한국농림기상학회지, 제 12권 제4호(2010) (pISSN 1229-5671, eISSN 2288-1859)
Korean Journal of Agricultural and Forest Meteorology, Vol. 12, No. 4, (2010), pp. 277~288
ⓒ Author(s) 2014. CC Attribution 3.0 License.

다중연직농도시스템(Multi-Level Profile System)을 이용한 수증기와
이산화탄소 시료채취 및 안정동위원소 조성 분석

이동호(1), 김수진(1), 천정화(2), 김 준(1)
연세대학교 대기과학과/지구환경연구소, (1)국립산림과학원

(2010년 09월 03일 접수; 2010년 10월 04일 수정; 2010년 10월 04일 수락)

Air Sampling and Isotope Analyses of Water Vapor
and CO2 using Multi-Level Profile System

Dongho Lee(1), Su-Jin Kim(1), Jung-Hwa Cheon(2), Joon Kim(1)
(1)Department of Atmospheric Sciences/Gloal Environment Laboratory, Yonsei University, Seoul 120-749, Korea
(2)Korea Forest Research Institute, Seoul 130-712, Korea

(Received September 03, 2010; Revised October 04, 2010; Accepted October 04, 2010)

The multi-level H2O/CO2 profile system has been widely used to quantify the storage and advection effects on energy and mass fluxes measured by eddy covariance systems. In this study, we expanded the utility of the profile system by accommodating air sampling devices for isotope analyses of water vapor and CO2. A pre-evacuated 2L glass flask was connected to the discharge of an Infrared Gas Analyzer (IRGA) of the profile system so that airs with known concentration of H2O and CO2 can be sampled. To test the performance of this sampling system, we sampled airs from 8 levels (from 0.1 to 40 m) at the KoFlux tower of Gwangneung deciduous forest, Korea. Air samples in the 2L flask were separated into its component gases and pure H2O and CO2 were extracted by using a vacuum extraction line. This novel technique successfully produced vertical profiles of δD of H2O and δ13C of CO2 in a mature forest, and estimated δD of evapotranspiration (δDET) and δ13 of CO2 from ecosystem respiration (δ13Cresp) by using Keeling plots. While technical improvement is still required in various aspects, our sampling system has two major advantages over other proposed techniques. First, it is cost effective since our system uses the existing structure of the profile system. Second, both CO2 and H2O can be sampled simultaneously so that net ecosystem exchange of H2O and CO2 can be partitioned at the same temporal resolution, which will improve our understanding of the coupling between water and carbon cycles in terrestrial ecosystems.

Keyword: Multi-level profile system, Isotopes, Air sampling, H2O, CO2, Deciduous forest



다중 수증기/이산화탄소 연직농도시스템(이하 프로파일시스템)은 에디공분산 방법에 의해 측정된 에너지 및 물질 플럭스에 대한 저류항 및 이류의 영향을 정량화하기 위해 광범위하게 이용되고 있다. 본 연구에서는 현재 사용되고 있는 프로파일시스템의 용도를 보다 확장하여 안정동위원소 분석을 위한 공기시료 채취에 활용하였다. 프로파일시스템에서 기체농도 측정에 이용되는 적외선기체분석기의 유출부에 2L 용량의 진공 플라스크를 연결하여 수증기와 이산화탄소의 농도가 측정된 공기시료가 채취되도록 개조하였다. 이 방법의 적용성을 검증하기 위하여 광릉 활엽수림 내에 설치되어 있는 플럭스타워에서 8개의 높이(0.1~40m)로 부터 공기시료를 채취하였다. 플라스크에 채취된 공기 시료로부터 실험실에서 진공추출라인을 이용하여 순수한 수증기와 이산화탄소가 분리되었고, 질량분석기를 이용하여 수증기의 수소 안정동위원소 조성 그리고 이산화탄소의 탄소 안정동위원소 조성을 각각 측정하였다. 이와 같은 방법으로 얻어진 자료를 이용하여 산림 내 수증기의 수소 안정동위원소 조성과 이산화탄소의 탄소 안정동위원소 조성의 수직적 분포를 확인하였고, 아울러 Keeling plot 을 적용하여 증발산된 수증기의 수소 동위원소 조성 및 생태계 호흡에 의해 발생된 이산화탄소의 탄소동위원소 조성을 산출하였다. 비록 현단계에서 여러 가지 기술적인 개선점이 존재하지만, 본 연구에서 이용한 방법은 기존에 활용되고 있는 방법과 비교하여 두 가지 장점이다. 첫째, 이 방법은 기존에 운용되고 있는 프로파일 시스템의 구조를 그대로 활용함으로써 상대적으로 저비용으로 이용이 가능하다. 둘째, 수증기와 이산화탄소의 동시 시료채취와 동위원소 분석이 가능하여 증발산 및 순생태교환량 구성요소의 구분이 동일한 시간적 해상도로 이루어질 수 있다. 이러한 결과는 생태계 물과 탄소 순환 과정의 상호 관련성에 대한 보다 향상된 이해를 위한 기본 자료로 활용될 수 있을 것으로 기대된다.


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