To evaluate plant and herbivore responses to nitrogen we conducted a fertilization study at a low and high pollution site in the mixed conifer forests surrounding Los Angeles, California. Contrary to expectations, discriminant function analysis of oak herbivore communities showed significant response to N fertilization when atmospheric deposition was high, but not when atmospheric deposition was low. We hypothesize that longer-term fertilization treatments are needed at the low pollution site before foliar N nutrition increases sufficiently to affect herbivore communities. At the high pollution site, fertilization was also associated with increased catkin production and higher densities of a byturid beetle that feeds on the catkins of oak. Leaf nitrogen and nitrate were significantly higher at the high pollution site compared to the low pollution site. Foliar nitrate concentrations were positively correlated with abundance of sucking insects, leafrollers and plutellids in all three years of the study.

Management of ambient concentrations of Volatile Organic Compounds (VOCs) is essential for maintaining low ozone levels in urban areas where its formation is under a VOC-limited regime. The significant decrease in traffic-induced VOC emissions in many developed countries resulted in relatively comparable shares of traffic and non-traffic VOC emissions in urban airsheds. A key step for urban air quality management is allocating ambient VOC concentrations to their pertinent sources. This study presents an approach that can aid in identifying sources that contribute to observed BTEX concentrations in areas characterized by low BTEX concentrations, where traditional source apportionment techniques are not useful. Analysis of seasonal and diurnal variations of ambient BTEX concentrations from two monitoring stations located in distinct areas reveal the possibility to identify source categories. Specifically, the varying oxidation rates of airborne BTEX compounds are used to allocate contributions of traffic emissions and evaporative sources to observed BTEX concentrations. BTEX sources are identified from temporal variations of ambient concentration.

A passive air sampler was developed for collecting polycyclic aromatic hydrocarbons (PAHs) in air mass from various directions. The airflow velocity within the sampler was assessed for its responses to ambient wind speed and direction. The sampler was examined for trapped particles, evaluated quantitatively for influence of airflow velocity and temperature on PAH uptake, examined for PAH uptake kinetics, calibrated against active sampling, and finally tested in the field. The airflow volume passing the sampler was linearly proportional to ambient wind speed and sensitive to wind direction. The uptake rate for an individual PAH was a function of airflow velocity, temperature and the octanol–air partitioning coefficient of the PAH. For all PAHs with more than two rings, the passive sampler operated in a linear uptake phase for three weeks. Different PAH concentrations were obtained in air masses from different directions in the field test. A novel directional passive air sampler was developed and tested for monitoring PAHs in air masses from different directions.

Spatial variations of Carbon Monoxide (CO) are examined in the urban environment of Ouagadougou, Burkina Faso. Focus is given on the variations between urban background, roadside and in-traffic measurements. Results show significant differences between the three methods where average in-traffic values were 2-3 times higher than average roadside values and 10-12 times higher than average background values. During traffic congestions these differences extended up to 6 and 20 times respectively. Results are discussed in relation to human exposure assessments and WHO guidelines.

Source apportionment analysis was used to identify the factors contributing to atmospheric pollution at a monitoring location in the Southeast of Spain, a well documented area with an arid climate and high insolation favouring two sources of particulate matter: secondary transformation in the atmosphere and resuspension of crustal dry soils to the air. These conditions are further complicated by numerous industrial facilities in the area of the historical city of Cartagena. This paper describes the air quality of an area which includes a zinc metallurgical industry, a petrochemical factory, an oil power station, a shipyard and natural phenomena including African dust transport and resuspension of regional and/or local crustal materials. Major and trace element concentrations in PM10 and PM2.5 were determined at two monitoring stations in Cartagena (one PM10 sampler located at a traffic hotspot and the PM2.5 sampler at a suburban station), during 2004 and 2005. Results showed that in the PM10 fraction, the zinc metallurgical activity was linked to high levels of Cd, Zn and Pb; shipyard emission was associated with high levels of Cr and Ni; and high Ni and V levels were associated with the secondary aerosol indicating the contribution from oil combustion (oil-fired power station or petrochemical facilities). In the PM2.5 size fraction, the zinc source is defined by Zn and Pb; V, Ni and As appear with the oil combustion emissions. In contrast to PM10, shipyard activity is not consistently defined. Consistent sources found in both size fractions include crustal materials and traffic emissions.

PM₁₀ particles were collected over three sites in France. The first one, Montagney was a rural site that was considered as a reference site. The second site Saclay, close to a highway, was used to study the influence of the traffic. The third site was Dunkerque, one of the most industrial areas in France for the production of steel, aluminium and petroleum refinement. More than 50 element concentrations were determined by instrumental neutron activation analysis and inductively coupled plasma-mass spectrometry. Comparisons between Saclay and Montagney shown that some elements, considered as crustal elements had similar concentration variations and weak (close to 1) enrichment factors. Elements with enrichment factors higher than 10 shown in Montagney correlated variations, with a Winter maximum, that should be due to Winter heating sources. Over Saclay, most of elements with high enrichment factors were attributed to the dense traffic of the highway. This is particularly true for Mn, Fe, Zn, Ba, Sb, Cu. Some additional elements correlated also, without a particular origin that can be ascertained. In Dunkerque, the most important industry is steel production. Correlation studies shown that Tl, Cs, Ba, Ag, Cu, Rb, Se, Mn, Pb concentration variations were closely associated to the Fe concentration variations. The second polluting industry is aluminium production. Correlation studies allowed to associate Ni, Y, Co, V, rare earth elements, Ti, Sr, Th, U, Ca, Sc, concentration variations to the aluminium concentration variations. A third important industry is petroleum refinement. The only element observed here and that is suspected to be emitted more specifically is La, used in cracking processes. An important enrichment of La with respect to Ce is observed. A strong decrease of the ratio Cl/Na was observed over the three sites, between the beginning of the experiment in Autumn 2005, and its end in Spring 2006. This was attributed to a release of gaseous HCl, produced by acidification of aerosols by other pollutants like NO x and SO x , that should have been oxidized to NO₂ and SO₃, then dissolved in the aerosols. The effects responsible for the loss of Cl, represents a large surface and long-term pollution event over the North of France. This work allowed a characterization of the heavy metal concentrations of the aerosol that will sustain results published in a companion paper, and that concerned the bio-accumulation of metals by Scleropodium purum, simultaneously exposed in the same sites.

The dust fall in a region is closely related to upwind sources. Dust fall from sandstorms has a strong influence on industry, agriculture, and daily life. Hohhot, the capital of Inner Mongolia Autonomous Region, is downwind of the Inner Mongolia Plateau and experiences frequent sandstorms during the spring monsoon season. This study investigated the relationship between dust fall in the Hohhot area and surface soils on the Inner Mongolia Plateau. Samples of dust fall from Hohhot and surface soils from the plateau were analyzed for major and trace elements. The SiO₂ content of dust fall from sandstorms differs from that of the plateau soils by only 2.77%, indicating that the main dust fall source for Hohhot is surface soils from the plateau. Dust samples from coal smoke, roads, and buildings were used for comparison. The As content in dust fall from sandstorms is greater than that found in the plateau soils and in dust from non-sandstorm days. This indicates that As is added to the sand during transport from the plateau by coal factories near Hohhot. The second most important dust source is traffic, as evidenced by Pb contents. Preventing erosion of sand upwind of Hohhot during the spring monsoon is key to improving and managing air quality in the Hohhot region. This can be accomplished through management of the farm grassland areas.

Understanding and controlling air pollution in highly populated areas is very important, although interpreting the levels of gaseous pollutants and airborne particulate matter is complicated by dominant natural and anthropogenic emissions, micro-meteorological processes, and chemical reactions which take place directly in the atmosphere. For this reason, it is very difficult to relate the characteristics of air pollution to one or more specific emission sources. The aim of this paper is to detect associations among elements and organic compounds emitted from specific sources by means of chemical analyses, statistical processing of data, seasonal evolution study, and geochemical considerations to trace their origin. A detailed characterization of air quality during the period September 2000-September 2001 was carried out in three locations of the Venice region: A heavy traffic urban site, a public park, and the island centre of the city of Venice. Twenty-eight inorganic elements, four polycyclic aromatic hydrocarbons, CO and benzene were quantified and processed by a statistical procedure based on factor analysis considering variations on a seasonal basis. Results show the presence of associations between elements and compounds with the same behaviour in all sampling points. This indicates that several pollutants originate from a common source, and are then “diluted” throughout the study area, maintaining the imprint of their origin. Pt, polycyclic aromatic hydrocarbons, CO and benzene originating from the exhaust gas of vehicles are all linked in the traffic factor, whereas Cd is associated with Se, having a common source in industrial processes.