A 3-month-long experiment was conducted to ascertain the effects of different concentrations of myclobutanil (0.4 mg kg⁻¹ soil [T1]; 1.2 mg kg⁻¹ soil [T3]; and 4 mg kg⁻¹ soil [T10]) on soil microbial biomass, respiration, and soil nitrogen transformations using two typical agricultural soils (Henan fluvo-aquic soil and Shanxi cinnamon soil). Soil was sampled after 7, 15, 30, 60, and 90 days of incubation to determine myclobutanil concentration and microbial parameters: soil basal respiration (RB), microbial biomass carbon (MBC) and nitrogen (MBN), NO−3–N and NH+4–N concentrations, and gene abundance of total bacteria, N2-fixing bacteria, fungi, ammonia-oxidizing archaea (AOA), and ammonia-oxidizing bacteria (AOB). The half-lives of the different doses of myclobutanil varied from 20.3 to 69.3 d in the Henan soil and from 99 to 138.6 d in the Shanxi soil. In the Henan soil, the three treatments caused different degrees of short-term inhibition of RB and MBC, NH+4–N, and gene abundance of total bacteria, fungi, N2-fixing bacteria, AOA, and AOB, with the exception of a brief increase in NO−3–N content during the T10 treatment. The MBN (immobilized nitrogen) was not affected. In the Shanxi soil, MBC, the populations of total bacteria, fungi, and N2-fixing bacteria, and NH+4–N concentration were not significantly affected by myclobutanil. The RB and MBN were decreased transitorily in the T10 treatment. The NO−3–N concentrations and the abundance of both AOA and AOB were erratically stimulated by myclobutanil. Regardless of whether stimulation or suppression occurred, the effects of myclobutanil on the two soil types were short term. In summary, myclobutanil had no long-term negative effects on the soil microbial biomass, respiration, and soil nitrogen transformations in the two types of soil, even at 10-fold the recommended dosage.

Sediment dredging is considered an effective restoration method to reduce internal loading of nitrogen (N) and phosphorus (P) in eutrophic lakes. However, the effect of dredging on N release from sediments to overlying water is not well understood. In this study, N exchange and regeneration across the sediment-water interface (SWI) were investigated based on a one-year simulated dredging study in Lake Taihu, China. The results showed low concentrations of inorganic N in pore water with low mobilization from the sediments after dredging. The calculated fluxes of NO3−-N from post-dredged sediments to overlying water significantly increased by 58% (p < 0.01), while those of NH4+-N dramatically decreased by 78.2% after dredging (p < 0.01). N fractionation tests demonstrated that the contents and lability of N generally declined in post-dredged sediments. Further high-throughput sequencing analysis indicated that relative abundance of the bacterial communities decreased, notably by 30% (compared with undredged sediments). The estimated abundance of Nitrospira enhanced, although the relative abundance of Thiobacillus, Sterolibacterium, Denitratisoma, Hyphomicrobium, Anaeromyxobacter and Caldithrix generally declined after dredging. Therefore, dredging reduced N mobilization from the sediments, which primarily due to decreases in N mobility, in organic matter (OM) mineralization potential and in the bacterial abundance of post-dredged sediments. Overall, to minimize internal N pollution, dredging is capable of effectively reducing N release from sediments. In addition, the negative side effect of dredging on removal of NO3−-N and NO2−-N from aquatic ecosystems should be paid much more attention in future.

The concentrations of nutrients (NO2–N, NO3–N, NH4–N, PO4–P, and SiO3–Si) and their ratios in the Lembeh Strait were estimated in April 2013, off the northeastern coast of Sulawesi in Indonesia. The concentrations of dissolved inorganic nitrogen (DIN) (NO2–N+NO3–N+NH4–N) and PO4–P were low, with a maximum of 0.181 and 0.007mg/L, respectively. P was found to be the limiting factor controlling phytoplankton growth overall. According to a potential eutrophication assessment model, both the surface water and the water at a depth of 15m were classified as water 1 (poor nutrition). This study provides baseline information including chemical datasets for future pollution monitoring and management programs in this area.

Few studies have been carried out so far for measuring concentrations of NH3, NO2 and O3 in plastic greenhouses. In this study, NH3, NO2 and O3 concentrations were measured with passive sampler technology in a plastic greenhouse located in the Changsha suburb in southern China over a one and a half month period (November 30, 2008 to January 11, 2009). Soil in the greenhouse was subjected to four treatment (T) types (no N fertilizer T1, common urea T2, coated urea T3 and common urea with nitrification inhibitor dicyandiamide (DCD) T4. The average concentrations (μg/m3) of NH3, NO2 and O3 in descending order was: T4 (31.66) > T2 (25.93) > T3 (23.52) > T1 (7.96), T2 (10.99) > T3 (8.16) > T4 (7.48) > T1 (5.20), T2 (75.05) > T3 (64.20) > T4 (63.85) > T1 (49.02), respectively. This implied that photochemical reactions took place and that harmful gases accumulated after application of N fertilizer in the plastic greenhouse. DCD inhibited the conversion of ammonium to nitrate, increased NH3 volatilization and decreased NO2 level. The coated urea decreased the emissions of NH3 and increased nitrogen use efficiency. We found significant positive correlations (p < 0.01) between temperature and both NH3 and NO2 levels. Correlations between soil pH and both NH3 and NO2 concentrations were also significant (p < 0.01). The O3 average concentration from March 31, 2009 to April 10, 2009 in the higher latitude of the Yinchuan suburb in northern China was two times greater than that in the Changsha suburb in southern China. The O3 daily concentrations in the Yinchuan suburb exceeded 160 μg/m3 (i.e., China's Grade I standard), and the maximal value 214.83 μg/m3 exceeded 200 μg/m3 (i.e., China's Grade III standard).

The effect of titanium dioxide nanoparticles (TiO₂ NPs) on biological wastewater treatment in a sequencing batch reactor was investigated. The overall removal of chemical oxygen demand (COD) and NH₄ ⁺-N were relatively unaffected; efficiencies remained at >95 % and around 99 %, respectively, after 30 days of continuous exposure to the NPs. However, TiO₂ NPs resulted in increased conversion of NO₂ ⁻-N to NO₃ ⁻-N and caused slight inhibition effect on denitrification, with the total nitrogen removal reduced from 95 to 90 %. Several shifts in the bacteria community composition were noted. However, the overall community structure and biodiversity remained relatively unchanged. The polysaccharide content in the extracellular polymeric substances (EPS) was generally unaffected, suggesting a low potential of substantial shock or damage that may result in cytoplasmic leakage. However, a decrease in protein content occurred and indicated the inhibitive effects of the NPs. TiO₂ NPs were removed in the system mainly via deposition into the sludge. The removal efficiency decreased from 90 to 70 % after 4 weeks, due to sorption saturation as well as the change in the EPS content of the activated sludge.

Nitrogen pollution in ground and surface water significantly affects the environment and its organisms, thereby leading to an increasingly serious environmental problem. Such pollution is difficult to degrade because of the lack of carbon sources. Therefore, an electrochemical and biological coupling process (EBCP) was developed with a composite catalytic biological carrier (CCBC) and applied in a pilot-scale cylindrical reactor to treat wastewater with a carbon-to-nitrogen (C/N) ratio of 2. The startup process, coupling principle, and dynamic feature of the EBCP were examined along with the effects of hydraulic retention time (HRT), dissolved oxygen (DO), and initial pH on nitrogen removal. A stable coupling system was obtained after 51 days when plenty of biofilms were cultivated on the CCBC without inoculation sludge. Autotrophic denitrification, with [Fe²⁺] and [H] produced by iron–carbon galvanic cells in CCBC as electron donors, was confirmed by equity calculation of CODCᵣ and nitrogen removal. Nitrogen removal efficiency was significantly influenced by HRT, DO, and initial pH with optimal values of 3.5 h, 3.5 ± 0.1 mg L⁻¹, and 7.5 ± 0.1, respectively. The ammonia, nitrate, and total nitrogen (TN) removal efficiencies of 90.1 to 95.3 %, 90.5 to 99.0 %, and 90.3 to 96.5 % were maintained with corresponding initial concentrations of 40 ± 2 mg L⁻¹ (NH₃–N load of 0.27 ± 0.01 kg NH₃–N m⁻³ d⁻¹), 20 ± 1 mg L⁻¹, and 60 ± 2 mg L⁻¹ (TN load of 0.41 ± 0.02 kg TN m⁻³ d⁻¹). Based on the Eckenfelder model, the kinetics equation of the nitrogen transformation along the reactor was N ₑ = N ₀ exp (−0.04368 h/L¹.⁸⁴³⁸). Hence, EBCP is a viable method for advanced low C/N ratio wastewater treatment.

Industrial production of poultry meat is associated with indirect environmental impacts such as contributing to climate change and deforestation and other direct impacts such as the deterioration of the quality of surface waters. Poultry industry effluents are rich in organic matter, nitrogen, and phosphorus; nutrients can be removed from wastewater through the use of macrophytes and periphyton. An essay in mesocosms with poultry industry wastewater recirculation was developed in the presence and absence of a native macrophyte Spirodela intermedia and periphyton from a lowland stream (La Choza stream, Buenos Aires) where the effluent is poured. The diffusion of O₂, increased by water recirculation, had the effect of increasing the concentration of dissolved oxygen in wastewater. The presence of S. intermedia and algae periphyton significantly contributed to the removal rates (%) of solids (69.7 ± 3.9), ammonium nitrogen (84.0 ± 3.4), and total phosphorus (38.1 ± 1.8) from residual water and favored nitrification. The dominance of Bacillariophyceae on other groups of algae of periphyton and the low representation of Euglenophyceae indicated an advanced stage of the effluent treatment process at the end of the assay.

This study aimed to investigate the characteristics of the event mean concentration (EMC) and first flush effect (FFE) during typical rainfall events in outfalls from different drainage systems and functional areas. Stormwater outfall quality data were collected from five outfalls throughout Fuzhou City (China) during 2011–2012. Samples were analyzed for water quality parameters, such as COD, NH₃-N, TP, and SS. Analysis of values indicated that the order of the event mean concentrations (EMCs) in outfalls was intercepting combined system > direct emission combined system > separated system. Most of the rainfall events showed the FFE in all outfalls. The order of strength of the FFE was residential area of direct emission combined system > commercial area of separated system > residential area of intercepting combined system > office area of separated system > residential area of separated system. Results will serve as guide in managing water quality to reduce pollution from drainage systems.

The use of reclaimed water (RW) for irrigation alleviates agricultural water shortages. However, N₂O emissions and N fertilizer transformations in soils irrigated with RW under different N fertilizer types and soil moisture contents are poorly understood. A 216-h laboratory incubation experiment was conducted to evaluate the effects of irrigation water types (RW and fresh water, FW), N fertilizer types (¹⁵N-labeled KNO₃ and (NH₄)₂SO₄), and soil moisture contents at 40, 60, and 90 % water-filled pore space (WFPS) on N₂O emissions and N fertilizer transformations in intact soil cores. The results showed that cumulative N₂O emissions ranged from 3.78 to 36.30 mg N m⁻², and fertilizer-derived N₂O losses accounted for 0.14–2.44 % of N fertilizers, while fertilizer-derived N residues (NO₃ ⁻-N + NH₄ ⁺-N) accounted for 10.16–26.95 % of N fertilizers. The N₂O emissions at 40 % WFPS and fertilizer-derived N residues at 60 % WFPS in soils irrigated with RW were significantly (10.98 and 20.95 %, respectively) higher than those irrigated with FW, while fertilizer-derived N₂O losses at 60 % WFPS in soils irrigated with RW were 10.26 % higher than those irrigated with FW. The N₂O emissions and fertilizer-derived N₂O losses in soils amended with (NH₄)₂SO₄ at 40 and 60 % WFPS were significantly (26.61–178.84 %) larger than those amended with KNO₃, while fertilizer-derived N residues in soils amended with KNO₃ were significantly (41.47 %) higher than those amended with (NH₄)₂SO₄. The N₂O emissions significantly increased with increasing soil moisture content. Our results indicate that N fertilizer types and soil moisture contents are the two important factors regulating N₂O emissions and N fertilizer transformations. When RW irrigation is used, controlling soil moisture contents within 41 and 60 % WFPS (the optimum is 46 % WFPS) and application of KNO₃ can reduce N₂O emissions and fertilizer-derived N₂O losses, and correspondingly increase fertilizer-derived N residues, which can contribute to climate change mitigation.

This outdoor research investigated the variations in soil ammonium (NH₃-N), nitrite (NO₂-N), nitrate (NO₃-N), total organic nitrogen (TON), and microbial biomass carbon (MBC) in bioretention tanks. Two biretention tanks (tank 1#: The depth of 0–20 cm was vacant aquifer layer; 20–90 cm, filled with the planting soil; 90–105 cm, filled with gravel. tank 3#: 0–20 cm was aquifer layer, 20–50 cm, filled with the planting soil; 50–90 cm, filled with blast furnace slag and sand; 90–105 cm, filled with gravel) were used with simulated rainwater discharge experiments to obtain soil samples at intervals of 1 h before the inflow and 24 h after the end of inflow. Results indicate that soil nitrogen (N) and MBC in two bioretention tanks were mainly captured at 10∼30 cm depth in soil; the content of soil NH₃-N exhibited a trend of initial decline but increase with time; the content of NO₂-N varied from 0.011 to 0.024 g/kg, and the change regularity was similar with the NH₃-N; different from the NH₃-N and NO₂-N, soil NO₃-N exhibited a trend of declining; while TON exhibited a trend of declining after slightly increase. Meanwhile, the content of NH₃-N and NO₃-N at 50 cm depth in tank 1# was slight lower than those at 10 and 30 cm; conversely, the discrepancy at the different depths in tank 3# was small. The contents of soil NH₃-N and NO₂-N before inflow were less than those after inflow, but it was adverse for NO₃-N. The NO₃-N leaching in bioretention system is a main reason for poor N removal in runoff. The content of MBC ranged from 1.055 to 1.847 g/kg and exhibited a trend of decline after increase. Furthermore, the content of MBC and TN has good linear correlation in bioretention tanks (R ² > 0.8), but it has general performance with TP (R ² > 0.5). The immobilization of NH₃-N, NO₂-N, and NO₃-N at the planting soil layer in tank 1# was greater than that in tank 3#. The N interception differences in the two tanks resulted from different infiltration rates of their underlying fillers.