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[en] It is the purpose of this paper to describe the Air Pollution Project that is being undertaken at the Ecole d'Hygiene of Universite de Montreal. The project is still in its organization phase. However, in the absence of any results, a description of the project with an emphasis on its goals, instrumentation and operational technique might prove interesting and raise comments beneficial to the project. (author)
[en] We present molecular line and 1.4 mm continuum observations toward five massive star-forming regions at arcsecond resolution using the Submillimeter Array. We find that the warm molecular gas surrounding each H II region (as traced by SO2 and OCS) appears to be undergoing bulk rotation. From the molecular line emission and thermal component of the continuum emission, we independently derived gas masses for each region which are consistent with each other. From the free-free component of the continuum emission, we estimate the minimum stellar mass required to power the H II region and find that this mass, when added to the derived gas mass, is a significant fraction of the dynamical mass for that region.
[en] Vertical profiles of O_3 and SO_2 concentrations were monitored at the Borden Forest site in southern Ontario, Canada from May 2008 to April 2013. A modified gradient method (MGM) was applied to estimate O_3 and SO_2 dry deposition fluxes using concentration gradients between a level above and a level below the canopy top. The calculated five-year mean (median) dry deposition velocity (V_d) were 0.35 (0.27) and 0.59 (0.54) cm s"−"1, respectively, for O_3 and SO_2. V_d(O_3) exhibited large seasonal variations with the highest monthly mean of 0.68 cm s"−"1 in August and the lowest of 0.09 cm s"−"1 in February. In contrast, seasonal variations of V_d(SO_2) were smaller with monthly means ranging from 0.48 (May) to 0.81 cm s"−"1 (December). The different seasonal variations between O_3 and SO_2 were caused by the enhanced SO_2 uptake by snow surfaces in winter. Diurnal variations showed a peak value of V_d in early morning in summer months for both O_3 and SO_2. Canopy wetness increased the non-stomatal uptake of O_3 while decreasing the stomatal uptake. This also applied to SO_2, but additional factors such as surface acidity also played an important role on the overall uptake. - Highlights: • Application of a modified gradient-method for quantifying dry deposition is demonstrated. • A five-year dry deposition database is developed for O_3 and SO_2 over a mixed forest. • Canopy wetness enhances non-stomatal O_3 uptake while inhibits stomatal uptake. • High surface acidity reduces SO_2 dry deposition. - Capsule: A five-year dataset of O_3 and SO_2 dry deposition velocities was generated from concentration gradient measurement data using a modified gradient method.
[en] Various studies have illustrated that exposure to ambient air pollution has negative impacts on health. However, little evidence exists on the effects of ambient air pollution on circulatory mortality in Xi’an, China. This study aims to investigate and ascertain the association between short-term exposure to ambient air pollutants and circulatory mortality in Xi’an, China. Daily average concentrations of PM2.5, SO2, and O3, meteorological data (temperature and relative humidity) and daily counts of circulatory mortality were obtained between January 2014 and June 2016. Mortality was stratified by gender and age group (≤ 64 years and ≥ 65 years). A generalized additive model (GAM) with natural splines (NS) was constructed to analyze the relationship between ambient air pollutants and daily circulatory mortality. There were 57,570 cases of circulatory mortality, with cerebrovascular and ischemic heart diseases accounting for 48.5% and 43.5%, respectively. All ambient air pollutants displayed different seasonal patterns. In the single pollutant model, 10 μg/m3 increase in 2-day moving average concentrations of PM2.5, SO2, and O3 was associated with relative risk of 1.288(1.198, 1.388), 1.360(0.877, 2.331), and 1.324(1.059, 1.705) in circulatory mortality, respectively. After adjusting for collinearity in the multi-pollutant model, the effects remained statistically significant. The ≥ 65 years and female sub-groups were associated with a higher risk of circulatory mortality. Short-term exposure to ambient air pollutants plays a pivotal role in the genesis of circulatory mortality in Xi’an. Responses to ambient air pollutants exposure in relation to circulatory mortality are different when analyzed by sub-groups.
[en] The performance of Cytisus striatus in association with different microbial inoculant treatments on the dissipation of the insecticide hexachlorocyclohexane (HCH) was studied. Two soils with different organic matter (A and B soil) content were spiked with 0 or 65 mg HCH kg−1. Plants were either not inoculated (NI), or inoculated with the endophyte Rhodococcus erythropolis ET54b and the HCH-degrader Sphingomonas sp. D4 separately or in combination (ET, D4 and ETD4). Unplanted pots were also established. HCH phytotoxicity was more pronounced in the B soil. Soil HCH concentrations in unplanted pots were similar to initial concentrations, whereas concentrations were reduced after plant growth: by 20% and 8% in A and B soil, respectively. Microbial inoculants also modified HCH dissipation, although effects were soil-dependent. Inoculation with the combination of strains (ETD4) led to a significant enhancement in HCH dissipation: up to 53% in the A soil and 43% in the B soil. -- Highlights: •Effect of microbial inoculants on HCH dissipation was studied in a plant-soil system. •Inoculation of C. striatus with bacterial strains strongly enhance HCH dissipation. •Retention of HCH by organic matter can influence efficiency of HCH phytoremediation. -- The inoculation of Cytisus striatus with a combination of bacterial strains is a promising approach for the remediation of HCH-contaminated sites
[en] An upgraded parameterization scheme for gaseous dry-deposition velocities has been developed for a new regional air-quality model with a 91-species gas-phase chemistry mechanism, of which 48 species are ''transported'' species. The well-known resistance analogy to dry deposition is adopted in the present scheme, with both O3 and SO2 taken as base species. Stomatal resistances are calculated for all dry-depositing species using a ''sunlit/shaded big-leaf'' canopy stomatal resistance submodel. Dry-ground, wet-ground, dry-cuticle, and wet-cuticle resistances for O3 and SO2, and parameters for calculating canopy stomatal resistance and aerodynamic resistance for these two base species are given as input parameters for each of the 15 land-use categories and/or five seasonal categories considered by the scheme. Dry-ground, wet-ground, dry-cuticle, and wet-cuticle resistances for the other 29 model species for which dry deposition is considered to be a significant process are scaled to the resistances of O3 and SO2 based on published measurements of their dry deposition and/or their aqueous solubility and oxidizing capacity. Mesophyll resistances are treated as dependent only on chemical species. Field experimental data have then been used to evaluate the scheme's performance for O3 and SO2. Example sets of modelled dry-deposition velocities have also been calculated for all 31 dry-deposited species and 15 land-use categories for different environmental conditions. This new scheme incorporates updated information on dry-deposition measurements and is able to predict deposition velocities for 31 gaseous species for different land-use types, seasons, and meteorological conditions. (author)
[en] In the case of emission of non-uniformly dispersed pollutants such as SO2 the negative effects depend on the location of the sources. A unit increase at one source must be compensated by either a larger or smaller reduction at another source to keep the negative effects at the same level. Emission trading between countries is possible under the Second Sulphur Protocol. Exchange rate trading and third party problems are studied within a simultaneous model facilitating impositions of various environmental constraints. Simulations based on the negotiated emission quotas are offered. Results indicate potential cost savings of 19%. 16 refs
[en] Following the great flooding of summer 1998, the mid-lower Yangtze Basin further suffered from another large flooding in summer 1999. Successive droughts through three recent summers (1997-1999) appeared in north China in addition, leading to an abnormal summer climate pattern of ''north drought with south flooding''. Such southward move of the summer monsoon rainy belt in east China started in the late 1970s-early 1980s. Its main cause may not be a purely natural climate change, but the acceleration of industrialization in east China could play a major role by emitting large volumes of SO2, especially from the rapidly growing rural factories of east China. The annual release of SO2 in China exceeded 20Tg during 1992-1998, so dense sulfate aerosols covered the central east China which significantly reduced the sunlight. Although present estimates for the changes of clear sky global solar radiation may include some error, they show that the negative radiative forcing of sulfate aerosols in central east China by far exceeds the effect of greenhouse warming in summer. Hence the mid-summer monsoon rainy belt of east China has a trend moving southward in 21 recent years (1979-1999), showing the very sensitive characteristic of the summer monsoon system to the change in heat equilibrium of the land surface. The occurrence rate of summer climate pattern of ''north drought with south flooding'' in east China during 21 recent years is the largest since AD 950; such anomalous climate has brought large losses to China. The only possible way to reverse this southward trend of summer monsoon rainy belt is to significantly reduce air pollution by using more clean energy. Recently, the PRC has paid serious attention to this problem by adopting a series of countermeasures. (author)
[en] Sulfur dioxide is a major air pollutant in the environment. Fortunately, the plant purification system can effectively reduce SO2 pollution. However, the effect mechanism of plant purification system for the dynamic evolution of SO2 remains incompletely clear. In this work, inspired by the “Boston ivy,” we successfully designed and constructed a semi-continuous plant system. Subsequently, based on the “vine-like plant” and the “island-like plant,” the semi-continuous plant system and the isolated plant system are selected as the models of plant purification system, respectively. The dynamic evolution of SO2 in the plant systems is investigated using the computational fluid dynamic (CFD) method. It is demonstrated that the dynamic evolution of SO2 is impacted by the plant structure and the flow path ((cg/lg) + (cl/ll)). In the semi-continuous plant system, the strong flow paths with gradually weakened fluctuation are restricted by this special plant structure, the length of flow paths are extended, and more SO2 can be dissolved. In the isolated plant system, the mild flow paths with linear relationship can easily pass through the plants, such that only a little SO2 is dissolved. Overall, the present study opens a new path into the dynamic evolution of SO2 pollution in the plant systems, which helps providing guidance for the designing of plant purification system.
[en] To the exclusion of other major atmospheric pollutants, sulfur dioxide is mainly responsible for attack upon dolomite. This article characterizes Laurel Dolomite on the basis of composition, texture, and porosity; describes the mechanism of the SO2 reaction with dolomite; and develops two equations for the prediction of the rate of decay of dolomite. Over a period of 120 yr nearly 3.57 mm surface reduction at protected areas and 0.915 mm surface reduction at unprotected surfaces of a building in Louisville was calculated. However, these values could not be verified because measurement of these quantities in the field cannot be made