Impacts of O2:CH4 ratios and CH4 concentrations on the denitrification and CH4 oxidations of a novel AME-AD system.

Aerobic methane (CH4) oxidation coupled to denitrification (AME-D) is a promising process for the denitrification of low C/N wastewater. Compared with anaerobic denitrifying bacteria, aerobic denitrifying bacteria may enable AME-D have high denitrification ability under aerobic conditions. This study constructed a novel aerobic methane oxidation coupled to aerobic denitrification (AME-AD) system using the typical aerobic denitrifying bacteria Paracoccus pantotrophus ATCC35512 and the typical aerobic methane oxidizing bacteria Methylosinus trichosporium OB3b. The denitrification and CH4 oxidations of AME-AD with different O2:CH4 ratios (0:1, 0.25:1, 0.5:1, 0.75:1, 1:1 and 1.25:1) and CH4 concentrations (0, 14000, 28000, 42000, 56000 and 70000 mg m-3) were investigated in batch experiments. Higher O2:CH4 ratios can significantly improve the denitrification and CH4 oxidations of the AME-AD (P < 0.05). The treatment with an O2:CH4 ratio of 1.25:1 had the highest denitrification rate (0.036 mg h-1) and highest CH4 oxidation rate (0.20 mg h-1). The CH4 concentration in the headspace was positively correlated with the AME-AD denitrification rate. The calculated CH4/NO3-(mol/mol) in most treatments ranged from 5.76 to 6.84. In addition, excessively high O2 and CH4 concentrations can lead to increased nitrous oxide (N2O) production in AME-AD. The N2O production rate was up to 1.00 µg h-1 when the O2:CH4 was 1.25:1. These results can provide data support for the application of AME-AD for low-C/N wastewater treatment and greenhouse gas emission reduction.

Separation efficiency of different solid-liquid separation technologies for slurry and gas emissions of liquid and solid fractions: A meta-analysis.

Solid-liquid separation (SLS) technology is widely used in the slurry management in animal farms. This study conducted a comprehensive meta-analysis of 45 published articles to evaluate the differences in separation efficiencies (SEX-SF) of various SLSs and the changes of gas emissions before and after the separation during on-farm slurry storage. The results indicated that the SEX-SF of the untreated raw slurry and acidified slurry were consistently greater than those of the digested slurry, and centrifugation resulted in greater SEX-SF than the other mechanical methods. Both measured and simulated data showed that the centrifuge technology had greater reductions in greenhouse gas (GHG) emissions relative to the screw press (56.1-58.0% vs. 38.9-40.2% for untreated slurry, and 29.7-30.2% vs. 22.5-23.2% for digested slurry), mainly due to CH4 reduction. Additionally, we identify the need for further assessment of the environmental risks that are associated with SLSs for the development of an optimal slurry management chain.

Impacts of slurry application methods and inhibitors on gaseous emissions and N2O pathways in meadow-cinnamon soil.

This study aimed to evaluate the impact of mitigation practices (slurry application methods and inhibitors applications) on gas emissions and identify the soil N2O production pathways in cattle slurry applied soil using isotopocule mapping approach. First, we compared the NH3 and N2O emissions of cattle slurry applied soil in a summer maize field experiment in north China plain (NCP) with four treatments: control (CK, no fertilization), slurry application using surface (SA-S), slurry application using band application (BA-S), and chemical fertilizer application using band application (BA-C). Then, an incubation experiment was conducted to investigate the mitigation effect of nitrification inhibitors (dicyandiamide, DCD) and denitrification inhibitors (procyanidins, PC) and their combination (DCD + PC) on gaseous N emissions with slurry applied using incorporation (IA) or surface application (SA) methods. The results showed that the total gaseous N emissions (N2O-N and NH3-N) in field were in the order of SA-S (1534 mg m-2) > BA-S (338 mg m-2) > BA-C (128 mg m-2) > CK (55 mg m-2), and the dominant N loss contributor varied from NH3 in SA-S (∼89%) to N2O in BA-S (∼94%) and BA-C (∼88%). Moreover, the isotopocule mapping approach indicated that emitted N2O of the slurry applied soil in field appeared to have lower rN2O values and led to more N2O + N2 emissions at the initial fertilization period. The incubation experiment indicated that the N2O emissions of slurry-applied soil were significantly reduced by DCD (∼45%) and DCD + PC (∼67%) application in comparison with CK (p < 0.05), and the stronger contributions of bacterial denitrification/nitrifier denitrification to N2O production were revealed by the lower δ15NSP in N2O using the isotopocule mapping approach. In conclusion, in NCP the gaseous losses of the slurry applied field can be largely reduced by using incorporation method, and greater reduction could be achieved given the simultaneous application of nitrification/denitrification inhibitors.

Purification efficiency of zeolite and two planted grasses on sewage and relationship with carbon-nitrogen-phosphorus ratios in simulated constructed wetland system.

For achieving the economical and efficient configuration of constructed wetlands (CWs), a simulated device of vertical flow CWs was used to investigate the effects of different volume ratios of substrates to two cold-resistant plants on pollutant concentrations as well as their ratios in effluent under different inflow domestic sewage concentrations. The average removal rates (ARRs) of ammonia nitrogen, total nitrogen (TN) and total phosphorus were 82.7%, 84.9% and 80.6% respectively in the treatments with zeolite but no plants, which increased by 22.6%, 20.8% and 14.9% compared with those without zeolite and plants. However, in the treatments with zeolite and planted grasses, the ARRs of the three pollutants were over 90%, and those of chemical oxygen demand were lower. The removal rates of ammonia nitrogen, TN and total phosphorus had negative correlations with C:N and N:P ratios and positive correlations with the C:P ratios. Increasing the ratio of zeolite to soil from 1:1 to 2:1 had no significant effects in the removal efficiency. It was suggested that planting Lolium perenne or Poa annua on the substrate with a zeolite to soil volume ratio of 1:1 could be considered as the optimum combination to purify the domestic sewage in north rural areas of China.

[Effects of Controlled-release Blended Fertilizer on Crop Yield and Greenhouse Gas Emissions in Wheat-maize Rotation System].

The increasing use of nitrogen fertilizers exerts extreme pressure on the environment (e.g., greenhouse gas emissions, GHGs) for winter wheat-summer maize rotation systems in the North China Plain. The application of controlled-release fertilizers is considered as an effective measure to improve crop yield and nitrogen fertilizer utilization efficiency. To explore the impact of one-time fertilization of controlled-release blended fertilizer on crop yield and GHGs of a wheat-maize rotation system, field experiments were carried out in Dezhou Modern Agricultural Science and Technology Park from 2020 to 2022. Five treatments were established for both winter wheat and summer maize, including no nitrogen control (CK), farmers' conventional nitrogen application (FFP), optimized nitrogen application (OPT), CRU1 (the blending ratio of coated urea and traditional urea on winter wheat and summer maize was 5:5 and 3:7, respectively), and CRU2 (the blending ratio of coated urea and traditional urea on winter wheat and summer maize was 7:3 and 5:5, respectively). The differences in yield, nitrogen fertilizer utilization efficiency, fertilization economic benefits, and GHGs among different treatments were compared and analyzed. The results showed that nitrogen application significantly increased the single season and annual crop yields of the wheat-maize rotation system (P < 0.05). Compared with those of FFP, the CRU1 and CRU2 treatments increased the yields of summer maize by 0.4% to 5.6%, winter wheat by -5.4% to 4.1%, and annual yields by -1.1% to 3.9% (P > 0.05). N recovery efficiency (NRE), N agronomic efficiency (NAE), and N partial factor productivity (NPFP) were increased by -8.6%-43.4%, 2.05-6.24 kg·kg-1, and 4.24-10.13 kg·kg-1, respectively. Annual net income increased by 0.2% to 6.3%. Nitrogen application significantly increased the annual emissions of soil N2O and CO2 in the rotation system (P < 0.05) but had no effect on the annual emissions of CH4 (except for in the FFP treatment in the first year). The annual total N2O emissions under the CRU1 and CRU2 treatments were significantly reduced by 23.4% to 30.2% compared to those under the FFP treatment (P < 0.05). Additionally, nitrogen application significantly increased the annual global warming potential (GWP) of the rotation system (P < 0.05), but the intensity of greenhouse gas emissions was reduced due to the increase in crop yields. Compared with that under FFP, the annual GWP under the CRU1 and CRU2 treatments decreased by 9.6% to 11.5% (P < 0.05), and the annual GHGs decreased by 11.2% to 13.8% (P > 0.05). In summary, the one-time application of controlled-release blended fertilizer had a positive role in improving crop yield and economic benefits, reducing nitrogen fertilizer input and labor costs, and GHGs, which is an effective nitrogen fertilizer management measure to promote cleaner production of food crops in the North China Plain.

Laws Governing Nitrogen Loss and Its Numerical Simulation in the Sloping Farmland of the Miyun Reservoir.

Surface flow (SF) and subsurface flow (SSF) are important hydrological processes occurring on slopes, and are driven by two main factors: rainfall intensity and slope gradient. To explore nitrogen (N) migration and loss from sloping farmland in the Miyun Reservoir, the characteristics of total nitrogen (TN) migration and loss via SF and SSF under different rainfall intensities (30, 40, 50, 60, 70, and 80 mm/h) and slope gradients (5°, 10°, and 15°) were studied using indoor stimulated rainfall tests and mathematical models. Nitrogen loss via SF and SSF was found to increase exponentially and linearly with time, respectively, with SSF showing 14-78 times higher loss than SF. Under different rainfall intensities, SSF generally had larger TN loss loading than SF, thereby indicating that SSF was the main route for TN loss. However, the TN loss loading proportion via SF increasing from 14.03% to 35.82% with increasing rainfall intensity is noteworthy. Furthermore, compared with the measurement data, the precision evaluation index Nash-Suttcliffe efficient (NSE) and the determination coefficient (R2) of the effective mixing depth model in the numerical simulation of TN loss through SF in the sloping farmland in the Miyun Reservoir were 0.74 and 0.831, respectively, whereas those of the convection-dispersion equation for SSF were 0.81 and 0.811, respectively, thus indicating good simulation results. Therefore, this paper provides a reference for studying the mechanism of N migration and loss in sloping farmland in the Miyun Reservoir.

[Effect of single basal application of controlled-release blended fertilizer on reactive nitrogen loss, carbon and nitrogen footprint during summer maize growth period]. / 基施控释掺混肥对夏玉米生长期活性氮损失和碳氮足迹的影响.

To elucidate the agronomic and environmental effects of single basal application of controlled-release blended fertilizer in summer maize, and optimize management measures of nitrogen fertilizer for grain production in North China Plain, we conducted a field experiment in Dezhou Modern Agricultural Science and Technology Park in Shandong Province. There were four treatments: CK (no N fertilizer), FFP (farmer's fertilizing practice, 240 kg N·hm-2), OPT (optimized nitrogen application, 210 kg N·hm-2), and CRBF (controlled-release blended fertilizer with single basal application, 210 kg N·hm-2). We compared maize yield and reactive nitrogen loss, and quantitatively evaluated the carbon and nitrogen footprints by using life cycle assessment method. The results showed that nitrogen application significantly increased summer maize yield. Compared with FFP, OPT and CRBF increased summer corn yield by 0.7% and 2.9%, respectively, decreased the total amount of ammonia volatilization, N2O emission, and nitrate leaching by 13.0% and 72.7%, 13.3% and 37.5%, 20.5% and 23.5% respectively. Compared with CK, nitrogen application significantly increased the global warming potential (GWP) of summer maize production. Compared with FFP, GWP and greenhouse gas emission intensity of OPT decreased by 3.8% and 4.2%, while the reduction of CRBF were 8.7% and 12.0%, respectively. Compared with CK, nitrogen application significantly increased the carbon and nitrogen footprint of summer maize production. The production and transportation of nitrogen fertilizer and soil greenhouse gas emission were the main contributing factors of the carbon footprint, with contribution rates of 54%-60% and 24%-31%, respectively. Nitrate leaching was the main contributing factor of nitrogen footprint, with contribution rate of 57%-94%. Compared with FFP, the carbon and nitrogen footprints of OPT and CRBF were reduced by 11.0% and 16.5%, 19.6% and 28.4%, respectively. Considering the yield, reactive nitrogen loss and carbon and nitrogen footprint, we recommended the single basal application of controlled-release blended fertilizer as an effective nitrogen fertilizer management measure to promote grain clean production in the North China Plain.

Biodegradation of Dibutyl Phthalate by the New Strain Acinetobacter baumannii DP-2.

Optimizing the culture conditions of DBP degradation by bacteria and investigating its biodegradation pathways have a great importance to develop effective PAEs pollution control strategies. In this study, we investigated the cultivation condition optimization, degradation kinetics, and degradation pathways of a newly isolated dibutyl phthalate (DBP) degradation strain, which was isolated from activated sludge and identified as Acinetobacter baumannii DP-2 via morphological observation, biochemical identification, and 16S rDNA sequence analysis. The degradation conditions were optimized based on the results of single-factor experiments and response surface optimization experiments. The DBP degradation rate of Acinetobacter baumannii DP-2 reached up to 85.86% when the inoculation amount was 17.14%, the DBP concentration was 9.81 mg·L-1 and the NaCl concentration was 5 g·L-1. The GC-MS analysis results indicated that the intermediate metabolites of Acinetobacter baumannii DP-2 mainly consisted of DMP, MBP, PA, and benzoic acid derivatives, which confirmed the degradation pathway from DBP to PA under aerobic pathway and then to BA under anaerobic pathway. In summary, Acinetobacter baumannii DP-2 shows great potential for the degradation of DBP in contaminated soils.

Mitigating gas emissions from poultry litter composting with waste vinegar residue.

The composting process is important in the recycling of organic wastes produced in agriculture, food, and municipal waste management. This study explored the suitability of using waste vinegar residue (WVR) as an amendment in poultry litter (PL) composting. Four treatments, including poultry litter (CK), poultry litter+vinegar residue (VR), poultry litter+vinegar residue+lime (VR_Ca) and poultry litter+vinegar residue+biochar (VR_B), were conducted. During a 42-day composting period, the dynamics of carbon dioxide (CO2), ammonia (NH3), nitrous oxide (N2O) and methane (CH4) emissions, as well as the physicochemical properties and abundances of the bacteria and fungi of the feedstock were tracked to examine the potential barriers in the co-composting of WVR and PL. Compared to those of the CK, using a WVR amendment lowered the pH, increased the electrical conductivity significantly at the early stage, resulted in a strong inhibition of bacterial and fungal growth and delayed the thermophilic period of poultry litter composting while significantly reducing NH3 and N2O and GHG (CO2-e) emissions. A preadjustment of the WVR with alkaline biochar or lime lengthened the thermophilic period and increased the germination index (GI) by alleviating the inhibitory effect of the WVR on bacterial and fungal growth during composting. However, such preadjustment might reduce the mitigation effect on NH3. In conclusion, WVR can be recycled through co-composting with poultry litter, and the additional mitigation of N losses and N conservation can be achieved without halting compost quality.

Effects of Different Hedgerow Patterns on the Soil Physicochemical Properties, Erodibility, and Fractal Characteristics of Slope Farmland in the Miyun Reservoir Area.

Soil erosion of sloping farmland in the Miyun reservoir area in Beijing has become a serious issue and has threatened the ecological environment and safety of the reservoir area. We used the Taishizhuang Village Non-point Source Pollution Prevention & Control Base in the Miyun reservoir as a study area and performed a comparative analysis of the physicochemical properties of soil of the upper, middle, and lower slopes of the Scutellaria baicalensis + Buchloe dactyloides plot (Treatment 1, T1), Morus alba + Buchloe dactyloides plot (Treatment 2, T2), Salvia miltiorrhiza + Cynodon dactylon plot (Treatment 3, T3), Platycodon grandiflorus + Cynodon dactylon plot (T4), and a barren land control plot (Control check, CK), to explore how different hedgerow patterns affect the soil's physicochemical properties, anti-erodibility, and fractal characteristics. We found the following: (1) The primary soil mechanical composition included sand particles in the upper slopes, whereas it was soil fine particles in the middle and lower slopes. (2) The fractal dimension of the slope soil showed a significant negative correlation with sand particles (R2 = 0.9791) while being positively correlated with silt particles (R2 = 0.9635) and clay particles (R2 = 0.9408). (3) All hedgerow patterns increased soil nutrients, with the Morus alba + Buchloe dactyloides hedgerow plot increasing the soil total nitrogen (STN), soil total phosphorus (STP), and soil organic matter (SOM) content by 213.89−282.69%, 55.56−58.15%, and 29.77−56.04%, respectively. (4) The Morus alba + Buchloe dactyloides hedgerow plot significantly decreased the soil erodibility factor K value, improved soil anti-erodibility, and reduced soil erosion. (5) The K value of the soil erodibility was significantly negatively correlated with clay particles, soil fractal dimension, and STP (p < 0.01); positively correlated with sand particles; and negatively correlated with silt particles, STN, and SOM. Therefore, the Morus alba + Buchloe dactyloides hedgerow planting contributes to clay particle conservation, soil nutrient content improvement, soil structure optimization, and soil anti-erodibility enhancement.

A correlation study between nursing staff's knowledge level of hospice care and the psychology, emotion and attitude towards deaths.

OBJECTIVE: We investigated the relationship between nursing staff's knowledge of hospice care and psychological states, including grief and attitude towards death. METHODS: From October 2018 to December 2018, a total of 1900 professional nursing staff of secondary and tertiary levels in Qinghai Province were chosen as the research subjects. Professional questionnaires were used to evaluate their knowledge level of Hospice Care (HC), psychological states, grief and attitude towards death, while the correlation between HC knowledge level and the latter three were analyzed. RESULTS: In Qinghai Province, the nursing staff had the highest scores in terms of knowledge levels of HC symptom control with a score of 4.48±1.65, and the lowest score of 1.79±1.12 in terms of knowledge levels of death education. In the Death Attitude Profile-Revised (DAP-R) scale, there was a negative correlation between fear of death, death avoidance, escape acceptance, and HC knowledge total score (P<0.05), while there was a positive correlation between natural acceptance and HC knowledge score (P<0.05). There was no statistical correlation between the total score of approach acceptance and HC knowledge (P>0.05). In the Grief Experience Questionnaire (GEQ) questionnaire, there were negative correlations between the total score of HC knowledge and body reaction, general grief response, seeking to explain and respond to special death forms (P<0.05). Hamilton anxiety scale (HAMA) and Hamilton depression scale (HAMD) were negatively correlated with HC knowledge scores (P<0.05). CONCLUSION: There is a correlation between nursing staff's knowledge level of hospice care and the psychological state, partial grief and attitudes towards death. The improvement of levels of nursing staff's HC knowledge plays a positive role in maintaining their healthy psychological state, alleviating their grief and helping them to actively face death.

Impact of biochar application on gas emissions from liquid pig manure storage.

Biochars have been used to reduce gas emissions from manure composting practices and to recover nutrients from wastewater because of their effective sorption capacity. However, relatively less is known about the impacts of different alkaline biochars on the gas emissions from liquid manure. Materials including two commercial biochars prepared from walnut shell (WA) and coconut shell (CC), respectively, and coal (CO) were applied (with manure/biochar ratio of 20:1 in weight) to examine their influence on NH3, CH4, and N2O emissions from liquid pig manure during a 68-d period in comparison with a control (CK, without biochars), and to investigate the evolution of the manure N mass balances and the changes in biochar properties during liquid manure storage to understand the characteristics of biochar. Compared with the CK, the application of WA, CC, and CO biochars increased the NH3 emissions by 4.00, 3.87, and 1.23 times, respectively, the absorbed N content of the biochars was markedly lower than the enhanced gaseous losses through NH3 emissions. Similarly, the total greenhouse gas (GHG) emissions from the manure with WA, CC, and CO biochar application were 6.28, 5.55, and 0.83 times greater than those observed with the CK, respectively, and were mainly attributed to the enhanced CH4 emissions. The significant contribution (5%-12%) of indirect GHG emissions from the enhanced NH3-N losses was also identified. The hypothesis for the enhanced gas emissions from liquid manure with biochar addition has been discussed in the present study; however, further investigation in the future is warranted.

Nitrogen removal performance and microbial community changes in subsurface wastewater infiltration systems (SWISs) at low temperature with different bioaugmentation strategies.

Poor nitrogen removal efficiency (mainly nitrate, NO3--N) at low temperatures strongly limits application of subsurface wastewater infiltration systems (SWISs). Seven psychrophilic strains (heterotrophic nitrifying bacteria and aerobic denitrifying bacteria) were isolated and added to SWISs to investigate the effect of embedding and direct-dosing bioaugmentation strategies on sewage treatment performance at low temperature. Both bioaugmentation strategies improved ammonium (NH4+-N) removal efficiencies, and the embedding strategy also exhibited satisfactory NO3--N and total nitrogen (TN) removal efficiencies. Pyrosequencing results of the bacterial 16S rRNA gene indicated that the embedding strategy significantly decreased the indigenous soil microbial diversity (p < .05) and altered the bacterial community structure, significantly increasing the relative abundance of Clostridia, which have good nitrate-reducing activity.

[Soil contamination and assessment of heavy metals of Xiangjiang River Basin].

The contents of heavy metals (As, Cd, Cu, Zn, Ni and Pb) in soils from Xiangjiang River Basin, Hunan Province, China, were analyzed by toxicity characteristic leaching procedure (TCLP) and Nemrow method. Results showed that the total contents of As, Cd, Cu, Zn, Ni and Pb were 4.25-549.67, 0.13-76.84, 11.49-281.69, 7.75-7234.81, 5.50-56.65 and 8.60-2084.81 mg x kg(-1), respectively, and the available contents of As, Cd, Cu, Zn, Ni and Pb extracted by TCLP were 0.02-10.97, 0.06-28.41, 0.04-72.29, 0.59-1 152.32, 0.07-10. 65 and 0.17-1 165.58 mg x kg(-1). The contents of available heavy metals extracted by TCLP correlated with total contents of heavy metals. Moreover, the pollution index Nemrow method showed that 72 samples at safety level, alert level, light pollution level, medium pollution level and heavy pollution level ratios were 60.52%, 11.33%, 5.65%, 4.22% and 18.38% separately, illustrating that pollution of heavy metals in soil samples of Xiangjiang River Basin is serious.

[Total phosphorus removal from eutrophic water in Baiyangdian Lake by Potamogeton crispus].

Taking the water, sediment, and Potamogeton crispus collected from Shihoudian, Wangjiazhai, and Xiaodian in Baiyangdian Lake area into laboratory, three simulated static systems were built to study the growth of P. crispus and its effect on the removal of total phosphorus from eutrophic water and sediment. Among the three systems, Shihoudian system had the best purification effect, with the removal efficiency of total phosphorus from water body being 87.9%, followed by Wangjiazhai system 47.4%, and Xiaodian system 76.9%. The largest total phosphorus removal efficiency per gram biomass in Shihoudian, Wangjiazhai, and Xiaodian systems was 2.2%, 0.9%, and 1.4%, and the largest total phosphorus adsorption rate of sediments was 9.1%, 7.4%, and 7.7%, respectively. The TP-t and v-t fitted equations of the three systems indicated that the total phosphorus concentration in water and the removal rate of the total phosphorus were negatively exponentially decreased with time.

[Ecological responses of Brassica juncea-alfalfa intercropping to cadmium stress].

A pot experiment was conducted to study the effects of cadmium (Cd) stress on the soil-plant system under Brassica juncea-alfalfa intercropping, and to evaluate the Cd feed safety of alfalfa. Comparing with monoculture, when the soil Cd content was in the range of 0.37-20.37 mg x kg(-1), intercropping decreased the B. juncea biomass by 0.4%-11.8% while increased the alfalfa biomass by 55.3%-70.0%. Soil available Cd was mainly determined by soil total Cd and plant species, and less affected by planting pattern. Comparing with monoculture, when the soil Cd content was in the range of 0.37-5.37 mg x kg(-1), intercropping increased the Cd content in above-ground part of B. juncea by 14.5%, but decreased the Cd content in above-ground part of alfalfa by 57.1%. The Cd contents in the above-ground parts of alfalfa under monoculture and intercropping were 0.21 and 0.09 mg x kg(-1), respectively, neither of them being over the feed safety standard (0.5 mg x kg(-1)). When the soil Cd content was in the range of 10.37-20.37 mg x kg(-1), though the Cd contents of mono-cultured and intercropped alfalfa were both over the standard, the Cd contents in the above-ground parts of alfalfa and B. juncea under intercropping were decreased by 2.8%-48.3% and 1.1%-48.6%, respectively. Under both monoculture and intercropping, the Cd transport coefficient of B. juncea was far greater than that of alfalfa.