Vegetative Filter Research Articles

Risk mitigation measures for pesticide runoff: How effective are they?

One of the most important sources of pesticide pollution of surface waters is runoff and erosion from agricultural fields after rainfall. This study analyses the efficacy of different risk mitigation measures to reduce pesticide runoff and erosion inputs into surface waters from arable land excluding rice fields. Three groups of risk mitigation measures were quantitatively analyzed: vegetative filter strips, micro-dams in row crops and soil conservation measures. Their effectiveness was evaluated based on a meta-analysis of available experimental data using statistical methods such as classification and regression trees, and exploratory data analysis. Results confirmed the effectiveness of vegetative filter strips and micro-dams. Contrary to common assumption, the width of vegetative filter strips alone is not sufficient to predict their effectiveness. The effectiveness of soil conservation measures (especially mulch-tillage) varied widely. This was in part due to the heterogeneity of the available experimental data, probably resulting from the inconsistent implementation and the inadequate definitions of these measures. Both vegetative filter strips and micro-dams are effective and suitable, and can therefore be recommended for quantitative assessment of environmental pesticide exposure in surface waters. However, the processes of infiltration and sedimentation in vegetative filter strips should be simulated with a mechanistic model like Vegetative Filter Strip Modeling System, VFSMOD. The reduction effect of micro-dams can be modelled by reducing the runoff curve number, e.g., in the pesticide root zone model, PRZM. Soil conservation measures are in principle promising, but further well-documented data are needed to determine under which conditions they are effective. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Evaluation of contaminants of emerging concern attenuation through a vegetation filter managed using different operating conditions

In wastewater treatment using Vegetation Filters (VFs), natural processes reduce contaminants present in water although some of them can reach the environment. In this study, 39 contaminants of emerging concern (CECs) are evaluated in a pilot VF under different operating conditions during almost four years. The use of woodchip amendments and the change from surface irrigation through furrows to drip irrigation (and from weekly to daily water application) provide CEC concentration reductions in the water infiltrating through the vadose zone. Biodegradation is the main process taking place and has been favoured mainly by woodchip soil amendments and the increased residence. Median attenuation percentages of the CECs most frequently detected with highest concentrations in applied wastewater vary between 52% and 100% at the end of the study (at 45 cm depth). Among targeted CECs, caffeine, and its transformation product paraxanthine are the most attenuated. Flecainide and venlafaxine show a persistent behaviour. However, their leaching concentrations are very low (< 31 ng/L). Concerning the underlying aquifer, the groundwater quality in terms of CEC concentrations is conditioned by the surrounding area rather than the operation of the VF. Levels in groundwater are always below those in wastewater and infiltrating water.

Suitability of Salicaceae genotypes to produce biomass using industrial wastewater

Water circularity is a challenge which must be met to guarantee the sustainability of this resource. Woody biomass is another resource of interest for the bioeconomy, which has multiple uses and acts as a carbon sink. Combining both aspects involves establishing wastewater irrigated plantations, the so-called Vegetation Filters. The aim in this research was to contribute towards assessing the suitability of different Salicaceae genotypes for enhancing the efficiency of these simultaneous processes. Twenty-three genotypes of different species and hybrids of the genera Populus and Salix were irrigated using brewery wastewater under controlled conditions (in a greenhouse using hydroponic cultivation or in pots with substrate) and in the field. Although the application of wastewater reduced the overall production, relevant differences among the genotypes were detected. Growth, physiological activity and nitrogen and electric conductivity (EC) attenuation efficiency provided good criteria for selection, although given the interaction with site conditions it is essential that plant material is selected based on its adaptation to the environment. The poplar hybrids ‘2000 Verde’ and ‘I-214’ showed the highest rates of net photosynthesis and transpiration, with high percentages of N removal and moderate biomass production, these two initially being considered of interest for the purposes outlined above. The ‘AF34’ genotype showed the highest production in the field, followed by the ‘Levante’ willow hybrid. The white poplar ‘PO-10-10-20’, which presented moderate production in the field, is also of interest due to its autochthony, which can be advantageous in certain environments.

Spatial Variability of Best Management Practices Effectiveness on Water Quality within the Yazoo River Watershed

Best management practices (BMPs) are management operations that reduce pollution and improve water quality. This study assessed the spatial variability of BMPs effectiveness within the Yazoo River Watershed (YRW) using Soil and Water Assessment Tool (SWAT). Two field-scale watersheds, Merigold Watershed (MW) from the Delta and Skuna River Watershed (SRW) in the Bluff Hills, were selected within the YRW. The SWAT model was calibrated and validated for monthly streamflow, and daily total suspended solids (TSS), total nitrogen (TN), and total phosphorus (TP). Monthly evaluated streamflow Nash–Sutcliffe efficiency indices were in the range from 0.60 to 0.86; daily evaluated TSS indices were in the range from 0.11 to 0.15, TN from 0.11 to 0.12, and TP from 0.05 to 0.26 during model calibration and validation periods. BMPs were implemented in MW and SRW to analyze the spatial variability effect on water quality. Cover crops (CC), vegetative filter strips (VFS), and a combination of VFS and CC were applied as BMP scenarios. Overall, a larger reduction in streamflow was about 15%, sediment about 26%, and nutrient loads, which was about 39% (TN) and 50% (TP), was determined in the MW, whereas in the large watershed (YRW) the reductions in streamflow, sediment, TN, and TP loads were about 4%, 5%, 30%, and 24%, respectively. Therefore, the novelty of this research is to compare the efficiency of a BMP in pollutant reduction at two different geographic scales. The results from this study could help farmers, scientific researchers, precision management planning, and implementing agencies select appropriate BMP for field-scale water resources management in minimizing sediment and nutrient quantities in surface water.

A trapping capacity constraint model for sediment transport in vegetative filter strips (VFS) on sloping surfaces

AbstractMost current modelling practices for sediment trapping in vegetative filter strips (VFS) assumed a constant sediment trapping efficiency of VFS, while, in practice, it was found to decrease greatly with the increasing trapped sediment amount in VFS (decreasing sediment trapping capacity of VFS). To account for this impact, a widely used VFS sediment transport module was modified to consider the changing sediment trapping capacity of VFS, which was expressed by a power‐law relationship with the inflow discharge, sediment concentration, slope gradient, and antecedent deposition amount. An integrated model that coupled a slope infiltration‐runoff module and the modified sediment transport module was then developed to simulate hydrology and suspended sediment transport in VFS on sloping surface. The model is calibrated and validated by 18 VFS experiments with different inflow, sediment, and slope conditions from Luo et al. (Science of the Total Environment, 725, 138361, 2020). Good agreements between observed and simulated runoff and sediment transport processes were found for nearly all cases. Due to the impact of changing sediment trapping capacity of VFS, the trapped sediment amount and the sediment transport rate of outflow varies greatly in space and time. With the increase of inflow discharge, sediment concentration, and slope gradient, the overall sediment trapping efficiency of VFS tends to decrease greatly and then remains almost unchanged. The comparison between proposed model and original physically based model shows that neglecting the impacts of changing sediment trapping capacity of VFS would lead to a constant and overly large sediment trapping efficiency of VFS, especially on steep slopes. Moreover, comparing with the empirical expression, the model with well‐founded theory can provide higher fidelity and more detailed results. Thus, the modelling framework is expected to provide a more effective approach for VFS assessment and maintenance in local or watershed scale.

Effectiveness of vegetative filter strips for sediment control from steep construction landscapes

Sediment carried off-site by runoff poses a significant water quality threat to receiving water bodies. Best management practices (BMPs) are commonly applied to reduce the impact of runoff on surface water quality. Vegetative filter strips (VFS) are low-cost BMP that often provide significant runoff mitigation in agricultural and urban settings with moderate slopes (<15 %). However, the runoff mitigation effectiveness of VFS under steep, short slopes like those typical of roadway construction is unknown. This study aimed to systematically investigate the efficacy of short (<5 m) and sparse VFS on steep slopes (>15 %). Field experiments were conducted on a steep hillslope (3H:1V, 33.3 %) where three VFS lengths (1.52 m, 3.05 m, and 4.57 m) were monitored during runoff events (10-y, 6-hr) to measure runoff delivery ratio (RDR) and sediment delivery ratio (SDR). The experimental results showed reductions of 60–98 % in runoff and 73–98 % in sediment, confirming the potential efficiency of this BMP in high-sloped conditions like a roadway construction site under certain conditions. The Vegetative Filter Strips Modeling System (VFSMOD) was successfully tested against the observed field values (NSE = 0.98 and 0.89 for RDR and SDR, respectively) and used to explore more scenarios. A wide range of roadway construction settings (VFS size, slope, vegetation density) was investigated with VFSMOD, and two simplified statistical regression equations and nomographs were developed to quantify RDR and SDR based on the simulation results. The proposed equations simplify the complexity of VFS design and can be readily generalized to other locations (rainfall/runoff, soil, vegetation) after reparametrizing coefficients in regression equations based on VFSMOD simulations to obtain new nomographs as a design aid to determine the minimum buffer length for a particular site.

Prairie strips remove swine manure associated antimicrobial resistance genes and bacteria from runoff

Runoff from manured agricultural fields can transport antimicrobial resistance (AMR) contaminants, including genes and bacteria, to downstream ecosystems. Previous work has identified the integration of Conservation Practice 43 (CP 43) prairie strips – a type of vegetative filter strip – within and at the edge of agricultural fields as a potential management solution to reduce the movement of these, and other, manure pollutants, while offering an opportunity for biodiversity conservation. The objectives of this study were to 1) quantify the ability of prairie strips to reduce the presence of antimicrobial resistance genes from manure laden runoff, and 2) characterize the impact of manure on prairie soil microbiomes over time. Simulated rainfall events were used to create artificial runoff on field plots with swine manure amendment and prairie strips as treatment factors. A suite of antibiotic resistance genes and mobile genetic elements were characterized in runoff samples collected during the rainfall simulation, while manure associated bacteria were characterized in soil samples collected over 153 days after the rainfall simulation. Prairie strips placed downslope from manured crop soil significantly reduced the cumulative abundance of resistance genes in both runoff water (p-value < 0.0001) and runoff sediment (p-value < 0.0001). Manure associated bacteria were transported both horizontally, from the manure amended crop soil into the prairie strip soil, and vertically, into the crop and prairie strip soil profiles. The specific manure associated gene tet(M) and the specific manure associated bacterial genus Clostridium sensu stricto 1 were highly enriched in manured runoff and soil, respectively, and could represent future targets of human health concern. Results from this study provide further support for the use of CP 43 prairie strips as a management practice to reduce the transport of manure associated resistance contaminants off agricultural fields.

Using color-only vegetation indexes to remove vegetation from otherwise mostly mono-material point clouds

Point clouds are now a standard way of describing objects in many engineering disciplines, whether they are man-made objects such as structures, buildings, or various types of structures. Commonly used methods of acquiring such data include ground, UAV, or even aerial photogrammetry, followed by terrestrial, UAV, and aerial scanning. After measurement (by the scanner) or calculation (from photogrammetry), the point cloud goes through extensive processing that essentially transforms the unordered mass of points into a usable data set. One of the important steps is removing points representing obstructing objects and features, including vegetation in particular. Here, many filtering methods based on different principles are available and suitable for application to different scenes. This paper presents a new method of filtering point clouds based on the visible spectrum color principle using vegetation indexes determined from RGB system colors only. Since each sensor has to some extent, an individual interpretation of the colors, it cannot be assumed to determine specific boundaries of what is and is no longer vegetation. Therefore, it was proposed to use means clustering to simplify the operator's work. The method was also designed in such a way that the entire evaluation could be implemented in the freely available CloudCompare software. The procedure was tested on three different sites with different terrain and vegetation characteristics showing, which demonstrated the applicability of this method to data where the color information (green) uniquely identifies vegetation. The selected vegetation filters ExG, ExR, ExB, and ExGr were tested, where ExG was the best. K-means clustering helps an operator to distinguish more easily between vegetation and the rest of the point cloud without compromising the quality of the result. The method is practically implementable using the freely downloadable and usable CloudCompare software.

MODELLING THE IMPACTS OF SELECTED WATERSHED MANAGEMENT STRATEGIES ON SEDIMENT REDUCTION UPSTREAM OF SHIRORO DAM, NIGERIA

This research utilized a regulated hydrological model, Soil and Water Assessment Tool (SWAT) interfaced with Geographical Information System (GIS), in studying the effectiveness of the chosen watershed management strategies on sediment reduction upstream of Shiroro dam, Nigeria. Selected management approaches were modelled while calibration and validation of the model were achieved using observed streamflow data. Findings indicated a good correlation during calibration and validation period. Application of reforestation, vegetative filter strips and stone bunds in the watershed reduces sediment production by 27 %, 39 %, and 15 % respectively. Thus, the sediment management scenarios depicted within this research are considerably sustainable and effective.

Untargeted metabolomic analysis to explore the impact of soil amendments in a non-conventional wastewater treatment

As non-conventional wastewater treatment, vegetation filters make the most of the natural attenuation processes that occur in soil to remove contaminants, while providing several environmental benefits. However, this practice may introduce contaminants of emerging concern (CECs) and their transformation products (TPs) into the environment. A potential improvement to the system was tested using column experiments containing soil (S) and soil amended with woodchips (SW) or biochar (SB) irrigated with synthetic wastewater that included 11 selected CECs. This study evaluated: i) known CECs attenuation and ii) unknown metabolites formation. Known CECs attenuation was assessed by total mass balance by considering both water and soil media. An untargeted metabolomic strategy was developed to assess the formation of unknown metabolites and to identify them in water samples. The results indicated that SB enhanced CECs attenuation and led to the formation of fewer metabolites. Sorption and biodegradation processes were favored by the bigger surface area of particles in SB column, especially for compounds with negative charges. Incorporating woodchips into soil shortened retention times in the column, which reduced attenuation phenomena and resulted in the formation of significantly more metabolites. Incomplete biodegradation reactions, fostered by shorter retention times in SW column could mainly explain these results.

Treatment of Landfill Leachate by Short-Rotation Willow Coppice Plantations in a Large-Scale Experiment in Eastern Canada

The treatment of leachate by vegetative filters composed of short-rotation willow coppice (SRWC) has been shown to be a cost-effective alternative to conventional and costly methods. However, few studies have considered the treatment capability of willow filters at a scale large enough to meet the industrial requirements of private landfill owners in North America. We report here on a field trial (0.5 ha) in which a willow plantation was irrigated with groundwater (D0) or aged leachate at two different loadings (D1 and D2, which was twice that of D1). Additionally, half of the D2-irrigated plots were amended with phosphorus (D2P). The system, which operated for 131 days, was highly efficient, causing the chemical oxygen demand concentration to drop significantly with the total removal of ammonia (seasonal average removal by a concentration of 99-100%). D2P efficacy was higher than that of D2, indicating that P increased the performance of the system. It also increased the willow biomass 2.5-fold compared to water irrigation. Leaf tissue analysis revealed significant differences in the concentrations of total nitrogen, boron, and zinc, according to the treatment applied, suggesting that the absorption capacity of willows was modified with leachate irrigation. These results indicate that the willow plantation can be effective for the treatment of landfill leachate in respect of environmental requirements.

Modelling sediment trapping in vegetative filter strips on steep slopes

AbstractThe slope effects on sediment trapping process in vegetative filter strips (VFS) are usually neglected in current modelling practices for VFS operation, which hamper the VFS design and performance evaluation, especially on steep slopes. To fill the knowledge gap, 12 laboratory experiments of sediment trapping in VFS were conducted with three different inflow discharge (80, 100, and 120 ml s−1) and four slope angles (5,10, 15, and 20°). The experimental results show that, on steep slopes (10, 15, and 20°), a part of trapped sediment particles in VFS can be eroded again and then dragged to the downstream as bed load, whilst they do not move on gentle slope (5°). To describe the complex processes, a simple and effective modelling framework was developed for sloped VFS by coupling the slope infiltration, runoff, and modified sediment transport model. The model was tested against the experimental results and good agreements between the modelled and observed results were found in both runoff and sediment transport processes for all cases. On steep slopes, the sediment trapping performance of VFS decreases significantly because the erosion of deposited sediment particles can account for more than 60% of the sediment load in the outflow. The slope effect on sediment trapping efficiency of VFS varies greatly with soil, VFS, and slope properties. The model was compared with previous sediment transport equation and found that both methods can satisfactorily predict the sediment trapping of VFS on gentle slopes, but previous sediment transport equation is likely to overestimate the sediment trapping efficiency in VFS on steep slopes. This model is expected to provide a more realistic and accurate method for predicting runoff and sediment reduction in VFS on sloping surfaces.

Modelling crop production, river low flow, and sediment load trade-offs under agroforestry land-use scenarios in Nyangores catchment, Kenya

The largest impact of land-use change on catchment hydrology can be linked to deforestation. This change, driven by exponential population growth, intensified food and industrial production, has resulted in alterations in river flow regimes such as high peaks, reduced base flows, and silt deposition. To reverse this trend more extensive management practices are becoming increasingly important, but can also lead to severe losses in agricultural production. Land-use optimization tools can help catchment managers to explore numerous land-use configurations for the evaluation of trade-offs amongst various uses. In this study, the Soil and water assessment tool (SWAT) model was coupled with a genetic algorithm to identify land-use/management configurations with minimal trade-offs between environmental objectives (reduced sediment load, increased stream low flow) and the crop yields of maize and soybean in Nyangores catchment (Kenya). During the land-use optimization, areas under conventional agriculture could either remain as they are or change to agroforestry or conservation agriculture (CA), where the latter was represented by introducing contour farming and vegetative filter strips. From the sets of the resulting Pareto-optimal solutions we selected mid-range solutions, representing a fair compromise among all objectives, for further analysis. We found that a combined measure implementation strategy (agroforestry on certain sites and conservation agriculture on other sites within the catchment) proved to be superior over single measure implementation strategies. On the catchment scale, a 3.6% change to forests combined with a 35% change to CA resulted in highly reduced sediment loads (−78%), increased low flow (+14%) and only slightly decreased crop yields (&amp;lt;4%). There was a tendency of the genetic algorithm to implement more extensive management practices in the upper part of the catchment while leaving conventional agriculture in the lower part. Our study shows that a spatially targeted implementation strategy for different conservation management practices can remarkably improve environmental sustainability with only marginal trade-offs in crop production at the catchment-level. Incentive policies such as payments for ecosystem services (PES), considering upstream and downstream stakeholders, could offer a practical way to effect these changes.

Influence of Vehicular Frequency on Air Quality of Delhi, India

Abstract Vehicular traffic has registered a phenomenal growth in the last few decades on Delhi roads, their increasing number is a cause of concern for city planners and administrators as they not only deteriorated the quality of environment but has also affected the human health. In this context, we studied the influence of traffic i.e., vehicular frequency on air quality of Delhi. Five sites were selected in four cardinal directions i.e., North, South, East, West and Centre for which data of air pollutants were already available in public domain (DPCC online website). Vehicular frequencies were recorded for Light Motor Vehicle (LMV) and Heavy Motor Vehicle (HMV) for both weekdays and weekends. Correlative analysis were carried out to study the relationship between vehicular frequency and air pollutants. The study showed, East of Delhi had the highest traffic load followed by North, West, South and Centre. We found statistically significant positive correlation between dust pollution, PM10 (r = 0.8) and PM2.5 (r = 0.6) with vehicular frequency while negative association with ozone (r = –0.5). A weak positive correlation was found with NOx (r = 0.2) while weak negative correlation with SO2 (r = –0.3). The study revealed that vehicular exhaust and their movement contribute in deteriorating the air quality of Delhi. Our findings suggest promotion of usage of public transport along with implementation of BS-VI stage vehicles and development of vegetation filters along the roads with native tree species.

Assessing the effectiveness of potential best management practices for science-informed decision support at the watershed scale: The case of the Mar Menor coastal lagoon, Spain

Coastal lagoons are ecosystems of high environmental importance but are quite vulnerable to human activities. The continuous inflow of pollutant loads can trigger negative impacts on the ecological status of these water bodies, which is contrary to the European Green Deal. One example is the Mar Menor coastal lagoon in Spain, which has experienced significant environmental degradation in recent years due to excessive external nutrient input, especially from non-point source (NPS) pollution. Mar Menor is one of the largest coastal lagoons of the Mediterranean region and a site of great ecological and socio-economic value. In this study, the highly anthropogenic and complex watershed of Mar Menor, known as Campo de Cartagena (1244 km2), was modelled with the Soil and Water Assessment Tool (SWAT) to analyse potential options for recovery of this unique system. The model was used to simulate several best management practices (BMP) proposed by recent Mar Menor regulations, such as vegetative filter strips, shoreline buffers, contour farming, removal of illegal agriculture, crop rotation management, waterway vegetation restoration, fertiliser management and greenhouse rainwater harvesting. Sixteen scenarios of individual and combined BMPs were analysed in this study. We found that, as individual measures, vegetative filter strips and contour farming were most effective in nutrient reduction: approximately 30 % for total nitrogen (TN) and 40 % for total phosphorus (TP). Moreover, waterway vegetation restoration showed the highest sediment (S) reduction at approximately 20 %. However, the combination of BMPs demonstrated clear synergistic effects, reducing S export by 38 %, TN by 67 %, and TP by 75 %. Selecting the most appropriate BMPs to be implemented at a watershed scale requires a holistic approach considering effectiveness in reducing NPS pollution loads and BMP implementation costs. Thus, we have demonstrated a way forward for enabling science-informed decision-making when choosing strategies to control NPS contamination at the watershed scale.

Dynamic prediction of effective runoff sediment particle size for improved assessment of erosion mitigation efficiency with vegetative filter strips

The most widely implemented mitigation measure to reduce transfer of surface runoff pesticides and other pollutants to surface water bodies are vegetative filter strips (VFS). The most commonly used dynamic model for quantifying the reduction by VFS of surface runoff, eroded sediment, pesticides and other pollutants is VFSMOD, which simulates reduction of total inflow (∆Q) and of incoming eroded sediment load (∆E) mechanistically during the rainfall-runoff event. These variables are subsequently used to calculate the reduction of pesticide load by the VFS (∆P). Since errors in ∆Q and ∆E propagate into ∆P, for strongly-sorbing compounds an accurate prediction of ∆E is crucial for a reliable prediction of ∆P. The most important incoming sediment characteristic for ∆E is the median particle diameter (d50). Current d50 estimation methods are simplistic, yielding fixed d50 based on soil properties and ignoring specific event characteristics and dynamics. We derive an improved dynamic d50 parameterization equation for use in regulatory VFS scenarios based on an extensive dataset of 93 d50 values and 17 candidate explanatory variables compiled from heterogeneous data sources and methods. The dataset was analysed first using machine learning techniques (Random Forest, Gradient Boosting) and Global Sensitivity Analysis (GSA) as a dimension reduction technique and to identify potential interactions between explanatory variables. Using the knowledge gained, a parsimonious multiple regression equation with 6 predictors was developed and thoroughly tested. Since three of the predictors are event-specific (eroded sediment yield, rainfall intensity and peak runoff rate), predicted d50 vary dynamically across event magnitudes and intensities. Incorporation of the improved d50 parameterization equation in higher-tier pesticide assessment tools with VFSMOD provides more realistic quantitative mitigation in regulatory US-EPA and EU FOCUS pesticide risk assessment frameworks. The equation is also readily applicable to other erosion management problems.

Methodology for preparing a reference sample in the air filter matrix

The proficiency tests are widely used to evaluate the analytical capacity of laboratories and also as part of the accreditation processes. The National Intercomparison Program is a Proficiency Test that uses radioactive reference materials in soil, vegetation, water and air filters. This work is a study of the choice of composition of radionuclides ideal to be used in the air filters to be produced by LNMRI as reference material for PNI. &#x0D; Five cocktails composed of different radionuclides chosen for their energies in the range of 30 to 2000 keV were prepared, each cocktail was distributed in three glass fiber air filters using a pantograph using the pycnometer technique, contaminating each filter with 19 (nineteen) drops, totaling fifteen (15) air filter samples, with the objective of homogeneous distribution of the droplets at the sites determined by the geometry chosen without the need for marking in the filters, in order to choose the best composition to be used in the preparation of reference material.

Colloid‐Pollutant Migration through Saturated Vegetative Filter Strips with Various Hydrodynamics Condition under Rainfall

AbstractFlow hydrodynamic condition impacts the deposition process on vegetation and removal of colloid and colloid‐associated contaminants in saturated vegetative filter strips (VFSs) under rainfall. A 9.6‐m‐long flume was constructed to investigate the retention of colloids through VFSs, with saturated soil and simulated rainfall. Colloidal filtration theory was applied to calculate the colloid deposition rate coefficient (kd) on vegetation surface. The result showed that removal efficiencies (η) of the single‐stem decreased, but colloid kd on the flume scale vegetation increased with increased Reynolds number (Re). Flume experiment found that the colloid retention rate in VFSs decreased as the Re increased. Since deposition on vegetation surface and diffusion into saturated soil are two main removal mechanisms, the discrepancy between kd and retention rate suggests that colloid diffusion into the soil was the dominant process of colloid removal in saturate VFSs. The research deepens the understanding of colloid transport mechanism in VFSs, and provides theoretical basis for the design of VFSs.

Wastewater-Fertigated Short-Rotation Coppice, a Combined Scheme of Wastewater Treatment and Biomass Production: A State-of-the-Art Review

Vegetated filters based on short-rotation coppice (SRC) can be used to treat various industrial and municipal wastewater while producing valuable biomass in an economical and sustainable way, showing potential in the field of pollution control and bio-based circular economy. This study provides an overview of the state of the art in wastewater-fertigated SRC systems (wfSRCs) worldwide. Different designs, wastewater sources, tree species and varieties, planting schemes, geographic locations, and climates for wfSRC implementation were identified after conducting a literature review. The performance review includes standard water quality parameters, BOD5, COD, nitrogen, phosphorous, and potassium, as well as the extent of pathogen and emergent contaminant removal and biomass production rates. Identified knowledge gaps and important factors to support the practical implementation of wfSRCs are highlighted. Europe leads the research of wfSRC, followed by North America and Australia. The available publications are mainly from developed countries (73%). The most applied and studied tree species in wfSRC systems are willows (32%), followed by eucalyptus (21%) and poplars (18%). Most of the reviewed studies used domestic wastewater (85%), followed by industrial wastewater (8%) and landfill leachate (7%). Most data show high BOD5 and COD removal efficiencies (80%). There are large differences in the documented total nitrogen and total phosphorus removal efficiencies (12%–99% and 40%–80%, respectively). Enhanced biomass growth in wfSRC systems due to wastewater fertigation was reported in all reviewed studies, and biomass production varied from 3.7 to 40 t DM/ha/yr. WfSRCs seem to have high potential as viable and cost-effective wastewater treatment alternatives to conventional treatment technologies.

Influence of Vegetation Filter Strip on Slope Runoff, Sediment Yield and Nutrient Loss

It is an important branch of erosion research to control soil erosion on eroded gullies and slopes by using vegetation filter strip. Several simulated rainfall experiments were carried out in soil tanks filled with loess sandy loam taken from a typical eroded gully area with less vegetation coverage in Yanghe hilly basin in Xuanhua District, Zhangjiakou City, Hebei Province. The soil and water conservation effects of two different vegetation setting modes were compared under the same vegetation strip width and different rainfall intensities and slopes. During the rainfall process, the changes of runoff and sediment yield and nutrient loss were not stable, but the same erosion index had similar variation trends under different combinations of rainfall intensity, slope and vegetation coverage. Multiple regression results showed that runoff and sediment production in eroded gully can be effectively reduced through vegetation filter strips, which are jointly affected by rainfall intensity and slope. There was no significant difference in the amount of runoff and sediment yield between the two vegetation setting modes. Rainfall intensity and slope gradient showed different strengths of impact on nutrient loss. Through cluster analysis, the results showed that the impacts of rainfall intensity, slope gradient and vegetation setting modes on soil and water loss on slope can be equal or offset. In general, setting vegetation filter strips can offset the effects of rainfall intensity and slope, but vegetation regulation of erosion was not obvious under extreme rainfall and steep slope conditions. What’s more, rainfall intensity had a dominant effect on erosion. The results in this research may provide reference for practical application of vegetation filter strips on eroded slopes.