State of the Art Report on Mathematical Methods for Groundwater Pollution Source Identification

The reliable assessment of hazards or risks arising from groundwater contamination problems and the design of efficient and effective techniques to mitigate these problems require the capability to predict the behavior of chemical contaminants in flowing water. Most attempts at quantifying contaminant transport have relied on a solution of some form of a well-known governing equation referred to as advection-dispersion-reaction equation. To choose an appropriate remediation strategy, knowledge of the contaminant release source and time release history becomes pertinent. As additional contaminated sites are being detected, it is almost impossible to perform exhaustive drilling, testing, and chemical fingerprint analysis every time. Moreover, chemical fingerprinting and site records are not sufficient to allow a unique solution for the timing of source releases. The purpose of this paper is to present and review mathematical methods that have been developed during the past 15 years to identify the contaminant source location and recover the time release history.     

酸碱调控及底物浓度对木糖发酵产酸特性的影响

以木糖为碳源采用间歇培养方式,对木糖厌氧发酵产酸进行研究。考察木糖浓度和初始pH值对木糖厌氧产酸的影响。结果表明,随着木糖浓度的增加,总产酸量得到提高,但木糖利用率却呈现下降的趋势。当木糖浓度为5 g/L时,其利用率为100%,15 g/L时利用率为73.9%,此时挥发性脂肪酸(VFAs)为9.22 g/L。木糖的分批投加可有效促进产酸,尤其是促进乙酸浓度的提高。pH为5.0和6.0左右时,VFAs主要成分为乙酸和丁酸;而pH为7.0～9.0时,乙酸含量明显增高,在pH值为8.0的条件下乙酸含量占总VFAs的80.1%。在pH=8.0时经过8 d左右的发酵,VFAs浓度可达9.34 g/L。     

Estimation of transport parameters of phenolic compounds and inorganic contaminants through composite landfill liners using one-dimensional mass transport model

One-dimensional (1D) advection–dispersion transport modeling was conducted as a conceptual approach for the estimation of the transport parameters of fourteen different phenolic compounds (phenol, 2-CP, 2-MP, 3-MP, 4-MP, 2-NP, 4-NP, 2,4-DNP, 2,4-DCP, 2,6-DCP, 2,4,5-TCP, 2,4,6-TCP, 2,3,4,6-TeCP, PCP) and three different inorganic contaminants (Cu, Zn, Fe) migrating downward through the several liner systems. Four identical pilot-scale landfill reactors (0.25 m³) with different composite liners (R1: 0.10 + 0.10 m of compacted clay liner (CCL), L_e = 0.20 m, k_e = 1 × 10⁻⁸ m/s, R2: 0.002-m-thick damaged high-density polyethylene (HDPE) geomembrane overlying 0.10 + 0.10 m of CCL, L_e = 0.20 m, k_e = 1 × 10⁻⁸ m/s, R3: 0.002-m-thick damaged HDPE geomembrane overlying a 0.02-m-thick bentonite layer encapsulated between 0.10 + 0.10 m CCL, L_e = 0.22 m, k_e = 1 × 10⁻⁸ m/s, R4: 0.002-m-thick damaged HDPE geomembrane overlying a 0.02-m-thick zeolite layer encapsulated between 0.10 + 0.10 m CCL, L_e = 0.22 m, k_e = 4.24 × 10⁻⁷ m/s) were simultaneously run for a period of about 540 days to investigate the nature of diffusive and advective transport of the selected organic and inorganic contaminants. The results of 1D transport model showed that the highest molecular diffusion coefficients, ranging from 4.77 × 10⁻¹⁰ to 10.67 × 10⁻¹⁰ m²/s, were estimated for phenol (R4), 2-MP (R1), 2,4-DNP (R2), 2,4-DCP (R1), 2,6-DCP (R2), 2,4,5-TCP (R2) and 2,3,4,6-TeCP (R1). For all reactors, dispersion coefficients of Cu, ranging from 3.47 × 10⁻⁶ m²/s to 5.37 × 10⁻² m²/s, was determined to be higher than others obtained for Zn and Fe. Average molecular diffusion coefficients of phenolic compounds were estimated to be about 5.64 × 10⁻¹⁰ m²/s, 5.37 × 10⁻¹⁰ m²/s, 2.69 × 10⁻¹⁰ m²/s and 3.29 × 10⁻¹⁰ m²/s for R1, R2, R3 and R4 systems, respectively. The findings of this study clearly indicated that about 35–50% of transport of phenolic compounds to the groundwater is believed to be prevented with the use of zeolite and bentonite materials in landfill liner systems.     

Comparative distribution, sourcing, and chemical behavior of PCDD/Fs and PCBs in an estuary environment

PCDD/F and PCB field data (1041 samples) in five media (dissolved, suspended sediment, bed sediment, catfish, and blue crab) were studied to explore dual contaminant patterns in the Houston Ship Channel, Texas, USA. PCDD/Fs showed greater concentration than PCBs in suspended sediments while PCBs were higher in apparent dissolved (truly dissolved + DOC-associated), fish, and crab. PCDD/Fs at nearly all locations contributed more strongly to dioxin-like toxicity. The fraction of PCB TEQ was, however, enriched in biotic over abiotic media due in large part to the presence of PCB 126, which was mostly undetected in water and sediment and yet exhibited a BAF three times greater than 2,3,7,8-TCDD. Dissolved-suspended sediment and suspended-bed sediment relationships showed that (1) observed apparent dissolved concentration differences (as fraction of total water were mean 10% PCDD/Fs and 63% PCBs) can reasonably be explained by a four-phase partition model (truly dissolved, DOC-associated, suspended OC, and suspended BC) for PCBs but not for PCDD/Fs and (2) the contaminants behaved similarly in bed to suspended sediment concentration ratios (C_bed/C_susp) upstream of a major confluence but not downstream. PCA-cluster analysis pointed to the possibility that suspended sediment PCB contamination originates from resuspended bed sediment while PCDD/Fs in suspended sediment originates more probably from other sediment sources such as upstream wash load or air deposition. Finally, examinations of a congener marker ratio (PCB 209/206) seemed to indicate that a source of pure PCB 209 may exist in bed sediment near Patrick Bayou though the source was not completely localized.     

Occurrence, bioaccumulation and potential sources of polybrominated diphenyl ethers in typical freshwater cultured fish ponds of South China

To determine the potential input sources of polybrominated diphenyl ethers (PBDEs) to fish farming environments in South China, samples of seven various environmental matrices were collected from October 2006-September 2007. Tri- to deca-BDEs were detected in all samples analyzed, with mean concentrations (±standard deviations) at 5.7 ± 3.6 ng/L in pond water, 15 ± 11 ng/g dry wt. in pond sediment, 12 ± 3.8 ng/g dry wt. in bank soil, 21 ± 20 ng/g lipid wt. in fish, and 93 ± 62 ng/g lipid wt. in fish feeds. In addition, BDE-209 was the major constituent in all samples except fish and BDE-47 was predominant in fish samples. Relatively high abundances of BDE-49 were detected in all the samples compared to those in the penta-BDE technical products. Several bioaccumulation factors were evaluated. Finally, statistical analyses suggested that fish feed, as well as pond water at a lesser degree, may have been the major source of PBDEs in freshwater farmed fish.     

Particle-facilitated lead and arsenic transport in abandoned mine sites soil influenced by simulated acid rain

The role of acid rain in affecting Pb and As transport from mine tailings was investigated by pumping simulated acid rain at a infiltration rate of 10.2 cm/h through soil columns. Simulated acid rain with pH of 3.0, 4.5 and 5.6 were used as leaching solutions. Results showed that 86.9–95.9% of Pb and 90–91.8% of As eluted from the columns were adsorbed by particles in the leachates. Scanning electron microscopy (SEM) analysis showed that particles released from the columns were mainly composed of flocculated aggregates and plate or rod shaped discrete grains. Transmission electron microscopy (TEM) coupled with energy dispersive X-ray analysis (EDX) showed that these particles were predominantly silicate minerals. Results from our experiments demonstrated that when rapid infiltration conditions or a rainstorm exist, particle-facilitated transport of contaminants is likely to the dominant metal transport pathway influenced by acid rain.     

利用羟胺实现城市污水短程硝化最优投加点选择

模拟缺氧/好氧（A/O）模式运行的序批式活性污泥法（SBR）处理系统,探究利用羟胺实现城市污水短程硝化的投加点优化.批次实验发现,溶解氧存在会降低羟胺对亚硝酸盐氧化菌（NOB）抑制效果的（20±0.5）%.此外,相较于未经缺氧处理和延长缺氧时间（>15min）处理,缺氧时间为1~5min可提高NOB活性抑制率13%~25%.长期试验表明,在缺氧段末投加羟胺的短程硝化系统维持NO₂^--N积累率92%以上,而在好氧阶段投加羟胺的系统NO₂^--N积累率逐渐降低.qPCR分析证明,羟胺投加点为缺氧段末可在充分抑制NOB基础上,降低对氨氧化菌（AOB）的抑制作用,从而有利于AOB成为优势菌群结构.本研究为优化羟胺投加点和稳定维持短程硝化提供理论基础.     

药剂法去除矿井水中多种有害物质的应用研究

根据某一煤矿矿井水水质特点,采用在矿井水净化处理工艺过程中投加药荆的方法,达到同时去除矿井水中的悬浮物、碳酸盐硬度和铁等多种有害物质的目的。工程试验表明,聚合氯化铝投加量100mg／L,石灰投加量120-140mg／L,二氧化氯投加量大于1．5mg／L时,可以取得较好的处理效果。     

联合基于野外的代谢组学和化学分析手段筛选优先关注新兴污染物：在五大湖流域的案例研究

由于毒性评估项目很难与日渐增长的需要测试的污染物保持同步,所以较难将关注点集中在影响水生生态系统的最为生物相关的污染物上。由于评估潜在毒性污染物所造成的生物影响已被证明是有效的,内生性代谢物的研究（代谢组学）对于剔除那些较低可能造成生物影响的污染物或许有一定帮助,从而找出生物重要性最高的污染物。本研究在北美五大湖流域的18个地点针对置于笼中的黑头软口鲦（Pimephales promelas）进行实验。我们测定了水体温度和水样中的污染物浓度（目标污染物132种,检出86种）,并使用1H-NMR谱测量了肝极性提取物中的内生性代谢物。利用偏最小二乘法回归来比对内生性代谢物的相对丰度与污染物浓度和环境温度。结果表明内生性极性代谢物的指标与最多49种污染物存在共同变化。因此我们认为至多52%的检出污染物与内生性代谢物变化的共同变化不显著,表明这些污染物很可能不会在这些地点造成可以检测到的影响。这是通过缩短对于实验地点有着潜在影响的污染物列表从而扫描出检出污染物生物相关性的第一步。类似的信息有助于风险评估者区分不同污染物的重要性并将重点毒性测试放在最为生物相关的污染物上。
精选自Nicol Janecko, Lucie Pokludova, Jana Blahova, Zdenka Svobodova, Ivan Literak. Linking field-based metabolomics and chemical analyses to prioritize contaminants of emerging concern in the Great Lakes basin. Environmental Toxicology and Chemistry: Volume 35, Issue 10, pages 2493–2502, October 2016. DOI: 10.1002/etc.3409
详情请见http://onlinelibrary.wiley.com/doi/10.1002/etc.3409/full
     

The Environmental Capacity Approach to the Control of Marine Pollution: The Case of Copper in the Krka River Estuary

Changes in soil pH, soil heavy metal forms, and the metabolic diversity of microbial communities were examined in soil samples collected in 1-mm increments from barley roots in soil contaminated with cadmium (Cd) and zinc (Zn) using a rhizobox system. Concentrations of exchangeable Cd and Zn increased near the roots owing to a decrease in soil pH. Conversely, the concentration of inorganically bound Cd and Zn decreased near the roots. Despite having the highest concentration of the most toxic exchangeable metals, the rhizosphere also had the highest bacterial and fungal metabolic activity and diversity when assessed using BIOLOG plates. Therefore, the promoting effects of root exudates on microbial activity could outweigh the adverse effects of Cd and Zn on microorganisms in the rhizosphere.