The stability of community functioning in anaerobic ammonia oxidation (anammox) sludge adaptation to various salinity changes are concerned but not fully explored. In this study, two anammox reactors were designed in response to different salt levels and salt-adding methods. The reactor PI, run with small stepwise salt increments (0.5%–1.0%), removed >90% of nitrite and ammonium in the influent over the range of 0%–4% salt. By contrast, the reactor SI, run with a sharp salt increment (>2.5%), exhibited a reduced performance (by up to 44%) over the same salt range with a new steady state. The observed resilience times after salt perturbations indicated that the PI reactor recovered substantially and rapidly at all imposed salt levels. Principal coordinates analysis of 16S rRNA gene amplicon sequences revealed that bacterial community structures of the anammox sludge altered conspicuously in response to the salinity changes. However, quantitative PCR analysis showed that the shift in copy number of studied nitrogen-converting genes encoding hydrazine synthase (hzsA), bacterial and archaeal ammonia monooxygenases (amoA), nitrite oxidoreductase (nxrB), nitrite reductase (nirK), and nitrous oxide reductase (nosZ) was not significant (p > 0.05) in anammox sludge across the salt levels of 0.5%–4%, which suggests the stability of microbial community functioning in the osmoadaptation processes. The freshwater anammox Ca. Kuenenia showed high osmoadaptation by potentially adopting both high-salt-in and low-salt-in strategies to dominate in both reactors. The quantitative transcript analysis showed that the active anammox bacteria represented by hzsA transcripts in the SI reactor were approximately two orders of magnitude lower than those in the PI reactor during the long-term exposure to 4% salinity, manifesting the influence by the salt-increasing methods. These results provided new insight into osmo-adaptation of the anammox microbiome and will be useful for managing salinity effects on nitrogen removal processes.

Under anaerobic conditions, ammonium (NH₄⁺) can react with nitrite (NO₂⁻) and sulfate (SO₄²⁻), termed nitrite-anammox (NirAnammox) and sulfate-anammox (Sulfammox), respectively. However, how to remove NH₄⁺ and SO₄²⁻ together from leachate is unclear. In this study, NirAnammox and Sulfammox cooperatively achieved nitrogen and sulfate removal from leachate using a biological process at low temperature (14–15 °C). NH₄⁺, total nitrogen (TN), and SO₄²⁻ concentrations in the influent were 610–700, 670–900, 1870–1920 mg/L, respectively, and 10 ± 1, 35 ± 3, and 897.7 ± 10 mg/L, respectively, in the effluent. Sulfammox, and NirAnammox (including partial nitrification) removed 44.2% and 35.46% of the NH₄⁺, respectively. Therefore, because leachate contains high concentrations of NH₄⁺ and SO₄²⁻, NirAnammox and Sulfammox can easily occur together, with nitrogen removal by Sulfammox being more than NirAnammox. The relative abundance of dominant bacteria of the Sulfammox were 10–20 times that of Candidatus Kuenenia (NirAnammox) in each reactor. Organic matter negatively affected NirAnammox, but not Sulfammox. Dissolved oxygen negatively affected both.

This study developed a process of genetically engineered bacteria Rhodococcus erythropolis expressing Nirs and AMO combined with membrane bioreactor (MBR), nanofiltration (NF) and reverse osmosis (RO) membrane (pRho-NA-MNR) for advanced treatment of landfill leachate. Results demonstrated that pRho-NA-MNR presented higher removal rate of chemical oxygen demand (COD), biological oxygen demand (BOD), ammonia nitrogen (N–NH₄), total nitrogen (TN) and total organic carbon (TOC) than activated sludge (AS-MNR) system. Administration of pRho-NA increased nitrification by converting N–NH₄ to nitrite (N–NO₂) and Nitrate (N–NO₃), and promoting denitrification by converting N–NO₂ to nitrogen (N₂) in the landfill leachate treatment, promoted the pH control, increased sludge activity and effluent yield, shortened phase length adaptation under alternating aerobic-anoxic conditions. pRho-NA increased the nitration and denitrifying rate in the aerobic and anaerobic stage in the system by increasing Cyt cd1 and Cyt c expression in the activated sludge. Nitrogen removal by nitrification and denitrification was positively correlated to the concentration of Nirs and AMO expression. Treatment with pRho-NA promoted pollutant removal efficiency of membrane bioreactor, nanofiltration and reverse osmosis membrane processes in landfill leachate. In conclusion, data suggest that pRho-NA-MNR facilitates the formation of granular sludge and enhances comparable removal of nitrogen and organic compounds, indicating the practice of this process should be considered in landfill leachate treatment system.

The paper presents the quality status of 14 brands of bottled water, with sources of groundwaters from different mountain areas alongside the Carpathian Mountains from Romania. A number of 12 physico-chemical parameters (ammonium, bicarbonate, electrical conductivity, carbonate, chemical oxygen demand, chloride, nitrate, nitrite, pH, sulphate, total hardness, turbidity), 9 metals and metalloids (Li, B, Na, Mg, Al, K, Ca, Sr, Ba) and 17 heavy metals (V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Mo, Ag, Cd, In, Tl, Pb, Bi) were determined and studied. The quality status, the potential contamination and the health risk assessment of bottled waters were assessed, by using the drinking water quality index, the heavy metal pollution index, the heavy metal evaluation index, the degree of contamination and the human health risk indices. Hierarchical cluster analysis was applied, indicating similarities among the studied bottled waters based on their metal content. The Piper diagram reveals that the majority of bottled water samples fall into the Ca, Mg, Na, K, Cl⁻, SO₄²⁻, CO₃²⁻, HCO₃⁻ categories. The quality of bottled waters based on the indices results indicated marginal, poor and very-poor quality status of the studied water samples, while the health risk assessment indices presented potential risks at aluminium, chloride and nitrate for the inhabitants who used those water samples with the purpose of drinking. The pollution indices with respect to metals generally reflected a low pollution status. This study represents the first attempt in assessing the overall quality of some bottled water collected from the mountain area, Romania, likewise assessing the comprehensive human health risk due to several chemical elements determined in water in amounts around and exceeding the maximum allowable concentrations. This research can be useful for development of potential strategies for risk control and management in the field of drinking water.

This study developed a lightweight air composition measuring equipment (ACME) mounted in unmanned aerial vehicles (UAVs) to measure the vertical distribution characteristics of PM₂.₅ chemical species in the micro-scale urban environment for the first time. 212 samples collected from 0 to 350 m above ground level were analyzed for water-soluble ions. The concentrations of most ions on the above ground level were higher than that on the ground surface during the sampling period. The measurements of the total ion concentrations were approximately 54 to 26% of the PM₂.₅ mass concentrations on the ground surface. The concentrations of NH₄⁺ and NO₃⁻ decreased with increases in the height from the ground, which may be related to the influence of the vehicle emissions and human activities. NO₂⁻ and SO₄²⁻ both had a peak concentration on the higher vertical altitude at night in the sea-land wind system. In the southern wind system, the emissions of sea salts, dust, and stationary pollution, might be transported by the regional prevailing airflow from the southern coastal area, were the major pollutant sources above the boundary layer. The vertical distribution of ionic concentrations and wind field provided information concerning changes in pollutant transport and source regions that affect the local air quality. The ACME mounted in UAVs is the feasible and convenient method to fast understand the vertical distributions of aerosol chemical species. It provides important information about the accumulation and diffusion effects by the boundary layer variation to aerosol characteristics, which is difficulty observed from the conventional ground-based measurements. In future, this technology is the useful application for investigating the pollutant species emitted from the smokestack and the sudden pollution accident.

In order to understand the impacts of regional emission changes and local tourism on sulfur and nitrogen wet deposition in Jiuzhaigou National Nature Reserve of southwestern China, wet deposition was monitored at a background site (Rize) and a tourist-affected site (PE: park entrance) in the reserve during 2015–2016. The observation data were compared between Rize and PE and between 2010–2011 and 2015–2016 monitoring campaigns. Also, the observation data were used in the Positive Matrix Factorization (PMF) model to identify the major sources of sulfur and nitrogen wet deposition. The results show that although local tourism emissions had considerable contributions to NH₄⁺, NO₂⁻, NO₃⁻, and SO₄²⁻ concentrations in wet deposition (p < 0.05), most of the annual Volume Weighted Mean (VWM) concentrations of these four ions were likely from emissions outside Jiuzhaigou. Annual wet deposition fluxes of the four ions were also affected more by precipitation and regional emissions than by local emissions. Although annual precipitation was higher at Rize (818 mm) during 2015–2016 than at another background site near Long Lake (LL: 752 mm) during 2010–2011, the annual concentrations and fluxes of SO₄²⁻ and NO₃⁻ wet deposition decreased by 77% and 74% for SO₄²⁻ and by 12% and 19% for NO₃⁻, respectively, most likely due to regional emission reductions. Similar large reductions in SO₄²⁻ and NO₃⁻ concentrations have been also found in some other sites in southwestern China. In contrast, the annual concentration and flux of NH₄⁺ wet deposition at Rize during 2015–2016 were 1.4 and 1.2 times of that measured at LL during 2010–2011, respectively. The results of source apportionment analysis and tour bus emission estimates suggest that elevated NH₄⁺ wet deposition was possibly related to NH₃ emissions from local tour buses, but additional studies on NH₃ emissions from tour buses in the reserve are needed to confirm this.

Effects of antibiotics on the transformation of nitrate and the associated N₂O release in paddy fields are obscure. Using soil slurry experiments combined with ¹⁵N tracer techniques, the influence of tetracycline and sulfamethazine (applied alone and in combination) on the denitrification, anaerobic ammonium oxidation (anammox), dissimilatory nitrate reduction to ammonium (DNRA) and N₂O release rates in the paddy soil were investigated, while genes related to nitrate reduction and antibiotic resistance were quantified to explore the microbial mechanisms behind the antibiotics’ effects. The potential rates of denitrification, anammox, and DNRA were significantly (p < 0.05) reduced, which were mainly attributed to the inhibitory effects of the antibiotics on nitrate-reducing microbes. However, the N₂O release rates were significantly (p < 0.05) stimulated by the antibiotic treatments (0.6–6000 μg kg⁻¹ soil dry weight), which were caused by the different inhibition effects of antibiotics on N₂O production and N₂O reduction as suggest by the changes in abundance of nirS (nitrite reduction step) and nosZ (N₂O reduction to N₂ step) genes. Antibiotic resistance gene (tetA, tetG, sulI, and sulIII) abundances were significantly (p < 0.05) increased under high antibiotic exposure concentrations (>600 μg kg⁻¹ soil dry weight). Our results suggest that the widespread occurrence of antibiotics in paddy soils may pose significant eco-environmental risks (nitrate accumulation and greenhouse effects) by altering nitrate transformation processes.

Toxicity and uptake of nano-CeO2 (nCeO2) in edible vegetables are not yet fully understood. In the present study, we grew romaine lettuce in sand amended with nCeO2. At high concentrations (1000 and 2000 mg/kg), nCeO2 diminished the chlorophyll content by 16.5% and 25.8%, respectively, and significantly inhibited the biomass production. nCeO2 (≥100 mg/kg) altered antioxidant enzymatic activities and malondialdehyde levels in the plants. nCeO2 (≥500 mg/kg) triggered a remarkable increase of nitrate-N level in the shoots, which can be converted to toxic nitrite in humans thereby posed risk to human health. Concentration dependent accumulation of Ce in the plant tissues was observed. X ray absorption near edge spectroscopy (XANES) results indicate that Ce presented as nCeO2 and CePO4 in the roots while as nCeO2 and Ce carboxylates in the shoots. Chelation of Ce3+ by citric acid or precipitation of Ce3+ by PO43− reduced the translocation and toxicity of nCeO2, indicating that release of Ce3+ played a critical role in the toxicity nCeO2.

The main aim of this study was to investigate the feasibility of using soybean meal added with papain to replace half of the fishmeal used in the moist pellets (49% fishmeal and 45% trash fish) developed by the Hong Kong Agriculture, Fisheries and Conservation Department (AFCD) for culturing marine fish. Gold-lined seabream (Rhabdosargus sarba), brown spotted grouper (Epinephelus bleekeri) and pompano (Trachinotus blochii) were farmed at one of the research stations (Kat-O) of AFCD, for a period of 340 days. Results indicated that diets containing papain resulted in better fish growth (reflected by relative weight gain and feed conversion ratio) than diets without papain. In general, wet weight gain of fish depends on the amount of papain added in diet rather than the diet composition. Soybean used in conjunction with papain also contributed to a more effective growth than fish fed with the moist pellets alone. A laboratory experiment (using tanks) was conducted to study the effects of the diets on concentrations of ammonia, nitrite and nitrate in the tank water. Results showed that concentrations of ammonia and nitrate were significantly lower (p < 0.05) when the fish were fed with papain-supplemented (with or without soybean meal) diets. It is envisaged that by using plant protein incorporated with enzymes could promote better growth of marine fish and lower the adverse impact of trash fish and fishmeal on water quality of the mariculture zones.

Increases in water temperature, as a result of climate change, may influence biogeochemical cycles, sediment-water fluxes and consequently environmental sustainability. Effects of rising temperature on dynamics of nitrate, nitrite, ammonium, dissolved inorganic nitrogen (DIN), dissolved reactive phosphorus (DRP), dissolved organic carbon (DOC) and gaseous nitrogen (N2 and N2O) were examined in a subtropical river (the Jiulong River, southeast China) by microcosm experiments. Slurry sediments and overlying water were collected from three continuous cascade reservoirs, and laboratory incubations were performed at four temperature gradients (5 °C, 15 °C, 25 °C and 35 °C). Results indicated: (1) warming considerably increased sediment ammonium, DIN and DOC fluxes to overlying water; (2) warming increased retention of nitrate, and to a lesser extent, nitrite, corresponding to increases in N2 and N2O emission; (3) DRP was retained but released from Fe/Al-P enriched sediments at high temperature (35 °C) due to enhanced coupled transformation of carbon and nitrogen with oxygen deficiency. Using relationships between sediment fluxes and temperature, a projected 2.3°C-warming in future would increase ammonium flux from sediment by 7.0%–16.8%, while increasing nitrate flux into sediment by 8.9%–28.6%. Moreover, substrates (e.g., grain size, carbon availability) influenced nutrient delivery and cycling across cascade reservoirs. This study highlights that warming would increase bioreactive nutrient (i.e., ammonium and phosphate) mobilization with limited gaseous N removal from sediments, consequently deteriorating water quality and increasing eutrophication with future climate change.