A complete record derived from a core dated both by 210Pb and 137Cs chronologies from Lake Ngoring at the headwater areas of the Yellow River provides new insight into the changing atmospheric deposition of trace metals including Cd, Cr, Cu, Ni, Pb, and Zn. This study showed that there was an inflection in the early 1960s, before which both fluxes and contents of Cd, Ni, Pb, and Zn remained relatively steady or slowly increased, and thereafter continued increases both in fluxes and contents were found. Taking Pb as an example, the flux increased from 0.13 (before 1960) to 0.25 mg m?2 a?1 (averaged 1963–2006). According to atmospheric flux calculations using Al as a reference element, atmospheric fluxes of trace metals generally showed a rapid increase and peaked in recent years, closely following the historical economic development of the neighboring region, mainly for Qinghai and Gansu provinces. The atmospheric inventory for Zn was the highest, reaching 1.068 g m?2, while the lowest was for Cd, at only 0.079 gm?2. The percentage proportions of atmospheric deposition for Cd, Ni, and Zn were 37, 12, and 8.7 %, respectively. Hence, the atmospheric contribution to the trace metal content via long range transport is not negligible when considering input of materials to lake ecosystems. 相似文献
Nowadays, selection of the suitable disposal site in municipal solid waste (MSW) management has become a challenge task for the municipal authorities, especially in fast-growing areas. Site selection can be viewed as a complicated multi-criteria decision-making (MCDM) problem requiring consideration of multiple alternative solutions and conflicting quantitative and qualitative criteria. In this paper, linguistic variables, which can be expressed as trapezoidal fuzzy numbers, are used to assess the ratings and weights for the selection criteria. The ordered weighted averaging operator is utilized to transform the fuzzy decision matrix into crisp values considering the decision maker’s attitudinal character. For selecting the best site, the extended VIsekriterijumska optimizacija i KOmpromisno Resenje (VIKOR) method is applied to determine the priority ranking of alternatives. As a result, a hierarchy MCDM model based on fuzzy set theory and VIKOR method is proposed to deal with the site selection problems in the MSW management system. An empirical study in Shanghai, China, is provided and comparison with the existing approach is conducted to illustrate the applicability and benefits of the proposed method. 相似文献
With the increasing exposure of populations and economy to natural hazards, the spatio-temporal characteristics of extreme rainfall remain a key subject of study. Based on annual maximum rainfall (AM) and peaks over threshold rainfall series at 30 meteorological stations during 1960–2011 in the Huai River Basin (HRB), spatio-temporal characteristics of extreme rainfall are analyzed through regional frequency analysis method using L-moments. The accuracy and uncertainty analysis of quantile estimations are also carried out, and the regional and at-site frequency analyses are compared. Results indicate the following: (1) During 1960–2011, AM precipitation at 20 stations in the HRB shows an increasing trend, while at the other 10 stations, it shows a decreasing trend. And both the increased and decreased trends are not significant. (2) The HRB can be categorized into three homogeneous regions via cluster analysis. For both at-site and regional frequency analyses, the root mean square error values increase with the increase in return periods. The estimations are reliable enough for the return periods of less than 100 years. The quantile estimates of large return period from regional frequency analysis are more accurate and have smaller uncertainty than those from at-site frequency analysis. (3) Extreme precipitation in the HRB concentrates in the upstream of the Huai River and YiShuSi water system in the east of the HRB. Generally, the area with extreme precipitation, especially the upper reaches of the Huai River and Yimeng Mountain areas, also has large standard variations of extreme precipitation, which will increase the risk of natural hazards. 相似文献
With the increasing occurrence frequency of emergency events, emergency management (EM) has been a very important issue in management science. One of the major activities of EM is to evaluate and select the most desirable emergency alternative(s). This paper proposes a new framework combining the analytic network process (ANP) method, the decision-making trial and evaluation laboratory (DEMATEL) technique, and 2-tuple linguistic technique for order preference by similarity to an ideal solution (TL-TOPSIS) method to solve the emergency alternative evaluation and selection problem. This study has been done in three stages. In the first stage, we use DEMATEL technique to obtain the network relation map (NRM) among emergency alternative evaluation criteria or sub-criteria. In the second stage, we use ANP method to calculate the global weight of each sub-criterion based on the NRM among emergency alternative evaluation sub-criteria. In the third stage, the ratings of emergency alternative with respect to each sub-criterion are described by linguistic items, and the TL-TOPSIS method is used to rank the emergency alternative. Finally, a practical example of urban fire emergency alternative selection is given to illustrate the application of the proposed framework.