Non-point Source Research Articles

Effects of Biochar on Gaseous Carbon and Nitrogen Emissions in Paddy Fields: A Review

The paddy field is a major source of gaseous carbon and nitrogen emissions, and reducing these emissions is of great significance for mitigating greenhouse effects and non-point source pollution in farmland. Biochar, derived from agricultural waste, possesses a stable structure, large specific surface area, abundant pore structures, and surface functional groups. These characteristics could enhance soil physicochemical properties and microbial activity, thereby facilitating the dual goals of increasing crop yield and reducing emissions. Based on numerous studies, this review summarizes the effects of biochar on the emissions of carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ammonia volatilization (NH3), as well as on global warming potential (GWP) and greenhouse gas emission intensity (GHGI). It elucidates the mechanism of emission reduction by biochar amendment from the perspective of carbon and nitrogen conversion processes and soil physicochemical and biological properties. Numerous studies showed the application of 5~40 t ha−1 biochar reduced CO2, CH4, N2O, and NH3 emissions by 1.64~89.6%, 8.6~89.6%, 10~90%, and 12.27~53%, respectively. A small number of studies found that the application of 5~48 t ha−1 biochar increased CO2, CH4, N2O, and NH3 emissions by 12~37%, 19.85~176%, 13~84.23%, and 5.47~70.9%, respectively. Most scholars have found that biochar has varying degrees of emission reduction capabilities in different parts of the world. Therefore, future research directions have been suggested for utilizing biochar to reduce carbon and nitrogen emissions in paddy fields.

The response of non-point source pollution to climate change in an orchard-dominant coastal watershed

China is the largest global orchard distribution area, where high fertilization rates, complex terrain, and uncertainties associated with future climate change present challenges in managing non-point source pollution (NPSP) in orchard-dominant growing areas (ODGA). Given the complex processes of climate, hydrology, and soil nutrient loss, this study utilized an enhanced Soil and Water Assessment Tool model (SWAT-CO2) to investigate the impact of future climate on NPSP in ODGA in a coastal basin of North China. Our investigation focused on climate-induced variations in hydrology, nitrogen (N), and phosphorus (P) losses in soil, considering three Coupled Model Intercomparison Project phase 6 (CMIP6) climate scenarios: SSP1-2.6, SSP2-4.5, and SSP5-8.5. Research results indicated that continuous changes in CO2 levels significantly influenced evapotranspiration (ET) and water yield in ODGA. Influenced by sandy soils, nitrate leaching through percolation was the principal pathway for N loss in the ODGA. Surface runoff was identified as the primary pathway for P loss. Compared to the reference period (1971–2000), under three future climate scenarios, the increase in precipitation of ODGA ranged from 15% to 28%, while the growth rates of P loss and surface runoff were the most significant, both exceeding 120%. Orchards in the northwest basin proved susceptible to nitrate leaching, while others were more sensitive to N and P losses via surface runoff. Implementing targeted strategies, such as augmenting organic fertilizer usage and constructing terraced fields, based on ODGA's response characteristics to future climate, could effectively improve the basin's environment.

Drivers and mechanisms of harmful algal blooms across hydrologic extremes in hypereutrophic grand lake st marys (Ohio)

Grand Lake St. Marys (GLSM) is a large, shallow, hypereutrophic lake situated in an agricultural watershed with high-nutrient, non-point source runoff. The resulting harmful algal blooms (HABs) are typically dominated by Planktothrix, which can produce microcystin, a potent cyanobacterial toxin that has varied in concentration over the past decade. Some drivers of bloom biomass and toxicity in GLSM are described, but recent years (2019–2022) have exhibited anomalous combinations of winter ice cover and spring runoff, suggesting that additional factors contribute to variability in HAB severity and toxicity. 2020 and 2022 were typical water years, with normal tributary runoff volumes occurring primarily in late winter and spring after either little to no ice cover (2019–2020) or heavy/prolonged ice cover (2021–2022). However, 2021 exhibited prolonged winter ice and low winter/spring runoff. 2020 and 2022 were typical bloom years, with near monoculture, Planktothrix-dominated biomass (11 to 405 μg/L total chlorophyll) and high total concentrations of microcystins (<0.3 to 65 μg/L). However, the first half of 2021 exhibited lower biomass (18 to 65 μg/L chlorophyll a) and toxin concentrations (0.4 to 2.0 μg/L). While biomass returned to bloom levels when external tributary loading increased, ammonium uptake and regeneration rates and microcystin concentrations remained low throughout 2021 (in contrast to other years). Overall, potential ammonium uptake rates strongly correlated with chlorophyll and microcystin concentrations (Bayesian R2 = 0.59; 95% CI = 0.44 to 0.65). Phytoplankton diversity was higher in 2021 than other years, especially in spring/early summer, with increased dinoflagellates and diatoms in spring, followed by a mixed cyanobacterial assemblage in summer. These results suggest that lower external nutrient loads can drive immediate positive impacts on water quality, such as reduced HAB biomass and toxicity and higher phytoplankton diversity, even in hypereutrophic, shallow lakes.

RETRACTED: Assessing nonpoint source pollution risk in watersheds using a water-functioning zone approach

A thorough understanding of the geographical and spatial attributes of nonpoint source pollution risk in watersheds is crucial for conducting nonpoint source pollutant studies and implementing effective scientific administration strategies. The inclusion of a water-related functioning zone was considered during the nonpoint source's pollution risks assessment procedure. Nevertheless, there has not been a thorough investigation into the potential risk of nonpoint sources of pollution to adequately safeguard the quality of water in watersheds having varying capacities to handle contaminants in the water. This research presents an innovative approach for assessing the risk of nonpoint sources contamination. This allows for a quantitative evaluation of the effect of discharges of pollution from a sub-catchment on the quality of water bodies nearby. The nonpoint source losses of nutrients process, as modeled by the Water and Soil Assessment Tool, had been used to assess the hazard of nonpoint source contamination in Le ‘a River Watersheds. This assessment happened on both yearly and monthly scales. The findings indicated that the risk of nonpoint source contamination exhibits both seasonal and regional variations and is significantly impacted by the ability of the fluid ecosystem. Elevated nonpoint sources pollutants do not always equate to elevated pollutant dangers. On the other hand, a small amount of nutrients in the nonpoint sources does not indicate an insignificant degree of susceptibility to region risk. Furthermore, by utilizing a risk assessment method that considers the capacity of the water's environment, it is possible to identify variations in risk levels that may be overlooked when solely considering nonpoint sources contaminant losses, and fluid functioning zone. This approach allows for precise regulation of nonpoint sources of pollution administration.

Multiobjective layout optimization for low impact development considering its ecosystem services

The augmented proportion of impervious surfaces and heavy rainfall have resulted in waterlogging, nonpoint source pollution, and environmental degradation. Low impact development (LID) is an effective storm management practice. Based on six different LID paving scenarios, a four objective simulation-optimization framework coupled with stormwater management model (SWMM) and NSGA-Ⅱ that incorporates the ecosystem service value (ESV) was proposed for the optimal layout of LID facilities. A case study in Beijing, China, was taken as an example. The results showed that the rain garden paving scenario is remarkable compared to the other scenarios in realizing ESV, with the dominant ESV of net carbon sinks. The optimization revealed that the change in pollution control rate was more sensitive than the runoff reduction rate. Simultaneously, the optimization of these two indicators will be accompanied by more cost and lower ESV. The optimal solution achieved 32.48 % of runoff reduction rate, 82.22 % of water pollution control rate, 0.73×105 CNY of ESV, and 2.29×106 CNY of cost. The framework provides reference and technical support to achieve the synergistic objectives among cost, water quality and quantity control, and ecosystem services.

Dynamic analysis of non-point source pollution in the Sanhekou Reservoir watershed: Implications for sustainable water management

Exogenous pollution, especially non-point source pollution runoff during a flood season, is an important factor affecting the water quality of reservoirs. The Sanhekou Reservoir (Shaanxi, China) is a newly dammed water body, so its non-point source pollution characteristics are unknown. In this study, three major tributaries of the Sanhekou Reservoir watershed were sampled during five rainfall-runoff events in the 2022 flood season. This enabled study of the transport processes of nitrogen, phosphorus, and suspended particles in the runoff under different rainfall conditions. Using hysteresis and redundancy analyses, the sources and transport modes of pollutants are explored here, alongside analysis of rainfall and hydrological characteristics that affect pollutant concentrations, and exploration of land-use relationships. The results showed that (i) nitrate nitrogen and particulate nitrogen were the main forms of nitrogen output, and particulate phosphorus was the main form of phosphorus output. (ii) Total nitrogen, suspended particles, total phosphorus, and particulate phosphorus were significantly affected by maximum rainfall intensity, average rainfall intensity, and average flow rate, whereas nitrate nitrogen and ammonia nitrogen were significantly affected by rainfall duration, rainfall amount, and rainfall-runoff duration. (iii) If 70 % of barren land and cultivated land with slope >15° were converted to forests, total nitrogen, total phosphorus, and suspended particulate loads in the Sanhekou Reservoir would be reduced during the flood season by 10.37 %, 33.01 %, and 45.39 %, respectively. The factors influencing migration and transformation of pollutants during rainfall runoff are important for operational scheduling decisions of reservoirs and guaranteeing quality of the water supply.

Agricultural watershed conservation and optimization using a participatory hydrological approach.

Maximizing the impact of agricultural wastewater conservation practices (CP) to achieve total maximum daily load (TMDL) scenarios in agricultural watersheds is a challenge for the practitioners. The complex modeling requirements of sophisticated hydrologic models make their use and interpretation difficult, preventing the inclusion of local watershed stakeholders' knowledge in the development of optimal TMDL scenarios. The present study develops a seamless modeling approach to transform the complex modeling outcomes of Hydrologic Simulation Program Fortran (HSPF) into a simplified participatory framework for developing optimized management scenarios. The study evaluates seven conservation practices in the Pomme de Terre watershed in Minnesota, USA, focusing on sediment and phosphorus pollutant load reductions incorporating farmers' opinions to guide practitioners toward implementing cost-effective CPs. Results show reduced tillage and filter strips are the most cost-effective practices for non-point source pollution reduction, followed by conservation cover perennials. The integration of SAM with HSPF is crucial for sustainable field-scale implementation of conservation practices through enhanced involvement of amateur-modeling stakeholders and farmers directly connected to fields.

Three-dimensional perspectives on revisiting the legacy impacts of non-point source phosphorus

Three-dimensional perspectives on revisiting the legacy impacts of non-point source phosphorus

Neonicotinoid insecticides in a large-scale agricultural basin system-Use, emission, transportation, and their contributions to the ecological risks in the Pearl River Basin, China

Neonicotinoid pollution has increased rapidly and globally in recent years, posing significant risks to agricultural areas. Quantifying use and emission, transport and fate of these contaminants, and risks is critical for proper management of neonicotinoids in river basin. This study elucidates use and emissions of neonicotinoid pesticides in a typical large-scale agriculture basin of China, the Pearl River Basin, as well as the resulting agricultural non-point source pollution and related ecological risks using market surveys, data analysis, and the Soil and Water Assessment Tool. Neonicotinoid use in the basin was estimated at 1361 t in 2019, of which 83.1 % was used in agriculture. After application, approximately 99.1 t neonicotinoids were transported to the Pearl River, accounting for 7.2 % of the total applied. Estimated aquatic concentrations of neonicotinoids showed three seasonal peaks. Several distinct groups of neonicotinoid chemicals can be observed in the Pearl River, as estimated by the model. An estimated 3.9 % of the neonicotinoids used were transported to the South China Sea. Based on the present risk assessment result, several neonicotinoids posed risks to aquatic organism. Therefore, the use of alternative products and/or reduced use is deemed necessary. This study provides novel insights into the fate and ecological risks of neonicotinoid insecticides in large-scale watersheds, and underscores the need for greater efficiency of use and extensive environmental monitoring.

A dataset of riverine nitrogen yield across watersheds in the Conterminous United States

Riverine nitrogen is a pivotal determinant influencing water quality in inland and coastal waters. Despite the recognized utility, no spatially-explicit data on riverine nitrogen yield is available for large parts of the world, thus hindering our ability to identify the contributors to riverine nitrogen and understand aquatic nitrogen cycling. To fill the data gap for the United States, here we (1) compiled 294,996 total nitrogen (TN), 225,827 nitrate (NO3−), 204,015 ammonium (NH4+), and 158,837 total organic nitrogen (TON) concentrations, with concurrent streamflow data, across the Conterminous United States (CONUS), (2) estimated riverine nitrogen loads for over 1,800 hydrological stations, (3) derived the spatial distribution of annual riverine nitrogen yield by leveraging river and catchment connectivity information contained in the National Hydrography Dataset plus (NHDPlus), and (4) characterized nonpoint-source TN loads by excluding point-source loads. This new spatial dataset quantifies spatial sources of nitrogen yield from point and non-point sources (e.g., up to 36% from point sources across the U.S.) and serves as ground-truthing to validate water quality models.

Mapping the Nexus: A County-Level Analysis and Visualization of Iowa’s Food–Energy–Water Systems

This study presents a county-level analysis and visual assessment of Iowa’s Food–Energy–Water systems (IFEWs), focusing on the interdependencies of agricultural practices, nitrogen management, and energy production. We use data from the USDA National Agricultural Statistics Service and other sources to assess cropland-nitrogen sources, animal-based-nitrogen contributions, and ethanol production capacity across Iowa’s counties. Our methodology leverages geoprocessing and interpolation tools to address data availability challenges and refine nitrogen surplus (Ns) estimates. The results reveal spatial–temporal dynamics of cropland-nitrogen, quantify non-point nitrogen sources at the county level, and evaluate the impact of energy systems on the IFEWs balance. We discuss the implications of our findings for sustainable agriculture, environmental management, and energy production in Iowa. The study highlights the need for integrated approaches to address the complex interactions within the IFEWs and informs policy development for sustainable resource management.

A modified approach of the agricultural grey water footprint considering the nitrogen fixation effect of crops in China

The rapidly growing demand for food in human societies has led to the extensive use of fertilizers, significantly contributing to water pollution. Grey water footprints (GWF) serve as a crucial method for measuring Non-point Source (NPS) pollution, particularly in agriculture. Traditional assessments of agricultural GWF neglect biologically fixed nitrogen and the use of organic fertilizers. This research proposed a modified method to assess the GWF of Chinese agriculture from 2000 to 2020, considering the impact of Nitrogen fixation in crops and the use of organic fertilizer. We also analyzed the determinants of Agricultural Nitrogen Fixation Intensity (ANFI) using the Logarithmic Mean Divisia Index (LMDI) method to better understand factors influencing agricultural GWF. Our findings include (1) Grain cereals (e.g., maize, rice, and wheat) significantly contribute to nitrogen fixation in crop organs, accounting for 87.7%, whereas the other six economic crops contribute the rest of 12.3%. Human wastes account for Nitrogen emissions for 1.40%, and emissions by livestock product, red meat contributes 16.26%, while white meat, eggs, and milk collectively contribute 82.34%. (2) Across China, there is an overestimation of GWF by 22.4 hundred million m3 per year, about 5.13% of the total GWF measured by traditional methods. It appears that the overestimation of GWF in plain regions with more arable land tends to be somewhat more pronounced compared to plateau and coastal municipalities. Biotechnological advancements in the capacity of nitrogen fixation for key crops (e.g., maize, wheat, rice) can alleviate agricultural water pollution. The modified methodology provides a robust scientific basis for a more precise application of GWF assessments, highlighting the substantial overestimation by traditional methods in China.

Tripartite evolutionary game and simulation analysis of agricultural non-point source pollution control

Tripartite evolutionary game and simulation analysis of agricultural non-point source pollution control

Quality evaluation and health risk assessment of karst groundwater in Southwest China

Groundwater in karst regions is of immense value due to its vital support for regional ecosystems and residents' livelihoods. However, it is simultaneously threatened by multi-source pollution from agricultural non-point sources, industrial and domestic point sources, and mining activities. This study focuses on the Guangxi of China, which features typical karst topography, aiming to thoroughly assess the groundwater quality and related health risks in Guangxi, especially identifying the impacts of various key pollution sources on the groundwater environment. A total of 1912 groundwater samples were collected, covering an area of approximately 237,600 km2. The spatial distribution of pollutants was analysed using the Nemeroww index method and Kriging interpolation, while multivariate statistical and cluster analysis methods were employed to identify the main types of pollution sources. Furthermore, based on the human health risk assessment model of the U.S. Environmental Protection Agency (US EPA), a risk assessment was conducted for key pollutants. The results revealed widespread heavy metal contamination in Guangxi's groundwater, particularly with concentrations of Mn, As, Al, Pb reaching up to 9.4 mg/L, 2.483 mg/L, 37.95 mg/L, 4.761 mg/L, respectively, significantly exceeding China's national Class III groundwater quality standards. Cluster analysis indicated that mining and industrial activities are the primary sources of pollution. The health risk assessment demonstrated that these activities pose a significant risk to public health. The aim of this study is to provide a scientific basis for the protection of the groundwater environment in Guangxi and other karst areas, the formulation of pollution prevention and control strategies, and the optimization of urban and industrial land use layouts. Future research should focus on advanced isotopic and molecular biological techniques to trace pollution sources more precisely and evaluate the effectiveness of pollution control measures.

An Imputation Method for Simulating 3D Well Screen Locations from Limited Regional Well Log Data.

In groundwater modeling studies, accurate spatial and intensity identification of water sources and sinks is of critical importance. Precise construction data about wells (water sinks) are particularly difficult to obtain. The collection of well log data is expensive and laborious, and government records of historic well log data are often imprecise and incomplete with respect to the precise location or pumping rate. In many groundwater modeling studies, such as groundwater quality assessments, a precise representation of the horizontal and vertical distribution of well screens is required to accurately estimate contaminant breakthrough curves. The number of wells under consideration may be very large, for example, in the assessment of nonpoint source pollution. In this paper, we propose an imputation framework that allows for proper reconstruction of missing well data. Our approach exploits available information and tolerates data gaps and imprecisions. We demonstrate the value of this method for a subregion of the Central Valley aquifer (California, USA). We show that our framework imputes missing values that preserve statistical properties of available data and that remain consistent with the known spatial distribution of well screens and pumping rates in the three-dimensional aquifer system.

Can the best management practices resist the combined effects of climate and land-use changes on non-point source pollution control?

Climate and land-use changes have an overlying impact on non-point source (NPS) pollution in river basins. However, the control effect of Best Management Practices (BMPs) for NPS pollution is not yet clear under future scenarios. The Soil and Water Assessment Tool (SWAT) model was coupled with the entropy-weighted method, global climate patterns and land-use data to explore the dynamic variations in total nitrogen (TN) and total phosphorus (TP) loads in the Jing River Basin during the baseline (2000−2020) and future periods (2021–2065), evaluate the pollution reduction effectiveness of individual and combined BMPs, and propose practical BMP configurations. Results indicate that a future trend of urban land expansion, particularly in the economic scenario (LU_SSP585), leads to weakened environmental ecosystems, while the sustainable scenario (LU_SSP126) exhibits more balanced land development. The MIROC-ES2L model demonstrates higher Taylor skill scores, forecasted significant increases in precipitation, maximum, and minimum temperatures under the SSP585 scenario. Spatial heterogeneity in TN and TP loads is notable, showing an upward trajectory in the future. The interaction between land-use and climate change has complex effects on TN and TP loads, with land-use-induced TN changes being relatively small (4.6 %) and TP changes substantial (24.3 %). The spatial distribution, under overlying effects, leans towards the influence of climate change, emphasizing its dominant role in TN and TP load variations. Distinct differences exist in the reduction of NPS pollution loads among different BMPs, with combined BMPs demonstrating superior effectiveness. The environmental-cost effectiveness trends of BMPs remain consistent across various future scenarios. RG (Return agricultural land to grass), RG + TT (Terracing), and RG + FR10 (Fertilizer reduction: 10 %) + GW (Grassed waterway) + FS (Filter strip) + TT emerge as the most effective single, double, and multiple BMP combinations, respectively. The results offer valuable insights for preventing and mitigating future NPS pollution risks, optimizing land-use layouts, and enhancing watershed management decisions.

Contribution of the ratoon sugarcane with planting years to river pollution evidenced from the four-year watershed observation

Non-point source pollution water erosion caused by sugarcane planting on sloping land is a serious environmental problem in tropical and subtropical regions. The adjustment of sugarcane planting patterns (ratio of perennial to new planting areas) will affect slope soil erosion. However, the relationship between the contribution of sugarcane land to river pollution load and the planting years of ratoon sugarcane remains unclear. To quantitatively analyse the contribution of sugarcane fields to eroded sediment nitrogen (N) and phosphorus (P) loads into the river in different ratoon years and growing seasons, this study was conducted in the intensive sugarcane cultivation area of the southern subtropical Guangxi Nala sub watershed, using the specific compound specific stable isotope (CSSI) traceability technology and real-time monitoring in the watershed. The changes of N and P loading of sugarcane soil erosion and sediment into the river was determined at different ratoon years (RS0-RS3) in addition to the related influencing factors. The results showed that the influence of different ratoon years on the N and P input loads of eroded sediment from sugarcane fields was significantly greater than that of runoff. The contribution of different ratoon sugarcane planting years (including root density) to the loads of sediment N and P into the river was 67.1 % (p < 0.01), which was 2.8 times that of runoff (24.3 %) (p < 0.05). With increasing ratoon sugarcane planting years, the N and P loads of sediment into the river from the sugarcane land decreased significantly; the ratoon sugarcane planting years showed a highly significant negative correlation with the N loads of sediment into the river from the sugarcane fields (p < 0.01), and a significant negative correlation with P (p < 0.05) was observed. Newly planted sugarcane contributed the most to the N and P sediment loads into the river at the seedling stage and the least at the maturity stage. Therefore, in the intensive sugarcane planting areas, to effectively control erosion-induced non-point source pollution, perennial sugarcane planting areas should be rationally in the newly planted sugarcane fields, especially at the seedling stage, to increase land surface cover.

Technical note: An open-source, low-cost system for continuous monitoring of low nitrate concentrations in soil and open water

Abstract. Nitrate (NO3-), mainly leaching with soil porewater, is the primary nonpoint source pollutant of groundwater worldwide. Obtaining real-time information on nitrate levels in soils would allow for gaining a better understanding of the sources and transport dynamics of nitrate through the unsaturated zone. However, conventional nitrate detection techniques (e.g., soil sample analysis) necessitate costly, laboratory-grade equipment for analysis, along with human resources, resulting in a laborious and time-intensive procedure. These drawbacks raise the need to develop cost-effective and automated systems for in situ nitrate measurements in field conditions. This study presents the development of a low-cost, portable, automated system for field measurements of nitrate in soil porewater and open water bodies. The system is based on the spectrophotometric determination of nitrate using a single reagent. The system design and processing software are openly accessible, including a building guide, to allow duplicating or changing the system according to user-specific needs. Three field tests, conducted over 5 weeks, validated the system's measurement capabilities within the range of 0–10 ppm NO3-–N with a low RMSE of &lt;0.2 ppm NO3-–N when comparing the results to standard laboratory nitrate analysis. Data derived from such a system allow for tracking of the temporal variation in soil nitrate, thus opening new possibilities for diverse soil and nutrient management studies.

A novel hydrodynamic-water quality coupling model for high-efficiency and high-resolution simulations of urban NSPs

Nonpoint source pollution (NSP) is one of the main factors leading to black odor in urban rivers. A better understanding and simulation of the formation and transport mechanism of NSP is critical to the development of effective urban rainwater management and pollution control strategies. This work presents a novel hydrodynamic-water quality coupling model to quantitatively simulate the entire physical process of the urban NSP by integrating two-dimensional (2D) NSP build-up, wash-off and transport modules into the source code of the GPU-accelerated surface water and transport (GAST) model. The advantages of this model are that high-resolution terrain is considered, such as key microtopography, such as roads and houses, which will have a diversion effect on the transport of hydrodynamic water quality and affect, and detailed hydrodynamic processes based on physical processes are fully considered. Additionally, a graphical processing unit (GPU)-based acceleration method is introduced to increase the parallel performance of the computing process. Three scales of cases were used to verify the model. First, indoor experimental data from the model roof and measured data from the campus roof under two short-duration rainstorms were used for nonpoint source model verification. The Nash-Sutcliffe efficiency (NSE), root mean square error (RMSE), Bayesian information criterion (BIC) and Akaike information criterion (AIC) were utilized to assess the applicability of the different NSP wash-off equations added to this model. Based on this model, the NSP mechanism processes of residential buildings were examined. The results indicate that this model is suitable for various pollutant wash-off formulas and is capable of high-efficiency and robust predictions of the sources, transmission paths, and spatiotemporal distribution characteristics of urban nonpoint sources. We quantitatively simulated the generation and transport of NSP from a single roof and proposed an NSP traceability method based on detailed hydrodynamic processes. This model can provide strong technical support for the precise treatment of urban NSP and the construction of sponge facilities.

Evaluation of agricultural non-point source pollution using an in-situ and automated photochemical flow analysis system

Off-line leachate collection from agricultural landscapes cannot guarantee precise evaluation of agricultural non-point source (ANPS) due to geospatial variations, time, and transportation from the field to the laboratory. Implementing an in-situ nitrogen and phosphorous monitoring system with a robust photochemical flow analysis is imperative for precision agriculture, enabling real-time intervention to minimize non-point source pollution and overcome the limitations posed by conventional analysis in laboratory. A reliable, robust and in-situ approach was proposed to monitor nitrogen and phosphorous for determining ANPS pollution. In this study, a home-made porous ceramic probe and the frequency domain reflectometer (FDR) based water content sensors were strategically placed at different soil depths to facilitate the collection of leachates. These solutions were subsequently analyzed by in-situ photochemical flow analysis monitoring system built across the field to estimate the concentrations of phosphorus and nitrogen. After applying both natural and artificial irrigation to the agricultural landscape, at least 10 mL of soil leachates was consistently collected using the porous ceramic probe within 20 min, regardless of the depth of the soil layers when the volumetric soil water contents are greater than 19%. The experimental results showed that under different weather conditions and irrigation conditions, the soil water content of 50 cm and 90 cm below the soil surface was 19.58% and 26.08%, respectively. The average concentrations of NH4+-N, NO3−-N, PO43− are 0.584 mg/L, 15.7 mg/L, 0.844 mg/L, and 0.562 mg/L, 16.828 mg/L and 0.878 mg/L at depths of 50 cm and 90 cm below the soil surface, respectively. Moreover, the comparison with conventional laboratory spectroscopic analysis confirmed R2 values of 0.9951, 0.9943, 0.9947 average concentration ranges of NH4+-N, NO3−-N, and PO43−, showcasing the accuracy and reliability of robust photochemical flow analysis in-situ monitoring system. The suggested monitoring system can be helpful in the assessment of soil nutrition for precision agriculture.