Institute for Agro-Environmental Sciences, National Agriculture and Food Research Organization, 3-1-3 Kannondai, Tsukuba, Ibaraki 305-8604, Japan.
Institute for Agro-Environmental Sciences, National Agriculture and Food Research Organization, 3-1-3 Kannondai, Tsukuba, Ibaraki 305-8604, Japan.
Sci Total Environ. 2017 Dec 1;601-602:346-355. doi: 10.1016/j.scitotenv.2017.05.090. Epub 2017 May 29.
Methane (CH) is a greenhouse gas, and paddy fields are one of its main anthropogenic sources. In Japan, country-specific emission factors (EFs) have been applied since 2003 to estimate national-scale CH emission from paddy field. However, these EFs did not consider the effects of factors that influence CH emission (e.g., amount of organic C inputs, field drainage rate, climate) and can therefore produce estimates with high uncertainty. To improve the reliability of national-scale estimates, we revised the EFs based on simulations by the DeNitrification-DeComposition-Rice (DNDC-Rice) model in a previous study. Here, we estimated total CH emission from paddy fields in Japan from 1990 to 2010 using these revised EFs and databases on independent variables that influence emission (organic C application rate, paddy area, proportions of paddy area for each drainage rate class and water management regime). CH emission ranged from 323 to 455ktCyr (1.1 to 2.2 times the range of 206 to 285ktCyr calculated using previous EFs). Although our method may have overestimated CH emissions, most of the abovementioned differences were presumably caused by underestimation by the previous method due to a lack of emission data from slow-drainage fields, lower organic C inputs than recent levels, neglect of regional climatic differences, and underestimation of the area of continuously flooded paddies. Our estimate (406ktC in 2000) was higher than that by the IPCC Tier 1 method (305ktC in 2000), presumably because regional variations in CH emission rates are not accounted for by the Tier 1 method.
甲烷（CH）是一种温室气体，稻田是其主要人为排放源之一。在日本，自 2003 年以来，一直应用特定于国家的排放因子（EF）来估算全国稻田 CH 排放量。然而，这些 EF 没有考虑影响 CH 排放的因素（例如，有机 C 输入量、田间排水率、气候）的影响，因此可能会产生高度不确定的估计值。为了提高国家尺度估算的可靠性，我们在前一项研究中基于 DeNitrification-DeComposition-Rice（DNDC-Rice）模型的模拟结果修订了 EF。在这里，我们使用这些修订后的 EF 和影响排放的独立变量（有机 C 施用量、稻田面积、每个排水率等级和水管理制度的稻田面积比例）数据库，估算了 1990 年至 2010 年日本稻田的总 CH 排放量。CH 排放量在 323 至 455ktCyr 之间（比使用先前 EF 计算的 206 至 285ktCyr 范围高 1.1 至 2.2 倍）。尽管我们的方法可能高估了 CH 排放，但由于缺少慢排水田的排放数据、低于当前水平的有机 C 输入、忽略了区域气候差异以及低估了连续淹水田的面积，导致大部分上述差异可能是由于先前方法的低估所致。我们的估算值（2000 年为 406ktC）高于 IPCC Tier 1 方法（2000 年为 305ktC），这可能是因为 Tier 1 方法没有考虑 CH 排放率的区域差异。
