广州市水资源人口承载力研究

水资源是城市可持续发展的重要基础,科学分析城市水资源承载力与经济社会发展的关系,并基于此协调人口与水资源的关系,建立适应于城市水资源承载力的人类生活与生产方式,将有助于实现城市经济社会可持续发展。本文的计算思路是在对广州市水资源现状进行分析的基础之上,构建广州市水资源承载力评价指标体系,划定水资源承载力等级,对市各辖区相应的水资源承载力进行评价,同时结合广州市人口规划预测的人口数量及未来的供水能力等进行预测,以此提出提升水资源承载力的相关政策和措施。     

黑龙江省饮用水水源地基础环境现状

饮用水的安全与否已经成为威胁人们健康的重要因素,保护饮用水水源地、保障人民饮水安全已经成为事关国家安全、社会稳定的重要工作。本文介绍了黑龙江饮用水水源地的基本情况、特点以及存在的问题,并提出了相应的对策和建议,希望可以为改善全省饮用水水源地水质,保障人民饮水安全提供一些帮助。     

Case study on nitrogen and phosphorus emissions from paddy field in Taihu region

The agricultural non-point source pollution by nitrogen (N) and phosphorus (P) loss from typical paddy soil (whitish soil, Bai Tu in Chinese) in the Taihu Lake region was investigated through a case study. Results shown that the net load of nutrients from white soil is 34.1 kg ha(-1) for total nitrogen (TN), distributed as 19.4 kg ha(-1), in the rice season and 14.7 kg ha(-1) in the wheat season, and for total phosphorus (TP) 1.75 kg ha(-1), distributed as 1.16 kg ha(-1) in the rice season and 0.58 kg ha(-1) in the wheat season. The major chemical species of N loss is different in the two seasons. NH4-N is main the form in the rice season (53% of TN). NO3-N is the main form in wheat season (46% of TN). Particle-P is the main form in both seasons, (about 56% of TP). The nutrient loss varied with time of the year. The main loss of nutrients happened in the 10 days after planting, 64% of TN and 42% of TP loss, respectively. Rainfall and fertilizer application are the key factors which influence nitrogen and phosphorus loss from arable land, especially rainfall events shortly after fertilizer application. So it is very important to improve the field management of the nutrients and water during the early days of planting.     

Occupational risks and the value and modelling of a measurement of severity

In studies of occupational risks, severity, which is a component of the estimation of every risk, appears as a multifaceted entity assessable according to numerous criteria. A method of measuring the degree of severity of the consequences of potentially dangerous events would be of undeniable value to organisations seeking to improve their understanding of the complexity of such events. The need to control severity is highlighted by scientifically acquired improvements in the understanding of occupational risks, by certain new regulatory obligations in Europe, and by some requirements in the financial management of organisations. We put forward a statistical way of integrating several constituent elements of severity and hence of determining a relevant, synthetic, one-dimensional index. This is achieved by means of principal component analysis (PCA), which is used here to calculate a resultant severity, as in some physical measurements. We also investigate how severity may be statistically modelled, with the aim of contributing to the quantitative assessment of occupational risks. The choice of parametric models is detailed and illustrated by the search for a suitable model for workplace accidents in an organisational setting. The practical value of modelling severity is two-fold. First, one is able to study the distribution of the numerical values of severity over a continuum (a theoretically infinite numerical set) rather than through a limited number of arbitrarily defined categories. Second, with a generally applicable parametric model, one can estimate the law of probability of a measurement of severity in a particular situation, notably recent or new. Lastly, the statistical concept of risk curve is defined and discussed. The goal is to incorporate the severity component into the risk assessment in the form of a probability law, thus circumventing the difficulties associated with an analysis of scenarios.     

COMPARISON OF DESIGN STORM CONCEPTS USING CONTINUOUS SIMULATION WITH SHORT DURATION STORMS1

ABSTRACT: The objectives of this paper were to test the ability of various design storm distributions to simulate the actual rainfall pattern and to compare the runoff rates used in the design of stormwater management devices in the State of Florida using continuous simulation approach. The analyses were performed for four gaged stations to evaluate the applicability of design storm distributions in different parts of the State of Florida. The approach used in this study compared the peak runoff rates from design storms based on the various distributions to those that would result from actual rainfall events. A series of continuous runoff rates were developed through the use of actual fifteen-minute recorded rainfall data, Horton type infiltration decay and recovery rate, and a continuous simulation model. The runoff rates were analyzed using frequency distributions to obtain peak runoff rates associated with different return periods based on the assumption that the continuous simulation approach closely predicts the actual runoff rates from the gaged stations. The results show that the behavior of the design storm distributions varies for different watershed characteristics in different parts of the state. The study also suggests that in general the Florida Department of Transportation and the Suwanne River Water Management (FDOT/ SRWMD) distributions appeared to agree with the continuous simulation results.     

Seasonal abundance and toxicity of the dinoflagellate Gambierdiscus spp. (Dinophyceae), the causative agent of ciguatera in Tahiti, French Polynesia

The benthic dinoflagellate Gambierdiscus spp. is the primary causative agent of ciguatera fish poisoning in French Polynesia. However, the initiation of ciguatera outbreaks and the factors that control ciguatoxin production in this dinoflagellate are still poorly understood. In this paper, we present some original data concerning the seasonal abundance and toxicity of natural populations of Gambierdiscus spp. based on a long-term survey in a ciguateric site of the island of Tahiti. From February 1993 to December 1997, Gambierdiscus spp. population densities were monitored weekly in the Atimaono barrier reef of Papara in relation to temperature and salinity. Densities peaked at 4992 cells g⁻¹ in October 1994 and constituted ≥1000 cells g⁻¹ on several occasions. A total of 58 blooms were recorded in the area, of which 65% occurred in 1995 and 1996 alone. Our data confirmed the high endemicity of Gambierdiscus spp. in the Papara area. Refined analysis of our raw data by a principal-component analysis of processes (PCAP) revealed a seasonality in cell densities from February 1993 to May 1995. During this period, Gambierdiscus spp. populations tended to reach maximum abundance at the beginning and end of the hot season. In contrast, salinity did not appear to be a determining factor in the seasonal abundance of this dinoflagellate. The noticeable increase in both peak densities and frequency of blooms further noticed in 1995 and 1996 was preceded by unusually high water temperatures in January to April 1994, concomitant with a severe coral-bleaching episode. During the course of the study, a total of 303 × 10⁶ cells obtained from 48 successive blooms was harvested. Toxicity screening revealed that toxin production was maximum from October 1994 through December 1996. No correlation was found between toxicity of these blooms and their biomass nor the seasonal pattern of temperatures. It is suggested that the toxicity of naturally-occurring blooms of Gambierdiscus spp. and, consequently, the severity of ciguatera incidents in a given area, is mainly dependent on the clonal nature of cells which coexist within local populations of this dinoflagellate. Received: 12 October 1998 / Accepted: 15 June 1999     

Degradation pathways of PCBs upon UV irradiation in hexane.

The photodegradations of eight individual PCB congeners (5, 31, 52, 77, 87, 126, 138, 169) in hexane have been investigated employing a mercury lamp. All degradation reactions of the above mentioned PCB congeners are of the pseudo first order. The principal products of PCB decomposition are the less chlorinated biphenyls, and no PCB-solvent adducts are found. Symmetrical and coplanar PCB congeners show lower photoreactivities. The reactivities of the chlorine atoms at various positions of PCB rings are generally in the order: ortho > meta > para. Photodechlorinations occur mainly on the more substituted rings, when the numbers of chlorine atoms on the two phenyl rings are unequal. During photodegradation, some coplanar PCB congeners are formed, which make the TEQ of solutions to decrease slowly or even to increase.     

5种多溴联苯醚同系物对海洋饵料藻(亚心型扁藻和盐生杜氏藻)的急性毒性

本研究选择5种多溴联苯醚同系物(BDE-28、BDE-47、BDE-99、BDE-153和BDE-209)对2种海洋饵料藻(亚心型扁藻和盐生杜氏藻)进行急性毒性试验。96 h半抑制浓度(96 h EC50)计算结果表明,BDE-28 和BDE-47的毒性较高,随溴原子取代数的增加,PBDE同系物对海洋饵料藻的毒性呈下降趋势,5种PBDE同系物对亚心形扁藻、盐生杜氏藻的96 h EC50由小及大依次为:BDE-28(128,75 g/L)、BDE-47(114,120 g/L)、BDE-99(383,572 g/L)、BDE-153(996,1249 g/L)和 BDE-209(2056,1868 g/L)。目前全球近岸海水中PBDEs浓度尚不会对海洋饵料藻产生急性毒性。海洋微藻对同种PBDE同系物的敏感性差异较大(96 h EC50相差1~2个数量级),为客观评价PBDEs的海洋生态风险性,应研究PBDEs对更多种类微藻的毒性效应。     

火电厂大气污染物排放标准对区域酸沉降影响的数值模拟

设计了火电厂实施2003版排放标准和2011版排放标准两种排放情景,运用Models-3/CMAQ模型系统分别模拟各情景到2015年的硫、氮沉降量,探讨2011版火电排放标准对我国大陆地区酸沉降的影响.研究表明,2011版火电标准能够有效改善我国的硫沉降状况,相比于实施2003版标准,2011版标准实施后至2015年我国大陆硫沉降总量降低了18.58%,年均硫沉降强度大于3.2t/km2的面积减少了86.40%;2011版火电标准对我国氮沉降状况也起到了一定的改善作用,标准实施后到2015年我国大陆氮沉降总量降低了9.28%,年均氮沉降强度大于4.0t/km2的面积减少了27.27%.