Disposing of nitrate-containing effluents from seawater-fed intensive aquacultural applications is a major environmental problem. A possible solution is to mix nitrate-rich effluents from marine recirculating aquaculture systems (RASs) with citrate-rich liquid wastes (CLW), a common by-product of the food industry. Where possible, such strategy can alleviate two environmental problems simultaneously, in a cost-effective fashion. However, concerns are often raised regarding secondary pollution stemming from the use of CLW, particularly related to phosphorus and heavy metals. This work showed that both phosphorus and heavy metal were completely absorbed by the bacterial sludge generated in the process, indicating low environmental risk associated with the disposal of the treated effluent to the environment. Operation of continuous stirred-tank reactor (CSTR) single-sludge denitrification reactor with CLW as electron and carbon donor resulted in high nitrate removal efficiency (>95 %) and denitrification rate of up to 1.6 g NO₃-N L⁻¹reactor day⁻¹along with low bacterial biomass yield [0.23 g chemical oxygen demand (COD) new cells g⁻¹COD citrate]. Moreover, the use of CLW was found to be environmentally safe and equally efficient to the use of traditional, costly carbon sources such as methanol and acetic acid, rendering this alternative attractive for treatment of nitrate-rich saline effluents.

Sorption is commonly agreed to be the major process underlying the transport and fate of polycyclic aromatic hydrocarbons (PAHs) in soils. However, there is still a scarcity of studies focusing on spatial variability at the field scale in particular. In order to investigate the variation in the field of phenanthrene sorption, bulk topsoil samples were taken in a 15 × 15-m grid from the plough layer in two sandy loam fields with different texture and organic carbon (OC) contents (140 samples in total). Batch experiments were performed using the adsorption method. Values for the partition coefficient Kd(L kg⁻¹) and the organic carbon partition coefficient KOC(L kg⁻¹) agreed with the most frequently used models for PAH partitioning, as OC revealed a higher affinity for sorption. More complex models using different OC compartments, such as non-complexed organic carbon (NCOC) and complexed organic carbon (COC) separately, performed better than single KOCmodels, particularly for a subset including samples with Dexter n < 10 and OC <0.04 kg kg⁻¹. The selected threshold revealed that KOC-based models proved to be applicable for more organic fields, while two-component models proved to be more accurate for the prediction of Kdand retardation factor (R) for less organic soils. Moreover, OC did not fully reflect the changes in phenanthrene retardation in the field with lower OC content (Faardrup). Bulk density and available water content influenced the phenanthrene transport mechanism phenomenon.

Sewage sludge has been used as a fertilizer in agriculture, but human exposure to toxins due to crop exposure has been reported. This study evaluated the uptake of essential and nonessential elements from soil (exposed to sewage sludge) to roots, shoots, and grains of corn, aiming to estimate the daily intake corn consumption to assess the associated health risk. Corn plants were grown in soil amended with 0, 5, 10, and 20 tons of sewage sludge per hectare (t/ha). Soil, root, shoot, and grain samples were analyzed by inductively coupled plasma mass spectrometry. In soil, sludge application at 10 and 20 t/ha enhanced the Zn, Cu, Mo, Cd, Pb, Hg, and Ni concentration compared to control soil. Normally, corn plants exhibited essential and nonessential element concentrations significantly higher in roots than in grains and shoots. Selenium was equally distributed in roots, shoots, and grains but Mo was preferentially stored in grains. Cadmium, As, and Pb were more efficiently trapped in roots than other elements. Considering the estimated daily intake, for Brazilians, the concentrations were below the toxicological or the dietary reference values. In conclusion, chemical elements were efficiently trapped in roots and therefore applying 5 t/ha proportion of sewage sludge might be a sustainable and cost-effective strategy, with a very lower risk of toxicity due to consumption of grains. In contrast, sewage sludge at 20 t/ha enhanced element levels in plant parts and in places with higher corn consumption, estimated daily intakes are expected to rise.

Atmospheric deposition can be an important source of ions to terrestrial and aquatic ecosystems. Previous studies have indicated that dry deposition of ions in and near large cities is greater than in nearby rural areas. However, few studies have compared dry deposition in and near smaller cities. We measured dry deposition of ions at various distances from Greenville, a smaller city in the piedmont of northwestern South Carolina. Dry deposition was estimated by exposure of artificial surfaces (glass Petri plates and paper filters) to the atmosphere at 13 locations during June–July 2008. Petri plates were expected to collect dust particles primarily, whereas filters were expected to collect both dust and gases. Fluxes measured by filters were significantly greater than those measured by Petri plates for nitrate and ammonium, suggesting that dry deposition of nitrogen in gases exceeded dry deposition in dust. Dry deposition of ammonium and nitrate declined significantly with distance from Greenville, and rates were significantly higher at urban than at rural locations. Also, dry deposition rates of ammonium correlated positively with road densities and traffic volumes around sampling locations, suggesting that automobiles were important sources of ammonia gas. Relationships between ammonium deposition and urban land cover and roads were stronger than for nitrate deposition, perhaps reflecting the influence of automobiles using catalytic converters. Base cation concentrations in dry deposition typically were below detection, precluding flux calculations. Overall, our results provide evidence that smaller cities influence atmospheric deposition of nitrogen, though perhaps not as strongly as larger cities.

Lichens absorb water, gases, dissolved substances, and especially pollutants by the entire surface, and they are considered to be the indicators of air quality. In our experiment, a sensitivity of Cladonia arbuscula subsp. mitis and Cladonia furcata lichens with the same photobiont Trebouxia was tested to nitrogen excess through a sensitivity of both the photobiont and mycobiont. Lichen ecophysiological parameters like chlorophyll a fluorescence, chlorophyll a integrity, the content of photosynthetic pigments, ergosterol, soluble proteins, thiobarbituric acid reactive substances, and secondary compounds were measured during two experiments that differed in time of nitrogen exposure. In the short-term experiment, also higher nitrogen concentrations were used to evaluate the dependence of different nitrogen concentrations. In the short-term experiment, lichens were soaked at the different solutions of ammonium nitrate (NH₄NO₃) for describing an immediate effect of range of NH₄NO₃ concentrations. In the long-term experiment, lichens were sprayed with low NH₄NO₃ concentrations for 3 months for evaluating the effect of naturally occurring low nitrogen concentrations. Results showed that lichens responded differently in spite of having the same photobiont. The mycobiont of C. arbuscula subsp. mitis was more sensitive than mycobiont of C. furcata. In higher nitrogen concentrations, the photobiont of C. furcata was more sensitive than C. arbuscula subsp. mitis photobiont. Both lichens exhibited signs of damage; therefore, we conclude that they are sensitive to nitrogen excess, while C. arbuscula subsp. mitis is more sensitive species. The secondary compound content did not change in neither of lichen species. Cladonia sp. response to nitrogen excess depends on length and nitrogen dose exposure.

Accumulations of mass loads of selected chemicals in roadside snowbanks were studied at five sites with various traffic densities in the city of Trondheim (Norway) by collecting snow samples throughout the winter period and analyzing them for 13 water quality constituents: pH, electrical conductivity (EC), alkalinity, Cl, Na, total suspended solids (TSS), Cd, Cr, Cu. Ni, Pb, W, and Zn. The resulting dataset was then supplemented by similar data collected earlier in the city of Luleå (Sweden). Regression analyses for individual sites indicated linear trends in unit-area constituent accumulations with time (0.65 < R ² < 0.95) and supported the assumption of linearity in further analyses. Principal component analysis (PCA) of the combined Luleå/Trondheim data revealed cause-effect relationships between the chemical mass loadings (TSS and trace metals) and three predictors: snow age (snow residence time (SRT)), traffic density (annual average density of traffic (AADT), and cumulative traffic volume (CTV = SRT × AADT). Cl and Na loads, originating from road salt applications in Trondheim only, did not display this trend. Two types of parsimonious models for predicting trace metal accumulations in winter-long roadside snowbanks were developed: (a) a linear regression model using CTV as a single predictor and predicting metal accumulations with a moderate certainty (0.37 < R ² < 0.66) and (b) multiple regression models using SRT, AADT, and snow water equivalent (SWE) as predictors. The latter models indicated good correlations between the mass loads and the predictors (0.64 < R ² < 0.77) and produced slightly better prediction accuracies (0.44 < R ² < 0.67) than the simpler model.

The diversity and spatial structure of soil fungi (SF) and arbuscular mycorrhizal fungi (AMF) communities in the southern taiga forest litter were studied in sites with two contrasting contamination levels with copper smelter emissions. The operational taxonomic unit richness and evenness in the communities of both target groups decreased under contamination. The community structure of contaminated and control areas differed for SF, whereas they were similar for AMF. According to spatial structure analysis results on a scale of tens of meters, a gradual change of composition with distance was revealed for the SF community within 30-m intervals in the control sites. No spatial autocorrelation was found for AMF in the control sites. However, pronounced patchiness was characteristic of both SF and AMF communities within 10 m of contaminated sites. In the contaminated area, no specific spatial structure determinants of the studied communities was found among environmental factors such as water content, heavy metal concentrations in the forest litter, sample plot localization relative to canopy density, and herb vegetation diversity and abundance. However, in the control sites, AMF richness depended on herb abundance and litter chemistry.

This work is a synthesis of a 5-year estimation of nitrogen balance at a semi-arid, semi-natural, undisturbed grassland site (Bugac). We measured the N input of atmospheric pollutants by wet and dry deposition of gases and aerosols, while we considered N output as NO and N₂O gases volatilized from soil. Besides measurements of soil fluxes, the denitrification-decomposition (DNDC) ecological model was also used and simulations were compared to and validated against the measured values. The daily flux simulations generally did not match well the measured data for N₂O and NO. In most cases, the mean fluxes were underestimated, though results of the comparison of monthly values suggest that model data, together with observed deposition data, are applicable to estimate the net N balance for grasslands. The calculated yearly N balance (net flux) between atmosphere and surface, without biological fixation and effect of grazing, ranged between −9.4 and −14 kg N ha⁻¹ year⁻¹as the sum of the measured deposition and emission terms, −11 to −15 and 0.9 to 2.9 kg N ha⁻¹ year⁻¹, respectively, between 2006 and 2010. Observed and modeled soil emissions were lower by one order of magnitude than atmospheric deposition. Considering the biological nitrogen fixation and the effect of grazing (effects of both grazed plant and excreta), the net nitrogen balance varies within −6.6 and −11 kg N ha⁻¹ year⁻¹. It seems — taking into account the high uncertainty in calculation due to the effect of grazing — that sources of nitrogen exceed the sinks; the surplus is probably mineralized in the soil.

A coupling technique is developed to predict the behavior of a buoyant river plume in a lake. The model incorporates a 3D hydrodynamic model (POMGL) and a 3D particle tracking model (Partic3D) for the far-field transport computations. The source conditions for the particle tracking model are obtained from a near-field model derived from the characteristics of the plume analyzed from extensive field studies on the Grand River plume, Lake Michigan. The empirical near-field model was developed to predict the geometry of the plume, dilution, and centerline trajectory near the river mouth, and to provide the concentration and location of the particles to be released in the far field. The coupled empirical-numerical model shows improved predictions in the near field versus the single numerical model. The present results strongly advocate the use of model combinations in order to improve coastal diffusion and transport processes. The primary application of the technique is in recreational water early-warning and forecasting systems that will estimate the immediate and short-term risk of exceeding pathogen indicator concentration criteria in lakes and coastal areas.

Eutrophication related to excess phosphorus (P) loadings continues to be an important issue for watersheds in North Carolina and other regions. Identifying the contributing sources of P in nutrient-sensitive waters is important for improving water quality. Prior studies have indicated that onsite wastewater treatment systems (OWS) can be a contributing source of P to surface waters, but more information is needed regarding their contribution relative to other wastewater treatment technologies. The goal of this study was to determine if P concentrations in groundwater and surface water were significantly different in a coastal plain watershed served by OWS in comparison to a watershed served by a municipal sewer system (MWS). Groundwater P concentrations were monitored at ten residential sites (five5 OWS and five MWS) once during each season (four times), and stream P concentrations and watershed exports were monitored monthly for 1 year (August 2011–August 2012). Groundwater in the OWS watershed had higher P concentrations than the MWS watershed. Stream P concentrations and P exports were also elevated in the OWS watersheds. However, the OWS were more efficient at reducing P prior to surface water discharge than the wastewater treatment plant that served the MWS watershed. The site-scale and watershed-scale P treatment efficiencies of OWS were between 73 and 99 %, whereas P treatment efficiency for the wastewater treatment plant was 54 %. While the OWS were efficient at reducing P concentrations and loads, OWS were still significant sources of P exports from the studied watershed. Potential contributions of P from OWS should be included in watershed nutrient management strategies along with other known sources such as agriculture and urban runoff if the strategies are to be considered comprehensive.