Application of a multi-step computation scheme to an intratidal estuarine water quality model

A computation scheme, which involves multi-step computation of the decoupled mass-balance equations in water quality models, was proposed by Park and Kuo (1996. Water Res. 30, 2255–2264). Using a simple hypothetical model, they explained the concept and demonstrated the accuracy and computational efficiency of the multi-step scheme. This paper describes the concept and the implementation of the multi-step computation scheme in a more generalized format for both intratidal and intertidal estuarine water quality models. The scheme is applied to a prototype estuary using a laterally-integrated two-dimensional intratidal model. The computational efficiency of the scheme is demonstrated by comparing the model results using the multi-step scheme with those using the traditional single-step explicit numerical solution of the kinetic processes.     

Encapsulation behaviors of metals in slags containing various amorphous volume fractions

In this study, a melting process with addition of SiO2 was applied to treat incinerator fly ash. To describe the encapsulation behaviors of metals quantitatively, the amorphous volume fraction (AVF) of slags was initially determined. Vitrification appeared to reduce the mobility of Cr, Cu, Mn, and Ni instead of significantly immobilizing Cd, Pb, and Zn. It was verified that SiO2 enhanced the formation of an amorphous glassy structure. With the increase of SiO2, the crystalline phases would gradually diminish and transform into a higher silica-connected species. During the formation of slag matrix, Al, Ca, and Mg could modify the glass network, and consequently the encapsulation behaviors of these species would noticeably affect the chemical stability of slags. Significant immobilization of crust metals could be achieved only when a more compact and interconnected amorphous glass network was formed. Hence, it indicated that a higher AVF silica-based slag had a better potential to resist acid attack. In conclusion, for environmental protection, it is important to investigate the correlation between the encapsulation behaviors of metals and the crystalline characteristics of slag structure.     

An investigation on the potential of metal recovery from the municipal waste incinerator in Taiwan

This study aimed to identify distribution of metals and to estimate the amount of these metals that can be potentially recovered from incineration residues. First, the partitioning behavior of Cr, Cu, Fe, Cd, Al, Zn, and Pb in bottom ash and fly ash was investigated in one large municipal waste incinerator in Taiwan. In addition, the material flow analysis (MFA) method was used to estimate the material flux of metals within incinerator plant, and to calculate the amount of metal recovery. According to the findings of this study, six metals (Fe, Al, Cu, Zn, Cr, and Pb) concentrated in bottom ash mostly, while Cd existed primarily in fly ash. The weight percentages of Fe (4.49%), Al (5.24%), Cu (1.29%), Zn (2.21%), and Pb (0.58%) in incinerator ash are high, and even higher than the compositions of natural minerals. Finally, the amount of Cr, Cu, Fe, Cd, Al, Zn and Pb that can be potentially recovered from incineration residues will reach 2.69 x 10(2), 1.46 x 10(4), 4.91 x 10(4), 6.92 x 10(1), 5.10 x 10(4), 1.85 x 10(4) and 4.66 x 10(3) ton/yr, respectively.     

A Web‐Based Decision Support System for Assessing Regional Water‐Quality Conditions and Management Actions1

Booth, Nathaniel L., Eric J. Everman, I‐Lin Kuo, Lori Sprague, and Lorraine Murphy, 2011. A Web‐Based Decision Support System for Assessing Regional Water‐Quality Conditions and Management Actions. Journal of the American Water Resources Association (JAWRA) 47(5):1136‐1150. DOI: 10.1111/j.1752‐1688.2011.00573.x Abstract: The U.S. Geological Survey National Water Quality Assessment Program has completed a number of water‐quality prediction models for nitrogen and phosphorus for the conterminous United States as well as for regional areas of the nation. In addition to estimating water‐quality conditions at unmonitored streams, the calibrated SPAtially Referenced Regressions On Watershed attributes (SPARROW) models can be used to produce estimates of yield, flow‐weighted concentration, or load of constituents in water under various land‐use condition, change, or resource management scenarios. A web‐based decision support infrastructure has been developed to provide access to SPARROW simulation results on stream water‐quality conditions and to offer sophisticated scenario testing capabilities for research and water‐quality planning via a graphical user interface with familiar controls. The SPARROW decision support system (DSS) is delivered through a web browser over an Internet connection, making it widely accessible to the public in a format that allows users to easily display water‐quality conditions and to describe, test, and share modeled scenarios of future conditions. SPARROW models currently supported by the DSS are based on the modified digital versions of the 1:500,000‐scale River Reach File (RF1) and 1:100,000‐scale National Hydrography Dataset (medium‐resolution, NHDPlus) stream networks.     

中国东北主要河流沉积物中多溴二苯醚的含量状况及生态风险分析

为揭示多溴二苯醚(PBDEs)在东北主要河流流域内的污染现状,通过采集该地区流域内表层沉积物样品,采用GC-NCIMS技术对沉积物中41种PBDEs同类物进行分析.结果发现沉积物中BDE209含量低于检出限,其它40种PBDEs同类物总含量(不包含BDE209)范围(干重)为0.91~17.67 ng·g-1.其中第二松花江吉林市上游和下游沉积物样品中PBDEs的检出含量最高,分别为15.86 ng·g-1、17.67 ng·g-1,以BDE207和BDE47为主,分别占PBDEs总量的86.5%和76.6%;其它河流沉积物中各同族体含量差异并不明显.实验结果与国内外最近的文献报道值相比较,再结合生态风险分析显示,东北主要河流沉积物中PBDEs的含量处于低污染水平,目前不存在生态风险.     

Anaerobic biodegradation of DDT residues (DDT, DDD, and DDE) in estuarine sediment.

The potential for anaerobic biodegradation of 1,1,1-trichloro-2,2-bischlorophenylethane (DDT), 1,1-dichloro-2,2,-bischlorophenylethane (DDD), and dichlorodiphenylchloroethylene (DDE) in anoxic sediment slurries collected from the Keelung River was investigated in this study. o,p'- and p,p'-DDT were dechlorinated to o,p'- and p,p'-DDD, respectively, and then transformed to other compound(s). 1-Chloro-2,2-bis (p-chlorophenyl) ethylene (DDMU) and trace amount of dichlorobenzophenone (DBP) were detected in sediment slurries amended with p,p'-DDT or p,p'-DDD. DDMU was also detected in sediment slurries amended with p,p'-DDE. The relative transformation rates for both o,p'- and p,p'-isomers of DDT, DDD, and DDE were DDT>DDD>DDE. Re-addition of DDT, DDD, or DDE to the sediment slurries after initial removal enhanced the respective dechlorination rates. The transformation rates of the p,p'-isomers of both DDT and DDD were faster than those of the respective o,p'-isomers. p,p'-DDT dechlorination in the p,p'-DDT-adapted sediment slurries were inhibited by the addition of molybdate, or molybdate plus sulfate, but not inhibited by the addition of sulfate. Addition of bromoethane-sulfonic acid (BESA) slightly inhibited p,p'-DDT dechlorination. Non-adapted sediment slurries lost the ability to dechlorinate pentachlorophenol during adaptation to p,p'-DDT. p,p'-DDD was the major transformation product of p, p'-DDT in 3,4,4',5-tetrachlorobiphenyl-adapted sediment slurries, which suggested that the microbial community in the 3,4,4',5-CB-adapted sediment was unable to remove chlorine from the aromatic rings of p,p'-DDT.     

广西典型碳酸盐岩区农田土壤-作物系统重金属生物有效性及迁移富集特征

为揭示碳酸盐岩地质高背景区土壤重金属生态风险,选择广西典型的成土母岩为碳酸盐岩的土壤重金属高背景区,采集水稻籽实及对应根系土样品68套,在分析测试土壤、农作物籽实样品中砷(As)、镉(Cd)、铬(Cr)、铜(Cu)、汞(Hg)、镍(Ni)、铅(Pb)和锌(Zn)这8种重金属含量及土壤中重金属赋存形态的基础上,采用统计学、地累积指数、生物富集系数及相关性分析等方法开展土壤重金属生态风险研究.结果表明,研究区土壤中8种重金属平均含量明显高于全国和广西表层土壤的平均水平,其中Cd、As和Cr超过农用地土壤污染筛选值的比例分别达95. 6%、86. 8%和69. 1%,超过土壤污染管控值的比例分别为27. 9%、17. 6%和5. 9%.区内土壤中As、Cr、Cu、Ni、Pb和Zn主要以残渣态为主(残渣态占比 80%),显示出较低的生物活性; Cd的生物活性相对较高,生物有效态组分占20. 99%,但仍明显低于全国其它非碳酸盐岩地区的土壤; Hg的潜在生物有效态组分占44. 04%,然而土壤中Hg全量较低,因此其潜在生物有效态的绝对含量较低.与土壤相比,研究区水稻籽实中重金属超标率明显较低,仅部分样品中Cd、Cr、Pb超过国家食品限量标准,超标率分别为8. 8%、2. 9%和23. 5%.相关性分析显示,研究区土壤重金属全量与对应的水稻籽实中重金属含量不存在显著正相关关系.水稻籽实重金属生物富集能力普遍较低,8种重金属生物富集系数(BCF)的均值均小于0. 1,其中As、Cr、Hg、Ni和Pb的BCF均值小于0. 05.上述结果表明,对于碳酸盐岩等地质高背景区,相关部门在制定污染土壤管控政策时不能仅以土壤重金属全量作为衡量标准,应综合考虑金属赋存形态、生物活性及农作物超标率等因素.     

工业锅炉烟管氯离子腐蚀原因分析

某DZL(SG)-1.25-M、Q-Ⅱ型工业锅炉的烟管水侧出现大量腐蚀凹坑,腐蚀烟管更换后不足一个月,烟管再次出现明显的腐蚀倾向.试验分析表明:水处理交换树脂清洗不彻底引起给水氯离子偏高,排污不足导致锅水中的氯离子和溶解固形物进一步浓缩,溶解固形物高于标准GB/T 1576-2018要求,受热烟管水侧外壁最终在锅水高浓度氯离子作用下发生了电化学腐蚀.     

故障树法和改进PSO-PNN网络的电梯故障诊断模型

针对电梯故障问题,提出一种将故障树分析法、改进的粒子群优化算法和概率神经网络相结合的方法用于电梯的故障诊断。以电梯的安全回路系统为例,用故障树法对回路进行分析,获得训练样本与故障类型;使用粒子群算法对概率神经网络的平滑因子进行优化,在优化过程中,针对粒子群算法存在易陷入局部最优的缺陷,提出对惯性权重的改进策略;采用相对误差对诊断效果做出评估,并与传统的概率神经网络和基本粒子群算法优化的概率神经网络在各种故障类型输出和最大相对误差等方面进行比较,结果表明:该模型能够有效诊断电梯故障。