The Rio Santiago in the Cordillera Negra of Peru is severely contaminated by acid mine drainage in its headwaters. In a strongly acid stream, at about 3800 m above sea level (masl), microterraces were found with terrace walls built up of dead moss, with encrustations and interstitial fine, creamy sediment. The stream water was turbid due to the presence of similar suspended sediment, which also occurred as a thin basal layer in inter-rim basins. The moss was identified as the rare bryophyte Anomobryum prostratum (Müll. Hal.) Besch. Chemical and mineralogical analyses show that green, living parts of the moss are gradually coated by Al/Fe (hydr)oxides, inducing their senescence and death. The necromass is covered by creamy crusts through precipitation of schwertmannite-type material from the stream water and simultaneous ‘capture’ of fine sediment. The latter consists of a mixture of precipitate and fine detrital primary minerals. These processes are held responsible for the formation of the microterraces, which regarding their composition and environment seem to be unique. Remarkable is the high As content of the creamy crusts and sediment, attributed to strong sorption of As, whereas its solute concentration is relatively low. This calls for more attention to suspended fine sediment in the assessment of environmental risks of stream water use. Lastly, the results raise serious doubts about the use of aquatic bryophytes as bioindicator for chemical pollution in acid mine drainage-polluted streams.

Road dust organic matter plays a vital role in mobilization of contaminants. This study investigated and characterized organic matter (OM) presents in road dust particles of various sizes. Road dust samples were collected from an industrialized city of Ulsan, Republic of Korea and fractionated into four groups: <75, 75–180, 180–850, and 850–2000 μm. OM extracted from the four fractions was characterized by excitation-emission matrix fluorescence and analyzed by parallel factor analysis (PARAFAC). The PARAFAC identified four major fluorophore components (C1–C4). These components were related to microbial humic-like, anthropogenic organic, fulvic-like, and low molecular weight OM contributed by anthropogenic activity, respectively. There were subtle changes in specific OM composition with change in particle size. The finest fraction contained more microbial humic-like substances whereas the coarse fraction was enriched with fulvic acid. The OM in two fractions (75–180 and 180–800 μm) showed dual characteristics. Our findings demonstrated that PARAFAC approach can assist to assess the accumulation of pollutants in road dust.

Recent droughts in the southwestern United States have heightened the interest in using more reclaimed water for agricultural irrigation. Treated wastewater effluent is a source of irrigation water and contains many pharmaceutical microcontaminants. Currently, there is little knowledge on if these microconstituents will enter food crops and if so where they will be found within the plant. For this experiment, the uptake of 17α-ethynylestradiol, fluoxetine HCl (Prozac®), and ibuprofen within different sections of a celery stalk over a 24-h time period was examined. Results found that all of these pharmaceuticals were taken up into the celery stalks within 24 h. Ibuprofen was found to have reached concentrations of 1 μg/g within the leaves in just 1 h. Metabolites of the ibuprofen were also detected at all locations within the stalk for all time periods. The concentration of EE2 in the submerged section of the stalk was found to increase from 0.031 to 0.911 μg/g of celery in just 23 h. The EE2 began to rise higher within the stalk to reach a concentration of 8.94 ng/g about 6 in above the base after 24 h. Fluoxetine HCl concentrations rose to 0.832 μg/g of celery within the submerged section of the stalk during the 24 h. After 12 h, fluoxetine HCl was detected within the bottom 4 in of the stalk. EE2, fluoxetine HCl, and ibuprofen all exhibit potential for uptake within food crops. Further studies on additional food crops and pharmaceuticals would be required to assess the full risk posed to human eating food crops irrigated with treated wastewater effluent.

The estimated diffusion fluxes of methane (CH₄) and carbon dioxide (CO₂) at the sediment–water interface in the Rzeszów Reservoir in southeastern Poland are presented. The relevant studies were conducted during 2009, 2010, and 2011. Calculated fluxes ranged from 0.01 to 2.19 mmol m⁻² day⁻¹and from 0.36 to 45.33 mmol m⁻² day⁻¹for methane and carbon dioxide, respectively. While the values for calculated diffusion fluxes of methane are comparable with those reported for other eutrophic reservoirs, much higher values were obtained here for carbon dioxide. The resulting values of δ¹³C-CH₄and the fractionation coefficients between methane and carbon dioxide (αCH₄-CO₂) suggest that methane in the sediment of the Rzeszów Reservoir is produced by acetate fermentation, while the hydrogenotrophic methanogenic process is of successively greater importance with increasing depth. In the top layer of the sediment, 24–72 % of CO₂came from methanogenesis, while the contribution made by the degradation of organic matter by methanogenesis to CO₂was greater in the deeper layer.

In this study, high-load compost leachate was successfully treated in a hybrid anaerobic baffled reactor (ABR)/electrocoagulation-flotation (ECF) system. The interaction effects of operational factors in ABR, i.e., influent chemical oxygen demand (COD), hydraulic retention time (HRT), and COD/nitrogen (N) ratio on the efficiency of COD removal and biogas production rate (BPR) were analyzed and correlated by response surface methodology (RSM). The optimum conditions of ABR were found at COD = 8250 mg/L, HRT = 46 h, COD/N ratio = 70, where COD removal and BPR reached 84 % and 76 mL/mg h, respectively. COD/N ratio and HRT were found to be the most effective parameters, respectively, on COD removal and BPR. The organic loading rate (OLR) values varied from 0.45 to 5.66 kg/m³ day. The data presented indicate that the ECF reactor successfully satisfies the discharge criteria for most of the experimental domain. The outcomes have exposed that sequential ABR/ECF reactors are a competent system in treating low- and high-strength compost leachate.

Understanding the biogeochemistry of metal-contaminated peatlands is important for predicting the impact of mining and industrial activities on peatlands and downstream surface waters and for predicting recovery of previously impacted sites. The objective of this work was to characterize the factors controlling spatial and temporal variability in surface peat (0–15 cm) and pore water chemistry of 18 regionally representative peatlands in Sudbury, Ontario, Canada. The pollution gradient is clearly evident as Cu and Ni concentrations in surface peat are elevated close to the main Copper Cliff smelter. Surface peat also differs greatly in acidity (pH) and organic matter content among sites, and dissolved organic carbon (DOC) concentrations in pore water are positively correlated with peat carbon content. In addition, sites having surface peat that is more decomposed also have pore water DOC that is more humified. Pore water chemistry varies seasonally; samples taken in late summer and fall were characterized by higher SO₄, and lower pH and higher concentrations of base cations and metals such as Ni, Co, and Mn compared with those in late spring that had higher DOC, higher pH, and higher concentrations of metals such as Cu and Fe. Despite the large spatial and temporal variability in pore water chemistry, soil-solution partitioning (K d) of some metals (Ni, Co, and Mn) can be explained by pH alone. Modeling soil-solution partitioning for these metals and Cu, Al, and Fe is significantly improved with the addition of SO₄; dissolved organic matter quality and quantity and/or the δ¹⁸O signature of the pore water in regression models indicating several factors other than acidity has an influence on pore water chemistry.

Zero-valent iron has received considerable attention for its potential application in the removal of heavy metals from water. This paper considers the possibility of removal of zinc ions from water by causing precipitates to form on the surface of iron. The chemical states and the atomic concentrations of solids which have formed on the surface of zero-valent iron as well as the type of the deposited polycrystalline substances have been analyzed with the use of X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), respectively. The BET surface area, the pH at point of zero charge (pHPZC), the ORP of the solutions, and the pH and chemical concentrations in the solutions have also been measured. Furthermore, the paper also considers the possibility of release of zinc from the precipitates to demineralised water in changing physicochemical and chemical conditions. In a wide range of pH values, Zn ₓ Fe₃ ₋ ₓ O₄ (where x ≤ 1) was the main compound resulting from the removal of zinc in ionic form from water. In neutral and alkaline conditions, the adsorption occurred as an additional process.

A comprehensive chemical characterisation of the ionic and metallic composition of PM₂.₅fraction of suburban aerosol collected with high‐volume aerosol samplers at a coastal suburban site of northwest Atlantic European is studied over a 1.5-year period (from March 2011 to August 2012). The monthly mean PM₂.₅mass concentrations (after gravimetric measurement) ranged from 13 to 26 μg m⁻³. Eighteen samples, which provide information pertaining to the monthly variation in chemistry, were analyzed. Trace metals (Al, As, Ba, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, V and Zn) were analysed in PM₂.₅fraction after acid extraction (total metallic concentration) and after sonication-assisted water extraction (aqueous soluble fraction). Major inorganic ions (Cl⁻, NO₃⁻, SO₄²⁻, Na⁺, K⁺, Ca²⁺, Mg²⁺, NH₄⁺and C₂O₄²⁻) were also analysed in the aqueous fraction of PM₂.₅. Trace metal extractability in water was in the range 50–67 % with exception of Al (∼2 %), Fe (∼4 %) and Cr (∼18 %). After univariate, cluster (CA) and principal component (PCA) analyses and air mass backward trajectory analysis, marine, crustal and anthropogenic (including road traffic) sources were found for the inorganic composition of PM₂.₅. Results also suggest a great influence of cleaner Atlantic air masses and ubiquitous sources for K⁺, Mg²⁺, Fe, Ni and V.

Removal of micropollutants from water with NF/RO membranes has received much attention in recent years. However, because of especially diffusion through the polyamide layer, NF/RO membranes never achieve complete removal, which may be a problem given the possibility of micropollutants causing adverse effects in even very low concentrations. In this paper, we have investigated a strategy of implementing adsorbents into the support layer of a NF membrane to increase the overall removal of three selected pesticides by combining membrane rejection and adsorption into one unit operation. The objective of the study was to act as proof of concept for the scheme, as well as to gain insights into how adsorbents may be inserted into the membrane support, and how they affect the membrane performance. The results showed that the addition of the adsorbents to the membrane increased the adsorption capacity of the membrane, and that the adsorbents could be embedded in the membrane without affecting the flux and rejection behaviour. This however depended very much on the specific manufacturing method. Furthermore, the adsorption capacity was found to vary significantly for the three pesticides, indicating a need for adsorbents designed to specifically target a given micropollutant. Overall, the concept of a complete removal membrane is realisable, but several challenges remain to be solved.

In this study, BiVO₄ powder is prepared and used as a visible-light catalyst for the photocatalytic degradation of alachlor. The as-prepared BiVO₄ photocatalyst is characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis diffuse reflectance spectra (DRS), and BET surface area analysis. Alachlor could be successfully degraded in the presence of both H₂O₂ and BiVO₄ catalyst under visible-light irradiation. With optimal operating parameters, its degradation efficiency could reach 97 % in 6 h. Factors such as solution pH, catalyst dosage, and the presence of anions are found to influence the degradation rate. To scrutinize the mechanistic details of the alachlor photodegradation, the intermediates of the process are separated, identified, and characterized by solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS). Results suggest that possible transformation pathways may include oxidation of the arylethyl group, cleavage of the N-methoxymethyl group, and N-chloroacetyl moiety.