Ecosystem anthropogenic enrichments enhance Chroococcus abundance and suppress Anabaena during cyanobacterial-dominated spring blooms in the Pengxi River, Three Gorges Reservoir, China.

Taxa-specific responses to the increasing anthropogenic eutrophication offer promising insights for mitigating harmful algal blooms (HABs) in freshwaters. The present study evaluated the HABs species dynamics in response to the ecosystem anthropogenic enrichment during cyanobacterial-dominated spring HABs in the Pengxi River, Three Gorges Reservoir, China. Results show significant cyanobacterial dominance with a relative abundance (RA = 76.54 %). The ecosystem enrichments triggered shifts in the HABs community structure from Anabaena to Chroococcus, especially in the culture involving iron (Fe) addition (RA = 66.16 %). While P-alone enrichment caused a dramatic increase in the aggregate cell density (2.45 × 108 cells L-1), the multiple enrichment (NPFe) led to maximum biomass production (as chl-a = 39.62 ± 2.33 µgL-1), indicating that nutrient in conjunction with the HABs taxonomic characteristics e.g., tendency to possess high cell pigment contents rather than cell density can potentially determine massive biomass accumulations during HABs. The stimulation of growth as biomass production demonstrated by both P-alone and the multiple enrichments, NPFe indicates that although P exclusive control is feasible in the Pengxi ecosystem, it can only guarantee a short-term reduction in HABs magnitude and duration, thus a lasting HABs mitigation measure must consider a policy recommendation involving multiple nutrient management, especially N and P dual control strategy. The present study would adequately complement the concerted effort in developing a rational predictive framework for freshwater eutrophication management and HABs mitigations in the TGR and elsewhere with similar anthropogenic stressors.

Dissimilatory nitrate reduction to ammonium in four Pseudomonas spp. under aerobic conditions.

Dissimilatory nitrate reduction to ammonium (DNRA) has an important role in soil nitrogen retention and is considered to be constrained to anaerobic conditions. However, a recent study found that Pseudomonas putida Y-9 is capable of DNRA under aerobic conditions. In this study, four species of Pseudomonas spp. were found to produce ammonium during the nitrite reduction process under aerobic conditions, similar to the Y-9 strain. The detectable ammonium in the culture supernatant during the nitrite reduction process for each of the four strains originated intracellularly. A subsequent 15N isotope experiment showed that these four strains were able to transform 15NO2 - to 15NH4 + in 3 h under aerobic conditions. The NirBD sequence in each of the four strains showed high similarity with that in the Y-9 strain (approximately 94.61%). Moreover, the nirBD sequences in the four strains and the Y-9 strain were all similar to those of other Pseudomonas spp., while they were relatively distant in terms of their phylogenetic relationship from those of other genera. Overall, these results suggest that these four strains of Pseudomonas spp. are capable of DNRA under aerobic conditions, which might be attributed to the existence of nirBD.

Metabolites dynamics exacerbated by external nutrients inputs into a Ceratium hirundinella-dominated bloom in the Pengxi River, Three Gorges Reservoir, China.

Secondary metabolites (toxins) production during harmful algal blooms (HABs) further increases the public health risks associated with water quality deterioration from anthropogenic eutrophication. In the present study, the dynamic pattern in the production of metabolites under different nutrient conditions in Ceratium-dominated spring HABs was investigated in Pengxi River, China. Results revealed five (5) important toxins all attributable to the Dinophyceae including azaspiracid 2&4, okadaic acid, tetrodotoxin, brevetoxin, and saxitoxin, each exhibiting certain levels of specificity to the ecosystem enrichments. In effect, while the production of azaspiracid 2 and okadaic acid was N-driven, azaspiracid 4 and tetrodotoxin were enhanced by Ca enrichment. The ambient HABs community structure shows absolute ecosystem dominance by a dinoflagellate, Ceratium hirundinella with relative abundance ((RA = 78.81%, p Ë‚ 0.05). However, P enrichment triggered a slight shift (p ≥ 0.05) in the HABs species structure within the cyanobacteria strictly represented by Chroococcus minor (RA = 26.60%) and Dolichospermum circinalis (RA = 23.91%) initiating possible emergency dominance. The effect of nutrient addition on biomass production as chlorophyll-a (Chl-a) confirmed a P-limited ecosystem juxtaposed by a secondary limitation by Ca. The significant stimulation on biomass as Chl-a from day 3 through day 4 by N and the multiple enrichments designated as NPFeCa was attributed to luxury consumption rather than limitation following N repletion thus delaying biomass accumulation. The study, therefore, offers useful insights into the dynamic pattern of toxins during spring HABs while it also provides comprehensive knowledge of the HABs impact predictions in the TGR.

Output characteristics and driving factors of non-point source nitrogen (N) and phosphorus (P) in the Three Gorges reservoir area (TGRA) based on migration process: 1995-2020.

Although physical models at present have made important achievements in the assessment of non-point source pollution (NPSP), the requirement for large volumes of data and their accuracy limit their application. Therefore, constructing a scientific evaluation model of NPS nitrogen (N) and phosphorus (P) output is of great significance for the identification of N and P sources as well as pollution prevention and control in the basin. We considered runoff, leaching and landscape interception conditions, and constructed an input-migration-output (IMO) model based on the classic export coefficient model (ECM), and identified the main driving factors of NPSP using geographical detector (GD) in Three Gorges Reservoir area (TGRA). The results showed that, compared with the traditional export coefficient model, the prediction accuracy of the improved model for total nitrogen (TN) and total phosphorus (TP) increased by 15.46 % and 20.17 % respectively, and the error rates with the measured data were 9.43 % and 10.62 %. It was found that the total input volume of TN in the TGRA had declined from 58.16 × 104 t to 48.37 × 104 t, while the TP input volume increased from 2.76 × 104 t to 4.11 × 104 t, and then decreased to 4.01 × 104 t. In addition Pengxi River, Huangjin River and the northern part of Qi River were high value areas of NPSP input and output, but the range of high value areas of migration factors has narrowed. Pig breeding, rural population and dry land area were the main driving factors of N and P export. The IMO model can effectively improve prediction accuracy, and has significant implications for the prevention and control of NPSP.

Spatiotemporal characteristics of air pollution in Chengdu-Chongqing urban agglomeration (CCUA) in Southwest, China: 2015-2021.

Studying the spatiotemporal characteristics of air pollutants in urban agglomerations and their response factors will help to improve the quality of urban living. In combining air quality monitoring data and wavelet analysis from the Chengdu-Chongqing urban agglomeration (CCUA), this study assessed the spatiotemporal distribution characteristics and influential factors of air pollutants on daily, monthly and annual scales. The results showed that the concentration of air pollutants in the CCUA has decreased year by year, and air quality has improved. Except for O3, pollutants in autumn and winter were higher than those in summer. The spatial distribution of air pollutants was obvious distributed in Chengdu, Chongqing, Zigong and Dazhou. Pollution incidents were mainly concentrated in winter. The 6 air pollutants and air quality index (AQI) have dominant periods on multiple time scales. AQI showed positive coherence with PM2.5 and PM10 on multiple time scales, and obvious positive coherence with SO2, CO, NO2 and O3 in the short term scale. AQI was not strongly correlated with the fire point, but exhibited obvious negative coherence in the long term scale. In addition, AQI showed an obvious positive correlation with temperature and sunshine hours in short term, and a clear negative correlation with humidity and rainfall. The research results of this paper will provide a reference for pollution prevention and control in the CCUA.

The nitrite reductase encoded by nirBDs in Pseudomonas putida Y-9 influences ammonium transformation.

It is unknown whether nirBDs, which conventionally encode an NADH nitrite reductase, play other novel roles in nitrogen cycling. In this study, we explored the role of nirBDs in the nitrogen cycling of Pseudomonas putida Y-9. nirBDs had no effect on organic nitrogen transformation by strain Y-9. The △nirBD strain exhibited higher ammonium removal efficiency (90.7%) than the wild-type strain (76.1%; P < 0.05) and lower end gaseous nitrogen (N2O) production. Moreover, the expression of glnA (control of the ammonium assimilation) in the △nirBD strain was higher than that in the wild-type strain (P < 0.05) after being cultured in ammonium-containing medium. Furthermore, nitrite noticeably inhibited the ammonium elimination of the wild-type strain, with a corresponding removal rate decreasing to 44.8%. However, no similar impact on ammonium transformation was observed for the △nirBD strain, with removal efficiency reaching 97.5%. In conclusion, nirBDs in strain Y-9 decreased the ammonium assimilation and increased the ammonium oxidation to nitrous oxide.

Crops' response to the emergent air pollutants.

MAIN CONCLUSION: Consequences of air pollutants on physiology, biology, yield and quality in the crops are evident. Crop and soil management can play significant roles in attenuating the impacts of air pollutants. With rapid urbanization and industrialization, air pollution has emerged as a serious threat to quality crop production. Assessing the effect of the elevated level of pollutants on the performance of the crops is crucial. Compared to the soil and water pollutants, the air pollutants spread more rapidly to the extensive area. This paper has reviewed and highlighted the major findings of the previous research works on the morphological, physiological and biochemical changes in some important crops and fruits exposed to the increasing levels of air pollutants. The crop, soil and environmental factors governing the effect of air pollutants have been discussed. The majority of the observations suggest that the air pollutants alter the physiology and biochemical in the plants, i.e., while some pollutants are beneficial to the growth and yields and modify physiological and morphological processes, most of them appeared to be detrimental to the crop yields and their quality. A better understanding of the mechanisms of the uptake of air pollutants and crop responses is quite important for devising the measures ‒ at both policy and program levels ‒ to minimize their possible negative impacts on crops. Further research directions in this field have also been presented.

Variabilities in autumn cyanobacterial responses to ecosystem external enrichments based on nutrient addition bioassay in Pengxi River, Three Gorges Reservoir, China.

Nutrient availability, is a crucial anthropogenic stressor promoting freshwater eutrophication and rapid expansion of harmful algal blooms (HABs), deteriorating water quality and threatening public health worldwide. The estimation of the HABs community responses to diel changes in the nutrients while characterizing the ecosystem growth limiting factors, is key to prudent watershed management. The present study investigated the short-term variabilities in autumn cyanobacterial responses to the external nutrient inputs into the Pengxi River using the nutrient addition bioassay approach. Results reveal phytoplankton community structure dominated by the cyanobacteria: Anabaena and Aphanizomenon spp. (relative abundance = 46.20% equilibrium abundance), followed by the diatoms, out of which Lindayia bodaniica, are preponderant. Nutrient enrichment triggered strong variabilities in dominance and successions among the cyanobacterial group, with maximum dominance (76.34%) exhibited by the Aphanizomenon sp. upon NH4 addition. Fe enrichment led to the succession of cyanobacteria, Leptolyngbya tenuis, which was below the detectable limit in the control, indicating the role of Fe in its proliferation. Studies on nutrient limitation demonstrated P/NH4 co-limited ecosystem, with P as the primary and NH4, a secondary limiting factor. The nitrate preference index (NO3-RPI = 0.991) shows a high preference for NH4 while NO3 constitutes the bulk of the ecosystem TN. Considering the elevated NO3 concentration, we posit that a shift in the phytoplankton community structure from cyanobacteria to diatoms dominated ecosystem, is expected following Fe depletion and a further stretch on the current ecosystem NH4 limitation. The study provides useful and first-ever insights for nutrient reduction in the middle Three Gorges Reservoir (TGR) before the onset of the heavy HABs during spring in the Pengxi River.

Bioaugmentation as a green technology for hydrocarbon pollution remediation. Problems and prospects.

Environmental pollution mitigation measure involving bioremediation technology is a sustainable intervention for a greener ecosystem biorecovery, especially the obnoxious hydrocarbons, xenobiotics, and other environmental pollutants induced by anthropogenic stressors. Several successful case studies have provided evidence to this paradigm including the putative adoption that the technology is eco-friendly, cost-effective, and shows a high tendency for total contaminants mineralization into innocuous bye-products. The present review reports advances in bioremediation, types, and strategies conventionally adopted in contaminant clean-up. It identified that natural attenuation and biostimulation are faced with notable limitations including the poor remedial outcome under the natural attenuation system and the residual contamination occasion following a biostimulation operation. It remarks that the use of genetically engineered microorganisms shows a potentially promising insight as a prudent remedial approach but is currently challenged by few ethical restrictions and the rural unavailability of the technology. It underscores that bioaugmentation, particularly the use of high cell density assemblages referred to as microbial consortia possess promising remedial prospects thus offers a more sustainable environmental security. The authors, therefore, recommend bioaugmentation for large scale contaminated sites in regions where environmental degradation is commonplace.

Certain Environmental Conditions Maximize Ammonium Accumulation and Minimize Nitrogen Loss During Nitrate Reduction Process by Pseudomonas putida Y-9.

Realizing the smallest nitrogen loss is a challenge in the nitrate reduction process. Dissimilatory nitrate reduction to ammonium (DNRA) and nitrate assimilation play crucial roles in nitrogen retention. In this study, the effects of the carbon source, C/N ratio, pH, and dissolved oxygen on the multiple nitrate reduction pathways conducted by Pseudomonas putida Y-9 are explored. Strain Y-9 efficiently removed nitrate (up to 89.79%) with glucose as the sole carbon source, and the nitrogen loss in this system was 15.43%. The total nitrogen decrease and ammonium accumulation at a C/N ratio of 9 were lower than that at 12 and higher than that at 15, respectively (P < 0.05). Besides, neutral and alkaline conditions (pH 7-9) favored nitrate reduction. Largest nitrate removal (81.78%) and minimum nitrogen loss (10.63%) were observed at pH 7. The nitrate removal and ammonium production efficiencies of strain Y-9 increased due to an increased shaking speed. The expression patterns of nirBD (the gene that controls nitrate assimilation and DNRA) in strain Y-9 were similar to ammonium patterns of the tested incubation conditions. In summary, the following conditions facilitated nitrate assimilation and DNRA by strain Y-9, while reducing the denitrification: glucose as the carbon source, a C/N ratio of 9, a pH of 7, and a shaking speed of 150 rpm. Under these conditions, nitrate removal was substantial, and nitrogen loss from the system was minimal.

Rhizosphere Microbial Communities Are Significantly Affected by Optimized Phosphorus Management in a Slope Farming System.

Soil rhizosphere microorganisms play crucial roles in promoting plant nutrient absorption and maintaining soil health. However, the effects of different phosphorus (P) managements on soil microbial communities in a slope farming system are poorly understood. Here, rhizosphere microbial communities under two P fertilization levels-conventional (125 kg P2O5 ha-1, P125) and optimal (90 kg P2O5 ha-1, P90)-were compared at four growth stages of maize in a typical sloped farming system. The richness and diversity of rhizosphere bacterial communities showed significant dynamic changes throughout the growth period of maize, while different results were observed in fungal communities. However, both the P fertilization levels and the growth stages influenced the structure and composition of the maize rhizosphere microbiota. Notably, compared to P125, Pseudomonas, Conexibacter, Mycobacterium, Acidothermus, Glomeromycota, and Talaromyces were significantly enriched in the different growth stages of maize under P90, while the relative abundance of Fusarium was significantly decreased during maize harvest. Soil total nitrogen (TN) and pH are the first environmental drivers of change in bacterial and fungal community structures, respectively. The abundance of Gemmatimonadota, Proteobacteria, and Cyanobacteria showed significant correlations with soil TN, while that of Basidiomycota and Mortierellomycota was significantly related to pH. Additionally, P90 strengthened the connection between bacteria, but reduced the links between fungi at the genus level. Our work helps in understanding the role of P fertilization levels in shaping the rhizosphere microbiota and may manipulate beneficial microorganisms for better P use efficiency.

A Bibliometric Analysis on Nonpoint Source Pollution: Current Status, Development, and Future.

Nonpoint source pollution (NPS) has become the leading factor of global water quality problems, attracting great attention from governments and researchers in various countries. Based on this situation, understanding the current research status of NPS can help guide future research. However, most of the current reviews only describe the research status of some specific aspects but fail to quantify the research hotspots and development trends on the whole, which limits the overall understanding of NPS. In this paper, bibliometrics was used to study the current status, hotspots, and frontiers of NPS research during 1991-2015, and the future research development was predicted. Over the past 15 years, there has been a remarkable growth trend in publication output, and the participation of countries/territories has also increased. Journal of Environmental Quality, Journal of Hydrology, and Total Environmental Science were the top three journals. Sharpley AN and Arnold JG from the USA were the most productive authors with the best quality articles. The major author clusters and research regions are located in North America and Europe, followed by East Asia. The United States dominates this research field, with the largest number of independent and collaborative articles. Chinese authors gained more attention through international cooperation. Keyword analysis confirmed that water quality and nutrients were the main concerns of NPS pollution research, which mainly involved a number of research topics, such as pollutant emission reduction research and the evaluation and simulation of pollutants' migration and their transformation under different situations, while pesticides were less of a concern, which suggests that the abuse of pesticides has come under control. Meanwhile, SWAT was the dominating model in the last decade partly because it satisfied the growing needs of watershed-scale management.

Low C/N Ratios Promote Dissimilatory Nitrite Reduction to Ammonium in Pseudomonas putida Y-9 under Aerobic Conditions.

The biogeochemical consequences of denitrification and dissimilatory nitrate reduction to ammonium (DNRA) have a significant influence on nitrogen (N) cycling in the ecosystem. Many researchers have explored these two pathways in soil and sediment ecosystems under anaerobic conditions. However, limited information is available regarding the influence of external environmental conditions on these two pathways in a well-defined experimental system under aerobic conditions. In this study, the impacts of the external environmental factors (carbon source, C/N ratio, pH, and dissolved oxygen) on nitrite reduction through the denitrification and DNRA routes in Pseudomonas putida Y-9 were studied. Results found that sodium citrate and sodium acetate favored denitrification and DNRA, respectively. Furthermore, neutral pH and aerobic conditions both facilitated DNRA and denitrification. Especially, low C/N ratios motivated the DNRA while high C/N ratios stimulated the denitrification, which was opposite to the observed phenomena under anaerobic conditions.

Funneliformis mosseae Improves Growth and Nutrient Accumulation in Wheat by Facilitating Soil Nutrient Uptake under Elevated CO2 at Daytime, Not Nighttime.

The concurrent effect of elevated CO2 (eCO2) concentrations and arbuscular mycorrhizal fungi (AMF) on plant growth, carbon (C), nitrogen (N), phosphorus (P) and potassium (K) accumulations in plant and soil is largely unknown. To understand the mechanisms of eCO2 and mycorrhization on wheat (Triticum aestivum) performance and soil fertility, wheat seedlings were grown under four different CO2 environments for 12 weeks, including (1) ambient CO2 (ACO2, 410/460 ppm, daytime/nighttime), (2) sole daytime eCO2 (DeCO2, 550/460 ppm), (3) sole nighttime eCO2 (NeCO2, 410/610 ppm), and (4) dual or continuous daytime/nighttime eCO2 ((D + N)eCO2, 550/610 ppm), and with or without AMF (Funneliformis mosseae) colonization. DeCO2, NeCO2 and (D + N)eCO2 generally significantly increased shoot and root biomass, plant C, N, P and K accumulation, soil invertase and urease activity, but decreased shoot and root N, P and K concentrations, and soil available N, P and K. Compared with non-AMF, AMF effects on above-mentioned characteristics were significantly positive under ACO2, DeCO2 and (D + N)eCO2, but negative on plant biomass, C, N, P and K accumulation under NeCO2. Overall, AMF colonization alleviated soil nutrient constraints on plant responses to DeCO2, while NeCO2 decreased AMF's beneficial effects on plants. These results demonstrated that an integration of AMF's benefits to plants under factual field DeCO2 and/or NeCO2 will be critical for managing the long-term consequence of future CO2 rising on global cropping systems.

Blue-light emitting aminated pectin for detecting Cu2+ ion.

This research studied the chemo-sensing of low-cost aminated pectin (PE) obtained by a facile calcination under ammonia gas at temperature no higher than 175 °C without excessive use of alkaline, acid or solvents. The ammonia gas was found to replace the hydroxyl and methoxyl group, enhancing the crystallinity and solubility of the resultant pectin than those calcined in air or in 5% H2. Though the increase of light absorption could be attributed mainly to the dehydration during calcination which caused the formation of CC double bond or aromatic ring, the N incorporation could be important to the photoluminescence (PL) emission. The PL quenching of the blue fluorescent aminated pectin showed a good linearity with the concentration of Cu2+, Fe3+ and the highest sensitivity toward Cu2+ among the investigated metal ions. In order to further increase the PL quenching toward Cu2+ and decrease the interference of Fe3+, a method involving H2O2 and ultraviolet illumination was developed to catalyze the oxidation of fluorophores on the polymer. This work provides new horizon on the modification and application of pectin in chemosensing.

Potential Ecological Risk of Heavy Metals in a Typical Tributary of the Three Gorges Reservoir.

Water and sediment samples were collected from a tributary (Ruxi River) of the Three Gorges Reservoir (TGR) to analyze the concentrations of seven heavy metals (HMs) and their fractions for better understanding the migration, bioavailability and potential environmental risk of HMs. The results indicated that the concentrations of HMs in water were lower than the Environmental Quality Standards for Surface Water Class I standards, except for Ni. Cd in sediment was found to be more sensitive to environmental changes, as the acid-soluble fraction of Cd accounted for about 40% of total Cd, and the sediment-water partition coefficient of Cd was the smallest among all the HMs. Meanwhile, multiple risk assessment methods of HMs indicated that sediment Cd in most sampling sites, significantly influenced by human activities, exhibited heavy pollution, suggesting that the Cd pollution should be attached great importance in the Ruxi River.

[Spatial Distribution and Risk Assessment of Heavy Metals in Sediments of the Ruxi Tributary of the Three Gorges Reservoir].

Sediment column and soil samples collected from 12 sampling sites in four regions of the Ruxi River, a typical tributary of the Three Gorges Reservoir, were analyzed for eight selected heavy metals including Cr, Ni, Cu, Mn, Zn, Cd, Pb, and Hg to evaluate their spatial and vertical distribution, source, and biological toxic effects. The results showed that the average concentrations of heavy metals were (79.60±11.87), (41.340±4.999), (32.69±8.70), (823.34±125.76), (122.11±22.82), (0.393±0.140), and (29.122±6.811) mg·kg-1 for Cr, Ni, Cu, Mn, Zn, Cd, and Pb, respectively, and (74.84±39.50) µg·kg-1 for Hg, all of which exceeded the sediment background values of the Yangtze River. A spatial trend of decreasing metal concentrations was observed from the reach influenced by the human activities of Ruxi town to the backwater zone and then to the natural river reach. Moreover, in the backwater zone, the heavy metals in sediments and soil along the river were significantly lower than those in sediments, indicating that the sediments and soil were not one primary source for these metals in backwater zone sediment. From the vertical distribution of sediment, in addition to Pb, the highest level of metals was observed at 8 cm in the reach influenced by human activities, and their concentrations decreased with sediment depth in the backwater zone and natural river beach. Significant correlation was found between all the heavy metals (P<0.01, except Ni), indicating a potential homology of these metals in the Ruxi River. Evaluation results of the geoaccumulation index reveal that there exists light to partial moderate Cd and Zn pollution in the Ruxi River. The evaluation of biotoxicity effects showed that Ni was likely to have toxic effects on organisms with a probability of 10% to 75%, and Cd, Zn, Hg, Cu, Pb, and Cr are likely to have biotoxic effects at<10% probability. The combined effect values of multiple metals indicated that the risk of adverse effects was between low and lower medium in the sediments of the Ruxi River.

Nitrate assimilation, dissimilatory nitrate reduction to ammonium, and denitrification coexist in Pseudomonas putida Y-9 under aerobic conditions.

The specific nitrate reduction pathway in Pseudomonas putida Y-9 under aerobic conditions was studied. Strain Y-9 removed 82% of the nitrate accompanied by an accumulation of ammonium and a decrease of total nitrogen. Ammonium inhibited nitrate transformation (removal efficiency was 22.65%), illustrating that nitrate assimilation exists in strain Y-9. The detectable ammonium in the supernatant during the nitrate reduction process came from intracellular locations in strain Y-9. The nirBD that encodes nitrite reductase had an important role in strain growth and ammonium production. A 15N isotope experiment demonstrated that strain Y-9 can conduct dissimilatory nitrate reduction to ammonium (DNRA) and nirBD controls this process. This further indicated that the loss of total nitrogen is due to denitrification. All results highlighted that strain Y-9 performs simultaneous nitrate assimilation, DNRA, and denitrification under aerobic conditions, and nirBD controls the assimilation and DNRA process. Thereinto, nitrate assimilation dominates the removal of nitrate.

Mechanized and Optimized Configuration Pattern of Crop-Mulberry Systems for Controlling Agricultural, Non-Point Source Pollution on Sloping Farmland in the Three Gorges Reservoir Area, China.

High-intensity utilization of sloping farmland causes serious soil erosion and agricultural, non-point source pollution (AGNSP) in the Three Gorges Reservoir Area (TGRA). Crop-mulberry systems are important agroforestry systems for controlling soil, water, and nutrient losses. However, there are many different mulberry hedgerow planting patterns in the TGRA. In this study, soil structure, nutrient buildup, and runoff nutrient loss were observed in field runoff plots with five configurations: P1 (two longitudinal mulberry hedgerows), P2 (two mulberry contour hedgerows), P3 (three mulberry contour hedgerows), P4 (mulberry hedgerow border), and P5 (mulberry hedgerow border and one mulberry contour hedgerow), as well as a control (CT; no mulberry hedgerows). P1 had the smallest percentage of aggregate destruction (18.8%) and largest mean weight diameter (4.48 mm). P5 led to the greatest accumulation of ammonium nitrogen (NH4+-N) and total phosphorus (TP) (13.4 kg ha-1 and 1444.5 kg ha-1 on average, respectively), while P4 led to the greatest accumulation of available phosphorus (AP), nitrate nitrogen (NO3--N), and total nitrogen (TN) (114.0, 14.9, and 1694.1 kg ha-1, respectively). P5 was best at preventing soil erosion, with the smallest average annual runoff and sediment loss of 112.2 m3 ha-1 and 0.06 t ha-1, respectively, which were over 72.4% and 87.4% lower than those in CT, respectively. P5 and P4 intercepted the most N in runoff, with average NH4+-N, NO3--N, particulate N, and TN losses of approximately 0.09, 0.07, 0.41, and 0.58 kg ha-1, respectively, which were 49.7%, 76.2%, 71.3%, and 69.9% lower than those in CT, respectively. P5 intercepted the most P in runoff, with average TP and total dissolved phosphorus (TDP) losses of 0.09 and 0.04 kg ha-1, respectively, which were 77.5% and 70.4% lower than those in CT, respectively. Therefore, the pattern with one mulberry hedgerow border and one mulberry contour hedgerow (P5) best controlled AGNSP, followed by that with only a mulberry hedgerow border (P4).

Nitrous oxide produced directly from ammonium, nitrate and nitrite during nitrification and denitrification.

A hypothermia aerobic denitrifying bacterium, Pseudomonas taiwanensis strain J488, can effectively remove multiple nitrogen sources from wastewater at 15 °C. The ammonium, nitrate and nitrite removal efficiencies were 100 %, 92.61 % and 92.49 %, respectively. Strain J488 could survive with hydroxylamine as sole nitrogen source and its removal efficiency was 97.71 %. The removal efficiency of ammonium was 100 % even in the presence of the classical inhibitors of nitrification allylthiourea and diethyldithiocarbamate. These findings fundamentally changed the picture that the ammonia monooxygenase could be inhibited by the copper chelators of allylthiourea or diethyldithiocarbamate. Similarly, the nitrite removal capacity of strain J488 was not sensitive to inhibition by Pb2+, and its removal efficiency was also 100 %. Additionally, by identifying the intermediates accumulation of nitrification and denitrification, using nitrification and denitrification inhibitors, measuring enzyme activities and determining N2O concentrations, it was demonstrated that N2O could be produced directly from ammonium, nitrate and nitrite.