Field Drainage Research Articles

Результаты исследований температурного режима осушаемой торфяной почвы

When cultivating row crops on depleted peatlands introduced into agricultural circulation using the peat soil farming practice, post-sowing tillage (harrowing, inter-row loosening, hilling and thinning of plants in rows) changes the thermophysical properties of peat, increasing the probability of a peat fire. To study the temperature and humidity mode of the upper fi re-hazardous layer of the peat soil on a drained fi eld used for vegetable and fodder crop rotation, studies were carried outon the drained Kalskoye swamp in the Ryazan region. Measurements of the soil parameters were carried out on its surface and in the upper layer of 0 to 5 cm. When modeling spontaneous combustion and forced ignition of the peat soil, the results of experimental fi eld studies were used. Based on the practical data obtained, the authors proposed mathematical dependencies for calculating the possibility of spontaneous combustion of peat soils. Comparison of experimental and calculated data showed that their discrepancy is 2.2% to 15.6%. The obtained mathematical dependencies can be used to predict the probability of fi res on peat soils. The authors propose a scheme of a new method for monitoring the fi re hazard situation on drained peatlands during their introduction into agricultural production. This method of monitoring, based on the criterion of uneven heating, is useful for taking preventive measures against the peat soil ignition on agricultural land.

Metaldehyde Transport Processes in a Water Abstraction Catchment in Essex, Southeast England

This paper addresses the issue of pesticide loss from agriculture and its impact on the aquatic environment. Specifically, this study assesses the transport of the relatively water-soluble polar molluscicide compound metaldehyde in a small (14 km2) water abstraction catchment in Essex, southeast England during a 14-month period (January 2019–February 2020). A rise in metaldehyde concentrations was observed at all monitoring points, to varying extents, in the months of seasonal metaldehyde applications. The highest increases in metaldehyde concentrations (up to 0.05 µg L–1) across the catchment were observed in the autumn months and in December. These findings reinforce the mobile nature of the pesticide, with surface and field drain runoff likely to be the predominant mode of transfer to surface waters. The scale of individual sources of metaldehyde influx to the Ardleigh surface storage reservoir in the catchment showed that the highest contribution to the total flux to the reservoir was from water transferred from the adjacent River Colne catchment. Atmospheric deposition of metaldehyde followed a similar seasonal pattern to that observed in metaldehyde levels in surface water and field drain runoff, and in certain months accounted for a higher input than influx from surface runoff (May, August–October 2019). Monthly values of metaldehyde mass in the reservoir ranged from 27.7 to 47.4 g. An increase in mass was associated with elevated levels of flux from individual sources. Relatively stable levels of metaldehyde total mass in the reservoir are probably due to the aqueous solubility and decreased degradation rates of metaldehyde in the aquatic environment.

Wheat Crop under Waterlogging: Potential Soil and Plant Effects.

Inundation, excessive precipitation, or inadequate field drainage can cause waterlogging of cultivated land. It is anticipated that climate change will increase the frequency, intensity, and unpredictability of flooding events. This stress affects 10-15 million hectares of wheat every year, resulting in 20-50% yield losses. Since this crop greatly sustains a population's food demands, providing ca. 20% of the world's energy and protein diets requirements, it is crucial to understand changes in soil and plant physiology under excess water conditions. Variations in redox potential, pH, nutrient availability, and electrical conductivity of waterlogged soil will be addressed, as well as their impacts in major plant responses, such as root system and plant development. Waterlogging effects at the leaf level will also be addressed, with a particular focus on gas exchanges, photosynthetic pigments, soluble sugars, membrane integrity, lipids, and oxidative stress.

Adsorption kinetics investigation of surfactant molecules at the short-chain alkane-water interface

Foam drainage technology based on surfactants is considered the most promising measure to solve liquid accumulation in natural gas wells and gathering pipelines. However, the presence of multiple alkane components in condensate and natural gas will affect the properties of aqueous foam containing surfactants, which greatly limits the application of this technology. To clarify the mechanisms of different condensate oil and natural gas components on foam properties, the interface characteristics of different alkane-surfactant-water systems were systematically analyzed from thermodynamics and kinetics by molecular dynamics simulation and experimental methods. The results show that the interfacial adsorption of alkanes and the interaction between alkanes and surfactants are the main factors affecting the surface tension and stability of interfacial films of different systems. This study has guiding significance and reference value for foam drainage in oil and gas fields.

PROTECTION OF TERRITORIES FROM WATERLOGGING IN THE ZONE OF THE NORTH CRIMEAN CANAL OF KHERSON REGION AND WAYS TO IMPROVE IT

The system of protecting territories from the harmful effects of water using vertical drainage in the zone of the North Crimean Canal of the Kherson region was considered and the proposals for its improvement by creating additional horizontal drainage systems with gravity drainage were substantiated. Field drainage studies were carried out at 8 research and production sites with a total area of 4763 hectares and a term of operation of 48-55 years and more. The conducted studies included surveying the drainage in the areas, measuring the drainage flow and the depth of groundwater levels, and determining work efficiency. The research covered the settlements: Chornyanka, Nova Mayachka, Stara Mayachka, Podo-Kalynivka, Tarasivka, Velyki Kopani, Kalanchak, and Skadovsk, for the protection of which 119 water intake wells with a depth of 26-70 m were installed. It is shown that vertical drainage is effective during the whole operation and periods of selective work when the groundwater levels were at depths of 2-3 m and 1-2 m, respectively. To ensure reliable protection of territories from waterlogging and flooding in current conditions due to the impossibility and economic impracticability of restoring the operation of all existing vertical drainage wells, it is proposed to supplement the existing protection systems based on it with systems of closed horizontal drainage of the gravity type with low-sloping and non-sloping drainage. The area of additional horizontal drainage is about 40 thousand hectares, the estimated length of the collector and drainage network is 456 km, and the depth of laying drains and collectors is 2,5-11,0 m.

Assessing the impact of climate change on Combined Sewer Overflows based on small time step future rainfall timeseries and long-term continuous sewer network modelling

The evolution of the climate in the future will probably lead to an increase in extreme rainfall events, particularly in the Mediterranean regions. This change in rainfall patterns will have impacts on combined sewer systems operation with a possible increase of spilled flows, leading to an increase of untreated water volumes released to the receiving water. Due to the impact of overflows on the water cycle, local authorities managing combined sewer systems are wondering about the extent of these changes and the possibility of taking it into account in stormwater management structure design. To do this, rainfall data with a fine time step are required to better master the shape of the hyetographs that are crucial to get a relevant rainfall/runoff relationship in an urban environment. However, there are currently no simulations of future rainfall series available at a time step compatible with the needs in urban drainage field. In this work, future rainfall time series with a fine time step are elaborated with the aim to be used in urban hydrology. The proposed approach is based on simulations results from five regional climate models in the framework of the Euro-Cordex program. It consists in a spatial downscaling step followed by a temporal disaggregation. The rainfall time series obtained are then used as input for a calibrated and validated hydrological model to investigate the evolution of annual CSO volumes and frequencies by 2100. The results show an increase of annual spilled volumes between 13% and 52% according to the considered climate model. This increase will most likely be a problem regarding compliance of sewer networks in line with the water framework directive, particularly the current French regulations. No clear trends were observed on the CSO frequencies. If there is a consensus for all the carried-out simulations to conclude that the CSO volumes will increase, we must remember that actual regional climate models suffer from limited spatial and temporal resolution and don't explicitly solve convection processes. Due to this point uncertainty concerning the evolution rate remains important particularly for intense rainfall episodes. New generations of climate models are needed to accurately predict intense episodes.

Earthworm distribution around tile drainage in agricultural fields of southwest Quebec, Canada

Tile drainage is installed in agricultural fields to remove excess soil moisture to allow earlier planting of spring crops. Water moving from soil into tile drainage lines will potentially create a moist environment for earthworms. This study investigated how earthworms were distributed around tile lines, and how their abundance was affected by moisture in field crops on sandy and clayey soils. Earthworm abundance and soil moisture were similar above and between tile lines. Earthworm biomass was low in dry soils, peaked at 41 g moisture 100 g−1, and declined in wetter soils, which affects the earthworm activity in agricultural fields.

Leaching and geochemical evaluation of oxyanion partitioning within an active coal ash management unit

Field monitoring combined with laboratory leaching characterization and geochemical speciation modeling were used to identify important geochemical parameters and controlling mechanisms for leaching of oxyanions from coal ash in a disposal site. The site consisted of dry stacked ash on top of a former surface impoundment. Constituents leached from the dry stacked ash served as sources for the soluble fractions of constituents in underlying impoundment ash. Weathering of field ash was evidenced by the identification of calcite and ettringite. Porewater concentrations of As, B, and V in the field pH range (9–11) and liquid-to-solid ratio (L/S) condition (∼0.6 L/kg-dry) were primarily controlled by Ca-bearing precipitates (Ca-arsenate, B-substituted carbonate solid solution, Ca-vanadate, and V-substituted ettringite solid solution). The leachable fraction of Mo as a function of pH was limited by the available content in the solid, with aqueous concentrations of Mo being a function of L/S. Leaching behavior of Cr and Se was sensitive to the redox changes (from suboxic to oxic conditions) during field ash collection and laboratory leaching tests, including oxidative dissolution of insoluble Cr(III)-oxides and conversion of Se(0) in the solid to dissolved Se(IV)/Se(VI). Oxidation resulted in increased Cr concentrations from < 0.00005 (in porewater) to 0.001–0.1 mg/L (in laboratory eluates). The identified geochemical parameters and leaching-controlling mechanisms provide the bases for understanding and estimating the partitioning of oxyanions in other disposal sites with alkaline and suboxic conditions. This case study also provides a typical example of laboratory test results interpretation and field leaching behavior estimation for other studies.

Inverse estimation of hydraulic parameters of soils with rock fragments

The application of inverse modeling to determine the hydraulic properties of layered soils with rock fragments (RF > 2 mm) is associated with complex challenges such as selecting suitable hydraulic functions and defining a strategy to optimize many parameters. These two issues were addressed in this study by performing field drainage experiments in layered soil profiles (three layers) with different particle size distributions and different percentages of RF. Water contents (θ) and pressure heads (h) were monitored at different soil depths during drainage experiments (h ≥ −200 cm). Data of θ and h for a drier range (h < −5000 cm) were determined with a dew point potentiometer on disturbed soil samples. The unimodal and bimodal van Genuchten-Mualem functions were evaluated, and their parameters were optimized using the Hydrus-1D “Inverse solution”. The RETC curve fitting software was used to estimate the second set of parameters of the bimodal function. The parameters for the uni- and bimodal models (15 and 27 parameters, respectively) were repeatedly optimized by fixing some parameters while estimating others. The unimodal van Genuchten-Mualem function provided a satisfactory fit of θ and h measurements only when either drainage or dew point potentiometer measurements were used. On the other hand, the bimodal van Genuchten-Mualem function provided a satisfactory fit of θ and h measurements when both sets of data (drainage and dew point potentiometer measurements) were used simultaneously. Furthermore, the optimized parameters were physically consistent except for a few high saturated hydraulic conductivity values. Therefore, bimodal functions should be considered to represent the hydraulic properties of soils with RF. The problem of many calibrated parameters when using bimodal functions can be managed using sequential optimization, which allowed us to estimate 27 parameters for layered soils with RF successfully.

Synergistic improvement of nitrogen and phosphorus removal in constructed wetlands by the addition of solid iron substrates and ferrous irons

Sanjiang Plain is intensively used for rice production, and ditch drainage diffuse pollution prevention is crucial. Groundwater, rich in Fe ions, is the main source of irrigation water in this region. In this study, pyrite and zero-valent iron (ZVI) (sponge iron and iron scraps) were used as substrates to identify the synergistic influence of exogenous Fe2+addition and solid iron substrates on pollutant removal in constructed wetlands. Based on the results, iron substrates hardly improved the ammonia removal, mainly because of the physical structure and oxidation activity. At a hydraulic retention time longer than 8 h, the pollution removal efficiency in the zero-valent iron (ZVI) substrate treatment increased significantly, and the removal of nitrate (NO3−-N) and total phosphorus (TP) in the iron scrap substrate treatment reached about 60% and 70%, respectively. The high-throughput sequencing results showed a significant increase in the abundance of microorganisms involved in denitrification and phosphate accumulation in biofilms on ZVI substrates. The highest diversities of such microorganisms in biofilms on iron scraps were found for denitrifying bacteria (Pseudomonas), nitrate-reducing Fe (II)-oxidizing bacteria (Acidovorax), and Dechloromonas with autotrophic denitrification and phosphate accumulation, with a 43% cumulative abundance. Dechloromonas dominated in the iron sponge substrate treatment. The highest relative abundance of Acidovorax was found in the mixed iron substrate (pyrite, sponge iron, and iron scraps) treatment. The addition of ZVI substrate significantly improved the removal of NO3−-N and TP and reduced the hydraulic retention time through the continuous release of Fe2+ and the promotion of microbial growth. When designing constructed wetlands for treating paddy field drainage, the appropriate addition of iron scrap substrates is recommended to enhance the pollutant removal efficiency and shock load resistance of CWs.

Effect of alfalfa on subsurface (tile) nitrogen and phosphorus loss in Ohio, USA.

Growing annual crops such as corn (Zea mays L.) can lead to considerable nutrient losses through subsurface drainage in agricultural fields, posing a serious threat to surface water quality in the midwestern United States. Perennial crops have the potential to reduce these nutrient losses. However, more comprehensive data are needed on the nutrient loss effect of perennial crops. We examined the effect of alfalfa (Medicago sativa L.) on nitrate-nitrogen (NO3 - -N), total nitrogen (TN), dissolved reactive phosphorus (DRP), and total phosphorus (TP) in subsurface drainage using a before-after-control-impact (BACI) experimental design with one control field (with annual crops) and one impact field (with alfalfa) each on two farms (Sites A and B) located in northwestern Ohio. The "Before" period (prior to planting alfalfa at the impact field) extended for 4 yr (2013-2017) at Site A and 6 yr (2011-2017) at Site B; the "After" period extended for an additional 2 yr at both sites. Reductions in the mean monthly discharge and loads of NO3 - -N, TN, DRP, and TP were significant at Site A, whereas the only significant change at site B was a reduction in the mean monthly TP load. Significant reductions in NO3 - -N loads were observed during spring and winter at Site A. In addition, alfalfa reduced the variability of discharge and nutrient loads through subsurface drainage at both sites. Our findings suggest that introducing alfalfa into annual crop rotations has the potential to reduce subsurface nutrient loads and increase the resiliency of agricultural systems.

The Investigation of Artificial Wetland Systems for the Improvement of Agricultural Drainage Water

Harmful substances in the wastewater negatively affect the ecological balance by reducing the dissolved oxygen concentration. High phosphorus and nitrogen compounds discharged into surface water resources may cause to eutrophication, due to increased algal growth. In this study, Elodea densa (Egeria), Lemna minor (Duckweed), Micranthemum micranthemoides (Micra), Pistia (Water Lettuce), Ceratophyllum demersum (Foxtail) plants were investigated for the removal of nitrate and ammonium from rice field drainage water. Synthetic drainage water was prepared to rely on the literature and real rice field drainage water composition from the Samsun Bafra region. Artificial wetland studies were carried out as individual systems in order to understand the treatment ability of each plant and as a combined system in batch and continuous flow mode. pH, electrical conductivity, dissolved oxygen, nitrate, and ammonium values were measured periodically. Results of the individual plant wetland system represented that the wetland plant Elodea densa revealed the highest nitrate removal efficiency (77%) at the end of 1 day, followed by Pistia (76%). It was observed that the treatment efficiency increased with increasing hydraulic retention time. In the combined system, the nitrate removal efficiency was 40%, while the ammonium removal efficiency was 51% at the end of the first day. It was concluded that the wetland plants successfully reduced the ammonium and nitrate content of the drainage water and showed resistance to the drainage water with high salinity. In the wetland experiments carried out under continuous flow mode, ammonium was reduced from 0.80 mg/L to 0.10 mg/L, while nitrate was reduced from 1.90 mg/L to 1.40 mg/L, yielding approximately 90% and 30% at the end of the 16th day. Studies have in general revealed the importance of plant type as well as residence time.

"다중시기 항공영상을 활용한 내륙습지 경계 설정에 관한 연구 - 장구메기습지를 대상으로 -"

This study analyzed the changes of the Jang-gumegi wetland using multi-temporal aerial images, and proposed an objective method of delineating wetland boundaries. The result of the study indicated that the Jang-gumegi wetland were formed in paddy fields in the early 1900’s, and the number of households and paddy area continued to increase by the government’s 5-year plan for agricultural production enhancement and the baby boom thereafter. On the other hand, the study area gave up on agricultural production when the number of households decreased due to migration from rural to urban area after the 1980’s, and the fields have been abandoned since then. Meanwhile, the wetland boundaries were re-detected based on the location information by GPS and soil depth data and sediment samples were updated in the Jang-gumegi wetland. The soil depth between the regions was proportionated to the period of paddy cultivation, and the grain size of the sediment consisted mostly of clay, silt and partially sandy particles. This reflected poor drainage of paddy fields, and it indicated that the sediment supplied from the slope after fallow was deposited along a gentle slope. The derived result is expected to serve as a guideline for the establishment of preservation and management measures for abandoned paddy wetlands and a better methodology for wetland boundary settings.

Characterizing Antimicrobial Resistance in Clinically Relevant Bacteria Isolated at the Human/Animal/Environment Interface Using Whole-Genome Sequencing in Austria.

Antimicrobial resistance (AMR) is a public health issue attributed to the misuse of antibiotics in human and veterinary medicine. Since AMR surveillance requires a One Health approach, we sampled nine interconnected compartments at a hydrological open-air lab (HOAL) in Austria to obtain six bacterial species included in the WHO priority list of antibiotic-resistant bacteria (ARB). Whole genome sequencing-based typing included core genome multilocus sequence typing (cgMLST). Genetic and phenotypic characterization of AMR was performed for all isolates. Eighty-nine clinically-relevant bacteria were obtained from eight compartments including 49 E. coli, 27 E. faecalis, 7 K. pneumoniae and 6 E. faecium. Clusters of isolates from the same species obtained in different sample collection dates were detected. Of the isolates, 29.2% were resistant to at least one antimicrobial. E. coli and E. faecalis isolates from different compartments had acquired antimicrobial resistance genes (ARGs) associated with veterinary drugs such as aminoglycosides and tetracyclines, some of which were carried in conjugative and mobilizable plasmids. Three multidrug resistant (MDR) E. coli isolates were found in samples from field drainage and wastewater. Early detection of ARGs and ARB in natural and farm-related environments can identify hotspots of AMR and help prevent its emergence and dissemination along the food/feed chain.

Farmer adoption and intensity of use of extreme weather adaptation and mitigation strategies: evidence from a sample of Missouri farmers

Climate change and its associated weather extremes pose a threat to agriculture. To slow down climate change and reduce its associated risks, governments around the world are currently developing policies to encourage farmers to engage in adaptation and mitigation efforts. The aim of this study is to assess the adoption and intensity of use of extreme weather adaptation and mitigation strategies among a sample of Missouri farmers and to identify the factors that influence adaptation and mitigation behavior. Of particular interest is the influence of the 2019 Missouri River flooding on adaptation and mitigation efforts. An econometric hurdle model that separates the decision on whether to adopt adaptation/mitigation strategies from the decision on how many strategies to employ was used to achieve the study’s purpose. Improving field drainage or soil water retention capacity for potential flooding was found to be by far the most used adaptation. The most used mitigations were increasing use of minimum tillage, managing fertilizer, and planting cover crops. Types of crops grown, farm income, and opinions on extreme weather events were the most important determinants of both adaptation and mitigation decision. Direct experience with the 2019 Missouri River floods is found to only influence adaptation decision. Adaptation and mitigation intensity were found to be strongly influenced by opinions on government support for adaptation and CRP involvement, respectively. Directions for policy and outreach that can promote adaptation and mitigation efforts among farmers are discussed.

Non-contact detection of degradation of in-service steel sheet piles due to buckling phenomena by using digital image analysis with Hough transform

Steel sheet pile materials are primarily used for canal structure construction for irrigation and drainage of agricultural fields in Japan. Recently, accelerated corrosion of steel materials and buckling phenomena in pitting corrosion parts have been detected in in-service steel sheet pile canals. In this study, we focus on the buckling phenomenon of in-service steel sheet pile canals, which is detected by non-contact monitoring using digital image analysis. The buckling phenomenon index is evaluated as the inclination angle of the steel sheet pile due to deformation. As a digital image analysis, Hough transform is applied, which is a figure detection method in digital images, to detect a straight line that describes the distance and angle parameters. The angle parameter corresponds to the inclination angle index of in-service steel sheet pile with a buckling phenomenon. As a result, the maximum difference between the analyzed angles by Hough transform and the measured angles is evaluated as 0.9° after the image rotation correction. The relation of the analyzed angles by Hough transform and the measured angles of the buckling phenomenon is correlated. Therefore, the degradation of steel sheet pile canals is quantitatively evaluated by using digital image analysis with unmanned aerial vehicle monitoring. This study’s significance is non-contact and simple measurement by using a digital image which can reduce a working time and perform quick diagnosis in extensive areas.

Finite Element Model to Simulate Two-Phase Fluid Flow in Naturally Fractured Oil Reservoirs: Part I.

Naturally fractured reservoirs host more than 20% of the world’s total oil and gas reserves. To produce from such reservoirs efficiently, a good understanding of the reservoir behavior at various conditions is essential. This allows us to predict the reservoir performance in advance and assess its economic feasibility. However, the production from such reservoirs is challenging due to (a) uncertainty associated with the fracture map, (b) complex physics phenomena of fluid and rock interaction, and (c) lack of comprehensive knowledge of the extent, orientation, and permeability sensitivity of the fracture network. This paper addresses the abovementioned challenges by presenting a three-dimenisonal (3-D) two-phase fluid flow model in a poroelastic environment. The model is based on a hybrid methodology by combining single continuum and discrete fracture network approaches. Also, the capillary pressure effect, saturation, and relative permeability variations are considered. A mathematical formulation for three-dimensional, two immiscible fluid flows including rock deformation for the fracture network and the rock matrix is presented. A standard Galerkin-based finite element method is applied to discretize the poroelastic governing equations in space and time. The characteristic Galerkin discretization method is used to stabilize the solution of the convection equation in a finite element approach. The 3-D model is validated against IMEX commercial software and finite element package to test its robustness. The results show that the developed model has the ability to predict the two-phase flow behavior precisely, which can be used to assess the production performance of naturally fractured reservoirs. Numerical results of fluid flow profiles for single and multiple fractures with different orientations that match experimental oil drainage tests and field case studies are presented that proves the reliability of the developed multiphase flow model. Results of simulated well production data show an excellent match with the field production data.

PEMBUATAN CETAKAN V-DITCH PRACETAK BETON RINGAN DI DESA SAMUTI RAYEUK KECAMATAN GANDAPURA KABUPATEN BIREUEN

Drainage or exhaust duct is one of the basic facilities designed as a system to meet community needs and is an important component in urban infrastructure planning. On the other hand, the channel can also be interpreted as an effort to control the quality of groundwater in relation to salinity, where drainage is one way of removing unwanted excess water in an area. From an agricultural point of view, drainage is also useful as a waterway that will flow into the community's rice fields, so it is an important infrastructure component in the process of planting rice in the fields. Samuti Rayeuk Village, Gandapura District, is one of the villages with land use conditions that are dominated by agriculture with the type of rice field utilization and community work being farmers, one of the important infrastructures for the concern of the local community is the unavailability of drainage in the community's rice fields. Samuti Rayeuk is a village assisted by the Faculty of Engineering, Almuslim University, which is the location for the Training of Making Lightweight Precast V-Ditch formwork. In some developed countries such as Japan, the use of precast has become the construction standard for drainage. Standards have been developed to ensure product quality and construction. In this community service activity, the Lecturers act as companions and also as instructors who assist in the implementation of making precast V-Ditch formwork starting from the selection of materials to be used, assembling, and finishing to completion. With this training, it is expected that it can increase community innovation for making channels for rice fields so as to improve the economy of the people of Samuti Rayeuk Village, Gandapura District and its surroundings.

Field leaching study - Inverse estimation of degradation and sorption parameters for a mobile soil metabolite and its pesticide parent

Pesticide concentration measurements from field studies under real-world conditions can improve the derivation of more representative modelling input parameters for the exposure assessment of agrochemicals in the authorization process of plant protection products. The pertinent guidance documents foresee the application of inverse modelling approaches in combination with environmental fate and transport models to estimate e.g., soil dissipation rates that are solely based on microbial degradation and are not lumped with contributions from other dissipation processes such as leaching, plant uptake, volatilization and photodegradation. Field leaching studies can be used to estimate both degradation and sorption of chemicals in the soil matrix. In this study, inverse modelling of environmental fate parameters is presented based on solute concentrations from a field leaching study sampling pore water from five different depths down to 1.5 m. The leaching model PEARL and the universal optimization tool PEST were coupled, and sorption and degradation of the fungicide fluopicolide and its soil metabolite BAM (2,6-dichlorobenzamide) were quantified. Soil degradation half-lives were not different from results obtained in regular field degradation studies sampling residues in the total soil matrix (236 d vs. 158 d for fluopicolide and 53 d vs. 45 d for BAM); whereas a sorption increase with time (time-dependent sorption) was observed for the parent compound. This work aims at pointing out the feasibility to include field leaching studies with measurements at different soil depths in regulatory exposure assessment, since a statistically significant derivation of degradation and sorption parameters is presented, along with low uncertainties in the estimated parameter values of ±10%.

Effect of the Matrix Dam in the Paddy Field Drainage Ditch on Water Purification Based on the Physical Model Test

(1) Setting a matrix dam in the paddy field drainage ditch has been recognized as an effective method to lower the velocity of water discharged from a paddy field in the drainage ditch, which can improve the purification efficiency of the drainage ditch for nitrogen and phosphorus pollutants, but the specific placement and thickness of the matrix dam have not been supported due to the insufficient research results. (2) Three thicknesses of the matrix dam were set in three locations of the physical model of the drainage ditch. By measuring the flow rate and water level in different sections, the optimal layout location and thickness of the matrix dam were determined. (3) When the matrix dam was located in section 1-1, the flow rate from sections A-A to C1-C1 was reduced by 0.159 m/s; when the matrix dam was located in section 2-2, the flow rate was reduced by 0.331 m/s; when the matrix dam was located in section 3-3, the flow rate was reduced by 0.360 m/s. (4) We concluded that the optimal design position of the matrix dam was section 3-3, 9.2 m from the entrance of the water flume, and the optimal design thickness was 0.3 m.