Quantifying Asian and biomass burning sources of mercury using the Hg/CO ratio in pollution plumes observed at the Mount Bachelor observatory

Total airborne mercury (TAM) and carbon monoxide (CO) were measured in 22 pollution transport “events” at Mt. Bachelor Observatory (MBO), USA (2.8 km asl) between March 2004 and September 2005. Submicron particulate scattering (${\sigma }_{\mathrm{sp}})$, ozone (${\mathrm{O}}_3)$, and nitrogen oxides (${\mathrm{NO}}_y)$ were also measured and enhancement ratios for each chemical and aerosol species with CO were calculated. Events were categorized based on their source regions, which were determined by a combination of back trajectories, satellite fire detections, chemical and aerosol enhancement ratios, and meteorology. The mean $\mathrm{\Delta }\mathrm{TAM}/\mathrm{\Delta }\mathrm{CO}$ values for each source region are: East Asian industrial ($0.0046\pm 0.0013\mathrm{ng}{\mathrm{m}}^{-3}{\mathrm{ppbv}}^{-1}$, $n=10$ events, 236 h), Pacific Northwest U.S. (PNW) biomass burning ($0.0013\pm 0.008\mathrm{ng}{\mathrm{m}}^{-3}{\mathrm{ppbv}}^{-1}$, $n=7$ events, 173 h), and Alaska biomass burning ($0.0014\pm 0.0006\mathrm{ng}{\mathrm{m}}^{-3}{\mathrm{ppbv}}^{-1}$, $n=3$ events, 96 h). The $\mathrm{\Delta }\mathrm{TAM}/\mathrm{\Delta }\mathrm{CO}$ means from Asian long-range transport (ALRT) and biomass burning events are combined with previous estimates of CO emissions from Chinese anthropogenic, global biomass burning, and global boreal biomass sources in order to estimate the emissions of gaseous elemental mercury (GEM) from these sources. The GEM emissions that we calculate here are: Chinese anthropogenic ($620\pm 180\mathrm{t}{\mathrm{y}}^{-1}$), global biomass burning $(670\pm 330\mathrm{t}{\mathrm{y}}^{-1})$, and global boreal biomass burning $(168\pm 75\mathrm{t}{\mathrm{y}}^{-1})$, with errors estimated from propagating the uncertainty in the mean enhancement ratios and CO emissions. A comparison of our results with published mercury (Hg) emissions inventories reveals that the Chinese GEM emissions from this study are higher by about a factor of two, while our estimate for global biomass burning is consistent with previous studies.     

Visual impact of plumes from power plants: A theoretical model

Theoretical relationships have been derived and transformed into a computer model to describe plume visual impact at various observer vantage points resulting from power plant boiler operation. Plume visual impact results from a reduction in visual range (visibility) and plume coloration. The model considers plume transport and diffusion, light scattering and absorption by aerosols and gases, and chemical transformation in the plume of nitric oxide to nitrogen dioxide, sulfur dioxide to sulfates, and nitrogen oxides to nitrates.The model is applied in a parametric study to explore the effect of emissions and environmental conditions on plume visual impact. The case selected is a hypothetical 1500 Mwe coal-fired power plant equipped with efficient particulate abatement equipment. The results establish that visual range is not significantly affected unless the observer is viewing along the plume axis or unless significant amounts of secondary particles are formed in the plume. Yellow-brown plume coloration is shown to result from the net production of nitrogen dioxide gas in the plume. The coloration is most apparent during stable and clear atmospheric conditions and effectively masked for elevated concentrations of background or plume aerosol.     

Transport and transformation of sulfur compounds over East Asia during the TRACE-P and ACE-Asia campaigns

On the basis of the recently estimated emission inventory for East Asia with a resolution of 1×1°, the transport and chemical transformation of sulfur compounds over East Asia during the period of 22 February through 4 May 2001 was investigated by using the Models-3 Community Multi-scale Air Quality (CMAQ) modeling system with meteorological fields calculated by the regional atmospheric modeling system (RAMS). For evaluating the model performance simulated concentrations of sulfur dioxide (SO₂) and aerosol sulfate (SO₄²⁻) were compared with the observations on the ground level at four remote sites in Japan and on board aircraft and vessel during the transport and chemical evolution over the Pacific and Asian Pacific regional aerosol characterization experiment field campaigns, and it was found that the model reproduces many of the important features in the observations, including horizontal and vertical gradients. The SO₂ and SO₄²⁻ concentrations show pronounced variations in time and space, with SO₂ and SO₄²⁻ behaving differently due to the interplay of chemical conversion, removal and transport processes. Analysis of model results shows that emission was the dominant term in regulating the SO₂ spatial distribution, while conversion of SO₂ to SO₄²⁻ in the gas phase and the aqueous phase and wet removal were the primary factors that controlled SO₄²⁻ amounts. The gas phase and the aqueous phase have the same importance in oxidizing SO₂, and about 42% sulfur compounds (25% in SO₂) emitted in the model domain was transported out, while about 57% (35% by wet removal processes) was deposited in the domain during the study period.     

A new Lagrangian particle model for the simulation of dense gas dispersion

A Lagrangian stochastic model (MicroSpray), able to simulate the airborne dispersion in complex terrain and in presence of obstacles, was modified to simulate the dispersion of dense gas clouds. This is accomplished by taking into account the following processes: negative buoyancy, gravity spreading and the particle's reflection at the bottom computational boundary. Elevated and ground level sources, continuous and instantaneous emissions, time varying sources, plumes with initial momentum (horizontal, vertical or oblique in any direction), plumes without initial momentum are considered. MicroSpray is part of the model system MSS, which also includes the diagnostic MicroSwift model for the reconstruction of the 3-D wind field in presence of obstacles and orography. To evaluate the MSS ability to simulate the dispersion of heavy gases, its simulation performances are compared in detail to two field experiments (Thorney Island and Kit Fox) and to a chlorine railway accident (Macdona). Then, a comprehensive analysis considering several experiments of the Modelers Data Archive is presented. The statistical analysis on the overall available data reveals that the performance of the new MicroSpray version for dense gas releases is generally reliable. For instance, the agreement between concentration predictions and observations is within a factor of two in the 72% up to 99% of the occurrences for the case studies considered. The values of other performance measures, such as correlation coefficient, geometric mean bias and geometric variance, mostly set in the ranges indicated as good-model performances in the specialized literature.     

Concentration field and turbulent fluxes during the mixing of two buoyant plumes

In this work an experimental study of mixing of two identical plumes, carried out in a turbulent neutral boundary layer generated in a wind tunnel, is presented. Measurements have been performed with fast flame ionisation detectors (FFIDs) and a two-component Laser-Doppler Anemometer system. Results allow the study of both the average and the fluctuating concentration field, including the turbulent vertical and longitudinal mass fluxes, in single plumes and during the interaction of two identical plumes. This information gives insight into the details of the mixing phase of the two plumes. Results of trajectories and additional rise (due to plume interactions) have been compared with previous measurements carried out in laminar cross-flows, showing similar behaviour. Concentration distributions in plume cross-sections in turbulent cross-flows differ from those measured in laminar cross-flows. Average vertical and longitudinal velocity measurements into the plume core show the strength of the shielding effect of the upwind plume and some details of interaction between the counter-rotating vortex pairs (CVPs). For large values of the alignment angle φ, between the line joining the stacks and the cross-flow, an average negative vertical velocity is measured in the middle of the plume even if its centre of mass is rising. This downward velocity is induced by the slow interaction of the CVPs and generates a vertical stretching of the plume and negative rise enhancement. Vertical turbulent fluxes change sign on the plume centreline and are of opposite sign with respect to the longitudinal turbulent fluxes. Results indicate a good linearity between vertical turbulent fluxes and concentration gradients, with different proportionality for the top and bottom parts of the plume (especially in the near field) indicating that dispersion could be described by a gradient-transfer model.     

环境激素污染研究进展

综述了国内外环境激素的研究进展．介绍了环境激素的特性、种类,重点阐述了环境激素的毒害途径和作用机理;指出环境激素物质的鉴定、激素物质环境容量的确定以及在环境中激素迁移、转化、积累等问题。从环境激素对人类的健康,尤其是对生殖健康的危害,提出了防治环境激素污染的措施。     

A new Lagrangian stochastic model for the gravity-slumping/spreading motion of a dense gas

A new dispersion model for dense gas which is released into the atmosphere on the flat terrain is constructed within the Lagrangian framework. Using the hydrostatic assumption for pressure distribution within cloud due to density variation, slumping motion is successfully incorporated into the Lagrangian model with entrainment effect naturally considered. Turbulence suppression due to stable stratification within cloud is also taken into consideration in the model formulation. Various results including time variant and maximum concentration predictions by the proposed model are compared with the available measured data in the experiment conducted in Thorney Island in 1984 with good agreement.     

A dynamic model of optimal reduction of marine oil pollution

This paper proposes a system of dynamic models to describe the interactive behaviour of different agents (polluters, inspectors, and a principal pollution control agency) involved in the processes of marine oil pollution and of its prevention and purification, under some realistic assumptions. In particular, short- and long-term economic responses of polluters to monitoring efforts, as well as possible collusions between polluters and inspectors, are taken into account. A numerical example is considered using the results of Deissenberg et al., (2001a), which show the existence of optimal fines and inspector wage rates that minimise (along with other variables) a simple and visual 'social damage' criterion.     

Simulation of aerosol radiative properties with the ORISAM-RAD model during a pollution event (ESCOMPTE 2001)

The aim of this study is to present the organic and inorganic spectral aerosol module-radiative (ORISAM-RAD) module, allowing the 3D distribution of aerosol radiative properties (aerosol optical depth, single scattering albedo and asymmetry parameter) from the ORISAM module. In this work, we test ORISAM-RAD for one selected day (24th June) during the ESCOMPTE (expérience sur site pour contraindre les modèles de pollution atmosphérique et de transport d’emissions) experiment for an urban/industrial aerosol type. The particle radiative properties obtained from in situ and AERONET observations are used to validate our simulations. In a first time, simulations obtained from ORISAM-RAD indicate high aerosol optical depth (AOD)0.50–0.70±0.02 (at 440 nm) in the aerosol pollution plume, slightly lower (10–20%) than AERONET retrievals. In a second time, simulations of the single scattering albedo (ω_o) have been found to well reproduce the high spatial heterogeneities observed over this domain. Concerning the asymmetry parameter (g), ORISAM-RAD simulations reveal quite uniform values over the whole ESCOMPTE domain, comprised between 0.61±0.01 and 0.65±0.01 (at 440 nm), in excellent agreement with ground based in situ measurements and AERONET retrievals. Finally, the outputs of ORISAM-RAD have been used in a radiative transfer model in order to simulate the diurnal direct radiative forcing at different locations (urban, industrial and rural). We show that anthropogenic aerosols strongly decrease surface solar radiation, with diurnal mean surface forcings comprised between −29.0±2.9 and −38.6±3.9 W m⁻², depending on the sites. This decrease is due to the reflection of solar radiations back to space (−7.3±0.8<ΔF_TOA<−12.3±1.2 W m⁻²) and to its absorption into the aerosol layer (21.1±2.1<ΔF_ATM<26.3±2.6 W m⁻²). These values are found to be consistent with those measured at local scale.     

Perceived and measured levels of environmental pollution: interdisciplinary research in the subarctic lowlands of northeast European Russia

Using interdisciplinary field research in the Usa Basin, northeast European Russia, we compared local inhabitants' perception of environmental problems with chemical and remote-sensing signatures of environmental pollution and their local impacts. Extensive coal mining since the 1930s around Inta and Vorkuta has left a legacy of pollution, detected by measuring snowpack, topsoil, and lichen chemistry, together with remote-sensing techniques and analysis of lake water and sediments. Vorkuta and its environs suffered the worst impacts, with significant metal loading and alkalization in lakes and topsoils, elevated metals and cations in terricolous (reindeer) lichens, and changes in vegetation communities. Although the coal industry has declined recently, the area boasts a booming oil and gas industry, based around Usinsk. Local perceptions and concerns of environmental pollution and protection were higher in Usinsk, as a result of increased awareness after a major oil spill in 1994, compared with Vorkuta's inhabitants, who perceived air pollution as the primary environmental threat. Our studies indicate that the principal sources of atmospheric emissions and local deposition within 25 to 40 km of Vorkuta were coal combustion from power and heating plants, coal mines, and a cement factory. Local people evaluated air pollution from direct observations and personal experiences, such as discoloration of snow and respiratory problems, whereas scientific knowledge played a minor role in shaping these perceptions.     

A model to predict the pollution potential with the use of Airways Surface Observation data

An atmospheric diffusion model of the Lettau-box type is developed, tested and applied. The principle attribute of the model is that readily available Airways Surface Observation data is used to estimate the mixing depth. In addition, the model does not assume that specific emitter-receptor location information be available. The test of the model yields added support to the validity of several physical relationships found in the literature. An application of the model emphasizes the value of Holzworth's “pollution potential” in its use of making comparisons between different cities.     

Validation of a Lagrangian model plume rise scheme using the Kincaid data set

Correct prediction of the initial rise of a plume due to momentum and buoyancy effects is an important factor in dispersion modelling. A new plume rise scheme, based upon conservation equations of mass, momentum and heat, for the Lagrangian model, NAME, is described. The conservation equations are consistent with the well-known analytical plume rise formulae for both momentum- and buoyancy-dominated plumes. The performance of the new scheme is assessed against data from the Kincaid field experiment. Results show that the new scheme adds value to the model and significantly outperforms the previous plume rise scheme. Using data from assessments of atmospheric dispersion models using the Kincaid data set, it is shown that NAME is comparable to other models over short ranges.     

DMS photochemistry during the Asian dust-storm period in the Spring of 2001: model simulations vs. field observations

This study examines the local/regional DMS oxidation chemistry on Jeju Island (33.17 degrees N, 126.10 degrees E) during the Asian dust-storm (ADS) period of April 2001. Three ADS events were observed during the periods of April 10-12, 13-14, and 25-26, respectively. For comparative purposes, a non-Asian-dust-storm (NADS) period was also considered in this study, which represents the entire measurement periods in April except the ADS events. The atmospheric concentrations of DMS and SO2 were measured at a ground station on Jeju Island, Korea, as part of the ACE-Asia intensive operation. DMS (means of 34-52 pptv) and SO2 (means of 0.96-1.14 ppbv) levels measured during the ADS period were higher than those (mean of 0.45 ppbv) during the NADS period. The enhanced DMS levels during the ADS period were likely due to the increase in DMS flux under reduced oxidant levels (OH and NO3). SO2 levels between the two contrasting periods were affected sensitively by some factors such as air mass origins. The diurnal variation patterns of DMS observed during the two periods were largely different from those seen in the background environment (e.g., the marine boundary layer (MBL)). In contrast to the MBL, the maximum DMS value during the ADS period was seen in the late afternoon at about sunset; this reversed pattern appears to be regulated by certain factors (e.g., enhanced NO3 oxidation). The sea-to-air fluxes of DMS between the ADS and NADS periods were calculated based on the mass-balance photochemical-modeling approach; their results were clearly distinguished with the values of 4.4 and 2.4 micromole m(-2) day(-1), respectively. This study confirmed that the contribution of DMS oxidation to observed SO2 levels on Jeju Island was not significant during our study period regardless of ADS or NADS periods.     

An efficient Lagrangian stochastic model of vertical dispersion in the convective boundary layer

We consider the one-dimensional case of vertical dispersion in the convective boundary layer (CBL) assuming that the turbulence field is stationary and horizontally homogeneous. The dispersion process is simulated by following Lagrangian trajectories of many independent tracer particles in the turbulent flow field, leading to a prediction of the mean concentration. The particle acceleration is determined using a stochastic differential equation, assuming that the joint evolution of the particle velocity and position is a Markov process. The equation consists of a deterministic term and a random term. While the formulation is standard, attention has been focused in recent years on various ways of calculating the deterministic term using the well-mixed condition incorporating the Fokker–Planck equation. Here we propose a simple parameterisation for the deterministic acceleration term by approximating it as a quadratic function of velocity. Such a function is shown to represent well the acceleration under moderate velocity skewness conditions observed in the CBL. The coefficients in the quadratic form are determined in terms of given turbulence statistics by directly integrating the Fokker–Planck equation. An advantage of this approach is that, unlike in existing Lagrangian stochastic models for the CBL, the use of the turbulence statistics up to the fourth order can be made without assuming any predefined form for the probability distribution function (PDF) of the velocity. The main strength of the model, however, lies in its simplicity and computational efficiency. The dispersion results obtained from the new model are compared with existing laboratory data as well as with those obtained from a more complex Lagrangian model in which the deterministic acceleration term is based on a bi-Gaussian velocity PDF. The comparison shows that the new model performs well.     

Environmental forensic investigation of the air pollution from a cement manufacturing unit

Abstract

Cement manufacturing is a process that results in the emission of significant quantities of suspended particulate matter (SPM) to the ambient air. An environmental forensic investigation was carried out in the surroundings of a major cement manufacturing unit at a place called Coimbatore in the southern Indian state of Tamil Nadu. The investigation was carried out to identify the contribution of the cement manufacturing unit to the SPM concentration of the surrounding air environment. The sampling points’ selection and sample collection were done following the principles outlined in the INTERPOL Manual for Pollution Crime Forensic Investigation. On-site monitoring of the air samples was carried out using Mini Laser Aerosol Spectrometer (GRIMM, Mini-LAS Model 11R). The instrument was capable of measuring particles ranging from 0.25 to 32 µm and classifying them into 31 size channels. The test results at majority of the monitoring locations were well above the limits specified in the National Ambient Air Quality Standards of India. Microscopic studies of the dust samples were carried out for surface texture and particle shape. The spatial distribution of particles was analysed using geographic information system (GIS) for the visual identification of the extent of the pollution by keeping the cement factory as the focal point. The results from the GIS and microscopic analysis established the role of the cement factory in the particulate matter pollution of its surroundings, specifically in the areas North-West of the factory. The successfully adopted procedure can serve as a guideline for the environmental forensic investigation of similar pollution incidences.     

A modeling study of SOx-NOx-Hydrocarbon plumes and their transport to the background troposphere

A model which emulates the behavior of urban-industrial plumes has been developed and used to analyze the chemical reaction processes occurring as a polluted air mass is transported from an urban area. A 73-step reaction mechanism describing hydrocarbon/NO_xSO_x chemistry was used, with photolytic rate constants depending on the latitude, time of day and time of year. The model includes the physical processes of plume dilution, entrainment and dry deposition, and is simulated under a diurnally varying mixing layer or neutral atmospheric stability conditions.Simulation results are compared with reported field measurements for plumes from St. Louis, Milwaukee, and a power plant plume entrained in the Milwaukee urban plume. The agreement with field concentrations and SO₂ transformation rate data is good, the latter ranging from 1 to 12 % h⁻¹. The study was extended to hypothetical plumes for parametric analysis. In every case considered, the classic O₃ peak occurred at about 3:30 p.m., essentially independent of initial concentrations and plume departure time. The analysis also indicated that substantial SO₂ oxidation via homogeneous gas phase chemistry can occur at night-time, the prerequisite being a high HG/NO_x ratio.     

A Cournot competition model with the uniform pollution tariff: an application to NAFTA

This paper investigates the impact of a uniform pollution tariff on production, consumption and consumer welfare in the framework of the Cournot competition. It suggests that the uniform pollution tariff would raise the welfare of US consumers. However, it would penalise the higher-cost producer in the country where environmental regulations are more stringent. The policy implication is that economic integration, such as NAFTA, should take discriminatory pollution tariffs into consideration.