An urban agglomeration (UA), similar to a megalopolis or a metropolitan area, is a region where cities and people are concentrated, and where air pollution has adversely impacted on sustainable and high quality development. Studies on the spatio-temporal trends and the factors which influence PM2.5 concentrations may be used as a reference to support air pollution control policy for major UAs throughout the world. Nineteen UAs in China covering the years 2000–2016 were chosen as the research object, the PM2.5 concentrations being used to reflect air pollution and being estimated from analysis of remote sensing images. The Exploratory Spatial Data Analysis method was used to study the spatio-temporal trends for PM2.5 concentrations, and the Geodetector method was used to examine the factors influencing the PM2.5 concentrations. The results revealed that (i) the temporal trend for the average values of the PM2.5 concentrations in the UAs followed an inverted U-shaped curve and the inflection points of the curve occurred in 2007. (ii) The PM2.5 concentrations in the UAs exhibited significant global spatial autocorrelation with the high–high type and the low–low type being the main categories. (iii) The rate of land urbanization and the structure of energy consumption were the main factors which influenced the PM2.5 concentrations in the UAs.
PM2.5 (particulate matter with an aerodynamic diameter <2.5 μm) samples were collected in Huangshi, central China, from March 2012 to February 2013 and were analyzed for dicarboxylic acids (diacids) and related compounds (DARCs). Oxalic acid (C2; 416 ng m?3) was the most abundant species, followed by phthalic (Ph; 122 ng m?3), terephthalic (tPh; 116 ng m?3), succinic (C4; 70.4 ng m?3), azelaic (C9; 67.9 ng m?3), and adipic (C6; 57.8 ng m?3) acids. Relatively high abundances of Ph and tPh differed from the distribution in urban and marine aerosols, indicating contributions from nearby anthropogenic sources. Glyoxylic acid (ωC2; 41.4 ng m?3) was the dominant oxoacid, followed by 9-oxononanoic (ωC9; 40.8 ng m?3) and pyruvic (Pyr; 24.1 ng m?3) acids. Glyoxal (Gly; 35.5 ng m?3) was the dominant α-dicarbonyl. Highest average concentrations were found for C2, ωC2, and C9 in autumn, for C4, for Pyr and C6 in spring, for Ph, ωC9, and Gly in summer, whereas the lowest values were observed in winter. Seasonal variations and correlation coefficients of DARCs demonstrate that both primary emissions and secondary production are important sources. Principal component analysis of selected DARCs species suggests that a mixing of air masses from anthropogenic and biogenic sources contribute to the Huangshi aerosols.
Implications: Both primary emissions and secondary production are important sources of diacids and related compounds in PM2.5 from Huangshi, central China. Principal component analysis of selected diacids in Huangshi aerosols suggests that mixing of air masses from anthropogenic and biogenic sources contribute to ambient aerosols in central China. 相似文献
Environmental Science and Pollution Research - The analysis and prediction of water quality are of great significance to water quality management and pollution control. In general, current water... 相似文献
• The effectiveness of four different ventilation systems was compared in depth.• Airflow and bacteria-carrying particles concentration were quantitatively analyzed.• Vertical laminar airflow with high airflow rate could not achieve desired effect.• Temperature-controlled airflow ventilation could guarantee air cleanliness. Biological particles in the operating room (OR) air environment can cause surgical site infections (SSIs). Various ventilation systems have been employed in ORs to ensure an ultraclean environment. However, the effect of different ventilation systems on the control of bacteria-carrying particles (BCPs) released from the surgical staff during surgery is unclear. In this study, the performance of four different ventilation systems (vertical laminar airflow ventilation (VLAF), horizontal laminar airflow ventilation (HLAF), differential vertical airflow ventilation (DVAF), and temperature-controlled airflow ventilation (TAF)) used in an OR was evaluated and compared based on the spatial BCP concentration. The airflow field in the OR was solved by the Renormalization Group (RNG) k-e turbulence model, and the BCP phase was calculated by Lagrangian particle tracking (LPT) and the discrete random walk (DRW) model. It was found that the TAF system was the most effective ventilation system among the four ventilation systems for ensuring air cleanliness in the operating area. This study also indicated that air cleanliness in the operating area depended not only on the airflow rate of the ventilation system but also on the airflow distribution, which was greatly affected by obstacles such as surgical lamps and surgical staff. 相似文献
Environmental Geochemistry and Health - The purpose of this study was to investigate the associations between levels of lead (Pb), cadmium (Cd), chromium (Cr), and manganese (Mn) in the PM2.5 and... 相似文献
Field surveys were carried out from January 2007 to December 2008 to investigate seasonal variations of dissolved inorganic nitrogen (DIN) and phosphorus (DIP) transported to the Linjiang Bay of the Three Gorges Reservoir, China. The results revealed that both DIN and DIP exhibited large seasonal variability. DIN (dominated by NH4?CN) concentrations were drastically higher in the dry season than those in the rainy season, and the same seasonal patterns of DIP concentrations and DIN and DIP fluxes were observed but inverse to that of DIN concentrations. The interannual variation in DIN fluxes descended by 28.2% from 2007 to 2008, while DIP fluxes increased by 40.9%, which were closely constant with interannual changes in DIN and DIP concentrations, respectively. The study indicated that nutrient fluxes (DIN and DIP) were strongly correlated with both nutrient concentrations and river discharge, and the Linjiang Bay received approximately 3,416 × 103 kg DIN and 324 × 103 kg DIP every year. In addition, DIN mainly originated from point sources, but DIP originated from non-point sources. It is shown that to control point source pollution is the most effective step for water quality improvement and reducing nutrient loading inputs in the Linjiang Bay. 相似文献
Hatching asynchrony commonly induces a size hierarchy among siblings and the resultant competition for food between siblings
can often lead to starvation of the smallest chicks within a brood. We created herring gull (Larus argentatus) broods with varying degrees of hatching synchrony by manipulating the timing of incubation while maintaining the originally
laid eggs. The degree of hatching asynchrony affected sibling size hierarchy at the time of hatching of the last-hatched ”c-chick.”
In unmanipulated broods, there was no disadvantage of being a c-chick. However, when asynchrony was experimentally increased,
we found reduced survival of the c-chick only in the exaggerated asynchronous experimental group. The effects were observable
only during the first 10 days of chick life. We recorded no cases of the chicks dying of starvation. Furthermore, behavioral
observations indicated that there was no sibling competition, and no selective feeding of larger sibs in the study colony.
We propose that the observed lower survival rates of c-chicks in exaggerated asynchronous broods resulted from their lesser
motor abilities, affecting their chances of escaping predators. Fledging success for the whole colony was generally high and
almost half of all pairs fledged all three chicks, which is indicative of a good feeding environment. We argue that normal
hatching asynchrony is a favorable solution in a good feeding environment, but that increased asynchrony reduces breeding
success. We do not view asynchrony in the herring gull as an adaptation for brood reduction and propose instead that it may
come about because there has been selection for incubation to start before clutch completion.
Received: 14 April 1999 / Received in revised form: 20 October 1999 / Accepted: 23 January 2000 相似文献