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641.
642.
长春市热岛效应的时空演变研究 总被引:2,自引:0,他引:2
以长春市为例,借助1988年9月25日,1995年9月29日和2000年9月18日三个时相的TM/ETM+遥感影像,研究长春市近12年热岛效应的时空演化规律。研究发现:长春市热岛效应明显且多年稳定存在,热岛中心主要分布在宽城区南部、二道区北部伊通河两岸和绿园区西南部;绿园区西南部和宽城区西北部强热岛区面积呈逐年增加态势,二道区北部伊通河两岸热状况有所改善;从1998年到1995年和从1995年到2000年,热岛面积分别增加约9.32 km2和14.93km2,增长速度加快。 相似文献
643.
Heavy metal concentrations in urban soils are likely to increase over time because of continuous urbanization and heavy metal emissions. To estimate the accumulation rates of heavy metals in urban soils, we collected soil samples from residential areas with different building ages in the metropolitan cities of Shanghai, Shenzhen, and Beijing, China. Heavy metal concentrations in the soils varied among the cities and were primarily affected by soil parent material and the intensity of anthropogen... 相似文献
644.
Eugene Yee 《Environmental Fluid Mechanics》2009,9(4):389-407
The relationships between various normalized higher-order concentration moments in plumes dispersing in a built-up (urban)
environment have been investigated using a large concentration data set obtained in a boundary-layer water channel. This data
set consists of measurements of plume dispersion in a number of idealized obstacle arrays (e.g., cubical and non-cubical obstacles
in aligned and staggered arrangements with uniform, random and alternating heights). A remarkably robust feature of all the
concentration data was the observed collapse of the third- and fourth-order normalized concentration moments on the second-order
normalized concentration moment. The data are shown to collapse to a series of universal curves (independent of the geometry
of the obstacle array) and these curves were found to be identical to those observed previously for open-terrain plumes. The
results imply that the probability law of concentration in a plume dispersing in either a built-up environment or open terrain
has a universal form that can be specified by at most two independent parameters. The universal functions representing the
relationships between the normalized concentration moments were found to be well modeled (approximated) using a two-parameter
clipped-gamma probability law for the concentration. Finally, the clipped-gamma distribution was found to be in very good
conformance with the measured probability distribution of concentration for plumes dispersing in a built-up environment. 相似文献
645.
Occurrence and distribution of sediment-associated insecticides in urban waterways in the Pearl River Delta, China 总被引:5,自引:0,他引:5
Sediment-associated pesticides, including organochlorine (OCP), organophosphate (OP), and pyrethroid insecticides, were analyzed in urban waterways in three cities (Guangzhou, Dongguan, and Shenzhen) in the Pearl River Delta (PRD), China. The OCPs represented 27.2% of the detectable insecticides in sediment, and chlordanes, DDTs, and endosulfans were the most frequently detected OCPs. The currently used insecticide chlorpyrifos was the only OP detected above the reporting limit (RL), with concentrations ranging from <RL to 100 ng g−1 dry weight (dw). Additionally, pyrethroids were detected in all sediments with the sum pyrethroid concentrations ranging from 4.26 to 384 ng g−1 dw and this represented 64.9% of the sum insecticide concentration. Despite their widespread use, no studies have been conducted investigating the occurrence and distribution of pyrethroids in China. As the first report of pyrethroids in urban waterways in China, the current study found cypermethrin was the most abundant insecticide detected in the PRD at concentrations ranging from 1.44 to 219 ng g−1 dw. Spatially, sediment from more populous and urbanized areas (Shenzhen and Tianhe district in Guangzhou) had higher insecticide residues than less populous agricultural areas. In the more modernized city of Shenzhen, the OCPs were seldom detected, whereas more diverse patterns of pyrethroids were observed. Potential sources of these insecticides, especially the frequently detected pyrethroids, were most likely from pest control during urban landscaping maintenance and from abatement programs targeting mosquitoes and ants. Results suggested that a shift in application pattern and elevated urbanization increased accumulation of currently used insecticides like pyrethroids in sediment, and made them the predominate insecticides in the PRD urban waterways. 相似文献
646.
Baker LA 《Chemosphere》2011,84(6):779-784
Achieving better understanding phosphorus (P) flows through urban ecosystems is needed to conserve P, as non-renewable phosphate rock deposits become depleted and the global human population increases. A baseline mass flow analysis (MFA) for P developed for the Twin Cities Watershed (TCW, which includes most of the Minneapolis-St. Paul metropolitan region) showed that most P input was stored in the system (65%) or leaked from it (31%); only 4% was deliberately exported as useful products. In a realistic, comprehensive conservation scenario P input was reduced by 15%; deliberate export of P in the form of sewage sludge, food waste, and landscape waste was 68% of P input. In this scenario, increased deliberate export was accomplished by decreasing leakage (to 9% of input) and storage (to 23% of input). If used as agricultural fertilizer, the deliberately exported P in the conservation scenario would support about half of the food production required by the TCW. 相似文献
647.
Chiriac R De Araujos Morais J Carre J Bayard R Chovelon JM Gourdon R 《Waste management (New York, N.Y.)》2011,31(11):2294-2301
The emission of volatile organic compounds (VOCs) from municipal solid waste stored in a pilot-scale cell containing 6.4 tonnes of waste (storage facility which is left open during the first period (40 days) and then closed with recirculation of leachates during a second period (100 days)) was followed by dynamic sampling on activated carbon and analysed by GC–MS after solvent extraction. This was done in order to know the VOC emissions before the installation of a methanogenesis process for the entire waste mass. The results, expressed in reference to toluene, were exploited during the whole study on all the analyzable VOCs: alcohols, ketones and esters, alkanes, benzenic and cyclic compounds, chlorinated compounds, terpene, and organic sulphides.The results of this study on the pilot-scale cell are then compared with those concerning three biogases from a municipal waste landfill: biogas (1) coming from waste cells being filled or recently closed, biogas (2) from all the waste storage cells on site, and biogas (3) which is a residual gas from old storage cells without aspiration of the gas. The analysis of the results obtained revealed: (i) a high emission of VOCs, principally alcohols, ketones and esters during the acidogenesis; (ii) a decrease in the alkane content and an increase in the terpene content were observed in the VOCs emitted during the production of methane; (iii) the production of heavier alkanes and an increase in the average number of carbon atoms per molecule of alkane with the progression of the stabilisation/maturation process were also observed.Previous studies have concentrated almost on the analysis of biogases from landfills. Our research aimed at gaining a more complete understanding of the decomposition/degradation of municipal solid waste by measuring the VOCs emitted from the very start of the landfill process i.e. during the acidogenesis and acetogenesis phases. 相似文献
648.
Hijosa-Valsero M Fink G Schlüsener MP Sidrach-Cardona R Martín-Villacorta J Ternes T Bécares E 《Chemosphere》2011,83(5):713-719
Seven mesocosm-scale constructed wetlands (CWs), differing in their design characteristics, were set up in the open air to assess their efficiency to remove antibiotics from urban raw wastewater. A conventional wastewater treatment plant (WWTP) was simultaneously monitored. The experiment took place in autumn. An analytical methodology including HPLC-MS/MS was developed to measure antibiotic concentrations in the soluble water fraction, in the suspended solids fraction and in the WWTP sludge. Considering the soluble water fraction, the only easily eliminated antibiotics in the WWTP were doxycycline (61 ± 38%) and sulfamethoxazole (60 ± 26%). All the studied types of CWs were efficient for the removal of sulfamethoxazole (59 ± 30-87 ± 41%), as found in the WWTP, and, in addition, they removed trimethoprim (65 ± 21-96 ± 29%). The elimination of other antibiotics in CWs was limited by the specific system-configuration: amoxicillin (45 ± 15%) was only eliminated by a free-water (FW) subsurface flow (SSF) CW planted with Typha angustifolia; doxycycline was removed in FW systems planted with T. angustifolia (65 ± 34-75 ± 40%), in a Phragmites australis-floating macrophytes system (62 ± 31%) and in conventional horizontal SSF-systems (71 ± 39%); clarithromycin was partially eliminated by an unplanted FW-SSF system (50 ± 18%); erythromycin could only be removed by a P. australis-horizontal SSF system (64 ± 30%); and ampicillin was eliminated by a T. angustifolia-floating macrophytes system (29 ± 4%). Lincomycin was not removed by any of the systems (WWTP or CWs). The presence or absence of plants, the vegetal species (T. angustifolia or P. australis), the flow type and the CW design characteristics regulated the specific removal mechanisms. Therefore, CWs are not an overall solution to remove antibiotics from urban wastewater during cold seasons. However, more studies are needed to assess their ability in warmer periods and to determine the behaviour of full-scale systems. 相似文献
649.
650.
Lauren A. Patterson Martin W. Doyle 《Journal of the American Water Resources Association》2009,45(1):237-252
Abstract: After a century of evolving flood policies, there has been a steady increase in flood losses, which has partly been driven by development in flood prone areas. National flood policy was revised in 1994 to focus on limiting and reducing the amount of development inside the 100‐year floodplain, with the goal of decreasing flood losses, which can be measured and quantified in terms of population and property value inside the 100‐year floodplain. Monitoring changes in these measurable indicators can inform where and how effective national floodplain management strategies have been. National flood policies are restricted to the spatial extent of the 100‐year floodplain, thus there are no development regulations to protect against flooding adjacent to this boundary. No consistent monitoring has been undertaken to examine the effect of flood policy on development immediately outside the 100‐year floodplain. We developed a standardized methodology, which leveraged national data to quantify changes in population and building tax value (exposure). We applied this approach to counties in North Carolina to assess (1) temporal changes, before and after the 1994 policy and (2) spatial changes, inside and adjacent to the 100‐year floodplain. Temporal results indicate the Piedmont and Mountain Region had limited success at reducing exposure within the 100‐year floodplain, while the Coastal Plain successfully reduced exposure. Spatially, there was a significant increase in exposure immediately outside the 100‐year floodplain throughout North Carolina. The lack of consistent monitoring has resulted in the continuation of this unintended consequence, which could be a significant driver of increased flood losses as any flood even slightly higher than the 100‐year floodplain will have a disproportionately large impact since development is outside the legal boundary of national flood policy. 相似文献