To identify different NO₃ ⁻ sources in surface water and to estimate their proportional contribution to the nitrate mixture in surface water, a dual isotope and a Bayesian isotope mixing model have been applied for six different surface waters affected by agriculture, greenhouses in an agricultural area, and households. Annual mean δ¹⁵N–NO₃ ⁻ were between 8.0 and 19.4‰, while annual mean δ¹⁸O–NO₃ ⁻ were given by 4.5–30.7‰. SIAR was used to estimate the proportional contribution of five potential NO₃ ⁻ sources (NO₃ ⁻ in precipitation, NO₃ ⁻ fertilizer, NH₄ ⁺ in fertilizer and rain, soil N, and manure and sewage). SIAR showed that “manure and sewage” contributed highest, “soil N”, “NO₃ ⁻ fertilizer” and “NH₄ ⁺ in fertilizer and rain” contributed middle, and “NO₃ ⁻ in precipitation” contributed least. The SIAR output can be considered as a “fingerprint” for the NO₃ ⁻ source contributions. However, the wide range of isotope values observed in surface water and of the NO₃ ⁻ sources limit its applicability.

On-road emissions are a major contributor to rising concentrations of atmospheric greenhouse gases. In this study, we applied a downscaling methodology based on commonly available spatial parameters to model on-road CO₂ emissions at the 1 × 1 km scale for the Boston, MA region and tested our approach with surface-level CO₂ observations. Using two previously constructed emissions inventories with differing spatial patterns and underlying data sources, we developed regression models based on impervious surface area and volume-weighted road density that could be scaled to any resolution. We found that the models accurately reflected the inventories at their original scales (R² = 0.63 for both models) and exhibited a strong relationship with observed CO₂ mixing ratios when downscaled across the region. Moreover, the improved spatial agreement of the models over the original inventories confirmed that either product represents a viable basis for downscaling in other metropolitan regions, even with limited data.

Diatom indices are used to evaluate the ecological status of rivers but they have been rarely applied in estuaries. This study aimed to identify the diatom species indicating the main environmental gradients and pressures in a highly stratified estuary; and to evaluate the applicability of existing freshwater diatom indices. Marine influence due to salt-wedge intrusion and sea water mixing appeared as the main factor affecting diatom community. Three diatom assemblages were identified: indicators of riverine conditions (without marine influence), indicators of estuarine conditions (heterogeneous conditions with higher conductivities due to marine influence) and those specifically indicating well-established salt-wedge situations. Nowadays, the main human pressure affecting diatom community in the Ebro Estuary is the hydrological alteration resulting from flow regulation and abstraction. Several limitations were encountered in the application of diatom indices (e.g. inverse response with nutrients; ecologically important species not considered). Therefore, their use in estuaries should be done cautiously.

To assess the presence of endocrine disruptors in treated marine outfall discharges and their possible effects, mussels (Mytilus galloprovincialis) were caged in the environmental mixing zone of the outfall of the Santander sanitation system and in one control area. After 30, 60 and 90days, samples were collected to perform chemical analyses (metals, anionic surfactants, alkylphenols, bisphenol A, phthalates and estrogenic hormones), biomarkers of general stress (lysosomal membrane stability-LMS, histopathology) and biomarkers of endocrine disruption (vitellogenin-like proteins and gonad index). There were no significant differences between outfall and control sites on contaminant levels, except for 4-tert-octylphenol which was higher in the outfall site. Bacteriological counts were higher in the outfall area. No relevant differences in biomarkers were detected between treated and control mussels. A significant reduction in LMS occurred in both groups after 90days caging, indicating a stress situation possibly related to caging or to post-spawning reproductive state.

Neustonic microplastic and zooplankton abundance was determined in the North Western Mediterranean Sea during a summer cruise between July 9th and August 6th 2010, with a break between July 22th and 25th due to a strong wind event. Ninety percent of the 40 stations contained microplastic particles (size 0.3–5mm) of various compositions: e.g., filaments, polystyrene, thin plastic films. An average concentration of 0.116particles/m² was observed. The highest abundances (>0.36particles/m²) were observed in shelf stations. The neustonic plastic particles concentrations were 5 times higher before than after the strong wind event which increased the mixing and the vertical repartition of plastic particles in the upper layers of the water column. The values rise in the same order of magnitude than in the North Pacific Gyre. The average ratio between microplastics and mesozooplankton weights was 0.5 for the whole survey and might induce a potential confusion for zooplankton feeders.

Rare earth elements (REE) were analyzed in surface sediments from the Guadiana Estuary (SW Iberian Pyrite Belt). NASC (North American Shale Composite) normalized REE patterns show clearly convex curvatures in middle-REE (MREE) with respect to light- and heavy-REE, indicating acid-mixing processes between fluvial waters affected by acid mine drainage (AMD) and seawater. However, REE distributions in the mouth (closer to the coastal area) show slightly LREE-enriched and flat patterns, indicating saline-mixing processes typical of the coastal zone. NASC-normalized ratios (La/Gd and La/Yb) do not discriminate between both mixing processes in the estuary. Instead, a new parameter (EMREE) has been applied to measure the curvature in the MREE segment. The values of EMREE>0 are indicative of acid signatures and their spatial distribution reveal the existence of two decantation zones from flocculation processes related to drought periods and flood events. Studying REE fractionation through the EMREE may serve as a good proxy for AMD-pollution in estuarine environments in relation to the traditional methods.

Marine sediment preserves a useful archive for contaminants and other properties that associate with particles. However, biomixing of sediments can smear the record on a scale of years to thousands of years, depending on sedimentation rate and on the depth and vigour of mixing within a particular sediment. Where such mixing occurs, dates can no longer be associated with discrete sediment depths. Nevertheless, much can still be learned from biomixed profiles, provided that mixing is accounted for. With no modelling at all, it is possible to calculate an inventory of a contaminant at a site and a maximum possible sedimentation rate, and to determine whether the contaminant has increased or decreased over time. Radiodating the core with ²¹⁰Pb permits the estimation of sedimentation and mixing rates, which can be combined with the surface contaminant concentration to estimate an approximate flux of the contaminant. Numerical models that incorporate sedimentation and mixing rates (determined using ²¹⁰Pb and other transient signals with known deposition histories) can provide the basis to propose plausible histories for contaminant fluxes.

The present work describes a detailed study about the adsorption of malachite green (MG) by a polyether-type polyurethane foam (PUF) using sodium dodecylsulfate (SDS) as a carrier. The adsorption process was based on the formation of a hydrophobic ionic-pair between the MG cationic dye and the dodecylsulfate anion, which presented high affinity for the PUF. The manifold employed in the study was built up by adjusting a cylinder of PUF with 200 mg in the arm of an overhead stirrer, which was soaked (and stirred) in the solution containing the dye and SDS. The adsorption process was characterized in relation to equilibrium and kinetic aspects. Langmuir (r 2 = 0.842) and Freundlich (r 2 = 0.996) isotherms were also employed for modeling the system as well as the Nernst partition law (r 2 = 0.999). A study about the recovery of MG and the PUF regeneration was conducted, and the acetonitrile was the most efficient solvent for the desorption of the adsorbed ionic pair. The obtained results showed that the concentration of SDS added to the medium plays an important role on the adsorption process, which can be better described by employing a second-order kinetic model.

A new speciation model developed and implemented in Polymath was found to be successful in predicting struvite precipitation in soils. Struvite (NH4MgPO4) has been identified as a mineral for the recovery of nitrogen (N) and phosphorus (P). Predicting struvite precipitation potential in soil is important for optimal quantification of nutrient species. Polymath and Visual Minteq models were used for prediction of several solid phases in the soil. One approach to immobilize P for solid-phase formation is by co-blending. Immobilization was achieved through the blending of an Al-based water treatment residual (Al-WTR) and with Ca–Mg-based materials [slag and magnesium oxide (MgO)]. The results suggest that Polymath model revealed solid Phases of dicalcium phosphate pentahydrate (DCPP), magnesium hydroxide (MHO), magnesium orthophosphate (v) docosahydrate (MP22), magnesium orthophosphate (v) octahydrate (MP8), and struvite, which were lacking in the modeling from Visual Minteq. Residual leachate from the co-blended amendments; Soil+WTR+Slag, Soil+WTR+MgO, Soil+MgO, Soil+Slag, Soil+WTR, and the control (without amendment) had struvite of 353, 199, 119, 90, 37, and 12 mg l-1, respectively. This implies that struvite, a phosphate mineral can be precipitated in the soil and could be released as nutrients for plant uptake. Struvite precipitation in soil and for reuse may reduce cost and may be a safe practice for sustainable environmental nutrient management.

The aim of this study was to investigate the removal of both polycyclic aromatic hydrocarbons (PAHs) and heavy metals from field-contaminated sediments by activated persulfate oxidation. Various chemicals, including hydroxypropyl-β-cyclodextrin (HPCD), S,S-ethylenediaminedisuccinic acid (EDDS), tetrasodium pyrophosphate (Na₄P₂O₇), and hydrochloric acid (HCl), were applied individually before or after activated persulfate oxidation to enhance the co-removal of both types of pollutants. It was found that the organic removal efficiency was not significantly enhanced by increasing the concentration of HPCD from 2.5 to 5.0 mM. The removal efficiency of heavy metals was not improved even at an excess amount of EDDS after activated persulfate oxidation. However, the addition of EDDS acted as the Fe²+ carrier for activated persulfate oxidation. In addition, no significant enhancement of heavy metal removal was observed by increasing the concentrations of Na₄P₂O₇ and HCl from 0.01 to 0.1 M after activated persulfate oxidation. However, comparing 0.1 M HCl with 0.1 M Na₄P₂O₇, HCl was shown to be more effective in promoting the removal of organic pollutants. With further adjustments on the experimental conditions, the highest removal amount of metals and PAHs was achieved by adding 2 M of HCl with 3 days mixing, followed by Fe²+-activated persulfate oxidation (PS/Fe²+ molar ratio at 4:1) for further 6 h mixing. The removal efficiency of low and high molecular weight PAHs was about 70 and 20 %, respectively, while the removal efficiency of metals was 70, 100, 40, 65, 65, 80, and 100 % for Cr, Cu, Hg, Mn, Ni, Pb, and Zn, respectively.