Atmospheric Environment (v.37, #17)

When atmospheric pollutant dispersion is simulated over complex terrain, the turbulence input parameters are often prescribed according to standard parameterisation based on surface layer quantities. These last are available from literature. In the past, several different parameterisations for the first few moments of the turbulence velocity statistic and for the Lagrangian time scale have been developed and tested in different stability conditions.The main shortcomings for using these parameterisations are their inadequateness in predicting the turbulence field in horizontally non-homogeneous boundary layer (like for example in complex terrain or in urban heat island) and the essentially local nature of the prescribed turbulence. The purpose of this work is to suggest proper methods for predicting turbulence field for dispersion model over complex terrain and, more generally, in horizontally non-homogeneous conditions.The modelling system RMS (RAMS–MIRS–SPRAY) is applied to the present study. We introduced new non-local turbulence closures in the RAMS circulation model, which provides both mean wind and turbulence fields. Then, through the interface code (MIRS), the input quantities needed to the Lagrangian stochastic dispersion model (SPRAY) are computed. The model system is validated against a tracer experiment performed in a wind tunnel over a schematic two-dimensional valley.
Keywords: Dispersion; Turbulence closure; Complex terrain; Wind tunnel flow; Neutral boundary layer;

The Ogawa passive sampler (Ogawa USA, Pompano Beach, Florida) is a useful tool for monitoring atmospheric ammonia (NH3(g)) concentrations and assessing the effects of agricultural waste management practices on NH3(g) emissions. The Ogawa sampler, with filter-discs impregnated with citric acid, was used to trap and determine NH3(g) concentrations in a variety of agricultural settings. A wide range of NH3(g) concentrations can be monitored by varying the sampler exposure time, provided that no more than ∼10 μg of NH3-N are adsorbed on the acid-coated filters. Concentrations less than 1 μg NH3-N m−3 can be detected using long deployments (⩽14 days), while concentrations as great as 10 mg NH3-N m−3 may be determined in very short (e.g. 5 min) deployments. Reproducibility ranged from 5% to 10% over the range of concentrations studied and passive determinations of NH3(g) were similar to those determined using dilute-acid gas scrubbers.Background levels of NH3(g) at a non-agricultural site in southern Delaware were typically <1 μg NH3-N m−3. The air entering a chicken house was 10 μg NH3-N m−3, reflecting the background levels in agricultural settings in this region. Within the house, concentrations ⩽8.5 mg NH3-N m−3 were observed, reflecting the high rates of NH3(g) emission from chicken excreta. Using measured NH3(g) concentrations and poultry house ventilation rates, we estimate that each broiler grown to production size over 6 weeks contributes approximately 19±3 g of NH3-N to the atmosphere, a value consistent with other published results.
Keywords: Atmospheric nitrogen; Agricultural emissions; Nitrogen budget; Gas sampling;

Liquefied petroleum gas effect on ozone formation in Mexico city by Jaimes-Lopez J Luis; Sandoval-Fernández Julio; González-Macı́as Uriel; González-Ortı́z Emmanuel (2327-2335).
An experimental study of outdoor smog chambers was carried out to determine effects of liquefied petroleum gas (LPG) on maximum ozone (O3 max). 60% additions of commercial LPG and 60%-propane/40% butane mixture of the initial concentration were introduced into eight smog chambers containing morning ambient air of Mexico City metropolitan area (MCMA). The ozone concentrations in each chamber were monitored throughout the day to determine the maximum of ozone. Dilution experiments of 50% total hydrocarbons and associated compounds to LPG in morning ambient air were carried out too.The results showed, that by increasing 60% of the associated compounds to LPG in the air of MCMA or diminishing 50% of them, had not an appreciable influence. The largest effect on ozone formation is determined by total nonmethane hydrocarbon (tNMHC) contained in the atmosphere, being the maximum of ozone formed in the smog chambers, on the average it diminished a 55%. C3 and C4 compounds associated to LPG only contribute a 14% of the total ozone formation.
Keywords: Smog chamber experiments; Air quality; Ozone precursors;

Environmental pollution is a problem affecting many cities in our planet. Santiago de Chile is one with the worst indices. Because of that, local authorities implemented a few years ago an air quality monitoring network with eight monitoring stations located across the whole city. These stations continuously collect information about the presence and level of atmospheric contaminants as well as meteorological indices.As the budget for this activity is limited, to increase the monitoring network as the city grows might be an inefficient decision. To evaluate alternative decisions multiple criteria should be consider. A statistical evaluation of some low cost modifications of the network becomes a valid research topic. This paper attempts to optimize Santiago's atmospheric monitoring network by excluding the least informative stations with respect to the variables under study: carbon monoxide (CO), airborne particulate material (PM10), ozone (O3) and sulfur dioxide (SO2). To accomplish this, an index of multivariate effectiveness, based on Shannon information index, is applied to that network.
Keywords: Effectiveness index; Monitoring network; Shannon information index; Atmospheric pollution;

Henry's law constants measurements of alachlor and dichlorvos between 283 and 298 K by Céline Gautier; Stéphane Le Calvé; Philippe Mirabel (2347-2353).
In this work, a dynamic system based on the water/air equilibrium at the interface within the length of a microporous tube was used to determine experimentally the Henry's law constants (HLC) of two pesticides: alachlor and dichlorvos. The measurements were conducted over the range 283–298 K. At 298 K, HLC were found to be equal to HLC=(14±2)×103 and HLC=(4.0±0.6)×103 (in units of M atm−1) for alachlor and dichlorvos, respectively. The obtained data were use to derive the following Arrhenius expressions: HLC=(8.0±3.4)×10−10 exp((9200±1600)/T) for alachlor and HLC=(2.8±0.4)×10−13 exp((11 100±1500)/T) for dichlorvos.At a cumulus temperature of 283 K, the fraction of alachlor and dichlorvos in the atmospheric aqueous phase is about 45% and 22%, respectively. Assuming that annual rainfall rate is 1 m/year, the wet deposition lifetimes were then estimated to be of the order of 2.8 days for alachlor and 5.6 days for dichlorvos. These latter are used to compare the relative importance of wet removal towards the lifetime in the gas phase.
Keywords: Pesticides; Alachlor; Dichlorvos; Henry's law constants;

Composition of the Finnish Arctic aerosol: collection and analysis of historic filter samples by Tarja Yli-Tuomi; Lisa Venditte; Philip K. Hopke; M.Shamsuzzoha Basunia; Sheldon Landsberger; Yrjö Viisanen; Jussi Paatero (2355-2364).
Week-long samples of total suspended particles have been collected between October 1964 and February 1978 from the Finnish Arctic. Neutron activation analysis, ion chromatography, and light-absorption techniques have been used to analyze the concentration of several heavy metals and other elements, major ions, methane sulfonate (MSA), and black carbon. Kevo is located near the Kola Peninsula and the effect of the industrial area can be seen. Compared to previous studies of Arctic aerosols carried out in North American Arctic, the Kevo results show higher concentration of anthropogenic pollutants and the seasonal variability for most constituents is weaker than the typical Arctic haze pattern. MSA, a marker of biogenic activity, has a clear seasonal cycle with a peak from April to August.
Keywords: Time series; Heavy metals; Methane sulfonate; Arctic Haze; Kola Peninsula;

The 2001 Phoenix Sunrise experiment: vertical mixing and chemistry during the morning transition in Phoenix by J.C Doran; C.M Berkowitz; R.L Coulter; W.J Shaw; C.W Spicer (2365-2377).
A field experiment was carried out in Phoenix during June 2001 to examine the role of vertical mixing on the O3 chemistry of the boundary layer during the morning transition from stable to unstable atmospheric conditions. Surface instruments, instruments located on two floors of a 39 story building in downtown Phoenix, and an instrumented airplane were used to characterize the evolving chemistry in the lowest 650 m of the atmosphere. Remote sensing and in situ platforms were used to obtain detailed profiles of winds and temperatures during the early morning hours and for several hours after sunrise. The analysis presented in this paper focuses on vertical profiles of CO, O3, and NO/NO y measured on the building and their relationship to the morning boundary layer evolution over Phoenix. Some features of these profiles were found that are consistent with a simple conceptual picture of nighttime trapping of pollutants in a stable surface layer and a subsequent release the following morning. On some days, however, evidence of significant vertical mixing was found during the early morning hours well before the times expected for the development of convective mixing after sunrise. Possible causes include advection, street canyon turbulence, and large-scale convergence, but a satisfactory explanation for the observed evolution of the chemical profiles has not yet been found.
Keywords: Morning transition; CO profiles; O3 profiles; Vertical mixing; Urban air quality;

The historical record of air pollution as defined by attic dust by Vito Ilacqua; Natalie C.J Freeman; Jerald Fagliano; Paul J Lioy (2379-2389).
The use of undisturbed attic dust as a tool for reconstructing historical air pollution was evaluated in this study. Dust collected from the attic of 201 houses in New Jersey, built between 1879 and 1995, was analyzed for lead with ICP-MS to validate the use of this method. The results were matched to an estimated pattern of the lead concentrations in attic dust, that was based upon historical data on lead gasoline consumption and emissions into the ambient air. In spite of the numerous uncertainties implied in such a comparison, the pattern of lead concentrations found in the attic dust approximated, within intervals of about 10 years, the time course of the lead emissions into the air. 137Cs concentrations were measured in the attic dust samples using gamma spectrometry to investigate the possibility of a local source contaminating the ambient air in Dover Township, NJ. No statistical differences in 137Cesium concentrations were found between the attics in Dover Township and other locations in NJ. The 137Cs concentrations measured in all locations were found to increase with the age of the house. The observed dependence of 137Cs concentrations on the age of the house could be explained primarily by the patterns of radionuclide fallout that has occurred over time because of above ground nuclear weapons testing during the 1950s and 1960s.
Keywords: Air pollution history; Lead; 137Cs; Attic dust;

A study of trace metals and polycyclic aromatic hydrocarbons in the roadside environment by Roy M Harrison; Rob Tilling; Marı́a S Callén Romero; Stuart Harrad; Kym Jarvis (2391-2402).
A study has been conducted of the concentrations of a range of inorganic elements and polycyclic aromatic hydrocarbons during a winter period at a roadside location in Birmingham, UK. Particle number and NO x concentrations were also determined continuously during the study. The analysis of size distributions of trace metals and the calculation of enrichment factors allows the identification of a number of elements which appear to be related with anthropogenic emissions. Using NO x and particle count as tracers of road traffic emissions, the elements Cu, Zn, Mo, Ba and Pb show significant correlations indicative of a traffic source contribution. When the results for the PM0.2 size fraction are compared with those for PM10, correlations with NO x and particle count improve for Ba and to a lesser degree for Pb, indicating association with very fine particles, whereas for Cu and Mo, the correlations are weaker for the smaller size fraction. Correlations between methylphenanthrenes, often used as tracers of diesel exhaust, particle count and NO x are significant, while correlations between methylphenanthrenes and calcium become increasingly strong moving from PM10 through to PM0.2, suggesting an exhaust emission of this element. Enrichment factors for lead and its correlation with NO x remain elevated despite the cessation of use of lead in automotive gasoline in the UK, and a large reduction in lead in air concentrations. The data are supportive of the conclusion that the enrichment of most trace elements in roadside aerosol derives from vehicle wear products rather than exhaust emissions, for which organic compounds are likely to prove better source tracers.
Keywords: Metals; Polycyclic aromatic hydrocarbons; Traffic pollution; Source apportionment; Airborne particulate matter;

The Center for Space Research (CSR), in conjunction with the Monitoring Operations Division (MOD) of the Texas Commission on Environmental Quality (TCEQ), is evaluating the use of remotely sensed satellite data to assist in monitoring and predicting air quality in Texas. The challenges of meeting air quality standards established by the US Environmental Protection Agency (US EPA) are impacted by the transport of pollution into Texas that originates from outside our borders and are cumulative with those generated by local sources. In an attempt to quantify the concentrations of all pollution sources, MOD has installed ground-based monitoring stations in rural regions along the Texas geographic boundaries including the Gulf coast, as well as urban regions that are the predominant sources of domestic pollution. However, analysis of time-lapse GOES satellite imagery at MOD, clearly demonstrates the shortcomings of using only ground-based observations for monitoring air quality across Texas. These shortcomings include the vastness of State borders, that can only be monitored with a large number of ground-based sensors, and gradients in pollution concentration that depend upon the location of the point source, the meteorology governing its transport to Texas, and its diffusion across the region. With the launch of NASA's MODerate resolution Imaging Spectroradiometer (MODIS), the transport of aerosol-borne pollutants can now be monitored over land and ocean surfaces. Thus, CSR and MOD personnel have applied MODIS data to several classes of pollution that routinely impact Texas air quality. Results demonstrate MODIS data and products can detect and track the migration of pollutants. This paper presents one case study in which continental haze from the northeast moved into the region and subsequently required health advisories to be issued for 150 counties in Texas. It is concluded that MODIS provides the basis for developing advanced data products that will, when used in conjunction with ground-based observations, create a cost-effective and accurate pollution monitoring system for the entire state of Texas.
Keywords: Remote sensing; MODIS; Pollution; Air quality; Continental haze;

Author's reply by Julio M Fernández-Dı́az (2417-2420).