应用线性和非线性法求解有机物生物降解动力学参数

根据苯甲酸类化合物在水体中不同时间的生化需氧量，用线性和非线性合法对化合物生物降解随时间变化的动力学过程进行曲线拟合，得到各化合物2个数值不同的安全生化需氧量、生物降解速率常数和生物降解滞后期。根据各化合物2种不同的生物降解动力学模型所得到的生化需氧量拟合值与实测值的误差相比较，发现用非线性法拟合得到的有机物生物降解动力学模型，更符合化合物真实生物降解规律，因此用非线性法拟合化合物的生物降解动态变化，比用线性方法更精确。     

河流线型对河流自净能力的影响

为研究河流线型对河流自净能力的影响,选取5条具有不同河流线型的河涌进行研究,以弯曲度和分形维数表征河流线型,以TP、NH 3-N、NO 2-N、NO 3-N、COD Cr、TOC、DOC、叶绿素(Chlorophyll)和蓝绿藻藻蓝蛋白(BGA-PC)等9项水质指标沿程削减率表征河流自净能力,并分析各研究河段的悬浮微生物生物量和生物活性,探讨河流线型影响河流自净能力的作用机制。结果表明:多项水质指标沿程削减率随河流线型蜿蜒程度的增加而提升。在直立式浆砌石挡墙河段,河流线型通过提高悬浮微生物生物活性,进而增强河流自净能力,使TP、NH 3-N、NO 3-N、DOC、Chlorophyll和BGA-PC的沿程削减率显著提升;而在格宾石笼挡墙河段,河流线型通过增加悬浮生物生物量和提高生物活性,进而增强河流自净能力,使NO 2-N、COD Cr、TOC和DOC的沿程削减率显著提高。     

Apparent relationships between anthropogenic factors and climate change indicators and POPs deposition in a lacustrine system

Climate change and anthropogenic activities are expected to impact the environmental behaviors and fates of persistent organic pollutants(POPs), however, quantitative studies on these combined factors are scarce. In this study, dichlorodiphenyltrichloroethane(DDTs), polycyclic aromatic hydrocarbons(PAHs), and polychlorinated biphenyls(PCBs)were used as examples to identify how and when those factors may be related to the deposition of POPs in the sediment of Lake Chaohu, China, using generalized additive models(GAMs). Three historical trends of DDT, PAH, and PCB deposition were delineated in a dated sediment core encompassing ～100 years of historical record: a steady state or gradually increasing stage, a rapidly increasing stage, and a declining stage. The GAM results showed that aquatic total phosphorus(TP) concentrations and regional GDP(anthropogenic factors) were dominant contributors to POP accumulation rates in the lake sediment. The fitted relationships between air temperature and sedimentary DDT and PAH concentrations were linear and negative, while a positive linear relationship was found for PCBs, suggesting that Lake Chaohu may have become a net source for DDTs and PAHs, and a sink for PCBs, under a progressively warming climate.     

Evaluation of linear alkylbenzenesulfonate (LAS) biodegradability in sediment by solid‐phase extraction and HPLC analysis

The linear alkylbenzenesulfonate (LAS) sorption on environmental sediments has been known long ago. Their high concentrations reflect the massive input of these chemicals from household and industrial uses. However few attempts were made to identify biodegradation metabolites of LAS in sediment. In this report, a method for the determination of these compounds in sediment samples by high‐performance liquid chromatography (HPLC) is described. The first step of our work was performed by solid‐phase extraction with octadecyl‐bonded silica (C18) mini‐columns and provided a suitable recovery of LAS (90 ± 5%) and most metabolites. Furthermore, laboratory investigations led to study the behaviour of LAS in sediment. The environmental samples used for this purpose were collected from a pond (named étang de Bolmon) located in the French Mediterranean coast. Our results were in agreement with an aerobic biodegradation process of LAS that occurred only with high values of sediment redox potential and needed the samples to be vigorously shaken to ensure adequate mixing and suspension of particulate material. In a stagnant sediment or under anaerobic conditions, LAS is not degraded. p‐Sulfophenylacetic acid and p‐sulfocinnamic acid were evidenced as predominant metabolites and were found not to be persistent.     

Is “No-Threshold” a “Non-Concept”?

A controversy prominent in scientific literature that has carried over to newspapers, magazines, and popular books is having serious social and political expressions today: “Is there, or is there not, a threshold below which exposure to a carcinogen will not induce cancer?” The distinction between establishing the existence of this threshold (which is a theoretical question) and its value (which is an experimental one) gets lost in the scientific arguments. Establishing the existence of this threshold has now become a philosophical question (and an emotional one). In this paper I qualitatively outline theoretical reasons why a threshold must exist, discuss experiments which measure thresholds on two chemicals, and describe and apply a statistical method for estimating the threshold value from exposure-response data.     

A MATHEMATICAL MODEL FOR OPTIMUM DESIGN AND CONTROL OF METROPOLITAN WASTEWATER MANAGEMENT SYSTEMS1

ABSTRACT: A comprehensive mathematical model (Urban Wastewater Management Model) has been developed to continuously simulate time-varying wastewater flows and qualities in complex metropolitan combined sewerage systems. The model serves three functions: (1) assessment of existing or planned system performance in relation to other wastewater discharges in either a metropolitan or river basin area; (2) determination of the optium operation or automatic control of existing or planned systems during rainstorms; and (3) determination of the most economically feasible combination of design alternatives for improving or expanding existing systems to meet specified performance criteria. The model provides an efficient engineering tool for evaluating and controlling pollutant discharges from combined sewerage systems (including treatment plants) to receiving waters, while considering the time and spacial variations of rainfall and dry-weather flows and qualities as well as economic constraints.     

Regional multiresource models in a national framework

The design and integration of models projecting the effects of management on environmental systems is one step in the environmental planning process. Interactions between resources produced on the same unit of land under current and future management can be examined only when assumptions and processes of these dynamic environmental systems are quantified. Multiresource interaction models have generally been large and cumbersome while also suffering from an inadequate amount of detail. This article presents a conceptual framework for integrating individual resource models to project multiresource interactions at a regional scale. Land management impact projections require common definitions of the total land base and common definitions of management activities applied to the same land unit. A case example focusing on the resources of timber, forage, wildlife, fish, and water for the southern United States is presented.     

山地农业资源的时空性与持续利用研究：以陕西秦巴山地为例

山地是一种特殊的生态环境类型,受自然分异规律与人类经济活动的双重干预和影响,产生其特有的时空分异规律与层带组合格局。通过土地生态类型格局分析,可以揭示山地生态环境类型结构瑟功能的异质性和有序性,从而为探讨农业资源的时空性及其开发利用模式提供科学指导。     

高可靠复杂工业产品可靠性的仿真模拟

可靠性仿真方法是研究高可靠复杂工业产品的可靠性的有力手段之一 ,本文对建立工业产品可靠性仿真模拟的方法以及必要性进行了论述。     

The estimated reduction in the odds of loss-of-control type crashes for sport utility vehicles equipped with electronic stability control

INTRODUCTION: Using data from the NASS General Estimates System (GES), the method of induced exposure was used to assess the effects of electronic stability control (ESC) on loss-of-control type crashes for sport utility vehicles. METHOD: Sport utility vehicles were classified into crash types generally associated with loss of control and crash types most likely not associated with loss of control. Vehicles were then compared as to whether ESC technology was present or absent in the vehicles. A generalized additive model was fit to assess the effects of ESC, driver age, and driver gender on the odds of loss of control. In addition, the effects of ESC on roads that were not dry were compared to effects on roads that were dry. RESULTS: Overall, the estimated percentage reduction in the odds of a loss-of-control crash for sport utility vehicles equipped with ESC was 70.3%. Both genders and all age groups showed reduced odds of loss-of-control crashes, but there was no significant difference between males and females. With respect to driver age, the maximum percentage reduction of 73.6% occurred at age 27. The positive effects of ESC on roads that were not dry were significantly greater than on roads that were dry.