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581.
The sensitivity of an integrated model to assess the potential for wind-borne spread of foot-and-mouth disease (FMD) to variations
in key parameters controlling different physical and biological processes was evaluated. The estimated number of farms at
risk is sensitive to the virus strain used and the accompanying effective contact rate. The C Noville strain increased the
estimated number of exposed farms ranked as high and medium risk of being infected by a factor of 5, compared to the baseline,
based on the O UKG 2001 strain. The inclusion of a model for biological ageing of the virus can also have a significant effect
on the concentration patterns arising from transport and dispersion of the virus. Its inclusion has the practical advantage
of markedly reducing the time required for the calculations. The estimated number of farms affected by exposure to high and
medium virus concentrations is not grossly sensitive to attenuation caused by temperature or relative humidity effects. Changes
in susceptibility to infection, as determined by the parameter θ in the exposure-risk model, does not change the configuration of the virus plumes, but it does change the distribution of
farms at risk by risk category. These findings suggest that a good understanding of characteristics (excretion rates from
infected animals, susceptibility of different species to infection, virus survival, etc.) of the virus strain involved in
an FMD outbreak is necessary to provide a reliable assessment of the risk of wind-borne spread. In the event of an incursion
of FMD, provision for laboratory studies on the virus will be an essential component of the disease response and should be
factored into contingency plans.
相似文献
X. YangEmail: |
582.
Seasonal variation of polycyclic aromatic hydrocarbons in soil and air of Dalian areas, China: an assessment of soil-air exchange 总被引:1,自引:0,他引:1
The seasonal variations of concentrations of PAHs in the soil and the air were measured in urban and rural region of Dalian, China in 2007. In soil, mean concentrations of all PAHs in summer were larger than those in winter, whereas the concentrations of heavier weight PAHs in winter were larger than those in summer. Winter/summer concentration ratios for individual PAHs (R(W/S)) increased with the increase of molecular weight of PAHs in soil, indicating that PAHs with high molecular weight were more easily deposited to soil in winter than summer. In air, mean concentrations of all PAHs in winter were larger than those in summer. In comparison with the R(W/S) in soil, all the values of R(W/S) in air were larger than one indicating that the entire individual PAH concentrations in winter were larger than those in summer. The average concentration composition for each PAH compound in soil and air samples was determined and the seasonal change of PAH profile was very small. It was suggested that PAHs in soils and air had the same or similar sources both in winter and summer. The approach to the soil-air equilibrium was assessed by calculating fugacity quotients between soil and air using the soil and air concentrations. The calculated soil-air fugacity quotients indicated that soil acted as a secondary source to the atmosphere for all lighter weight PAHs (two-three rings) and it will continue to be a sink for heavier weight PAHs (five-six rings) in the Dalian environment, both in winter and summer. Medium weight PAHs (four-five rings) were close to the soil-air equilibrium and the tendency shifted between soil and air when season or function region changed. The fugacity quotients of PAHs in summer (mean temperature 298 K) were larger than those in winter (mean temperature 273 K), indicating a higher tendency in summer than winter for PAHs to move from soil to air. The variation of ambient conditions such as temperature, rainfall, etc. can influence the movement of PAHs between soil and air. Most of the fugacity quotients of PAHs for the urban sites were larger than that for the rural site both in winter and summer. This phenomenon may be related with that the temperatures in urban sites were higher than those in the rural site because of the urban heat island effect. 相似文献
583.
Comparative studies on seasonal variations of metazooplankton in waters with different eutrophic states in Lake Taihu 总被引:1,自引:0,他引:1
A comparative study on the metazooplankton community was conducted in three different eutrophic areas, including Lake Wulihu, Meiliang Bay and the central open water area, in Lake Taihu from Oct. 2003 to Sep. 2004. Forty metazooplankton species were identified in Lake Wulihu, 37 in Meiliang Bay, and 34 in the central open water area. The annual average abundance of metazooplankton was 218 ind. l(-1) in the central open water area, 309 ind. l(-1) in Meiliang Bay, and 384 ind. l(-1) in Lake Wulihu. In Lake Wulihu, rotifers, Brachionus calyciflorus and Brachionus angularis, were the dominant species, which contributed 20.9% and 17.2% to the total metazooplankton abundance. Bosmina coregoni and Ceriodaphnia cornuta were the dominant species, contributing 20.4% and 11.3% of the total in Meiliang Bay, and contributing 21.6% and 16.2% of the total in the central open water area. There was a significant positive relationship between rotifers abundance and Secchi transparency. Cladoceran and copepod abundance were positively correlated with total phosphorus and water temperature. Our results show that structures of metazooplankton community differ between the three lake areas with different eutrophic states in Lake Taihu. 相似文献
584.
C. L. Yang Z. F. Wu H. H. Zhang R. P. Guo Y. Q. Wu 《Environmental monitoring and assessment》2009,159(1-4):381-391
In this study, the spatial distributions of soil lead (Pb) concentration in three horizontal soils in Guangdong, China, were surveyed and analyzed using geostatistics and geography information systems (GIS). Findings indicated that the Pb geometric mean concentration of 23.3 mg/kg in surface soils was found to be higher than those in global soils, which ranged from 2.3–235 mg/kg. In addition, the Pb geometric mean concentrations from A- to C-horizon were found to be 23.3, 27.2, and 28.6 mg/kg, respectively. The classification of a soil Pb environmental risk in an area was likewise presented based on the different levels of environmental quality of Pb and was done by GIS technology. Accordingly, there is a higher local concentration of Pb in the surrounding areas of Guangzhou where there is higher population density and in the north of Guangdong, which is a historic mining area. The results obtained by the environmental risk assessment reveal that about 46% of total surveyed area was above the background value, that is, 2.7% of the total area was at risk of pollution. 相似文献
585.
586.
Spatial and temporal distribution of polycyclic aromatic hydrocarbons (PAHs) in sediments of the Nansi Lake, China 总被引:2,自引:0,他引:2
Hong-Li Li Hong Gao Chen Zhu Guo-Gang Li Fan Yang Zheng-Yu Gong Jun Lian 《Environmental monitoring and assessment》2009,154(1-4):469-478
Polycyclic aromatic hydrocarbons (PAHs) were measured in surface sediments and dated core sediments from the Nansi Lake of China to investigate the spatial and temporal distribution characteristics. The concentrations of 16 kinds priority PAH compounds were determined by GC-MS method. And 210Pb isotope dating method was used to determine the chronological age of the sediment as well as the deposition rate. The results indicated that the total PAHs concentration ranges in surface and core sediment samples were 160 ~32,600 and 137 ~ 693 ng/g (dry wt.), respectively. The sediment rate and the average mass sedimentation were calculated to be 0.330 cm·year???1 and 0.237 g·cm???2·yr???1 and the sediment time of the collected core sample ranged from 1899 to 2000. The peak of PAH concentrations came at recent years. The source analysis showed PAHs mainly came from the contamination of low temperature pyrogenic processes, such as coal combustion. The PAHs concentrations were lower than ERL and LEL values for most collected samples. However, in several surface sediment samples especially in estuary sites, the PAHs concentrations were not only higher than ERL and LEL values, but also higher than ERM values. 相似文献
587.
In this study, an interval-fuzzy two-stage chance-constrained integer programming (IFTCIP) method is developed for supporting
environmental management under uncertainty. The IFTCIP improves upon the existing interval, fuzzy, and two-stage programming
approaches by allowing uncertainties expressed as probability distributions, fuzzy sets, and discrete intervals to be directly
incorporated within a general mixed integer linear programming framework. It has advantages in uncertainty reflection, policy
investigation, risk assessment, and capacity-expansion analysis in comparison to the other optimization methods. Moreover,
it can help examine the risk of violating system constraints and the associated consequences. The developed method is applied
to the planning for facility expansion and waste-flow allocation within a municipal solid waste management system. Violations
of capacity constraints are allowed under a range of significance levels, which reflects tradeoffs between the system cost
and the constraint-violation risk. The results indicate that reasonable solutions for both binary and continuous variables
have been generated under different risk levels. They are useful for generating desired decision alternatives with minimized
system cost and constraint-violation risk under various environmental, economic, and system-reliability conditions. Generally,
willingness to take a higher risk of constraint violation will guarantee a lower system cost; a strong desire to acquire a
lower risk will run into a higher system cost. 相似文献
588.
Behaviour of selected endocrine-disrupting chemicals in three sewage treatment plants of Beijing, China 总被引:3,自引:0,他引:3
Haidong Zhou Xia Huang Xiaolin Wang Xiahui Zhi Chengdui Yang Xianghua Wen Qunhui Wang Hiroshi Tsuno Hiroaki Tanaka 《Environmental monitoring and assessment》2010,161(1-4):107-121
Occurrence and fate of eight kinds of selected endocrine-disrupting compounds (EDCs) in three sewage treatment plants (STPs) of Beijing, China was investigated. These EDCs, composed of 4-octylphenol (4-OP), 4-n-nonylphenol (4-n-NP), bisphenol A (BPA), estrone (E1), 17α-estradiol (17α-E2), 17β-estradiol (E2), estriol (E3) and 17α-ethinylestradiol (EE2), in every step of STPs, were simultaneously analysed by gas chromatography/mass spectrometry after derivatisation. All the EDCs were detected in the influents of three STPs, and BPA was the most abundant compound. The concentrations of EDCs ranged from 36.6 ng/l of 17α-E2 (STP C) to 1342.3 ng/l of BPA (STP B) in the influent sewages and from below limits of detection of E2 and E3 (STP C) to 142.5 ng/l of E1 (STP B) in the effluent sewages. The STPs could not remove alkylphenols effectively from the aqueous phase with less than 40% reduction. BPA decreased over 90%, and steroid estrogens achieved considerable reductions from 64.8% of E2 to 94.9% of E3. Generally, biological treatment was more effective in removing alkylphenols, BPA and natural estrogens from the aqueous phase than primary treatment. However, the synthetic estrogen, EE2, was mostly removed by the primary treatment with about 63.5% reduction. It is the first time that the concentration of 17α-E2 in the sewage of China was reported in this paper. The compound might have a bearing with the waste effluents of dairy farms around urban area of Beijing. 相似文献
589.
Investigation of heavy metals in sediments and Manila clams Ruditapes philippinarum
from Jiaozhou Bay, China 总被引:1,自引:0,他引:1
Xiaoyu Wang Yi Zhou Hongsheng Yang Qing Wang Shilin Liu 《Environmental monitoring and assessment》2010,170(1-4):631-643
Manila clams (Ruditapes philippinarum) and sediments were collected bimonthly during 2007 at five locations in Jiaozhou Bay near Qingdao, China, to determine heavy metal concentrations and to assess the validation of R. philippinarum as a metal biomonitor. Concentrations of heavy metals in clam soft tissues ranged between 0.75 and 3.31, 0.89 and 15.20, 5.70 and 26.03, 52.12 and 110.33, 10.30 and 72.34, 9.64 and 28.60, and 3.15 and 52.75 μg g???1 dry weight for Cd, Pb, Cu, Zn, Mn, Cr, and Ni, respectively. Most of the highest values occurred at the northeast bay and the lowest values occurred at the western part. Regarding seasonal variation, relatively high tissue metal concentrations were observed during October or December. A similar pattern was also found in habitat sediments. There was a strong correlation between the concentrations of Cd, Pb, Zn, Mn, Cr, and Ni in soft tissues and surrounding sediments. It is indicated that R. philippinarum could be used as a biomonitor for heavy metal contamination in Jiaozhou Bay. 相似文献
590.
Ryu C Phan AN Yang YB Sharifi VN Swithenbank J 《Waste management (New York, N.Y.)》2007,27(6):802-810
Recent developments in national recycling and re-use programmes for municipal waste have led to segregation of an increasing proportion of waste to enhance material recovery. Several of the segregated streams contain materials that can not viably be re-used or recycled but can be used for energy recovery. In this study, the combustion of cardboard and waste wood was investigated in a small-scale packed bed reactor in order to provide fundamental data for the design/operation of moving bed furnaces. Key parameters of combustion including the ignition and burning rates were evaluated for various air flowrates and compared to the modelling results. Two successive stages of combustion were identified for both samples: the propagation of ignition front into the bed and combustion of the fuel above the ignition front. The burning rate of cardboard reached a peak of about 300 kg/m(2)h at the air flowrate of 936 kg/m(2)h and decreased at higher air flowrates. For waste wood, both the ignition and burning rates increased in the tested range of the air flowrate up to 702 kg/m(2)h, of which the values were very close to those for the cardboard. The model prediction was in good agreement with the test results for waste wood. However, the burning rate for cardboard was under-predicted due to strongly irregular shapes of the fuel. 相似文献