Maximum Nitrate Concentration Research Articles

Sulfur autotrophic electrodialysis ion exchange membrane bioreactor (SEDIMB) for nitrate removal in water: Synergism and adaptability of electrodialysis and sulfur autotrophy

In this study, the novel sulfur autotrophic electrodialysis ion-exchange membrane bioreactor (SEDIMB) with high denitrification performance was developed without the addition of carbon source. Sulfur autotrophic denitrification occurs at the same time of nitrate enrichment by electric field to achieve harmless nitrate transformation in water. The final nitrate concentration in water chamber was 2.16 mg-N/L (removal efficiency of 94.49 %) at an initial nitrate concentration of 40 mg-N/L, with the maximum nitrate concentration in biological chamber of 4.09 mg-N/L. Nitrate removal in water chamber of the SEDIMB conformed to the first-order kinetic model (R2 = 0.98) and reaction rate constant K1 = 0.0030 (1/min). The effect of environmental variables (i.e., voltage, initial nitrate concentration and water body) on the SEDIMB denitrification performance was investigated. Increasing voltage could promote nitrate migration in water chamber, and when the voltage was 7 V, initial nitrate concentrations of 20 ∼ 60 mg-N/L was effectively removed (all > 93.54 %). Moreover, the change of water body (i.e., tap water, lake water and deionized water) did not affect denitrification performance of SEDIMB. Microbial community structure analysis indicated that Betaproteobacteria were dominant in the SEDIMB. Membrane characterizations (ATR-IR, SEM and CLSM) confirmed that the bacteria in biological chamber tended to accumulate and grow on one side of the anion exchange membrane (AEM), while could not affect the selective permeability of AEM.

Groundwater Contamination with Nitrate and Human Health Risk Assessment of North East Alluvial Plains of Bihar, India

Groundwater is natural resources which supplies almost half of all drinking water in the world and plays a key role in food production. Consuming water containing high nitrate concentration have immediate effect on infant and could cause the risk of diseases Methemoglobinemia in which blood lacks the ability to carry sufficient oxygen to the individual body cells. As difference in nitrate concentration in water, made it important to study the undesirable effect of it. In rural areas, groundwater contamination is a problem related to the excessive use of chemical fertilizers by local farmers. Shallow groundwater plays a vital role in water use and the yield of Maize. Nitrogen application significantly affects crop uptake and utilization of water from irrigation, but little is known about groundwater use. Farmers are applying nitrogen on an average 278 kg/ha in Kharif maize, which is about 131.72% more than the RDN of Kharif maize i.e. 120 KgN/ha. The mean value of N application by farmers ranges from 251-323 kg/ha. The Maximum rate of N application was observed in Khagaria (323 kg N/ha) followed by Madhepura (275.08 kg N/ha) and minimum in case of Saharsa district (251.16 kg N/ha). The application rate of nitrogenous fertilizer, varying from 109.25% to 169.16% over the RDN, resulting in NO3- leaching. The groundwater and surfacewater from 12 villages was collected and various quality parameters were analysed. The nitrate in ground water varied (1.87- 6.19 mg/L) and surface water (1.87 – 3.84 mg/L) being maximum concentration of nitrate in Madhepura district. The present study on nitrate leaching in soil, its level of contamination in ground water and human health risk assessment by chronic daily intake of nitrate and Hazard Quotient (H.Q) values in the study area of Khagaria, Saharsa, Madhepura and Supaul has been carried out in the eastern alluvial region of Bihar.

A Comprehensive Assessment of Water Quality and Mass Balance of the Bhairab River, Khulna

Abstract: Water is a vital component for all organisms on Earth. Water is essential for the survival of all living organisms on Earth. Water is vital for life, much like oxygen, since no kind of life can survive without it. Water often includes several physical, chemical, and biological contaminants. Surface water sources mostly consist of rivers, lakes, ponds, glaciers, and precipitation. The sources are becoming degraded due to contemporary urbanization, escalating population, domestic trash, and industry. The Bhairab River is not far from the sick worry. The water quality of the area is rapidly deteriorating due to the significant influx of contaminants it gets. This research focuses on evaluating the water quality and mass balance of the Bhairab River. In order to achieve the current objective of the research, a stretch of 22.9 kilometers from Jailkhana Ferighat to Shuvorada Kheya Ghat, Fultola, was split into 10 sample sites. The water samples were collected monthly from each monitoring site during the year of 2021 for laboratory analysis. A total of nine water quality indicators, including Fecal Coliform, Temperature, Biochemical Oxygen Demand (BOD), pH, Turbidity, Total Solids (TS), Phosphate, Dissolved Oxygen (DO), Nitrate, and Chloride, were analyzed using standardized methods. The water quality evaluation was conducted by calculating the WQI using the National Sanitary Foundation (NSF) technique. The mass balance has been determined by means of analysis. The current study is being undertaken using both primary and secondary data sources. The investigation reveals that the primary parameters exhibit varying degrees of correlation with each other. In December, the temperature reached a minimum of 16.8 °C, while in May, it peaked at 37.5°C. The pH reached its peak at 8.80 in August, while it had its lowest point at 7.94 in January. The pH variation is minimal and similar throughout the board. The measured turbidity level was 564 NTU, which is the average value. The maximum total solids (TS) concentration recorded was 3346 mg/L, while the minimum concentration was 2460 mg/L. The phosphate content reached its peak at 8.12 mg/L in S5, while it was at its lowest at 4.26 mg/L in S4. The maximum nitrate concentration measured was 26.4 mg/L, while the minimum concentration was 12.80 mg/L. The maximum biochemical oxygen demand (BOD) recorded was 1.80 mg/L at location S6, whereas the minimum BOD was 0.60 mg/L at location S3. The concentration of BOD was consistently low during each month. The highest fecal coliform (FC) concentration observed in November was 1024 N/100ml, while the lowest concentration was 572 N/100ml. The drinking water quality standard for fecal coliform (FC) in Bangladesh is zero per 100 milliliters. The greatest, average, and lowest values surpass the allowable limit set by BDS. The water quality index determined for the year 2021 for Ten Stations has an average value of 43, indicating a similar level of water quality throughout the stations. According to the range of NSF water quality index, the Bhairab River has a poor quality rating. Therefore, this water is not safe for drinking without undergoing treatment. The Bhairab River has a Mass Balance value of 362349.09 gallons per day

Hydrogeological characterization of karst springs of the white (Proteus anguinus anguinus) and black olm (Proteus anguinus parkelj) habitat in Bela krajina (SE Slovenia)

The springs west of Črnomelj, in SE Slovenia, are the habitat of the black (Proteus anguinus parkelj) and the white olm (Proteus anguinus anguinus). Some of these springs are also the only known habitat in the world of endemic species of black olm. A steady decline in olm populations has been observed in this area over the past decades. Owing to the rapid runoff and groundwater flow high-resolution monitoring is essential in providing better insight into the hydrogeological characterization of the catchment area of springs. Specific factors and critical parameters of water behind said olm degradation have not yet been defined. Because the olm’s environment is largely aquatic, one potential critical parameter could be the higher water temperatures (>12 °C) or higher nitrate concentration (>9.2 mg/l). The six-month observation of the springs (July – December 2021) point to water temperature as a potential critical parameter since the water temperature of the springs exceeded 12 °C in months July and August. Nitrate concentrations could also be a second critical parameter in the degradation of the olm’s habitat. Maximum nitrate concentrations above 9.2 mg/l throughout much of the observation period (except for Dobličica spring). Due to less agricultural activity in December in the spring catchment area and a higher dilution rate due to reduced evapotranspiration and increased effective precipitation during this time of the year, the nitrate concentrations are decreased. The results of the measured parameters of groundwater could show the hydrogeological connection between the Otovski and Pački breg springs and between Šotor, Jamnice and Dobličica. The Obršec spring has an independent catchment area. A detailed estimation of the springs catchment area is possible due to a detailed geologic map. It is necessary to determine the origin of the nitrate (nitrate isotope analysis), to quantify the threshold values of the critical parameters, to define precisely all the causes of the olm deterioration, and to make proposals for appropriate measures to limit or even stop the decline of the olm population.

Вплив антропогенного навантаження на екологічний стан поверхневих вод в агроландшафтах західного регіону України

Goal. To analyze the state of open water bodies in the Western region of Ukraine and to identify factors that worsen their quality indicators. Methods. Route agroecological monitoring; methods of chemical and physicochemical analysis using atomic absorption spectrophotometry, flame photometry, and mathematical and statistical analysis. Results. In pond water samples taken in the village Pavlov of the Chervonograd district of the Lviv oblast, an excess of the maximum permissible concentration of nitrate and ammonium nitrogen was found — 11.8–13.2 and 4.6 mg/l, respectively. The content of manganese compounds here exceeded the normative indicators by 5–10 times. On the territory of home ownership in Zakarpattia region (vil. Sokyrnytsia, Khust district) the content of ammonium nitrogen in pond water samples exceeded the norm by 1.8 times, the content of copper by 20 times, and zinc by twice. Analysis of water from a pond located in the vil. Popeliv of the Ivano-Frankivsk district of the Ivano-Frankivsk oblast showed an excess of the norm according to the indicator of dry residue — 2120 mg/l. In water samples taken from the Prut River (vil. Sadzhavka, Nadvirniansk district, Ivano-Frankivsk oblast), the excess of normative indicators only for the iron content was 0.13 mg/l. In the water from the Sluch River (vil. Samchyky, Khmelnytskyi district, Khmelnytskyi oblast), the pH was 8.6, the phosphorus content exceeded the norm by almost two times, and copper by 10 times. In the water from the Dniester River near the vil. Nyzhniv of Ivano-Frankivsk district, Ivano-Frankivsk oblast the content of sulfates and manganese was 156.8 and 0.03 mg/l, respectively. In water samples taken from the Rika River (Khust district, Zakarpatska oblast) the iron content was 11.3 times higher than normal, and manganese was 5 times higher than normal. Conclusions. The results of the monitoring of water bodies in the specified regions proved that both natural and anthropogenic factors affect the water quality of open water bodies. The quality of pond water is largely influenced by anthropogenic factors related to the economic activities of people, and it is they that cause the accumulation of excessive amounts of nitrogen, ammonium, copper, and zinc compounds. The quality of water samples taken from the Prut, Stara, and Rika rivers was mostly determined by natural conditions. Pollution of the Sluch River with phosphorus and copper and the Dniester River with sulfates can be caused by the inflow of sewage with detergents, as well as animal waste, fertilizers, and pesticides from residential areas.

Health risk assessment of the population of the Republic of Buryatia associated with increased nitrate and nitrite intake

AIM: To conduct a hygienic assessment of the health risk levels associated with drinking water with high nitrate and nitrite contents in the rural territories of the Republic of Buryatia.
 MATERIAL AND METHODS: The content of nitrates and nitrites in drinking water in comparison with the maximum permissible concentrations (MPC) was assessed in the period of 20102019. With the use of the risk assessment methodology, non-carcinogenic risk (HQ) for adult and child populations of priority territories is calculated.
 RESULTS: In the territory of the Republic of Buryatia, two priority territories were identified according to the largest content of nitrates in the drinking water of a centralized cold water supply system: Mukhorshibirsky and Tarbagatai districts. The maximum nitrate concentrations reached 4.52 and 4.11 MPC, respectively, which are 1.71 and 1.45 times higher than in the previous five-year period, respectively. A similar situation was observed in the non-centralized water supply system in these areas, with 4.98 MPC in the Mukhorshibirsky district (1.88 times higher) and 3.41 MPC in Tarbagatai (2.53 times higher).
 CONCLUSIONS: The unacceptable level of non-carcinogenic risk due to nitrate contamination of drinking water at the level of the average centile trend (Me) is established for the adult and child population provided with centralized water supply in the Tarbagatai region. The HQ exceeds the acceptable level for children consuming decentralized drinking water in the Mukhorshibirsky district. The risk levels for children and adults due to oral intake of nitrites with drinking water of centralized and non-centralized water supply were not dangerous (HQ 1).

Spatiotemporal variations of surface water quality in a medium-sized river catchment (Northwestern Germany) with agricultural and urban land use over a five-year period with extremely dry summers

Medium-sized rivers, which are used for intensive agriculture and urban infrastructure, are subject to manifold hydrochemical stressors. Identifying and monitoring these stressors is important for river basin management and a functioning ecosystem. To understand the spatiotemporal variation of surface water quality in a highly modified lowland river, the Münstersche Aa River (Northwestern Germany) with 62% of land used for agriculture and 26% urban/residential area, was exemplarily studied. A total of 519 samples were collected using two automated high-frequency samplers and five catchment-wide sampling campaigns. They covered the five-year period 2015–2020 and included two extremely dry summers. The Münstersche Aa catchment is dominated by low permeable strata resulting in surface water runoff (Baseflow Index: 0.41) which leads to a high amplitude of discharge variation (mean discharge: 0.7 m3/s) with high flow conditions in winter/spring, and low discharge during summer/fall. In wintertime, maximum nitrate concentrations (up to 73 mg NO3/L) and loads (up to 1300 t NO3/a; up to 98% in winter) correlate with high-flow conditions. δ18O and δ15N isotopic analysis indicated manure from farmland as the major source of nitrate whereas the impact of municipal wastewater treatment plants was neglectable. Increased nitrate concentrations are linked to the higher proportion of farmland in the upper catchment (77%) compared with the lower catchment (47%). In summertime, at extremely low flow conditions, surface water consisted of up to 100% of treated wastewater, resulting in the highest measured chloride, sodium and potassium concentrations. The river is impacted by strongly seasonal and different stressors, which can be expected to intensify with ongoing climate change. Results from this study may help to adapt monitoring schemes for the Münstersche Aa but also for other lowland streams with comparable land-use targeting the goals of the Water Framework Directive.

Health risk assessment and spatial distribution of nitrate, nitrite, fluoride, and coliform contaminants in drinking water resources of kazerun, Iran

Exposure to nitrate, nitrite, and fluoride through drinking water consumption, especially in arid and semi-arid regions, has been considered by many researchers. Therefore, the present study aimed to investigate the status of nitrate, nitrite, fluoride, and total coliforms in water supply sources of Kazerun located in Fars province, Iran, determine their spatial distribution, and perform health risk assessment in four age groups (infants, children, teenagers, and adults). In this research, the concentration data of 25 groundwater wells were examined. Then, the spatial distribution of the contaminants was determined using the Arc GIS software (v. 10.5) and their health risk assessment was performed via the standard method of the US Environmental Protection Agency. The maximum concentrations of nitrate, nitrite, and fluoride were 25.5, 0.056, and 0.72 mg/l, respectively and their mean concentrations were 13.5, 0.008, and 0.52 mg/l, respectively. In addition, the mean and maximum concentrations of coliforms were 371.21 and 2694.50 CFU/100 ml, respectively. The total coliforms value was higher than the permissible limit in 60 % of the cases. The highest Chronic Daily Intake (CDI) of the studied contaminants was related to nitrate among children (range: 0.21–1.45, with an average value of 0.77 mg/kg-day). Moreover, the Hazard Quotient (HQ) values were below 1 for all contaminants and in all age groups. The highest HQ value (0.9) belonged to nitrate amongst children. Furthermore, the Hazard Index (HI), as a cumulative effect of HQ, was calculated for all three contaminants and the results showed that it was greater than 1 in 56 % of the cases among children, which was considered a serious risk. The findings revealed no significant relationship between nitrate and nitrite concentrations and total coliforms. Overall, nitrate seemed to play a more critical role in the health risk of the exposed age groups in comparison to nitrite and fluoride. Hence, appropriate managerial measures are recommended to be taken.

Health Risk Assessment for Exposure to Nitrate in Drinking Water in Central Java, Indonesia.

Since 2005, over 30 epidemiological studies have evaluated the association between nitrate in drinking water and adverse health outcomes. Conditions that lead to nitrate pollution in water, such as open defecation, the proximity of septic tanks to water sources, and the use of inorganic fertilizer, are rampant in Indonesia, which has experienced little research evaluating nitrate in drinking water. We conducted a health risk assessment for exposure to nitrate in drinking water and evaluated the nitrate concentration in key water sources in two villages of rural Central Java, Indonesia. The nitrate concentrations in the drinking water ranged from 3.55 mg/L to 26.75 mg/L as NO3−. Daily nitrate intake estimates, calculated at 50% and 95% exposure to the maximum nitrate concentration of the drinking water in both villages, were above the levels associated with birth defects, colorectal cancer, and thyroid conditions observed in other studies. There was a large variation in nitrate concentrations between and within the villages at different water sources. Further research into whether these health outcomes exist in rural Central Java, Indonesia will be required to better understand this risk.

Groundwater quality and non-carcinogenic health risk assessment of nitrate in the semi-arid region of Punjab, India

Groundwater is the main source of water in the study area (Rupnagar District, Punjab), and its quality is essential since it is the primary determinant of the suitability of groundwater for drinking and irrigation purposes. In this study, data from 28 years have been used to evaluate the adequacy of groundwater for domestic and irrigation purposes and assess the potential human health impacts of nitrate contaminants. Results of sodium adsorption ratio, percentage sodium, magnesium hazard ratio, Kelley ratio, and residual sodium carbonate illustrate that most of the sampling locations were suitable for irrigational purposes and drinking water quality of the region mostly belonged to the 'good' class. The maximum nitrate concentration was observed in the northern and north-east parts of the area. Among the three age groups, children > female > male was found to be more prone to health risks with oral ingestion of nitrate. Uncertainties in the risk estimates were quantified using Monte Carlo simulation and sensitivity analyses. Thus, a proper management plan should be adopted by the decision-makers to improve the quality of drinking water in this area to avoid major health problems in the near future.

Groundwater quality in the Jaffna peninsula of Sri Lanka and a qualitative study of BTEX removal by greenly synthesized iron nanoparticles-electro-catalyst system.

The Jaffna peninsulais northern part of Sri lanka (Longitude: 80° 06′ 2.28″ E and Latitude: 9° 41′ 12.20″ N), mainly gains water from groundwater which is continuously protected by various human activity even with reckless deterioration. The maximum nitrate concentration reached up to 51 ppm whereas the amount of phosphate found to be as 3.8 ppm. The average EC for a year is 38.1 mS/cm and corresponding salinity and TDS found to be as 20.2 and 24.3 g/L respectively. The middle region of the territory consists less saline water and 0.132 ppm of Pb and 0.092 ppm Cd presence in the groundwater. The BTEX has been completely eradicated by using the cost-effective environmentally-friendly electrochemical system. The developed system can be utilized the application areas such as service station, mechanic stores, hospitals, universities and household purpose.

Nonlinear models of the dependence of nitrate concentrations on the pumping rate of a water supply system

The aim of this paper is to analyse the influence of a groundwater pumping rate on nitrate concentrations at the Bartolovec wellfield, which is part of a water supply system of the town of Varaždin, Croatia. Over the past 16 years both the pumping rate and nitrate concentrations have increased at the wellfield. The nonlinear models that describe the pumping rate to nitrate concentration levels were developed on the basis of Logistic, Gompertz, and Richards growth functions. For each function, three different types were established regarding the initial lower contamination limit parameter. The conditions that models have to meet were defined and their reliability was established. The models were implemented on the experimental data collected during the period under consideration. The models were validated and mutually compared using Akaike’s Information Criteria (AICc), while the data fitting was estimated by using a coefficient of determination. After the results were obtained by using different models, they were compared to the maximum allowable nitrate concentrations (MAC) in water for human consumption. The dependence of nitrate concentrations on a pumping rate was confirmed and the reliable model for nitrate concentration on pumping rate was created. The model was calibrated and tested on the experimental data. The model exhibits asymptotic behavior and result shows that with the further increase in the pumping rate of groundwater drainage at the Bartolovec wellfield, nitrate concentrations will not exceed the MAC value providing there are no new sources of contamination in the zone of a pollutant influence.

Phosphorus delays the onset of nitrification during aerobic digestion of aquaculture/aquaponic solid waste

This study was carried out, at both laboratory- and pilot-scale, to investigate whether the presence of phosphorus affects the nitrification process during aerobic digestion of aquaculture/aquaponic solid waste. Results from the laboratory-scale aerobic digestions indicated that nitrification did not occur throughout the entire bioprocessing period (21 days) in aerobic bioreactors containing phosphorus. The mineralization process in laboratory-scale aerobic bioreactors which did not contain phosphorus, on the other hand, followed the typical non-inhibited nitrogen mineralization (i.e., release of ammonium, NH4+ followed by oxidation into nitrate, NO3−). Results from pilot-scale aerobic digestions confirmed that the presence of phosphorus did impact the nitrification of aquaculture/aquaponic solid waste. However, analytical data and modeled parameters revealed that the presence of phosphorus significantly (P = 0.0406) delayed the onset of nitrification (lag period of 9.2 days for aerobic bioreactors without the presence of phosphorus compared to 29.3 days for aerobic bioreactors containing phosphorus, corresponding to a delay period of 3 weeks) but did not influence (P > 0.05) the nitrification kinetic parameters (i.e., maximum nitrate concentration (99.5–101.1 mg/L) and maximum rate of nitrate production (11.3–19.6 mg/L/day)).

Copepod community structure during upwelling and non-upwelling seasons in coastal waters off Cochin, southwest coast of India

Vypeen, an island of Cochin estuarine system, acts as the spawning site of several marine and estuarine fishes. We assumed that, physical process (upwelling) make changes in hydrography and the production of chlorophyll a in coastal waters off Vypeen. These alterations can influence the zooplankton abundance and copepod community structure in that area. For justifying this hypothesis, samples were collected from Vypeen at 10 m and 30 m locations during January (pre-southwest monsoon), August (late-southwest monsoon) and November (post-southwest monsoon) 2014. During August, subsurface water column was cool, nutrient rich and less oxygenated (signatures of upwelling) than in November and January. Maximum concentrations of nitrate and chlorophyll a were recorded during August. In the present study, 15 zooplankton groups were recorded; of which copepods were the most predominant group (73%–90%). Copepod density in the present study ranged between 527.2 ind./m2 and 5 139.2 ind./m2. Totally, 37 copepods species were reported in present study and copepod species richness was higher during January. The abundance of zooplankton and copepods was high in August during late-southwest monsoon. These variations were closely associated with the coastal upwelling in August and weakening of moderate upwelling in November. In SIMPER analysis, it was found that the copepods species distribution was similar within season and dissimilar between the three seasons. Moreover, the higher abundance of upwelling indicator species Temora turbinata was recorded in August, which confirms the signs of seasonal upwelling in Vypeen. The present study emphasized on the influence of hydrographical parameters associated with physical process, in governing the copepod community organization of the Vypeen Island.

Groundwater systems in bare and covered karst aquifers: evidence from tracer tests, hydrochemistry, and groundwater ages

The east Guilin region contains a karst dominated hydrological system along the Lijiang River. The two main topographic characteristics of the basin are peak cluster depression and peak forest. Despite the fact that these areas represent adjacent units, they have different groundwater movement patterns. This study describes the groundwater and solute movement in the different hydrogeological sub-regions via several techniques. Our results indicated that the topographic boundary between the peak cluster depression and the peak forest is clear. However, a transition zone exists between these topographic zones, and it can be determined in terms of groundwater movement. We employed several methods that are widely considered to be effective. Tracer tests were conducted in the transition zone, hydrochemistry techniques were used in the peak forest, and groundwater age dating based on CFCs was employed throughout the study area. The main conduits could be found in the transition zone, but the groundwater flow was much slower in the transition zone than in the mountain peak cluster area. Minor conduits also accounted for a high proportion of the total flow in the transition zone. The solute migration within the plain, which was determined by analyzing the nitrates, was controlled by mixing and distance effects. The maximum nitrate concentration was limited at the local scale. The nitrate concentration gradient at the regional scale was not related to the groundwater movement, indicating that the groundwater recharged in a dispersed manner and discharged at discrete locations along the river. The age dating revealed that the groundwater was older in the plain than in the bare mountain zone. This was due to the strong mixing of young and old water, which was the result of the characteristics of the karst media in the aquifer. Our investigation of the groundwater system in a bare/covered karst aquifer provides data for decision-making in effective groundwater management.

Lėvens upės taršos tyrimas

Darbo tikslas – ištirti Lėvens upės taršą. Pateikiamos žinios apie šios upės būklę. Apskaičiuoti teršalų kiekiai, kurie atplukdomi į Lėvens upę iš Svalios upės. Lėvens upėje pasirinkta 10 taškų, kuriuose buvo imami vandens mėginiai. Vandens mėginiuose ištirta vandens temperatūra, pH, skendinčiųjų medžiagų kiekis, ištirpęs deguonies kiekis, biocheminis deguonies suvartojimas per 7 paras, amonio azoto, bendrojo azoto, nitratų, bendrojo fosforo ir fosfatų koncentracijos. Tyrimas buvo atliekamas 2018 m. balandžio mėnesį. Ištirtuose vandens mėginiuose pH kito nuo 7,53 iki 8,01. Skendinčiųjų medžiagų koncentracija kito nuo 8,9 mg/l iki 17,6 mg/l, nebuvo viršijama didžiausia leistina koncentracija. Bendrojo azoto koncentracija mėginiuose kito nuo 3,89 mg/l iki 4,38 mg/l ir buvo viršyta visuose upės taškuose. Ribinę vertę viršijanti nitratų koncentracija siekė 2,47 mgN/l. Nitratų koncentracija kitose tirtose upės vietose kito nuo 1,37 mgN/l iki 2,23 mgN/l, tačiau ribinės vertės neviršijo. Didžiausia bendrojo fosforo koncentracija Lėvens upėje nustatyta Svalios upės žiotyse – leistinos koncentracijos ribinę vertę viršijo 0,059 mgP/l.Gauti mėginių rezultatai palyginti su Pasvalio rajono savivaldybės monitoringo duomenimis, bendra Lėvens upės būklė priskirtina vidutinei ekologinės būklės klasei.

An integrated framework to model nitrate contaminants with interactions of agriculture, groundwater, and surface water at regional scales: The STICS–EauDyssée coupled models applied over the Seine River Basin

Nutrient enrichment from natural and anthropogenic activities is one of the major environmental pollution stressors. This study presents an integrated framework that couples a mesoscale atmospheric analysis system (SAFRAN), an agronomic model (STICS) and a distributed hydro(geo)logic model (EauDyssée) to estimate nitrogen flux at the regional scale. The EauDyssée modeling framework was developed to include nitrate transport from soils to rivers via surface runoff and stream-aquifer interactions. Further, an in-stream nitrate model was developed based on the large-scale river routing of the framework. The utility of the integrated framework was demonstrated on the Seine River Basin (SRB), which has an area of 88,000 square kilometers. The SRB is one of the most productive agricultural areas in France and encompasses the megalopolis of Paris. This basin is a complex hydrosystem with multiple aquifers. The STICS-EauDyssée integrated framework was implemented for a long-term simulation covering 39 years (1971–2010) at a daily time step. Comparison of groundwater nitrate concentrations with observations showed an overall absolute bias of less than 10 mg/L. Model results showed that simulated nitrate flux to rivers highly depend on the inflow produced by surface and subsurface waters. Results also demonstrated that approximately 10% of leaching nitrate flux is delivered to the river network from stream-aquifer interactions. The statistical analysis indicates the modeling system performs better in the eastern region of the SRB in comparison to the western part of the basin, due to the hydrological complexity of the western part of the basin. Comparison of maximum nitrate concentration between dry and wet years (1990 and 2001) showed an increase of 60%, largely driven by more annual water yield in the wet year compared to the dry year.

Simulation of heterogeneous photooxidation of SO<sub>2</sub> and NO<sub><i>x</i></sub> in the presence of Gobi Desert dust particles under ambient sunlight

Abstract. To improve the simulation of the heterogeneous oxidation of SO2 and NOx in the presence of authentic mineral dust particles under ambient environmental conditions, the explicit kinetic mechanisms were constructed in the Atmospheric Mineral Aerosol Reaction (AMAR) model. The formation of sulfate and nitrate was divided into three phases: the gas phase, the non-dust aqueous phase, and the dust phase. In particular, AMAR established the mechanistic role of dust chemical characteristics (e.g., photoactivation, hygroscopicity, and buffering capacity) in heterogeneous chemistry. The photoactivation kinetic process of different dust particles was built into the model by measuring the photodegradation rate constant of an impregnated surrogate (malachite green dye) on a dust filter sample (e.g., Arizona test dust – ATD – and Gobi Desert dust – GDD) using an online reflective UV–visible spectrometer. The photoactivation parameters were integrated with the heterogeneous chemistry to predict the formation of reactive oxygen species on dust surfaces. A mathematical equation for the hygroscopicity of dust particles was also included in the AMAR model to process the multiphase partitioning of trace gases and in-particle chemistry. The buffering capacity of dust, which is related to the neutralization of dust alkaline carbonates with inorganic acids, was included in the model to dynamically predict the hygroscopicity of aged dust. The AMAR model simulated the formation of sulfate and nitrate using experimental data obtained in the presence of authentic mineral dust under ambient sunlight using a large outdoor smog chamber (University of Florida Atmospheric Photochemical Outdoor Reactor, UF-APHOR). Overall, the influence of GDD on the heterogeneous chemistry was much greater than that of ATD. Based on the model analysis, GDD enhanced the sulfate formation mainly via its high photoactivation capability. In the case of NO2 oxidation, dust-phase nitrate formation is mainly regulated by the buffering capacity of dust. The measured buffering capacity of GDD was 2 times greater than that of ATD, and consequently, the maximum nitrate concentration with GDD was nearly 2 times higher than that with ATD. The model also highlights that in urban areas with high NOx concentrations, hygroscopic nitrate salts quickly form via titration of the carbonates in the dust particles, but in the presence of SO2, the nitrate salts are gradually depleted by the formation of sulfate.

Unexpected nationwide nitrate declines in groundwater of Korea

AbstractElevated levels of nitrate in groundwater are an important concern for health and the environment. The overapplication of nitrogen fertilizer to croplands is one of the major sources of high nitrate content in groundwater. In this study, we analyse the nitrate concentrations in Korean groundwater based on data from groundwater quality monitoring wells (n = 1,022–2,072), which were sampled twice annually over a recent 13‐year analysis period (2001–2013). We report that groundwater nitrate levels are decreasing, despite steadily increasing groundwater use. The maximum nitrate concentration decreased from 168.91 to 48.11 mg/L, whereas the mean values also show a gradual decreasing trend. Non‐parametric Mann–Kendall tests on nitrate concentrations also confirm the decreasing trend. The nitrate decrease is more clearly evident in agricultural groundwater as compared to domestic and drinking groundwaters. This decrease of nitrate in groundwater coincides with a large decline in nitrogen fertilizer application due to reduced cropland areas, more sustainable agricultural practices, and progressive improvement of sewage disposal services. This study proposes that the long‐term adoption of best practices in agriculture has had a positive impact on groundwater nitrate control.

The Effectiveness of Nitrate-Mediated Control of the Oil Field Sulfur Cycle Depends on the Toluene Content of the Oil.

The injection of nitrate is one of the most commonly used technologies to impact the sulfur cycle in subsurface oil fields. Nitrate injection enhances the activity of nitrate-reducing bacteria, which produce nitrite inhibiting sulfate-reducing bacteria (SRB). Subsequent reduction of nitrate to di-nitrogen (N2) alleviates the inhibition of SRB by nitrite. It has been shown for the Medicine Hat Glauconitic C (MHGC) field, that alkylbenzenes especially toluene are important electron donors for the reduction of nitrate to nitrite and N2. However, the rate and extent of reduction of nitrate to nitrite and of nitrite to nitrogen have not been studied for multiple oil fields. Samples of light oil (PNG, CPM, and Tundra), light/heavy oil (Gryphon and Obigbo), and of heavy oil (MHGC) were collected from locations around the world. The maximum concentration of nitrate in the aqueous phase, which could be reduced in microcosms inoculated with MHGC produced water, increased with the toluene concentration in the oil phase. PNG, Gryphon, CPM, Obigbo, MHGC, and Tundra oils had 77, 17, 5.9, 4.0, 2.6, and 0.8 mM toluene, respectively. In incubations with 49 ml of aqueous phase and 1 ml of oil these were able to reduce 22.2, 12.3, 7.9, 4.6, 4.0, and 1.4 mM of nitrate, respectively. Nitrate reduced increased to 35 ± 4 mM upon amendment of all these oils with 570 mM toluene prior to incubation. Souring control by nitrate injection requires that the nitrate is directed toward oxidation of sulfide, not toluene. Hence, the success of nitrate injections will be inversely proportional to the toluene content of the oil. Oil composition is therefore an important determinant of the success of nitrate injection to control souring in a particular field.