Vegetative Filter Research Articles

Keeping Up with Phosphorus Dynamics: Overdue Conceptual Changes in Vegetative Filter Strip Research and Management

Vegetative filter strips (VFS) are best management practices with the primary aim of protecting surface waters from eutrophication resulting from excess nutrient inputs from agricultural sources. However, we argue that there is a substantial time and knowledge lag from the science underpinning VFS to policy and implementation. Focussing on phosphorus (P), we strive to introduce a holistic view on VFS that accounts for the whole functional soil volume, temporal and seasonal effects, the geospatial context, the climatic and physico-chemical basic conditions, and the intricate bio-geochemical processes that govern nutrient retention, transformation, and transport. Specifically, we suggest a step-wise approach to custom VFS designs that links and matches the incoming P from event to multi-annual timescales from the short- and mid-term processes of P retention in the effective soil volume and to the longer-term P retention and offtake coupled to the soil-vegetation system. An a priori assessment of the P export potential should be followed by bespoke VFS designs, in line with local conditions and socio-economic and ecological constraints. To cope with increasingly nutrient saturated or functionally insufficient VFS installed over the last decades, concepts and management strategies need to encompass the transition in understanding of VFS as simple nutrient containers to multifunctional buffer zones that have a complex inner life. We need to address these associated emerging challenges and integrate their implications more thoroughly into VFS research, monitoring, policy, and implementation than ever before. Only then we may get VFS that are effective, sustainable, and persistent.

Analytical method to monitor contaminants of emerging concern in water and soil samples from a non-conventional wastewater treatment system

Nonconventional wastewater treatments, such as vegetation filters (VFs), are propitious systems to attenuate contaminants of emerging concern (CECs) in small municipalities. The development of standardised multiresidue and multimatrix methods suitable for measuring a reliable number of CEC in environmental samples is crucial for monitoring infiltrating concentrations and for ensuring these systems’ treatment capacity. The objective of this study is to develop and validate an analytical method for the simultaneous determination of CECs, including transformation products (TPs), with diverse physico-chemical properties, in environmental samples. The optimised method is based on sample clean-up and preconcentration by solid-phase extraction (SPE), followed by liquid chromatography electrospray ionization tandem mass spectrometry (LC-MS/MS). The method is able to detect and quantify 40 target CECs, including pharmaceuticals of different classes (analgesics, antibiotics, antihypertensives, lipid regulators, anticonvulsants, antidepressants, antiarrhythmics, beta-blockers, amongst others), hormones and lifestyle products with good reproducibility (variations below 23%), in different water matrices, and 28 CECs, in soil samples. Acceptable recoveries (65–120%) were obtained for most of the CECs in all the matrices. However in the soil samples, as complexity required a prior extraction treatment, the recovery of some analytes was affected, which reduced the number of target CECs. The achieved methodological quantification limits (0.05–5 ng/L and 0.04–1.1 ng/g levels for the water and the soil matrices, respectively) were reasonably low for most CECs. The proposed method was successfully applied to monitor CECs in a VF. The CECs detected at higher concentrations are some of the world's most widely used products (e.g. acetaminophen or caffeine and its main TP, paraxanthine). The results showed an almost 70% reduction in CEC concentrations during infiltration. The groundwater data indicated that the VF treatment operation did not affect the underlying aquifer (Cmax found in GW <1 µg/L).

Effect of surface area to catchment area ratio on pollutant removal efficiency in vegetation-type facilities

In Korea, non-point source emissions have been investigated since the early 1980s, and the proportion of non-point source sources as a source unit for each land use has been evaluated based on actual measurement data following the implementation of the Total Water Pollution Control System. Recently, a lot of research has been done on the application of LID(low impact development) technology that can effectively manage nonpoint pollution and rainfall runoff. The ratio SA/CA (surface area/catchment area) is one of the design factors for LID facilities. In this study, the major objective is to analyse relationship between the SA/CA ratio and efficiencies of runoff reduction and pollutant removal. To do this, long-term monitoring has been conducted for three - years at LID facilities installed at a domestic LID pilot project complex. The type of LID facilities analyzed in this study are grassed swale, vegetative filter strip, tree filter box, planter box, and bioretention. As a result of logarithmic relation analysis, efficiencies of pollutants removal tended to increase with increasing SA/CA ratio. Among the pollutants, TP(total phosphorus) had the highest correlation with R value of 0.9365. When SA/CA is under consideration as a design factor, this research data can be used as input for the designer for calculating the specific criteria and scope.

Riparian Buffers as a Critical Landscape Feature: Insights for Riverscape Conservation and Policy Renovations

Riparian zones are critical for functional integrity of riverscapes and conservation of riverscape biodiversity. The synergism of intermediate flood-induced disturbances, moist microclimates, constant nutrient influx, high productivity, and resource heterogeneity make riparian zones disproportionately rich in biodiversity. Riparian vegetation intercepts surface-runoff, filters pollutants, and supplies woody debris as well as coarse particulate organic matter (e.g., leaf litter) to the stream channel. Riparian zones provide critical habitat and climatic refugia for wildlife. Numerous conservation applications have been implemented for riparian-buffer conservation. Although fixed-width buffers have been widely applied as a conservation measure, the effectiveness of these fixed buffer widths is debatable. As an alternative to fixed-width buffers, we suggest adoption of variable buffer widths, which include multiple tiers that vary in habitat structure and ecological function, with each tier subjected to variable management interventions and land-use restrictions. The riparian-buffer design we proposed can be delineated throughout the watershed, harmonizes with the riverscape concept, thus, a prudent approach to preserve biodiversity and ecosystem functions at variable spatial extents. We posit remodeling existing conservation policies to include riparian buffers into a broader conservation framework as a keystone structure of the riverscape. Watershed-scale riparian conservation is compatible with landscape-scale conservation of fluvial systems, freshwater protected-area networks, and aligns with enhancing environmental resilience to global change. Sustainable multiple-use strategies can be retrofitted into watershed-scale buffer reservations and may harmonize socio-economic goals with those of biodiversity conservation.

Evaluation of the Impact of Best Management Practices on Streamflow, Sediment and Nutrient Yield at Field and Watershed Scales

Evaluating Best Management Practices (BMPs) in watersheds using hydrologic and water quality models can help to establish an effective watershed water management. Soil and Water Assessment Tool (SWAT) was applied to Big Sunflower River Watershed (BSRW) and the Stovall Sherard Watershed (SSW) to evaluate BMP’s impact at watershed and field scale watersheds respectively. SWAT was calibrated and validated for streamflow, sediment yield, total nitrogen (TN), and total phosphorous (TP) at outlets of three sub-basins of the BSRW, and within the SSW. BMP scenarios of check-dam, tail water pond, vegetative filter strips (VFS), nutrient management, and tillage management were evaluated for their efficacy in reducing streamflow, sediment yield, and nutrient loads at field and watershed scales. The VFS was determined as the most effective BMP in decreasing sediment yield, TN, and TP at both field and watershed scales. At field scale, reduction of sediment yield, TN, and TP by VFS ranged from 8 to 12%, 71% to 98%, and 72% to 99% respectively and at watershed scale, reduction of sediment yield, TN, and TP by VFS ranged from 12 to 38%, 29% to 87%, and 42% to 99% respectively. The application of conservation and zero tillage operation showed reduction in sediment yield by 1% to 2% respectively but increased TN and TP by 2% to 25% at field and watershed scale watersheds. This study will help in managing water at field and watershed scale watersheds regarding BMPs selection and implementation.Graphical

ОЦЕНКА ВЛИЯНИЯ УРОВНЯ МИНЕРАЛЬНОГО ПИТАНИЯ НА МОРФОЛОГИЧЕСКИЕ ПАРАМЕТРЫ И АККУМУЛЯЦИЮ БИОГЕННЫХ ЭЛЕМЕНТОВ В БИОМАССЕ БЫСТРОРАСТУЩЕЙ ИВЫ

The article presents the results of studies for assessment of the influence of the level of mineral nutrition on the morphological parameters and accumulation of biogenic elements in the biomass of the fast-growing willow Salix alba, cv. Volmyanka. A vegetation experiment to study the dependence of the morphological parameters of willow and the accumulation of nitrogen and phosphorus in the biomass of plants on the level of mineral nutrition have been done at the experimental site (53°55’24.6 “N,27°40’04.7” E) of the Institute of Research institute of nature management Academy of science of Belarus. The vegetation experiment was based on the following options: control, without additional application of mineral fertilizers; option N50P50 (dose of application 0.5 g per vessel); option N100P100 (the dose of application is 3.0 g per vessel); option N150P150 (dose of application 4.5 g). In the vegetation experiments, the dependences of the content of total nitrogen (Ntot) and Р2О5 in the biomass of a willow plant from the doses of mineral fertilizers and the content of mineral nitrogen Nmin) and Р2О5 in the soil were obtained. The influence of the content of Nmin (N-O3 + NH4) in the soil on the content of Ntot in the plant biomass is expressed by a high degree of quantitative and qualitative characteristics of the correlation (R2 = 0.778). The influence of the content of mobile phosphorus in the soil (from 200 to 600 mg/kg) on the content of Р2О5 in the plant biomass is expressed by a moderate quantitative and qualitative characteristic of the correlation (R2 = 0.403); (from 600 to 900 mg/kg) - very high (R2 = 0.928). The influence of mineral fertilizers on the content of Р2О5 and Ntot in the aboveground plant biomass during the growing season has been established. The influence of the doses of mineral fertilizers on the productivity and morphological parameters of the aboveground biomass of willow plants has been determined. The research results confirm the assumption about the possibility of using the plantation of fast-growing willow (Salix alba), cv. Volmyanka, as a vegetative filter capable to accumulate nitrogen and phosphorus in the plant biomass, preventing their penetration into water bodies and reducing the risk of eutrophication.

Ardières‐Morcille in the Beaujolais, France: A research catchment dedicated to study of the transport and impacts of diffuse agricultural pollution in rivers

AbstractThe 8‐km2 Morcille catchment, which is a sub‐catchment of the 150‐km2 Ardières catchment in the Beaujolais region of France, is one of the first sites in Europe where research has been conducted on surface water contamination by pesticides. A consolidated hydrological and chemical dataset has been set up with data collected since 2002 on the Morcille River and since 2011 on the Ardières River. Additional data on the ecotoxicological and ecological impacts of pesticides on aquatic microbial communities and macroinvertebrates has also been recorded in both rivers since 2005. The ‘Site Atelier Ardières‐Morcille Dataset’ described here combines rainfall and stream water height measurements at gauged stations with concentrations of two trace elements and nine pesticides (mainly herbicides, fungicides and some of their metabolites) in both the Ardières and Morcille rivers. All contaminant concentration data showed spatial and temporal variability in water quality associated with pesticide use and rainfall patterns. This long‐term monitoring framework made it possible to estimate the persistence of two herbicides (diuron and norflurazon) after legislation banning them. It took 4 years for diuron and more than 10 years for norflurazon concentrations to fall below 0.1 μg/L. Concurrent biological data showed a gradient of impacts consistent with chemical anthropogenic pressure, and rapid recovery of phototrophic microbial communities after the diuron ban. Finally, monitoring data on pesticide transport in a grassed strip set on a slope of the Morcille catchment confirmed that vegetative filter strips can effectively reduce diuron fluxes in surface runoff (&gt;80% abatement) and infiltration water (&gt;70% abatement). The full dataset offers a valuable resource for the validation of hydrological models and the development of global approaches to better understand the pressure–transport–exposure–impact chain and aquatic community resilience at the small catchment scale.

Biomass Production and Removal of Nitrogen and Phosphorus from Processed Municipal Wastewater by Salix schwerinii: A Field Trial

In many Baltic regions, short-rotation willow (Salix spp.) is used as a vegetation filter for wastewater treatment and recycling of valuable nutrients to upsurge bioeconomy development. In this context, a four-year field trial (2016–2019) was carried out near a wastewater treatment plant in eastern Finland (Outokumpu) to investigate the effect of the processed wastewater (WW) on biomass production as well as the nutrients uptake capability (mainly N and P) by a willow variety (Salix schwerinii). Results indicated that WW irrigation expressively increased the willow diameter growth and biomass yield around 256% and 6510%, respectively, compared to the control treatment site (without WW). The willow was also able to accumulate approximately 41–60% of the N and 32–50% of the P in two years (2018–2019). Overall, willow showed a total 20% mortality rate under WW irrigation throughout the growing periods (2017–2019) as compared to control (39%). The results demonstrate that willow has the potential to control eutrophication (reducing nutrients load) from the wastewater with the best survival rate and can provide high biomass production for bioenergy generations in cold climatic conditions.

Applying a Hybrid Modeling Approach to Evaluate Potential Pesticide Effects and Mitigation Effectiveness for an Endangered Fish in Simulated Oxbow Habitats.

The occurrence of some species listed under the United States' Endangered Species Act in agricultural landscapes suggests that their habitats could potentially be exposed to pesticides. However, the potential effects from such exposures on populations are difficult to estimate. Mechanistic models can provide an avenue to estimating the potential impacts on populations, considering realistic assumptions about the ecology of the species, the ecosystem it is part of, and the potential exposures within the habitat. In the present study, we applied a hybrid model of the Topeka shiner (Notropis topeka), a small endangered cyprinid fish endemic to the US Midwest, to assess the potential population-level effects of realistic exposures to a fungicide (benzovindiflupyr). The Topeka shiner populations were simulated in the context of the food web found in oxbow habitats that are the focus of ongoing habitat restoration efforts for the species. We applied realistic, time-variable exposure scenarios and represented lethal and sublethal effects to individual Topeka shiners using toxicokinetic-toxicodynamic models. With fish in general showing the highest sensitivity to the compound, direct effects on simulated Topeka shiner populations governed the population-level effects. We characterized the population-level effects of different exposure scenarios with exposure multiplication factors (EMFs) applied. The introduction of a vegetative filter strip (VFS; 15 ft; 4.6 m) between the treated area and the oxbow habitat was shown to be effective as mitigation because EMFs were 2 to 3 times higher than for the exposure scenario without VFS. Environ Toxicol Chem 2021;40:2615-2628. © 2021 SETAC.

Impact of grass traits on the transport path and retention efficiency of nitrate nitrogen in vegetation filter strips

Vegetation filter strips (VFS) have been shown to effectively intercept water flow and remove nitrogen. Studies of the vegetation effects on water flow and nitrogen transport are typically studied based on qualitative analyses with species, layouts, growth stage, seasonal changes, and other vegetation conditions and did not considered quantification based on plant traits. In this study, the transport path and retention efficiency of nitrate nitrogen (NO3-N) in VFSs are investigated from the view of the plant specific trait effects by simulating runoff experiments using three grassed VFSs (centipede grass, tall fescue, and vetiver grass), as well as a bare VFS under different slope gradients (2%, 7%, and 12% slope gradients). The primary grass traits (stem spacing, root depth, root length density, and nitrogen total uptake) were measured, and the responses of water flow and NO3-N loss above and below ground to those were quantitatively assessed using the grey correlation analysis method. Results indicated that grasses and slope gradient significantly influenced the water flow and NO3-N loss in general, except the NO3-N loss concentration of the surface flow, in which the tall fescue VFS showed the highest NO3-N total retention rates under each slope condition. Considering the impact of specific grass traits, stem density and root length density has the greatest effects on the surface flow and the subsurface flow respectively, while the effect of roots was lower than that of stems on NO3-N loss below ground. Additionally, the NO3-N loss mass in the surface and subsurface flow were mostly related to the water flow volume and the NO3-N loss concentration respectively. This indicated that grass traits that reduce water flow should be considered more to control the NO3-N loss mass above ground, whereas the grass traits reducing NO3-N loss concentration should be considered more to control the NO3-N loss mass below ground.

Sediment Management for Reservoir Sustainability and Cost Implications Under Land Use/Land Cover Change Uncertainty

AbstractAddressing uncertainty in sediment predictions due to land use/land cover (LULC) change could better inform the selection of sediment management options for reservoir sustainability. We used the Nam Kong catchment of the Mekong River Basin in Southern Laos, with two hydropower dams in series, to understand the implications of LULC change uncertainty for catchment‐level and reservoir‐level sediment management options. The catchment‐level sediment management options of terracing, vegetative filter strips, and no tillage were evaluated applying the Soil and Water Assessment Tool (SWAT). The reservoir‐level sediment management option of flushing was assessed using the Sediment Simulation Screening Python Model (PySedSim). Costs of sediment management options were assessed via the economic value of the loss in hydropower production and the avoided cost of dredging. Our results suggest that LULC projections resulted in high variability in loss of reservoir capacity and cost of sediment management. Terracing was found to be the best catchment‐level management option at decreasing both the magnitude and variability in loss of reservoir storage for both dams, but it was also the most expensive option. Flushing was also effective in reducing sedimentation, but it was less economically beneficial compared to catchment‐level sediment management options. Combinations of catchment‐level and reservoir‐level management strategies, however, can be effective in reducing the magnitude and variability in loss of reservoir storage and associated costs in response to LULC change uncertainty.

Impact of BMPs on water quality: a case study in Big Sunflower River watershed, Mississippi

ABSTRACT Impact of Best Management Practices (BMPs) can be evaluated using hydrologic and water quality models. Although numerous models with diverse function, capability and degree of complexity are available, suitable model for each watershed should be determined. The Soil and Water Assessment Tool (SWAT) and Hydrologic Simulation Program-Fortran (HSPF) models were applied to the Big Sunflower River Watershed (BSRW) and their performances in simulating hydrology and water quality were evaluated. Both the models simulated streamflow, sediment, and nutrient concentrations with model efficiency greater than 50%. The SWAT model simulated streamflow and sediment concentration more accurately than HSPF whereas, for total nitrogen (TN) and total phosphorous (TP) concentrations, the HSPF model simulated equally good as SWAT. Models evaluated effect of two BMPs: vegetative filter strip (VFS) and tailwater recovery pond (TRP) in reduction of streamflow, sediment, TN, and TP concentrations. Average reduction of streamflow due to the implementation of both BMPs in SWAT and HSPF were less than 1% but average reduction of sediment concentration by VFS in SWAT was 26% and in HSPF was 38%. Average reduction of sediment concentration by TRP in SWAT and HSPF were 21% and 30% respectively. VFS reduced TN concentration by 51% in SWAT and by 25% in HSPF, while average reduction of TN concentration by TRP in SWAT and HSPF were 7% and 2% respectively. Similarly, average reduction of TP concentration by VFS in SWAT and HSPF were 56% and 31% respectively and that by TRP in SWAT and HSPF were 2% and 1% respectively. Differences in simulation results based on application of two models were mainly attributed by the modelling mechanism and equations used. The results from this study will provide a broader idea to other modellers and end-users in selecting appropriate model according to their need and type of watershed.

Application of the theory of planned behavior with agent-based modeling for sustainable management of vegetative filter strips

This study proposes an innovative socio-hydrological modeling framework for the development of environmental policies that are tailored to farmers' attitudes and economic interests but also optimize environmental criteria. From a farmers' on-site survey, a behavior model is developed based on a modified Theory of Planned Behavior (TPB). The dynamics of the social and environmental system is implemented by coupling an agent-based model (ABM) with an agro-hydrological model for vegetative filter strips (VFS). A case study is conducted with farmers from the Larqui river basin, Chile to understand their standpoint on VFS to reduce soil loss in their agricultural fields and protect water bodies. Partial least square structural equation modeling is used to analyze the survey on farmers’ aspiration and attitudes. It showed that the constructs added to TPB (behavioral morality, behavioral willingness, knowledge) had a significant effect on modeling the intention and behavior of farmers to have VFS. Based on the survey, the farmers were categorized into perceptive, proactive, bounded rational and interactive agents. An ABM was developed using the behavioral categorization, related decision rules, and utility functions of agricultural activities including the VFS implementation and management. The results of the ABM corroborate with the survey of the farmers. The survey supports the view that the decision on the width of VFS is not solely dependent on the utility generated and the reduction in soil losses but also on the behavior of farmers. This behavioral sociohydrological modeling framework is capable of supporting policy-makers in developing tailored environmental policies that might improve the acceptance of sustainable agricultural practices by farmers.

Effects of Shallow Water Table Depth on Vegetative Filter Strips Retarding Transport of Nonpoint Source Pollution in Controlled Flume Experiments

Vegetative filter strips (VFSs) have been recommended as the best management practice for reducing runoff nonpoint source (NPS) pollution. The efficiency of VFSs located adjacent to water bodies can vary with shallow water table depths (WTD). A vegetated soil tank containing silt loam soil and Shortleaf Lilyturf vegetation was designed to study the effects of VFSs under shallow WTD (0.08, 0.22, and 0.36 m) on retentions of surface runoff, sediment, phosphorus, and bromide. Experiments were conducted with a simulated rainfall intensity of 28 mm h−1 and inflow rates of 4.02–4.56 L min−1. The results revealed that a deep WTD, low grass spacing, and low slope had high VFS retention efficiencies. The retention efficiencies varied greatly from 35%, 70%, 64%, and 55% at the 0.08-m WTD in the experimental group with high grass spacing (6.69 cm) and low slope (5%) to 96%, 98%, 96%, and 95% at the 0.36-m WTD in the experimental group with low grass spacing (4.18 cm) and low slope (5%) for surface runoff, sediment, phosphorus, and bromide, respectively. A steeper slope (at the same grass spacing) increased the effects of the WTD on VFS performance. For each experimental group, the average surface runoff outflow rate decreased with the WTD, whereas the average subsurface lateral flow rate increased. The transport of phosphorus in the surface runoff almost resembled that of bromide, and the average concentration (C/C0 Ave) of phosphorus and bromide decreased with the WTD. For the subsurface lateral flow, the transport of bromide and phosphorus exhibited typical breakthrough behaviors during each experiment, and both the normalized phosphorus and bromide concentrations in increasing limbs could be described by power equations. The high concentration of pollutants in the subsurface lateral flow may have affected the adjacent water bodies and groundwater. In quantification of the impact of WTD on effectiveness of VFS, we can effectively control the NPS pollutants in a watershed.

APPLICATION OF THE AGRO-HYDROLOGIC SWAT MODEL ON THE TAABO RIVER BASIN (COTE D'IVOIRE) TO EVALUATE THE EFFECT OF THREE VEGETATIVE FILTER STRIP SCENARIOS ON STREAMFLOW AND NUTRIENTS

C te d'Ivoire is one of the world's leading producers and exporters of agricultural products. Unfortunately, the multiplicity of stakeholders in this sector and the absence of legislation and regulations have contributed to the pollution of the various hydro systems, particularly those of Taabo river basin. The purpose of this study was to assess the ability of the Soil and Water Assessment Tool (SWAT) model to test the applicability of three vegetative filter strips scenarios to minimize nutrient loads downstream of the emission fields. The model calibration (1982-1986) and validation (1987-1990) were performed for daily time periods using mathematical algorithm Sequential Uncertainty Fitting, version 2 (SUFI-2) included in the SWAT-CUP software. SWAT model produce a good simulation performance because it offered realistic simulations of streamflow both in calibration (NS = 0.67 and R2 = 0.68) and validation (NS = 0.6 and R2 = 0.6). Then, three scenarios of vegetative filter strips in sensitive sub-basins were examined. The implementation of these vegetative filter strips could have a positive impact on nutrient flows. Nevertheless, scenario 2 with a ratio of, field area and vegetative filter strip of 50, appears to be the most suitable for the agro-climatic conditions of the Taabo river basin.

植被格局对土壤入渗和水沙过程影响的模拟试验研究

合理的植被格局能够提高土壤入渗性能和抗冲性，有效阻蚀减沙，平衡土壤保持与土壤水分保蓄二者关系，进而促进生态环境的改善。基于径流小区人工模拟降雨，研究了多种植被格局生物量密度（0、50%、100%）和分布方式（坡上分布、坡下分布、均匀分布）的土壤入渗、产流、产沙特征以及土壤储水量变化。结果表明：使用Philip模型、Kostiakov模型、Horton模型模拟坡面入渗过程，Horton模型的拟合结果最优。不同植被格局产流率的变化趋势基本一致，大体可分为两个阶段：初期阶段迅速增长，中后期阶段增长变缓并逐渐趋于稳定状态。产沙率的变化趋势随植被格局的不同而略有差异。相较于产流过程，产沙过程变化剧烈、规律性差。总体而言，降低生物量密度能够增加降雨期间的径流量（从19.21 mm到25.44-38.09 mm再到51.79 mm）和侵蚀量（从118.97 g/m²到237.57-597.90 g/m²再到1400.29 g/m²），土壤水分得到更好的保蓄。从植被分布方式的角度来看，均匀分布的植被格局有利于更好地控制土壤侵蚀和径流，却促进了土壤水分的消耗。坡下分布的植被格局，例如植被过滤带的形式，能够最好地同时控制水土流失和土壤耗水。权衡考虑水土流失防治与土壤水分消耗，建议采用适宜密度（本研究为110 g/m²）且集中分布在出口附近的植被格局。;Reasonable vegetation pattern can improve soil infiltration performance and erosion resistance, effectively reduce runoff and sediment yield, balance the relationship between soil erosion prevention and soil water conservation, and then promote the improvement of the ecological environment. In the plot scale, based on artificial simulated rainfall, the soil infiltration, runoff, sediment production characteristics and soil storage of various vegetation patterns biomass density (0, 50%, 100%) and distribution methods (concentrated distribution on the upper of the slope, concentrated distribution on the lower of the slope, uniform distribution) were studied. The results show that among the Philip model, Kostiakov model, and Horton model used to simulate the slope infiltration process, the Horton model has the best fitting results. The change trend of runoff rate of different vegetation patterns is basically the same, which can be roughly divided into two stages: rapid growth in the initial stage, slower growth in the middle and later stages and gradually tending to a stable state. The variation trend of sediment yield varies slightly with the vegetation pattern. Compared with the runoff process, the sediment production process changes drastically and has poor regularity. Overall, reducing biomass density can increase runoff (from 19.21 mm to 25.44-38.09 mm to 51.79 mm) and erosion (from 118.97 g/m² to 237.57-597.90 g/m² to 1400.29 g/m²), as well as soil moisture is better preserved. The concentrated vegetation pattern under the slope, such as the form of vegetation filter belt, can best control both soil erosion and soil water consumption. Comprehensively considering soil erosion prevention and soil water consumption, it is recommended to use a vegetation pattern with appropriate density (110 g/m² in this study) and concentrated distribution near the exit.

Quantifying the Importance of Preferential Flow in a Riparian Buffer

HighlightsRiparian buffers and vegetative filter strips are uniquely susceptible to preferential flow.An innovative method is proposed to partition infiltration into matrix and macropore domains.Riparian buffer matrix and plot-scale infiltration experiments were simulated with HYDRUS-1D and VFSMOD.Preferential flow accounted for 32% to 47% of infiltration depending on hydrologic conditions.Preferential flow mechanisms should be incorporated into riparian buffer design tools and models.Abstract. Riparian buffers are uniquely susceptible to preferential flow due to the abundance of root channels, biological activity, and frequent wetting and drying cycles. Previous research has indicated such susceptibility and even measured the connectivity of preferential flow pathways with adjacent streams and rivers. However, limited research has attempted to partition the riparian buffer infiltration between matrix and preferential flow domains. The objectives of this research were to develop an innovative method to quantify soil matrix infiltration at the plot scale, develop a method to partition infiltration into matrix and macropore infiltration at the plot scale, and then use these methods to quantify the significance of macropore infiltration at a riparian buffer site. This research further demonstrated the importance of considering preferential flow processes in design tools and models to evaluate riparian buffer effectiveness. Sprinkler and runon field experiments were conducted at an established riparian buffer site with sandy loam soil. Trenches were installed and instrumented with soil moisture sensors along the width of the riparian buffer (i.e., along the flow path toward the stream) for detecting non-uniform flow patterns due to preferential flow. Riparian buffer parameters, including soil hydraulic parameters, were estimated using HYDRUS-1D for the sprinkler experiments and VFSMOD for the runon experiments. This research partitioned the infiltration into matrix and preferential flow domains by assuming negligible exchange of water between the soil matrix and preferential flow pathways in comparison to the magnitude of soil matrix flow. For these experimental conditions with 0.20 to 0.48 L s-1 of runon and initial soil water contents of 0.29 to 0.32 cm3 cm-3, preferential flow accounted for at least 27% to 32% of the total runon water entering the riparian buffer. This corresponded to approximately 32% to 47% of the total infiltration. While increasing the riparian buffer plot soil hydraulic conductivity in single-porosity models can adequately predict the total infiltration and therefore the surface outflow from the buffer, design tools and models should specifically consider preferential flow processes to improve predictive power regarding the actual infiltration processes and correspondingly the non-equilibrium flow and solute transport mechanisms. Keywords: Flow partitioning, HYDRUS, Matrix flow, Preferential flow, Riparian buffer, VFSMOD.

Sediment particle selectivity and its response to overland flow hydraulics within grass strips

AbstractParticle selectivity plays an important role in clarifying sediment transport processes in vegetative filter strips (VFS). 10‐m long grass strips at slopes of 5° and 15° were subjected to a series of sediment‐laden inflows experiments with different particle sizes to investigate the sediment transport and its response to overland flow hydraulics. The inflow sediments came from local soil, river‐bed sand, and mixed, with median particle size d50 of 39.9, 207.9 and 77.4 μm, respectively. Three independent repeated experiments were carried for each treatment. The results show that when the sediment trapping lasted for a certain length of time, the re‐entrainment of some small‐sized particles was greater than the deposition; that is, net loss occurred, which was not erosion of the original soil. Net loss of particles is mainly determined by the particle diameter. The coarser the inflow sediment particles and/or the steeper the slope, the coarser the particles can be net lost. Deposited sediment causes the VFS bed surface to become smooth and hydraulic resistance decrease exponentially. Unit stream power P is more suitable than shear stress τ of overland flow to be used to describe the process of sediment particle transport in VFS. The relationship between P and d50 of outflow sediment is very consistent with the form of power function with a constant term. These results are helpful to understand the physical process of sediment transport on vegetation hillslopes.

Green filters of Eucalyptus globulus for microalgae harvesting from freshwater reservoir and reuse of biomass harvested for pellet production

Filtration was used for the separation of microalgae from water collected at the reservoir of a Baxe, in north-western Spain, where cyanobacterial blooms are known to occur. The barks of Eucalyptus globulus were used as bed filters. Filters were made with compacted and non-compacted barks of 0.5, 1 and 2 g. Filtration of water with compacted barks showed the best results with yields of 43.12, 76.85 and 63.67 % for the different weights. The microalgae obtained and the vegetation filters were used for the manufacturing of pellets to be used as fuels. Their energy potential was studied according to different parameters such as calorific value, humidity, volatile matter and ash content, to verify the requirements for the use of pellets as fuel in biomass boilers met the criteria according to UNE Standards. These pellets meet the requirements of UNE standards established and could, therefore, be used in boilers as biofuels. Obtaining a high heating value above to 15.00 MJ/kg, greater than 17.00 MJ/kg for all samples except the pellet sample with only microalgal biomass. The samples have a lower ash content of (10 %), with the exception of the microalgae pellet without eucalyptus bark (13.67 %). The use of Eucalyptus bark is a feasible option for the separation of microalgae in aquatic ecosystems. The next step would be to carry out the experiments on a large scale in a reservoir with eutrophication problems, to test if it works correctly under different conditions. Although the aim of obtaining pellets for boilers does not pursue an economic or commercial objective, the results obtained were promising. This would help towards reducing forest waste and as consequence, reducing environmental pollution.

Optimization of the wastewater treatment capacity of a short rotation willow coppice vegetation filter

The objective of this study was to determine the conditions to optimize the wastewater treatment efficiency of a short rotation willow coppice (SRWC) plantation (Salix miyabeana ‘SX67’) used as a vegetation filter to treat small municipal primary effluents (with less than 800 population equivalent). With the aim of maximizing the annual amount of wastewater treated, the effect of adjusting the hydraulic loading rate (HLR) according to the estimated evapotranspiration was tested at demonstration scale under humid continental climate conditions. We proposed a new method to calculate the evapotranspiration rate from plant physiological data, introducing an α factor based on direct transpiration measurements. This method increased the accuracy of the water balance, with a prediction of the crop coefficient (kc) based on either an seasonal approach (R2 of 0.88) or a monthly approach (R2 of 0.94). This led to a more precise estimation of the pollutant loading reaching the groundwater and could be used after plantation establishment as a fine-tuning tool. Adjusting the HLR to that of evapotranspiration between May and October led to an annual increase of 2 mm/d (around 0.35 m3/m2 per growing season) in HLR, while maintaining a pollutant loading removal efficiency of at least 96% for organic matter, 99% for total phosphorus and 93% for total nitrogen. A high HLR at the end of the season caused nitrogen leaching into groundwater, indicating that the HLR should be decreased in October, when willow growth is greatly reduced.