Atmospheric deposition in the Athabasca Oil Sands Region decreased exponentially with distance from the industrial center. Throughfall deposition (kg ha−1 yr−1) of NH4–N (.8–14.7) was double that of NO3–N (.3–6.7), while SO4–S ranged from 2.5 to 23.7. Gaseous pollutants (NO2, HNO3, NH3, SO2) are important drivers of atmospheric deposition but weak correlations between gaseous pollutants and deposition suggest that particulate deposition is also important. The deposition (eq ha−1) of base cations (Ca + Mg + Na) across the sampling network was highly similar to N + S deposition, suggesting that acidic deposition is neutralized by base cation deposition and that eutrophication impacts from excess N may be of greater concern than acidification. Emissions from a large forest fire in summer 2011 were most prominently reflected in increased concentrations of HNO3 and throughfall deposition of SO4–S at some sites. Deposition of NO3–N also increased as did NH4–N deposition to a lesser degree.

Excess nitrogen inputs to terrestrial ecosystems via human activities have deteriorated water qualities on regional scales. Urban areas as settlements of over half global population, however, were usually not considered in the analysis of regional water pollution. Here, we used a 72-month monitoring data of water qualities in Hangzhou, China to test the role of urban rives in regional nitrogen pollution and how they response to the changes of human activities. Concentrations of ammonium nitrogen in urban rivers were 3–5 times higher than that in regional rivers. Urban rivers have become pools of reactive nitrogen and hotspots of regional pollution. Moreover, this river pollution is not being measured by current surface water monitoring networks that are designed to measure broader regional patterns, resulting in an underestimation of regional pollution. This is crucial to urban environment not only in China, but also in other countries, where urban rivers are seriously polluted.

The open top chamber (OTC) method was used in a farmland to study the influence of different levels of O3 concentrations (40 ppb, 80 ppb and 120 ppb) on the enzymatic activity and metabolite contents of the antioxidation system of the winter wheat leaves during the jointing, heading and milk stage. The protective effect of exogenous spermidine (Spd) against the antioxidation of winter wheat under the O3 stress was investigated. With the increasing O3 concentrations and fumigation time, the injuries of the winter wheat leaves were observed to be more serious. For instance, when the O3 concentration reached 120 ppb, the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and nitrate reductase (NR) in the jointing stage decreased by 50.3%, 64.9%, 75.5% and 92.9%, respectively; peroxidase (POD) and glutathione reductase (GR) increased by 45.1% and 80.5%, respectively; the contents of malondialdehyde (MDA), ascorbic acid (AsA) and reduced glutathione (GSH) increased by 314.3%, 8.4% and 31.7%, respectively; and the soluble protein (SP) content decreased by 47.5%. The O3 stress also had significant impact on the contents of proline (Pro), NO3––N and NH4+–N of the winter wheat leaves. During the heading stage, when the O3 concentration was 40 ppb and 80 ppb, the content of Pro was 163.9% and 173.2% higher than that in the control group, respectively. But under 120 ppb, it was decreased by 42.4%. Exogenous application of Spd increased the activities of SOD, POD, CAT, APX and GR, as well as the contents of GSH and SP, but decreased the contents of MDA and AsA. This indicates that Spd is an effective antioxidant to relieve the O3 stress on winter wheat leaves, thereby might be applicable to protect winter wheat from the harm of O3.

The nutrient uptake and release by the mussels in relation with amount of food consumption are emphasised in this research. Results of the study demonstrate that about 16% of the total mass dry weight food consumed by the mussels was released as faeces. The depositions of particulate carbon, nitrogen, and phosphorus in mussel faeces were found to be 26.3, 5.7, and 0.6mg/day/indv respectively. Soluble inorganic nutrients such as NH4+-N (2.5mg/day/indv), and PO43−-P (0.6mg/day/indv) were also released as mussel excretion. The nutrient absorption efficiency for the green mussel body was found to be 65.1% for carbon, 62.1% for nitrogen, and 79.2% for phosphorus. Subsequently, green mussels can remove particulate carbon, nitrogen and phosphorus at 108.1, 13.5, and 4.6mg/day/indv from aquatic systems. Finally, the results can help in estimating the carrying capacity of mussel cultivation without deteriorating the water quality in marine ecosystems.

Soil thawing can affect the turnover of soil carbon (C) and nitrogen (N) and their release into the atmosphere. However, little has been known about the release of C and N during the thawing of alpine soils in the Qinghai-Tibet Plateau. This study investigated the effects of soil thawing on the release of CO₂, CH₄, and N₂O from alpine peatland soils and alpine meadow soils through an indoor experiment and determined the changes in the dissolved organic C (DOC), dissolved organic N (DON), NO₃ ⁻-N, NH₄ ⁺-N, and NO₂ ⁻-N concentrations in the soils after soil thawing. The freeze–thaw treatments were performed by incubating the soil columns at mild (−5 °C) and severe (−15 °C) for 14 days, and then at 5 °C for 18 days. The control columns were incubated at 5 °C. During thawing, the cumulative CO₂ emissions from the severely frozen alpine peatland soils and alpine meadow soils were 36 and 85 % higher than those from the control soils, and the cumulative N₂O emissions were 3.9 and 5.8 times higher than those from the control soils. However, the thawing after mild freezing produced no significant effects. The two freezing temperatures significantly increased the release of CH₄ from the alpine peatland soils, but the thawing of the severely frozen soils reduced the CH₄ uptake of the alpine meadow soils by 27 %. After the severely frozen alpine peatland soils thawed, the concentrations of DOC, DON, NO₃ ⁻-N, NH₄ ⁺-N, and NO₂ ⁻-N increased significantly, but NO₂ ⁻-N showed no significant changes for the alpine meadow soils. After thawing with mild freezing, DOC in the alpine peatland soils and NH₄ ⁺-N, NO₂ ⁻-N, and DOC in the alpine meadow soils showed no significant changes. This study indicates that the potential for release of C and N from alpine soils during thawing periods strongly depends on the freezing temperature and soil types.

The aim of this study was to investigate the synergistic effects of the process of iron-carbon microelectrolysis (ICME) followed by struvite (MAP) crystallization on treating antibiotic wastewater. Characteristics of ICME effluent depended mainly on the iron to carbon mass ratio (Fe/C). The optimum reaction conditions of Fe/C ratio of 2:1 and reaction time of 90 min were observed. The ICME effluent was further treated by MAP crystallization using Na₂HPO₄·12H₂O and MgCl₂·6H₂O as precipitation agents. The results showed that, the Mg²⁺/NH₄ ⁺-N/PO₄ ³⁻-P molar ratio of 1:1:1 and pH 8.5, were suitable for the crystallization process, which could obtain high-quality MAP containing 5.18 % N,10.23 % Mg, and 13.83 % P. Optimal total removal rate of COD and NH₄ ⁺-N removal rate achieved 84.6 and 89.9 %, respectively. The economic evaluation of NH₄ ⁺-N recovery by the synergistic process was also conducted, indicating that the synergistic process had the potential to benefit COD emission reduction and nitrogen recovery. Graphical Abstract The aim of this study was to investigate the effects of treating antibiotic wastewater using iron and carbon combined process of microelectrolysis and struvite (MAP) crystallization. The MAP was of high purity and good crystal morphology, which could be used as a slow-release fertilizer.

Biofiltration of an air stream polluted with diffuse CH₄ concentrations of 0.19 % (v v⁻¹) was carried out. These emissions can be encountered at different industrial facilities such as wastewater treatment plants and landfills. The effect of ammonium supplied in the nutrient solution was studied in a range from 0 to 1 g N-NH₄ ⁺ L⁻¹, taking account its effect on CH₄ removal efficiency (RE), CO₂ production, ammonium conversion and the occurrence of exopolymeric substances. Additional batch assays were performed in order to evaluate the most suitable pH and temperature ranges for the biomass used as inoculum. A conventional biofilter was operated along 225 days achieving maximum CH₄ elimination capacities of up to 11.2 g CH₄ m⁻³ h⁻¹, corresponding to REs of 62 %, using 0.52 g N L⁻¹ of ammonia as nitrogen source in the nutrient solution and operating at an empty bed residence time of 4.4 min. CO₂ production values confirmed that most of this elimination was biological and not absorption into the liquid phase. The occurrence of instability periods resulted in a clear increase of the soluble microbial products (SMPs) contained in the liquid phase, especially in the protein fraction, which could be used as a monitoring tool to follow the stress conditions of the biofilter. Results indicate interesting links between the performance of the biofilter and the presence of extracellular polysaccharide and protein concentration in the liquid phase, with increasing concentrations detected when the process was not stable.

Harmful algal bloom has posed great threat to drinking water safety worldwide. In this study, soils were combined with commercial nontoxic polyamine poly(epichlorohydrin–dimethylamine) (PN) and polymeric ferric sulfate (PFS) to obtain PN-PFS soils for Microcystis removal and eutrophic water remediation under static laboratory conditions. High pH and temperature in water could enhance the function of PN-PFS soil. Algal removal efficiency increased as soil particle size decreased or modified soil dose increased. Other pollutants or chemicals (such as C, P, and organic matter) in eutrophic water could participate and promote algal removal by PN-PFS soil; these pollutants were also flocculated. During PN-PFS soil application in blooming field samples, the removal efficiency of blooming Microcystis cells exceeded 99 %, the cyanotoxin microcystins reduced by 57 %. Water parameters (as TP, TN, SS, and SPC) decreased by about 90 %. CODMₙ, PO₄-P, and NH₄-N also sharply decreased by >45 %. DO and ORP in water improved. Netting and bridging effects through electrostatic attraction and complexation reaction could be the two key mechanisms of Microcystis flocculation and pollutant purification. Considering the low cost of PN-PFS soil and its nontoxic effect on the environment, we proposed that this soil combination could be applied to remove cyanobacterial bloom and remediate eutrophic water in fields.

High nitrogen (N) concentrations in rural domestic water supplies have been attributed to excessive agricultural N leaching into shallow groundwater systems; therefore, it is important to determine the impact of agriculture (e.g., rice production) on groundwater quality. To understand the impact of agricultural land use on the N concentrations in the shallow groundwater in subtropical central China, a large observation program was established to observe ammonium-N (NH₄-N), nitrate-N (NO₃-N), and total N (TN) concentrations in 161 groundwater observation wells from April 2010 to November 2012. The results indicated that the median values of NH₄-N, NO₃-N, and TN concentrations in the groundwater were 0.15, 0.39, and 1.38 mg N L⁻¹, respectively. A total of 36.3 % of the water samples were categorized as NH₄-N pollution, and only a small portion of the samples were categorized as NO₃-N pollution, based on the Chinese Environmental Quality Standards for Groundwater of GB/T 14848-93 (General Administration of Quality Supervision of China, 1993). These results indicated of moderate groundwater NH₄-N pollution, which was mainly attributed to intensive rice agriculture with great N fertilizer application rates in the catchment. In addition, tea and vegetable fields showed higher groundwater NO₃-N and TN concentrations than other agricultural land use types. The factorial correspondence analysis (FCA) suggested that the flooded agricultural land use types (e.g., single-rice and double-rice) had potential to impose NH₄-N pollution, particularly in the soil exhausting season during from July to October. And, the great N fertilizer application rates could lead to a worse NO₃-N and TN pollution in shallow groundwater. Hence, to protect groundwater quality and minimize NH₄-N pollution, managing optimal fertilizer application and applying appropriate agricultural land use types should be implemented in the region.

Electrolytic manganese residue (EMR) is a solid waste found in filters after sulphuric acid leaching of manganese carbonate ore, which mainly contains manganese and ammonia nitrogen and seriously damages the ecological environment. This work demonstrated the use of electrokinetic (EK) remediation to remove ammonia nitrogen and manganese from EMR. The transport behavior of manganese and ammonia nitrogen from EMR during electrokinetics, Mn fractionation before and after EK treatment, the relationship between Mn fractionation and transport behavior, as well as the effects of electrolyte and pretreatment solutions on removal efficiency and energy consumption were investigated. The results indicated that the use of H₂SO₄ and Na₂SO₄ as electrolytes and pretreatment of EMR with citric acid and KCl can reduce energy consumption, and the removal efficiencies of manganese and ammonia nitrogen were 27.5 and 94.1 %, respectively. In these systems, electromigration and electroosmosis were the main mechanisms of manganese and ammonia nitrogen transport. Moreover, ammonia nitrogen in EMR reached the regulated level, and the concentration of manganese in EMR could be reduced from 455 to 37 mg/L. In general, the electrokinetic remediation of EMR is a promising technology in the future.