Nitrate sources and nitrogen dynamics in a karst aquifer with mixed nitrogen inputs (Southwest China): Revealed by multiple stable isotopic and hydro-chemical proxies

2021 ◽  
pp. 118000
Author(s):  
Kun Ren ◽  
Xiaodong Pan ◽  
Daoxian Yuan ◽  
Jie Zeng ◽  
Jiapeng Liang ◽  
...  
Keyword(s):  
Southwest China ◽  
Karst Aquifer ◽  
Nitrogen Dynamics ◽  
Nitrate Sources ◽  
Nitrogen Inputs ◽  
Stable Isotopic

Discrimination of Nitrogen Sources in Karst Spring Contributing Areas Using a Bayesian Isotope Mixing Model and Wastewater Tracers (Florida, USA)

2020 ◽  
Vol 26 (3) ◽  
pp. 291-311
Author(s):  
Andy Canion ◽  
Katherine M. Ransom ◽  
Brian G. Katz
Keyword(s):  
Land Use ◽  
Nitrogen Sources ◽  
Mixing Model ◽  
Septic Tank ◽  
Residential Areas ◽  
Nitrate Sources ◽  
Prior Probabilities ◽  
Relative Contribution ◽  
Use Of Resources ◽  
Nitrogen Inputs

ABSTRACT Many springs in Florida have experienced a proliferation of nuisance algae and alteration of trophic structure in response to increases in nitrate concentration concurrent with rapid population growth and land use intensification beginning in the mid-20th century. While loading targets and remediation plans have been developed by state agencies to address excess nitrogen inputs, further confirmation of the relative contribution of nitrogen sources to groundwater is necessary to optimize the use of resources when implementing projects to reduce nitrogen loads. In the present study, stable isotopes of nitrate and wastewater indicators were used to discriminate sources of nitrogen in wells and springs in central Florida. Sampling was performed in 50 wells at 38 sites and at 10 springs with varying levels of agriculture and urban development. Nitrate isotope values were used to develop Bayesian mixing models to estimate the probability distribution of the contributions of nitrate sources in wells. Prior probabilities for the fractional contribution of each source were adjusted based on land use and density of septic tanks. Sucralose and the Cl:Br mass ratio were used as confirmatory indicators of wastewater sources. In residential areas, mixing model results indicated that fertilizer or mixed fertilizer and wastewater (septic tank effluent and reuse water) were the primary sources, with sucralose detections corresponding to wells with elevated contributions from wastewater. Sources of nitrogen in pasture and field crop areas were primarily fertilizer and manure; however, model posterior distributions of δ15N indicated that manure sources may have been overpredicted. The present study demonstrates the utility of a multi-tracer approach to build multiple lines of evidence to develop locally relevant remediation strategies for nitrogen sources in groundwater.

scholarly journals Overview of the Chemical and Isotopic Investigations of the Mareza Springs and the Zeta River in Montenegro

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 957
Author(s):  
Katarina Živković ◽  
Milan Radulović ◽  
Sonja Lojen ◽  
Mira Pucarević
Keyword(s):  
Seasonal Variations ◽  
Water Samples ◽  
Mean Transit Time ◽  
Karst Aquifer ◽  
Winter Period ◽  
Mountainous Area ◽  
Monthly Precipitation ◽  
Air Masses ◽  
Water Fraction ◽  
Stable Isotopic

The Mareza karst aquifer is the most important drinking water resource for the water supply system of the City of Podgorica, the capital of Montenegro. This study presents the first assessment for the determination of the Mareza catchment area. Water chemistry and stable isotopic composition (δ18O and δ2H) of monthly precipitation samples (as inputs) are presented, in order to determine the Local Meteoric Water Line (LMWL) for the study area, and to analyze the behavior of the karst spring Mareza (as output) and the Zeta River water. The possible impact of the river on the Mareza springs was also investigated. Stable isotope compositions were used to analyze the origin of the four springs of the Mareza aquifer. Seasonal variations of δ18O and δ2H values and deuterium excess (d excess) changes in precipitation are explained by the mixing of air masses, such that a Mediterranean source prevails in the winter period, while in the summer period, the area is rather under the influence of air mass originating from the Atlantic Ocean. All spring water samples have lower δ values than the local precipitation and they plot above the LMWL, which may indicate recharge at a higher altitude in the distant mountainous area. The d excess values of all water samples (higher than 10‰) indicate the prevalence of the Mediterranean as a moisture source. Based on the analysis of the seasonal variations of δ18O and δ2H in precipitation and the Mareza spring, it has been estimated that the groundwater mean transit time (MTT) is 92–129 days, and that the young water fraction (Fyw) amounts to 40.9%–53.3%. These values are typical for the strong karstic springs of highly karstified terrains.

Using δ15N- and δ18O-Values To Identify Nitrate Sources in Karst Ground Water, Guiyang, Southwest China

2006 ◽  
Vol 40 (22) ◽  
pp. 6928-6933 ◽  
Author(s):  
Cong-Qiang Liu ◽  
Si-Liang Li ◽  
Yun-Chao Lang ◽  
Hua-Yun Xiao
Keyword(s):  
Ground Water ◽  
Southwest China ◽  
Nitrate Sources

Nitrogen dynamics in conventional and no-tillage agroecosystems with inorganic fertilizer or legume nitrogen inputs

1987 ◽  
Vol 97 (3) ◽  
pp. 315-332 ◽  
Author(s):  
Peter M. Groffman ◽  
Paul F. Hendrix ◽  
D. A. Crossley
Keyword(s):  
Nitrogen Dynamics ◽  
Inorganic Fertilizer ◽  
No Tillage ◽  
Nitrogen Inputs

scholarly journals Is there any isotopic fractionation of nitrate associated with diffusion and advection?

2012 ◽  
Vol 9 (2) ◽  
pp. 158 ◽  
Author(s):  
Priscillia Semaoune ◽  
Mathieu Sebilo ◽  
Joëlle Templier ◽  
Sylvie Derenne
Keyword(s):  
Isotopic Composition ◽  
Aquatic Ecosystems ◽  
Nitrate Solution ◽  
Isotopic Fractionation ◽  
Transport Processes ◽  
Biological Processes ◽  
Physical Processes ◽  
Nitrogen Inputs ◽  
Stable Isotopic ◽  
Transport Diffusion

Environmental contextAnthropogenic nitrogen inputs have significant effects on terrestrial and aquatic ecosystems, the extent of which can be traced by using the natural stable isotopic composition of nitrate to integrate the sources of nitrogen and the biological processes of their production. In ecosystems, nitrates are transported by diffusion in water and advection of water masses, but these physical processes have not been characterised in terms of isotopic fractionation. We report experiments demonstrating that physical transport processes have a negligible effect on the isotopic composition of dissolved nitrate. AbstractWe experimentally investigated the effect of the physical process of transport (diffusion and advection) on the isotopic composition of nitrate (δ15N and δ18O). Strict diffusion of nitrate in water was studied using a modified Richter apparatus. The combination of diffusion and advection processes was followed by elution of nitrate solution onto silica gel column. No significant isotopic fractionation was observed.

scholarly journals Nitrate vulnerability of karst aquifers and associated groundwater-dependent ecosystems in the Baltic region

2021 ◽  
Vol 80 (18) ◽  
Author(s):  
Andis Kalvāns ◽  
Konrāds Popovs ◽  
Agnese Priede ◽  
Oliver Koit ◽  
Inga Retiķe ◽  
...  
Keyword(s):  
Conceptual Model ◽  
Karst Aquifer ◽  
Cold Season ◽  
Nitrogen Fertilizers ◽  
Baltic Region ◽  
Geological Conditions ◽  
Nitrogen Inputs ◽  
Groundwater Dependent Ecosystems ◽  
The Baltic

AbstractGroundwater pollution by agrochemicals such as nitrogen fertilizers can cause complex biogeochemical transformations to take place in groundwater-dependent ecosystems. To explore the interaction between nitrogen load and groundwater-dependent, spring-fed ecosystems, a study was conducted in Latvia in an area of suspected high nitrate (NO3−) vulnerability due to its geological settings. A map of NO3− vulnerability along the margins of the carbonate aquifer in Latvia is presented. The map is based on a conceptual model that was developed during an extensive case study involving hydrological, hydrochemical, and habitat investigation of springs discharging from a karst aquifer and spring-fed ecosystems. Areas that should be prime targets for restricting fertilizer application are highlighted on the map. Although the case study revealed increased nitrogen pollution (up to 51 mg L−1, standard deviation of 9 mg L−1, in the springs discharging from the karst aquifer), no clear evidence of adverse effects due to NO3− pollution on the groundwater-dependent ecosystems using biotic indicators was found, highlighting the resilience of spring-fed ecosystems against high nitrogen inputs. In the case study, downstream groundwater-dependent ecosystems retained 70% of the reactive nitrogen during the vegetation season, but only a small proportion during the cold season. Thus, NO3− pollution can be partly mitigated by restoring wetlands along valley slopes where natural groundwater discharge takes place. The conceptual model developed for groundwater NO3− vulnerability is applicable to other areas in the Baltic region and other places with similar climatic and geological conditions.

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