Identifying source and transformation of riverine nitrates in a karst watershed, North China: comprehensively using major ions, multiple isotopes and Bayesian model

2021 ◽  
Author(s):  
Jie Zhang ◽  
Menggui Jin
Keyword(s):  
Surface Water ◽  
Organic Nitrogen ◽  
North China ◽  
Drainage Basin ◽  
Major Ions ◽  
Inorganic Nitrogen ◽  
Mixing Model ◽  
Main Process ◽  
Soil Organic Nitrogen ◽  
Biogeochemical Transformations

<p>The identification of nitrate (NO<sub>3</sub><sup>-</sup>) sources and biogeochemical transformations is critical for understanding and controlling diffuse pollution in surface water in drainage basins. This study combines water chemistry, environmental isotopes (δ<sup>2</sup>H<sub>H2O</sub>, δ<sup>18</sup>O<sub>H2O</sub>, δ<sup>15</sup>N<sub>NO3</sub>, and δ<sup>18</sup>O<sub>NO3</sub>), with land use data and a Bayesian isotope mixing model (Simmr), for reducing the uncertainty in estimating the contributions of different pollution sources in a Karst drainage basin of Jinan, North China. 64 samples were collected from Yufu River (YFR) of Jinan city in September and December, 2019. The results revealed that the NO<sub>3</sub><sup>−</sup>-N (4.41mg/L) was the predominant form of inorganic nitrogen in YFR watershed, accounting for about 58% of total nitrogen (8.06 mg/L). There were significant temporal and spatial variations in nitrate concentrations in the area. The nitrate concentration in time was low in December and high in September, while the process of first rising and then attenuating from upstream to downstream in space. Moreover, according to the surface water flow path, different biogeochemical transformations were observed throughout the study area: microbial nitrification was dominant in the upstream with elevated NO<sub>3</sub><sup>−</sup>-N concentrations; in the middle stream a mixing of different transformations, such as nitrification, denitrification, and/or assimilation, were identified, associated to moderate NO<sub>3</sub><sup>−</sup>-N concentrations; whereas in the downstream the main process affecting NO<sub>3</sub><sup>−</sup>-N concentrations was assimilation, and/or denitrification, resulting in low NO<sub>3</sub><sup>−</sup>-N concentrations. Water chemical and dual isotope of δ<sup>15</sup>N<sub>NO3</sub> and δ<sup>18</sup>O<sub>NO3 </sub>indicated that the river water was significantly affected by soil organic nitrogen and ammonium fertilizer inputs. Simmr mixing model outputs revealed that soil organic nitrogen (SON 55.5%) and ammonium fertilizer inputs(AF 29.5%) were the primary contributors of N pollution, whereas nitrate fertilizer(NF 7.1%), sewage & manure (M&S 3.6%), and atmospheric deposition (AP3.4%) played a less important role. The chemical fertilizer (AF and NF) and SON collectively mean contributing > 50 % of nitrate both in September and December in the watershed. Therefore, reducing fertilizer application and adopting water-saving irrigationare key to control nitrate pollution in the area. The results provide scientific basis for the water quality protection and sustainable water management in the study area or similar areas.</p>

scholarly journals Sources and fluxes of organic nitrogen in precipitation over the southern East Sea/Sea of Japan

2015 ◽  
Vol 15 (5) ◽  
pp. 2761-2774 ◽  
Author(s):  
G. Yan ◽  
G. Kim
Keyword(s):  
Atmospheric Deposition ◽  
Sea Of Japan ◽  
Organic Nitrogen ◽  
Major Ions ◽  
Inorganic Nitrogen ◽  
East Sea ◽  
Reactive Nitrogen ◽  
Back Trajectory ◽  
Northwestern Pacific ◽  
Organic Fraction

Abstract. We measured total dissolved reactive nitrogen in precipitation samples collected at Uljin, a Korean coastal site upwind of the southern East Sea/Sea of Japan (EJS), selected as a representative study site of atmospheric deposition over the northwestern Pacific margin. NO3- was found to be the most abundant nitrogen species, followed by NH4+ and dissolved organic nitrogen (DON). Air-mass back-trajectory (AMBT) analysis revealed that a significant fraction of the inorganic nitrogen (NO3- and NH4+) originated from mainland Asia, whereas the DON was primarily derived from Korea. Using varimax-rotated factor analysis in combination with major ions as tracers, agricultural activities in Korea were identified as the primary sources of DON in these samples. In addition, a positive correlation was found at Uljin between the size of organic fraction in total reactive nitrogen and nitrogen to carbon atomic ratio in organic matter. This correlation has also been observed at other locations worldwide, implying the utilization potential of atmospheric organic nitrogen might increase with its proportion in total nitrogen. Combining wet deposition measurements in this study with literature values for dry deposition observed at a remote island in the EJS, the total atmospheric depositional flux of reactive nitrogen was estimated to be 115 mmol N m−2 yr−1 over the southern EJS. Our study sheds new light on the potentially significant contribution to primary productivity of the northwestern Pacific Ocean by atmospheric deposition of nitrogen, especially the organic fraction.

scholarly journals Capturing temporal and spatial variability in the chemistry of shallow permafrost ponds

2017 ◽  
Vol 14 (23) ◽  
pp. 5471-5485 ◽  
Author(s):  
Matthew Q. Morison ◽  
Merrin L. Macrae ◽  
Richard M. Petrone ◽  
LeeAnn Fishback
Keyword(s):  
Spatial Variability ◽  
Temporal Variability ◽  
Dissolved Organic Nitrogen ◽  
Organic Nitrogen ◽  
Multiple Scales ◽  
Major Ions ◽  
Inorganic Nitrogen ◽  
Storm Event ◽  
Rain Event ◽  
Event Scale

Abstract. Across the circumpolar north, the fate of small freshwater ponds and lakes (< 1 km2) has been the subject of scientific interest due to their ubiquity in the landscape, capacity to exchange carbon and energy with the atmosphere, and their potential to inform researchers about past climates through sediment records. A changing climate has implications for the capacity of ponds and lakes to support organisms and store carbon, which in turn has important feedbacks to climate change. Thus, an improved understanding of pond biogeochemistry is needed. To characterize spatial and temporal patterns in water column chemistry, a suite of tundra ponds were examined to answer the following research questions: (1) does temporal variability exceed spatial variability? (2) If temporal variability exists, do all ponds (or groups of ponds) behave in a similar temporal pattern, linked to seasonal hydrologic drivers or precipitation events? Six shallow ponds located in the Hudson Bay Lowlands region were monitored between May and October 2015 (inclusive, spanning the entire open-water period). The ponds span a range of biophysical conditions including pond area, perimeter, depth, and shoreline development. Water samples were collected regularly, both bimonthly over the ice-free season and intensively during and following a large summer storm event. Samples were analysed for nitrogen speciation (NO3−, NH4+, dissolved organic nitrogen) and major ions (Cl−, SO42−, K+, Ca2+, Mg2+, Na+). Across all ponds, temporal variability (across the season and within a single rain event) exceeded spatial variability (variation among ponds) in concentrations of several major species (Cl−, SO42−, K+, Ca2+, Na+). Evapoconcentration and dilution of pond water with precipitation and runoff inputs were the dominant processes influencing a set of chemical species which are hydrologically driven (Cl−, Na+, K+, Mg2+, dissolved organic nitrogen), whereas the dissolved inorganic nitrogen species were likely mediated by processes within ponds. This work demonstrates the importance of understanding hydrologically driven chemodynamics in permafrost ponds on multiple scales (seasonal and event scale).

scholarly journals Sources and fluxes of organic nitrogen in precipitation over the southern East/Japan Sea: potential impacts on marine productivity

2014 ◽  
Vol 14 (23) ◽  
pp. 31987-32025
Author(s):  
G. Yan ◽  
G. Kim
Keyword(s):  
Atmospheric Deposition ◽  
Organic Nitrogen ◽  
Major Ions ◽  
Inorganic Nitrogen ◽  
Japan Sea ◽  
Atomic Ratio ◽  
Reactive Nitrogen ◽  
Back Trajectory ◽  
Northwestern Pacific ◽  
Organic Fraction

Abstract. We measured total dissolved reactive nitrogen in precipitation samples collected at Uljin, a Korean coastal site upwind of the southern East/Japan Sea (EJS), selected as a representative study site of atmospheric deposition over the northwestern Pacific margin. NO3− was found to be the most abundant nitrogen species, followed by NH4+ and dissolved organic nitrogen (DON). Air mass back trajectory analysis revealed that a significant fraction of the inorganic nitrogen (NO3− and NH4+) originated from mainland Asia, whereas the DON was primarily derived from Korea. Using varimax-rotated factor analysis in combination with major ions as tracers, agricultural activities in Korea were identified as the primary sources of DON in these samples. In addition, a positive correlation was found at Uljin between the size of organic fraction in total reactive nitrogen and nitrogen to carbon atomic ratio in organic matter. This correlation has also been observed at other locations worldwide, implying the utilization potential of atmospheric organic nitrogen might increase with its proportion in total nitrogen. Combining wet deposition measurements in this study with literature values for dry deposition observed at a remote island in the EJS, the total atmospheric depositional flux of reactive nitrogen was estimated to be 115 mmol N m−2 yr−1 over the southern EJS. Our study sheds new light on the potentially significant contribution to primary productivity of the northwestern Pacific Ocean by atmospheric deposition of nitrogen, especially the organic fraction.

scholarly journals Water Quality and Hydrogeochemical Characteristics of Some Karst Water Sources in Apuseni Mountains, Romania

Water ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 857
Author(s):  
Maria-Alexandra Hoaghia ◽  
Ana Moldovan ◽  
Eniko Kovacs ◽  
Ionut Cornel Mirea ◽  
Marius Kenesz ◽  
...  
Keyword(s):  
Drinking Water ◽  
Water Chemistry ◽  
Major Ions ◽  
Anthropogenic Activities ◽  
Water Sources ◽  
Main Process ◽  
Karst Water ◽  
Rock Interaction ◽  
Apuseni Mountains ◽  
Karst Waters

Human activities and natural factors determine the hydrogeochemical characteristics of karst groundwaters and their use as drinking water. This study assesses the hydrogeochemical characteristics of 14 karst water sources in the Apuseni Mountains (NW Romania) and their potential use as drinking water sources. As shown by the Durov and by the Piper diagrams, the chemical composition of the waters is typical of karst waters as it is dominated by HCO3− and Ca2+, having a circumneutral to alkaline pH and total dissolved solids ranging between 131 and 1092 mg L−1. The relation between the major ions revealed that dissolution is the main process contributing to the water chemistry. Limestone and dolostone are the main Ca and Mg sources, while halite is the main Na and Cl source. The Gibbs diagram confirmed the rock dominance of the water chemistry. The groundwater quality index (GWQI) showed that the waters are of excellent quality, except for two waters that displayed medium and good quality status. The quality of the studied karst waters is influenced by the geological characteristics, mainly by the water–rock interaction and, to a more limited extent, by anthropogenic activities. The investigated karst waters could be exploited as drinking water resources in the study area. The results of the present study highlight the importance of karst waters in the context of good-quality water shortage but also the vulnerability of this resource to anthropogenic influences.

scholarly journals Spatial variability of nitrate pollution and its sources in a hilly basin of the Yangtze River based on clustering

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yuhuan Cui ◽  
Jie Wang ◽  
Shuang Hao
Keyword(s):  
Surface Water ◽  
Yangtze River ◽  
Drainage Basin ◽  
Quality Standard ◽  
Nitrate Pollution ◽  
Middle Part ◽  
Lake Basin ◽  
The Yangtze River ◽  
Nitrate Sources ◽  
Groundwater Samples

AbstractNitrate (NO3−) pollution is a serious global problem, and the quantitative analysis of its sources contributions is essential for devising effective water-related environmental-protection policies. The Shengjin Lake basin, located in the middle to lower reaches of the Yangtze River in China was selected as the research area in our study. We first grouped 29 surface water samples and 33 groundwater samples using cluster analysis, and then analyzed potential nitrate sources for each dataset of δ15N–NO3− and δ18O–NO3− isotope values by applying a Bayesian isotope-mixing model. Our results show that the nitrogen pollution in the surface-ground water in the study area seriously exceeded to class V of the Environmental Quality Standard of Surface Water of China. The NO3− in surface water from the mid-upper reaches of the drainage basin mainly originates from soil nitrogen (SN) and chemical fertilizer (CF), with contribution rates of 48% and 32%, respectively, and the NO3− in downstream areas mainly originates from CF and manure and sewage (MS), with contribution rates of 48% and 33%, respectively. For the groundwater samples, NO3− mainly originates from MS, CF, and SN in the mid-upper reaches of the drainage basin and the northside of Dadukou near the Yangtze River, with contribution rates of 34%, 31%, and 29%, respectively, whereas NO3− in the lower reaches and the middle part of Dadukou mainly originates from MS, with a contribution rate of 83%. The nitrogen conversion of surface water in lakes and in the mid-upper reaches is mainly affected by water mixing, while the groundwater and surface water in the lower plains are mainly affected by denitrification. The method proposed in this study can expand the ideas for tracking nitrate pollution in areas with complex terrain, and the relevant conclusions can provide a theoretical basis for surface and groundwater pollution control in the hilly basin of Yangtze River.

scholarly journals Different forms of nitrogen deposition show variable effects on soil organic nitrogen turnover in a temperate forest

2022 ◽  
Vol 169 ◽  
pp. 104212
Author(s):  
Jihui Tian ◽  
Kai Wei ◽  
Tao Sun ◽  
Nan Jiang ◽  
Zhenhua Chen ◽  
...  
Keyword(s):  
Nitrogen Deposition ◽  
Temperate Forest ◽  
Organic Nitrogen ◽  
Soil Organic Nitrogen ◽  
Nitrogen Turnover

Tillage effects on labile pools of soil organic nitrogen in a semi-humid climate of Argentina: A long-term field study

2017 ◽  
Vol 169 ◽  
pp. 71-80 ◽  
Author(s):  
Juan M. Martínez ◽  
Juan A. Galantini ◽  
Matias E. Duval ◽  
Fernando M. López
Keyword(s):  
Field Study ◽  
Organic Nitrogen ◽  
Humid Climate ◽  
Soil Organic Nitrogen ◽  
Term Field
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