The Park River watershed (PRW), a sub-basin of the Lower Connecticut River watershed, has experienced increased urbanization over the last century as the city of Hartford and its surrounding towns have grown and developed. We present watershed-wide and outflow scale maps of the trace metals Cd, Cu, Zn, and Pb to determine patterns of contamination in fine (<63 μm) stream sediment. Results are compared to established sediment quality guidelines (SQG) and probable effect concentrations (PEC) for each metal. Throughout the watershed, higher concentrations of trace metals are observed in the more urbanized south branch of the PRW. In this sub-basin, there are more industries that use, and waste, metals in their manufacturing processes that contribute to acutely high concentrations of metals in the fine bedload sediments. Impervious surfaces are examined as well in the context of the entire watershed. While an increase in metals can be attributed to an increase in impervious surfaces, these increases do not generally exceed SQGs and PECs. Two focused mapping studies were conducted at the storm water outflow of the West Hartford Landfill and the Trout Brook Sanitary Sewer Overflow (SSO). The purpose of these studies was to analyze the local effects of natural stream features such as channel bar deposits next to the outfalls. We determined that the sediment directly below the two outfalls often exceeded the PEC, while the accumulated sediment around the channel bar deposits was not contaminated beyond background stream levels. We believe mapping at both the small (watershed) and large (outfall) scale can be helpful in future urban studies to determine the extent of trace metal sediment contamination in both channelized and natural sections and may provide a useful method for sediment mitigation endeavors.

Methane (CH₄) formation in wastewater treatment is linked to long residence times under anaerobic conditions such as those in sewers and primary treatment units. Emissions of this methane to the atmosphere can occur under turbulent flows and, potentially, during aeration in an activated sludge plant. An online, 8-week monitoring campaign of CH₄emissions and operational conditions was conducted to study emissions from a full-scale nitrifying activated sludge plant (ASP). Significant emissions were found throughout the aerated lane, with the highest values observed two thirds down the lane. Emissions had high diurnal and spatial variability, with values ranging from 0.3 to 24 g CH₄/h. No significant correlations were found between dissolved oxygen, aeration or influent loads. The results suggest that emissions are linked to upstream process conditions, with potential for methane generation in-lane due periods of limited oxygen availability. The dynamic oxygen profile observed suggests that aerobic and anoxic conditions coexist in the lane, leading to limited oxygen diffusion from the bulk liquid to the inner regions of the floc where anoxic/anaerobic layers may allow methanogenic microorganisms to survive. The average emission factor was 0.07 % of removed chemical oxygen demand, giving a total of 668 kg CH₄/year and 14,000 CO₂equivalents/year. The operational carbon associated with the energy requirements of the ASP increased by 5 %. With emerging legislation requiring the reporting of greenhouse gas emissions, the carbon impact may be significant, particularly as the industry moves towards a carbon-reducing future. Therefore, an adequate profiling of full-scale emissions is critical for future proofing existing treatment technologies.

Phosphorus (P) loss from non-point sources is a main cause of freshwater eutrophication in agricultural regions. Knowledge-based watershed management plans, aimed at reducing the diffuse flux of phosphorus from specific land-use and site characteristics to freshwater resources, are needed in order to curb eutrophication in agriculture regions. In this context, the use of a phosphorus index provides a simple and practical method for identifying hot-spot source areas and to estimate their potential for contributing a flux of P to the surface waters. However, as a semi-quantitative tool, the P index is usually difficult to validate due to inadequate data representation relative to large spatial and temporal variation in P fluxes. An amended P index scheme is therefore developed and validated, based on comprehensive synoptic soil study and stream water monitoring as well as a previous study that had applied the former P index in the studied watershed in northern China (Zhang et al. 2003). The amendments include the use of data from the individual village units (mean area, ca. 30.6 ha), use of the degree of P saturation (DPS) in the source factor scheme, adoption of flow length factor and modified water course erosion factor into the P transportation scheme, and an adjustment of the organization structure of the P index scheme. The validation of the amended P schemes was performed by comparing the modeled average P index values with the corresponding measured P fluxes for 12 different sub-catchments. The results indicate an improved precision in the simulated potential for P loss using the refined P index scheme. Measured fluxes of total P (r = 0.825), particulate P (r = 0.867), and less-studied yet more relevant dissolved P (r = 0.627) all showed significant correlations with the modeled P index values in the amended P scheme. The primary direct finding of the current research is that the areas with close proximity to rivers and the reservoir, as well agricultural land around villages, are found to be the main hot-spot sources for P loss to the reservoir.

The aim of this study is to develop a new method for the preconcentration of copper via a dispersive liquid–liquid microextraction method using 4-phenyl-3-thiosemicarbazide as a ligand and determination with FAAS in different sample types such as plants, soils and natural waters such as seawater. Optimum experimental conditions were determined, and the applicability of the proposed dispersive liquid–liquid microextraction method was investigated. In the first step of the work, the parameters that affect complex formation and extraction, such as volume of extractant/disperser solvent, pH and concentration of the chelating agent, NaCl and surfactant, were optimised. The interference effects from potential concomitants on the determination of the Cu(II) ion were investigated in synthetic mixtures that contain high levels of these ions. These results showed the analytical applicability of the proposed method in different kinds of samples. Under the optimal conditions, the calibration curve was linear over the range 2–600 μg L⁻¹of copper, and the detection limit was 0.69 μg L⁻¹in the original solution (3 Sb/m). The accuracy of the developed method was checked by analysing certified reference materials (QCS-19 (high purity standard), LGC 6156 (harbour sediment) and NBS 1572 (citrus leaves)). Results obtained were in agreement with certified values with a t test showing that no significant differences at the 95 % confidence interval levels were found. The proposed method was applied to seawater, river water, and plant and soil samples. The recovery values for spiked water samples were between 99.7 and 117.3 %.

A common weed, Imperata cylindrica (cogongrass), was used as a low-cost adsorbent for the adsorption of methylene blue (MB) and the process optimized. The effects of four factors, namely, shaking speed (100–300 rpm), pH (3–9), contact time (10–40 min) and adsorbent dosage (0.4–1.0 g), on colour removal and chemical oxygen demand (COD) reduction of MB were studied and optimized using fractional factorial design and response surface methodology. The two factors that play a vital role in the adsorption process are pH and adsorbent dosage. From the results, colour removal and COD reduction recorded coefficient of determination (r ²) values of 0.9600 and 0.9594, respectively. Optimum adsorption conditions, resulting in 99.09 % colour removal and 97.87 % COD reduction, were achieved at shaking speed of 100 rpm, pH 9, 40 min contact time and adsorbent dosage of 1.0 g. The adsorption systems for MB dye were found to fit the pseudo-second order model instead of the pseudo-first order model, while equilibrium studies showed that the adsorption process followed the Langmuir isotherm.

Mutual sorption interactions between heavy metals, humic acids and fungi were evaluated in this article. While the relative amount of sorbed As(V), Sb(III) and Pb(II) slightly decreased or remained unchanged, the sorption capacity of Zn(II) increased significantly with increasing amounts of immobilized humic acids in the Ca-alginate beads. Therefore, zinc is most likely preferentially sorbed to functional groups provided by humic acids rather than carboxyl or hydroxyl groups of alginate, with an optimum pH for uptake between 4 and 6. Nevertheless, the removal efficiency of metal(loid)s by unmodified Ca-alginate beads or those with humic acids modification was highest for Pb(II), at up to 93.5 %. The pH value also affects humic acids sorption properties on microbial surfaces. While the highest humic acids sorption capacity of mycelial pellets prepared from Aspergillus niger occurred at pH 8.5 (231 mg g⁻¹), the pelletized Aspergillus clavatus biomass was more effective in acidic solution and 199 mg g⁻¹was recorded there at pH 5.5. The effect of mutual interactions between humic acids and mycelial pellets on Zn(II) immobilization indicates that zinc affinity is higher for the fungal surface than for humic acids which do not supply sufficient active sorption sites for zinc. This resulted in less sorption capacity of the mycelial pellets modified with humic acids compared to the unmodified biomass.

Normal seed germination of native herbaceous species can be reduced by high concentrations of deicer products and their constituent salts. Chloride salts are commonly used during the winter months in temperate climates to remove ice and snow. Although these products greatly improve driving conditions, they can have detrimental effects on the vegetation growing along highways. The purpose of this laboratory study was to determine the impact of a magnesium-based deicer product and a sodium-based deicer product and the major salts they contain on the germination and viability of several species of grasses and forbs native to Colorado and planted in revegetation seedings there. Seeds were placed on blotter paper saturated with either a water control, one of three concentrations of each of the deicing solutions, or one of three concentrations of a pure NaCl or MgCl₂ solution. Increasing concentrations of salt ions generally resulted in delayed and reduced normal seed germination, especially the sodium- and magnesium-based deicer solutions. Germination for most species was lower when seeds were grown in deicer solution compared with germination percent of seeds grown in the pure salt solutions. Some species were more tolerant of one of the salts and deicers. Species with C4 photosynthetic pathway were more tolerant than C3 species of high concentrations of both deicer products. Those species which attained the highest germination percent under moderate or high solution concentrations included blue grama, buffalograss, little bluestem, mountain brome, and slender wheatgrass.

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.

In order to develop an effective and economical method for removing U(VI) from the low concentration radioactive wastewater with the U(VI) concentration of less than 1 mg L⁻¹, the biomass of Aspergillus niger was prepared and modified with ethylenediamine, and the biosorption of uranium from the low concentration radioactive wastewater by the unmodified and the modified biomasses was investigated in a batch system. The modified biomass exhibited the adsorption efficiency of 99.25 % for uranium under the optimum conditions that pH was 5.0, the contact time was 150 min, and the biosorbent dose was 0.2 g L⁻¹. The adsorption fitted well to Langmuir isotherm, and the maximum sorption capacity of the modified biomass for U(VI) was determined to be 6.789 mg g⁻¹which increased by 36.45 % compared with the unmodified biomass. The adsorption kinetics was better depicted by pseudo-second-order kinetic model. The Gibbs free energy change (ΔG⁰), enthalpy change (ΔH⁰), and entropy change (ΔS⁰) showed that the process of U(VI) adsorption was spontaneous, endothermic, and feasible. The changes in the groups, morphology, and the presence of U(VI) on the surface of the adsorbents which were characterized by FT-IR, SEM, and EDS, demonstrated that the U(VI) was successfully adsorbed onto the modified biomass. Moreover, the UO₂²⁺absorbed on the modified biomass can be released by 0.1 mol L⁻¹HNO₃with high desorption efficiency of 99.21 %. The results show that the modified biomass can remove U(VI) from low concentration radioactive wastewater more effectively than the unmodified biomass.

The leachate pollution index (LPI) represents a tool to assess the pollution potential of a leachate, on a scale from 5 to 100. However, the significance of the LPI number in terms of a particular phytotoxic effect has not been investigated. The aim of this work was to determine if the LPI is also an appropriate tool in relation to the biological significance of a phytotoxic assay using the common bean plant (Phaseolus vulgaris L.) in a greenhouse scale test. Two different leachates were used in this study: one from Guanajuato (GUL) and another from Toluca (TOL); the calculated LPIs were 34.8 and 18.4, respectively. Leachate dilutions of 25, 50, and 75 % were used; undiluted leachate (100 %) was also used, and an enriched mineral solution was used as the control. Our findings indicate that when using concentrated leachate, the LPI was not directly related to the recorded phytotoxic effect (grain yield was significantly reduced by TOL leachate); however, when only using diluted leachate (25 %), the LPI was directly related to the effect. These findings suggest that for diluted leachates, leachates with higher LPIs are likely to exert a more detrimental effect on the common bean than leachates with lower LPIs.