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.
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
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