Comparative Analysis of Heavy Metal Contamination, Mineral Composition and Spectral Characteristics of White, Reddish Brown and Mixed Precipitates Occurring at Osip Stream Drainage, Gangwondo, South Korea

강원도 오십천 수계에 분포하는 백색침전물, 적갈색침전물 및 혼합침전물의 중금속 오염, 광물조성 및 분광학적 특성의 비교분석

Abstract

This study analyzed precipitation environment, heavy metal contamination, and mineral composition of white, reddish brown and mixed precipitates occurring at the Osip stream drainage, Gangwondo. Furthermore, spectral characteristics of the precipitates associated with heavy metal contamination and mineral composition was investigated based on spectroscopic analysis. The pH range of the precipitates was 4.43-6.91 for white precipitates, 7.74-7.94 for reddish brown precipitates, and 7.59-7.9 for the mixed precipitates, respectively. XRF analysis revealed that these precipitates were contaminated with Ni, Cu, Zn, and As. The white precipitates showed high Al concentration compared to reddish brown precipitates as much as 3.3 times, and the reddish brown precipitates showed high Fe concentration compared to white precipitates as much as 15 times. XRD analysis identified that the mineral composition of the white participates was aluminocoquimbite, gibbsite, quartz, saponite, and illite, and that of reddish brown precipitates was aluminum isopropoxide, kaolinite, goethite, dolomite, pyrophyllite, magnetite, quartz, calcite, pyrope. The mineral composition of the mixed precipitates was quartz, albite, and calcite. The spectral characteristics of the precipitates was manifested by gibbsite, saponite, illite for white precipitates, goethite, kaolinite, pyrophyllite for reddish brown precipitates, and albite for the mixed precipitates, respectively. The spectral reflectance of the precipitates decreased with increase in heavy metal contamination, and absorption depth of the precipitates indicated that the heavy metal ions were adsorbed to saponite and illite for white precipitates, and goethite and magnetite for reddish brown precipitates.

본 연구는 강원도 오십천 수계에 형성된 백색, 적갈색 그리고 두 침전물이 혼합된 침전물을 대상으로 침전환경을 파악하고, 중금속 오염도 및 광물학적 분석을 수행하였다. 또한, 분광학적 분석을 통해 수계침전물의 중금속 오염도와 광물조성에 따른 분광특성을 고찰하였다. 백색침전물, 적갈색침전물 및 혼합침전물이 형성된 하천수의 pH 범위는 각각 4.43-6.91, 7.74-7.94와 7.59-7.9로 나타났다. X선 형광분석 결과, 이들 침전물은 니켈, 구리, 아연 및 비소에 대해 오염도가 높은 것으로 확인되었다. 백색침전물은 적갈색침전물 내 알루미늄의 농도에 비해 약 3.3배 높았으며, 적갈색침전물은 백색침전물 내 철의 농도보다 약 15배 부화되었다. X선 회절분석 결과 백색침전물은 알루미노코큠바이트, 깁사이트, 석영, 사포나이트, 일라이트의 광물로 구성되며, 적갈색침전물은 알루미늄 이소프로폭사이드, 고령토, 침철석, 돌로마이트, 엽랍석, 자철석, 석영, 방해석, 홍석류석으로 이루어졌으며, 혼합침전물은 석영, 조장석, 방해석의 광물로 구성된다. 백색침전물은 깁사이트, 사포나이트, 일라이트에 의해, 적갈색침전물은 침철석, 고령토, 엽랍석에 의해, 혼합침전물은 조장석에 의해 분광학적 특성이 발현되는 것으로 판단된다. 중금속 오염도가 높아짐에 따라 분광반사도가 낮아지는 경향을 보였으며, 흡광깊이를 분석한 결과, 백색침전물 및 적갈색침전물에서 검출된 중금속은 각각 사포나이트와 일라이트, 침철석과 자철석에 흡착된 결과로 예상된다.

Fig. 1. Location map of the study area.

Fig. 2. Flow chart of methods carried out for this study.

Fig. 3. Field photographs of white precipitates(a), reddish brown precipitates(b), the confluence of white precipitate and reddish brown precipitate(c) and mixed precipitates(d) in this study area.

Fig. 4. X-ray diffraction pattern of white precipitates(a)-(b), mixed precipitate(c) and reddish brown precipitates(d)-(f)collected from the bottom of the stream.

Fig. 5. The visible-near infrared-shortwave infrared(VNIR-SWIR) reflectance spectra and hull-quotient spectra of white,reddish brown and mixed precipitates.

Fig. 6. The average visible-near infrared-shortwave infrared(VNIR-SWIR) reflectance spectrum of white precipitates and reference spectra of illite, saponite and gibbsite from standard spectral library data(Clark et al., 2007; Baldridge et al., 2009).

Fig. 7. The average visible-near infrared-shortwave infrared(VNIR-SWIR) reflectance spectrum of reddish brown precipitates and reference spectra of kaolinite, pyrophyllite and goethite from standard spectral library data(Clark et al.,2007; Baldridge et al., 2009).

Fig. 8. The average visible-near infrared-shortwave infrared(VNIR-SWIR) reflectance spectrum of mixed precipitates and reference spectra of albite from standard spectral library data(Clark et al., 2007; Baldridge et al., 2009).

Fig. 9. The average visible-near infrared-shortwave infrared(VNIR-SWIR) reflectance and hull-quotient spectra of white precipitate groups.

Fig. 10. The average visible-near infrared-shortwave infrared(VNIR-SWIR) reflectance and hull-quotient spectra of reddish brown precipitate groups.

Fig. 11. The average visible-near infrared-shortwave infrared(VNIR-SWIR) reflectance and hull-quotient spectra of mixed precipitate groups.

Table 1. The pH values of stream water in which white precipitates are distributed

Table 2. The pH values of stream water in which reddish brown precipitates(left) and mixed precipitates(right) are distributed

Table 3. Sediment pollution evaluation standard for Ni, Cu, Zn and As established by NIER(2015) (unit: ppm)

Table 4. Minimum, median, maximum and mean concentrations of Ni, Cu, Zn and As(unit: ppm) for each precipitate

Table 5. Minimum, median, maximum and mean concentrations of Ni, Cu and Zn(unit: ppm), and calculated pollution index(PI) for each white precipitate group

Table 6. Minimum, median, maximum and mean concentrations of Ni, Cu, Zn and As (unit: ppm), and calculated pollution index(PI) for each reddish brown precipitate group

Table 7. Minimum, median, maximum and mean concentrations of Ni, Cu and Zn (unit: ppm), and calculated pollutionindex (PI) for each mixed precipitate group

Table 8. Average concentration of stream sediment for Al, Mn and Fe and minimum, median, maximum and mean concentrations for each precipitate(unit: %)