei to scattering coefficient loadings is obtained for F2 indicating larger particles. Factor F3 is related to condensation nuclei. It has an annual cycle with two maxima, March and July–August indicating some involvement of marine biogenic sources. The fourth factor F4 represents the contribution to the stratospheric aerosol from the eruptions of El Chichon and Mt. Pinatubo. No significant long-term trend for F1 was detected while F2 shows a negative trend over the period from 1982 to 1994 but not over the whole measurement period. A positive trend of F3 over the whole period has been observed. This trend may be related to increased biogenic sulfur production caused by reductions in the sea-ice cover in the Arctic and/or an air temperature increase in the vicinity of Barrow. Potential source contribution function (PSCF) analysis showed that in winter and spring during 1989 to 1993 regions in Eurasia and North America are the sources of particles measured at barrow. In contrast to this, large areas in the North Pacific Ocean and the Arctic Ocean was contributed to observed high concentrations of CN in the summer season. Three-way positive matrix factorization was an effective method to extract time-series information contained in the measured quantities. PSCF was useful for the identification possible source areas and the potential pathways for the Barrow aerosol. The effects of long-distance transport, photochemical aerosol production, emissions from biogenic activities in the ocean, volcanic eruptions on the aerosol measurements made at Barrow were extracted using this combined methodology.     

Numerical calculation of flow and stack-gas concentration fluctuation around a cubical building

A numerical simulation model was developed to predict the instantaneous concentration fluctuation of a plume and applied to stack-gas diffusion around a cubical building. The flow field, including an instantaneous velocity component, was predicted using the large eddy simulation (LES) method in the developed numerical model. Then, the instantaneous concentration fluctuation was predicted using the obtained unsteady flow field. Concentration was calculated using the finite difference method, in which the LES is expanded for concentration, and the puff method, in which small volumes of the tracer gas are divided and combined according to the calculation mesh sizes. In order to avoid numerical viscous effects, a puff method and finite difference method were applied separately in the regions near and far from the stack-gas release point, respectively. Then, the flow field around a cubical building and the diffusion of stack-gas, emitted from an elevated point source at an upstream position of the building, were calculated using the model mentioned above. Numerical calculation results were compared with those obtained in wind tunnel experiments in which concentration fluctuation was measured using high-response flame ionization detectors. Although there were some discrepancies in the flow field between the calculated results and those of wind tunnel experiments, e.g., the calculated windward length of a cavity region behind the building, the calculated mean velocity and turbulent intensity showed good agreement with those of the wind tunnel experiments. Furthermore, the calculated concentration fluctuation showed good agreement with that in the wind tunnel, not only regarding the features of fluctuating concentration signals, but also statistic quantities, viz., mean concentration, fluctuation intensity and high-concentration values.     

Potential sources of atmospheric total gaseous mercury in the St. Lawrence River valley

The potential source contribution function (PSCF) has been used to study the source–receptor relationships for total gaseous mercury (TGM) found in air collected at two sites along the St. Lawrence River valley, namely at St. Anicet and Mingan. TGM concentrations have been measured with high time-resolution analysers (Tekran instrument). The source–receptor analyses have been applied with regards to the seasonality of TGM. Median TGM concentrations are significantly less (χ²: α=0.01) during the summertime than other periods at both sites. A total of 12 225 trajectory end-points for St. Anicet and 4480 trajectory end points for Mingan have been used to create potential source area maps. This study identifies preferred potential sources of TGM at St. Anicet during wintertime with strongest probability stretching from the Gulf of Mexico to the southern tip of Greenland. This pattern mimics, the North American anthropogenic Hg emission inventory. Furthermore, some Eurasian mercury air mass intrusions are suggested at Mingan during wintertime. The summertime period at Mingan points out some potential sources stretching from the american mid-west to the St. Lawrence River valley as well as areas around the southern tip of the Hudson Bay.