基于过程模型的青藏高原湿地甲烷排放格局评估

甲烷(CH_4)是大气中最丰富的碳氢化合物,是仅次于二氧化碳(CO_2)的温室气体。湿地是甲烷的重要来源,在全球碳循环中发挥着重要作用,其排放的甲烷占所有天然甲烷排放源的70%,占全球甲烷排放总量的24.8%。青藏高原平均海拔4000 m以上,占有中国约三分之一的湿地。近几十年来,由于全球气候变暖和降水增加,该地区甲烷排放率和湿地面积都发生着巨大变化,因此,青藏高原湿地CH_4排放的长期变化在很大程度上仍存在较大的不确定性。利用TRIPLEX-GHG模型模拟了青藏高原湿地1978—2008年CH_4排放的动态特征,研究结果表明:(1)1978—2008年青藏高原湿地CH_4排放速率呈逐渐增加趋势。(2)青藏高原大多数湿地区域CH_4排放速率为0—6.13 g CH_4 m~(-2 )a~(-1);东北部分湿地区域CH_4排放速率为6.14—20.19 g CH_4 m~(-2 )a~(-1);较高的CH_4排放速率分布于青藏高原南部湿地区域,为56.14—74.97 g CH_4 m~(-2 )a~(-1)。(3)青藏高原湿地CH_4排放量在1978、1990、2000年和2008年分别为0.21、0.23、0.27和0.32 Tg CH_4 a~(-1)。在1978—1990年,尽管CH_4排放速率增加,但湿地面积减少,因此这一时期青藏高原湿地CH_4排放量并未发生明显变化。随后由于降水增加和冰川融化,使得湿地面积逐渐增加,青藏高原湿地CH_4排放量也呈现增加趋势。

Evaluating patterns of wetland methane emissions in Qinghai-Tibet plateau based on process model

Methane (CH₄) is the most abundant hydrocarbon in the atmosphere, only second to carbon dioxide (CO₂) as a greenhouse gas. Wetlands are an important source of methane and play an important role in the global carbon cycle. They account for 70% of all natural methane emissions and 24.8% of global methane emissions. The Qinghai-Tibet Plateau (QTP) has an average elevation of more than 4000 m and contains one-third of China''s wetlands. In recent decades, due to global warming and increased precipitation, methane emission rate and wetland area in the region have undergone great changes, so the long-term change of CH₄ emissions is still largely uncertainty. In this study, the TRIPLEX-GHG model was used to simulate the dynamic characteristics of CH₄ emissions from wetlands on the QTP from 1978 to 2008. The results showed that: (1) CH₄ emission rate in QTP wetlands were gradually increasing from 1978 to 2008. (2) CH₄ emission rate in most wetland areas of the QTP was 0-6.13 g CH₄ m^-2a^-1 and in some wetland areas of northeast QTP was 6.14-20.19 g CH₄ m^-2a^-1. The higher CH₄ emission rate distributed in the wetland areas of the southern QTP was 56.14-74.97 g CH₄ m^-2a^-1. (3) Total CH₄ emissions in 1978, 1990, 2000, and 2008 were 0.21, 0.23, 0.27, and 0.32 Tg CH₄ a^-1, respectively. The analyses indicated that although the CH₄ emission rate increased, the wetland area decreased from 1978 to 1990, therefore, CH₄ emissions did not change significantly in this period. Due to the continuous increase of precipitation and glacier melting, the wetland area gradually increased after 2000. With the combination of increasing wetland area and wetland CH₄ emission rate, the total CH₄ emissions of the QTP wetlands had a continuously creasing trend.