Physiochemical characteristics of soils and water-columns in different freshwater constructed wetlands under alternative hydrologic regime

Abstract

Wetlands are distinguished by the presence of water, unique nutrient cycles, and microbe activities. To explore the effects of hydrologic regimes on nutrient cycles in freshwater wetlands, I measured environmental parameters including extracellular enzyme activities in constructed marsh-pond wetlands in Korea. Soil and water samples were collected in two mesocosms with different water regimes from May, 2006 to October, 2006. On a weekly basic, the high nitrogen mineralization and organic matter accumulation were observed in soil under drying treatment, significantly in marsh (P<0.05). Release of available phosphate from sediment was observed under drying event, which prolonged for following rewetting event. Extracellular enzyme activities (β-glucosidase, N-acetylglucosaminidase, arylsulfatase, and phosphatase) were also activated by drought. In addition, the activities were higher in marsh than those in pond. Even after rewetting, the phosphatase activity was still activated. Before drought, marshes showed higher removal rate of nutrient, but that capacity was decreased more severely than those of ponds after undergoing hydrologic changes. Enhanced sulfate releasing and decreased nitrate removal capacity of sediment beds during rewetting period were observed obviously (P<0.05). The Principal Component Analysis (PCA) of some correlated environmental variables showed separated clusters of samples which were influenced by hydrologic changes. This study suggests that changing of hydrologic regime in wetland can affect on nutrient cycles particularly and environmental functions (water amelioration, C sink) of wetlands generally.;습지는 물의 저장과 물질의 순환, 그리고 미생물의 활성 등으로 구분될 수 있다. 본 연구에서는 수문학적 특성이 습지의 물질순환에 미치는 영향을 알아보기 위해 pond형 습지 (연못형) 반응조에서 미생물의 체외효소활성도를 포함한 여러 가지 환경인자들을 측정하였다. 실험은 체류시간과 수심을 조절한 두 개의 서로 다른 반응조에서 2006년 5월 ~ 10월까지 토양시료와 물시료를 채취하여 진행하였다. 실험결과, 습지 퇴적물에서 배출되는 이용가능 한 phosphate는 혐기조건에서 관찰되었고, 습지 반응조를 다시 호기조건으로 전환할 때까지 계속되었다. 미생물의 체외효소활성도 (β-glucosidase, N-acetylglucosaminidase, arylsulfatase, phosphatse)는 혐기조건에서 활발했다. 그리고 pond형 습지에서보다 marsh형 습지에서 미생물의 체외효소활성도가 더 높았다. 또한 습지 반응조를 다시 호기조건으로 전환한 후에도 phosphatase의 활성이 여전히 활발한 것으로 나타났다. 혐기조건으로 전환하기 전 marsh의 영양염류 제거효율이 높은 것으로 나타났으나, 혐기조건으로 전환한 후에는 pond보다 더 감소하였다. 따라서 습지의 수문학적 조건의 변화가 습지의 일반적인 물질순환과 환경기능 (수질개선, 탄소 저장)에 영향을 미칠 것으로 사료된다.