Numerical technique for estimating equilibrium concentrations from initial concentrations when using the freundlich adsorption equation

Abstract

The Freundlich equation, X/m = K C_e ^N, is frequently used to express the partitioning of pesticides between solid (soil, sediment) and aqueous phases. When designing adsorption‐desorption experiments, it would be useful to be able to estimate the equilibrium concentration, C_e, in terms of the initial concentration, C_o, if reasonable estimates of K and N can be made. Because of the usual non‐integer nature of N, only a numerical solution of the Freundlich equation is possible for C_e in terms of C_o. A simple computer program is presented which produces almost an exact solution for the value of C_e.     

A PARTITIONING PROCEDURE FOR WATER QUALITY MANAGEMENT MODELS1

ABSTRACT: An improved computational procedure for solving water quality management models containing interacting pollutants and control policies is presented. The method is developed with respect to the specific problem of minimizing the costs of basin-wide thermal and organic pollution control to meet water quality standards. It views the problem in partitioned form where a master problem is used to find cooling levels for thermal polluters while subproblems determine optimal organic pollutant reductions for fixed cooling levels. A gradient based search procedure is used to solve the master problem. Computational results for several river systems are presented. Application of the method to other water quality management models is suggested.     

Large-Scale Effects of Timber Harvesting on Stream Systems in the Ouachita Mountains, Arkansas, USA

Using Basin Area Stream Survey (BASS) data from the United States Forest Service, we evaluated how timber harvesting influenced patterns of variation in physical stream features and regional fish and macroinvertebrate assemblages. Data were collected for three years (1990–1992) from six hydrologically variable streams in the Ouachita Mountains, Arkansas, USA that were paired by management regime within three drainage basins. Specifically, we used multivariate techniques to partition variability in assemblage structure (taxonomic and trophic) that could be explained by timber harvesting, drainage basin differences, year-to-year variability, and their shared variance components. Most of the variation in fish assemblages was explained by drainage basin differences, and both basin and year-of-sampling influenced macroinvertebrate assemblages. All three factors modeled, including interactions between drainage basins and timber harvesting, influenced variability in physical stream features. Interactions between timber harvesting and drainage basins indicated that differences in physical stream features were important in determining the effects of logging within a basin. The lack of a logging effect on the biota contradicts predictions for these small, hydrologically variable streams. We believe this pattern is related to the large scale of this study and the high levels of natural variability in the streams. Alternatively, there may be time-specific effects we were unable to detect with our sampling design and analyses.     

Spatial distribution and transport of heavy metals in soil, ponded-surface water and grass in a pb-contaminated watershed as related to land-use practices

The aim of this study was to investigate the spatial distribution of heavy metal in soil and evaluate the dissolution of metal from soil to ponded-surface water, leaching through soil profiles and metal uptake in grass as related to different land-use practices. The data provided a scientific basis for best-management practices for land use in Khli Ti watershed. The watershed has a Pb-contamination problem from the previous operation of a Pb-ore concentrator and abandoned Zn–Pb mine. Sampling sites were selected from a land-use map, with land-use types falling into the following four categories: forest, agricultural land, residential area and road. Soil, ponded-surface water, grass samples and soil profiles were collected. The study related soil characteristics from different land-use practices and locations with observed metal concentrations in ponded-surface water and soil. High enrichment factors of Pb and As in soil were found. Partitioning coefficient, K_d values were in the order: Cr > Pb > Ni > Cu > Cd > Zn. Soil disturbance from land-use activities including tillage and traffic increased leaching of trace metal from soils. Pb in soil was significantly taken up by grass even though the Transfer Factor, TF values were rather low. Agricultural activities in the watershed must be limited. Moreover, land encroachments in the upper and middle part of the watershed which have high potential of Pb must be strictly controlled in order to reduce the Pb contamination from non-point sources.     

基于空气质量自动监测站PM10滤纸的新型大气二NFDA1英监测技术研究

通过典型空气质量自动监测站PM10滤纸(结合气固相分配模拟)和传统大流量大气采样仪的比对试验,探讨了基于空气质量自动监测站PM10滤纸的新型大气二英监测技术的可行性。研究表明,基于空气质量自动监测站PM10滤纸的大气固相二英毒性当量浓度和指纹特征与传统大流量大气监测技术的监测结果具有很好的可比性;基于空气质量自动监测站PM10滤纸气固相分配模拟(利用Harner-Bidleman模型)的大气二英毒性当量浓度和指纹特征与传统大流量大气监测技术的监测结果具有很好的可比性。与传统大流量大气监测技术相比,基于空气质量自动监测站PM10滤纸的新型大气二英监测技术可以利用现有的大气自动监测网络和气固相分配模型,具有采样成本低、代表性强和易于普及等优点,适合不同区域尺度大气二英的长期同步监测。     

汾河流域太原段河水及沉积物中PFOS和PFOA的浓度分布特征

考察山西省汾河太原段全氟辛烷磺酸(PFOS)和全氟辛酸(PFOA)的浓度分布特征,采用固相萃取(SPE)的前处理方法与高效液相色谱-质谱联用(LC-MS/MS)仪器分析方法,检测了汾河太原段水体及沉积物中PFOS和PFOA的含量.结果表明,汾河水样品中PFOS和PFOA浓度范围分别为3.54~16.23 ng·L-1和2.49~4.79 ng·L-1,沉积物样品中含量分别为7.77~51.22 ng·g-1和1.94~3.54 ng·g-1.汾河太原段水样PFOS的浓度从上游到下游有逐渐升高的趋势,PFOA在各采样点的浓度相近;沉积物样品中PFOS的浓度大致呈从上游到下游逐渐升高的趋势,升高趋势没有水样中的明显,但是PFOA在各采样点的浓度亦相近.此外,PFOS在水体及沉积物中的分配与沉积物中有机碳的含量相关,而PFOA的相关性不显著.     

浙江汤浦水库浮游植物季节演替及其影响因子分析

为探索我国亚热带饮用水源水库浮游植物时空变化特征及其影响因素,2011年对汤浦水库浮游植物和22项水文水环境因子进行月度监测.结果表明,调查期间共检出浮游植物7门62属115种,其中绿藻种类最多,硅藻其次;春季水华期间(4月)浮游植物细胞密度达到最高20.88×10~6cells·L~(-1),随后因强降雨影响降至最低0.59×10~6cells·L~(-1)(6月);浮游植物群落组成的时间异质性比空间异质性更为明显,其时空方差分解的结果显示,时间变异占总变异的72.3%,大于仅占2.5%的空间变异;优势种和冗余分析(RDA)表明,硅藻全年优势最为明显,其次是蓝藻和隐藻,再次是绿藻,其中春季由硅藻和蓝藻占优势,夏季由蓝藻和绿藻占优势,秋季和冬季则由硅藻和隐藻占优势;HRT及其驱动的水库离子浓度变化和反硝化过程是主导春季和秋季水体扰动耐受和敏感种类间演变,以及春季水华形成的关键因子;SiO_2、WT和N∶P则是主导冬季和夏季,硅藻、隐藻和蓝藻、绿藻间演变的关键因子.     

长江口沉积物重金属赋存形态及风险特征

基于长江口沉积物8种重金属(As、Cd、Cr、Cu、Hg、Ni、Pb、Zn)总量与形态在丰、平、枯水期以及14个典型点位的分布特征,通过平衡分配法建立了长江口沉积物质量基准(SQGs),并以此评价长江口沉积物重金属生态风险,揭示重金属生态风险与其形态特征间的相关关系.结果表明,除Cd之外,长江口沉积物重金属以残渣态为主导形态,尤其是As、Cr、Hg,其残渣态含量均为90%以上.长江口As、Cd、Cr、Cu、Hg、Ni、Pb、Zn的沉积物质量基准分别为43.29、0.672、79.65、19.08、0.569、339.09、30.87、411.36μg·g~(-1).Cu的生态风险程度最高,对水生生物具有较大的毒性影响,应当引起重视.河口上游受到长江径流影响大,在丰水期风险较高,在平水期和枯水期则风险偏低;而下游受上海等城市排污影响较大,风险较高(尤其在平水期和枯水期).8种重金属的生态风险与赋存形态之间表现出3种不同的相关关系.     

Polybrominated diphenyl ethers in atmosphere and soil of a production area in China: Levels and partitioning

Polybrominated diphenyl ethers (PBDEs) were measured in atmosphere and soil samples taken in winter and summer at a PBDE production area of Laizhou Bay in China. The concentrations of P11PBDE were 0.017–1.17 ng/m3 in gaseous phase, 0.5–161.1 ng/m3 in particulate phase, and 73–2629 ng/g dry weight in soil samples. The PBDE congener pattern in the gaseous phase di ered from that in the particulate phase, and the PBDE congener pattern in the particulate phase was similar with that in soil. This demonstrated that there was little di erence with atmospheric particle-soil transfer e ciency among PBDE congeners. In addition, there were seasonal variations in percentages on particle for lower brominated congeners. The BDE-28 was mostly in the gaseous phase in summer (88.3%), whereas the average proportion of BDE-28 in gaseous phase in winter was 38.9%. Higher brominated congeners (i.e., BDE-206, BDE- 207, BDE-208, and BDE-209) were bound to the atmospheric particulate phase, and their potentials for long-range migration were mainly a ected by the environmental behavior of atmospheric particles. Results indicated that PBDE congeners in summer were closer to gas-particle partition equilibrium than in winter. Temperature should be considered the main factor causing nonequilibrium in winter.     

太湖流域宜溧河酚类内分泌干扰物的空间分布及风险评价

以NP(nonylphenol,壬基酚)、4-t-OP(4-t-octylphenol,辛基酚)和BPA(bisphenol A,双酚A)为目标物质,研究酚类EDCs(内分泌干扰物)在太湖流域宜溧河地表水体和悬浮物中的空间分布特征及风险评价. 结果表明,太湖流域宜溧河地表水体中ρ(NP)、ρ(4-t-OP)和ρ(BPA)分别为156.2～434.0、11.8～19.4和89.8～353.8 ng/L,悬浮物中w(NP)、w(4-t-OP)和w(BPA)分别为520.0～9 818.2、52.0～454.5和39.0～2 454.5 ng/g. 流域内生活及工业污水排放可能是宜溧河流域水体中酚类EDCs的主要来源,ρ(NP)与ρ(NO₃-)呈显著正相关(R=0.860,P<0.01). 宜溧河水系中酚类EDCs在水相-悬浮物相的有机碳标准分配系数为4.14～6.41,表明悬浮颗粒物的吸附是水体中EDCs迁移的一个重要途径. 研究区域中NP、4-t-OP和BPA的入湖量分别为506、57.9和297 kg/a. 风险评价结果表明,该地区部分河段ρ(EDCs)具有潜在的生态风险.