近年來溫室氣體快速增加，且根據IPCC 2021年的報告指出，N2O及CH4的全球溫暖化潛勢（Global Warming Potential， GWP）分別為265與28，意即排放一噸N2O相當於排放265噸CO2，因此降低N2O及CH4的排放成為全球淨零碳排的重要議題。而一氧化二氮(N2O)主要排放來源為農業，農業活動中使用大量氮肥，過多的氮肥在土壤中容易流失或是被微生物過度利用，尤其是在水稻田中，當水稻田覆水缺氧時，微生物產生較多CH4，而一般旱田或是當水稻田排水期間，在有氧環境下微生物進行大量硝化作用及少量脫硝作用，產生大量N2O，並釋放在缺氧期間脫硝作用所產生的N2O，造成溫室氣體的增加。近年來常使用生物炭作為土壤改良劑及土壤緩釋劑，用其吸附及穩定土壤或水溶液中的物質，因此本研究製備350℃及700℃的咖啡渣生物炭(BC350、BC700)，並另取300℃及600℃的樟樹落葉生物炭(LB300、LB600)，將其進行酸淋洗及丙烯酸改質，並針對氮肥中的主要含氮成分，包括以帶正電銨離子型態存在之氨氮，以及不帶電之尿素，在25mg-N/L的濃度下添加1% (w/v)生物炭進行動力學吸附、等溫吸附、動學脫附實驗，並探討生物炭特性與其吸附機制。由實驗結果可得，低溫的咖啡渣生物炭及改質後的生物炭因為含有較多的含氧官能基，能夠有較高的氨氮吸附量，尤其是改質後生物炭表面增加較多的含氧官能基，能夠快速吸附氨氮，其吸附機制偏向化學吸附，並在動力學脫附實驗中，達到緩慢脫附氨氮的效果。而酸淋洗後生物炭對尿素有較佳吸附效果，因為酸淋洗會去除生物炭表面及孔隙中的雜質，增加尿素可吸附之活性位點，較偏向物理吸附，並在動力學脫附實驗中快速脫附尿素。實驗結果可得，改質後生物炭較適合當作土壤緩釋劑，並可以預期加入土壤後，可以快速吸附尿素水解後的氨氮，減少微生物對其的利用，並減少微生物的硝化-脫硝作用，盼能減少N2O的排放。;In recent years， greenhouse gas concentrations have increased rapidly. According to the IPCC 2021 report， the global warming potentials (GWPs) of nitrous oxide (N2O) and methane (CH4) are 265 and 28， respectively. This means that the emission of one ton of N2O is equivalent to the emission of 265 tons of CO2. Therefore， reducing N2O and CH4 emissions has become an important issue in achieving global net-zero carbon emissions. Agriculture is the major source of nitrous oxide (N2O) emissions. Large amounts of nitrogen fertilizers are applied in agricultural activities， and excessive nitrogen fertilizer can be easily lost from the soil or excessively utilized by microorganisms. In particular， in paddy fields， when the soil is flooded and anaerobic conditions develop， microorganisms tend to produce more CH4. In contrast， in upland fields or during the drainage period of paddy fields， microorganisms carry out extensive nitrification and a smaller degree of denitrification under aerobic conditions， resulting in the production of large amounts of N2O. In addition， N2O produced through denitrification during anaerobic periods may also be released， further contributing to greenhouse gas emissions and climate change. In recent years， biochar has frequently been used as a soil amendment and soil slow-release material due to its ability to adsorb and stabilize substances in soil or aqueous solutions. Therefore， in this study， coffee-ground biochars were prepared at 350°C and 700°C， and camphor leaf biochars prepared at 300°C and 600°C were also used. These biochars were subjected to acid washing and acrylic acid modification. The adsorption and desorption behaviors of the major nitrogen-containing components in nitrogen fertilizers were investigated， including ammonium nitrogen， which exists as positively charged ammonium ions， and urea， which is electrically neutral. Kinetic adsorption， isothermal adsorption， and kinetic desorption experiments were conducted at a concentration of 25 mg-N/L with the addition of 1% (w/v) biochar. The characteristics of the biochars and their adsorption mechanisms were also discussed. The experimental results showed that low-temperature coffee-ground biochar and modified biochar exhibited higher ammonium nitrogen adsorption capacities due to their greater abundance of oxygen-containing functional groups. In particular， the modified biochar showed a significant increase in oxygen-containing functional groups on its surface， enabling rapid adsorption of ammonium nitrogen. The adsorption mechanism was more closely associated with chemisorption. In the kinetic desorption experiment， the modified biochar also achieved a slow-release effect for ammonium nitrogen. In contrast， acid-washed biochar showed better adsorption performance for urea. This may be attributed to the removal of impurities from the biochar surface and pores during acid washing， which increased the number of active sites available for urea adsorption. The adsorption mechanism was more likely dominated by physical adsorption， and urea was rapidly desorbed in the kinetic desorption experiment. Overall， the experimental results indicate that modified biochar is more suitable as a soil slow-release material. After being applied to soil， it is expected to rapidly adsorb ammonium nitrogen generated from urea hydrolysis， thereby reducing microbial utilization of ammonium nitrogen and decreasing microbial nitrification–denitrification processes. This may potentially contribute to the reduction of N2O emissions.
