(The) Demand-based climate change risk assessment and adaptation strategy development

김아라 경희대학교 대학원 2023 국내박사

As climate change has increased the intensity and frequency of heatwaves and heat-related morbidity and mortality, the livability and health of citizens have been threatened worldwide. Especially the urban inhabitants are faced with increasing risks due to the climate-induced intensification of the urban heat island (UHI) effect. To reduce the urban risks, climate change adaptation as a main component of the climate change policy has been established based on the risk assessment. Although conventional approaches to risk assessment were mainly a top-down method led by the government by surveying risk priorities to sectoral experts, it had some limitations of information with uncertainty and non-reflection of citizens' demands for about adaptation options or requirements. However, citizen science as the bottom-up approach to overcoming the limitations has recently begun to make a mark in involving citizens in knowledge generation such as monitoring. Therefore, we aimed to assess the citizens-experienced climate change risk based on their adaptation demands and then develop adaptation strategies via citizen science. There are diverse types of citizens such as the old, building managers, and officials. As each citizen type has different demands for adaptation, the risk should be set and assessed according to the adaptation demands of each citizen. It was important to design the assessment process with citizen participation to assess climate change risk customized to adaptation demands for them via citizen science. Hence, we conducted a SWOT (Strength, Weakness, Opportunity, and Threat) analysis targeting citizen science projects with good cases in the climate change adaptation field in other countries. Based on the analysis results, we suggested important implications that citizens should involve in all risk assessment processes and be appropriately rewarded for their contribution. In this study, we selected outdoor workers and pedestrians as participating citizens. As outdoor workers have to work for a living even in the heatwave, heat strain related to health was regarded as outdoor workers' demands. Pedestrians' demands were set for thermal comfort because they have complained of increasing discomfort due to the heat in their daily lives. To reflect their demands in the risk assessment, we considered heart rate (HR) as a viable proxy because it has been a widely used indicator showing physiological adaptation and physical intensity to reflect the climate change risk directly experienced by citizens in the assessment. In assessing heat strain for outdoor workers, they participated in directly exposed temperature (DET) and HR monitoring and a periodic thermal comfort survey as a psychological heat strain. We collected official air temperatures and compared them with DETs. We also quantified a physiological heat strain from workers' HR and compared physiological and psychological heat strains. On average, outdoor workers were exposed to up to 5.4℃ more heat than the official air temperature. Consequently, workers experienced the physiological heat strain on 75% of the workdays. The influential factors on physiological heat strain occurrence were age and work year. However, age was the most critical factor, considering that the work year tends to increase by age. A mismatch was observed between physiological and psychological heat strains in older participants as a result of heat acclimatization. Therefore, a wearable sensor-based early-warning system should be developed regarding personal characteristics such as age and work year, along with heart rate. Regarding the pedestrians' thermal comfort evaluation, we selected four streets with the different thermal environments by grey (building height) and green (tree canopy cover) infrastructures. Pedestrians participated in HR monitoring while walking one street a day for an hour on the selected four streets and thermal comfort survey. We compared the thermal environments among four streets and identified the influence of grey and green infrastructures on thermal environments. We also quantified and compared physiological and psychological thermal comfort on the different streets, then investigated the factors influencing physiological thermal comfort. As a result, buildings and trees improved the streets' thermal environments by blocking direct sunlight and forming shade with a cooling effect. Pedestrians were physiologically comfortable on the streets with the high building. Interestingly, a significant interaction between the grey and green infrastructure was found. In the streets of a high building, the effect of a large tree canopy cover had a negative impact on physiological thermal comfort, while in the streets of low buildings, the positive effect of tree canopy dramatically emerged. On streets where high buildings already form sufficient shade, the tree canopy hindered heat dissipation by blocking the wind path and interfering with air circulation rather than having the cooling effect of the shades formed by the tree canopy. Meanwhile, pedestrians felt the most comfortable on the street with low buildings and high tree canopy cover due to other factors such as trees' aesthetic effect to feel better. Therefore, physiological thermal comfort was a more objective index to assess pedestrians' risk. Based on the results of physiological thermal comfort, pedestrians' thermal comfort on the high building street can be increased by planting fewer trees or pruning trees to reduce canopy cover. In addition, it can help to develop a thermal comfort map informing the thermal comfort level of streets where pedestrians move. This thesis implies that climate change risk should be defined and evaluated by reflecting the demands for adaptation from the standpoint of each citizen group such as heat strain related to health for outdoor workers and physiological thermal comfort associated with daily discomfort for pedestrians. Moreover, this thesis will help to design climate change risk assessment based on citizen participation and to establish adaptation strategies for outdoor workers and pedestrians in light of our suggestions.

Environmental assessment and management in urban roadside tree-soil systems and CCS facilities for climate change adaptation and mitigation

김유진 경희대학교 대학원 2021 국내박사

Globally, climate change has drastically increased the threats from climate-related extreme events such as heatwaves, droughts, storms, and flooding. Many countries and organizations have been making various efforts to respond to it. Urban roadside tree-soil systems, one of the major green infrastructures in urban areas, can significantly alleviate the impacts of climate change through tree shading, evaporative cooling, wink blocking, and rainfall interception/infiltration. Urban roadside soils have played as a growth media for roadside trees to sustain their ecological benefits. However, reckless pruning, soil compaction, and waste dumping have seriously deteriorated the function and quality of roadside tree-soil systems. Hence, new methodologies are necessary to assess and improve the ecological benefits and quality of urban roadside tree-soil systems. Meanwhile, carbon capture and storage (CCS) is considered as an effective option to mitigate climate change until the global industrial structure is completely shifted toward low- or zero-carbon energy. For CCS technology to be successful, potential CO2 leakage needs to be detected as soon as possible, and its impacts on surrounding ecosystems need to be assessed. A bio-monitoring technique for CO2 leakage using plants could be very effective in extensive areas, especially in areas near transport pipelines. Therefore, this thesis focuses on environmental assessment and management in urban roadside tree-soil systems and CCS facilities that are promising strategies for climate change adaptation and mitigation. To estimate the benefits of urban roadside tree systems for climate change adaptation, a new methodology was suggested and applied to the specific-street segments in two major cities in Korea (street A and B). In this methodology, the benefits are categorized into building energy savings, pedestrians’ thermal-environment improvement, and surface runoff reduction. The benefits for building energy savings and surface runoff reduction by canopy interception are estimated using i-Tree eco, an existing tool for assessing urban tree benefits. The roadside trees’ benefit for improving pedestrians’ thermal environment includes thermal-comfort enhancement and thermal-illness prevention, estimated using the replacement-cost and averting-cost method, respectively. For surface runoff reduction by soil infiltration, the benefit is estimated using hydrological model, storm water management model (SWMM). As a result of applying the newly-suggested methodology, the total benefits of roadside tree systems were estimated two to four times higher than those using the conventional i-Tree eco model. This indicates that the new methodology could estimate the benefits of roadside tree systems more comprehensively by considering the missing parts in the i-Tree eco model. Finally, based on the estimated benefits, we proposed the management plans for roadside tree systems. A two-row planting could be a strategy to maximize the tree-shading effects on building energy savings and pedestrians’ thermal-environment improvement. For increasing surface runoff reduction by soil infiltration, constructing belt-type greenery was proposed. Although urban roadside soil is crucial part of urban green infrastructure, relatively few attention has been paid to assess overall soil quality in this systems. Only a few studies have assessed the quality of urban roadside soil especially focusing on the contamination by heavy metals. However, urban roadside soils have peculiar characteristics because they are severely degraded by narrow spaces, compaction, waste dumping, and erosion. In this study, we suggested an optimal set of soil variables that are representative of roadside soil properties and tree health. Seventy-three roadside soil were collected for measurement. Samples were used to measure both pre-suggested and new variables. The former included bulk density, penetration resistance (PR), pH, organic matter (OM), fluorescein diacetate (FDA) activity, and soil respiration (RES). New variables included the modified bulk density using PR, C/H ratio of particulate organic matter (POM-C/H) and stable nitrogen isotope ratio of POM (POM-δ15N). Two criteria were used to select the optimal set of variables: 1) the variable should identify distinct characteristics of roadside compared to urban forest soils, and 2) the variable should have a high correlation with urban tree health variables: leaf chlorophyll content and tree vigor. As a result, the modified bulk density (BDmodified) obtained from the soil PR was suggested to better represent soil compaction. The soil pH was a useful variable to represent unfavorable chemical conditions caused by de-icing materials, construction debris, and atmospheric alkali particles. The unexpectedly high OM contents in the roadside soils showed either insignificant or negative correlations with tree health variables. This implies that soil OM quality, not quantity, could be an important factor to influence tree health. The POM-C/H and POM-δ15N had significant correlations with tree health variables. The RES was significantly affected by soil compaction and low OM quality in urban roadside soils, and it had a significant positive correlation with tree health variables. Using multiple regression analysis, we suggested an optimal set of variables, BDmofieid, pH, POM-C/H, and RES, which were confirmed to be good predictors for tree growth in urban roadside greenery. In particular, the narrow space and excessive soil compaction are the major reason for degradation of urban roadside soil among all anthropogenic stresses. These stressful conditions can directly degrade soil structural qualities, eventually inhibiting plant growth under drought stress. Biochar application can improve soil structure and water retention, but the mechanisms for connecting changes in soil aggregation with those in pore size distribution and relating it to plant growth have not been fully understood. In this study, we investigated the role of biochar in improving soil structure and water retention under water-shortage stress in urban roadside greenery. In a field study, plots (2 m x 2 m) were established on roadside greenery in Suwon, Korea, in which 2.5% bochar by weight was mixed (BCfield). During the eight-month experiment, drought conditions prolonged, and soil water content was continuously higher in BCfield than in CONfield. For a more mechanistic understanding, a 100-day greenhouse experiment was conducted on seedlings of Rudbeckia hirta planted in sandy soil, mixed with 4% biochar by weight (BCgreenhouse). Drought conditions were simulated by maintaining the soil water content below 40% of the water-holding capacity. In the soil-aggregation process, the macro-aggregation (250-1000 μm) was enhanced after 60 days of biochar application, indicating that biochar acted as a binding agent for forming macro-aggregates. Enhanced macro-aggregation in biochar-added soil is, therefore, a possible mechanism for the increased formation of meso-pores. These pores could retain more soil water for plant uptake, eventually leading that plant biomass and water use efficiency in the BCgreenhouse were significantly increased by 39% compared to that in the CONgreenhouse under drought conditions. To determine the impacts of geological CO2 leakage on plant and soil processes, we conducted a greenhouse study in which plants and soils were exposed to high levels of soil CO2. Cabbage, which has been reported to be vulnerable to high soil CO2, was grown under BI (no injection), NI (99.99% N2 injection), and CI (99.99% CO2 injection). Mean soil CO2 concentration for CI was 66.8~76.9% and the mean O2 concentrations in NI and CI were 6.6~12.7%, which could be observed in the CO2 leaked soil from the pipelines connected to the CCS sites. The soil N2O emission was increased by 286% in the CI, where NO3--N concentration was 160% higher compared to that in the control. This indicates that higher N2O emission from CO2 leakage could be due to enhanced nitrification process. Higher NO3--N content in soil was related to inhibited plant metabolism. In the CI treatment, chlorophyll content decreased and chlorosis appeared after 8th day of injection. Due to the inhibited root growth, leaf water and nitrogen contents were consistently lowered by 15% under CI treatment. Our results imply that N2O emission could be increased by the secondary effects of CO2 leakage on plant metabolism. Another greenhouse study was conducted to suggest an effective indicator for leaked CO2 detection among the early-changed plant parameters. Corn (Zea mays), which was reported to be a tolerant species, was selected to identify early-changed and CO2-specific indicators of CO2 leakage, regardless of species. The mean soil CO2 concentration for CO2 treatment (CO2) was 20-40%, which could occur near transport pipelines through slow-insidious seepage. In CO2 treatment, the number of yellow leaves in the canopy level was significantly increased from the 6th day of injection compared to the control. The chlorophyll content in green leaf was significantly reduced at 8th day from CO2 injection. The soil water content in the CO2 treatment was increased from the 6th day of injection, which was due to reduced root adsorption. The results of this study implied that the early-changed parameters of CO2-tolerant species, such as canopy-level discoloration and chlorophyll content, could be utilized as CO2-specific and universal indicators for detection of soil CO2 leakage. In addition, rhizospheric-level parameters, such as soil water content, could be good subsidiary indicators together with massive baseline data and statistical analysis. In conclusion, we successfully suggested the methodologies and bio-indicators to assess and manage urban roadside tree-soil systems and CCS facilities. The novel methodology was developed to estimate the climate change adaptation benefits of roadside tree systems more extensively by considering building energy savings, pedestrians’ thermal-environment improvement, and surface runoff reduction. To assess soil quality in urban roadside systems, a new optimum set of soil variables was suggested that can better represent the unique characteristics of roadside soils exposed to excessive compaction and anthropogenic pollutants. As a soil amendment for urban roadside greenery, we identified how biochar improves the degraded soil quality and plant drought resilience by changing soil pore structure and soil water retention. To ensure CCS technological safety, we suggested that plant parameters, such as chlorophyll content and canopy-level discoloration, were useful bio-indicators for assessing and monitoring potential CO2 leakage in extensive CCS sites, such as CO2 transport pipelines. Besides, the rhizospheric changes by soil CO2 exposure, such as the increased soil N2O emission and water content, would be good subsidiary indicators for the impact assessment and detection of CO2 leakage. Therefore, this thesis will help establish and manage sustainable and safe strategies for climate change adaptation and mitigation.

국내 농경지 바이오차 투입에 따른 아산화질소 배출 : 밭토양을 중심으로

이용운 경희대학교 대학원 2017 국내석사

주요 온실가스 중 하나인 아산화질소(N2O) 배출은 국내에서 절반이상이 농업분야에서 발생한다. 이러한 농경지 아산화질소 배출을 저감시키기 위해 바이오차(Biochar) 투입 기술이 고려되고 있다. 바이오차는 산소를 제한한 상태에서 유기물을 열분해하여 만들어지는 물질로 토양에 투입되어 토양 탄소 저장 및 기후변화 완화 효과를 가지고 있다고 알려져 있다. 토양에서의 아산화질소 배출은 생물학적 질산화 및 탈질로 인해 발생하게 되는데, 바이오차를 토양에 투입하였을 경우 토양환경이 변화되어 아산화질소 배출이 변화될 수 있다. 본 연구의 목적은 국내 밭토양에 바이오차를 투입하였을 때 아산화질소 배출변화를 관찰하고 이에 영향을 주는 요인을 조사하며, 또한 아산화질소 배출의 대표기작을 알아보는 것이다. 실험은 국내 주요 작물인 고추와 배추를 대상으로 하였고, 온실 및 야외 실험지에서 바이오차를 투입하여 작물의 생장기간 동안 아산화질소 배출 변화를 측정하였다. 또한 아산화질소 배출변화의 주요 기작을 추가실험을 통해 밝히고, 토양 미생물 군집 변화를 파이로시퀀싱(Pyrosequencing)을 통해 알아보았다. 연구는 총 3회에 걸쳐 진행되었는데, 실험Ⅰ-고추밭(온실)과 실험Ⅱ-배추밭(야외) 연구를 진행하고, 바이오차 투입에 따른 아산화질소 배출 주요 기작을 알아보기 위해 실험Ⅲ-고추밭(야외) 연구를 진행하였다. 실험Ⅰ과 실험Ⅱ에서는 왕겨(rice husk) 바이오차 2 ton ha-1를 투입한 처리구를 아무것도 처리하지 않은 대조구와 비교하였다. 아산화질소 배출 기작을 알아보기 위해 바이오차와 질산화억제제(DCD, Dicyandiamide)를 요인 배치법(factorial design)으로 설계한 실험Ⅲ에서 아산화질소 배출량을 비교하였다. 연구 결과 아산화질소 누적 배출량은 대조구 대비 바이오차 처리구에서 실험Ⅰ에서는 9%, 실험Ⅱ에서는 74%, 실험Ⅲ에서는 51% 증가되었다. 실험Ⅲ에서 바이오차와 질산화억제제를 혼용 투입하였을 때 아산화질소 누적배출량이 바이오차만 처리한 처리구 대비 55% 감소하였다. 이는 본 연구지에서 아산화질소 배출의 주요기작이 질산화이고 바이오차 투입에 따라 아산화질소 배출이 증가된 원인이 질산화의 촉진임을 보여준다. 토양 미생물 군집분석 결과, 바이오차 투입에 따라 토양 미생물의 종 풍부도(Species richness)의 변화는 없었고 다양성지수(Diversity index)는 감소하였다. 속(Genus) 수준에서 질산화와 탈질 세균을 조사한 결과 바이오차 투입에 따라 독립영양 질산화세균과 탈질세균의 변화는 없었지만 종속영양 질산화 세균이 오히려 감소한 것으로 나타났다. 이는 바이오차 투입에 따른 미생물의 변화는 군집구조 자체보다는 특정 미생물의 활성이 변화될 수 있음을 시사한다. 또한 시험기간 중 토양수분함량이 매우 낮은 시점에서 바이오차 투입에 따른 아산화질소 배출의 큰 증가는 바이오차의 높은 수분보유능력에 의해 질산화세균의 활성도를 촉진시킨 것으로 사료된다. 본 연구 결과는 국내 밭토양과 같이 유기물 함량이 낮고 질소시비를 많이 하는 경우 가뭄으로 수분함량이 낮게 유지될 때 바이오차의 투입으로 인해 아산화질소 배출이 증가될 수 있기 때문에 바이오차 토양 투입 시 토양의 상태와 환경을 신중하게 고려하여 투입하여야 함을 보여준다. Nitrous oxide(N2O) is the one of the most important greenhouse gases. N2O emissions from agriculture contribute to more than half of the total amount of N2O emissions in Korea. Biochar application is considered as a useful technology to reduce N2O emissions. Biochar, which is a substance made by pyrolysis of organic matter, is introduced to soils to increase soil carbon storage and mitigate climate change. N2O is produced by biological nitrification and denitrification, both of which can be influenced by application of biochar into soil. In this study, the objectives are to investigate the changes of N2O emission by biochar application and to identify the factors affecting emissions when biochar is added into Korean agricultural soils. We selected two major Korean crops, red pepper and Chinese cabbages, and three separate experiments were conducted both in the greenhouse and field experimental site to measure N2O emissions during the growing seasons. Experiment I was conducted in the greenhouse red pepper field and Experiment Ⅱ was in the cabbage field site. In Experiment I and Experiment II, the treatments with 2 ton ha-1 of rice husk biochars were compared with the control without any additions. In addition, to understand the mechanism of increased N2O emission by biochar treatment, Experiment Ⅲ was conducted in the red pepper field by treating biochar and DCD(Dicyandiamide : nitrification inhibitor) with factorial design. Soil microbial community changes were investigated by pyrosequencing. The cumulative N2O emissions in the biochar treatment were increased by 9%, 74% and 51% in the experiment I, II and Ⅲ compared to the controls, respectively. In Experiment Ⅲ, cumulative N2O emissions were decreased by 55% in the biochar treatment relative to biochar mixed with DCD treatment. This indicated that N2O emission was increased by biochar addition and that nitrification is the main process for N2O production in our sites. Analysis in soil microbial communities showed that there was no change in species richness(Ace, Chao1) of soil microorganisms by biochar treatment, however, diversity index(Shannon, Simpson) was decreased by biochar addition. At the genus level, there was no change in autotrophic nitrifying bacteria and denitrifying bacteria by biochar application, while the abundance of heterotrophic nitrifying bacteria was significantly decreased. It suggested that biochar addition might alter the activity of specific microorganisms while it might not change the overall microbial community structure. In addition, biochar amendment might have improved dry soil condition, which, in turn, promoted activities of nitrifying bacteria, resulting in higher N2O emission. Overall results suggested that in a soil with low organic matter and high mineral nitrogen fertilizer, N2O emission from soils may be increased due to biochar input when the soil water content is maintained very low. Care should be taken when biochar is amended in this situation.

지표면 특성과 미기상 조건이 미세먼지의 비산 및 재비산에 미치는 영향 연구

서인혜 경희대학교 대학원 2022 국내석사

Atmospheric particulate matter(PM) is blocked or attached to or absorbed by leaves and bark while passing through the vegetation barrier. As all these mechanisms do not lead to permanent removal, PM deposits ground surface and it may re-entrainment to the air flow. In this study, a wind tunnel system and a closed chamber system were designed respectively to quantify PM resuspension from several surface types in different environmental conditions. Each experimental group was categorized into various factors such as wind speed, relative humidity, surface roughness, and presence of litter layer. Resuspension PM was measured using EDM164, a light scattering PM detector. PM resuspension varied depending on the surface type and wind speed, and the resuspension quantified in the semi-open wind tunnel was lower than that quantified in the closed chamber. Improvement of the experimental methodology can lead to multidisciplinary development between atmospheric-soil studies in the future.

바이오차 투입을 통한 가로수 토양의 물환경 개선 연구

유신이 경희대학교 대학원 2019 국내석사

도시 가로수는 도시 미관향상, 기후조절, 대기오염물질 정화기능 뿐 아니라 단절된 도시 녹지네트워크를 연결하는 축으로서 중요한 역할을 하고 있다. 그러나 이들의 생육환경은 인간과 건물에 의한 토양압밀로 통기성 및 투수성이 불량하고 극심한 기후변화로 인한 강수변동 스트레스를 동시에 겪고 있다. 바이오차는 산소가 제한된 환경에서 바이오매스를 열분해하여 생성되는 물질로 토양에 투입할 경우 토양압밀 완화, 수분 및 양분 보유 증대 등의 토양개량효과가 있다. 이에 본 연구에서는 기후변화로 수분 스트레스를 겪고 있는 가로수 토양 내 바이오차 투입을 통한 토양환경의 변화를 분석하고 변화된 토양환경에 대한 식물의 반응을 살펴보았다. 연구는 총 2회에 걸쳐 진행하였는데, 실험Ⅰ은 온실규모에서 홍수 및 가뭄의 수분변동을 고려한 가로수 모사실험을 진행하였고 실제 가로수 토양환경 개선에도 적용가능한지 확인하기 위해 실험Ⅱ를 야외에서 진행하였다. 실험Ⅰ은 과도한 물조건과 일정시점 이후 물공급을 중단하여 수분상태가 변화하는 두 조건에서 은행나무 2년생을 대상으로 130일간 진행하였으며 사양토에 바이오차를 2.5%(w/w)를 투입한 처리구와 아무것도 투입하지 않은 대조구를 비교하였다. 실험Ⅱ는 수원시 느티나무 가로수의 토양을 대상으로 3달간 진행하였으며 왕겨 바이오차와 왕겨를 각각 토양에 2%(w/w) 투입한 처리구와 아무것도 투입하지 않은 대조구를 비교하였다. 배양 후 토양의 구조적, 화학적, 생물학적 변화와 식물의 바이오매스, 엽록소 및 잎수분함량을 분석하였다. 실험Ⅰ 결과, 과도한 물조건에서 바이오차 처리구는 배양기간동안 토양수분함량이 LLWR(least limiting water range)를 벗어나는 일수가 평균 10일인데 반해 대조구는 평균 117일로 과도한 수분에 대한 스트레스를 받음을 확인하였다. 이는 바이오차 투입에 따른 입단분포변화와 관련된다. 바이오차 투입으로 토양 내 거대입단(250-1000um,>1000um)과 대공극이 형성되고 바이오차 자체가 거대입단처럼 작용하여 토양 공극 분포에 영향을 준 것으로 보인다. 물공급의 중단으로 토양이 건조되는 환경에서 대조구는 입단분포 변화가 나타났지만 바이오차 처리구에서는 입단분포 변화가 관찰되지 않았다. 이는 토양 내 바이오차 투입이 수량변동에 저항성 높은 토양구조를 만들었음을 보여준다. 이러한 토양구조는 식물과 미생물이 이용가능한 양분보유에도 영향을 미쳐 바이오차 처리구에서 높은 미생물 활성과 식물생장으로 보였다. 실험Ⅱ 결과, 폭우로 발생되는 토양압밀에 대해 왕겨 바이오차 및 왕겨 처리구에서 대조구에 비해 각각 70%, 96% 높은 토양압밀 저항성을 보였다. 이는 투입물질의 투입을 통해 토양압밀 저항성이 높아졌음을 의미한다. 또한 폭우기간 1일 전후 동안의 수분변화량을 통한 토양의 폭우완충정도를 비교해보면, 왕겨 바이오차 처리구가 0.05%로 0.09%인 대조구, 0.08%인 왕겨 처리구에 비해 급변하는 수량변동에 대한 영향을 덜 받음을 확인하였다. 이러한 결과는 앞선 실험Ⅰ의 결과처럼, 바이오차 투입으로 형성되는 거대입단 또는 거대입단(250-1000um,>1000um)과 비슷한 크기의 입자들로 구성된 바이오차 자체가 거대입단처럼 작용하였기 때문으로 사료된다. 변화된 토양환경에 대한 가로수의 반응은 관찰되지 않았는 데, 투입물질-토양-미생물-식물 간의 상호작용이 이루어지는 데 긴 시간이 필요하기 때문으로 판단된다. 본 연구에서는 바이오차를 토양에 투입할 경우 토양환경이 개선되어 식물 및 미생물이 성장하기에 더 나은 환경을 제공해줄 뿐 아니라 안정된 토양구조로 극심한 기후변화로 발생되는 외부 변화에 대해 토양이 받는 스트레스를 감소시킨다는 것을 알 수 있었다. 그러나 바이오차가 투입되어 토양, 미생물, 식물과 상호작용을 하는 데 시간이 필요하므로 장기적인 관점에서 꾸준한 모니터링이 요구되며 시간이 흐름에 따라 추가적으로 발생되는 바이오차의 토양개량효과도 기대해 볼 수 있다. Urban roadside tree plays an important role not only in enhancing urban aesthetics, climate regulation and purification of air pollutant, but also connecting the scattered urban greens. However, their growth environment is influenced by soil compaction and fluctuating stress of precipitation due to extreme climate change. Biochar, a substance produced by pyrolysis of biomass, which is regarded as a useful soil amendment to enhance soil structural quality and increase plant growth. Two experiments were conducted to investigate the effect of biochar on urban roadside tree soil subjected to severe water status changes due to climate change and to identify the response of plants with biochar addition. The ExperimentⅠwas simulated the common urban roadside tree system considering the water conditions of flood and drought, so we conducted with different extreme water conditions of the excessive and switching water conditions. The 2-year-old Ginkgo trees (Ginkgo biolba) were selected and planted in the soil with biochar addition at application rate of 2.5% (w/w) (BC) in greenhouse for 130 days. ExperimentⅡwas conducted in the urban roadside tree system in Suwon to determine whether biochar application could improve the soil quality in the field for 3 months. In this experiment, the species of urban tree is Zelkova trees (Zelkova serrata) and we applied soil with 2% (w/w) of rice husk biochar (RH_CHAR) and rice husk biomass (RH_RAW), respectively. After the incubation of two experiments, we analyzed soil physicochemical and biological properties, plant biomass, chlorophyll content, and leaf water content. In ExperimentⅠ, the time of soil water content was out of the LLWR (Least limiting water range) in BC soil was only for 10 days, but the time in the CON soil was 117 days during the incubation with the excessive water conditions. This indicated that the CON soil was influenced with flooding stress due to a low hydraulic conductivity which was changed in distribution of soil aggregates by biochar additions. Biochar addition could enhance the formation of soil macroaggregates (250-1000um, > 1000um) and biochar itself could play as macroaggregates resulting in changes of pore size distribution. Also, the resilience of soil structure to switch water conditions in the BC soil was increased. Higher resilience could enhance the nutrient retention which led to high microbial activity and plant growth. In Experiment Ⅱ, compared to CON, RH_CHAR and RH_RAW showed higher resistance of soil compaction by 70% and 96%, respectively. This implied that addition of rice husk biochar and rice husk biomass improved the resistance of soil compaction. In addition, about the changes of amount for soil water content before and after rainfall, CON, RH_RAW and RH_CHAR were 0.09%, 0.08% and 0.05% respectively. Biochar amendment could increase the degree of buffering of rainfall. This result was probably due to the formation of macroaggregates with biochar addition or biochar itself which could act as macroaggregates. However, no response of urban roadside trees was observed for the changed soil environment with biochar and biomass addition. We can assume that making the interaction of added material-soil-microorganisms-plant would take a long time. Overall our study indicated that biochar amendment to soil could improve soil environment which is beneficial for plants and microorganisms. Biochar addition decreased the soil stress for extreme water changes due to climate change by having stable soil structure. However, it takes a long time to form an interaction of biochar with soil, microorganisms, and plants. The continuous monitoring is also required for the long-term experiment to investigate the effects of biochar addition on soil improvement over time.

도시 가로수 공간의 탄소 흡수량 산정 : 수원시 가로수 대표 관목을 대상으로

정민섭 경희대학교 대학원 2023 국내석사

가로수의 탄소 흡수는 도시 녹지의 중요한 기능이다. 가로수는 일반적으로 교목과 많은 개체수의 관목을 조합하여 식재되지만, 관목의 탄소 흡수는 많은 연구에서 무시되어 왔다. 따라서, 본 연구는 적외선 가스 분석기(IRGA)를 이용하여 가로수 현장 관목의 탄소 흡수량을 정량화하고, 온실에서 배양 실험과 직접수확법을 수행하였다. 가로수 현장에서는 관목의 광합성과 기온, 광량(PAR)을 측정하였다. 온실에서는 2020년부터 2022년까지 매년 관목을 수확하여 순일차 생산량(NPP)을 계산하였다. 사철나무(Euonymus japonicus)의 연간 NPP는 0.036 kg C/tree/yr로 확인되었고, 교목과 관목이 있는 8m 도로변 구간의 NPP는 10.884 kg C/yr에 해당한다. 이 수치는 관목이 없는 구간의 NPP인 8.040 kg C/yr에 비해 약 35.4% 높았다. 따라서 본 연구에서는 가로수 관목에 대한 탄소 데이터를 확보하였으며, 관목의 다층식재의 중요성을 강조함으로써 관목의 연구 필요성을 확인하였다. Carbon uptake of roadside trees is an important function of urban greenery. Roadside trees are usually combined with a large number of shrubs, but shrubs are neglected in various studies of carbon uptake. Therefore, I quantified the carbon uptake of shrubs using an infrared gas analyzer(IRGA) on the roadside and harvesting method with a greenhouse incubation. On the roadside, I measured the photosynthesis of shrubs, air temperature, and photosynthetically active radiation(PAR). In the greenhouse, shrubs were harvested yearly from 2020 to 2022 to calculate the net primary production(NPP). The annual NPP of Euonymus japonicus was 0.036 kg C/tree/yr, and the NPP of the 8m roadside section with a tree and shrubs was 10.884 kg C/yr. It was about 35.4% higher than the NPP of the section without shrubs. This study obtained the carbon data on roadside shrubs and emphasized the importance of multi-layered planting.

농경지의 아산화질소 배출 저감 연구 : 가축분뇨 투입에 따른 배출 특성 파악 및 바이오차를 활용한 저감 기작 연구

현준기 경희대학교 대학원 2019 국내석사

As N2O is a major greenhouse gas and known to deplete stratospheric ozone, it is important to estimate total emission by different sources and develop appropriate technologies to reduce its emission. It was reported that 40% of total anthropogenic N2O emission is from the cultivation sector, indicating that the efforts to reduce N2O emission from the agricultural soils is urgently needed. In this study, we conducted the field and laboratory experiments to investigate characteristics of N2O emission patterns by manure application and to understand emission reduction mechanism of N2O by biochar application to the soil. The field experiment was conducted for 3 years from 2016 to 2018 in the central zone of Korea (Chungcheongnam-do agricultural research & extension). The experiment was carried out with control, chemical fertilizer treatment and chemical fertilizer with pig, cow and chicken manure treatments at 10, 20, 30ton ha-1 rate, respectively. Emission factor (EF) on the average of 3years for chemical fertilizer was 0.0120 kg N2O-N (kg N)-1, which is similar to that of default emission factor of IPCC guideline. On the other hand, the EFs of pig, cow and chicken manures were 0.0020 kg N2O-N (kg N)-1, 0.0075 kg N2O-N (kg N)-1, 0.0062 kg N2O-N (kg N)-1, respectively, which were 16, 60 and 50% of the default values of IPCC guidelines. Developed EFs in this study could be regarded as the representative emission factors in the Central Korea zone as we strictly followed the IPCC guidelines. Our EFs, together with those developed in Southern and Western Korean zones, are expected to improve the accuracy of N2O national inventory from the cultivation sector. In addition, total cumulative N2O emissions showed high annual variability among different manure treatments and the magnitude of variance was up to 600%. We found that the nitrogen content of the manure and the soil water content during the first month after the manure application were the main factor to control the total amount of annual N2O emissions. Biochar application was suggested as a new management practice to reduce N2O emission in upland agricultural fields. However, the effects of biochar on N2O emission showed inconsistent trends depending on biochar types and soil conditions. To understand this inconsistency, we need to understand mechanisms of microbial soil N transformations related to N2O emission. We hypothesized that biochar with high labile matter could increase N2O emission from dry and infertile upland soils with heavy N fertilization. To test our hypothesis, two sets of incubation experiments were conducted. The first set of experiment aimed at investigating the effect of biochar amendments with different labile matters on N2O emission and NO2- accumulation, which known to be directly associated with N2O emission increase in the excessive nitrogen fertilized soil. In the second set of experiment, we tried to find the condition where the biochar with high labile matter can be utilized without increasing N2O emission. The experiment I was carried out using the C limited soil with 300mg N kg-1 fertilization amended with 4% (w/w) biochars, varying with HWC content (Hot Water extractable carbon, wood pellet biochar: 635.13 mg kg-1; cocopeat biochar: 4413.70 mg kg-1; rice husk biochar: 6943.80 mg kg-1). As a result, N2O emission rates were increased in the high labile biochar treatments, which supported our hypothesis. We speculated that increased urease activity and microbial respiration by labile matter of biochar resulted in NH3 increase and NO2- accumulation, leading to higher N2O emission. This is because in the process of nitrification (NH4+→ NO2- → NO3-), when NH3 contents are high, NO2- tends to be accumulated due to NOB (nitrite oxidizing bacteria) is more sensitively inhibited to NH3 toxicity than AOB (ammonia oxidizing bacteria). However, the gene abundance of AOB and NOB did not change by biochar application and it is assumed that the experiment period was too short to observe changes of gene abundance and/or the inhibitory effect of NH3 to NOB was temporary. Our results showed that when labile biochar is added to C limited soil with excessive N condition, more N2O is produced via NO2- accumulation. The experiment II was followed using the same soil amended with rice husk biochar only, which showed an increase in N2O emission upon biochar addition from the experiment I. On the other hand, we changed the N fertilization rate into half (150mg N kg-1) and a set of lime application (0.5% CaCO3) was added to find a condition where the biochar with high labile matter can be utilized without increasing N2O emission. In contrast to experiment I, N2O emission was not increased by rice husk biochar and it was rather decreased when biochar was added with CaCO3. While urease activity and microbial respiration were increased by biochar addition as same as experiment I. It was speculated that NH3 concentration was also increased rapidly by biochar addition. However, NO2- concentration and N2O emission were maintained/reduced in the biochar treatments and this results implies that the inhibition of NOB by increased NH3 was minimal. We attributed this to adsorption of NH4+ by biochar, which was not observed in excessive N condition. Overall results indicate that application of biochar with high HWC content to the carbon limited agricultural field with excessive N fertilization may lead to additional N2O emission and it is necessary to manage the N application rate in order to reduce N2O emission. In addition, when lime and biochar are simultaneously amended to the moderately fertilized soils, it would be an effective strategy to reduce N2O emission. 아산화질소 (N2O)는 주요한 온실가스이며 오존층을 파괴하기 때문에, 이의 배출원과 배출량을 정확히 파악하고 그에 맞는 저감 기술을 도입할 필요가 있다. 에너지, 산업 공정, 축산, 경종 등 다양한 아산화질소 배출원 중 경종 부문에서의 배출량이 총 인위적 배출량의 40%에 달하기 때문에, 작물재배 과정에서 배출되는 아산화질소의 감축 노력이 시급한 실정이다. 이에 본 연구는 국내 농경지에서 가축 종류별 퇴비 투입에 따른 아산화질소 배출 특성을 파악하고, 아산화질소 저감 방안을 제안하기 위하여 야외 실험과 실내 배양 실험을 각각 수행하였다. 야외 실험은 2016년부터 2018년까지 3년간 충청남도 농업기술원 내 밭에서 수행되었다. 아무런 처리도 하지 않은 무처리구와 화학 비료를 투입한 NPK처리구, 화학 비료를 처리하고 돈분, 우분, 계분을 각각 10, 20, 30 ton ha-1만큼 투입한 처리구로 수행되었으며, 화학 비료, 돈분, 우분, 계분에 대한 아산화질소 배출계수를 산정하였다. 화학 비료의 3년 평균 배출계수는 0.0120 kg N2O-N (kg N)-1 로 IPCC 가이드라인의 기본 계수와 유사한 수준인 반면, 돈분은 0.0020 kg N2O-N (kg N)-1, 우분은 0.0075 kg N2O-N (kg N)-1, 계분은 0.0062 kg N2O-N (kg N)-1로 IPCC 가이드라인 가축분뇨 기본 계수의 16, 60, 50% 수준이었다. 본 연구에서 개발된 배출계수와 함께 호남, 경남 지역에서 개발된 배출계수의 평균치를 온실가스 인벤토리에 적용함으로써 농경지 가축분뇨 시용에 의한 배출량 산정의 정확도를 개선할 수 있을 것으로 기대된다. 또한 연간 총 누적 아산화질소 배출량은 가축분의 종류 및 연도에 따라 최대 6배 가량의 차이를 보였는데, 가축분의 질소 함량과 더불어 가축분 투입 후 초기 한 달 동안의 토양 수분 함량이 이러한 변동을 결정하는 주요 요인임을 파악하였다. 야외 실험을 통해 아산화질소 배출 특성을 파악할 수 있었으며, 이를 기반으로 국내 농경 토양에 적합한 아산화질소 배출 저감 기술 도입을 위한 배양 실험을 수행하였다. 바이오차는 이를 농경 토양에 투입함으로써 탄소를 장기적으로 저장할 수 있는 기후변화 완화 대책으로 주목받고 있다. 또한 바이오차의 농경 토양 투입은 토양의 건강성을 회복시키고, 아산화질소의 배출을 저감할 수 있는 추가적인 효능을 가지고 있기 때문에 척박한 국내 농경지 토양에 적합한 아산화질소 배출 저감 기술로 판단된다. 하지만 일부 바이오차 투입으로 인해 아산화질소의 배출량이 증가 또는 영향을 받지 않는 사례들이 보고되고 있기 때문에, 실제 농경지에 적용하기에 앞서 실내 실험을 통해 바이오차의 밭 토양 투입에 따른 아산화질소 배출량 변화를 관찰하고 그 원인을 파악하고자 하였다. 배양실험 I은 바이오차 토양 투입에 따른 아산화질소 배출량 변화가 바이오차가 함유하고 있는 가용한 탄소함량 (HWC; Hot Water extractable Carbon)과 연관이 있다고 보고, HWC 함량이 상이한 세 종류의 바이오차 (WO_600, CO_400, RH_400)를 가지고 수행되었다. 모든 대조구와 바이오차 처리구에는 300 mg N kg-1의 과도한 질소 시비가 이루어졌으며, 산소 공급이 원활한 조건에서 15일간 배양되었다. 실험 결과 HWC 함량이 높을수록 대조구 대비 아산화질소의 배출량이 증가하는 것을 볼 수 있었으며, HWC 함량이 낮은 WO_600 바이오차의 경우 대조구와 차이가 없었다. 아산화질소 배출량이 높게 나타난 RH_400 과 CO_400 처리구에서 전반적인 미생물 활성도가 증가되었을 뿐만 아니라 요소 분해 효소의 활성도도 높게 관찰되었는데, 이로 인해 요소 투입 직후 토양 내 NH4+/NH3이 과량 존재할 것으로 사료된다. 토양 내 고농도 암모니아가 존재하면 아질산이 축적되는 것으로 알려져 있는데 이는 아질산 산화균이 암모니아 산화균에 비하여 고농도 암모니아에 대한 독성에 민감하게 저해되어 나타나는 현상으로 보고되고 있다. 본 실험 결과 CO_400 과 RH_400 처리구에서 배양 4일차에 아질산 이온의 축적을 관찰할 수 있었으며, 축적된 아질산이 질산화 미생물의 탈질 과정 등에 의해 아산화질소로 배출되어 대조구와 WO_600 처리구 대비 아산화질소 배출량이 높은 것으로 사료된다. 하지만 암모늄/아질산 산화균의 종풍부도는 처리구 간 차이가 없었는데, 이는 AOB와 NOB의 DNA 풍부도의 변화를 관찰하기에는 실험 기간이 다소 짧았거나, 암모니아에 의한 NOB의 저해가 일시적인 현상이기 때문에 나타난 결과로 사료된다. 배양 실험 II는 아산화질소 배출 증가가 가장 컸던 RH_400 바이오차만으로 수행되었으며, HWC 함량이 높은 바이오차를 활용하기에 적합한 농경지 관리 방안을 찾고자 질소시비량을 150 mg N kg-1으로 줄이고 석회 시용 (0.5% CaCO3)을 한 세트를 추가하였다. 배양 실험 I과는 상이하게도, RH_400 처리구에서 아산화질소 배출이 증가되지 않았으며, 석회 시용 처리구에서는 오히려 배출이 감소되었다. 하지만 배양실험 I과 동일하게 RH_400 바이오차 처리구에서 높은 미생물 활성을 보였으며, 각 처리구 별 아산화질소 배출량과 아질산 이온의 농도가 높은 상관관계를 보였다. 이는 질소 시비량이 절반으로 줄은 경우 바이오차의 HWC가 전반적 미생물 활성도와 요소분해효소 활성도를 증가시켰음에도 불구하고, 이 때의 증가된 토양 암모니아는 바이오차의 높은 CEC로 인한 암모늄 흡착에 의해 조절되어 암모늄/아질산 산화 과정의 불균형을 초래하지 않은 것으로 사료된다. 배양 실험 I에서는 바이오차의 흡착에 의한 영향이 나타나기에 과도한 수준의 질소 시비가 이루어진 것으로 판단된다. 한편, 석회를 시용한 처리구들은 질소 시비량이 줄은 경우라도 석회가 함께 투입되어 토양 내 pH가 증가되었기 때문에 암모니아 농도가 상대적으로 높아 아질산 산화균에게 선택적 독성을 보일 수 있는 조건이지만, 바이오차 처리구에서 오히려 아질산 이온 감소 및 아산화질소 배출의 감소가 나타났다. pH가 증가함에 따라 바이오차의 양이온 교환능 역시 증가하는 선행 연구들을 고려했을 때 높은 pH로 인해 바이오차의 암모늄 흡착능이 증가하여 오히려 아질산 이온의 농도와 아산화질소 배출량이 감소한 것으로 사료된다. 두 번의 배양 실험은 과도한 질소 시비가 이루어지는 척박한 국내 농경 토양에 HWC 함량이 높은 바이오차를 투입하는 것은 추가적인 아산화질소 발생을 가져올 수 있으며, 이를 저감하기 위해서는 적정 시비량에 맞추어 질소원을 관리할 필요가 있음을 시사한다. 또한 토양 산성화 관리를 위해 석회를 시용 하는 경우 바이오차와 혼용하면 오히려 아산화질소 발생을 저감시킬 수 있는 효과적인 관리방안이 될 수 있을 것이다.

바이오차르 토양 투입 관리 방안의 타당성 평가 ? 농경 활용을 중심으로

김예솔 경희대학교 2014 국내석사

Biochar is defined as pyrolyzed biomass which is intended to be applied into the soil. As biochar contains high contents of stable carbon, its application to agricultural soils can increase soil carbon sequestration. In addition, biochar amendment is also known to improve soil fertility and crop production. However, these benefits are sometimes under debate because production process of biochar requires additional energy and extra greenhouse gases might be emitted during the application process. Hence, overall impacts of biochar utilizing system should be assessed for the entire stages from production to application of biochar. In this study, the feasibility of biochar utilization was evaluated for domestic agricultural system by considering both greenhouse gas emissions and energy balance. Accounting for 10% of crop residues in Korea, the rice hull was selected for feedstock of biochar and the rice hull biochar was assumed to be applied to loamy sand rice paddy soil and Saemangeum reclaimed land soil. We used scenario approach by examining biochar utilization systems in three different scenarios depending on the scale of biomass pyrolysis facility (CHAR_RH small, intermediate, and large). As control scenarios, systems with rice hull biomass application (BIO_RH scenario) and no soil amendment (NO_AMD scenario) were also examined. In every scenario, soil amendments were applied at 2% (w/w) concentration. Three different stages were considered for the overall feasibility assessment and greenhouse gas emissions and energy balance were calculated in each stage. At the first stage, data on the biochar production process were obtained from running the BEAT2 software from UK DEFRA. The second stage was related to biochar application process and soil cultivation. Data were collected from the published reports by the government for the domestic agricultural greenhouse gas emissions and energy consumption. The last stage considered the effects of biochar application to soil and lab-scale experiment was conducted to produce data for this stage. Data were uniformly converted to ton CO2 eq. ha-1 yr-1 for greenhouse gas emissions and MWh ha-1 for energy balance, respectively. Results showed that greenhouse gas emissions from the CHAR_RH scenarios were -42.09 ~ -21.46 ton CO2 eq. ha-1 yr-1 while those from the BIO_RH and NO_AMD scenarios were +14.00 ~ +19.59 ton CO2 eq. ha-1 yr-1. This indicated that there was no additional emissions of greenhouse gases from the systems on the CHAR_RH scenarios regardless of biochar production scale. The energy balance was estimated as -8.42 ~ +49.39 MWh ha-1 depending on the scenarios. Energy balance was positive for the CHAR_RH intermediate and large scenarios, meaning that the systems are producing the additional energy. Considering both greenhouse gas emissions and energy balance, biochar utilization system was feasible at the CHAR_RH intermediate and large scenarios. In The CHAR_RH small scenario, more energy is needed to sustain the system because the efficiency of biochar producing facility was low. Consequently, the feasibility of biochar application to the domestic agricultural system was dependent on the efficiency of the biochar producing facility. Therefore, improvement in efficiency of pyrolysis technology should be accompanied to ensure the benefit of utilizing biochar. 바이오차르란 폐 바이오매스를 열분해하여 얻는 탄화물로, 이를 토양에 투입하면 원료 물질의 탄소를 고농도로 안정하게 격리할 수 있어 기후변화 완화 잠재력을 기대할 수 있다. 또한 유기물이 매우 적고 양이온 교환능력이 낮아 생산성이 떨어지는 간척지와 같은 척박한 토양에 투입되었을 때 토양의 비옥도와 양분 이용 효율을 증대시키는 등의 토양 개량 효과가 있다고 보고되고 있다. 하지만 일각에서는 바이오차르의 생산에 따른 에너지의 소모 및 온실가스 배출과 바이오차르의 활용에 의한 편익 간의 수지에 대한 쟁점이 제기되고 있다. 따라서 바이오차르 토양 투입 방안을 국내에 도입하기 위해서는 바이오차르 활용 시스템의 타당성 검증이 필수적으로 선행되어야 한다. 따라서 본 연구에서는 국내 실정을 고려한 바이오차르 농경 활용 시스템을 가정하여 시스템 전단계의 온실가스 배출 수지 및 에너지 수지를 분석함으로써 바이오차르 활용의 타당성을 평가하였다. 먼저 연구 재료로 국내 주요 농업 부산물인 왕겨 바이오매스로 생산한 왕겨 바이오차르를 선정하였으며 이를 양질사토의 논 토양과 새만금 간척지 토양에 각각 투입하는 시나리오를 가정하였다(CHAR_RH 시나리오). CHAR_RH시나리오는 바이오차르 생산 시설의 규모에 따라 소규모, 중간규모, 대규모로 세분화하였다. 또한 비교를 위해 토양 개량제의 투입이 없는 무투입 시나리오와 왕겨 바이오매스를 토양 개량제로서 투입한 BIO_RH 시나리오를 설정하였다. 모든 시나리오는 토양 1 ha를 기준으로 무게기준 2%의 토양 개량제를 투입하는 시스템을 가정하였다. 바이오차르 활용 시스템의 타당성 평가를 위한 자료 수집은 크게 세 단계로 구분하여 실시하였는데, 첫 번째 단계인 바이오차르 생산 단계는 바이오에너지 발전시설 평가 소프트웨어인 BEAT2를 구동하여 정보를 수집하였다. 두번째 바이오차르 토양 투입 및 경작 단계에서는 농촌진흥청 연구 보고서, 국내 농업부문 온실가스 배출량 연구 자료 등을 통해 관련 정보를 수집하였고 마지막으로 바이오차르의 토양 투입에 따른 효과의 연구 자료는 실험실 규모에서 실시한 실험 결과를 바탕으로 정리하였다. 수집한 자료는 온실가스 배출 수지와 에너지 수지로 구분하여 각각 ton CO2 eq. ha-1 yr-1 및 MWh ha-1 단위를 기준으로 변환하였다. 그 결과 온실가스 배출 수지는 시스템에 따라 -42.09 ~ +19.59 ton CO2 eq. ha-1 yr-1로 계산되었는데 무투입 시나리오와 BIO_RH 시나리오는 모두 시스템의 온실가스 배출 수지가 양의 값을 보인 반면 CHAR_RH 시나리오는 규모와 무관하게 음의 값으로 시스템에서 온실가스가 저장되어 추가로 배출되지 않는 것으로 나타났다. 에너지 수지는 시스템에 따라 -8.42 ~ +49.39 MWh ha-1로 계산되었는데 CHAR_RH 중간규모 및 대규모를 제외한 나머지 시나리오에서는 에너지 수지가 음의 값으로 시스템에 에너지가 투입되는 것으로 나타났다. 따라서 온실가스 배출 수지와 에너지 수지를 동시에 고려하면 CHAR_RH 시나리오에서만 바이오차르 활용이 타당한 것으로 평가되었으며, CHAR_RH 소규모 시나리오에서는 바이오차르 생산 시설의 발전 효율이 낮기 때문에 시스템에 에너지가 추가로 투입되어야 하는 것으로 평가되었다. 결과적으로 국내 바이오차르 농경 활용의 타당성은 바이오차르 생산 시설의 규모에 따른 효율성에 의해 결정되었다. 따라서 바이오차르 활용에 따른 편익이 보장되기 위해선 국내 바이오차르 열분해 기술의 개발을 통한 효율 개선이 동반되어야 하는 것으로 분석되었다.

Effects of different biochar amendments on carbon loss and leachate characterization from an agricultural soil

YANG XINGYA Kyung Hee University 2018 국내석사

Application of biochar to soils was suggested as a strategy to increase carbon (C) sequestration and improve soil quality, but its impact on C leaching loss and leachate chemistry has received little research attention. A lab lysimeter study was conducted to compare the effects of application of four types biochar on C balance and leachate quality. Biochars made from sewage sludge and wood pellets produced at 400℃ (SS400 and WP400) and 700℃ (SS700 and WP700) were applied to 300 g of agricultural soil (Silt loam) at 4% application rate, non-amended soil was used as the control. During the 35 days of incubation, 150 ml of distilled water was applied to each lysimeter for five times with a 7 day interval. Results showed the proportion of total C loss to total C content of each treatment was decreased in all biochar treatments (SS400, SS700, WP400, WP700) by 68.7%, 45.8%, 69.6%, 73.8% respectively, compared to control (4.3%). Biochar treatments also reduced the proportion of C leaching loss, especially WP400 and WP700 treatment by 65.3% and 64.8% respectively, compared to the control (0.3%). Biochar applications not only affected the quantity of leaching C but also the leachate quality. Only in the SS700 treatment, concentrations of COD, TN and DOC were significantly decreased compared to other treatments and the control. Fluorescence analysis of the DOC revealed that the SS700 treatment attenuated the intensity of the peak related to humic-like substances, which might be related to higher adsorptive capacity of SS700 biochar. On the other hand, DOC in the leachate from the SS400 treatment had higher component of humic-like substance and a new peak appeared which was originatd from the biochar itself. Over all, our findings indicated that wood pellet biochars greatly reduced the total C loss compared to the sewage sludge biochars. And sewage sludge biochar (700℃) amendment could markedly reduced C and N leaching from soil, it may be possible to improve both C sequestration and nutrient retention by pyrolyzing sewage sludge at higher temperatures. The effects of biochar varied with different feedstocks and different pyrolysis temperatures.

공간규모의 특성을 고려한 기후변화 취약성 평가와 적응정책 연계를 위한 방법론 연구

김아라 경희대학교 2014 국내석사

기후변화 취약성 평가는 기후변화 적응정책을 수립하는 데 중요한 역할을 하므로 기후변화 취약성을 올바르게 평가하는 것이 중요하다. 그 동안의 평가는 생물⋅물리적인 측면과 사회경제적인 측면을 동시에 갖고 있는 기후변화 취약성의 복잡한 개념 때문에 정보를 종합하는 데 용이한 복합지수를 이용하여 평가해왔다. 기존 기후변화 취약성 지표를 구성하는 대리변수들은 논리적 적합성과 자료의 가용성에 근거하여 주로 통계자료들 중에 선정되었는데, 이를 선정하는 기준이 다소 주관적이었다. 또한 중복된 지표가 포함되는 경우가 많았기 때문에 지표들 사이에 다중공선성이 존재하여, 특정 부문이 의도치 않게 가중화되는 경향이 있었다. 뿐만 아니라 기후변화 취약성을 구성하는 요소인 기후노출의 본질적인 규모와 민감도, 그리고 적응능력의 평가 및 관리 규모를 고려하여야 함에도 불구하고, 이를 고려하지 않고 유사한 구성의 지표를 사용하여 기후변화 취약성을 평가했다는 한계점이 있었다. 따라서 본 연구에서는 다변량 분석 기법인 주성분 분석과 군집 분석을 통해 국가 자료세트(국가규모)와 지자체 자료세트(지자체규모)로부터 기후변화 취약성의 핵심지표를 추출하여 복합지수의 한계점을 극복하고자 했다. 그 결과, 국가 자료세트에서는 여러 국제기구에서 기후변화 취약성 지표로 널리 사용되는 총 33개의 대리변수 중 GINI Index, 인구밀도, 기대여명 등 18개의 대리변수가 추출되었다. 지자체 자료세트에서는 국내 여러 연구기관에서 기후변화 취약성의 지표로 많이 사용되는 총 34개의 대리변수 중 GRDP, 재정자립도, 인구밀도 등 10개의 대리변수가 주요 인자로 파악되었다. 나아가 본 연구에서는 인도네시아 자카르타를 대상으로 취약성 평가를 수행하였다. 이를 통해 지리정보시스템(GIS)과 토지이용도 등이 평가 대상인 공간의 상황과 특성을 반영하는 지표 선정에 활용될 수 있으며, 이러한 지표를 기반으로 진행된 취약성 평가의 결과가 적응정책에 연계될 수 있는 방법론을 제안하였다. 본 연구는 기후변화 취약성을 구성하는 주요 인자 중 공간규모에 무관하게 유지되는 것도 있지만, 공간규모의 특성을 반영하는 주요한 핵심 지표가 있다는 것을 통계적으로 보여줌으로써 지역의 맥락화(contextualization)의 중요성을 강조한다는 데에 의의가 있다. ` Assessment of climate change vulnerability plays an important role in providing objective criteria for setting up adaptation policies. Many previous assessments of vulnerability have used a composite index because it can incorporate biophysical and socioeconomic aspects of climate change vulnerability relatively easily. Although using a composite index is simple method to assess vulnerability, this method has some limitations; 1) selection of proxy variables for climate change vulnerability is largely dependent on the availability of statistical data. Therefore, some variables are redundant, leading to the multicollinearity problem. 2) There has been little consideration on the “scale” issue in the field of climate change assessment. In this study, we tried to overcome limitations of a composite index by extracting key indicators of climate change vulnerability from the national dataset (a national scale) and the municipal dataset (a municipal scale) using principal component analysis and cluster analysis. The national dataset and the municipal dataset were collected based on indicators being widely used in many studies of international agencies and research institutes of Korea, respectively. These dataset were composed of proxy variables from the section of climate, demographic, health, welfare, agriculture, economic, infrastructure, and education data. As a result, in the national dataset, 18 proxy variables such as GINI index, population density, and life expectancy were extracted from 33 proxy variables. In the municipal dataset, 10 proxy variables such as GRDP, population density, and forest area were extracted from 34 proxy variables. In order to apply this result to the case study, we conducted vulnerability assessment for Jakarta, Indonesia. In the case study, we suggested Geographic Information System and land cover map as a tool to select indicators reflecting spatial status and characteristics of the study area. We also developed the methodology to connect vulnerability assessment with adaptation policies. This study shows that some indicators are important regardless of spatial scales and some indicators reflect characteristics of specific spatial scale. In conclusion, this study emphasizes the significance of contextualization.