Environmental science and pollution research international, 2018
Polychlorinated biphenyls (PCBs) can be used as chemical sentinels for the assessment of anthropo... more Polychlorinated biphenyls (PCBs) can be used as chemical sentinels for the assessment of anthropogenic influences on Arctic environmental change. We present an overview of studies on PCBs in the Arctic and combine these with the findings from ArcRisk-a major European Union-funded project aimed at examining the effects of climate change on the transport of contaminants to and their behaviour of in the Arctic-to provide a case study on the behaviour and impact of PCBs over time in the Arctic. PCBs in the Arctic have shown declining trends in the environment over the last few decades. Atmospheric long-range transport from secondary and primary sources is the major input of PCBs to the Arctic region. Modelling of the atmospheric PCB composition and behaviour showed some increases in environmental concentrations in a warmer Arctic, but the general decline in PCB levels is still the most prominent feature. 'Within-Arctic' processing of PCBs will be affected by climate change-relat...
Multi-year monitoring data for PCBs in abiotic media and biota collected from the Baltic region w... more Multi-year monitoring data for PCBs in abiotic media and biota collected from the Baltic region were compiled into a database and analyzed using the equilibrium lipid partitioning (ELP) approach to study temporal trends as well as to investigate food web biomagnification. Statistically significant reductions in ELP concentrations between 1987 and 2001 were observed in guillemots, air, and some fish species and a general, but not always statistically significant decline in concentrations was observed throughout the Baltic ecosystem. Estimated clearance half-lives ranged from 2.7-10.7 years. The database contained concentrations for a range of different Baltic species, which comprise a well-known Baltic food web. It was possible to derive the trophic position of the species in this food web and relate them to ELP concentrations. A significant positive correlation between ELP concentrations and trophic position was obtained. Estimated food web magnification factors ranged between 1.9 a...
A dynamic combined fate and food web model was developed to estimate the food web transfer of che... more A dynamic combined fate and food web model was developed to estimate the food web transfer of chemicals in small aquatic ecosystems (i.e. ponds). A novel feature of the modeling approach is that aquatic macrophytes (submerged aquatic vegetation) were included in the fate model and were also a food item in the food web model. The paper aims to investigate whether macrophytes are effective at mitigating chemical exposure and to compare the modeling approach developed here with previous modeling approaches recommended in the European Union (EU) guideline for risk assessment of pesticides. The model was used to estimate bioaccumulation of three hypothetical chemicals of varying hydrophobicity in a pond food web comprising 11 species. Three different macrophyte biomass densities were simulated in the model experiments to determine the influence of macrophytes on fate and bioaccumulation. Macrophytes were shown to have a significant effect on the fate and food web transfer of highly hydrophobic compounds with log K OW N = 5. Modeled peak concentrations in biota were highest for the scenarios with the lowest macrophyte biomass density. The distribution and food web transfer of the hypothetical compound with the lowest hydrophobicity (log K OW = 3) was not affected by the inclusion of aquatic macrophytes in the pond environment. For the three different hypothetical chemicals and at all macrophyte biomass densities, the maximum predicted concentrations in the top predator in the food web model were at least one order of magnitude lower than the values estimated using methods suggested in EU guidelines. The EU guideline thus provides a highly conservative estimate of risk. In our opinion, and subject to further model evaluation, a realistic assessment of dynamic food web transfer and risk can be obtained using the model presented here.
Mercury (Hg) and 13 other trace elements (Al, Ti, V, Cr, Fe, Mn, Co, Ni, Cu, Zn, As, Cd, and Pb) ... more Mercury (Hg) and 13 other trace elements (Al, Ti, V, Cr, Fe, Mn, Co, Ni, Cu, Zn, As, Cd, and Pb) were measured in phytoplankton, zooplankton, mysis and herring in order to examine the trophodynamics in a well-studied pelagic food chain in the Baltic Sea. The fractionation of nitrogen isotopes (δ 15 N) was used to evaluate food web structure and to estimate the extent of trophic biomagnification of the various trace elements. Trophic magnification factors (TMFs) for each trace element were determined from the slope of the regression between trace element concentrations and δ 15 N. Calculated TMFs showed fundamental differences in the trophodynamics of the trace elements in the pelagic food chain studied. Concentrations of Al, Fe, Ni, Zn, Pb and Cd showed statistically significant decreases (TMF < 1) with increasing trophic levels and thus these trace elements tropically dilute or biodilute in this Baltic food chain. Cu, As, Cr, Mn, V, Ti and Co showed no significant relationships with trophic levels. Hg was unique among the trace elements studied in demonstrating a statistically significant increase (TMF > 1) in concentration with trophic level i.e. Hg biomagnifies in this Baltic food chain. The estimated TMF for Hg in this food chain was comparable to TMFs observed elsewhere for diverse food chains and locations.
The bioaccumulation behaviour of PCB congeners in a Baltic food web is studied using a novel mech... more The bioaccumulation behaviour of PCB congeners in a Baltic food web is studied using a novel mechanistic model.
e n v i r o n m e n t a l s c i e n c e & p o l i c y 5 0 ( 2 0 1 5 ) 2 0 0 -2 1 3 a r t i c l e ... more e n v i r o n m e n t a l s c i e n c e & p o l i c y 5 0 ( 2 0 1 5 ) 2 0 0 -2 1 3 a r t i c l e i n f o Keywords: Contaminant cycling Climate change Human health effects POPs Mercury The Arctic population a b s t r a c t Results of the EU ArcRisk project on human health impacts in the Arctic owing to climateinduced changes in contaminant cycling are summarized in the context of their policy
The Science of the total environment, Jan 24, 2015
Alternative plasticizers to phthalate esters have been used for over a decade, but data regarding... more Alternative plasticizers to phthalate esters have been used for over a decade, but data regarding emissions, human exposure and health effects are limited. Here we review 20 alternative plasticizers in current use and their human exposure, hazard and risk. Physicochemical properties are collated for these diverse alternatives and log KOW values range over 15 orders of magnitude and log KAW and log KOA values over about 9 orders of magnitude. Most substances are hydrophobic with low volatility and are produced in high volumes for use in multiple applications. There is an increasing trend in the total use of alternative plasticizers in Sweden compared to common phthalate esters in the last 10years, especially for DINCH. Evaluative indoor fate modeling reveals that most alternatives are distributed to vertical surfaces (e.g. walls or ceilings). Only TXIB and GTA are predicted to be predominantly distributed to indoor air. Human exposure data are lacking and clear evidence for human exp...
This chapter describes the partitioning properties of organofluorine compounds in the environment... more This chapter describes the partitioning properties of organofluorine compounds in the environment. Partitioning in the air-water-octanol system is discussed using these pure substances as surrogates for real environmental systems consisting of air, water, natural organic matter and lipids. It is shown that the substitution of fluorine for hydrogen in alkanes, aromatics and carboxylic acids causes significant changes in properties such as vapor pressure, aqueous solubility, octanol-water partition coefficient and acid dissociation constant. These changes are quite different in magnitude from the corresponding changes caused by other better-studied halogens, namely chlorine and bromine. Perfluorinated substances have unique properties imparted by their minimal intermolecular interactions. The environmental implications of these properties are illustrated using simple multimedia partitioning models showing that organofluorine compounds behave quite differently than organochlorine analogs and more closely resemble the corresponding non-halogenated compounds.
To date, no harmonized guidance is available in the EU to estimate the emission of pesticides int... more To date, no harmonized guidance is available in the EU to estimate the emission of pesticides into air (excluding spray drift) and to quantify their atmospheric transport, transformation and deposition outside the treated field. The EU-Commission established ...
This paper describes (1) a ®eld experiment in which the air±soil exchanges of a range of polychlo... more This paper describes (1) a ®eld experiment in which the air±soil exchanges of a range of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) were measured and (2) the use of the fugacity quotient concept to provide information on the equilibrium partitioning of PCBs, PAHs and polychlorinated dibenzo-p-dioxins (PCDDs) between the air and soil in the UK. In the ®eld experiment aluminium foil trays containing thin layers ($5 mm) of spiked and unspiked soil were placed under custom-built shelters at a meteorological station and exposed to outdoor air for periods of up to 9 months (281 days). Soil and air samples were taken periodically throughout the 9-month period and analysed for PCBs and PAHs. The results from the experiment showed that the PCBs and PAHs in the soils were moving towards equilibrium partitioning conditions. Statisitically signi®cant losses of the majority of PCB/PAH compounds occurred in the spiked soils. Volatilisation was hypothesised to be the dominant loss mechanism. The PCBs in the unspiked soils were close to equilibrium with the air at the start of the experiment and there was, therefore, little change in their concentrations during the 9 months of exposure. For the PAHs there was also only a small change in the concentrations in the unspiked soils during the experiment, although there was a statistically signi®cant loss of acenaphthene, uorene and phenanthrene. Soil/air fugacity quotients were calculated using the air and soil concentrations measured in the ®eld experiment and also using our database of UK air and soil survey data. The calculated soil/air fugacity quotients, together with the ®ndings of the ®eld experiment, indicate that the soil and air are close to equilibrium for PCBs. However, this study provides evidence that the soil may now be a source of some lighter weight PAHs to the atmosphere, whereas it appears to be still acting as a long-term sink for the heavier weight PAHs and the PCDDs. #
Archived (1951–1974) and contemporary (1993) surface soil samples collected from the same 46 loca... more Archived (1951–1974) and contemporary (1993) surface soil samples collected from the same 46 locations widely distributed over the UK have been analyzed for 12 polynuclear aromatic hydrocarbons (PAHs). Contemporary soils were analyzed wet, ensuring that contamination, losses or alteration of PAHs in the samples was minimal. Archived soils had been air-dried prior to storage. The ΣPAH concentration of the contemporary
A laboratory experiment was carried out to measure volatilisation fluxes of polychlorinated biphe... more A laboratory experiment was carried out to measure volatilisation fluxes of polychlorinated biphenyls (PCBs) from sewage sludge-amended soils. The most commonly practised methods of applying sludge to agricultural land in the UK, namely, surface application, ploughing in to soil and subsurface injection, were simulated inside glass experimental chambers using an anaerobically digested sludge and a sandy loam soil. Humidified air
The Science of the total environment, Jan 15, 2015
Raw and treated landfill leachate samples were collected from 5 municipal landfill sites in China... more Raw and treated landfill leachate samples were collected from 5 municipal landfill sites in China to measure the concentrations and contamination profile of perfluoroalkyl acids (PFAAs) in leachate during different steps of treatment. The total concentration of PFAAs (∑PFAAs) ranged from 7280 to 292,000ngL(-1) in raw leachate and from 98.4 to 282,000ngL(-1) in treated leachate. The dominant compounds measured were PFOA (mean contribution 28.8% and 36.8% in raw and treated leachate, respectively) and PFBS (26.1% and 40.8% in raw and treated leachate, respectively). A calculation of mass flows during the leachate treatment processes showed that the fate of individual PFAAs was substance and treatment-specific. The Chinese national leakage of ∑PFAAs to groundwater from landfill leachate was estimated to be 3110kgyear(-1), which is a significant environmental release that is potentially threatening the sustainable use of groundwater as a drinking water source.
. Modeled and measured PFOS concentration in serum for women using the adjusted G mbl (12.2 mL/kg... more . Modeled and measured PFOS concentration in serum for women using the adjusted G mbl (12.2 mL/kg-bw/year) and Wong et al., 2 G mbl (6.1 mL/kg-bw/year).
Previous work has concluded that the sources of dioxins to the Baltic Sea are dominated by atmosp... more Previous work has concluded that the sources of dioxins to the Baltic Sea are dominated by atmospheric deposition. Here, we investigate whether current emission estimates can explain Baltic air levels and deposition fluxes of four selected 2,3,7,8-substituted PCDD/F congeners using an atmospheric modeling approach. The EMEP (European Monitoring and Evaluation Programme) database of emissions for dioxins was used to provide inputs to the selected model (MSCE-POP model) and model predicted levels were compared with measurements of dioxins in air and deposition fluxes at three monitoring stations in Sweden. The model underestimated air concentrations between a factor of 5 and 30, with the level of agreement depending on congener, monitoring station and, importantly, with the compass sector from which the contaminated air mass had arrived. Additional model simulations were undertaken in which emissions were enlarged in some selected areas to optimize agreement between model predictions and measurements. A novel emission adjustment approach is used in an attempt to identify source regions where emissions were in error. The emission adjustment approach improved the agreement between model predictions and measurements for 60% of the measurements within a factor of 3 of model predicted concentrations. However, the agreement was still relatively poor when air masses originated from the SSE and SSW. The model adjustment procedure gives an indication of the magnitude of error in exiting emission estimates, but due to the poor quality of existing emission databases and few quality air monitoring data it is not currently possible to use the emission adjustment approach to accurately identify source regions of error. The approach presented here is promising, however, and could be applied to other substances where better emission and monitoring data are available.
Environmental science and pollution research international, 2018
Polychlorinated biphenyls (PCBs) can be used as chemical sentinels for the assessment of anthropo... more Polychlorinated biphenyls (PCBs) can be used as chemical sentinels for the assessment of anthropogenic influences on Arctic environmental change. We present an overview of studies on PCBs in the Arctic and combine these with the findings from ArcRisk-a major European Union-funded project aimed at examining the effects of climate change on the transport of contaminants to and their behaviour of in the Arctic-to provide a case study on the behaviour and impact of PCBs over time in the Arctic. PCBs in the Arctic have shown declining trends in the environment over the last few decades. Atmospheric long-range transport from secondary and primary sources is the major input of PCBs to the Arctic region. Modelling of the atmospheric PCB composition and behaviour showed some increases in environmental concentrations in a warmer Arctic, but the general decline in PCB levels is still the most prominent feature. 'Within-Arctic' processing of PCBs will be affected by climate change-relat...
Multi-year monitoring data for PCBs in abiotic media and biota collected from the Baltic region w... more Multi-year monitoring data for PCBs in abiotic media and biota collected from the Baltic region were compiled into a database and analyzed using the equilibrium lipid partitioning (ELP) approach to study temporal trends as well as to investigate food web biomagnification. Statistically significant reductions in ELP concentrations between 1987 and 2001 were observed in guillemots, air, and some fish species and a general, but not always statistically significant decline in concentrations was observed throughout the Baltic ecosystem. Estimated clearance half-lives ranged from 2.7-10.7 years. The database contained concentrations for a range of different Baltic species, which comprise a well-known Baltic food web. It was possible to derive the trophic position of the species in this food web and relate them to ELP concentrations. A significant positive correlation between ELP concentrations and trophic position was obtained. Estimated food web magnification factors ranged between 1.9 a...
A dynamic combined fate and food web model was developed to estimate the food web transfer of che... more A dynamic combined fate and food web model was developed to estimate the food web transfer of chemicals in small aquatic ecosystems (i.e. ponds). A novel feature of the modeling approach is that aquatic macrophytes (submerged aquatic vegetation) were included in the fate model and were also a food item in the food web model. The paper aims to investigate whether macrophytes are effective at mitigating chemical exposure and to compare the modeling approach developed here with previous modeling approaches recommended in the European Union (EU) guideline for risk assessment of pesticides. The model was used to estimate bioaccumulation of three hypothetical chemicals of varying hydrophobicity in a pond food web comprising 11 species. Three different macrophyte biomass densities were simulated in the model experiments to determine the influence of macrophytes on fate and bioaccumulation. Macrophytes were shown to have a significant effect on the fate and food web transfer of highly hydrophobic compounds with log K OW N = 5. Modeled peak concentrations in biota were highest for the scenarios with the lowest macrophyte biomass density. The distribution and food web transfer of the hypothetical compound with the lowest hydrophobicity (log K OW = 3) was not affected by the inclusion of aquatic macrophytes in the pond environment. For the three different hypothetical chemicals and at all macrophyte biomass densities, the maximum predicted concentrations in the top predator in the food web model were at least one order of magnitude lower than the values estimated using methods suggested in EU guidelines. The EU guideline thus provides a highly conservative estimate of risk. In our opinion, and subject to further model evaluation, a realistic assessment of dynamic food web transfer and risk can be obtained using the model presented here.
Mercury (Hg) and 13 other trace elements (Al, Ti, V, Cr, Fe, Mn, Co, Ni, Cu, Zn, As, Cd, and Pb) ... more Mercury (Hg) and 13 other trace elements (Al, Ti, V, Cr, Fe, Mn, Co, Ni, Cu, Zn, As, Cd, and Pb) were measured in phytoplankton, zooplankton, mysis and herring in order to examine the trophodynamics in a well-studied pelagic food chain in the Baltic Sea. The fractionation of nitrogen isotopes (δ 15 N) was used to evaluate food web structure and to estimate the extent of trophic biomagnification of the various trace elements. Trophic magnification factors (TMFs) for each trace element were determined from the slope of the regression between trace element concentrations and δ 15 N. Calculated TMFs showed fundamental differences in the trophodynamics of the trace elements in the pelagic food chain studied. Concentrations of Al, Fe, Ni, Zn, Pb and Cd showed statistically significant decreases (TMF < 1) with increasing trophic levels and thus these trace elements tropically dilute or biodilute in this Baltic food chain. Cu, As, Cr, Mn, V, Ti and Co showed no significant relationships with trophic levels. Hg was unique among the trace elements studied in demonstrating a statistically significant increase (TMF > 1) in concentration with trophic level i.e. Hg biomagnifies in this Baltic food chain. The estimated TMF for Hg in this food chain was comparable to TMFs observed elsewhere for diverse food chains and locations.
The bioaccumulation behaviour of PCB congeners in a Baltic food web is studied using a novel mech... more The bioaccumulation behaviour of PCB congeners in a Baltic food web is studied using a novel mechanistic model.
e n v i r o n m e n t a l s c i e n c e & p o l i c y 5 0 ( 2 0 1 5 ) 2 0 0 -2 1 3 a r t i c l e ... more e n v i r o n m e n t a l s c i e n c e & p o l i c y 5 0 ( 2 0 1 5 ) 2 0 0 -2 1 3 a r t i c l e i n f o Keywords: Contaminant cycling Climate change Human health effects POPs Mercury The Arctic population a b s t r a c t Results of the EU ArcRisk project on human health impacts in the Arctic owing to climateinduced changes in contaminant cycling are summarized in the context of their policy
The Science of the total environment, Jan 24, 2015
Alternative plasticizers to phthalate esters have been used for over a decade, but data regarding... more Alternative plasticizers to phthalate esters have been used for over a decade, but data regarding emissions, human exposure and health effects are limited. Here we review 20 alternative plasticizers in current use and their human exposure, hazard and risk. Physicochemical properties are collated for these diverse alternatives and log KOW values range over 15 orders of magnitude and log KAW and log KOA values over about 9 orders of magnitude. Most substances are hydrophobic with low volatility and are produced in high volumes for use in multiple applications. There is an increasing trend in the total use of alternative plasticizers in Sweden compared to common phthalate esters in the last 10years, especially for DINCH. Evaluative indoor fate modeling reveals that most alternatives are distributed to vertical surfaces (e.g. walls or ceilings). Only TXIB and GTA are predicted to be predominantly distributed to indoor air. Human exposure data are lacking and clear evidence for human exp...
This chapter describes the partitioning properties of organofluorine compounds in the environment... more This chapter describes the partitioning properties of organofluorine compounds in the environment. Partitioning in the air-water-octanol system is discussed using these pure substances as surrogates for real environmental systems consisting of air, water, natural organic matter and lipids. It is shown that the substitution of fluorine for hydrogen in alkanes, aromatics and carboxylic acids causes significant changes in properties such as vapor pressure, aqueous solubility, octanol-water partition coefficient and acid dissociation constant. These changes are quite different in magnitude from the corresponding changes caused by other better-studied halogens, namely chlorine and bromine. Perfluorinated substances have unique properties imparted by their minimal intermolecular interactions. The environmental implications of these properties are illustrated using simple multimedia partitioning models showing that organofluorine compounds behave quite differently than organochlorine analogs and more closely resemble the corresponding non-halogenated compounds.
To date, no harmonized guidance is available in the EU to estimate the emission of pesticides int... more To date, no harmonized guidance is available in the EU to estimate the emission of pesticides into air (excluding spray drift) and to quantify their atmospheric transport, transformation and deposition outside the treated field. The EU-Commission established ...
This paper describes (1) a ®eld experiment in which the air±soil exchanges of a range of polychlo... more This paper describes (1) a ®eld experiment in which the air±soil exchanges of a range of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) were measured and (2) the use of the fugacity quotient concept to provide information on the equilibrium partitioning of PCBs, PAHs and polychlorinated dibenzo-p-dioxins (PCDDs) between the air and soil in the UK. In the ®eld experiment aluminium foil trays containing thin layers ($5 mm) of spiked and unspiked soil were placed under custom-built shelters at a meteorological station and exposed to outdoor air for periods of up to 9 months (281 days). Soil and air samples were taken periodically throughout the 9-month period and analysed for PCBs and PAHs. The results from the experiment showed that the PCBs and PAHs in the soils were moving towards equilibrium partitioning conditions. Statisitically signi®cant losses of the majority of PCB/PAH compounds occurred in the spiked soils. Volatilisation was hypothesised to be the dominant loss mechanism. The PCBs in the unspiked soils were close to equilibrium with the air at the start of the experiment and there was, therefore, little change in their concentrations during the 9 months of exposure. For the PAHs there was also only a small change in the concentrations in the unspiked soils during the experiment, although there was a statistically signi®cant loss of acenaphthene, uorene and phenanthrene. Soil/air fugacity quotients were calculated using the air and soil concentrations measured in the ®eld experiment and also using our database of UK air and soil survey data. The calculated soil/air fugacity quotients, together with the ®ndings of the ®eld experiment, indicate that the soil and air are close to equilibrium for PCBs. However, this study provides evidence that the soil may now be a source of some lighter weight PAHs to the atmosphere, whereas it appears to be still acting as a long-term sink for the heavier weight PAHs and the PCDDs. #
Archived (1951–1974) and contemporary (1993) surface soil samples collected from the same 46 loca... more Archived (1951–1974) and contemporary (1993) surface soil samples collected from the same 46 locations widely distributed over the UK have been analyzed for 12 polynuclear aromatic hydrocarbons (PAHs). Contemporary soils were analyzed wet, ensuring that contamination, losses or alteration of PAHs in the samples was minimal. Archived soils had been air-dried prior to storage. The ΣPAH concentration of the contemporary
A laboratory experiment was carried out to measure volatilisation fluxes of polychlorinated biphe... more A laboratory experiment was carried out to measure volatilisation fluxes of polychlorinated biphenyls (PCBs) from sewage sludge-amended soils. The most commonly practised methods of applying sludge to agricultural land in the UK, namely, surface application, ploughing in to soil and subsurface injection, were simulated inside glass experimental chambers using an anaerobically digested sludge and a sandy loam soil. Humidified air
The Science of the total environment, Jan 15, 2015
Raw and treated landfill leachate samples were collected from 5 municipal landfill sites in China... more Raw and treated landfill leachate samples were collected from 5 municipal landfill sites in China to measure the concentrations and contamination profile of perfluoroalkyl acids (PFAAs) in leachate during different steps of treatment. The total concentration of PFAAs (∑PFAAs) ranged from 7280 to 292,000ngL(-1) in raw leachate and from 98.4 to 282,000ngL(-1) in treated leachate. The dominant compounds measured were PFOA (mean contribution 28.8% and 36.8% in raw and treated leachate, respectively) and PFBS (26.1% and 40.8% in raw and treated leachate, respectively). A calculation of mass flows during the leachate treatment processes showed that the fate of individual PFAAs was substance and treatment-specific. The Chinese national leakage of ∑PFAAs to groundwater from landfill leachate was estimated to be 3110kgyear(-1), which is a significant environmental release that is potentially threatening the sustainable use of groundwater as a drinking water source.
. Modeled and measured PFOS concentration in serum for women using the adjusted G mbl (12.2 mL/kg... more . Modeled and measured PFOS concentration in serum for women using the adjusted G mbl (12.2 mL/kg-bw/year) and Wong et al., 2 G mbl (6.1 mL/kg-bw/year).
Previous work has concluded that the sources of dioxins to the Baltic Sea are dominated by atmosp... more Previous work has concluded that the sources of dioxins to the Baltic Sea are dominated by atmospheric deposition. Here, we investigate whether current emission estimates can explain Baltic air levels and deposition fluxes of four selected 2,3,7,8-substituted PCDD/F congeners using an atmospheric modeling approach. The EMEP (European Monitoring and Evaluation Programme) database of emissions for dioxins was used to provide inputs to the selected model (MSCE-POP model) and model predicted levels were compared with measurements of dioxins in air and deposition fluxes at three monitoring stations in Sweden. The model underestimated air concentrations between a factor of 5 and 30, with the level of agreement depending on congener, monitoring station and, importantly, with the compass sector from which the contaminated air mass had arrived. Additional model simulations were undertaken in which emissions were enlarged in some selected areas to optimize agreement between model predictions and measurements. A novel emission adjustment approach is used in an attempt to identify source regions where emissions were in error. The emission adjustment approach improved the agreement between model predictions and measurements for 60% of the measurements within a factor of 3 of model predicted concentrations. However, the agreement was still relatively poor when air masses originated from the SSE and SSW. The model adjustment procedure gives an indication of the magnitude of error in exiting emission estimates, but due to the poor quality of existing emission databases and few quality air monitoring data it is not currently possible to use the emission adjustment approach to accurately identify source regions of error. The approach presented here is promising, however, and could be applied to other substances where better emission and monitoring data are available.
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Papers by Ian Cousins