Sara E. Vero

Consequences of varied soil hydraulic and meteorological complexity on unsaturated zone time lag estimates.

The true efficacy of a programme of agricultural mitigation measures within a catchment to improve water quality can be determined only after a certain hydrologic time lag period (subsequent to implementation) has elapsed. As the biophysical response to policy is not synchronous, accurate estimates of total time lag (unsaturated and saturated) become critical to manage the expectations of policy makers. The estimation of the vertical unsaturated zone component of time lag is vital as it indicates early trends (initial breakthrough), bulk (centre of mass) and total (Exit) travel times. Typically, estimation of time lag through the unsaturated zone is poor, due to the lack of site specific soil physical data, or by assuming saturated conditions. Numerical models (e.g. Hydrus 1D) enable estimates of time lag with varied levels of input data. The current study examines the consequences of varied soil hydraulic and meteorological complexity on unsaturated zone time lag estimates using simulated and actual soil profiles. Results indicated that: greater temporal resolution (from daily to hourly) of meteorological data was more critical as the saturated hydraulic conductivity of the soil decreased; high clay content soils failed to converge reflecting prevalence of lateral component as a contaminant pathway; elucidation of soil hydraulic properties was influenced by the complexity of soil physical data employed (textural menu, ROSETTA, full and partial soil water characteristic curves), which consequently affected time lag ranges; as the importance of the unsaturated zone increases with respect to total travel times the requirements for high complexity/resolution input data become greater. The methodology presented herein demonstrates that decisions made regarding input data and landscape position will have consequences for the estimated range of vertical travel times. Insufficiencies or inaccuracies regarding such input data can therefore mislead policy makers regarding the achievability of water quality targets.

Review: the environmental status and implications of the nitrate time lag in Europe and North America.

The efficacy of water quality policies aiming to reduce or prevent nitrate contamination of waterbodies may be constrained by the inherent delay or “time lag” of water and solute transport through unsaturated (soil) and saturated (groundwater) pathways. These delays must be quantified in order to establish realistic deadlines, thresholds and policy expectations, and to design effective best management practices. The objective of this review is to synthesise the current state of research on nitrate-related time lags in both the European and North American environmental and legislative contexts. The durations of time lags have been found to differ according to climatic, pedological, landscape and management scenarios. Elucidation of these driving factors at a watershed scale is essential where water quality is impaired or at risk. Finally, the existence of time lags is increasingly being acknowledged at a policy level and incorporated into the development of environmental legislation. However, the full impact of these time lags is not yet fully understood or appreciated, and continued outreach and education in scientific, public and policy venues is still required.RésuméL’efficacité des politiques visant à la réduction et la prévention de la contamination en nitrate des masses d’eau doit être évaluée au regard du délai inhérent ou décalage temporel du transport de l’eau et des solutés au travers de la zone non saturée (sols) et saturée (nappe). Ces délais doivent être quantifiés afin de permettre d’établir des échéances, seuils et attentes réglementaires réalistes, et pour établir des règles efficaces de bonnes pratiques. L’objectif de cette revue est. de faire une synthèse de l’état des recherches sur les délais de transfert du nitrate dans un contexte environnemental et législatif européen et nord-américain. L’importance du décalage temporel diffère selon les scénarios climatiques, pédologiques, d’occupation des sols et de gestion. L’analyse de ces facteurs à l’échelle des bassins versants est. essentielle lorsque la qualité de l’eau est. dégradée ou à un risque de dégradation. Enfin, l’existence d’un décalage temporel est. de plus en plus reconnue au niveau des politiques et intégrée dans la mise en œuvre de la législation environnementale. Toutefois, l’impact total de ce décalage temporel n’est. pas complètement compris ou apprécié, et la poursuite de la sensibilisation et de la formation lors d’événements scientifiques, réunions publiques et rencontres politiques sont toujours nécessaires.ResumenLa eficacia de las políticas de calidad del agua destinadas a reducir o prevenir la contaminación por nitratos de los cuerpos de agua puede verse limitada por el retraso inherente o el “retraso temporal” del transporte de agua y de soluto a través de rutas no saturadas (suelo) y saturadas. Estos retrasos deben cuantificarse para establecer plazos, umbrales y expectativas normativas realistas, y para diseñar mejores prácticas eficaces de gestión. El objetivo de esta revisión es sintetizar el estado actual de la investigación sobre los retardos relacionados con los nitratos en el contexto ambiental y legislativo europeo y norteamericano. Se ha comprobado que las duraciones de los retardos de tiempo difieren según los escenarios climáticos, pedológicos, paisajísticos y de gestión. La dilucidación de estos factores de conducción a escala de cuenca es esencial cuando la calidad del agua está deteriorada o en riesgo. Por último, la existencia de retardos es cada vez más reconocida a nivel político e incorporada en el desarrollo de la legislación ambiental. Sin embargo, aún no se ha comprendido ni apreciado plenamente el impacto total de estos retardos, y se sigue requiriendo la extensión y educación continua en lugares científicos, públicos y políticos.摘要旨在预防水体遭受硝酸盐污染的税制政策效力可能受到水和溶质通过非饱和(土壤)和饱和(地下水)通道迁移中固有的延迟或“时间滞后”的制约。对这些延迟必须量化以便建立现实的警戒线、阈值和政策期望值,设计有效的最佳管理模式。本文的目的就是梳理欧洲和北美洲环境和立法背景下目前与硝酸盐相关的时间滞后研究现状。发现时间滞后的持续时间依据气候、土壤、地形和管理方案的不同而有所不同。在水质受损或处于危险之中的地方,流域尺度上阐明这些驱动因素至关重要。最后,时间滞后的存在在政策层面上日益得到人们的认可,并被纳入环境立法中。然而,这些时间滞后的全部影响没有被完全理解或领会,仍然需要在科学、公共和政策方面给予持续的拓展和培养。ResumoA eficácia de políticas de qualidade da agua que visam reduzir ou prevenir a contaminação por nitrato em corpos d’água pode ser prejudicada pelo atraso inerente, ou ‘defasagem temporal’ do transporte de água e de soluto através dos meios não saturado (solo) e saturado (agua subterrânea). Estes atrasos têm de ser quantificados a fim de definir prazos reais, os limites e as expectativas políticas, e para a definição das práticas mais efetivas de gestão. O objetivo desta revisão é fazer uma síntese do conhecimento atual da pesquisa sobre a defasagem temporal do nitrato no contexto das legislações europeia e norte-americana. A duração dos atrasos difere de acordo com os diferentes cenários climáticos, pedológicos, relevo e de gerenciamento. O esclarecimento destes fatores condicionantes na escala da bacia hidrográfica é essencial ali onde a qualidade da água está afetada, ou em risco. Finalmente, a existência das defasagens temporais tem sido gradualmente reconhecida no nível político e incorporado dentro do desenvolvimento da legislação de meio ambiente. Entretanto, o impacto completo das defasagens temporais ainda não foi completamente compreendido ou dimensionado, fazendo-se necessário atingir e educar permanentemente os foros científicos e políticos.

Application of Dexter’s soil physical quality index: an Irish case study

Abstract Historically, due to a lack of measured soil physical data, the quality of Irish soils was relatively unknown. Herein, we investigate the physical quality of the national representative profiles of Co. Waterford. To do this, the soil physical quality (SPQ) S-Index, as described by Dexter (2004a,b,c) using the S-theory (which seeks the inflection point of a soil water retention curve [SWRC]), is used. This can be determined using simple (S-Indirect) or complex (S-Direct) soil physical data streams. Both are achievable using existing data for the County Waterford profiles, but until now, the suitability of this S-Index for Irish soils has never been tested. Indirect-S provides a generic characterisation of SPQ for a particular soil horizon, using simplified and modelled information (e.g. texture and SWRC derived from pedo-transfer functions), whereas Direct-S provides more complex site-specific information (e.g. texture and SWRC measured in the laboratory), which relates to properties measured for that exact soil horizon. Results showed a significant correlation between S-Indirect (Si) and S-Direct (Sd). Therefore, the S-Index can be used in Irish soils and presents opportunities for the use of Si at the national scale. Outlier horizons contained >6% organic carbon (OC) and bulk density (Bd) values <1 g/cm3 and were not suitable for Si estimation. In addition, the S-Index did not perform well on excessively drained soils. Overall correlations of Si. with Bd and of Si. with OC% for the dataset were detected. Future work should extend this approach to the national scale dataset in the Irish Soil Information System.

Tungsten Contamination of Soils and Sediments: Current State of Science

Tungsten (W) is commonly employed as a non-toxic alternative to lead in a broad variety of industrial and military applications. However, correlations between environmental contamination through soil, water and airborne pathways, and biological effects such as epithelial damage, bioaccumulation, and trophic mobility, have led to its classification as an “emerging contaminant.” Of particular concern are recent clusters of childhood leukemia and lung cancer in the vicinity of tungsten mines and processing facilities. High environmental tungsten availability has also been associated with altered thyroid function, cardiovascular disease, and prolonged elevation of concentrations in blood, breath, and urine. Tungsten’s use as a replacement for lead (Pb) in military munitions has resulted in leaching of tungsten into soil and into soft tissues in which bullet fragments are embedded. Despite these associations, no consensus has been reached regarding the mechanisms by which tungsten affects the human body. Particularly confounding are the issues of co-toxicity with other known contaminants such as arsenic, cobalt, and cadmium, and differences resulting from the various methods of ingestion. The present paper summarizes the current behavior of tungsten in the environment, its occurrence within the pedosphere, biosphere, and atmosphere, and discusses its potential effects on exposed biota (especially humans). In particular, knowledge gaps are identified regarding the biological mechanisms of tungsten-related disease, which urgently require further elucidation in order to develop appropriate policies and management practices for the use of this element.

Soils and Water Quality

Ireland has a diverse physical landscape of upland and lowland inland waters represented by 13,200 km of river and 12,000 lakes framed by an estimated 3171 km of coastline providing a range of freshwater ecosystem services. The quality and quantity of water flowing through Ireland’s inland and coastal waters are determined by the complex interaction of anthropogenic activities with soil and climate. It is the mosaic of soils that characterise the catchment draining a waterbody that regulates the flow of water through a catchment and the movement of nutrients and contaminants. In this chapter, we describe the role of soil as the matrix through which, water and contaminants can be transported and retained within the Irish landscape, and the impacts on water quality in Ireland. Here we reference current water quality policies relating to diffuse of pollution from soils and describe processes and functions identified in Irish soils that influence nutrient and sediment transport to affect water quality in Ireland.

The effect of soil moisture deficit on the susceptibility of soil to compaction as a result of vehicle traffic

Soil compaction negatively affects soil productivity, fertilizer use efficiency and water infiltration. The extent of compaction is dependant on soil strength, which is influenced by the soil moisture content. The purpose of this study was to determine the extent of soil compaction (measured by changes in soil bulk density and shear strength) and soil deformation incurred due to a single pass of a tractor and a fully loaded slurry tanker over grassland soils at a range of soil moisture deficits (SMD). The study should identify threshold values of SMD at which adverse soil compaction becomes significant for the soil-crop system. These values may be incorporated into the forecasting and decision making process for slurry spreading. SMD was used as a proxy for volumetric water content. Treatments of a single pass by a Landini Vision 105 tractor and a loaded 7.2 m³ single axle slurry tanker (total weight of c. 18 tonnes) were conducted on well, moderate and poorly drained grassland soils at forecasted SMD of 0, 5, 10 and 20 mm. The moderately drained soil was classified as a loam, while the well and poorly drained sites were classified as sandy loams. Changes in soil bulk density and torsional shear strength were used as indicators of compaction, with rut profile measurements taken to measure the extent of surface deformation, which is often the most visible indicator of compaction on the soil surface. Grass yields were measured at 30 and 60 days subsequent to trafficking. Results showed that SMD at the time of traffic had an effect on the changes in bulk density, shear strength and the extent of soil rutting following wheel traffic. Preliminary results indicate that higher SMD at the time of trafficking resulted in smaller changes to soil characteristics and more rapid recovery from surface deformation than when trafficking occurred at lower SMD. Trafficking at an SMD of 20 mm led to mean increases in soil bulk density of 8% and formation of ruts with cross sectional areas in the range of 29.4 cm² to 98.3 cm². Trafficking at 0 SMD (field capacity) led to mean increases in bulk density of 15% and the formation of rut profiles in the range of 91.6 cm² to 197.9 cm². These preliminary results indicate that forecasted SMD provides a valuable tool to determine the suitability of the soil for supporting farm vehicle operations such as slurry spreading. This study is still ongoing, with more detailed results and analysis to be forthcoming.

Soils and Productivity

This chapter explores the predominant land-based production systems in Ireland, specifically describing grassland, arable and forestry production. Grass is the most important agricultural crop in Ireland representing the main feed source for the livestock sector. Arable production represents a relatively small area, largely due to excess soil moisture conditions that are typical of many Irish soils. Despite favourable conditions for forestry in Ireland, the level of forest cover is low by European standards and has historically been associated with sub-marginal and marginal agricultural land. The importance of soil structure in the provision of nutrients, water and air is emphasised along with best management practices in relation to the management cycle. The role of soil texture is outlined, as is the agroclimate and soil interaction in Irish soils. The agricultural drainage conditions of Irish soils fall into the temperate zone, where the main role of drainage is the removal of excess water in the root zone of crops from surplus rainfall. This follows with a historical account of land drainage schemes in Ireland. Finally, the issues of the main production systems on poorly drained soils and the cultural practices to maintain trafficability are described. Improving the overall trafficability of any soil first requires the identification of factors causing either excessive moisture or poor soil structure. Correctly ascertaining these issues allows implementation of appropriate preventative and remediation measures, and should be the initial step in any management strategy.

A methodological framework to determine optimum durations for the construction of soil water characteristic curves using centrifugation

Abstract During laboratory assessment of the soil water characteristic curve (SWCC), determining equilibrium at various pressures is challenging. This study establishes a methodological framework to identify appropriate experimental duration at each pressure step for the construction of SWCCs via centrifugation. Three common temporal approaches to equilibrium – 24-, 48- and 72-h – are examined, for a grassland and arable soil. The framework highlights the differences in equilibrium duration between the two soils. For both soils, the 24-h treatment significantly overestimated saturation. For the arable site, no significant difference was observed between the 48- and 72-h treatments. Hence, a 48-h treatment was sufficient to determine ‘effective equilibrium’. For the grassland site, the 48- and 72-h treatments differed significantly. This highlights that a more prolonged duration is necessary for some soils to conclusively determine that effective equilibrium has been reached. This framework can be applied to other soils to determine the optimum centrifuge durations for SWCC construction.