scholarly journals A meta-analysis of groundwater contamination by nitrates at the African scale

2016 ◽  
Author(s):  
Issoufou Ouedraogo ◽  
Marnik Vanclooster
Keyword(s):  
Statistical Model ◽  
Nitrate Concentration ◽  
Regional Scale ◽  
Model Development ◽  
Shallow Groundwater ◽  
Nitrate Pollution ◽  
Nitrate Contamination ◽  
Pan African ◽  
Nitrate Concentrations ◽  
Groundwater Systems

Abstract. Contamination of groundwater with nitrate poses a major health risk to millions of people around Africa. Assessing the space-time distribution of this contamination, as well as understanding the factors that explain this contamination is important to manage sustainable drinking water at the regional scale. This study aims to assess the variables that contribute to nitrate pollution in groundwater at the pan-African scale by statistical modeling. We compiled a literature database of nitrate concentration in groundwater (around 250 studies) and combined it with digital maps of physical attributes such as soil, geology, climate, hydrogeology and anthropogenic data for statistical model development. The maximum, medium and minimum observed nitrate concentrations were analysed. In total, 13 explanatory variables were screened to explain observed nitrate pollution in groundwater. For the mean nitrate concentration, 4 variables are retained in the statistical explanatory model: (1) Depth to groundwater (shallow groundwater, typically < 50 m); (2) Recharge rate; (3) Aquifer type; and (4) Population density. The former three variables represent intrinsic vulnerability of groundwater systems towards pollution, while the latter variable is a proxy for anthropogenic pollution pressure. The model explains 65 % of the variation of mean nitrate contamination in groundwater at the pan-Africa scale. Using the same proxy information, we could develop a statistical model for the maximum nitrate concentrations that explains 42 % of the nitrate variation. For the maximum concentrations, other environmental attributes such as soil type, slope, rainfall, climate class and region type improve the prediction of maximum nitrate concentrations at the pan-African scale. As to minimal nitrate concentrations, in the absence of normal distribution assumptions of the dataset, we do not develop a statistical model for these data. The data based statistical model presented here represents an important step toward developing tools that will allow us to accurately predict nitrate distribution at the African scale and thus may support groundwater monitoring and water management that aims to protect groundwater systems. Yet they should be further refined and validated when more detailed and harmonized data becomes available and/or combined with more conceptual descriptions of the fate of nutrients in the hydro system.

scholarly journals A meta-analysis and statistical modelling of nitrates in groundwater at the African scale

2016 ◽  
Vol 20 (6) ◽  
pp. 2353-2381 ◽  
Author(s):  
Issoufou Ouedraogo ◽  
Marnik Vanclooster
Keyword(s):  
Statistical Model ◽  
Nitrate Concentration ◽  
Regional Scale ◽  
Shallow Groundwater ◽  
Statistical Modelling ◽  
Nitrate Pollution ◽  
Nitrate Contamination ◽  
Data Set ◽  
Nitrate Concentrations ◽  
Groundwater Systems

Abstract. Contamination of groundwater with nitrate poses a major health risk to millions of people around Africa. Assessing the space–time distribution of this contamination, as well as understanding the factors that explain this contamination, is important for managing sustainable drinking water at the regional scale. This study aims to assess the variables that contribute to nitrate pollution in groundwater at the African scale by statistical modelling. We compiled a literature database of nitrate concentration in groundwater (around 250 studies) and combined it with digital maps of physical attributes such as soil, geology, climate, hydrogeology, and anthropogenic data for statistical model development. The maximum, medium, and minimum observed nitrate concentrations were analysed. In total, 13 explanatory variables were screened to explain observed nitrate pollution in groundwater. For the mean nitrate concentration, four variables are retained in the statistical explanatory model: (1) depth to groundwater (shallow groundwater, typically < 50 m); (2) recharge rate; (3) aquifer type; and (4) population density. The first three variables represent intrinsic vulnerability of groundwater systems to pollution, while the latter variable is a proxy for anthropogenic pollution pressure. The model explains 65 % of the variation of mean nitrate contamination in groundwater at the African scale. Using the same proxy information, we could develop a statistical model for the maximum nitrate concentrations that explains 42 % of the nitrate variation. For the maximum concentrations, other environmental attributes such as soil type, slope, rainfall, climate class, and region type improve the prediction of maximum nitrate concentrations at the African scale. As to minimal nitrate concentrations, in the absence of normal distribution assumptions of the data set, we do not develop a statistical model for these data. The data-based statistical model presented here represents an important step towards developing tools that will allow us to accurately predict nitrate distribution at the African scale and thus may support groundwater monitoring and water management that aims to protect groundwater systems. Yet they should be further refined and validated when more detailed and harmonized data become available and/or combined with more conceptual descriptions of the fate of nutrients in the hydrosystem.

scholarly journals ESTIMATION, REALITY AND TREND OF GROUNDWATER NITRATE CONCENTRATION UNDER UNSEWERED AREA OF YOGYAKARTA CITY – INDONESIA

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Doni Prakasa Eka Putra
Keyword(s):  
Water Supply ◽  
Urban Population ◽  
Nitrate Concentration ◽  
Chloride Concentration ◽  
Shallow Groundwater ◽  
Unconfined Aquifer ◽  
Nitrate Contamination ◽  
Sanitation Systems ◽  
The City ◽  
Yogyakarta City

In the last two decades, urbanization has transformed Yogyakarta City expanding beyond its administrative area with about one million inhabitants. The City sited on shallow unconfined aquifer has rapidly changed without appropriate access to sanitation and piped water supply. Until now, only 9% of the urban population is served by sewers system and less than 30% of urban population have access to clean water which supplied by the local public water-work. Most of the urban population depend on shallow groundwater for much of their water supply. Regards to the massive used of on-site sanitation systems in the city, contamination of nitrate in shallow groundwater is predicted to occur and surveys of domestic dug wells have revealed a widespread nitrate contamination of the groundwater. Comparison of groundwater nitrate and chloride concentration from several old data and the latest data shows clearly an evidence of the increasing of nitrate concentration and nitrate leaching in the shallow groundwater under Yogyakarta City overtime. Considering the trend, it is no doubt that most of nitrate concentration under urbanized area in the Yogyakarta City will be greater than 50 mg/L in the next several years, if appropriate management action to deal with the on-site sanitation system is not conducted.

scholarly journals The Characterization of Microbial Communities Response to Shallow Groundwater Contamination in Typical Piedmont Region of Taihang Mountains in the North China Plain

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 736 ◽  
Author(s):  
He ◽  
Ning ◽  
Yang ◽  
Huang ◽  
Cui ◽  
...  
Keyword(s):  
Microbial Diversity ◽  
Microbial Communities ◽  
Dna Sequences ◽  
Regional Scale ◽  
Shallow Groundwater ◽  
Nitrate Contamination ◽  
Cumulative Probability ◽  
Organic Nitrate ◽  
Microbial Indicators ◽  
Piedmont Region

Regional-scale nitrate and organic contaminants in the shallow groundwater were investigated in the Piedmont region of Taihang Mountains (PRTM), but the information of the microbial communities is limited. However, microorganisms provide a dominated contribution to indicate and degrade the contaminants in the aquifer. Therefore, this study investigates the microbial diversity and contamination microbial indicators of groundwater samples with different contaminated types to better understand the contamination in the PRTM. Seventy-six samples were collected between two rivers in the Tang-Dasha River Basin covering 4000 km2 in the PRTM. High-throughput sequencing was employed to determine the samples’ DNA sequences. The samples were divided into four groups: background (B), nitrate contamination (N), organic contamination (O) and organic-nitrate contamination (O_N) based on the cumulative probability distribution and the Chinese groundwater standard levels of NO3−, COD and DO concentrations. Then, the microbial diversity and contamination microbial indicators were studied in the four groups. The results showed that the O group exhibited lower diversity than other groups. Bacteria detected in these four groups covered 531 families, 987 genera, and 1881 species. Taxonomic assignment analysis indicated that Rhodobacter, Vogesella, Sphingobium dominated in the O_N group, N group, and O group, and accounted for 18.05%, 17.74%, 16.45% in each group at genus level, respectively. Furthermore, these three genera were identified as contamination microbial indicators to the three types of contamination, respectively. The results provide a potential molecular microbiological method to identity contamination in shallow groundwater, and established a strong foundation for further investigation and remediation in the PRTM.

scholarly journals Monitoring of nitrate contamination in groundwater: case study of the campus of UNESP, Rio Claro/SP

2019 ◽  
Vol 41 ◽  
pp. e54 ◽  
Author(s):  
Elias Hideo Teramoto ◽  
Pedro Paulo Bazilio da Costa ◽  
Roger Dias Gonçalves ◽  
Bruno Zanon Engelbrecht ◽  
Hung Kiang Chang
Keyword(s):  
Water Quality ◽  
Conceptual Model ◽  
Shallow Groundwater ◽  
Nitrate Contamination ◽  
Septic Tank ◽  
Multiple Sources ◽  
Concentration Gradients ◽  
Nitrate Concentrations ◽  
Sources Of Contamination

This study presents the results of the monitoring of nitrate concentrations in shallow groundwater at the UNESP Campus of Rio Claro/SP assumed to be sourced by septic tank leakage, which were discontinued in October 2014. The distribution of nitrate concentrations provides support to a conceptual model of contamination by multiple sources, since the concentration gradients are not observed along the flowpaths. The results of the monitoring indicate that in some monitored wells, the nitrate concentrations remain stable, while in other wells minor to strong fall trends were observed. These results provide support to the presence of other active sources, such as sewage leakage in the external and internal area of the campus. This scenario perfect fit with the maintenance of recorded high nitrate concentrations over the time. Despite the nitrate concentrations are below potability limit, additional investigations will be conducted to identify sources of contamination to ensure water quality in the future.

scholarly journals Antecedent flow conditions and nitrate concentrations in the Mississippi River basin

2014 ◽  
Vol 18 (3) ◽  
pp. 967-979 ◽  
Author(s):  
J. C. Murphy ◽  
R. M. Hirsch ◽  
L. A. Sprague
Keyword(s):  
River Basin ◽  
Mississippi River ◽  
Nitrate Concentration ◽  
Regional Scale ◽  
Mississippi River Basin ◽  
Flow Conditions ◽  
Daily Streamflow ◽  
Nitrate Concentrations ◽  
High Flows ◽  
The Mean

Abstract. The relationship between antecedent flow conditions and nitrate concentrations was explored at eight sites in the 2.9 million square kilometers (km2) Mississippi River basin, USA. Antecedent flow conditions were quantified as the ratio between the mean daily flow of the previous year and the mean daily flow from the period of record (Qratio), and the Qratio was statistically related to nitrate anomalies (the unexplained variability in nitrate concentration after filtering out season, long-term trend, and contemporaneous flow effects) at each site. Nitrate anomaly and Qratio were negatively related at three of the four major tributary sites and upstream in the Mississippi River, indicating that when mean daily streamflow during the previous year was lower than average, nitrate concentrations were higher than expected. The strength of these relationships increased when data were subdivided by contemporaneous flow conditions. Five of the eight sites had significant negative relationships (p ≤ 0.05) at high or moderately high contemporaneous flows, suggesting nitrate that accumulates in these basins during a drought is flushed during subsequent high flows. At half of the sites, when mean daily flow during the previous year was 50 percent lower than average, nitrate concentration can be from 9 to 27 percent higher than nitrate concentrations that follow a year with average mean daily flow. Conversely, nitrate concentration can be from 8 to 21 percent lower than expected when flow during the previous year was 50 percent higher than average. Previously documented for small, relatively homogenous basins, our results suggest that relationships between antecedent flows and nitrate concentrations are also observable at a regional scale. Relationships were not observed (using all contemporaneous flow data together) for basins larger than 1 million km2, suggesting that above this limit the overall size and diversity within these basins may necessitate the use of more complicated statistical approaches or that there may be no discernible basin-wide relationship with antecedent flow. The relationships between nitrate concentration and Qratio identified in this study serve as the basis for future studies that can better define specific hydrologic processes occurring during and after a drought (or high flow period) which influence nitrate concentration, such as the duration or magnitude of low flows, and the timing of low and high flows.

Agricultural nitrogen reduction requirement to reach groundwater and surface water quality targets in North Rhine-Westphalia, Germany

2020 ◽  
Author(s):  
Ralf Kunkel ◽  
Sabine Bergmann ◽  
Michael Eisele ◽  
Horst Gömann ◽  
Frank Herrmann ◽  
...  
Keyword(s):  
Surface Water ◽  
Transport Model ◽  
Nitrate Concentration ◽  
Nitrate Pollution ◽  
Balance Model ◽  
Federal State ◽  
Nitrate Transport ◽  
Time Period ◽  
Nitrate Concentrations ◽  
The Eu

&lt;p&gt;Excessive nitrate inputs into groundwater have been recognized as a main reason for failing drinking water standards since decades. Agricultural N-emissions originating from mineral or organic fertilizers are regarded as the most relevant source of nitrate in groundwater worldwide. Accordingly, strategies to cope with the nitrate pollution of groundwater are focused on controlling the agricultural sources of nitrate. In Europe this is reflected in the water legislation on EU level, i.e. the EU Water Framework Directive (EU-WFD), the EU Marine Strategy Framework Directive and the EU Nitrates Directive, obliging the polluter to implement measures to reduce the nitrogen impact on groundwater.&lt;/p&gt;&lt;p&gt;With an average population density of 525 inhabitants/km&lt;sup&gt;2&lt;/sup&gt;&amp;#160;the Federal State of North Rhine-Westphalia represents an example for a densely populated region in Germany. Consequently, the assessment of water bodies showed that a number of groundwater and surface water bodies are not in good status due to high nitrogen loads resulting e.g. in high nitrate concentrations in groundwater. There is a debate in North Rhine-Westphalia to what extent agricultural and non-agricultural N-emissions contribute to high nitrate concentrations.&lt;/p&gt;&lt;p&gt;The German Working Group on water issues of the Federal States and the Federal Government, require that the nitrate concentration in the leachate should not exceed 50 mg NO&lt;sub&gt;3&lt;/sub&gt;/l. Against this background it is obvious that the nitrate concentration in the leachate represents a decisive parameter for both, the assessment on the nitrate pollution of groundwater and as starting point to determine the N reduction requirements.&lt;/p&gt;&lt;p&gt;We used an interdisciplinary model network consisting of a nutrient balance model, a nutrient balancing model (RAUMIS, Henrichsmeyer et al., 1996), a water balance model (mGROWA, Hermann et al., 2015), a reactive nitrate transport model in soil (DENUZ, Wendland et al., 2009) and a reactive nitrate transport model in groundwater (WEKU, Kunkel &amp; Wendland, 1997) to predict the nitrogen intakes and the nitrogen losses to groundwater and surface waters from different input sources and pathways.&lt;/p&gt;&lt;p&gt;The nitrogen flux was modelled using nitrogen input data from the time period 2014-2016 and hydrological data for the time period 1981-2010. The nitrate concentrations in the leachate were calculated separately for agricultural and non agricultural N-sources involved, to enable the identification of the main polluter in a certain region, i.e. the one who has to implement measures to to reduce the nitrogen impact on groundwater.&lt;/p&gt;&lt;p&gt;From the model analysis it becomes evident that non-agricultural sources do only locally cause nitrate concentrations in the leachate above 50 mg NO&lt;sub&gt;3&lt;/sub&gt;/l in spite of the high population density (525 inhabitants / km&lt;sup&gt;2&lt;/sup&gt;). It could be confirmed that agricultural sources (N-balance surpluses from agriculture and atmospheric NH&lt;sub&gt;4&lt;/sub&gt; deposition) are exclusively responsible for extended areas of nitrate concentrations above 50 mg NO&lt;sub&gt;3&lt;/sub&gt;/l. Especially in the northern (M&amp;#252;nsterland) and western (Lower Rhine basin) parts of the Federal State the implementation of measures to reduce agricultural N-emissions in the context of the WFD program of measures is necessary. These results will not only support the right dimensioning of agricultural N-reduction measures, but also affect the selection and implementation of regionally adapted N-reduction measures.&lt;/p&gt;

scholarly journals Distribution of Nitrate Household Waste and Groundwater Flow Direction around Code River, Yogyakarta, Indonesia

2019 ◽  
Vol 51 (1) ◽  
pp. 54 ◽  
Author(s):  
Muryanto Muryanto ◽  
Suntoro Suntoro ◽  
Totok Gunawan ◽  
Prabang Setyono ◽  
Afid Nurkholis ◽  
...  
Keyword(s):  
Groundwater Flow ◽  
Nitrate Concentration ◽  
Flow Direction ◽  
Shallow Groundwater ◽  
Household Waste ◽  
Groundwater Samples ◽  
Water Well ◽  
Nitrate Concentrations ◽  
Potential Groundwater ◽  
Yogyakarta City

The nitrate concentrations in shallow groundwater of the Yogyakarta City and its surroundings has increased to about twenty times in the period 1985-2018. The objective of this study was to analyse the distribution of nitrate concentrations in water well around the Code River, Yogyakarta. Flownets mapping was performed to find out the distribution and direction of potential groundwater pollution. Nitrate concentration was analysed by taking 18 groundwater samples scattered in the upstream, midstream and downstream areas of the Code River. The results of this study indicate that nitrate concentrations in the water well of upstream and downstream areas could still be used as a source of drinking water and recreation-irrigation-livestock. Meanwhile, the nitrate concentration in water well of the midstream area of the Code River, Yogyakarta City, mostly (80% of the sample) did not meet all classes of water quality standards. Human activities in the densely populated settlements were the main factors that influence nitrate pollution. Furthermore, groundwater flow in the study area leads from north to south and towards the Code River. This condition indicates that the nitrate concentrations in  the groundwater can be a source of a pollutant for the Code River.

scholarly journals Mobilisation or dilution? Nitrate response of karst springs to high rainfall events

2014 ◽  
Vol 18 (11) ◽  
pp. 4423-4435 ◽  
Author(s):  
M. Huebsch ◽  
O. Fenton ◽  
B. Horan ◽  
D. Hennessy ◽  
K. G. Richards ◽  
...  
Keyword(s):  
High Resolution ◽  
Nitrate Contamination ◽  
Karst Aquifers ◽  
The European Union ◽  
Storm Events ◽  
Discharge Data ◽  
Rainfall Events ◽  
Nitrate Concentrations ◽  
Nitrate Response ◽  
Karst Systems

Abstract. Nitrate (NO3−) contamination of groundwater associated with agronomic activity is of major concern in many countries. Where agriculture, thin free draining soils and karst aquifers coincide, groundwater is highly vulnerable to nitrate contamination. As residence times and denitrification potential in such systems are typically low, nitrate can discharge to surface waters unabated. However, such systems also react quickest to agricultural management changes that aim to improve water quality. In response to storm events, nitrate concentrations can alter significantly, i.e. rapidly decreasing or increasing concentrations. The current study examines the response of a specific karst spring situated on a grassland farm in South Ireland to rainfall events utilising high-resolution nitrate and discharge data together with on-farm borehole groundwater fluctuation data. Specifically, the objectives of the study are to formulate a scientific hypothesis of possible scenarios relating to nitrate responses during storm events, and to verify this hypothesis using additional case studies from the literature. This elucidates the controlling key factors that lead to mobilisation and/or dilution of nitrate concentrations during storm events. These were land use, hydrological condition and karstification, which in combination can lead to differential responses of mobilised and/or diluted nitrate concentrations. Furthermore, the results indicate that nitrate response in karst is strongly dependent on nutrient source, whether mobilisation and/or dilution occur and on the pathway taken. This will have consequences for the delivery of nitrate to a surface water receptor. The current study improves our understanding of nitrate responses in karst systems and therefore can guide environmental modellers, policy makers and drinking water managers with respect to the regulations of the European Union (EU) Water Framework Directive (WFD). In future, more research should focus on the high-resolution monitoring of karst aquifers to capture the high variability of hydrochemical processes, which occur at time intervals of hours to days.

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