酸性降下物 및 山林地域 流出水가 住岩湖 水質에 미치는 影響

Abstract

Atmospheric pollutants were regarded as non-pointed source pollutants, since nitrogen compounds such as ammonium and nitrate among atmospheric pollutants influence on soil and water quality. It is significant to measure precipitation amount and estimate nitrogen precipitation unit, because chemical composition and precipitation amount within Juam basin are different from other areas. Outflow characteristics of rainfall in forest area varied according to tomography, geological features, species of trees, shape of forest trees and humic deposit. Therefore the area of forest zone near Juam lake by forest types was examined and outflow amount from forest zone was estimated through examining rainfall outflow rate by forest types. Rainfall by time, outflow by forest types, area of survey zone and water quality of runoff were investigated and unit pollutant loading factor by forest types was calculated. Non-pointed pollutant loading of forest zone near Juam lake estimated on the basis of those values could be applied as basic data to establish the countermeasure for management of Juam basin. We accomplished a comparative study on the water quality of runoff from forest zone by forest tree types (broad-leaved, conifer, mixed and herbage area), water form valley, 3 major streams flowed to Juam lake and main stem of Juam lake. And the relationship between pollutants from forest area and water quality of water from valley, stream and Juam lake was investigated. Conclusions of this study were as follows: (1) Annual soluble cation amount among precipitation materials was Na+ > Ca2+ > NH4+ > Mg2+ > K+, and annual average concentration of each cation was Na+ 96.84μeq/L, which occupied about 35% of whole cation, Ca2+ 74.71μeq/L, Mg2+ 58.05μeq/L, NH4+ 53.94μeq/L and K+ 19.92μeq/L. Annual soluble anion amount was SO42- > Cl- > NO3- , and annual average concentration was SO42- 73.63μeq/L, which occupied about 35% of whole cation, Cl- 56.48μeq/L and NO3- 10.84μeq/L. (2) Nitrogen precipitation amount of Juam basin was 78,714 kg/month(August, 2005), 44,763 kg/month(February, 2005) and 40,897 kg/month(April, 2005) in the order of high amount and 11,960 kg/month(September, 2004), 12,972 kg/month(October, 2004), 14,907 kg/month(December, 2004), and 16,125 kg/month(November, 2005) in the order of low amount. The difference between the highest and the lowest month was about 6.5 times. The share rate of nitrogen loading by forest tree types was 58.13% in conifer, 23.29% in mixed and 18.49% in broad-leaved area. Monthly average nitrogen loading of Juam basin during one year from September, 2004 was 31,879 kg/month and annual loading was 382,547 kg/year. (3) Water quality analysis results of runoff by forest tree types were as follows. Annual BOD, CODMn and CODCr concentration of runoff in conifer area was high, and particle and biological recalcitrant compounds were flowed highly. SS, T-N and T-P concentration was high in runoff from broad-leaved area, and biological degradable compounds was flowed. Water quality of water from valley was maintained good under non-rainfall and could be utilized as fresh drinking water. Through water quality standard investigation, a countermeasure establishment was necessary to secure a good quality of drinking water BOD, CODMn, and CODCr concentration of Bo-sung river was higher 1.5 times than other 2 streams, and because of high T-N, and T-P concentration in Songgwang stream, the management for this was necessary. (4) Unit pollutants loading factor of non-pointed pollutants was the highest in broad-leaved area as SS 160.7 kg/ha/ year, BOD 9.8 kg/ha/year, CODMn 14.2 kg/ha/year, CODCr 200.8 kg/ha/year, T-N 6.248 kg/ha/year, and T-P 0.178 kg/ha/year, while was the lowest in conifer area as SS 29.5 kg/ha/year, BOD 6.0 kg/ha/year, CODMn 7.9 kg/ha/year, CODCr 80.6 kg/ha/year, T-N 2.263 kg/ha/year, and T-P 0.122 kg/ha/year. (5) Non-pointed pollutants loading by forest tree types was the highest in conifer area as BOD 127.10ton/year, CODMn 167.67ton/year, CODCr 1,699.95ton/year, T-N 47.74ton/year and T-P 2.57ton/year, while SS loading was the highest in broad-leaved as 1,078.60ton/year. (6) The physico-chemistry characteristics of humics are below. The SUVA(Specific Ultra-vlolet Absorbance) of forest tree types was in the order of an conifer, broad-leaved tree, herbage and mixed area. The SUVA of rivers was in the order of Bo-sung river, Songgwang stream and Dong-bog stream. Middle and high molecular compounds were rich in soil, while low and middle molecular compounds were in Juam lake. Humic materials in soil and Juam lake had similar structure characteristics, and aliphatic and aromatic compounds were detected in soil humics but not aliphatic compounds in Juam lake. 7) The correlation coefficient between DOC and Chlorophyll-a was significant (R2 = 0.714). Although the upperstream and downstream of Juam lake were affected by non-point source of forest reigons, SUVA in Juam lake was low probably due to decomposition and transformation of the outside origin substances inflowed.