Forecasting N2O emission and nitrogen loss from swine manure composting based on BP neural network

Mitigation of ammonia, nitrous oxide and methane emissions during solid waste composting with different additives: A meta-analysis

The surface hydrology and diffuse pollution loading is hypothesized based on the unique characteristics under different rainfall types in watersheds with a subtropical monsoon climate. This study evaluated the effects of different rainfall event intensity on surface runoff and diffuse nitrogen loss in a subtropical watershed located in the latitude range between 22.5° north and 25° north in southern China by adapting the hydrological model SWAT (Soil and Water Assessment Tool). The rainfall events were classified into four categories including light rainfall (LR), moderate rainfall (MR), intense rainfall (IR), and extreme rainfall (ER). Our results showed that the ER events had the lowest occurrences of 7 days per year, but they contributed the most to total surface runoff (54.29%) and TN losses (57.63%) in the subtropical watershed researched. Although forests and pastures had a better effect on reducing diffuse pollution, their surface runoff and nitrogen loss were still proved to be serious under ER events. As for the nitrogen loss form, water-soluble nitrogen oxides nitrogen (ON-N) loss was the dominant form of total nitrogen (TN) loss, which accounted for 90% of the total loss in the simulated watershed in the subtropical monsoon climate region. Under LR events, however, nitrate nitrogen (NO3-N) accounted for 74.54% and 55.59% of TN losses from paddy fields and dry lands, respectively. The effects of antecedent soil water content (ASW) on surface runoff and TN loss were higher under ER events. The surface runoff and TN loss in the high-ASW condition were 1.17–3.86 times and 1.34–1.76 times higher, respectively, than in the low-ASW condition. These findings highlighted the important influence of ER events on diffuse pollution and have significant implications for controlling diffuse pollution under different rainfall types. This conclusion proved that extra attention and efforts are required in handling non-point-source pollution in subtropical monsoon watersheds than the watersheds in cooler regions because the natural systems including forest and pastures are no longer effective enough in controlling surface runoff and TN loss during ER.

Effects of polyacrylamide on soil erosion and nutrient losses from substrate material in steep rocky slope stabilization projects

Seasonal freeze-thaw erosion is a form of soil erosion caused by the topographical characteristics and climatic factors of the hilly and gully loess regions. Seasonal freeze-thaw can damage the soil pores and cause its bulk density to change. The effects of thawing depth on runoff and Nitrogen and Phosphorus loss on the rainfall erosion of an artificial slope filled with loess soil were analyzed after a rainfall test that simulated the spring thaw period in China. The results showed that: (1) The maximum runoff yield was 33.35 mm at 4 cm thawing depth, and the minimum was 12.95 mm at 6 cm thawing depth. With the increase in runoff time, the slope infiltration rate had a decreasing trend. The loss rate of available and total Phosphorus increased with the increase in runoff rate. The rate of increase was fastest when the thawing depth was 4 cm. (2) The relationships between runoff rate and Nitrogen loss and Phosphorus loss rate can be explained by linear regression equations, and the loss rate increased as the runoff rate rose for all thawing depths. Within the 0–6 cm thawing depths, the loss of total phosphorus was the largest when the thawing depth was 4 cm, and the loss of available phosphorus was the smallest when the thawing depth was 6 cm. At the shallower thawing depths, the available Nitrogen loss represented a smaller proportion of the total Nitrogen loss compared to nitrate Nitrogen loss. However, there was a gradual rise in the available Nitrogen proportion in the total amount of inorganic Nitrogen as the thawing depth increased. (3) Total Phosphorus was the available Phosphorus with a quadratic function relationship with runoff energy and runoff power. Runoff energy mainly affected the total Nitrogen and available Nitrogen loss in runoff, whereas runoff power mainly affected total Nitrogen loss in runoff. The results of this paper can improve the understanding of runoff and Nitrogen and Phosphorus loss caused by runoff during freeze-thaw conditions.

Driving forces and future trends on total nitrogen loss of planting in China

Protein Losses and Urea Nitrogen Underestimate Total Nitrogen Losses in Peritoneal Dialysis and Hemodialysis Patients

Insight into N2O emission and denitrifier communities under different aeration intensities in composting of cattle manure from perspective of multi-factor interaction analysis

The quantitative relationship between accumulated rainfall and accumulated total nitrogen and total phosphorus loss was analyzed by setting up economic forest experimental sites in typical regions of Zhejiang Province, and the response efficiency of accumulated total phosphorus and total nitrogen loss in different economic forests to rainfall was compared The results showed that there was a significant linear relationship between accumulated rainfall and accumulated total nitrogen and total phosphorus loss. The total nitrogen and total phosphorus loss rate of Castanea mollissima Blum economic forest was higher than that of Phyllostachys edulis forest and nursery > Morella rubra > Camellia sinensis > Phyllostachys edulis. Man-made disturbance of economic forest will accelerate the loss of total nitrogen and total phosphorus, and its loss rate is 1.5~4 times that of natural economic forest. The total nitrogen loss rate of 28% and total phosphorus loss rate of 47% can be reduced by planting shrubs or herbs under the in the Phyllostachys edulis forest. The purification efficiency of total phosphorus and total nitrogen of different economic forests is affected by economic forest types, ecological restoration, rainfall, and the purification efficiency varies between 30% and 70%.

Nitrogen loss is the main reason for land quality degradation and productivity decline and an important factor in groundwater pollution. Extreme rainfall has occurred frequently in Karst areas of southwest China in recent years. It is of great significance to study the response of soil nitrogen loss to extreme rainfall in Karst areas to prevent and treat land quality degradation and non-point source pollution. In this study, field monitoring and indoor artificial rainfall simulation were used to study the loss characteristics of total soil nitrogen (TN), ammonium (NH4+-N) nitrogen, and nitrate-nitrogen (NO3−-N) in Karst bare slope farmland (slope angles of 5° and 10°) under extreme rainfall conditions. The results showed that: (1) Extreme rainfall (90 mm/h) increased the surface runoff, middle soil runoff, and underground runoff by 1.68 times, 1.16 times, and 1.43 times, respectively, compared with moderate rainfall (60 mm/h), so that nitrogen loss increased with runoff. (2) The loss of nitrate-nitrogen in surface, soil, and underground under extreme rainfall conditions was 223.99, 147.93, and 174.02% higher than that under moderate rainfall conditions, respectively; the nitrate losses were 203.78, 160.18, and 195.39% higher, respectively. Total nitrogen losses were 187.33, 115.45, and 138.68% higher, respectively. (3) The influencing factors of total soil nitrogen and nitrate-nitrogen loss in Karst slope farmland were slope > rainfall duration > rainfall intensity, while the influencing factors of ammonium nitrogen loss were rainfall duration > slope > rainfall intensity. Therefore, in controlling nitrogen loss in Karst slope farmland, changing slope degree and increasing farmland coverage may be useful measures to slow the nitrogen loss caused by extreme rainfall.

Due to intensive farm practices, nonpoint-source (NPS) pollution has become one of the most challenging environmental problems in agricultural and mixed land use watersheds. Usually, various conservation practices are implemented in the watershed to control the NPS pollution problem. However, land use changes can mask the water quality improvements from the conservation practices implemented in the watershed. The objectives of this study were to evaluate the linkage between nutrient input from various pasture management practices and water quality, and to quantify the impacts of land use changes and pasture management on water quality in a pasture-dominated watershed. Land use data from 1992, 1994, 1996, 1999, 2001, and 2004 were evaluated for the land use changes in the watershed, and the corresponding implemented management practices were also incorporated into the Soil and Water Assessment Tool (SWAT) model. The individual impacts of land use change and pasture management were quantified by comparing the SWAT simulation results for different land use change and pasture management scenarios. The results indicated that land use changes resulted in greater total sediment (499 kg ha-1) and nitrogen losses (3.8 kg ha-1) in the Moores Creek subwatershed, whereas pasture management resulted in greater total nitrogen losses (4.3 kg ha-1) in the Beatty Branch subwatershed. Overall, the combined impacts of land use changes and pasture management resulted in greater total sediment (28 to 764 kg ha-1 of cumulative combined impacts between 1992 and 2007) and nitrogen losses (5.1 to 6.1 kg ha-1) and less total phosphorus losses (1.5 to 2.1 kg ha-1) in the Beatty Branch, Upper Moores Creek, and Moores Creek subwatersheds. By quantifying the individual impacts of land use changes and pasture management, we found that an increase in total nitrogen losses in the Beatty Branch subwatershed was mainly due to an increase in nutrient inputs in the pasture areas, and total sediment and nitrogen losses in the Moores Creek subwatershed were mainly due to an increase in urban lands. Therefore, the individual impacts of land use changes and conservation practices should be quantified to get a true picture of the success of CEAP programs in watersheds experiencing significant land use changes.

In order to understand the characteristics of soil nitrogen and phosphorus loss under different land use patterns in the small watershed of the Three Gorges Reservoir area and provide a scientific basis for the prevention and control of agricultural non-point source pollution, a field test method was used to study the paddy fields and drought in the small Shipanqiu Watershed in the Three Gorges Reservoir area. The characteristics of different runoff concentrations and the fluxes of nitrogen and phosphorus in surface runoff under the five land use schemes of paddy filed, slope land, woodlands, citrus orchards, and vegetable land. The results show that the annual total nitrogen loss followed the order of paddy field[17.73 kg·(hm2·a)-1] > citrus orchards[4.86 kg·(hm2·a)-1] > dry slope land[4.33 kg·(hm2·a)-1] > vegetable field[4.00 kg·(hm2·a)-1] > woodland[2.41 kg·(hm2·a)-1]. The annual total phosphorous loss followed the order of vegetable fields[4.97 kg·(hm2·a)-1] > Citrus orchards[1.87 kg·(hm2·a)-1] > paddy fields[0.93 kg·(hm2·a)-1] > woodlands[0.27 kg·(hm2·a)-1] > dry slope land[0.19 kg·(hm2·a)-1]. The nitrogen and phosphorus losses under the five land use methods were mainly concentrated from April to May with frequent rainfall events, accounting for 53.80%-96.52% and 56.03%-87.78% of the total annual nitrogen and phosphorus losses. Nitrogen loss was mainly in the form of nitrate nitrogen (16.16%-52.70%), and the total nitrogen loss flux and runoff showed a significant positive correlation (R2=0.9826). Particulate phosphorus was the main form of phosphorus loss in vegetable fields (83.30%), but in other land use schemes it is not significant. There were significant differences in the loss of different forms of nitrogen and phosphorus under the different land use schemes. Among them, measures should be taken in vegetable fields to deal with the problem of particulate phosphorus loss under conditions of heavy rainfall. Fertilization should be avoided in paddy fields during periods of concentrated rainfall. Scientific fertilization and reasonable land use configurations are important ways to control agricultural non-point source pollution in small watersheds.

Mitigation of NH3 and N2O emissions during food waste digestate composting at C/N ratio 15 using zeolite amendment

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.

Role of tobacco and bamboo biochar on food waste digestate co-composting: Nitrogen conservation, greenhouse gas emissions, and compost quality

Carbon and N losses reduce the agronomic value of compost and contribute to greenhouse gas (GHG) emissions. This study investigated GHG emissions during composting of straw-bedded manure (SBM) and wood chip-bedded manure (WBM). For SBM, dry matter (DM) loss was 301 kg Mg(-1), total carbon (TC) loss was 174 kg Mg(-1), and total nitrogen (TN) loss was 8.3 kg Mg(-1). These correspond to 30.1% of initial DM, 52.8% of initial TC, and 41.6% of initial TN. For WBM, DM loss was 268 kg Mg(-1), TC loss was 154 kg Mg(-1), and TN loss was 1.40 kg Mg(-1), corresponding to 26.5, 34.5, and 11.8% of initial amounts. Most C was lost as CO2 with CH4 accounting for <6%. However, the net contribution to greenhouse gas emissions was greater for CH4 since it is 21 times more effective at trapping heat than CO2. Nitrous oxide (N2O) emissions were 0.077 kg N Mg(-1) for SBM and 0.084 kg N Mg(-1) for WBM, accounting for 1 to 6% of total N loss. Total GHG emissions as CO2-C equivalent were not significantly different between SBM (368.4 +/- 18.5 kg Mg(-1)) and WBM (349.2 +/- 24.3 kg Mg(-1)). However, emission of 368.4 kg C Mg(-1) (CO2-C equivalent) was greater than the initial TC content (330.5 kg Mg(-1)) of SBM, raising the question of the net benefits of composting on C sequestration. Further study is needed to evaluate the impact of composting on overall GHG emissions and C sequestration and to fully investigate livestock manure management options.