Terms Of Nitrate Concentrations Research Articles

PREDICTION OF NITRATE CONCENTRATION IN GROUNDWATER USING MLR AND AGRICULTURAL INDICATORS

Environmental pollution results in the degradation of all segments of nature. Groundwater, as one of thesignificant sources of drinking water at the global level, is increasingly exposed to various types of pollutants thatare mainly the result of anthropogenic action. Nitrate are one of the pollutants that can persist for a long time ingroundwater and their concentrations can reach high levels. Namely, the fact that groundwater is used for variouspurposes such as: irrigation, food production, drinking, special attention is focused on monitoring the concentrationof nitrate in groundwater. In this sense, EU legislation also prescribed a standard for drinking water in terms ofnitrate concentration in order to avoid possible threats to human health. The main sources of nitrate in groundwaterare agricultural activities, which primarily involve the use of chemical fertilizer, animal farms, waste water fromindustries that produce chemical fertilizer. In this paper, the prediction of average annual concentrations of nitrate ingroundwater at the national level was performed. Bearing in mind the mentioned sources of nitrate in groundwater, atotal of seven agricultural indicators were selected in this paper, which were assumed to contribute to higher nitrateconcentrations, namely: the area used for agriculture, meat production on farms, the balance of indicators - whichrepresents the total potential environmental risk caused by excess or deficit of N and P in agricultural soils, areaused for organic agricultural production, consumption of chemical fertilizer, sale of pesticides and percentage ofpopulation associated with at least secondary wastewater treatment. The prediction was made using multiple linearregression, where agricultural indicators were used as input parameters, i.e. independent variables, a total of seven,while the dependent variable was the average annual concentration of nitrate in groundwater at the national level. Inthis paper, five EU countries were selected for nitrate prediction: Belgium, Bulgaria, the Czech Republic, Germanyand France. For the development of the MLR (Multiple linear regression) model, available data from 2011 to 2015were used for all eight variables. Before developing the model, a correlation analysis was first performed todetermine whether the selected independent variables were correlated with the dependent variable. The results of thecorrelation analysis showed that there is a significant correlation between the independent and dependent variables.The developed MLR model showed good prediction results with a value of coefficient of determination R2 - 0.96.The results of the one year prediction by the MLR model showed satisfactory results, the biggest deviations betweenthe measured and model predicted values are in the case of Germany and France. Based on the obtained results, itcan be concluded that the MLR model can be applied as one of the alternatives in the assessment of nitrateconcentration in groundwater.

Water Quality Assessment of Ekulu and Asata Rivers in Enugu Area, Southeastern Nigeria, Using Physico-Chemical and Bacteriological Parameters

This study was aimed at assessing the impacts of human activities on the quality of Ekulu and Asata Rivers in Enugu Area, Southeastern Nigeria. Twelve (12) water samples six (6) from Ekulu River and (six 6) from Asata River) were collected at different points along the regime of the two rivers and their physico-chemical and bacteriological characteristics/parameters determined. Results of the study indicate that the two rivers do not satisfy the Drinking Water Quality Standard of World Health Organization (WHO) and Federal Ministry of Environment (FMENV) in terms of pH/acidity (values between 4.5 and 7.0 and outside the WHO Standard of 6-5-8-5); turbidity (values between 7.88 and 294NTU units and greater than WHO standard of 5.0NTU units); iron (values between 3.10 and 7.35 mg/1 and greater than WHO standard of below 0.30mg/l; and coliform (values between 20 and 180 counts per 100ml and greater than WHO Standard of 3 counts per 100ml). Though Ekulu River is more acidic (lower pH values), more turbid (higher NTU units) and contains higher concentration of iron than Asata River. On the other hand, only Asata River do not satisfy the WHO Standards in terms of nitrate concentration (values between 8.9 and 25.9mg/l and greater than WHO Standard of 10 mg/1): and chromium (heavy metal, values between 0.189 and 0.429 mg/1 and greater than WHO Standard of 0.00lmg/1) Human activities of mining at abandoned Onyeama Coal Mine, car watch and disposal of industrial/domestic wastes are believed to be responsible for poor water quality of the two rivers in Enugu area. On the basis of Piper Diagram Classification, Ekulu River may be classified as Calcium Chloride Type, while Asata River may be classified as Mixed Water Type. Water from the two rivers, to be used for domestic and industrial purposes, should be adequately treated; and there is need to institute regular water quality monitoring programme for the two rivers. Keywords: Water Quality, Ekulu River, Asata River, Enugu Area, Assessment, Piper Diagram DOI: 10.7176/JEES/11-4-07 Publication date: April 30 th 2021

Modeling an in-situ hydrogenotrophic denitrification and oxidation process in an experimental scale aquifer

This paper presents a mathematical model for an in-situ hydrogenotrophic denitrification and oxidation process in an experimental scale aquifer. This model was developed to investigate the stable denitrification performance of the aquifer as well as the effects of varying the molar ratio of nitrate load to hydrogen gas injection (N/H ratio) on the effluent quality in terms of nitrate and nitrite concentrations under a long-term operation. The model could fairly predict the effluent quality in terms of nitrate and nitrite concentrations in the aquifer, in response to the sudden decrease in H2 gas injection as well as different N/H ratios. Furthermore, the model clearly demonstrated that denitrification and nitrification proceeded in each zone injected with H2 gas or O2 gas, respectively, and that stable treatment can be achieved. There were some differences between the experimental data and the model results for nitrate, nitrite, dissolved oxygen, and dissolved hydrogen at the H2-injection zone, implying that mass transfer rates in biofilm should be taken into consideration for more precise modeling. A sensitivity analysis showed that effluent quality in terms of nitrate concentration was the most sensitive to changes in maximum nitrate and nitrite utilization rates.

Green microalgae in marine coastal waters: The Ocean Sampling Day (OSD) dataset

The ecology and distribution of green phytoplankton (Chlorophyta) in the ocean is poorly known because most studies have focused on groups with large cell size such as diatoms or dinoflagellates that are easily recognized by traditional techniques such as microscopy. The Ocean Sampling Day (OSD) project sampled surface waters quasi-simultaneously at 141 marine locations, mostly in coastal waters. The analysis of the 18S V4 region OSD metabarcoding dataset reveals that Chlorophyta are ubiquitous and can be locally dominant in coastal waters. Chlorophyta represented 29% of the global photosynthetic reads (Dinoflagellates excluded) and their contribution was especially high at oligotrophic stations (up to 94%) and along the European Atlantic coast. Mamiellophyceae dominated most coastal stations. At some coastal stations, they were replaced by Chlorodendrophyceae, Ulvophyceae, Trebouxiophyceae or Chlorophyceae as the dominating group, while oligotrophic stations were dominated either by Chloropicophyceae or the uncultured prasinophytes clade IX. Several Chlorophyta classes showed preferences in terms of nitrate concentration, distance to the coast, temperature and salinity. For example, Chlorophyceae preferred cold and low salinity coastal waters, and prasinophytes clade IX warm, high salinity, oligotrophic oceanic waters.

Tomography of anthropogenic nitrate contribution along a mesoscale river

Elevated nitrate concentrations are a thread for water supply and ecological integrity in surface water. Nitrate fluxes obtained by standard monitoring protocols at the catchment outlet strongly integrate spatially and temporally variable processes such as mobilization and turnover. Consequently, inference of dominant nitrate sources is often problematic and challenging in terms of effective river management and prioritization of measures. Here, we combine a spatially highly resolved assessment of nitrate concentration and fluxes along a mesoscale catchment with four years of monitoring data at two representative sites. The catchment is characterized by a strong land use gradient from pristine headwaters to lowland sub-catchments with intense agricultural land use and wastewater sources. We use nitrate concentrations in combination with hydrograph separation and isotopic fingerprinting methods to characterize and quantify nitrate source contribution.The hydrological analysis revealed a clear dominance of base flow during both campaigns. However, the absolute amounts of discharge differed considerably from one another (outlet: 1.42m3s−1 in 2014, 0.43m3s−1 in 2015). Nitrate concentrations are generally low in the pristine headwaters (<3mgL−1) and increase downstream (15 to 16mgL−1) due to the contribution of agricultural and wastewater sources. While the agricultural contribution did not vary in terms of nitrate concentration and isotopic signature between the years, the wastewater contribution strongly increased with decreasing discharge. Wastewater-borne nitrate load in the entire catchment ranged between 19% (2014) and 39% (2015). Long-term monitoring of nitrate concentration and isotopic composition in two sub-catchment exhibits a good agreement with findings from spatially monitoring. In both datasets, isotopic composition indicates that denitrification plays only a minor role. The spatially highly resolved monitoring approach helped to pinpoint hot spots of nitrate inputs into the stream while the long-term information allowed to place results into the context of intra-annual variability.

Hydrogeophysical investigations of the former S-3 ponds contaminant plumes, Oak Ridge Integrated Field Research Challenge site, Tennessee

At the Oak Ridge Integrated Field Research Challenge site, near Oak Ridge, Tennessee, contaminants from the former S-3 ponds have infiltrated the shallow saprolite for over 60 years. Two- and three-dimensional DC-resistivity tomography is used to characterize the number and location of the main contaminant plumes, which include high concentration of nitrate. These contaminant plumes have typically an electrical resistivity in the range 2–20 ohm-m while the background saprolite resistivity is in the range 60–120 ohm-m, so the difference of resistivity can be easily mapped using DC-resistivity tomography to locate the contaminant pathways. We develop a relationship to derive the in situ nitrate concentrations from the 3D resistivity tomograms accounting for the effect of surface conductivity. The footprint of the contamination upon the resistivity is found to be much stronger than the local variations associated with changes in the porosity and the clay content. With this method, we identified a total of five main plumes (termed CP1 to CP5). Plume CP2 corresponds to the main plume in terms of nitrate concentration (∼50,000 [Formula: see text]). We also used an active time constrained approach to perform time-lapse resistivity tomography over a section crossing the plumes CP1 and CP2. The sequence of tomograms is used to determine the changes in the nitrate concentrations associated with infiltration of fresh (meteoritic) water from a perched aquifer. This study highlights the importance of accounting for surface conductivity when characterizing plume distributions in clay-rich subsurface systems.

Long-term electrical resistivity monitoring of recharge-induced contaminant plume behavior

Geophysical measurements, and electrical resistivity tomography (ERT) data in particular, are sensitive to properties that are related (directly or indirectly) to hydrological processes. The challenge is in extracting information from geophysical data at a relevant scale that can be used to gain insight about subsurface behavior and to parameterize or validate flow and transport models. Here, we consider the use of ERT data for examining the impact of recharge on subsurface contamination at the S-3 ponds of the Oak Ridge Integrated Field Research Challenge (IFRC) site in Tennessee. A large dataset of time-lapse cross-well and surface ERT data, collected at the site over a period of 12months, is used to study time variations in resistivity due to changes in total dissolved solids (primarily nitrate). The electrical resistivity distributions recovered from cross-well and surface ERT data agrees well, and both of these datasets can be used to interpret spatiotemporal variations in subsurface nitrate concentrations due to rainfall, although the sensitivity of the electrical resistivity response to dilution varies with nitrate concentration. Using the time-lapse surface ERT data interpreted in terms of nitrate concentrations, we find that the subsurface nitrate concentration at this site varies as a function of spatial position, episodic heavy rainstorms (versus seasonal and annual fluctuations), and antecedent rainfall history. These results suggest that the surface ERT monitoring approach is potentially useful for examining subsurface plume responses to recharge over field-relevant scales.

Nutritional quality of greenhouse lettuce at harvest and after storage in relation to N application and cultivation season

The effect of five levels of nitrogen fertilization on the growth and nutritional quality of Cos lettuce ( Lactuca sativa L. cv. Parris Island) at harvest and after storage was studied during autumn and winter in South-West Greece. Plants were cultivated hydroponically in a greenhouse and the nitrate, chlorophyll and ascorbic acid (vitamin C) concentrations within the plant tissues were measured at harvest and following storage at 5 or 10 °C for 10 days. Nitrate accumulated in the leaves with increasing amounts of N within the nutrient solution and was higher in the winter than in the autumn. At the lowest N level (20 mg L −1), the inner leaves accumulated more nitrate than the outer leaves, whereas at higher N levels (140, 200 or 260 mg L −1) nitrate accumulation was higher in the outer leaves. Overall, the highest nitrate concentrations were detected in the petiole and the proximal end of the leaf, but at the lowest N application rate (20 mg L −1) nitrate accumulated in the distal region of the leaf too. Although the nitrate concentrations within the leaves did not change significantly during 10 days storage at 5 or 10 °C, the chlorophyll and vitamin C concentrations decreased. Chlorophyll loss was higher in lettuce that was grown under low N levels and was higher at 10 °C than at 5 °C, but was reduced by enclosure of the lettuce in polyethylene film. It is concluded that the optimum N application rate for Cos lettuce grown hydroponically under cover during autumn and winter in South-West Greece, and in other areas with a similar climate, is 200 mg N L −1 because at this N rate yield is satisfactory and leaf nitrate concentrations are below the maximum acceptable level for human consumption. Nutritional value (vitamin C concentration) and market quality (chlorophyll content) are highest at harvest and decrease during storage, but quality in terms of nitrate concentration does not change.

Density–dependent recruitment of Puntius sophore in floodplain waterbodies in Bangladesh

Recruitment of Puntius sophore in floodplain waters of Bangladesh was strongly densitydependent at a range of high stock densities and can be described by a Ricker model. Recruitment at low stock density was correlated strongly with waterbody fertility measured in terms of nitrate concentration. The implications of these results are discussed in terms of community–based management.

Water flow and nitrate transport to a groundwater-fed stream in the Belgian-Dutch chalk region

Human activities, such as high fertilizer applications, groundwater abstractions and land use changes, might have a negative impact on drinking water supply, environment and nature reserves of the chalk region in the Dutch–Belgian boundary area. In this area, the groundwater and surface water systems of the Noor experimental catchment have been monitored intensively and modelled to investigate groundwater flow and the transport of nitrate to groundwater-dominated streams. Groundwater flow towards the riparian area, the springs and Noor brook is strongly controlled by long-term variation of the groundwater recharge. Relatively small, but permanent changes in the recharge have a higher impact on spring flow and stream flow than current groundwater abstraction in this chalk catchment. Land use, groundwater flow patterns and the characteristics of the geological formations result in distinctly different groundwater types and associated nitrate concentrations. High concentrations were found under the plateau (median 55 mg · l−1) and extremely low in the riparian area (median 2 mg · l−1). The springs and thereby the Noor brook are mainly fed by groundwater directly coming from the plateau with a low probability of denitrification. This results in median NOconcentrations which are clearly above the drinking water standard of 50 mg · l−1 (i.e. 68 and 58 mg · l−1). Monitoring and modelling show that the north springs have higher NOconcentrations than the south springs due to different probabilities of denitrification. Nitrate in the groundwater-dominated Noor brook is hardly correlated with the discharge, but the major spring shows a clear upward trend in terms of nitrate concentrations, i.e. an increase by about 30 mg · l−1 from 1980 onwards. A policy of reduced nitrogen application will result in lower nitrate concentrations in the surface water system not earlier than in 10 or 20 years, because of the long travel times of water particles in the unsaturated and saturated zone. The north springs will react earlier than the south springs. Copyright © 1999 John Wiley & Sons, Ltd.