The microclimate of beach and foredune areas of North Padre Island along the mid-Texas coast was found to be greatly modified by vehicular and pedestrian traffic during investigations made from late fall to early summer 1973–74. The primary effect of human activity on microclimate was expressed as reduced cover and species diversity of the vegetation. As the intensity of human activity increased, elevation, especially of areas near the beach, was decreased, whereas average wind velocities near the ground surface, evaporation, atmospheric salinity near the ground surface, wind-carried sand particles near the ground surface, soil salinity, soil pH, average soil temperature and range in temperature, soil bulk density, and soil-water contents were increased. 相似文献
In the last four decades, various techniques including spectroscopic, wet chemical and mass spectrometric methods, have been developed and applied for the detection of ambient nitrous acid (HONO). We developed a HONO detection system based on long path photometry which consists of three independent modules i.e., sampling module, fluid propulsion module and detection module. In the propulsion module, solenoid pumps are applied. With solenoid pumps the pulsed flow can be computer controlled both in terms of pump stroke volume and pulse frequency, which enables the attainment of a very stable flow rate. In the detection module, a customized Liquid Waveguide Capillary Cell (LWCC) is used. The customized LWCC pre-sets the optical fiber in-coupling with the liquid wave guide, providing the option of fast startup and easy maintenance of the absorption photometry. In summer 2014, our system was deployed in a comprehensive campaign at a rural site in the North China Plain. More than one month of high quality HONO data spanning from the limit of detection to 5 ppb were collected. Intercomparison of our system with another established system from Forschungszentrum Juelich is presented and discussed. In conclusion, our instrument achieved a detection limit of 10 pptV within 2 min and a measurement uncertainty of 7%, which is well suited for investigation of the HONO budget from urban to rural conditions in China. 相似文献
Higher plants may be used as biomonitors for the assessment of atmospheric heavy metal pollution by means of their bioaccumulative properties. We evaluated the reliability of biomonitoring heavy metal pollution by horse chestnut and linden leaves, common species found in Belgrade city parks. The results show that the highest concentrations of heavy metals were found in horse chestnut leaves at Studentski Park site, amounting to 110.2, 20.3 and 4.9 g g–1 dry weight for Cu, Pb and Cd, respectively, which are considered above toxic levels for plants.Selected article from the Regional Symposium on Chemistry and Environment, Krusevac, Serbia, June 2003, organised by Dr. Branimir Jovancicevic. 相似文献
This paper assesses the distribution of ammonium (NH4+) and nitrate (NO3-) nitrogen deposition in native bushland soil adjacent to an open ventilated poultry farm. The farm is located in Thirlmere 150 km south west of Sydney, Australia. A total of 104 geographically referenced soil cores were obtained from the study area. Soil pH, electrical conductivity (EC), NH4(+) - and NO3(-)-nitrogen concentrations were analysed for variable trends at three depths, i.e. 0-30, 30-60, and 60-90 cm. Significantly higher concentrations of the two nitrogen forms and EC were observed nearer to the farm in the surface soil samples (0-30 cm). The distribution of NH4+, NO3- and EC were all correlated in surface samples throughout the study area. There was no indication of NH4+ and NO3- leaching within soil profile sampled and it appears that weeds and native vegetation had utilised the accumulated nitrogen. The level of N deposition adjacent to the poultry farm decreased downwind due to dispersion of plume and to the buffering effects from the bushland. 相似文献
The chloroform flux through the environment is apparently constant at some 660±220 Gg yr−1 (±1σ) and about 90% of the emissions are natural in origin: the largest single source being in offshore sea water (contributing 360±90 Gg yr−1), with soil processes the next most important (220±100 Gg yr−1). Other natural sources, mainly volcanic and geological, account for less than 20 Gg yr−1. The non-natural sources total 66±23 Gg yr−1 and are much better characterised than the natural sources. They are predominantly the result of using strong oxidising agent on organic material in the presence of chloride ion, a direct parallel with the natural processes occurring in soils.
Chloroform partitions preferentially into the atmosphere; the equilibrium distribution is greater than 99% and the average global atmospheric concentration has been calculated to be 18.5 pmol mol−1. Atmospheric oxidation, the principal removal process, is approximately in balance with the identified source fluxes. Chloroform is widely dispersed in the aquatic environment (even naturally present in some mineral waters). Consequently, it is also widely dispersed in the tissue of living creatures and in foodstuffs but there is little evidence of bioaccumulation and the quantities in foodstuffs and drinking water are not problematical for human ingestion at the highest concentrations found. Definitive studies have shown that current environmental concentrations of chloroform do not present an ecotoxicological risk, even to fish at the embryonic and larval stages when they are most susceptible.
By virtue of the very small amounts that actually become transported to the stratosphere, chloroform does not deplete ozone materially, nor is it a photochemically active volatile organic compound (VOC). It has a global warming potential that is less than that of the photochemically active VOCs and is not classed as a greenhouse gas. 相似文献