Potential Efficiency of Grassy or Shrub Willow Buffer Strips against Nutrient Runoff from Soybean and Corn Fields in Southern Quebec, Canada

A three-dimensional perspective of phosphorus retention across a field-buffer strip transition

Vegetated filter strips (VFS) act as buffer zones between fields and water bodies that are supposed to retain incoming runoff, sediment, and nutrients. The factors that govern nutrient retention and cycling in VFS are complex and act in all three dimensions. A key element that determines VFS effectivity is flow type, e.g., sheet vs. concentrated flow. These aspects are, however, often insufficiently accounted for in VFS research and design recommendations. In this study, we attempt to tackle these shortcomings by examining the nutrient distribution in detail at two field-VFS transitions, applying a three-dimensional sampling array together with extensive laboratory analyses. Concentrated runoff was the dominant type we found and we argue that flow convergence is the norm rather than the exception. Further complicating this issue is that entry locations of runoff may vary, calling for more sophisticated sampling designs. Overall trends were similar across the analyzed nutrient fractions (different K- and P-pools) and there were distinct trends of decreasing nutrients along the longitudinal (from the field to the VFS) and vertical planes. The horizontal plane (from outside to inside the area of concentrated flow) showed mostly inconclusive or U-shaped gradients. Both sites were similar and close to each other, nevertheless, there were significant differences that affected nutrient retention in the VFS which were linked to site-specific factors. The spatial extent (i.e., width) is often considered the main variable in VFS designs. However, other VFS traits such as vegetation type and structure, as well as external factors such as field topography and the severity of erosive events are equally important and should be attributed more significance.

Phytoremediation by ornamental plants: a beautiful and ecological alternative

Phytoremediation is an eco-friendly and economical technology in which plants are used for the removal of contaminants presents in the urban and rural environment. One of the challenges of the technique is the proper destination of the biomass of plants. In this context, the use of ornamental plants in areas under contamination treatment improves landscape, serving as a tourist option and source of income with high added value. In addition to their high stress tolerance, rapid growth, high biomass production, and good root development, ornamental species are not intended for animal and human food consumption, avoiding the introduction of contaminants into the food web in addition to improving the environments with aesthetic value. Furthermore, ornamental plants provide multiple ecosystem services, and promote human well-being, while contributing to the conservation of biodiversity. In this review, we summarized the main uses of ornamental plants in phytoremediation of contaminated soil, air, and water. We discuss the potential use of ornamental plants in constructed buffer strips aiming to mitigate the contamination of agricultural lands occurring in the vicinity of sources of contaminants. Moreover, we underlie the ecological and health benefits of the use of ornamental plants in urban and rural landscape projects. This study is expected to draw attention to a promising decontamination technology combined with the beautification of urban and rural areas as well as a possible alternative source of income and diversification in horticultural production.

The interactions of site-specific factors on riparian buffer effectiveness across multiple pollutants: A review

Following decades of riparian buffer zone (RBZ) studies there remains a need to look across individual site data for collective evidence on the site-specific pollution mitigation and river water quality. We explored primary study evidence on runoff, sediment, P, N, coliforms and pesticides using complimentary styles of metadata interpretation. A quantitative assessment of pollution retention (75 studies, 474 data rows) derived relationships for retention versus width, including significant covariates of clay particle size and buffer slope for sediment, total and dissolved P. Total N and coliforms related to texture and slope but were independent of width. Other factors across pollutants were inconsistently reported. With limitations on quantitative studies a second approach examined factor significance (formal testing versus inferred; 93 studies) across source pressure, transport/physical, vegetation and soil biogeochemical factors on pollution effectiveness. The RBZ evidence showed considerable disagreement and bias in shorter term study implications on longer-term processes. Screening for stronger evidence by study number and agreement left fifteen factors informing on at least one pollutant, whereas only rainfall intensity, preferential deposition, tree planting, soil infiltration remained addressing three or more pollutants. Key messages were that: data complexities, from short-term trapping in upper buffer edges and so-called 'negative effectiveness' associated with internal recycling and/or errors in constraining mass inputs for dissolved pollutant and subsurface transport require careful interpretation; RBZ intervention and study durations were limited compared to effect times (particularly vegetation management and changing soil conditions); factors affect pollutants with particulate and dissolved phases differently and must be understood to limit RBZ pollution swapping. Buffer functioning is highly site-specific. To understand this better attention should be given to revisiting studies of vegetation management to extend timeframes, wider study of belowground (soil biogeochemical and transport) processes and studies should document site contexts across source pressures, riparian hydrological, soil and vegetation factors.

Land use and landscape position influence soil organic phosphorus speciation in a mixed land use watershed

Land use can significantly alter soil P forms, which will influence P loss in runoff. Organic P (P_o ) compounds are an important component of soil P, but their forms and cycling in soils with different land uses are still poorly understood. In addition, streambanks are potential sources of P loss; P forms and concentrations in streambank soils may vary with land use, affecting potential P loss to water. This study used solution ³¹ P nuclear magnetic resonance spectroscopy to characterize and quantify P in interior and streambank soils (0-10 cm) under duplicate sites from four different land uses along streams in the Missisquoi River basin (VT, USA): silage corn, hay meadow, emergent wetlands, and forest. Orthophosphate monoesters were the dominant P compound class regardless of land use or landscape position. Forest soils had the lowest P_o concentrations, less labile P forms than other soils, and significantly lower concentrations of total inositol hexakisphosphates and total orthophosphate monoesters compared with corn soils. Riparian buffer zones for agricultural soils lowered P concentrations in streambank soils for many soil P pools relative to interior soils. The wetland soils of this study had P concentrations and P forms that were similar to those for interior agricultural soils and generally showed no reduction in P concentrations in streambank soils relative to interior soils. This is consistent with the role of wetlands as P sinks in the landscape but also suggests these wetlands should be carefully monitored to minimize P accumulation, especially in streambank soils.

The carbon stable isotope compositions of glyphosate and aminomethylphosphonic acid (AMPA): Improved analytical sensitivity and first application to environmental water matrices

RATIONALE

The presence of glyphosate and its degradation product aminomethylphosphonic acid (AMPA) in the environment has adverse effects on environmental quality, raising the need to better constrain their fates, in particular the processes that control their production and degradation. Our aim was to improve the sensitivity of their δ¹³ C analysis and demonstrate the feasibility of measuring them in natural surface water.

METHODS

The δ¹³ C values of dissolved glyphosate and AMPA were determined using isotope ratio mass spectrometry (IRMS) (Delta V Plus instrument) coupled to a high-performance liquid chromatography (HPLC) unit, where glyphosate and AMPA were separated on a Hypercarb column.

RESULTS

We demonstrated an improved sensitivity of the δ¹³ C analysis for glyphosate and AMPA by LC/IRMS compared with previous studies. For waters from the carbonate and silicate hydrofacies, while no pretreatment was required for the isotope analysis of glyphosate, removal by H₃ PO₄ acidification of dissolved inorganic carbon, that co-elutes with AMPA, was required prior to its analysis. We successfully tested a freeze-drying pre-concentration method showing no associated isotope fractionation up to concentration factors of 500 and 50 for glyphosate and AMPA, respectively.

CONCLUSIONS

We demonstrated, for the first time, the feasibility of measuring the δ¹³ C values of glyphosate and AMPA in natural surface waters with contrasted hydrofacies (calcium carbonate and silicate types). This opens new fields in pesticide research, especially on the characterization of processes that control their degradation and the production of their secondary byproducts.

Performance of woody and herbaceous plant polyculture in constructed wetland for treating domestic wastewater

Effect of polyculture of woody and herbaceous plant with different ecological niche in constructed wetlands (CWs) on wastewater treatment is unclear. Herein, three kinds of polyculture CWs were constructed to treat domestic wastewater: woody polyculture system (W, Nerium and Hibiscus), herbaceous polyculture system (H, Acorus and Typha), woody and herbaceous polyculture system (WH, Nerium, Hibiscus, Acorus and Typha) and non-planted system (N) as control. The seasonality removal performance of pollutant, activities of urease and phosphatase, microscopic characteristics of roots were measured. Results showed that the average removals of COD, TN and TP in WH were significantly higher than that in the other systems. Interspecies competition existed in WH system, while the difference in terms of biomass gradually diminished. Furthermore, the root lengths, area, volume and tip number were higher compared to the other systems. The correlation between the removal rate of TP and activity of phosphatase in upper and bottom layer of CWs showed the opposite tendency, the distribution of plant roots in polyculture essentially impact TP removal rate in CWs. Our results provide the necessary insights for appropriately selecting different plant types for doing polyculture in CWs.

Current Insights into the Effectiveness of Riparian Management, Attainment of Multiple Benefits, and Potential Technical Enhancements

Buffer strips between land and waters are widely applied measures in diffuse pollution management, with desired outcomes across other factors. There remains a need for evidence of pollution mitigation and wider habitat and societal benefits across scales. This paper synthesizes a collection of 16 new primary studies and review papers to provide the latest insights into riparian management. We focus on the following areas: (i) diffuse pollution removal efficiency of conventional and saturated buffer strips, (ii) enhancing biodiversity of buffers, (iii) edge-of-field technologies for improving nutrient retention, and (iv) potential reuse of nutrients and biomass from buffers. Although some topics represent emerging areas, for other well-studied topics (e.g., diffuse pollution), it remains that effectiveness of conventional vegetated buffer strips for water quality improvement varies. The collective findings highlight the merits of targeted, designed buffers that support multiple benefits, more efficiently interrupting surface and subsurface contaminant flows while enhancing diversity in surface topography, soil moisture and C, vegetation, and habitat. This synthesis also highlights that despite the significant number of studies on the functioning of riparian buffers, research gaps remain, particularly in relation to (i) the capture and retention of soluble P and N in subsurface flows through buffers, (ii) the utilization of captured nutrients, (iii) the impact of buffer design and management on terrestrial and aquatic habitats and species, and (iv) the effect of buffers (saturated) on greenhouse gas emissions and the potential for pollution swapping.