The role of the hyporheic zone in mercury (Hg) cycling has received limited attention despite the biogeochemically active nature of this zone and, thus, its potential to influence Hg behavior in streams. An assessment of Hg geochemistry in the hyporheic zone of a coarse-grained island in the Coast Fork Willamette River in Oregon, USA, illustrates the spatially dynamic nature of this region of the stream channel for Hg mobilization and attenuation. Hyporheic flow through the island was evident from the water-table geometry and supported by hyporheic-zone chemistry distinct from that of the bounding groundwater system. Redox-indicator species changed abruptly along a transect through the hyporheic zone, indicating a biogeochemically reactive stream/hyporheic-zone continuum. Dissolved organic carbon (DOC), total Hg, and methylmercury (MeHg) concentrations increased in the upgradient portion of the hyporheic zone and decreased in the downgradient region. Total Hg (collected in 2002 and 2003) and MeHg (collected in 2003) were correlated with DOC in hyporheic-zone samples: r ² = 0.63 (total Hg-DOC, 2002), 0.73 (total Hg-DOC, 2003), and 0.94 (MeHg-DOC, 2003). Weaker Hg/DOC association in late summer 2002 than in early summer 2003 may reflect seasonal differences in DOC reactivity. Observed correlations between DOC and both total Hg and MeHg reflect the importance of DOC for Hg mobilization, transport, and fate in this hyporheic zone. Correlations with DOC provide a framework for conceptualizing and quantifying Hg and MeHg dynamics in this region of the stream channel, and provide a refined conceptual model of the role hyporheic zones may play in aquatic ecosystems.

Micrometer-size poly(vinyl phosphonic acid) (p(VPA)) hydrogel was synthesized by employing UV irradiation of an emulsion containing vinyl phosphonic acid (VPA) and crosslinker, prepared using lecithin as surfactant and gasoline as solvent. The p(VPA) microgels were employed in absorption of UO₂²⁺ions from aqueous environments and have very high and fast absorption capacity. In about 20 min, 670 mg UO₂²⁺ions were absorbed per gram of p(VPA) microgel from the prepared UO₂²⁺ion solution, and the absorption capacity increased up to 900 mg at pH 6. Various parameters affecting UO₂²⁺absorption characteristics of p(VPA) were investigated. It was found that the Langmuir isotherm fitted the absorption characteristics of p(VPA) better than the Freundlich isotherm. Moreover, magnetic ferrite can be prepared within p(VPA) and used as a magnetically responsive p(VPA) microgel composite for externally controlled absorption of UO₂²⁺ions with little decrease in the absorption capacity of the p(VPA) microgel.

While most waste foundry sands (WFSs) are not hazardous, regulatory agencies are often reluctant to permit their beneficial use in agricultural and geotechnical applications due to concerns over metal leaching. The objective of this study was to quantify total and Toxicity Characteristic Leaching Procedure (TCLP) metals in 16 waste sands from Brazilian ferrous foundries then assess their potential to leach to groundwater using a probabilistic model. Total and TCLP metal concentrations in the non-hazardous sands fell within ranges as reported in the literature, although some of the leachate concentrations were found to exceed drinking water and groundwater maximum contaminant levels (MCLs). Leachate values above the MCLs were then used in the model to estimate groundwater concentrations at hypothetical wells up to 400m downgradient from a land application unit. A conservative scenario of 1 ha of land applied WFS, and high annual rainfall totals (low evaporation) suggested that groundwater concentrations of Ba, Hg, Mn, Ni, and Pb could potentially exceed health-based MCLs at most wells. While a wet climate can exacerbate the transport of metals, land application of WFSs in areas with moderate rainfall totals or high rainfall, high evaporation was predicted to be protective of groundwater quality and human health.

This study examined the transport behavior of nano zero-valent iron (NZVI) coated with three types of stabilizers (i.e., polyacrylic acid, Tween-20, and starch) in saturated sand- and soil-packed columns under varying geochemical conditions. The cations or ionic strength and humic acid (HA) affected the transport of NZVI in varying degrees for different types of surface-modified NZVI (SM-NZVI). The effects of HA on the transport of SM-NZVI were different in sand- and soil-packed columns. In the sand-packed column, the presence of HA exerted an effect on the particle–particle interaction (i.e., aggregation), resulting in either enhanced or decreased transport of SM-NZVI. However, in the soil-packed column, the HA not only influenced the particle–particle interaction but also exerted an effect on the particle–soil grain interaction (i.e., deposition). Additionally, a significant enhancement in the transport of SM-NZVI in the soil-packed column was observed with increasing particle concentration. Moreover, the adsorption of arsenic on the surface of SM-NZVI exhibited insignificant effect on the transport of SM-NZVI. The release of arsenic from the arsenic-loaded SM-NZVI was detected when subjected to flushing with phosphate-containing groundwater. This fundamental understanding of the subsurface transport of SM-NZVI is of critical importance for the benign use and risk management of SM-NZVI.

The ultimate goal of our study is to establish thin-layer chromatography (TLC) as a quick and simple method for identifying the type of refined petroleum products present in the environmental media. As a preliminary step, TLC chromatograms of different petroleum products, including gasoline, kerosene, and diesel, were characterized and compared. Methanol was determined as the optimum carrier solution in TLC analysis. The spherical-shaped TLC chromatogram of gasoline showed the longest migration distance, and thus the highest retardation factor (Rf) of 0.91. This was followed by that of kerosene (0.63) with an elliptical-shaped, and diesel (0.24) with an elongated trapezoid-shaped chromatogram. Rfof kerosene and diesel increased with the dilution factor, while gasoline showed a constant value. Additionally, it was observed that the TLC chromatograms of oils produced the same peak pattern with the corresponding petroleum products in gas chromatography (GC). A mixed sample of kerosene and diesel presented a triangular shaped chromatogram, underlining the need to consider the shape of chromatogram in addition to the Rfvalue, as an indicator of the petroleum type. The findings indicate that TLC has a huge potential to be used as a quick and reliable method for identifying the type of refined petroleum products in the environmental media.

The nanoscale zero-valent iron grafted on acid-activated attapulgite (A-nZVI) was prepared by a liquid-phase reduction method and used for Cr(VI) removal from solution with enhanced efficiency. The structure of the composite A-nZVI was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller surface area analysis. nZVI was well-dispersed on the surface of acid-treated attapulgite, and no obvious aggregation was observed due to the support of rod-like structure of attapulgite, which is beneficial to Cr(VI) removal. Batch experiments revealed that the removal of Cr(VI) using A-nZVI was consistent with pseudo-first-order reaction kinetics, and removal efficiency was up to 98.73 % within 60 min for 100 mL 20 mg/L Cr(VI) at the initial pH 7.0 and 4.0 g/L A-nZVI. The pseudo-first-order rate constant kₒbₛwas independent of initial Cr(VI) concentration, but there was a good linearity (r² = 0.95) between kₒbₛand the A-nZVI dosage. This study demonstrates that A-nZVI has the potential to become a promising material for in situ groundwater remediation.

Industrialization and urbanization in central Europe since the middle of the nineteenth century led to changes in urban waste water disposal and thus, to an increasing nutrient impact of surface waters by human waste. Based on historical statistics and literature research, we have made a quantification of nutrient loads discharged to surface waters in central European river catchments for seven decades between 1878 and 1939. For both total nitrogen (TN) and total phosphorus (TP), nutrient inputs via point (urban) and diffuse (rural) pathways, nutrient removal by waste water treatment plants (WWTPs) and that during soil passage were quantified. The total nutrient inputs caused by human waste between 1880 and 1940 increased from 243 to 396 kt TN year⁻¹, and from 18 to 30 kt TP year⁻¹. In 1880, most of the inputs (92 % for TN and 93 % for TP) originated from diffuse pathways (cesspits). In 1940, 43 % of TN and 41 % of TP inputs originated from urban pathways (sewer systems). The total nutrient removal between 1880 and 1940 declined from 79 to 59 % for TN and from 86 to 66 % for TP. Consequently, waste water disposal shifted from diffuse to urban pathways. On the one side, this led to rising nutrient loads discharged to surface waters because of insufficient nutrient removal by the early WWTPs. Otherwise, nutrient concentration in groundwater under rural areas decreased by discharge human waste via sewer systems out of the cities.

Phosphorus (P) is widely known as a limiting nutrient of water eutrophication for inland freshwater ecosystems. Owing to the complexity of P chemistry, remote sensing detection of total phosphorus (TP) concentrations currently remains limited especially for optically complex turbid inland waters. To address this need, a new TP remote sensing algorithm is developed based on prior water optical classification and the use of support vector regression (SVR) machine. The in situ observed datasets, used in this study, were collected at specific times during 2009 ~ 2011, covering a total of 232 stations from eight cruises in Lakes Taihu, Chaohu, Dianchi, and Three Gorges reservoir of China. Three types of waters were first classified by using a recently developed NTD675 (Normalized Trough Depth of spectral reflectance at 675 nm) water classification method. Then, spectral regions sensitive specifically to each water type were explored and expressed via several band ratios and used for retrieval algorithm development. The established type-specific SVR algorithms yield relatively high predictive accuracies. Specifically, the mean absolute percentage errors (MAPE) produced with the independent validation samples were achieved at 32.7, 23.2, and 14.1 % for type 1, type 2, and type 3 waters, respectively. Such water type-specific SVR algorithms are more accurate for the classified waters than an aggregated SVR algorithm for the nonclassified water and also superior to commonly used statistical algorithms. Moreover, application of the developed algorithms with HJ1A/HSI image data demonstrates that the algorithms have a large potential for remote sensing estimation of TP concentrations in optically complex turbid inland waters.

A new solid phase extraction method was developed for the preconcentration and determination of rare earth elements (REEs) (Nd, Sm, Eu, Gd, Tb, Dy, Ho, Yb, Lu, Ce) in water samples. The method is based on the sorption of REE ions onto the 2,6-pyridinedicarboxaldehyde-functionalized Amberlite XAD-4 resin at pH 7.0, followed by the elution with 2 mL of 1.0 mol L⁻¹ HNO₃ solution and determination by inductively coupled plasma optical emission spectrometry (ICP-OES). The main parameters affecting preconcentration, including sample pH, sample and eluent flow rate, and sample volume, have been investigated in detail. Under the optimum conditions (pH 7.0, sample flow rate of 1.0 mL min⁻¹, and eluent flow rate of 4.0 mL min⁻¹), detection limits between 0.011 and 0.298 μg L⁻¹ for a 25 mL sample volume and 0.006 and 0.149 μg L⁻¹ for a 50 mL sample volume were obtained. The sorption capacities for the resin were found to range between 49.0 μmol g⁻¹ (for Lu) and 66.7 μmol g⁻¹ (for Sm). The method was validated by analysis using a surface water certified reference material (SPS-SW2 Batch 127). The proposed method was successfully applied to the determination of REEs in tap water and seawater samples. The recovery values for the spiked water samples were in the range of 90.0–101.7 %.

Storm runoff is a major vector for transporting urban contaminants, especially metals, and continues to be a leading cause of urban waterways degradation. Stormwater treatment systems in New Zealand and Australia are primarily designed to remove total suspended solids and heavy metals to low levels, principally through bioinfiltration. In Christchurch, the second largest city in New Zealand, more than two thirds of the water, including stormwater, infrastructure is currently being rebuilt following the devastating 2010–2011 earthquakes. Despite increased use of bioinfiltration systems for this purpose, there is a dearth of knowledge about their treatment performance or water quality dynamics. This paper reports enhanced treatment efficacy in bioinfiltration stormwater systems by including an alkaline waste product, mussel shells, in the substrates. Experimental systems with mussel shells significantly increased the metal removal efficacy, hardness, and pH, which also have implications for reducing the potential ecotoxicological effects of stormwater. Mussel shell systems resulted in lower dissolved metal fractions in the treated effluent because metals shifted to the particulate states facilitated by hardness buffering. This resulted in greater metal removal afforded by increased filtration. Using locally available waste products can reduce the amount and transport impacts of waste going to landfills and offset costs associated with the construction of stormwater treatment systems, while concurrently improving stormwater treatment. The long-term capacity of such systems to enhance metal removal using waste mussel shells should be examined by monitoring larger pilot-scale systems in situ under different seasonal events.