Total mercury concentrations are presented for 19 Swedish watercourses 2000–2010, together with an analysis of factors affecting these concentrations in space and time. Organic matter (OM) measured as absorbance at 420nm (Abs₄₂₀) and total organic carbon (TOC) were the variables most strongly correlated with THg concentrations in the pooled dataset from all 19 watercourses, explaining 66% and 61% of the variance respectively. The correlation between THg and OM indicates that OM is the main controlling factor independent of geographical variation in Hg deposition, geology, or any other factor evaluated in this study. Despite an increase in TOC concentrations at most sites during the study period, THg increased in only one of the watercourses, and the THg/TOC ratio decreased significantly at six sites. The Abs₄₂₀ did not increase like TOC. We suggest that OM-fractions absorbing at 420nm are more important for Hg mobilization than other OM-fractions.

The magnetic, nanocrystalline Fe₀.₂(Co₂₀Ni₈₀)₀.₈ alloy porous microfibers were prepared by the citrate gel thermal decomposition and reduction process. The morphology, chemical composition, microstructure, and magnetic properties of the microfibers were investigated by X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray, Brunauere–Emmette–Teller, and vibration sample magnetometer. The as-prepared magnetic, nanocrystalline Fe₀.₂(Co₂₀Ni₈₀)₀.₈ porous microfibers consisting of about 48 nm grains are characterized by diameters of 1–4 μm, specific surface area of 17.73 m²/g, and specific magnetization of 196.7 Am²/kg. The arsenic(V) absorption on these magnetic Fe₀.₂(Co₂₀Ni₈₀)₀.₈ porous microfibers at room temperature was determined by the ICP-AES measurement of arsenic(V) in aqueous solution. The results show that the pseudo-first-order kinetic model is consistent with the arsenic(V) adsorption process and a good correlation coefficient (R ² = 0.9862). By comparing among the Langmuir, Freundlich, Temkin, and Redlich–Peterson models for adsorption isotherms of arsenic(V) onto the magnetic Fe₀.₂(Co₂₀Ni₈₀)₀.₈ porous microfibers at room temperature, the Freundlich model and Redlich–Peterson model can be used to evaluate the arsenic(V) adsorption isotherm at room temperature. The arsenic(V) equilibrium absorbance of the magnetic Fe₀.₂(Co₂₀Ni₈₀)₀.₈ porous microfibers is up to 1.9 mg/g when the initial arsenic(V) concentration is 1.0 mg/L in aqueous solution.

A simple spectrophotometric method was developed to quantify chlorophenol (CP) concentrations after reaction with potassium permanganate and quenching with sodium sulfite. Other quenching agents (peroxide, sodium thiosulfate and hydroxylamine hydrochloride) were found to create absorbance in the spectral range required for CP quantification. Analysis at pH 12 gave greater absorption and sensitivity for the method compared with pH 5.6. The calibration curves of the proposed methods were linear in the concentration ranges 0.0061–0.61 and 0.0078–0.78 mM with detection limit of 0.0006 and 0.0008 mM for dichlorophenols and monochlorophenols, respectively. The oxidation kinetics of five chlorophenols in aqueous solution with excess potassium permanganate were evaluated using the analytical method. The pseudo-first-order reaction rates were found to be relatively rapid 1.42 × 10−3 to 0.024 s−1 and followed the sequence 2-chlorophenol (2-CP) > 2,6-dichlorophenol (2,6-DCP) > 4-chlorophenol (4-CP) > 2,4-dichlorophenol (2, 4-DCP) > 3-chlorophenol (3-CP). The apparent second-order rate constant was calculated from the measured pseudo-first-order rate constant with respect to CP with initial KMnO4 concentration (1.5 mM) and follows the same sequence of pseudo-first-order rate constant. This shows that chlorine atoms in the structure of chlorophenol had a significant influence on the oxidation of chlorophenols by potassium permanganate. Permanganate can be used for the treatment of chlorophenol-contaminated soil and groundwater.

The performance of the magnetic anion exchange resin, MIEX®, in the pretreatment of reclaimed water for managed aquifer recharge (MAR) was investigated. MIEX® can effectively remove aromatic organic substances with molecular weights above 10 kDa and between 1 and 5 kDa, which are always present recalcitrant during soil infiltration. The removal of organic substances is accompanied by the elimination of other undesirable components in MAR, such as nitrogen and phosphorus. The optimal process parameters are at resin doses of 5–10 mL L⁻¹ and contact time of 10–15 min, as determined via jar tests. The efficiency of the MAR pilot system was consistent throughout the long running time, during which the MIEX® treatment significantly contributed (30 to 60 %) to the removal of both organic and inorganic materials (i.e., dissolved organic carbon, ultraviolet absorbance at 254 nm, color, nitrate, ammonia, phosphorus, and sulfate). The quality of the MAR final effluent is lower than the groundwater standard for drinking sources (type III in GB/T 14848-93). Based on this study, MIEX® treatment is a suitable and efficient pretreatment method for the removal of extra dissolved organic matters and nitrates in reclaimed water for MAR.

BACKGROUND AIM AND SCOPE: Though the tidal Anacostia River, a highly polluted riverine system, has been well characterized with regard to contaminants, its overall resident bacterial populations have remained largely unknown. Improving the health of this system will rely upon enhanced understanding of the diversity and functions of these communities. Bacterial DNA was extracted from archived (AR, year 2000) and fresh sediments (RE, year 2006) collected from various locations within the Anacostia River. Using a combination of metabolic and molecular techniques, community snapshots of sediment bacterial diversity and activity were produced. RESULTS: Employing Biolog EcoPlates, metabolic analysis of RE sediments from July revealed similar utilization of amines, amino acids, carbohydrates, carboxylic acids, and polymers at all sites. Normalized optical density measurements demonstrated that for most compounds, utilizations were similar though when differences did occur, the downstream site was enhanced compared to one or both of the upstream sites. Using denaturing gradient gel electrophoresis, bacterial diversity fingerprints of operational taxonomic units (OTUs) were obtained. Dendograms of the banding patterns revealed qualitative relationships as well as differences between replicate samples from similar sites. Replicates from the AR sites shared several common OTUs, while RE sites were more varied. Species richness and Shannon diversity indices generally increased with increasingly downstream locations, and were significant for the AR sediments (analysis of variance, P < 0.0001). Carbon and nitrogen content and concentration of fine grain sediment (<63 μm) were positively correlated with OTU richness (r 2 = 0.37, P = 0.0008; r 2 = 0.45, P < 0.0001; r 2 = 0.48, P = 0.001, respectively). CONCLUSIONS: This study demonstrated that the bacterial communities from all regions sampled were not only metabolically active with the capacity to utilize several different compounds as energy sources but also were genetically diverse. This study is the first to focus on the overall bacterial community, providing insight into this vital component of stream ecosystems. Understanding the bacterial components of aquatic systems such as the Anacostia River will increase our knowledge of the overall structure and function of the ecological communities in polluted systems, subsequently enhancing our ability to improve the health of this important tidal river.

PURPOSE: Cold and hot water processes have been intensively used to recover soil organic matter, but the effect of extraction conditions on the composition of the extracts were not well investigated. Our objective was to optimize the extraction conditions (time and temperature) to increase the extracted carbon efficiency while minimizing the possible alteration of water extractable organic matter of soil (WEOM). METHOD: WEOM were extracted at 20°C, 60°C, or 80°C for 24 h, 10–60 min, and 20 min, respectively. The different processes were compared in terms of pH of suspensions, yield of organic carbon, spectroscopic properties (ultraviolet–visible absorption and fluorescence), and by chromatographic analyses. RESULTS: For extraction at 60°C, the time 30 min was optimal in terms of yield of organic carbon extracted and concentration of absorbing and fluorescent species. The comparison of WEOM 20°C, 24 h; 60°C, 30 min; and 80°C, 20 min highlighted significant differences. The content of total organic carbon, the value of specific ultraviolet absorbance (SUVA254), the absorbance ratio at 254 and 365 nm (E 2/E 3), and the humification index varied in the order: WEOM (20°C, 24 h) < WEOM (80°C, 20 min) < WEOM (60°C, 30 min). The three WEOM contained common fluorophores associated with simple aromatic structures and/or fulvic-like and common peaks of distinct polarity as detected by ultra performance liquid chromatography. CONCLUSIONS: For the soil chosen, extraction at 60°C for 30 min is the best procedure for enrichment in organic chemicals and minimal alteration of the organic matter.