• 한국대기환경학회지
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• 제13권1호
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• pp.9-18
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• 1997

Precipitation samples were collected by the wet- only event sampling method from Seoul during September 1991 to April 1995. These samples were analyzed for the concentrations of the major ionic components (N $O_3$$^{[-10]}$ , N $O_2$$^{[-10]}$ , S $O_4$$^{2-}$, C $l^{[-10]}$ , $F^{[-10]}$ , N $a^{＋}$, $K^{+}$, $Ca^{2＋}$, $Mg^{2＋}$, and N $H_4$$^{＋}$), pH, and electric conductivity. During the study period, a total of 182 samples were collected, but only 163 samples were used for the data analysis via quality assurance of precipitation chemistry data. The volume-weighted pH was found to be 4.7. The major acidifying species from our precipitation studies were identified to be non-seasalt sulfate (84$\pm$9 $\mu$eq/L) and nitrate (24$\pm$2 $\mu$eq/L) except for chloride. Because the Cl/Na ratio in the precipitation was close to the ratio in seawater. If all of the non-seasalt sulfate and nitrate were in the form of sulfuric and nitric acids, the mean pH in the precipitation could have been as low as 3.7 lower than the computed value. Consequently, the difference between two pH values indicate that the acidity of precipitation was neutralized by alkaline species. The equivalent concentration ratio of sulfate to nitrate was 3.5, indicating that sulfuric and nitric acids can comprise 78％ and 22％ of the precipitation acidity, respectively. Analysis of temporal trend in the measured acidity and ionic components were also performed using the linear regression method. The precipitation acidity generally showed a significantly decreasing trend, which was compatible with the pattern of the ratio (N $H_4$$^{＋}$＋C $a^{2＋}$)/ (nss-S $O_4$$^{2-}$＋N $O_3$$^{[-10]}$ ).).

• 분석과학
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• 제33권1호
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• pp.33-41
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• 2020

Wet precipitation samples were collected in Jeju City and Mt. Halla-1100 site (a site at an altitude of 1100 m on Mt. Halla) during 2011-2013, and their major ionic species were analyzed to examine the chemical composition and characteristics. A comparison of ion balance, electric conductivity, and acid fraction of precipitation revealed correlation coefficients in the range of r = 0.950~0.991, thereby implying the high quality of analytical data. Volume-weighted mean pH and electric conductivity corresponded to 4.86 and 25.5 µS/cm for Jeju City, and 4.98 and 15.1 µS/cm for Mt. Halla-1100 site, respectively. Ionic strengths of the wet precipitation in Jeju City and Mt. Halla-1100 site corresponded 0.3 ± 0.5 and 0.2 ± 0.2 mM, respectively, thereby indicating that more than 30 % of total precipitation was within a pure precipitation criteria. The precipitation with a pH range of 4.5 - 5.0 corresponded to 40.8 % in Jeju City, while the precipitation with a pH range of 5.0 - 5.5 corresponded to 56.9 % in Mt. Halla-1100 site, thereby indicating slightly more weak acidity than that in Jeju city. The volume-weighted mean concentration (µeq/L) of ionic species was in the order of Na⁺ > Cl^- > nss-SO₄^2- > NO₃^- > Mg²⁺ > NH₄⁺ > H⁺ > nss-Ca²⁺ > PO₄^3- > K⁺ > CH₃COO^- > HCOO^- > NO₂^- > F^- > HCO₃^- > CH₃SO₃^- at Jeju City area, while it corresponded to Na⁺ > Cl^- > nss-SO₄^2- > NO₃^- > NH₄⁺ > H⁺ > Mg²⁺ > nss-Ca²⁺ > PO₄^3- > CH₃COO^- > K⁺ > HCOO^- > NO₂^- > F^- > HCO₃^- > CH₃SO₃^- at Mt. Halla-1100 site. The compositions of sea salts (Na⁺, Cl^-, Mg²⁺) and secondary pollutants (NH₄⁺, nss-SO₄^2-, NO₃^-) corresponded to 66.1 % and 21.8 %, respectively, in Jeju City and, 49.9 % and 31.5 %, respectively, in Mt. Halla-1100 site. The acidity contributions in Jeju City and Mt. Halla-1100 site by inorganic acids, i.e., sulfuric acid and nitric acid, corresponded to 93.9 % and 91.4 %, respectively, and the acidity contributions by organic acids corresponded to 6.1 % and 8.6 %, respectively. The neutralization factors in Jeju City and Mt. Halla1100 site by ammonia corresponded to 29.8 % and 30.1 %, respectively, whereas the neutralization factors by calcium carbonate corresponded to 20.5 % and 25.2 %, respectively. From the clustered back trajectory analysis, the concentrations of most ionic components were higher when the airflow pathways were moved from the continent to Jeju area.

• 한국환경복원기술학회지
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• 제7권1호
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• pp.40-49
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• 2004

This work carried out to define the characteristic of Cymbidium kanran habitat at Mt. Halla in Jejudo, Korea from the ecological point of view including geological and topographical features, air and soil temperature, relative humidity, fluctuations of light intensity, habitat vegetation, distribution altitude, area limit, and etc. And another goal of this study consider the conservation counterplan of the cymbidium habitat. Natural distribution areas of the cymbidium were observed more abundantly on the well drained south and east-facing slopes. Soil acidity was ranged from pH 4.1 to 5.3, and electric conductivity was ranged from 176.4 to 299.9 us/cm (average 215.3 us/cm). Base-saturation percentage of the habitat soil was below 50%, bulk density 0.42g/$cm^2$, particle density 2.05g/$cm^2$, humus content 26%, total nitrogen 0.82%, available phosphate 4.2 mg/kg, exchangeable potassium 0.63 Cmol/kg, calcium 0.44 Cmol/kg and magnesium 0.67 Cmol/kg. Annual mean air temperature was $15.4^{\circ}C$, however, air temperature was ranged $11.7{\sim}18.2^{\circ}C$ in spring, $21.2{\sim}23.8^{\circ}C$ in summer, $12.8{\sim}22.0^{\circ}C$ in fall and $5.5{\sim}7.8^{\circ}C$ in winter season. Annual mean soil temperature at depth of 10cm was $13.2^{\circ}C$ And minimum value was recorded $4.7^{\circ}C$ on January, and maximum value $22.5^{\circ}C$ on August. Relative humidity was ranged 90.8~94.7% in summer, 80.8~91.5% in fall and 77.6~84.2% in winter season. Minimum value was 56.5% on December, and maximum value was 100% on July and August. Light intensities were ranged from 400 to 1,800 lux at the greater part of Cymbidium kanran sites in Jejudo. Summer regarded as an lower light intensities was recorded to be range of 500~600 lux; however, autumn and winter were shown higher light regimes ranged from 3,500 to 3,800 lux. Therefore, one must be suprised that the cymbidium grow at the light condition of 6 lux (minimum) or 10,000 lux (maximum). Tree species keeping higher frequency rate and density were Eurya japonica, Camellia japonica, Castanopsis cuspidata, Carpinus laxiflora and Pinus densiflora. Number of trees growing in a 5${\times}$5m quardrat was 35 as an average, and proportion of evergreen versus deciduous was 5:1. Distribution altitude of the orchid habitat was ranged from 120m (low) to 840m (high) from sea level on the south facing slope of Mt. Halla, and was ranged eastern borderline of Gujwaup, Bukjejugun to western boundaries of Jungmundong, Seogwipo city. For the stable conservation of Cymbidium kanran habitat, sunlight regimes must be increased more by means of cutting trees or twigs in the site.

• 상하수도학회지
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• 제35권6호
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• pp.417-424
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• 2021

Algal bloom is an ongoing issue in the management of freshwater systems for drinking water supply, and the chlorophyll-a concentration is commonly used to represent the status of algal bloom. Thus, the prediction of chlorophyll-a concentration is essential for the proper management of water quality. However, the chlorophyll-a concentration is affected by various water quality and environmental factors, so the prediction of its concentration is not an easy task. In recent years, many advanced machine learning algorithms have increasingly been used for the development of surrogate models to prediction the chlorophyll-a concentration in freshwater systems such as rivers or reservoirs. This study used a light gradient boosting machine(LightGBM), a gradient boosting decision tree algorithm, to develop an ensemble machine learning model to predict chlorophyll-a concentration. The field water quality data observed at Daecheong Lake, obtained from the real-time water information system in Korea, were used for the development of the model. The data include temperature, pH, electric conductivity, dissolved oxygen, total organic carbon, total nitrogen, total phosphorus, and chlorophyll-a. First, a LightGBM model was developed to predict the chlorophyll-a concentration by using the other seven items as independent input variables. Second, the time-lagged values of all the input variables were added as input variables to understand the effect of time lag of input variables on model performance. The time lag (i) ranges from 1 to 50 days. The model performance was evaluated using three indices, root mean squared error-observation standard deviation ration (RSR), Nash-Sutcliffe coefficient of efficiency (NSE) and mean absolute error (MAE). The model showed the best performance by adding a dataset with a one-day time lag (i=1) where RSR, NSE, and MAE were 0.359, 0.871 and 1.510, respectively. The improvement of model performance was observed when a dataset with a time lag up of about 15 days (i=15) was added.

• 분석과학
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• 제29권1호
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• pp.19-28
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• 2016

2009~2014년에 제주지역의 강수시료(n=284)를 채취하여 주요 이온 성분을 분석하였다. 분석 정확도 확인을 위해 이온수지, 전기전도도, 산분율 비교법으로 회귀분석을 실시한 결과, 이들의 상관계수는 0.927~0.983의 범위로 양호한 직선성을 나타내었다. 강수의 부피가중평균 pH 4.9, 전기전도도는 22.7 µS/cm, 이온세기는 0.27±0.38 mM로 시료 중 약 35.9 %가 순수한 빗물 수준을 보였다. 강수 이온성분의 부피가중 평균농도(µeq/L)는 Na⁺ > Cl⁻ > nss-SO₄²⁻ > NO₃⁻ > NH₄⁺ > Mg²⁺ > H⁺ > nss-Ca²⁺ > PO₄³⁻ > K⁺ > HCOO⁻ > CH₃COO⁻ > NO₂⁻ > F⁻ > HCO₃⁻ > CH₃SO₃⁻ 순이었다. 강수의 산성화 기여율은 황산과 질산의 기여율이 각각 54.5 %, 36.5 %인 반면에 유기산 음이온인 HCOO⁻ 와 CH₃COO⁻ 의 기여율은 각각 4.8 %, 4.2 %를 나타내어 제주지역 강수의 산성화는 유기산보다는 주로 무기산에 의해 일어나고 있음을 확인할 수 있었다. 또한 중화인자를 확인한 결과, NH₃에 의한 중화인자는 33 %를 나타내었고 CaCO₃에 의한 중화인자는 20 % 이었다.

• Current Research on Agriculture and Life Sciences
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• 제1권
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• pp.85-93
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• 1983

경북(慶北)의 낙동강수계(洛東江水系)와 동해안수계농촌(東海岸水系農村) 17개(個) 지점(地点)을 기준(基準)하여 농업용수원(農業用水源)의 수질환경(水質環境)을 조사검토(調査檢討)하여 장래(將來)의 방재대책(防災對策)에 참고하고져 조사분석(調査分析)을 실시(實施)한 바 농업용수원(農業用水源)을 기준(基準)할 때 수온상태(水溫狀態)는 수질(水質)을 저해(沮害)시킬 큰 요인(要因)이나 문제점(問題点)이 없으며 PH는 6.5~7.8의 절위에서 기준치(基準値)에 저촉되지 않으며 염도의 기준(基準)이 되는 전기전도도(電氣傳導度)도 $200{\mu}{\Omega}/cm$에 이르는 지점도 있으나 농업용수의 수질저해지점에는 미치지 못하며 BOD의 경우는 기준치 10ppm에 육박(肉迫)하는 지점(地点)이 있어 다소(多少)의 위험위협을 받고 있다. 그리고 DO의 경우는 위험기준치에 미달(未達)하고 있다. 그리고 중금속(重金屬)에 속하는 Cu, Pb, Cd 등도 아직은 위험기준치에는 미달(未達)이나 장차에는 주위의 산업(産業)과 도시발달(都市發達)에 따르는 특별(特別)한 조치가 없는 한(限) 위험조건에 이를 것으로 생각된다.

• 한국환경농학회지
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• 제38권4호
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• pp.273-280
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• 2019

BACKGROUND: The reclaimed lands for agricultural use managed by the Korean government is consisted of 17,145 hectares of lands under construction and 13,384 hectares of completed lands. In order to utilize these reclaimed lands as competitive agricultural complexes, the government is preparing to develop comprehensive development plans for multiple purposes. For rational land-use planning and soil management, information of the soil chemical properties is necessary. METHODS AND RESULTS: From 2013 to 2016, soil samples were collected from 85 representative sampling sites of the reclaimed lands and analyzed for soil chemical properties including electric conductivity (EC), pH, soil organic matter (SOM), and nutrients. The annual mean soil EC ranged from 5.1 to 8.3 dS m^-1 and have continued to decrease over the years (estimation equation with EC as dependent and year as independent variable was y =0.0736x² - 1.4985x + 9.8305, R² = 0.9753). The pH ranged from 7.3 to 7.6, which was higher than the optimum range (5.5~7.0) for agricultural soils. Soil organic matter (8 to 11 g kg^-1) was lower level than the optimum range (20~30 kg^-1). Available silicate (Av.SiO₂) ranged from 169 to 229 mg kg^-1, which was close to the minimum content (≥157 mg kg^-1) for rice paddy field. Available phosphate (Av.P₂O₅) content (24~39 mg kg^-1) was lower than the optimum range (80~120 mg kg^-1) for rice paddy field. CONCLUSION: For efficient agricultural use of reclaimed lands under government management, our results suggest that the application of organic matter and supplying deficient nutrients as well as desalinization is required.

• 한국작물학회지
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• 제41권4호
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• pp.411-419
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• 1996

보리입모중 벼 파종에 있어서 보리짚 시용에 따른 경운방법과 질소시용량별 관개수중에 용출된 각 성분함량 변화를 검토하였던 바, 그 결과를 요약하면 다음과 같다. 1. pH는 무경운재배에서는 시비수준간 차리가 없었으나 경운재배에서는 컸으며, 10일까지는 시비수준이 높을수록 pH가 높았으나 그 이후는 비슷하였다. 2. EC는 무경운에 비해 경운재배에서 높았으며, 경운의 유 ㆍ무에 관계없이 시비수준이 높을수록 EC도 높았다. 시기별로 보면 10일에 최고수준에 도달하였다가 그 후 감소경향이나, 20일에는 초기와는 달리 시비수준이 높을수록 EC가 감소하였고, 그 감소폭은 경운재배에서 컸다. 3. 용존산소는 무경운에 비해 경운에서 높았으며, 시비량이 많을수록 낮은 경향을 보였다. 경운방법별로는 무경운에서는 시용후일수가 경과됨에 따라 다소 증가하는 경향이었으며, 무처리에 비해 매우 낮았으나, 경운재배에서는 초기에 매우 높고 10일에 급격히 감소하였으며 그 후 다시 증가하였다. 4. NH$_4$-N는 경운의 유 ㆍ무에 관계없이 시비수준이 높을수록 높았으나, 20일에는 시비량간 차이는 없었다. 경운방법간에는 무경운에서는 10일까지 높고 그 후 감소를 보였으나 경운에서는 초기(5일)에 매우 높았다가 급격히 감소하였고, 15일에 다시 감소하였으나 20일에는 거의 발현되지 않았다. NO$_3$-N는 무경운에서는 처리일수 및 시비수준간의 차이가 매우 컸으며, 10일에 최고수준을 보였고, 그 후 20일까지 급격히 감소하였다. 경운구에서는 처리일수가 경과함에 따라 감소경향을 보였으나, 시비수준간 차이는 보이지 않았다. 5. PO$_4$$^{3-}$ 은 경운재배에 비해 무경운재배에서 높았으며, 두처리 모두 시비수준이 높을수록 높았으나, 무경운재배에 비하여 경운재배에서는 시일의 경과에 따라서도 차이가 크지 않았고 함량도 낮았다. 6. 양이온함량은 모두 경운 유 ㆍ무에 관계없이 시비수준이 높을수록 높은 경향을 보였고, 10일에 최고수준을 보인 후 완만한 감소를 나타냈으며, $K^{+}$, $Ca^{2+}$에 비해 $Mg^{2+}$이 보다 낮은 함량을 보였다.