RIDGE REGRESSION TECHNIQUES APPLIED TO LANDSAT INVESTIGATION OF WATER QUALITY IN LAKE OKEECHOBEE1

ABSTRACT: Landsat radiance values were processed at two different (single and double) levels of accuracy to estimate chlorophyll a, turbidity, and suspended sediment in Lake Okeechobee, Florida. Both ordinary least square and ridge regression analyses were used to establish a relationship between water quality parameters and Landsat radiance. Radiance measurements made at greater precision (double level) gave a better solution in this application. The ridge regression analysis for double level not only can reduce the total mean square error about 13–20 percent and confidence interval about 6–28 percent as compared to ordinary least square analysis, but it can also change the interpretation of analysis results.     

STOCHASTIC MODELING OF MONTHLY AND DAILY RAINFALL SEQUENCES1

ABSTRACT: A monthly model and two daily models (I and II) are presented for the purpose of generating monthly and daily rainfall sequences in the Quae Yai river basin in Thailand. Performance of the models are evaluated by comparing the statistical parameters of the generated sequences with those from historical data. For monthly generation, Thomas-Fiering model worked satisfactorily in spite of the monthly correlations being weak, if any. Daily Model I, which assumes no persistence between daily rainfall amounts within the wet spells, could not preserve some important parameters regardless of the simplicity in model construction. Application of multi-state transition probability matrix model gave good results, although the user has to modify some parameters looking at the performance of the model for each historical record.     

ESTIMATING THE SUSPENDED SEDIMENT LOAD IN RESERVOIRS1

ABSTRACT: The total suspended sediment loads of four north Mississippi reservoirs were determined from measurements of concentrations of suspended sediment in a vertical profile at several locations on each reservoir made during the year. These data were combined with the stage-height and known stage-volume relationships for each reservoir in a numerical integration to determine the total suspended sediment in the water body. Total suspended sediments were estimated using the product of the suspended sediment concentration in the surface water by the appropriate reservoir volume. The averaged ratios of the estimated to measured suspended sediment loads for each reservoir exceeded 0.90. Since the concentration of suspended sediments in surface waters of north Mississippi reservoirs has been shown as highly correlated with spectral reflectance, estimating the total suspended sediment of these reservoirs using remotely sensed spectral reflectance data is possible.     

Air quality assessment along Dhanbad - Jharia road

Road ambient air pollution status along Dhanbad – Jharia road isstudied and presented in this article. The selection of this areais made considering the importance of the road in Dhanbad district and the nature of activities taking place along the road, which reflect that the portion of road upto Dhansar can be considered as having commercial areas on both sides and that from Dhansar to Jharia as having industrial areas on both sides.For the assessment of the ambient air quality along the road monitoring is done at the following five locations: Indian Schoolof Mines (ISM), main gate; Bankmore; Dhansar police check post; Dhansar opencast project agent office and a residential house beside the Rajapur opencast project. The location of ISM, maingate is specially chosen as this represents a commercial shoppingcomplexes and the situation can be compared with that at Bankmore. Monitoring of ambient air quality is done following thestandard procedure prescribed in IS: 5182. In addition the concentration of lead, zinc, copper, iron, manganese, cadmium metals in SPM is also monitored. The ambient air quality is monitored in the months of September and November 1999, respectively, to represent monsoon and winter seasons. The SPM concentration observed at all the five locations in the winterseason is more than the permissible limits for commercial andindustrial areas. However, in the monsoon season, the SPM concentration is higher than the permissible limit at the twocommercial locations, i.e., ISM gate and Bankmore, while it isless than the prescribed limit for industrial areas at the remaining three locations. At the ISM gate and Bankmore the SPM generation is mainly by vehicular traffic while at other three locations it was in addition due to mining and other activities.     

Contamination of Oxygen-Consuming Organics in the Yellow River of China

Contamination of oxygen-consuming organics (OCOs) was one of the most serious problems in the Yellow River of China. This study was conducted to analyze monitoring of the data on OCOs contamination for the river in 1980 and during 1992–1999 as well as examining the effect of suspended solids (SS) on chemical oxygen demand (COD_Mn) and biochemical oxygen demand (BOD₅) of river water. Several significant results have arisen from the study. First, COD_Mn and BOD₅ of the river water showed an increasing trend from the upper to the lower reaches of the mainstream. BOD₅ values of river water in 1992 were significantly higher than those in 1980 and showed an increasing trend during 1992–1999. Second, OCOs in river water of the mainstream was attributed mainly to point sources; the ratio of point to non-point sources of BOD₅ was about 2.81. The load from point sources showed an increasing trend during 1992–1998. In contrast, the load from non-point sources manifested a decreasing trend during this period; this was caused by the decreasing trend of SS content in river water. The total load of BOD₅ from point and non-point sources displayed an increasing trend during 1992–1998. Third, as the humic substances in SS can hardly be biologically oxidized in natural conditions but can be oxidized by chemical oxidants such as potassium permanganate, COD_Mn was not suitable for being regarded as a parameter reflecting the pollution degree of OCOs in river water with a high SS content.     

Method to analyze the regional life loss risk by airborne chemicals released after devastating earthquakes: A simulation approach

Widespread chemical plants render human life more vulnerable to major natural disasters such as earthquakes. Recognizing the potential cascading threats initiated by a devastating earthquake, a general methodology for assessing the life loss risks introduced by airborne hazardous chemical dispersion following seismically induced chemical release (SICR) was proposed. With a 600 km × 600 km region in North China as a demonstrative study area, the dispersion of ammonia released from multiple relevant chemical plants that were supposed to be damaged by a devastating earthquake was simulated in a probabilistic manner. Using an ammonia toxicity-fatality relationship and its toxicity concentration threshold, regional life loss and spatial spread were evaluated. The life loss risk was found to be non-prominent but would be very contingent on unfavorable meteorological conditions. Non-parametric correlation analysis revealed that the respective effects of meteorological mixing parameters on the risk exhibit new features in a disaster context, that is, stronger mixing would cause elevation of risk in a region. This preliminary research implied that the risk of chemical-induced life loss after a devastating earthquake deserves attention and a thorough uncertainty evaluation in the future.     

地铁运营突发事件应急响应模式的马尔科夫链分析

为研究城市轨道交通网络化运营线路的风险传导规律和耦合关系,构建基于随机Petri网的同构马尔科夫链模型。通过模型分析突发事件应急响应模式中线路之间的相互影响,以及各线路启动突发事件应急响应模式对整个系统稳态的影响。结果表明,用该模型可从数学上研究城市轨道交通运营线路之间的传导规律和耦合关系,找出影响整个应急指挥系统效率的关键因素,最终提高地铁应对突发事件的能力。     

风浪扰动对太湖水体中砷在水相-悬浮物相之间分配的影响

在太湖冬季不同风速下(0.8、1.8、2.7、3.2、4.0 m·s-1)采集了不同深度(水深0.1、1.0和1.8 m,分别记为上、中和下层)的水样,测定了水体和悬浮物中的砷含量及水质参数,计算了砷在两相之间的分配系数,以期了解在太湖生物活动最低的阶段,风浪扰动作用对砷在水相和悬浮物相之间分配的影响.结果显示,随着风浪作用的加强,水体总砷含量有所增加,相应的悬浮物总砷含量及砷的分配系数降低,说明风浪作用可以降低悬浮物吸附砷的能力,以至于促进砷从悬浮物中的释放,进而使水体中的溶解态砷增加.相关性分析及变化趋势比较分析发现,砷分配系数的降低与在风浪扰动的影响下悬浮物浓度和溶解氧的增加,以及叶绿素a浓度的下降有关.不同风速下各参数的垂向分布变化显示,风浪扰动对中下层的砷分配系数以及中层的悬浮物砷含量影响较大;风速变大时,中层溶解态砷含量升高,上层与下层溶解态砷含量降低;而风浪扰动作用对水体总砷的分层变化影响不大.悬浮物浓度、砷浓度及分配系数均在3~4 m·s-1风速下发生变化,且呈现与之前不同的分层特征.4 m·s-1可能是一个临界风速,在4 m·s-1以上的风速下风浪占主导作用,而4 m·s-1以下是湖流与风浪共同作用的结果.     

鄱阳湖悬浮颗粒物絮凝沉降典型藻类的动力学研究

为了探讨鄱阳湖水动力条件改变引起的悬浮颗粒物浓度变化可能导致的鄱阳湖浮游植物群落结构的变化,本文研究了鄱阳湖悬浮颗粒物絮凝沉降3种典型藻类的动力学过程.以铜绿微囊藻(蓝藻)、四尾栅藻(绿藻)和菱形藻(硅藻)为研究对象、鄱阳湖采集沉积物为悬浮颗粒物,使用混凝试验搅拌仪模拟动力学条件,在颗粒物投加量为20 mg·L-1时分别研究了静置沉降时间、扰动强度和扰动时间对颗粒物絮凝沉降藻细胞的影响.结果表明,絮凝沉降效率:蓝藻绿藻硅藻.在扰动强度为20 s-1、扰动时间为30 min时,0.5~4 h静置沉降时间均促进3种藻类的絮凝沉降.绿藻和硅藻的絮凝沉降效率随着静置沉降时间的延长而降低,前0.5 h的絮凝沉降效率最大;而蓝藻的絮凝沉降效率变化无明显规律.扰动时间和静置沉降时间均为30 min时,随着扰动强度在2~40 s-1增加时,3种藻的絮凝沉降效率逐渐增大.扰动强度为20 s-1、静置沉降时间为30 min时,5~60 min扰动时间均促进藻细胞的絮凝沉降,并且随着扰动时间的增加,絮凝沉降效率呈先增大后降低的趋势.30 min为蓝藻絮凝沉降的最佳扰动时间,絮凝沉降效率为12.56%;45 min为绿藻和硅藻絮凝沉降的最佳扰动时间,絮凝沉降效率分别为11.93%和7.54%.因此,水动力条件的改变可以引起悬浮颗粒物与藻类的絮凝沉降效率发生变化,从而对藻类的群落结构以及水华发生规律产生影响.     

电吸附水处理技术(EST)对污水悬浮物去除效果研究

为了研究电吸附水处理技术(EST)对污水悬浮物的去除效果,本文采用电吸附水处理技术对生活污水中悬浮物进行处理分析,结果表明电吸附水处理系统对悬浮物的去除效果较好,去除率达到74.07%,而电吸附模块本身对悬浮物去除率仅为14.29%,氯离子、进水中悬浮物的浓度及进水中的硬度值均对悬浮物去除效率没有影响。因此,电吸附水处理技术可作为污水处理的一种新型有效方法。