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HYDRUS (2D/3D) model was used to simulate spatial and temporal distributions of nitrate-nitrogen (NO3-NNO3-N) within and below the onion root zone under conventional furrow fertigation with the urea-ammonium-nitrate (UAN) liquid fertilizer. The simulated water contents in the furrow irrigated onion field agreed well with the measurements. Simulations produced similar patterns of the measured NO3-N concentration profiles throughout the growing season. NO3-N concentrations remained higher and accumulation of NO3-N was observed within the root zone. Higher NO3-N within the root zone was dependent on the rate of the UAN fertilizer application, quantity of NO3-N removed by root uptake, and NO3-N drainage fluxes below the root zone. Simulations also suggested that NO3-N below the root zone during different growth stages remained much higher than a recommended (for drinking water) standard concentration level (10 mg L-1). This resulted in higher NO3-N drainage fluxes, particularly during the fertigation events between the establishment and vegetative growth stages. This indicates the need to apply most fertigation events at an early stage of bulb formation to provide the maximum NO3-N demands by onions and to reduce potential NO3-N leaching.

Quantitative information about the spatial and temporal patterns of compensatory root water uptake (RWU) in flood-irrigated pecan orchard is limited. We evaluated spatio-temporal compensated and uncompensated RWU patterns of mature pecan tree in a silty clay loam orchard using the HYDRUS (2D/3D) model. HYDRUS (2D/3D) simulations, which agreed well with measured water contents and temperatures at different soil depths and horizontal distances from the tree trunk, suggested that while both compensated and uncompensated RWU varied with soil depth they did not do so laterally because of similar spatial vertical distributions of root length density (RLD) for the under-canopy and the tree canopy dripline locations. Considering compensated RWU resulted in an increase in actual transpiration by 8%, and a decrease in evaporation and drainage by 5% and 50%, respectively, during a growing season. Simulated transpiration and relative transpiration (a ratio between actual and potential transpiration) values were correlated with measured transpiration and plant-based water stress indicators (stem and leaf water potentials), respectively. Overall, our results of the spatio-temporal compensatory RWU provide support to use HYDRUS (2D/3D) as a tool for managing efficient water use of pecan. © 2013 American Society of Civil Engineers. ASCE/AUGUST 2013.

Understanding the composition and fluxes of vadose zone soil water is extremely important to many environmental studies, and hence the monitoring of soil solution is of basic interest for different scientific and practical fields, including pedologic studies, water-use management, fate and transport of environmentally consequential pollutants, monitoring of disposal from mining and industries, nutrient management of agricultural and forest ecosystems, ecology, and environmental protection. Soil solution sampling techniques for effectively monitoring the quality and quantity of vadose zone soil pore water have been used to assess the persistence and transport of potential groundwater pollutants, assess the ecological and human health impact of such pollutants, and develope appropriate remediation strategies. However, there is still no consensus as to best techniques for soil solution collection at most field or laboratory soil conditions. The purpose of this review is to evaluate different laboratory and in-situ techniques of vadose zone soil solution sampling. This comprehensive review presents and discusses advantages and disadvantages of these techniques, problems and limitations of some of these techniques, proper installation, operation and pretreatment of samplers, interaction of pollutants with sampler materials, and proper selection of samplers under a wide range of potential pollutants measurements to provide a background and guidelines for the evaluation of recent developments. Key words: soil solution, soil solution sampling techniques, suction cups, suction lysimeter applications. La comprehension de la composition et des flux de l'eau du sol en zone vadose revet une tres grande importance dans plusieurs etudes environnementales; consequemment, le suivi des solutions de sol est d'interet fondamental pour different s aspects de la science et de la pratique incluant les etudes pedologiques, l'amenagement de l'utilisation de l'eau, le transport et le devenir de polluants a consequences environnementales, le suivi des dechets miniers et industriels, l'amenagement des nutriments dans les ecosystemes agricoles et forestiers, l'ecologie, et la protection environnementale. On utilise des techniques d'echantillonnage de la solution de sol pour suivre de facon efficace, qualitative et quantitative l'eau capillaire de la zone vadose pour evaluer la persistance el le transport de polluants potentiels des nappes phreatiques, et pour developper des strategies de remediation. Cependant, il n'existe pas presentement de consensus sur les meilleures techniques pour recolter la solution de sol dans la majorite des conditions de laboratoire et de champ. Les auteurs cherchent ici a evaluer les differentes techniques in situ et de laboratoires pour l'echantillonnage de la solution de sol en zones vadoses, Dans celte revue d'ensemble, ils presentem et discutent les avantages et desavantages de ces techniques, les problemes et limitations de certaines de ces techniques, les installations appropriees, ['utilisation el le pretraitement des oulils d'echantillonnage, les interactions des polluants avec ces oulils ainsi que la selection d'outils adequais pour un ensemble de mesures de polluants potentiels, afin de fournir une base et des criteres pour revaluation de developpements recents. Mots-cles : solution de sol, techniques d'echantillonnage des solutions de sols, recipients a suction, application des lysimetres a succion. [Traduit par la Redaction], 1. Introduction The vadose zone contamination due to environmental pollutants such as nutrients, trace metals, colloids and microorganisms, pesticides, hormones, pharmaceuticals, and other synthetic organic chemicals is a major environmental [...]

Turfgrass systems have been identified as potential sources of nitrate leaching and subsequent groundwater contamination. The HYDRUS (2D/3D) model was used to quantify nitrate leaching from bermudagrass [Cynodon dactylon (L.) Pers.] and buffalograss [Buchloe dactyloides (Nutt.) Engelm] established by either seed or sod and irrigated with either tailored (defined as reclaimed water with an N concentration of 15 mg L−1) or potable water and fertilized with calcium nitrate. A parameter sensitivity analysis conducted prior to model calibration revealed that soil texture, denitrification rate, and plant uptake all affected nitrate leaching. Simulated nitrate flux matched the experimental data more accurately when denitrification rate varied by soil depth. Moreover, nitrate leaching also differed between turfgrass species and between establishment methods. Leaching was higher from grasses propagated by seed than from sod at the beginning of the establishment period. Increasing the concentration of nitrate in tailored water from 0 to 200 mg L–1 increased concentrations at 50‐cm depths for both species but the increase was significantly higher under buffalograss than bermudagrass and was attributed to lower nutrient uptake and denitrification rates under buffalograss. Nitrate concentrations at 50‐cm depth were significantly higher for coarse sand compared with loamy sand, which was attributed to differences in retention times of the two soil types. Soil texture was even more important than nitrate application rate in predicting nitrate leaching losses and the results of the sensitivity analysis demonstrated that nitrate leaching was affected more by denitrification than by plant uptake. [ABSTRACT FROM AUTHOR]

Perfluoro alkyl acids (PFAAs) are known to bioconcentrate in plants grown in contaminated soils; the potential risk from consuming these plants is currently less understood. We determined that the current daily reference doses (RfDs) of the US Environmental Protection Agency (USEPA) could be met by consuming a single radish grown in soils with a perfluorooctanoic acid (PFOA) concentration of 9.7 ng/g or a perfluorooctane sulfonate (PFOS) concentration of 90.5 ng/g. Using a combination of our own research and literature data on plant uptake of PFAAs from soil, we developed equations for predicting PFAA bioconcentration factors (BCFs) for plant shoot and root tissues grown in soils with a known percentage of organic carbon. This calculated BCF was then applied to 6 scenarios with measured soil PFAA concentrations to estimate PFAA concentrations in plants and potential exposure to humans and animals consuming harvested vegetation. Five of the 6 scenarios showed potential for surpassing USEPA PFAA RfDs at soil concentrations as low as 24 ng/g PFOA and 28 ng/g PFOS. Environ Toxicol Chem 2021;40:832–845. © 2020 SETAC [ABSTRACT FROM AUTHOR]