作为英国政府资助的更新英国N2O清单方法的研究项目的一部分,对已发表的非英国研究的一氧化二氮(N2O)排放因子进行了系统评价,用于未来与英国基于测量的证据基础的比较和综合。该研究的目的是评估英国IPCC合成或有机肥料投入(EF1)产生的N2O排放的默认排放因子与已发表文献中报告的国际值的比较。评估了用于比较和/或完善英国IPCC默认值的数据的可用性,以及分析足够的辅助数据以提出Tier2EF1报告策略的可能性。该评论表明,在报告肥料衍生EF和N2O通量数据的误差范围方面缺乏一致性,分别有8%和44%的出版物报告EF和N2O通量误差范围。对环境(气候和土壤)和实验设计辅助数据的描述也很差。这可能是由于研究目标的差异,然而,提出了对土壤参数报告的潜在改进。审查表明,与英国一级IPCCEF1默认值1.25%(IPCC1996)和1%(IPPC2006)相比,农业衍生的N2O排放的排放因子范围为-0.34%至37%,差异很大。然而,英国相关土壤报告的大多数EF(83%)属于英国IPCCEF1不确定度范围0.03%~3%.对评论中整理的数据进行的残余最大似然(REML)分析表明,施氮量和土壤类型是影响所报告EF的重要因素。排放国家,测量周期的长度,拆分的数量,作物类型,pH和SOC对N2O排放没有显著影响。确定了报告了足够数据进行荟萃分析的出版物子集。对41种处理效果大小的荟萃分析表明,与对照地块相比,施肥对N2O排放有显着影响,排放因子显着差异为零。然而,与对照地块相比,施肥量与施肥地块排放的N2O量的影响大小之间没有显着关系。与对照处理相比,每年添加35至557kgN/ha的肥料的平均排放量增加了2.02±0.28gN2O/ha/天(p<0.01)。排放因子明显不同于零,根据荟萃分析直接估计的平均排放因子为0.17±0.02%。这低于IPCC2006第1级EF1值的1%,但在IPCC2006第1级EF1的不确定性范围内(0.03%至3%)。由于缺乏关键控制因素的报告,只有少数论文可以进行荟萃分析,本文对EF的估计不能包括与英国相似条件下的真实变异性。审查得出的EF为0.34%至37%,荟萃分析得出的平均EF为0.17±0.02%,这突出了报告EF的变异性,具体取决于所应用的方法和样本量。提出了跨学科出版物中N2O排放和关键辅助参数的系统报告协议。如果采用,这将加强社区为IPCCTier2报告发展提供信息,并减少报告的英国N2O排放周围的不确定性。
As part of a UK government funded research project to update the UK N2O inventory methodology, a systematic
review of published nitrous oxide (N2O) emission factors was carried out of non-UK research, for future comparison and synthesis with the UK measurement based evidence base. The aim of the study is to assess how the UK IPCC default emission factor for N2O emissions derived from synthetic or organic fertiliser inputs (EF1) compares to international values reported in published literature. The availability of data for comparing and/or refining the UK IPCC default value and the possibility of analysing sufficient auxiliary data to propose a Tier 2 EF1 reporting strategy is evaluated. The
review demonstrated a lack of consistency in reporting error bounds for fertiliser-derived EFs and N2O flux data with 8% and 44% of publications reporting EF and N2O flux error bounds respectively. There was also poor description of environmental (climate and soil) and experimental design auxiliary data. This is likely to be due to differences in study objectives, however potential improvements to soil parameter reporting are proposed. The
review demonstrates that emission factors for agricultural-derived N2O emissions ranged -0.34% to 37% showing high variation compared to the UK Tier 1 IPCC EF1 default values of 1.25% (IPCC 1996) and 1% (IPPC 2006). However, the majority (83%) of EFs reported for UK-relevant soils fell within the UK IPCC EF1 uncertainty range of 0.03% to 3%. Residual maximum likelihood (REML) analysis of the data collated in the
review showed that the type and rate of fertiliser N applied and soil type were significant factors influencing EFs reported. Country of emission, the length of the measurement period, the number of splits, the crop type, pH and SOC did not have a significant impact on N2O emissions. A subset of publications where sufficient data was reported for meta-analysis to be conducted was identified. Meta-analysis of effect sizes of 41 treatments demonstrated that the application of fertiliser has a significant effect on N2O emissions in comparison to control plots and that emission factors were significantly different to zero. However no significant relationships between the quantity of fertiliser applied and the effect size of the amount of N2O emitted from fertilised plots compared to control plots were found. Annual addition of fertiliser of 35 to 557 kg N/ha gave a mean increase in emissions of 2.02 ± 0.28 g N2O/ha/day compared to control treatments (p<0.01). Emission factors were significantly different from zero, with a mean emission factor estimated directly from the meta analysis of 0.17 ± 0.02%. This is lower than the IPCC 2006 Tier 1 EF1 value of 1% but falling within the uncertainty bound for the IPCC 2006 Tier 1 EF1 (0.03% to 3%). As only a small number of papers were viable for meta analysis to be conducted due to lack of reporting of the key controlling factors, the estimates of EF in this paper cannot include the true variability under conditions similar to the UK.
Review-derived EFs of 0.34% to 37% and mean EF from meta-analysis of 0.17 ± 0.02% highlight variability in reporting EFs depending on the method applied and sample size. A protocol of systematic reporting of N2O emissions and key auxiliary parameters in publications across disciplines is proposed. If adopted this would strengthen the community to inform IPCC Tier 2 reporting development and reduce the uncertainty surrounding reported UK N2O emissions.