• Proceedings of the KSEEG Conference
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• 2007.04a
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• pp.453-455
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• 2007

• Proceedings of the KSEEG Conference
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• 2005.04a
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• pp.255-259
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• 2005

• Korean Journal of Ecology and Environment
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• v.50 no.4
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• pp.459-469
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• 2017

Nitrogen (N) loading from domestic, agricultural and industrial sources can lead to excessive growth of macrophytes or phytoplankton in aquatic environment. Many studies have used stable isotope ratios to identify anthropogenic nitrogen in aquatic systems as a useful method for studying nitrogen cycle. In this study to evaluate the precision and accuracy of denitrification bacteria method (Pseudomonas chlororaphis ssp. Aureofaciens ($ATCC^{(R)}$ 13985)), three reference (IAEA-NO-3 (Potassium nitrate $KNO_3$), USGS34 (Potassium nitrate $KNO_3$), USGS35 (Sodium nitrate $KNO_3$)) were analyzed 5 times repeatedly. Measured the ${\delta}^{15}N-NO_3$ and ${\delta}^{18}O-NO_3$ values of IAEA-NO-3, USGS 34 and USGS35 were ${\delta}^{15}N:4.7{\pm}0.1$‰ ${\delta}^{18}O:25.6{\pm}0.5$‰, ${\delta}^{15}N:-1.8{\pm}0.1$‰ ${\delta}^{18}O:-27.8{\pm}0.4$‰, and ${\delta}^{15}N:2.7{\pm}0.2$‰ ${\delta}^{18}O:57.5{\pm}0.7$‰, respectively, which are within recommended values of analytical uncertainties. Also, we investigated isotope values of potential nitrogen source (soil, synthetic fertilizer and organic-animal manures) and temporal patterns of ${\delta}^{15}N-NO_3$ and ${\delta}^{18}O-NO_3$ values in river samples during from May to December. ${\delta}^{15}N-NO_3$ and ${\delta}^{18}O-NO_3$ values are enriched in December suggesting that organic-animal manures should be one of the main N sources in those areas. The current study clarifies the reliability of denitrification bacteria method and the usefulness of stable isotopic techniques to trace the anthropogenic nitrogen source in freshwater ecosystem.

• Economic and Environmental Geology
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• v.45 no.1
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• pp.23-30
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• 2012

Major ions and nitrogen isotopic analyses were performed to determine the geochemical characters and to identify the source of nitrate of the shallow groundwater around agricultural field in the Youngdong area. The pH value of groundwater ranges from 60. to 8.2 (pH 7.2, mean). The average of EC, Eh and DO is 369 ${\mu}S/cm$ (70~729 ${\mu}S/cm$), 165.6 mV (29~383.2 mV), 4.3 mg/L (1.8~8.0 mg/L) respectively. The ion concentraion of groundwater was in the order of $Ca^{2+}$>$Na^{2+}$>$Mg^{2+}$>$K^{2+}$ and ${HCO_3}^-$>${NO_3}^-$>${SO_4}^{2-}$>$Cl^-$>$F^-$. Most of groundwater is Ca-$HCO_3$ type. The groundwater was affected by water-rock interaction in the shallow depth. Some groundwater is Ca-Cl or Na-$HCO_3$ (2.5%) type that was due to agricultural activities. The $NO_3$_N concetration of grondwater range from 10.2 mg/l to 26.9 mg/l, which show that this area is under nitrate pollution. ${\delta}^{15}N-NO_3$ value of the groundwater is the origins of are a combination of animal wastes and man-made fertilizers.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.17 no.2
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• pp.120-129
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• 2012

We investigated seasonal variation of sediment-water oxygen and inorganic nitrogen fluxes, and denitrification at tidal flat sediments located in the Nakdong River Estuary from July 2005 to September 2006. Net oxygen fluxes, measured with sediment incubations at in situ temperature, varied from -37.0 to $0.5mmol\;O_2\;m^{-2}\;d^{-1}$. Oxygen fluxes into the sediments from the overlying water increased due to the increased water temperature. Denitrification rate ($4{\sim}2732{\mu}mol\;N\;m^{-2}\;d^{-1}$) in this study was higher compared to the other Korean coast measured with the same method. Denitrification showed the same seasonal variation as oxygen fluxes. Denitrification rate based on $^{15}N$-nitrate showed a strong correlation with nitrate flux into the sediments from the overlying water. Denitrification via "water column supplied nitrate ($D_w$)", calculated from Isotope pairing technique, also correlated well with nitrate flux into the sediments. Nitrate from water column seems to account for seasonal variation of denitrification in Nakdong River Estuary. To understand general patterns and trends of biogeochemical processes of sediments in the Nakdong River Estuary, we categorized biogeochemical fluxes measured in this study according to direction and sizes of fluxes. Type 1(high oxygen and inorganic nitrogen fluxes into the sediments and high denitrification) occurred in summer, whereas Type 2(low oxygen and inorganic nitrogen fluxes into the sediments and low denitrification) occurred in rest of the season. Intertidal flat sediments seem to react sensitively to influence of freshwater from the Nakdong River.

• Economic and Environmental Geology
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• v.43 no.1
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• pp.43-52
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• 2010

The geochemical and nitrogen isotopic analyses for shallow groundwater of Ogcheon area were carried out to characterize the geochemical characteristics of the groundwater and to identify the source of nitrate. Groundwater shows a neutral pH to weakly alkalic condition with pH values ranging from 6.9 to 8.4. The average of EC, Eh and DO is $344.2\;{\mu}s/cm$, 195 mV, 4 mg/L, respectively. According to piper diagram, chemical composition of groundwater is dominantly characterized by Ca-$HCO_3$ type. On the other hand, groundwater type in the study area include Ca-Cl+$NO_3$ type that were highly influenced by agricultural activities. $NO_3$-N concentration of the collected samples(n=45) range from 12.4 to 34.2 mg/l. These data show that the $NO_3$-N concentration exceeds Korea Drinking Water Standard (10 mg/l). The $\delta^{15}N-NO_3$ values range from $2.7^{\circ}/_{\circ\circ}$ to $18.8^{\circ}/_{\circ\circ}$. The enrichments of heavy isotope in the groundwater indicate that major origin of nitrate pollution were associated with animal and human waste. Also the denitrification may have partly contributed as one of the sources of nitrogen.

• Economic and Environmental Geology
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• v.42 no.6
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• pp.527-539
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• 2009

The Kumho River flows through volcanic and sedimentary rocks at upstream and downstream regions and also through industrial district including dyeing complex before it meets the Nakdong River, and as a result, many factors can influence the geochemistry of river water. The concentrations of dissolved ions generally increased as it flows downstream. The concentrations of cations are in the order of Ca>Na>Mg>K, and those of anions are $HCO_3$>$SO_4$>Cl>$NO_3$. These results show that the weathering of sandstone and shale containing carbonate including calcite caused the enrichment of Ca and $HCO_3$. At first 4 sampling sites, Si contents are relatively high mainly due to the weathering of silicate minerals of volcanic rocks. However, Na and $SO_4$ contents are higher at downstream sites due to the industrial and municipal sewage. Piper diagram also shows that the geochemical patterns changed from Ca-$HCO_3$ to Ca-Cl/Ca-$SO_4$ and Na-Cl/Na-$SO_4$ type. When comparing the samples collected in May and July, the concentrations of dissolved ions in July are generally lower than those in May, which indicates that dilution by precipitation played an important role. In July the relative concentration of Ca increased, indicating that Ca in soils probably from fertilizer were mixed into the river water by precipitation. The river waters are mainly from precipitation. The dissolved ions are mainly from weathering of carbonate minerals and pollutants from municipal sewage and discharged water from industrial complex. The composition of oxygen and deutrium isotope in July showed higher values, which is contrary to the amount effect, maybe due to Youngchon Dam. The nitrogen isotope showed lower values in July than those in May, which can be interpreted to indicate mixing of nitrate from soils and fertilizer in the cultivated land by the heavy rain. The isotope composition of nitrate increased downstream, indicating that the influence of sewage and animal manure also increased downstream.

• Economic and Environmental Geology
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• v.42 no.6
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• pp.575-589
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• 2009

Groundwater has been extracted for irrigation in Sacheon-Hadong area, which is close to the South Sea. We analyzed chemical components of groundwater to examine the effects of seawater intrusion and agricultural activities in the study area. Most groundwater samples displayed the Na/Cl concentration ratios similar to that of seawater (0.55) with an increasing tendency of electrical conductivity ($227-7,910\;{\mu}S/cm$) towards the coast. In addition, statistical interpretation of the cumulative frequency curves of Cl and $HCO_3$ showed that 30.1% of the groundwater samples were highly affected by seawater intrusion. Groundwaters in the study area mostly belonged to the Ca-Cl and Na-Cl type, demonstrating that they were highly influenced by seawater intrusion and cation exchange. The result of oxygen-hydrogen isotope analysis demonstrated slightly higher $\delta^{18}O$ ((-8.53)-(-6.13)‰) and ${\delta}D$ ((-58.7)-(-43.7)‰) comparing to mean oxygen-hydrogen isotope ratios in Korea. As a result of nitrogen isotope analysis, the $\delta^{15}N-NO_3$ values ((-0.5)-(19.1)‰) indicate two major sources of nitrate pollution (organic nitrogen in soil and animal and human wastes) and mixed source of the two. However, denitrification may partly contribute as a source of nitrogen. According to factor analysis, four factors were identified among which factor 1 with an eigenvalue of 6.21 reflected the influence of seawater intrusion. Cluster analysis indicated the classification of groundwater into fresh, saline, and mixed ones.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.16 no.2
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• pp.81-96
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• 2011

Sediment oxygen demand(SOD) and denitrification rates were measured in four major estuaries(Suncheon Bay, Seomjin river estuary, Goseong stream estuary and Masan Bay) in south coast of Korean peninsula from March of 2009 to May 2010 to estimate organic matter cleaning capacity. SOD was estimated from the temporal dissolved oxygen concentration change and isotopic pairing technique was employed to measure denitrification. Sediment oxygen demand(SOD) was ranged from -5.1 to 24.6 mmole $O_2m^{-2}d^{-1}$ and denitrification rate was ranged from 0.0 to 3.9 mmole $N_2m^{-2}d^{-1}$in the study area. SOD was the highest in Masan Bay(-2.2 to 19.2, average = 10.2 mmole $O_2m^{-2}d^{-1}$) and Suncheon, Goseong, Tae-an and Seomjin followed. Denitrification was also the highest in Masn Bay(0.0 to 3.9, average = 1.0 mmole $N_2m^{-2}d^{-1}$) and Goseong, Seomjin, Suncheon and Taean followed. The effect of benthic photosynthesis by microphytobenthos on denitrification was evident in some season of Tae-an, Seomjin, and Masn Bay. The increased oxygen level produced by photosynthesis stimulated nitrification without severe adverse effect on denitrification and, as a result, coupled nitrification and denitrification was enhanced in these areas. A difference of seasonal patterns of denitrification at each site depended on relative importance of denitrification on different nitrate source($D_w$: nitrate from water column and $D_n$: nitrated produced during nitrification). Denitrification was maximum during spring in Goseong, Suncheon and Masan Bay. On the contrary, denitrification was the highest during summer in Tae-an and Seomjin estuary.

• Journal of the Korean Society of Groundwater Environment
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• v.6 no.4
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• pp.171-179
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• 1999

The $CO_2$-rich waters in the Chojeong area are characterized by low pH (5.0~5.8), high $CO_2$pressure (about 1 atm) and high amounts of total dissolved iou (up to 989 mg/L) and chemically belong to Ca-HC $O_3$type. The oxygen. deuterium and tritium isotope data indicate that the mixing process occurred between $CO_2$-rich water and surface water and/or shallow groundwaters and also suggest that the $CO_2$-rich water has been derived from meteoric waters. According to $\delta$$^{13}$ C values (-8.6~-5.3$\textperthousand$). the $CO_2$ in the water is attributed from deep seated $CO_2$gas. The high dissolved carbon (-14.4~-6.8$\textperthousand$. $\delta$$^{13}$ C) in groundwater of the granitic terrain might be affected by $CO_2$-rich water, whereas the dissolved carbon (-17.9~-15.2$\textperthousand$. $\delta$$^{13}$ C) in groundwater of the metamorphic terrain is likely controlled by soil $CO_2$ and from the reaction with calcite in phyllite. Sulfur isotope data (＋3.5~＋11.3$\textperthousand$,$\delta$$^{34}$ $S_{SO4}$) also support the mixing process between $CO_2$-rich water and shallow groundwater. Strontium isotopic ratio ($^{87}$ Sr/$^{86}$ Sr) indicates that the $CO_2$-rich water (0.7138~0.7156) is not related to vein calcite (0.7184) of Buak mine or calcite (0.7281~0.7346) in phyllite. By nitrogen isotope ($\delta$$^{15}$ $N_{NO3}$) the sources of nitrogen (up to 55.0 mg/L, N $O_3$) in the $CO_2$-rich water are identified as fertilizer and animal manure. It also indicates the possibility of denitrification during the circulation of nitrogen in the Chojeong area. The possible evolution model of the $CO_2$-rich water based on the hydrochemical and environmental isotopic data was proposed in this study. The $CO_2$-rich waters from the Chojeong area were primarily derived from the reaction with granite by supply of deep seated $CO_2$. and then the $CO_2$-rich water was mixed and diluted with the local groundwater.ter.