Vertical Distribution Of Nitrate Research Articles

Note on the unparallel vertical distribution of nitrate and sulfate in Mollisols

AbstractSoil fertility diagnosis often omits subsoil measurements, impacting precision. Our objective was to compare the vertical distribution of nitrate and sulfate in agricultural Mollisols. Both anions were measured in 34 Mollisols of the Pampean region (Argentina) sampled to 160‐cm depth at 20 cm intervals. Nitrate exhibited a continuous downward trajectory, with maximum values at 0–20 cm (12.7 mg N kg−1) and minimum values at 140–160 cm (3.3 mg N kg−1). Sulfate displayed a sinuous pattern, with a minimum at 60–80 cm (3 mg S kg−1). The 60–160/0–160 cm concentration ratio was 42% for nitrate and 60% for sulfate, indicating greater topsoil stratification for nitrate. Predicting deep‐layer nitrate concentrations from topsoil data was more accurate than for sulfate. This poses a challenge for assessing soil S bioavailability, as subsoil sulfates go undetected in conventional sampling.

Vertical Distribution of Nitrate, Phosphate, and Abundance of Planktonic Diatoms in Pandan Waters, Tapanuli Tengah Regency, North Sumatra

This research was conducted in February 2021 in Pandan Waters, Central Tapanuli Regency, North Sumatra Province. The purpose of this study was to analyze the concentration of nitrate and phosphate, analyze the composition distribution and abundance of planktonic diatoms, and analyze the relationship between nitrate and phosphate concentrations with an abundance of planktonic diatoms at different depths in Pandan Waters. The method used is the survey method. The results of the analysis of vertical concentrations of nitrate and phosphate in Pandan waters tend to increase with increasing depth, while the results of vertical analysis of planktonic diatom abundance in Pandan waters tend to decrease with increasing depth. The results of a simple linear regression test showed that the relationship between nitrate concentration and abundance of planktonic diatoms at different depths had a strong (negative) relationship, while the relationship between phosphate concentration and planktonic diatom abundance at different depths had a very weak (negative) relationship

Nutrient Distribution in Eastern Indonesian Waters

Nutrients are needed for the growth of phytoplankton as a basic component in the marine food web. The concentration of nutrients in waters relates to primary productivity and it will influence fisheries stocks. So far, research on nutrients in the deep sea is rarely carried out in Indonesia. This study aims to determine water quality, horizontal and vertical distribution of nutrients in eastern Indonesian waters, which can be used as baseline data for deep-sea nutrients in Indonesia. The study was conducted from October 29 to November 15, 2017. Sampling was carried out in 20 stations with seven layers. Nutrient measurements were conducted based on Strickland and Parsons (1972). Our results showed that the concentrations of phosphate, nitrate, nitrite, ammonium, and silicate ranged from 0.000-0.060 mg/l, 0.001-0.321 mg/l, 0.000-0.009 mg/l, 0.004-0.024 mg/l and 0.085-1.090 mg/l, respectively. In general, the highest concentration of nutrients was found in Maluku Sea. The vertical distribution of nitrate, phosphate, and silicate shows that the increasing concentrations as increasing depth, except for nitrite and ammonium. The maximum nitrite concentration appears in the northern area, while the ammonium distribution has homogenous pattern.

Sensitivity of nitrate concentration‐discharge patterns to soil nitrate distribution and drainage properties in the vertical dimension

We propose a conceptual model that examines the ‘variable source area’ (VSA) and ‘nitrate flushing’ hypothesis in the vertical direction, and use this approach to explain nitrate concentration–discharge relationships in a semi-arid watershed. We use an eco-hydrology simulation model (RHESSys) to show that small changes in the vertical distribution of nitrate mass and their interaction with soil hydraulic conductivity can result in abrupt changes in the nitrate concentration–discharge relationship. We show that the estimated concentration–discharge relationship is sensitive to the parameters governing soil vertical nitrate distribution and soil hydraulic conductivity, at both patch scale and watershed scale, where lateral redistribution of water and nitrate is also accounted for. Given heterogeneity in nitrogen inputs, uptake processes, soil drainage and storage processes, substantial variation in parameters that describe rate of changes in vertical distribution of soil nitrate and hydraulic properties is likely both within and between watersheds. Thus, we argue that vertical ‘variable source area’ processes may be as important as lateral VSA in determining concentration discharge relationships.

Hybrid Multilevel System for Monitoring Groundwater Flow and Agricultural Impacts in Fractured Sedimentary Bedrock

AbstractUnderstanding agricultural contamination in bedrock aquifers is challenging due to complexity of fracture networks and limitations in data acquisition imposed by instrumentation and drilling costs. Engineered assemblages known as multilevel monitoring systems (MLSs) maximize data from each borehole by providing numerous, depth‐discrete monitoring intervals for profiles of hydraulic head and hydrochemistry. This article describes a hybrid MLS that uses key components of the Waterloo MLS, with extra piezometers of sufficient diameter to accommodate removable transducers for continuous pressure monitoring, attached to the outside using custom clamps. Monitoring intervals are created with sand packs separated by bentonite seals, either via backfilling from surface or tremie placement. The hybrid MLS is best suited for use in rotary drilled boreholes 12 to 15 cm diameter, smaller holes have insufficient space for the MLS and added piezometer(s) while larger holes have excessive backfill material and purge requirements. Variations were installed to 60 m depth in sandstone in Prince Edward Island, and to 150 m in dolostone in southwestern Ontario. Transducers in the external piezometers provided temporal head data under ambient and stressed conditions in key intervals, and manual measurements in all ports provided detailed vertical hydraulic snapshots. Combined with hydrochemistry profiles from groundwater sampling, the hybrid MLS provided detailed composite datasets for interpreting flow and transport in these bedrock aquifers. The hybrid MLS offers promise as a versatile low‐cost option for groundwater studies in agricultural areas providing improved insights on groundwater flow systems and vertical distribution of nitrate and other contaminants, allowing more informed management decisions.

Nitrate dynamics in the soil and unconfined aquifer in arid groundwater coupled ecosystems of the Monte desert, Argentina

[1] In arid ecosystems, vegetation controls water and nitrate movement in the soil, reducing solute transport to aquifers. Here we analyzed nitrate distribution and transport throughout the soil profile and to the groundwater under different ecologic (vegetation type) and topographic (upland/lowland) situations across sand dune ecosystems with shallow water tables, subject to domestic grazing in the Monte desert. Based on vertical nitrate distributions in deep soil profiles we found that dune uplands (deep groundwater, low productivity) lost relatively more nitrogen than lowlands (shallow groundwater, high productivity), likely reinforcing productivity contrasts along these topographic positions. The traditional practice of nighttime animal concentration in corrals may affect nitrogen transport, with poorly vegetated interdunes at livestock posts showing higher subsoil nitrate concentrations than a well-vegetated nonsettled interdune. Vegetation left its imprint on the vertical distribution of nitrate, as suggested by the presence of a depletion zone that matched the depth of maximum root densities, followed by an underlying zone of accumulation. To explore how nitrogen exports to groundwater could affect water quality and nutrient supply to phreatophyte plants, we characterized groundwater flow patterns based on a potentiometric map and sediment characteristics, and measured groundwater electric conductivity, nitrate and arsenic concentration, and stable isotopes across 29 wells (5.8–12 m deep). Under the present land use and climate conditions, nitrate leaching does not seem to have an important and widespread effect on water quality. Nitrate concentration exceeded established limits for human consumption (45 mg L−1) in only one well, while arsenic concentration exceeded the established limits (10 μg L−1) in all but one well, reaching extreme values of 629 μg L−1. Yet, our analysis suggests that nitrate exports from corrals can reach the aquifer in localized areas and be transported to the surrounding vegetation in a relatively short time. Vegetation access to groundwater could allow ecosystems to recover part of this nutrient loss, buffering the effects of land use.

Effects of Organic Manure on Nitrate Distribution in Greenhouse Soil over Three Continuous Crop Cultivations

An experiment was conducted on a vegetable planting base in Damintun Town, Xinmin City, Liaoning Province to study the influence of different organic manure rate on nitrate distribution in vertical profile in a greenhouse soil over three continuous crop cultivations of cucumbers, beans and lettuces. The soil was treated with organic manure at five treatments. The results showed that the distribution characteristic was closely related with organic manure rate in the process of plant growth. After harvest of the cucumber and lettuce soil nitrate content of all layers was higher than before planting and the accumulation of nitrate was increased with the application rate of organic manure. When applied into the low amount of organic fertilizer (M1 and M2), no significant phenomenon of nitrate accumulation and leaching occurred. High amount of organic manure rate (M4) increased significantly (P<0.05), especially in 0~40cm soil layer. In the lower layer (60~120cm) of soil different degrees of nitrate leaching took place. The vertical distribution of nitrate before planting and harvest of beans showed that catch crops can effectively reduce the accumulation of nitrate in soil.

Vertical distribution of sub-micron aerosol chemical composition from North-Western Europe and the North-East Atlantic

Abstract. A synthesis of UK based airborne in-situ measurements of aerosol properties representing air masses from North-West Europe and the North-East Atlantic is presented. The major focus of the study is the vertical distribution of sub-micron aerosol chemical composition. Vertical profiles are derived from a Quadrupole Aerosol Mass Spectrometer (Q-AMS). Background sub-micron aerosol vertical profiles are identified and are primarily composed of organic matter and sulphate aerosol. Such background conditions occurred predominantly during periods associated with long-range air mass transport across the Atlantic. These instances may serve as useful model input of aerosol to Western Europe. Increased mass concentration episodes are coincident with European outflow and periods of stagnant/recirculating air masses. Such periods are characterised by significantly enhanced concentrations of nitrate aerosol relative to those of organic matter and sulphate. Periods of enhanced ground level PM2.5 loadings are coincident with instances of high nitrate mass fractions measured on-board the aircraft, indicating that nitrate is a significant contributor to regional pollution episodes. The vertical structure of the sulphate and organic aerosol profiles were shown to be primarily driven by large-scale dynamical processes. The vertical distribution of nitrate is likely determined by both dynamic and thermodynamic processes, with chemical partitioning of gas phase precursors to the particle phase occurring at lower temperatures at the top of the boundary layer. Such effects have profound implications for the aerosol's lifetime and subsequent impacts, highlighting the requirement for accurate representation of the aerosol vertical distribution.

Nitrate pollution and its distribution in the groundwater of Srikakulam district, Andhra Pradesh, India

The complex depositional pattern of clay and sand in most of the areas controlled the vertical and lateral movement of nitrate in groundwater. The variation of nitrate concentration at different groundwater levels and the lateral distribution of nitrate in the groundwater at two sites indicated the filtration of nitrate by clayey formations. A rural agricultural district located in the Vamsadhara river basin, India was selected for studying the lateral and vertical distribution of nitrate in the groundwater and the association of nitrate with other chemical constituents. The nitrate concentrations in the groundwater are observed to vary between below detectable limit and 450 mg NO3/L. The sources for nitrate are mainly point sources (poultry farms, cattleshed and leakages from septic tanks) and non-point sources (nitrogenous fertilisers). The nitrate concentrations are increased after fertiliser applications. However, very high concentrations of nitrate are derived from animal wastes. Relatively better correlations between nitrate and potassium are observed (R = 0.74 to 0.82). The better relationship between these two chemical constituents in the groundwater may be due to the release of potassium and nitrate from both point and non-point sources. The nitrate and potassium concentrations are high in the groundwater from clayey formations.

Transformation and transport of nitrogen compounds above the North Sea investigated by aircraft measurements

The aircraft measurements presented here aimed at studying the Mid-European plume entering the North Sea region. They revealed a remarkable difference for the vertical distribution of nitrate and sulphate within the mixing layer. On the average sulphate was found to be more uniformly distributed while nitrate concentrations were enhanced at lower altitudes. This is explained as a result of different emission heights and conversion rates of SO 2 and NO x. An approach to correct for transport phenomena is presented to explain part of the observed horizontal inhomogenities.

Zeitliche und vertikale Nitratverteilung in der ungesättigten und gesättigten Bodenzone grundwassernaher Sandböden Nordwestdeutschlands

Abstract Periodic and Vertical Nitrate Distribution in Unsaturated and in Saturated Zone of Sandy Soils Close to Groundwater in North‐West Germany Investigations into the periodic and vertical distribution of nitrate were conducted in three geologically, pedologically and climatically comparable arable sandy soils lying close to the groundwater zone of the coastal moorlands of N.W. Germany. Periodical and vertical distribution of nitrate was observed in unsaturated and in saturated zones of the soil.The investigation concerns podzol‐brown earths. The depth of the water‐unsaturated zone is 2 to 3 m. The crops in two locations consisted of maize and winter rye; in one location, of maize only. N‐manuring consisted of mineral fertilizers and/or of organic liquid manure. At two locations the investigations were conducted over 3 years, at one location, over 18 months.The results from the three locations indicate a corresponding clear variability of nitrate amounts in the soil depending on weather conditions, on the course of growth of the crops, and on the date, the rate and the type of manuring.The dependence of nitrate content on the time span is most clearly expressed in the top soil. The peak values of NO3 in the top soil appear in May, June and in the autumn months. Nitrate peaks in the top soil are continued in the subsequent ground levels with a time shift. Underneath the root zone, the nitrate peak values are transferred, largely without losses, by the seepage water through the capillary and groundwater zones close to the surface.In the capillary and groundwater zones the nitrate peak values are characterized by time‐dependent extension.The time‐span for transferring nitrate peak values from the top soil down to 4.00 m under the surface was determined to be approximately 6‐8 months.

Simulated nitrogen dynamics and losses in a layered agricultural soil

A soil nitrogen model emphasizing mineral nitrogen dynamics and losses is presented. The model has a one-dimensional layered structure and considers plant uptake, mineralization, immobilization, leaching and denitrification processes. Fertilization and manure additions are included as management inputs. A physically based soil-water and heat model provides daily values of temperature, unfrozen water content, water flow and drainage, at different depths in the profile. Input data requirements include standard meteorological variables, basic soil physical and biological properties and crop management characteristics. Soil nitrogen dynamics were simulated for a 3-year period in N-fertilized and unfertilized barley. Model predictions were compared with measurements of nitrate leaching and mineral N content of the soil. Simulation of mineral N levels and leaching generally agreed with field data. Prediction of mineral N dynamics in both N-fertilized and unfertilized barley was better for surface layers than for deeper layers in the profile. Discrepancies between simulated and measured mineral N content in the topsoil were mainly related to mineralization and plant uptake. In deeper soil layers, differences between measured and predicted values were primarily related to the water flow and the drainage pathway. Simulated amounts of nitrate leached were close to measured values. Discrepancies in the temporal distribution of nitrate leached were mainly attributable to the simulated water flow. The model predicted that nitrate leaching to drainage tiles occurred mainly from the upper layers. Prediction of leaching depended as much on the simulation of drainage flow pathways and the vertical distribution of nitrate in the profile as on the simulation of water flow rates.

The vertical distribution of nitrate in open ocean surface water

Near-surface nitrate concentrations in and around warm core ring 82-B were measured using a chemiluminescent technique with a precision of ±2 nM. Concentrations close to the detection limit were encountered in the Sargasso Sea and surface concentrations were below the detection limit of colorimetric techniques (± 50 nM) at all stations. Nitrate concentrations generally increased exponentially with depth. The data are consistent with a concentration-dependent uptake by phytoplankton and a diffusional supply in a one-dimensional vertical model. The constants relating nitrate uptake to nitrate concentration were evaluated from the vertical nitrate distribution, and had time scales of 14 to 140 h. These time scales are appropriate for phytoplankton-mediated processes in the sea. The model demonstrates that phytoplankton uptake of nitrate exerts a control on both the vertical nitrate flux and gradient. Temporal changes in the nitrate content of the euphotic zone at ring center show at least 0.5 gC m −2 nitrate-based productivity in mid-June. Whether or not this change was the end of the spring bloom in the ring is uncertain, but the nitrate-based productivity is high and atypical of the parent Sargasso seawater.

Effects of nitrate on the diurnal vertical migration, carbon to nitrogen ratio, and the photosynthetic capacity of the dinoflagellate Gymnodinium splendens

A non-thecate dinoflagellate, Gymnodinium splendens, was studied in a 12 d laboratory experiment in 2.0x0.25 m containers in which light, temperature, and nutrients could be manipulated. Under a 12 h light: 12 h dark cycle, the dinoflagellates exhibited diurnal vertical migrations, swimming downward before the dark period began and upward before the end of the dark period. This vertical migration probably involved geotaxis and a diel rhythm, as well as light-mediated behavior. The vertical distribution of nitrate affected the behavior and physiology of the dinoflagellate. When nitrate was present throughout the container, the organisms resembled those in exponential batch culture both in C:N ratios and photosynthetic capacity (Pmax); moreover, they migrated to the surface during the day. In contrast, when nitrate was depleted, C:N ratios increased, Pmax decreased, and the organisms formed a subsurface layer at a depth corresponding to the light level at which photosynthesis saturated. When nitrate was present only at the bottom of the tank, C:N ratios of the population decreased until similar to those of nutrient-saturated cells and Pmax increased; however, the dinoflagellates behaved the same as nutrient-depleted cells, forming a subsurface layer during the light period. Field measurements revealed a migratory subsurface chlorophyll maximum layer dominated by G. splendens. It was just above the nitracline during the day, and in the nitracline during the night, which concurs with our laboratory observations.

Steady-state Growth of the Marine Diatom Thalassiosira pseudonana

Seasonal studies of the vertical distribution of nitrate, nitrite, and phytoplankton in the oceans and studies using (15)N as a tracer of nitrate metabolism indicate that the reduction of nitrate by phytoplankton is a source of nitrite in the upper waters of the ocean. To better understand this process, the relationship between nitrate uptake and nitrite production has been examined with continuous cultures of the small marine diatom Thalassiosira pseudonana. In a turbidostat culture, the rates of nitrite production by T. pseudonana increase with light intensity. This process is only loosely coupled to rates of nitrate assimilation since the ratio of net nitrite production to total nitrate assimilation increases with increased rates of growth. In continuous cultures where steady-state concentrations of nitrate and nitrite were varied, T. pseudonana produced nitrite at rates which increased with increasing concentrations of nitrate. Again, the rates of nitrite production were uncoupled from rates of nitrate assimilation. The study was used to derive a mathematical description of nitrate and nitrite metabolism by T. pseudonana.The validity of this model was supported by the results of a study in which (15)N-labeled nitrite was introduced into the continuous culture, and the model was used to examine patterns in distribution of nitrite in the Antarctic Ocean and the Sargasso Sea.

Estimates of denitrification in sediments of the Bering Sea shelf

Denitrification, i.e. anaerobic reduction of nitrate or nitrite to gaseous nitrogen, in the surface sediments of the Bering Sea was estimated using a 15 N-tracer method. N 2 production is apparently controlled by the supply of nitrate and nitrite to the sediments. The average rate of N 2 production in three locations was 1.2 ng-atoms N (g dry weight of sediment) −1 h −1 . The rate of nitrate reduction estimated from the vertical distribution of nitrate in the sediments using a one-dimensional diffusion model agreed well with observed rates of N 2 production. The annual loss of combined nitrogen by denitrification in the Bering Sea shelf was estimated to be 5 × 10 11 g.