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.

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 %.

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.

The issue of air pollution has become the focus of the world because of its significant influence to the economic development and public health. This paper proposes an interval dual stochastic-mixed integer programming (IDSIP) approach for regional air quality management. The IDSIP approach can be effectively communicated into the optimization processes and resulting solutions, which is formulated through integrating interval-parameter integer programming (IIP) within a two-stage stochastic programming (TSP) joint chance-constrained programming (CCP) and could deal with uncertainties expressed as not only probability distributions but also interval values. Moreover, the left-hand-side (LHS) constraints with stochastic variables could be handled at different risk levels with varied reliability scenarios. In the modeling formulation, penalties are imposed when expected policies are violated. The results indicate that reasonable solutions for air quality management system have been generated, which can help decision makers draw up productive strategies taking into account the trade-off between system economy and air quality under uncertainty.

Identifying the relative importance of stressors is critical for effectively managing and conserving freshwater aquatic ecosystems. However, variability in natural ecosystems and the potential for multiple stressors make understanding the effects of stressors challenging in the field. To address these challenges, we assessed four common stressors in the northeastern USA including acidification (pH), climate change (water temperature), salinization (Na and Cl), and nutrient addition using laboratory mesocosms. Each stressor was evaluated independently, with ten mesocosms assigned across a gradient of concentrations for each stressor (total N = 40). We then monitored the effects of the stressors on a model community consisting of periphyton, zooplankton, Northern watermilfoil (Myriophyllum sibericum), American ribbed fluke snail (Pseudosuccinea columella), and larval American bullfrogs (Lithobates catesbeianus). Aquatic stressors varied in the strength of their effects on community structure: Nutrient addition was the least influential stressor, with no significant effects. Acidification influenced periphyton biomass, but not higher trophic levels. Water temperature influenced primary productivity and survival of amphibian larvae, but not intermediate trophic levels. Finally, road salt led to decreases in productivity for all trophic levels included in our model systems. Our results support the findings of prior research, although the effects of acidification and nutrient addition were less pronounced in our study. Importantly, we found that road salt had the most far-reaching effects on a model aquatic community. Given that road salt is the most easily managed of the stressors we compared, our results indicate that improving the condition of freshwater aquatic ecosystems in the northeastern USA may be a feasible objective.

Artemisinin, an antimalarial compound derivated from the cultivated plant Artemisia annua L., is produced in situ through cultivation of A. annua under different climatic conditions. The bioactive compound artemisinin has been observed to spread to the surroundings as well as to leach to surface- and groundwater. To make better risk assessments of A. annua which is cultivated under varying climatic conditions, the temperature-dependent toxicity of artemisinin toward the green algae Pseudokirchneriella subcapitata and the macrophyte Lemna minor was evaluated at temperatures ranging from 10 to 30 °C. To include a possible effect of temperature on the degradation rate of artemisinin, artemisinin concentrations were measured during the experiment and toxicity was related to the time-weighted averages of exposure concentrations. The toxicity of artemisinin toward the macrophyte L. minor and the algae P. subcapitata increased with increasing growth rates, and we conclude that bioavailability plays a minor role in the observed relation between temperature and toxicity of artemisinin. The obtained results are important for possible future risk assessment of A. annua cultivation.

To remove phosphate from solution, a new class of sorbent based on chitosan bead (CB) was prepared using copper ion (Cu(II)) with/without a traditional crosslinking agent (glutaraldehyde [GLA]); these materials are referred to as CB-G-Cu and CB-Cu, respectively. Copper ions play a key role in the CB synthesis; these species crosslink each polymer chain, and during phosphate removal, they are the active functional group. Overall, 2.5 % (w/w) of chitosan is necessary to maintain the physical properties of the bead. In the FTIR spectra, adding GLA decreased the intensity of the amino group in chitosan, lowering the amount of copper in the CB. The maximum phosphate uptake (Q) for CB-Cu was 53.6 mg g⁻¹when calculated with the Langmuir isotherm, and the phosphate equilibrium was achieved in 12 h. Although the solution pH was not strongly affected, values below 7 are optimal for phosphate removal. The CB-Cu can be feasibly applied during a fixed column test, revealing that the phosphate breakthrough was 1.5 times higher than with CB-G-Cu.

Green Infrastructure (GI) practices have been identified as a sustainable method of managing stormwater over the years. Due to the increasing popularity of GI as an integrated urban water management strategy, most of the current catchment modeling tools incorporate these practices, as built-in modules. GI practices are also viewed as economically viable methods of stormwater management when compared to conventional approaches. Therefore, cost-benefit analysis or economics of GI are also emerging as obligatory components of modeling tools. Since these tools are regularly upgraded with latest advancements in the field, an assessment of tools for modeling stormwater management and economic aspects of GI practices is vital to developing them into more sophisticated tools. This review has undergone a three-phase process starting with 20 identified modeling tools available in the literature followed by a detailed review of a selection of ten most recent and popular modeling tools, based on their accessibility. The last phase of the review process is a comparison of the ten modeling tools along with their different attributes. The major aim of this review is to provide readers with the fundamental knowledge of different modeling tools currently available in the field, which will assist them with screening for a model, according to their requirements from the number of tools available. A secondary aim is to provide future research directions on developing more comprehensive tools for GI modeling, and recommendations have been presented.

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.

Pharmaceutical agents, like diclofenac and acetaminophen, are sold without prescription leading to excessive use. These agents may reach water bodies through various routes and attain significant concentrations, posing a risk to hydrobiont health. Diverse studies have shown that during the biotransformation of these compounds, reactive metabolites and reactive oxygen species are produced which induce oxidative stress and damage to diverse biomolecules. However, toxicity studies that assess the effects of a mixture of contaminants are scarce, being very important as this is how they are actually in the environment. The present study aimed to evaluate the oxidative stress induced by mixture of diclofenac and acetaminophen on Cyprinus carpio and compare with the effect produced by these pharmaceuticals in isolation. A 96-h sublethal toxicity assay of the tested pharmaceuticals (isolated and in mixture) was performed and the following biomarkers were evaluated: lipid peroxidation, protein carbonyl content, and activity of the antioxidant enzymes superoxide dismutase, catalase, and glutathione peroxidase. The pharmaceuticals evaluated induce oxidative stress on C. carpio in isolated form and as a mixture, but the level of damage being dependent on the organ evaluated as well as the type of toxicant and form of exposure (in isolation or as a mixture).