生物炭與鹽度對人工濕地溫室氣體排放之影響

Abstract

面對持續升高的地表溫度，如何增加碳匯以平衡碳源成為迫在眉睫的議題。其中，濕地作為甲烷的自然排放源卻也具有碳匯的潛力。而利用人工濕地處理廢水的能耗大幅低於其他處理程序，若能解決甲烷排放的問題便可使人工濕地成為扭轉全球暖化的關鍵。生物炭為生物質經高溫熱裂解後的產物，並於許多研究中被證明具有改質土壤及降低溫室氣體排放的潛力。本研究利用不同生物炭比例改質人工濕地，並調整進流鹽度(0、5、10、15 psu)以檢視生物炭改質感潮人工濕地的潛力。結果顯示0 psu 時，添加25%、50%及100%生物炭的人工濕地與未添加生物炭的人工濕地比約可降低 44%、69.6%、81.6%的甲烷通量。5 psu 時， 添加25%、50%及 100%生物炭的人工濕地與未添加生物炭的人工濕地比約可降低12.2%、9.5%、76.3%的甲烷通量。10 psu時，添加 25%生物炭的人工濕地與未添加生物炭的人工濕地比約增加3.4%的甲烷通量，而添加 50%及 100%生物炭的人工濕地與未添加生物炭的人工濕地比約可降低 47.2%、61.2%的甲烷通量。15 psu時，添加25%生物炭的人工濕地與未添加生物炭的人工濕地比約增加2.7%的甲烷通量，添加 50%及 100%生物炭的人工濕地與未添加生物炭的人工濕地比約可降低38.1%、46.7%的甲烷通量。功能性基因的結果顯示，生物炭可以有效提高甲烷氧化菌、硫酸鹽還原菌及硝化菌的相對豐度，使其甲烷通量大幅低於未改質的人工濕地。而於感潮人工濕地中，生物炭仍可提高甲烷氧化菌、硫酸鹽還原菌及硝化菌的相對豐度並減少甲烷通量。然而，感潮濕地中硫酸鹽還原菌對甲烷通量的影響仍需更進一步的研究。

Facing the rising global surface temperature, increasing carbon sinks to balance carbon sources has become an urgent issue. Wetlands, although natural sources of methane emissions, also possess potential as carbon sinks. Utilizing constructed wetlands for wastewater treatment consumes significantly less energy than other treatment processes. If the issue of methane emissions can be addressed, constructed wetlands could become a key factor in mitigating global warming. Biochar, a product of biomass pyrolysis at high temperatures, has been proven in many studies to have the potential for soil amendment and reducing greenhouse gas emissions. This study used different proportions of biochar to amend constructed wetlands and adjusted the inflow salinity (0, 5, 10, 15 psu) to assess the potential of biochar-amended tidal constructed wetlands. The result showed that at the salinity of 0 psu, methane flux of constructed wetlands with 25%, 50%, and 100% biochar additions can be reduced by approximately 44%, 69.6%, and 81.6%, respectively, compared to constructed wetlands without biochar. At the salinity of 5 psu, the methane flux of constructed wetlands with 25%, 50%, and 100% biochar additions can be reduced by approximately 12.2%, 9.5%, and 76.3%, respectively, compared to those without biochar. At the salinity of 10 psu, the methane flux of constructed wetlands with 25% biochar addition increased by approximately 3.4% compared to those without biochar, while the methane flux of constructed wetlands with 50% and 100% biochar additions can be reduced by approximately 47.2% and 61.2%, respectively, compared to those without biochar. At the salinity of 15 psu, the methane flux of constructed wetlands with 25% biochar addition increased by approximately 2.7% compared to those without biochar, while the methane flux of constructed wetlands with 50% and 100% biochar additions can be reduced by approximately 38.1% and 46.7%, respectively, compared to those without biochar. Functional gene analysis shows that biochar effectively increases the relative abundance of methanotrophs, sulfate-reducing bacteria, and nitrifying bacteria, leading to significantly lower methane flux in biochar-amended constructed wetlands compared to those without biochar. Furthermore, biochar continues to enhance the relative abundance of methanotrophs, sulfate-reducing bacteria, and nitrifying bacteria in tidal constructed wetland, thereby reducing methane flux. However, the influence of sulfate-reducing bacteria on methane flux in tidal constructed wetland requires further investigation.