The goal of this study was to document if lakes in National Parks in Washington have exceeded critical levels of nitrogen (N) deposition, as observed in other Western States. We measured atmospheric N deposition, lake water quality, and sediment diatoms at our study lakes. Water chemistry showed that our study lakes were ultra-oligotrophic with ammonia and nitrate concentrations often at or below detection limits with low specific conductance (<100 μS/cm), and acid neutralizing capacities (<400 μeq/L). Rates of summer bulk inorganic N deposition at all our sites ranged from 0.6 to 2.4 kg N ha⁻¹ year⁻¹and were variable both within and across the parks. Diatom assemblages in a single sediment core from Hoh Lake (Olympic National Park) displayed a shift to increased relative abundances of Asterionella formosa and Fragilaria tenera beginning in the 1969–1975 timeframe, whereas these species were not found at the remaining (nine) sites. These diatom species are known to be indicative of N enrichment and were used to determine an empirical critical load of N deposition, or threshold level, where changes in diatom communities were observed at Hoh Lake. However, N deposition at the remaining nine lakes does not seem to exceed a critical load at this time. At Milk Lake, also in Olympic National Park, there was some evidence that climate change might be altering diatom communities, but more research is needed to confirm this. We used modeled precipitation for Hoh Lake and annual inorganic N concentrations from a nearby National Atmospheric Deposition Program station, to calculate elevation-corrected N deposition for 1980–2009 at Hoh Lake. An exponential fit to this data was hindcasted to the 1969–1975 time period, and we estimate a critical load of 1.0 to 1.2 kg N ha⁻¹ year⁻¹for wet deposition for this lake.

During an extended period from 2010–2012 ambient air quality researches, concentration of nitrogen dioxide (NO₂) in the air was measured applying the passive method. In order to evaluate the spatial distribution of pollutants and the major sources, 12 sampling sites across the region were chosen. Additionally, the seasonal changes of this pollutant under different meteorological conditions (air temperature, humidity, wind speed and direction) were investigated. The long-term study showed 3.8 times higher NO₂concentrations in the Mažeikiai urban area (24.2 μg m⁻³) as compared to other locations in the region (6.3 μg m⁻³). This confirms the assumption that the main source of NO₂in this area is motor vehicle exhaust fumes. The analysis of the results obtained in different seasons showed a significant difference (p < 0.05) in NO₂concentrations under different meteorological conditions. The increase in NO₂concentrations was recorded in the winter and late autumn seasons, due to reduced solar radiation and lower temperatures. Cluster analysis results showed that sampling sites can be grouped into different classes based on NO₂main source, motor vehicles and traffic intensity.

Principal component analysis (PCA) was performed on chemical data of two sediment cores from an urban freshwater lake in Copenhagen, Denmark. X-ray fluorescence (XRF) core scanning provided the underlying datasets on 13 variables (Si, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Rb, Cd, and Pb). Principal component analysis helped to trace geochemical patterns and temporal trends in lake sedimentation. The PCA models explained more than 80 % of the original variation in the datasets using only two or three principal components. The first principal component (PC1) was mostly associated with geogenic elements (Si, K, Fe, Rb) and characterized the content of minerogenic material in the sediment. In the case of both cores, PC2 was a good descriptor emphasized as the contamination component. It showed strong linkages with heavy metals (Cu, Zn, Pb), disclosing changing heavy-metal contamination trends across different depths. The sediments featured a temporal association with contaminant dominance. Lead contamination was superseded by zinc within the compound pattern which was linked to changing contamination sources over time. Principal component analysis was useful to visualize and interpret geochemical XRF data while being a straightforward method to extract contamination patterns in the data associated with temporal elemental trends in lake sediments.

Polychlorinated biphenyls (PCBs) pose a threat to the environment due to their high adsorption capacity to soil organic matter, stability and low reactivity, low water solubility, toxicity and ability to bioaccumulate. With Icelandic soils, research on contamination issues has been very limited and no data has been reported either on PCB degradation potential or rate. The goals of this research were to assess the bioavailability of aged PCBs in the soils of the old North Atlantic Treaty Organization facility in Keflavík, Iceland and to find the best biostimulation method to decrease the pollution. The effectiveness of different biostimulation additives (N fertiliser, white clover and pine needles) at different temperatures (10 and 30 °C) and oxygen levels (aerobic and anaerobic) were tested. PCB bioavailability to soil fauna was assessed with earthworms (Eisenia foetida). PCBs were bioavailable to earthworms (bioaccumulation factor 0.89 and 0.82 for earthworms in 12.5 ppm PCB soil and in 25 ppm PCB soil, respectively), with less chlorinated congeners showing higher bioaccumulation factors than highly chlorinated congeners. Biostimulation with pine needles at 10 °C under aerobic conditions resulted in nearly 38 % degradation of total PCBs after 2 months of incubation. Detection of the aerobic PCB degrading bphA gene supports the indigenous capability of the soils to aerobically degrade PCBs. Further research on field scale biostimulation trials with pine needles in cold environments is recommended in order to optimise the method for onsite remediation.

Recent evidence suggests that microplastic pollution is widespread in every oceanic basin; however, there is limited data available for the tropical South Atlantic Ocean. The purpose of this study was to examine the distribution, density and characteristics of plastic particles in plankton samples collected in the western tropical Atlantic Ocean. Neustonic tows (N = 160) were conducted near three important insular environments (Fernando de Noronha, Abrolhos and Trindade), and the presence of microplastics in the ocean surface of these areas was confirmed for the first time. The collected microplastic particles included hard plastic fragments, plastic films, paint chips and fibres and strands, which were classified as a secondary source of microplastics. The stock of plastic originates from both land-based and marine-based sources. This type of marine pollution in the tropical Atlantic Ocean is a potential threat to important ecological species.

The aim of the present study was to evaluate the influence of the recirculation rate on the efficiency of a 1,000-L pilot anaerobic sequencing batch biofilm reactor (ASBBR) treating effluent from a small dairy plant over a long-term period (570 days). Three operational conditions were studied, in which recirculation rates were varied, resulting in upflow velocities of 0.2, 3.8, and 6.4 m h⁻¹and the cycle time of 48 h. The biomass was immobilized on plastic supports containing polyurethane foam. The organic loading rate varied according to the operations occurring in the dairy plant. After system stability had been verified, temporal profiles of the substrate and metabolite concentrations were obtained, allowing kinetic parameter inference. Sludge samples from the inoculum and from the reactor were analyzed through microscopic examination, molecular biology analyses, and specific methanogenic activity assays. The average efficiencies of organic matter removal were 82 ± 11, 84 ± 9, and 87 ± 9 % at velocities of 0.2, 3.8, and 6.4 m h⁻¹, respectively. Microscopic examinations indicated that the fluorescent microorganisms decreased throughout the experiment, and they were not detected in the last condition. Homoacetogenesis was inferred as a possible pathway for H₂removal and for maintenance of the methanogenic process. Specific methanogenic activity increased throughout the monitoring period. It was possible to conclude that the ASBBR was efficient, robust, and reliable in treating dairy effluents under the conditions used.

The coffee agro-industry generates a large volume of wastewater that is notable for its high organic strength as well as its color content. Due to the seasonal nature of the harvest (3–4 months per year), this particular industrial waste needs a treatment method that is both reliable and fast (in terms of start-up time). As part of investigating a system capable of treating a coffee wastewater, this research evaluated four electrochemical advanced oxidation processes (EAOPs) using boron-doped diamond (BDD) electrodes. The processes were anodic oxidation (AO), anodic oxidation with electrogenerated H₂O₂(AO-H₂O₂), electro-Fenton (EF), and photoelectro-Fenton (PEF). Experimental conditions were as follows: 40 mA cm⁻²current density (all EAOPs), 0.3 mmol Fe²⁺L⁻¹(Fenton systems), 300 mL air min⁻¹(AO-H₂O₂, EF, PEF), and 500 μW cm⁻²UV irradiation (photo-Fenton systems). The performance of the four EAOP treatment methods (in terms of color and organic carbon removal) was compared against two conventional chemical oxidation methods, namely, Fenton and photo-Fenton. The research indicated that the four EAOPs were better at removing color (89–93 %) and total organic carbon (TOC) (73–84 %) than the respective chemical Fenton (58 and 4.8 %) and photo-Fenton (61 and 7 %) methods. The trend in performance was as follows: AO-H₂O₂ > AO > PEF ≈ EF. It appeared that the ferrous iron reagent formed a dark-colored complex with some coffee components, diminishing the effect of Fenton reactions. In addition, the dark color of the wastewater limited the effect of light in the UV-Fenton processes. Analysis showed that acceptable levels of Fe²⁺(0.3 mmol L⁻¹) and energy (0.082–0.098 kWh g⁻¹TOC) were required by the EAOPs after 4-h treatment time. In conclusion, the use of electrochemical methods (equipped with BDD electrodes) seems a promising method for the effective treatment of coffee wastewaters.

A granular media synthesized using iron oxide nanoparticle-coated alumina (IONA) has been demonstrated as an effective solid catalyst in the heterogeneous catalytic ozonation of para-chlorobenzoic acid (pCBA). TEM analysis showed that iron oxide nanoparticles with an average size of 5–20 nm were well-coated onto an alumina surface. It was determined that the iron oxide nanoparticle coating increased the specific surface area by 54 times and the functional group density by 1.5 times. During catalytic ozonation at acidic pH levels, it was clearly observed that IONA increased the degradation of pCBA (98 %) through effective hydroxyl radical formation compared to bare alumina (9 %) under continuous ozonation processes. In comparing the Rcₜvalue, which represents the ratio of ozone exposure to hydroxyl radical exposure, the Rcₜof IONA was approximately four times higher than for bare alumina. In addition, IONA showed good stability for catalytic ozonation of pCBA in the reusability tests.

Iron hydroxide supported onto porous diatomite (D-Fe) is a low-cost material with potential to remove arsenic from contaminated water due to its affinity for the arsenate ion. This affinity was tested under varying conditions of pH, contact time, iron content in D-Fe and the presence of competitive ions, silicate and phosphate. Batch and column experiments were conducted to derive adsorption isotherms and breakthrough behaviours (50 μg L⁻¹) for an initial concentration of 1,000 μg L⁻¹. Maximum capacity at pH 4 and 17 % iron was 18.12–40.82 mg of arsenic/g of D-Fe and at pH 4 and 10 % iron was 18.48–29.07 mg of arsenic/g of D-Fe. Adsorption decreased in the presence of phosphate and silicate ions. The difference in column adsorption behaviour between 10 % and 17 % iron was very pronounced, outweighing the impact of all other measured parameters. There was insufficient evidence of a correlation between iron content and arsenic content in isotherm experiments, suggesting that ion exchange is a negligible process occurring in arsenate adsorption using D-Fe nor is there co-precipitation of arsenate by rising iron content of the solute above saturation.

The variability of levels of fecal indicator bacteria (FIB) and a human-associated genetic marker (HF183) during wet and dry weather conditions was investigated at two urban coastal watersheds in Southern California: Santa Monica Canyon channel (SMC) and Ventura Harbor, Keys, and Marina. Seventy-eight to 86 % of the samples collected from SMC sites exceeded standard water quality standards for FIB (n = 59 to 76). At SMC, HF183 was present in 58 % of the samples (n = 78) and was detected at least once at every sample site. No individual site at SMC appeared as a hotspot for the measured indicators, pointing to a likely chronic issue stemming from urban runoff in wet and dry weather. In Ventura, the Arundell Barranca, which drains into Ventura Harbor and Marina, was a source of FIB, and HF183 was most frequently detected off of a dock in the Marina. Rainfall significantly increased FIB levels at both SMC and Ventura; only at Ventura did HF183 detection increase with wet weather. Sample locations that were high in FIB were geographically distinct from the sites that were high in HF183 in Ventura, which supports the importance of measuring host-associated parameters along with FIB in chronically impaired watersheds to guide water quality managers in pollution remediation efforts.