Rural Non-point Source Research Articles

Enhancing environmental sustainability in transferred farmlands through rural e-commerce: insights from China.

The issue of farmers neglecting environmental concerns in transferred farmlands poses a serious challenge, contradicting the long-term ecological goals of establishing resource-efficient and environment-friendly agriculture. Amidst the pivotal trend of moderately scaled agricultural operations, rural e-commerce holds promise as a catalyst and driving force for enhancing long-term environmental governance of transferred lands. The effectiveness and mechanisms of this potential, however, remain to be empirically examined. This study gathers panel data on environmental positive and negative externalities from six provinces in China, spanning the period from 2013 to 2022, encompassing 6372 farmers. A quasi-natural experiment of farmers' e-commerce participation is designed using difference-in-differences methodology (DID), propensity score matching (PSM), and moderating models. The primary findings are as follows: E-commerce participation increases farmers' positive environmental inputs on transferred lands, such as water-saving irrigation, adoption of social services, and preservation of traditional varieties. Simultaneously, it decreases negative environmental inputs, such as the consumption of fertilizers, pesticides, and agricultural films. The environmental sustainability effects of e-commerce vary across the eastern, central, and western regions of China. E-commerce has a more pronounced impact on agricultural social services and chemical pollutants in the eastern and central regions, while its influence is more significant on water-saving irrigation and variety preservation in the western region. Land transfer forms and supply order contracts do not directly promote farmers' environmentally friendly cultivation practices. Instead, they catalyze the environmental effects of e-commerce through a significant positive interaction term. These conclusions hold after matching for e-commerce participation propensity, while passing sensitivity tests, parallel trend tests, and placebo tests. Consequently, rural e-commerce, without compromising farmers' income, enhances the proactiveness of farmers in environmental conservation, transforms agricultural management practices, and effectively reduces rural non-point source pollution. Policy recommendations include reducing institutional barriers to rural e-commerce participation at the national level, encouraging the establishment of region-specific agricultural environmental sustainability goals, and leveraging the rural e-commerce industry chain to establish a nationwide environmental credit database and incentive mechanism.

Scenario analysis on the management practices and optimization of rural non-point source pollution with the coupling of source-process-end: A case study of the Guishui river basin

Currently, non-point source (NPS) pollution is the primary contributor to water pollution in river basins. Therefore, assessing the benefits of rural non-point source pollution management measures and optimizing their allocation are of great significance for improving water quality. In this study, a SWAT model was firstly constructed for the NPS pollution simulation and optimization based on the four-period land use data, which was more suitable for the Guishui River Basin. And then it was calibrated and verified by using the monitoring data. On the basis of spatiotemporal evolution of total nitrogen (TN) and total phosphorus (TP) in the Guishui River Basin from 2007 to 2019, and the priority control areas for TP and TN were identified based on the RUSLE and additive models. Next, seven management measures scenarios were designed in the priority control areas from the perspectives of hydrological response units (HRUs), sub-basins, and basin scales. Finally, the cost-effectiveness of each scenario was quantitatively evaluated, and the optimal allocation scheme of pollution control management measures was determined. Results showed that the amounts of TP in the Guishui River basin was lower than that of TN, showing a fluctuating downward trend, and the spatial distribution of TP and TN was high in the central and low in the north and southeast. Compared the effect of management measures, it was found that process interception measures were more effective than source control and landscape management measures in reducing the TP and TN. Among them, vegetation filter strips (FS) and grassed waterways (GW) had more environmental benefits and better cost-effectiveness for the pollution reduction. As for the source control measures, 20% chemical fertilizer reduction (FRT20) had relative more effects for the pollutants control than the 10% chemical fertilizer reduction (FRT10) and no-tillage (NTIL). When it refers to landscape management, the reduction effect of return farmland to forest (CFTF) on TP and TN was not much different from that of GW. Considering the costs and benefits of optimized allocation, the combination of FRT20, FS and CFTF had better environmental benefits, while the combination of FRT20 and FS had higher cost-effectiveness. Therefore, the government should control the source emission, strengthen the process interception and pay attention to the end-of-pipe treatment in the downstream. These conclusions can provide a scientific basis for the prevention, control and management of NPS pollution in the Guishui River Basin.

Practice and Exploration of the Improvement of Rural Human Settlement Environment Under the Rural Revitalization Strategy—Take Malingang Town, Mudan District, Heze City as an Example

In recent years, Shandong Province has vigorously implemented the strategy of rural clean project construction throughout the whole province, endeavoring to improve the prevention and control level of rural non-point source pollution, and has carried out beneficial practical exploration on the measures of rural environmental remediation under the strategy of rural revitalization, effectively promoting the rapid and healthy development of the new socialist countryside, which is well received by grassroots cadres and farmers. A number of rural clean project construction demonstration villages have been built preliminarily, which has played a good demonstration and driving role in strengthening rural environmental governance in the future. This paper takes related villages of Malingang Town, Mudan District, Heze City, with obvious effects of rural environmental governance as an example, summarizes the beneficial experience and measures in the governance process, and analyzes the existing problems. From the four aspects of guiding social investment, strengthening the construction of the rule of law, optimizing the fund guarantee and increasing the technical support, the paper provides some useful suggestions for the improvement of rural living environment under the strategy of rural revitalization in Shandong Province in the future.

A novel heterogeneous catalytic system (AC/ZVI/CaO2) promotes simultaneous removal of phosphate and sulfamethazine: Performance, mechanism and application feasibility verification

The eutrophication and pharmaceutical residue are the key issues to the treatment of rural non-point source pollution, concerning risks to aquatic ecosystems and human health. In this study, a novel activated carbon/zero-valent iron/calcium peroxide (AC/ZVI/CaO2) catalytic system was constructed to remove simultaneously typical rural non-point source pollutants: phosphate and sulfamethazine (SMZ). The optimal mass ratio of the system was determined as 20% AC, 48% ZVI and 32% CaO2. It was shown that the removal efficiency of phosphorus (P) and SMZ exceeded 65% and 40% in pH 2–11, respectively. It worked well in the presence of typical anions and humic acid. The mechanistic analyses for P removal indicated that AC/ZVI/CaO2 system can effectively load P by the formation of crystalline state Ca-P species and Fe-P/Ca-P amorphous state coprecipitates under neutral and acidic conditions, respectively. The presence of AC in AC/ZVI/CaO2 system could form iron-carbon micro-electrolysis process for accelerating Fenton reaction in acidic environment. And AC also can produce reactive oxygen species for the SMZ degradation by relying on persistent free radicals/graphitic carbon catalysis under environmental condition. In addition, we developed a low-impact development stormwater filter for application feasibility verification of the system. Feasibility analysis showed that the system could save up to ∼50% cost in contrast with the price of Phoslock (a commercial P load product) and presented advantages of non-toxicity, long-acting, stability and the potential to promote biodegradation by provision of aerobic environment.

Contribution Analysis of External Source Pollution Load and Environmental Capacity Estimation of Reservoirs in Central Yunnan Plateau

To explore the source of the pollution load and its contribution rate in the upper reaches of the plateau reservoir and to analyze the water environment capacity of the reservoir, we selected the Chaishitan Reservoir in the Yunnan Plateau as the research object, applied the pollutant discharge coefficient method to estimate the source of external pollution in the upstream basin of the reservoir, used the simultaneous monitoring data of hydrology and water quality to calculate pollution load into the reservoir, and used the eutrophication model to calculate the maximum capacity of TN and TP in the reservoir under different water quality target scenarios. The results showed that:① the main characteristic pollutants in Chaishitan Reservoir and the above basin were TN and TP. ② COD and TP in the upper reaches of the reservoir mainly came from rural non-point source pollution, with contribution rates of 49.40% and 50.11%, respectively; NH4+-N and TN mainly came from urban domestic pollution sources, with contribution rates of 45.76% and 33.77%, respectively. Among the contributions of rural non-point source pollution, the contribution rates of COD and TP in Luliang District were 34.82% and 36.82%, respectively. The contributions of COD, NH4+-N, TN, and TP to urban domestic pollution were the highest in Qilin District, all of which were up to 65%. ③ The inflows of COD, NH4+-N, TN, and TP were 28050.90, 2465.16, 4680.54, and 870.93 t·a-1, respectively. The inflow of TN and TP pollution load was 4637.80 t·a-1 and 125.04 t·a-1, respectively. ④ When the target of water quality was Class Ⅲ, and the requirements of the Water Function Zoning of Yunnan province were met, the environmental capacities of TN and TP were 1102.62 t·a-1 and 54.85 t·a-1, respectively. Rural non-point source pollution and urban domestic pollution sources were the main sources of pollution in the upper reaches of Chaishitan Reservoir, which were priority control sources. These research results can provide a scientific theoretical basis for pollution source treatment in the plateau reservoir basin.

Differentiated discharge patterns, causes and prevention measures of rural non-point source pollution in the four economic regions of mainland China

Agricultural non-point source pollution has got more attention than rural non-point source pollution (RNPSP) in the past decades. Discharge patterns, causes and prevention measures of RNPSP in the four economic regions of mainland China are still lacking. Based on the framework for RNPSP assessment from agricultural production and rural resident living, inventory analysis and redundancy analysis methods were used to calculate the discharges of RNPSP and identify its influence factors, respectively. During 1978–2019, increased national per capita chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) discharges with values of 1.62, 3.04 and 3.86 times was found, respectively. Northeast and eastern regions always had the higher per capita COD, TN and TP discharges than those of national average. In addition, eastern region had highest average per capita discharges of COD, TN and TP with increased times of 1.90, 2.67 and 2.47 than the national average. The biggest variations of per capita discharges of COD, TN and TP were mainly occurred in Shandong, Liaoning and Fujian provinces from eastern region, and in Inner Mongolia from western region. Livestock and poultry were the dominate sources of per capita COD and TP discharges, while contribution of fertilization was highest to per capita TN discharge. Agricultural production had higher contribution to the national per capita COD, TN and TP discharges with ratios of 75.56%, 90.27% and 82.51%, respectively. Highest contribution of agricultural production in northeast region and rural resident living in western region should be noted. Redundancy analysis shows that pig was the key factor of RNPSP discharges in the four economic regions. Freshwater aquaculture and resident living were the important factors to RNPSP discharges in northeast and eastern regions, respectively, while rice planting should be highlighted to the discharges of RNPSP in central and western regions. Our results revealed the different discharge patterns and causes of RNPSP in the four economic regions of mainland China. The increased RNPSP discharges were associated with intensified agricultural production which was driven by changed resident lifestyles. Targeted RNPSP controlling strategies should be carried out besides the universal and important strategies involving fertilization, and livestock and poultry in four economic regions.

Performance of a Tower-Shaped Integrated Ecological Purification Device for Pollutants Removal from Domestic Sewage in Rural Areas

With the continuous development of China's modern economy and agricultural society, the discharge of rural sewage has been recognized as a major threat to the safety of the rural ecological environment. This study discussed the purification efficiency of a tower-shaped integrated ecological purification device (TIEPD)-consisting of a measuring tank, detention tank and three-stage purification unit-towards various common pollutants in rural areas during operation and tested the stability and efficiency of the TIEPD under different rural life events (fair activity days and nonfair activity days) and different precipitation intensities (light rain, moderate rain and heavy rain). The results showed that the average removal efficiencies of the TIEPD towards chemical oxygen demand, ammonia nitrogen, total nitrogen and total phosphorus were 69%, 67%, 54% and 73%, respectively. The average effluent concentration of each pollutant can meet the standard of the discharge of pollutants in China. The system exhibited good stability in removing pollutants and good ecological and economic benefits. This study provides the treatment of domestic sewage in the upper reaches of the Yangtze River and in mountainous areas of China and strengthens the prevention and control of rural nonpoint source pollution.

Research on Rural Environmental Pollution Control Path Under Administrative Intervention Mechanism

Abstract With the continuous development of urbanisation, the economic level of rural areas has improved greatly. However, due to the development of industry and the leap in the economy, the rural environment has suffered unprecedented damage. Taking Zhejiang Province as an example, this paper explores the rural environmental pollution control path under the government intervention mechanism. Firstly, it analyses the functions of the government in rural environmental pollution control. Then, taking Huzhou as an example, this paper empirically evaluates the willingness to pay for the treatment of living environment pollution in rural areas of Huzhou based on the CVM (Contingent Valuation Method) and analyses the decentralised domestic sewage treatment mode, multi household domestic sewage treatment mode, and waste collaborative treatment mode from the perspective of treatment technology and policy system. Finally, it is proposed that to speed up the governance of the rural environment, and we must strengthen the administrative intervention of the government in rural environmental governance. The government should improve the environmental protection awareness of leaders at all levels and the masses and enrich farmers’ environmental governance knowledge and technical training. Based on the theory of environmental economics, agricultural economics, and decision-making behaviour, this paper analyses the influence mechanism of farmers’ decision-making behaviour and government intervention in rural non-point source pollution control.

Characteristics and driving factors of coastal rural domestic waste of the Yellow River Delta in China

So far, waste discharge has caused serious regional pollution owing to the deficiency of waste management in rural areas located across coastal areas. However, characteristics of rural domestic waste generation and the potential drivers of water eutrophication in the Yellow River Delta remain poorly understood. Under the background that the ecological protection and high-quality development of the Yellow River Basin have risen as a national strategy, the lack of such research is unfavorable to the control of non-point source pollution and the promotion of comprehensive treatment of rural domestic waste. This study, investigated 142 field data from a typical town in the Yellow River Delta in China at the summer of 2020. Then used structural equation modeling and redundancy analysis to characterize the driving factors of rural domestic waste generation and potential polluting components in water from three perspectives: village domestic waste management measures, household characteristics, and consumption habits. The consumption of cleaning products illustrated the maximum explanation rate of waste generation (up to 20.1%), and showed significant effect on the total nitrogen content, and annual household food consumption had a significant impact on organic matter. The “Beautiful Village” and “Waste Classification” pilot villages effectively reduced the content of potential polluting components in the domestic waste of villages, attaining approximately 12.1% reduction in organic matter and 79.8% in total nitrogen. Therefore, to effectively control rural non-point source pollution, it is necessary to implement pilot projects, advocate villagers to reduce unnecessary consumption of cleaning products and dietary ingredients. This work can provide a theoretical basis for rural domestic waste treatment and offshore environmental protection in the Yellow River Delta.

Pollutant Removal Efficiency of a Bioretention Cell with Enhanced Dephosphorization

Low impact development can contribute to Sustainable Development Goals (SDGs) 2, 6, 7, 11, and 13, and bioretention cells are commonly used to reduce nonpoint source pollution. However, although bioretention is effective in reducing ammonia nitrogen and chemical oxygen demand (COD) pollution, it performs poorly in phosphorus removal. In this study, a new type of enhanced dephosphorization bioretention cell (EBC) was developed; it removes nitrogen and COD efficiently but also provides excellent phosphorus removal performance. An EBC (length: 45 m; width: 15 m) and a traditional bioretention cell (TBC) of the same size were constructed in Anhui, China, to treat rural nonpoint source pollution with high phosphorus concentration levels. After almost 2 years of on-site operation, the ammonium nitrogen removal performance of the TBC was 81%, whereas that of the EBC was 78%. The COD removal rates of the TBC and EBC were 51% and 65%, and they removed 51% and 92% of the total phosphorus, respectively. These results indicate that the TBC and EBC have similar performance in the removal of ammonium nitrogen and COD, but the EBC significantly outperforms the TBC in terms of total phosphorus removed.

How Capital Endowment and Ecological Cognition Affect Environment-Friendly Technology Adoption: A Case of Apple Farmers of Shandong Province, China.

Ever-increasing global environmental issues, land degradation, and groundwater contamination may significantly impact the agricultural sector of any country. The situation worsens while the global agricultural sectors are going through the unsustainable intensification of agricultural production powered by chemical fertilizers and pesticides. This trend leads the sector to exercise environmentally friendly technology (EFT). Capital endowment and ecological cognition may significantly impact fostering farmers’ adoption of environmentally friendly technology. The government also tends to change the existing policies to cope with ever-increasing challenges like pollution control, maintaining ecological balance, and supporting agricultural sectors substantially by employing ecological compensation policy. The study’s main objective is to explore the impacts of farmer’s ecological compensation, capital endowment, and ecological cognition for the adoption of EFT. The empirical setup of the study quantifies with survey data of 471 apple farmers from nine counties of Shandong province. The study used Heckman’s two-stage model to craft the findings. The results showed that 52.02% of fruit farmers adopted two environmentally friendly technologies, and 23.99% of fruit farmers adopted three forms of environmentally friendly technologies. At the same time, we have traced that the capital endowment, planting scale, family income, and technical specialization of fruit farmers significantly impact adopting EFT. The study also revealed that understanding ecological compensation policy has a significant positive effect on adopting environmentally friendly technology. Seemingly, ecological compensation policy has a specific regulatory effect on fruit farmers’ capital endowment and ecological cognition. Therefore, it is necessary to extend the demonstration facilities, training, and frequently arrange awareness-building campaigns regarding rural non-point source pollution hazards and improve the cognition level of farmers. The agriculture extension department should strengthen the agricultural value chain facilities to make farmers fully realize the importance of EFT. Government should promote and extend the supports for availing new and innovative EFT at a reasonable price. Moreover, cooperative, financial, and credit organizations need to lead for the smooth transition of EFT. The agricultural cooperatives and formal risk-taking networks should act responsibly for shaping the behavioral factors of farmers.

A WebGIS-Based Platform for Sewage Treatment Facilities in Villages and Small Towns Near the Lake Dian

Lake Dian is one of “Three-river and Three-lake Project” that focus on water pollution prevention and control in China. Rural non-point source pollution is increasing year by year. In order to effectively control the amount of sewage from villages and small towns entering the lake, a full coverage of treatment facilities has been built near the Lake Dian. Among them, the facilities are scattered in the eight districts and two counties of Kunming City, Yunnan Province. It is so difficult to manage that we have to rely on WebGIS technology for management and analysis. This paper designs a visualization platform for sewage treatment facilities in villages and small towns, which is a three-tier system architecture of B/S model. The system takes the map engine of ArcGIS API for JavaScript and the component development of Vue.js as the technical core, combined with ArcGIS Online service portal and spatial database technology. It finishes function implementation such as the visualization of the treatment situation and data management. The platform can scientifically analyse the problems in the construction, management, and operation of sewage treatment facilities in villages and small towns. It improves the ability to share information, and provide decision-making support to the sewage treatment department of the Lake Dian.

Assessing interannual variability in nitrogen sourcing and retention through hybrid Bayesian watershed modeling

Abstract. Excessive nutrient loading is a major cause of water quality problems worldwide, often leading to harmful algal blooms and hypoxia in lakes and coastal systems. Efficient nutrient management requires that loading sources are accurately quantified. However, loading rates from various urban and rural non-point sources remain highly uncertain especially with respect to climatological variation. Furthermore, loading models calibrated using statistical techniques (i.e., hybrid models) often have limited capacity to differentiate export rates among various source types, given the noisiness and paucity of observational data common to many locations. To address these issues, we leverage data for two North Carolina Piedmont river basins collected over three decades (1982–2017) using a mechanistically parsimonious watershed loading and transport model calibrated within a Bayesian hierarchical framework. We explore temporal drivers of loading by incorporating annual changes in precipitation, land use, livestock, and point sources within the model formulation. Also, different representations of urban development are compared based on how they constrain model uncertainties. Results show that urban lands built before 1980 are the largest source of nutrients, exporting over twice as much nitrogen per hectare than agricultural and post-1980 urban lands. In addition, pre-1980 urban lands are the most hydrologically constant source of nutrients, while agricultural lands show the most variation among high- and low-flow years. Finally, undeveloped lands export an order of magnitude (∼7–13×) less nitrogen than built environments.

CFD simulation and experiment on the flow field of air-assisted ultra-low-volume sprayers in facilities

In order to explore the performance of the B-ULV-616A knapsack sprayer, computational fluid dynamics (CFD) was used to simulate the B-ULV-616A knapsack air-assisted device, which features an ultra-low-volume electric sprayer. Field experiments were carried out to test the spraying effects, and the KANOMAX anemometer was used to verify the simulated results. First, the internal and external flow fields and droplet deposition distribution of the ultra-low-volume sprayer were established. The results showed that the air-assisted spray device can change the airflow speed and direction and produce a high-speed swirling airflow at the outlet of the air-assisted spray device. The high-speed airflow (maximum of 83.5 m/s) generates negative pressure (minimum of 0.099 MPa) and causes a rapid increase in the droplet velocity and a secondary droplets spray, allowing droplets to reach a longer distance. Then, the maximum relative error was 20.14%, and its average value was 9.59%, indicating that the CFD method is suitable for the flow field analysis of the air-assisted spray device. Finally, based on the greenhouse experiment, the knapsack air-assisted ultra-low-volume electric sprayer was found to effectively improve the deposition on the rear of the crop, increase the droplet density (maximum of 81/cm2; droplet density of conventional electric sprayer is 64/cm2), and reduce the deposition amount and coefficient of variation (below 20%) within and between regions. Further, it managed to reduce pesticide use (by 69.85%) and rural non-point source pollution. Keywords: CFD simulation, air-assisted sprayer, ultra-low spraying rate, deposition, air-velocity field, relative error DOI: 10.25165/j.ijabe.20211402.6013 Citation: Lu X Y, Gong Y, Liu D J, Wang G, Chen X, Zhang X, et al. CFD simulation and experiment on the flow field of air-assisted ultra-low-volume sprayers in facilities. Int J Agric & Biol Eng, 2021; 14(2): 26–34.

Investigation and Analysis of the Main Pollution Sources in Fuxian Lake

Fuxian Lake is a plateau-based freshwater lake. In recent ten years, with the rapid development of the economy around the lake, the water quality of Fuxian Lake has declined and the nutritional status in lake has increased obviously. To identify the main sources of pollution in Fuxian lake and provide a reference for the protection and management direction and theoretical guidance, the pollution status of Fuxian Lake basin was analyzed and evaluated from the aspects of rural domestic pollution, farmland runoff pollution, urban domestic pollution, phosphorous chemical pollution and tourism pollution, respectively, based on years of field investigation and the indexes detection and analysis such as chemical oxygen demand (COD), total nitrogen, total phosphorus. The results showed that the pollution in Fuxian Lake basin mainly came from the rural non-point source pollution, urban domestic pollution, waste phosphate rock area pollution, tourism pollution and other aspects, among which the most important source of pollution was the rural non-point source pollution, including watershed village pollution, human and animal excrement pollution, rural waste pollution, and farmland runoff pollution in the basin. The COD, total nitrogen and total phosphorus from rural non-point source pollution accounted for 94.81%, 94.85% and 87.79% of the total pollution into the lake, respectively. Among them, the farmland runoff pollution was the most important component of rural non-point source pollution

Enhanced pollutant removal from rural non-point source wastewater using a two-stage multi-soil-layering system with blended carbon sources: Insights into functional genes, microbial community structure and metabolic function

A two-stage multi-soil-layering system with blended carbon sources (MSL–BCS) was constructed at pilot scale for treatment of rural non-point source wastewater. Results showed the MSL–BCS system had effective removal efficiencies with 64% of TN and 60% of TP, respectively. The addition of BCS could result in higher (1.6–3.1 fold) denitrification gene abundances (nirS and nosZ) for enhancing denitrification. High-throughput sequencing approach revealed that the higher abundance (>50%) of Epsilonbacteraeotra (Genus: Sulfuricurvum, Family: Thiovulaceae, Class: Campylobacteria, Phylum: Epsilonbacteraeota) enriched in the surface of BCS, which suggested that Epsilonbacteraeotra are the keystone species in achieving nitrogen removal through enhancing denitrification at oligotrophic level. KEGG analysis indicated that BCS might release some signaling molecules for enhancing the energy metabolism process, as well as stimulate the enzyme activities of histidine kinase, glycogen phosphorylase and ATPase, and thereby the denitrification processes were strengthened in MSL-BCS system. Consequently, this study could provide some valuable information on the removal performance and mechanism of engineering MSL systems packed with BCS to govern the rural wastewater treatment.

Biochar as a tool to reduce environmental impacts of nitrogen loss in water-saving irrigation paddy field

Abstract Nitrogen (N) loss caused by excessive and incorrect application of N fertilizer in traditional rice-growing agriculture contributed to rural non-point source pollution and greenhouse gas emission, reduced crop N utilization efficiency. The objective of this study is to explore the response of N loss (leaching, NH3 volatilization and N2O emission) to different biochar applications (0,20,40 t/hm2) and irrigation patterns (controlled irrigation, flooding irrigation) in paddy fields of the Taihu Lake region (TLR) with the combination of field experiments and laboratory analysis. Based on the long-term observation of rice growth period, the ammonium N (NH4+–N), nitrate N (NO3−–N) and total N (TN) leaching of paddy fields applied with water-saving irrigation (WSI) and biochar was measured in the plots of lysimeter. The impact of biochar application on NH3 volatilization, N2O emission in different water-carbon modes were clarified and the effect of water-carbon management modes on rice yield and yield components was analyzed. The results showed that the application of biochar reduced the NO3−–N and TN leaching by 29.98%–38.63% and 12.77%–13.36%, increased rice seed setting rate and actual yield by 12.15%–15.28% and 1.67%–5.54%. Biochar addition inhibited NH3 volatilization and N2O emission. Under low-volume biochar (20 t/hm2), the main form of N leaching in rice fields was NO3−–N, the NO3−–N leaching accounted for 33.67% – 50.24% of the TN leaching; under high-volume biochar (40 t/hm2), N leaching in rice field was dominated by NH4+–N, the NH4+–N leaching accounted for 16.50% – 47.47% of the TN leaching. Controlled irrigation can not only reduce the water leakage in paddy fields but also reduce the N concentration in water leakage compared with flooding irrigation so that the total leaching of NH4+–N, NO3−–N and TN in rice fields can be reduced by 23.44%, 47.89% and 50.69%. This study suggests that to make biochar beneficial for reducing environmental impacts of soil N effluxes and realizing cleaner production in rice cultivation, WSI technique and adapted use of biochar are of great importance.

CFD simulation and experiment on the flow field of air-assisted ultra-low-volume sprayers in facilities

In order to explore the performance of the B-ULV-616A knapsack sprayer, computational fluid dynamics (CFD) was used to simulate the B-ULV-616A knapsack air-assisted device, which features an ultra-low-volume electric sprayer. Field experiments were carried out to test the spraying effects, and the KANOMAX anemometer was used to verify the simulated results. First, the internal and external flow fields and droplet deposition distribution of the ultra-low-volume sprayer were established. The results showed that the air-assisted spray device can change the airflow speed and direction and produce a high-speed swirling airflow at the outlet of the air-assisted spray device. The high-speed airflow (maximum of 83.5 m/s) generates negative pressure (minimum of 0.099 MPa) and causes a rapid increase in the droplet velocity and a secondary droplets spray, allowing droplets to reach a longer distance. Then, the maximum relative error was 20.14%, and its average value was 9.59%, indicating that the CFD method is suitable for the flow field analysis of the air-assisted spray device. Finally, based on the greenhouse experiment, the knapsack air-assisted ultra-low-volume electric sprayer was found to effectively improve the deposition on the rear of the crop, increase the droplet density (maximum of 81/cm2; droplet density of conventional electric sprayer is 64/cm2), and reduce the deposition amount and coefficient of variation (below 20%) within and between regions. Further, it managed to reduce pesticide use (by 69.85%) and rural non-point source pollution. Keywords: CFD simulation, air-assisted sprayer, ultra-low spraying rate, deposition, air-velocity field, relative error DOI: 10.25165/j.ijabe.20211402.6013 Citation: Lu X Y, Gong Y, Liu D J, Wang G, Chen X, Zhang X, et al. CFD simulation and experiment on the flow field of air-assisted ultra-low-volume sprayers in facilities. Int J Agric & Biol Eng, 2021; 14(2): 26–34.

A three-dimensional and multi-source integrated technology system for controlling rural non-point source pollution in the Three Gorges Reservoir Area, China

Techniques for controlling rural non-point source pollution (RNSP) represent cleaner production techniques that can provide an effective guarantee for regional sustainable development. The majority of studies on RNSP control technologies are mainly aimed at handling only a single pollution source. However, such studies are difficult to perform in rural areas, which have dense populations, complex terrains and extreme climates, such as the Three Gorges Reservoir Area (TGRA), China. Therefore, this paper focuses on the application of the RNSP control technologies based on the following four aspects: crop planting, livestock production, domestic inputs and water-level-fluctuating (WLF) zone. Based on the unique topography, land features and planting patterns of the TGRA, a three-dimensional (3D) and multi-source integrated technology system for controlling RNSP was established according to the principle of source reduction, runoff regulation, and nitrogen (N) and phosphorus (P) loss control. From the results of the long-term observations, the risk of RNSP has been significantly reduced in the study area. The nutrient capacity of the soil increased by 9–15%, while the chemical fertilizer application reduced by 30–50%. The loss of sediment, N and P were reduced by 60–80%, 30–70% and 50–90% in the sloping land at the backslope, respectively, by 30–60%, 70–90%, and 70–90% in the paddy field at the footslope, respectively, and by 75–90%, 30–50%, 65–95% in the WLF zone, respectively. The average removal rates of COD, NH3-N and TN in sewage in the residential area were higher than 82%, 87% and 63.3%, respectively. Overall, more than 90% of RNSP was reduced by using this 3D and multi-source technology system, and it can be widely promoted for controlling RNSP in similar ecological areas with support from local governments by implementing effective measures, such as strengthening environmental protection education and government subsidies.

Framework for quantifying rural NPS pollution of a humid lowland catchment in Taihu Basin, Eastern China

Controlling of rural non-point sources (NPS) pollution has been a major priority of Chinese government in an initiative to improve the rural living environment. However, quantifying NPS pollution remains a considerable challenge in the humid lowland rural areas of Eastern China, which are characterized by complicated hydrological and nutrient processes and exhibits intensified artificial interference. In this study, a new and feasible framework was developed to estimate different NPSs specifically for this area by combing hydrological modelling, export coefficient, and sediment release experiment. Then the framework was applied to a typical lowland area (Zongjiaqiao River catchment) in Eastern China. The results showed that annual total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (COD), and ammonia–nitrogen (NH3–N) in the area were 8.49 t, 0.63 t, 83.71 t, and 4.22 t, respectively. Rainfall-runoff contributed more NPS (except for TP) loads to the river than other sources and had a substantial spatiotemporal difference in contrast to other sources. Rural living was the largest source for TP, with a total TP load of 58%. The majority of this TP was derived from toilets and laundry areas. Sediment was another important source, particularly for TN and NH3–N pollution. Nevertheless, the livestock here contributed the least to water pollution. The proposed method has extensive application potential in critical source identification and policy drafting for rural NPS pollution control of lowland area.