Nitrate Concentrations In Aquifers Research Articles

Investigation of the impact of the implementation of the coastal aquifer management plan on nitrate pollution in Gaza Strip Aquifer using modeling techniques

Groundwater is the principal source of public water supply and for satisfying the daily water needs. The Gaza strip coastal aquifer is suffering from salinity and contamination due to human activities especially agriculture activities. Although, the nitrate is necessary for agriculture activities it can affect the groundwater quality if leached nitrate from the soil into freshwaters after some time. The main objective of this research is to evaluate the current situation of the Gaza strip coastal aquifer and to predict the nitrate concentrations resulting from agriculture activities over the next twenty years using modelling approach. 3D Numerical groundwater flow modeling was developed to simulate the impacts of transport of nitrate loading from agricultural land on groundwater system using finite difference method GMS 10.4 software (MODFLOW 2005 code and MT3DMS package). Five management scenarios were considered to study the effect of pumping and recharge parameters on the groundwater flow system and the impacts of transport of nitrate loading from agricultural areas on the aquifer. Ten different wells were selected to investigate the impact of management scenarios on the nitrate concentration. All management scenarios indicated that there is a relationship between the water level and nitrate concentration in aquifer therefore the rates of nitrate concentration in the southern regions of Gaza strip is more than the northern regions.

Source apportionment of nitrates in different aquifers in an arid region, northwestern China

The nitrate pollution of groundwater in arid areas subject to human activity, and especially agricultural activity, is of immense environmental concern. Groundwater is the main water source in arid areas, once an aquifer is polluted, the impact upon the security of the water supply becomes all the more serious. The process of nitrate transformation is also different from that of humid areas, therefore, it is very important to identify and quantify the nitrate sources in aquifers. Using the hydrochemical, stable isotope tracers of 194 groundwater samples, and combining these with the MixSIAR model, the spatial distribution of groundwater nitrates in the Shiyang River Basin (SRB), China, was mapped. The relative contributions made by nitrate sources to different aquifers, and their key transformation processes, were identified. It was found that, shallow groundwater is seriously polluted, with NO3− concentrations ranging from 1.1 to 438.7 mg L−1. In the SRB, NO3− concentrations of 23% and 73% in shallow groundwater samples exceed the NO3− concentration limits found in natural sources (13.3 mg L−1), and the World Health Organization (WHO) nitrate limits for drinking water (50 mg L−1). Furthermore, the nitrates found in confined aquifers indicate that these are also affected by anthropogenic sources, with concentrations ranging from 1.6 to 44.7 mg L−1. Soil organic nitrogen (51.9%) and NH4+ fertilizer (20.8%), wastewater and manure (20.5%) are the main sources of groundwater nitrates; NO3− fertilizer (4.4%) and precipitation (2.3%) have a relatively insignificant effect on groundwater nitrates. The process of nitrification is the main factor affecting changes in nitrate concentrations in aquifers. Other than the denitrification observed in the shallow aquifers of the Minqin Basin (MQB), there was no significant denitrification in the other sub-basins of the SRB. Anthropogenic sources, especially agricultural sources, are now major contributors to the increases in groundwater nitrate concentrations observed in the SRB. This study provides data that can be used to help prevent groundwater pollution and enhance water resources management in arid areas.

What do we need to predict groundwater nitrate recovery trajectories?

Nitrate contamination affects many of the Earth's aquifers and surface waters. Large-scale predictions of groundwater nitrate trends normally require the characterization of multiple anthropic and natural factors. To assess different approaches for upscaling estimates of nitrate recovery, we tested the influence of hydrological, historical, and biological factors on predictions of future nitrate concentration in aquifers. We tested the factors with a rich hydrogeological dataset from a fractured bedrock catchment in western France (Brittany). A sensitivity analysis performed on a calibrated model of groundwater flow, denitrification, and nitrogen inputs revealed that trends in nitrate concentration can effectively be approximated with a limited number of key parameters. The total mass of nitrate that entered the aquifer since the beginning of the industrial period needs to be characterized, but the shape of the historical nitrogen input time series can be largely simplified without substantially altering the predictions. Aquifer flow and transport processes can be represented by the mean and standard deviation of the residence time distribution, offering a tractable tool to make reasonable predictions at watershed to regional scales. Apparent sensitivity to denitrification rate was primarily attributable to time lags in oxygen depletion, meaning that denitrification can be simplified to an on/off process, defined only by the time needed for nitrate to reach the hypoxic reactive layer. Obtaining these key parameters at large scales is still challenging with currently available information, but the results are promising regarding our future ability to predict nitrate concentration with integrated monitoring and modeling approaches.

Real-time monitoring of nitrate in soils as a key for optimization of agricultural productivity and prevention of groundwater pollution

Abstract. Lack of real-time information on nutrient availability in cultivated soils inherently leads to excess application of fertilizers in agriculture. As a result, nitrate, which is a soluble, stable, and mobile component of fertilizers, leaches below the root zone through the unsaturated zone and eventually pollutes the groundwater and other related water resources. Rising nitrate concentration in aquifers is recognized as a worldwide environmental problem that contributes to water scarcity. The development of technologies for continuous in situ measurement of nitrate concentration in soils is essential for optimizing fertilizer application and preventing water resource pollution by nitrate. Here we present a conceptual approach for a monitoring system that enables in situ and continuous measurement of nitrate concentration in soil. The monitoring system is based on absorbance spectroscopy techniques for direct determination of nitrate concentration in soil porewater without pretreatment, such as filtration, dilution, or reagent supplementation. A new analytical procedure was developed to improve measurement accuracy while eliminating the typical measurement interference caused by soil dissolved organic carbon. The analytical procedure was tested at four field sites over 2 years and proved to be an effective tool for nitrate analysis when directly applied on untreated soil solution samples. A soil nitrate-monitoring apparatus, combining specially designed optical flow cells with soil porewater-sampling units, enabled, for the first time, real-time continuous measurement of nitrate concentration in soils. Real-time, high-resolution measurement of nitrate concentration in the soil has revealed the complex variations in soil nitrate concentrations in response to fertigation pattern. Such data are crucial for optimizing fertilizer application and reducing pollution potential of groundwater.

An interference-tolerant nitrate smart sensor for Wireless Sensor Network applications

As a major contaminant in ground water, nitrate determination is a common practice in environmental analysis, especially the continuous and simultaneous monitoring of its concentration at many different points. For this task, sensor networks are a promising tool, although they require the use of sensors with special features, such as those of Ion Selective Electrodes (ISEs). Unfortunately, their measurements are – to a greater or lesser extent – affected by the presence of other coexisting (interfering) ions. A new methodology is then proposed in this work to deal with major interferences (chloride and bicarbonate in the case of nitrate determination), in such a way that the results obtained in the measurements of the content of NO3− with a nitrate selective electrode can be considered as virtually error-free from these interferences. For this purpose, a new sensor node has been developed; it consists of three ISEs (NO3−, Cl−, and HCO3−) coupled to a low-consumption, low-cost microcontroller (a small chip containing all the computer components), which receives and processes all signals coming from the electrodes. This information is suitably treated, as described in detail in this paper, to provide an accurate estimation of the true value of NO3− concentration.The application of this methodology results in an interference-tolerant nitrate smart sensor capable of being employed within a Wireless Sensor Network in the continuous monitoring of nitrate concentration in aquifers and rivers.

Are groundwater nitrate concentrations reaching a turning point in some chalk aquifers?

In past decades, there has been much scientific effort dedicated to the development of models for simulation and prediction of nitrate concentrations in groundwaters, but producing truly predictive models remains a major challenge. A time-series model, based on long-term variations in nitrate fertiliser applications and average rainfall, was calibrated against measured concentrations from five boreholes in the River Frome catchment of Southern England for the period spanning from the mid-1970s to 2003. The model was then used to “blind” predict nitrate concentrations for the period 2003–2008. To our knowledge, this represents the first “blind” test of a model for predicting nitrate concentrations in aquifers. It was found that relatively simple time-series models could explain and predict a significant proportion of the variation in nitrate concentrations in these groundwater abstraction points ( R 2 = 0.6–0.9 and mean absolute prediction errors 4.2–8.0%). The study highlighted some important limitations and uncertainties in this, and other modelling approaches, in particular regarding long-term nitrate fertiliser application data. In three of the five groundwater abstraction points (Hooke, Empool and Eagle Lodge), once seasonal variations were accounted for, there was a recent change in the generally upward historical trend in nitrate concentrations. This may be an early indication of a response to levelling-off (and declining) fertiliser application rates since the 1980s. There was no clear indication of trend change at the Forston and Winterbourne Abbas sites nor in the trend of nitrate concentration in the River Frome itself from 1965 to 2008.

Impact of Nitrogen Fertilization on Soil and Aquifers in the Humid Pampa, Argentina

There is great concern worldwide about air and water pollution arising from N-fertilizer. Considering the expansion of agriculture and fertilization practices in Argentina, the objective of this study was to determine the effect of Nfertilizers on soil N dynamics and then relationship with nitrate concentration in aquifers. Soil samples were taken during a maize crop cycle in two agricultural farms under different fertilization treatments: UAN (urea, ammonium nitrate and ammonium tiosulfate, 110 kg N ha-1); and UREA (urea, 60 kg N ha-1). UAN and UREA treatment produced an increase in soil nitrate content (from 6 to 550 and 60 mg N kg-1 respectively) and the 71% of aquifers sampled exceeded 45 mg l-1. Our results indicate that uan application produced great N losses and did not increase soil residual N, suggesting that the high amount of nitrates in aquifers would arise from the soil N losses.