Department of Civil and Environmental Engineering, University of California at Davis, 1 Shields Ave, Davis, CA 95616, USA.
Environmental Chemistry and Technology Program, University of Wisconsin-Madison, 660 North Park Street, Madison, WI 53706, USA; Environmental Engineering Department, Pontificia Bolivariana University-Bucaramanga, Km 7 Vía Piedecuesta, Bucaramanga, Colombia.
Sci Total Environ. 2015 Dec 15;538:412-22. doi: 10.1016/j.scitotenv.2015.08.030. Epub 2015 Aug 25.
The use of biodiesel as a replacement for petroleum-based diesel fuel has gained interest as a strategy for greenhouse gas emission reductions, energy security, and economic advantage. Biodiesel adoption may also reduce particulate elemental carbon (EC) emissions from conventional diesel engines that are not equipped with after-treatment devices. This study examines the impact of biodiesel blends on EC emissions from a commercial off-road diesel engine and simulates the potential public health benefits and climate benefits. EC emissions from the commercial off-road engine decreased by 76% when ultra-low sulfur commercial diesel (ULSD) fuel was replaced by biodiesel. Model calculations predict that reduced EC emissions translate directly into reduced EC concentrations in the atmosphere, but the concentration of secondary particulate matter was not directly affected by this fuel change. Redistribution of secondary particulate matter components to particles emitted from other sources did change the size distribution and therefore deposition rates of those components. Modification of meteorological variables such as water content and temperature influenced secondary particulate matter formation. Simulations with a source-oriented WRF/Chem model (SOWC) for a severe air pollution episode in California that adopted 75% biodiesel blended with ULSD in all non-road diesel engines reduced surface EC concentrations by up to 50% but changed nitrate and total PM2.5 mass concentrations by less than ±5%. These changes in concentrations will have public health benefits but did not significantly affect radiative forcing at the top of the atmosphere. The removal of EC due to the adoption of biodiesel produced larger coatings of secondary particulate matter on other atmospheric particles containing residual EC leading to enhanced absorption associated with those particles. The net effect was a minor change in atmospheric optical properties despite a large change in atmospheric EC concentrations. These results emphasize the importance of considering EC mixing state in climate research.
生物柴油作为一种替代石油基柴油燃料的策略，因其在减少温室气体排放、能源安全和经济优势方面的潜力而受到关注。生物柴油的采用也可能减少未配备后处理装置的传统柴油发动机的颗粒元素碳 (EC) 排放。本研究考察了生物柴油混合物对商业非道路柴油机 EC 排放的影响，并模拟了潜在的公共健康和气候效益。当超低硫商业柴油 (ULSD) 燃料被生物柴油取代时，商业非道路发动机的 EC 排放量减少了 76%。模型计算预测，EC 排放量的减少直接导致大气中 EC 浓度的降低，但这种燃料变化并没有直接影响二次颗粒物的浓度。二次颗粒物成分向其他来源排放的颗粒物的再分配确实改变了这些成分的粒径分布和沉积速率。气象变量（如水含量和温度）的变化会影响二次颗粒物的形成。在加利福尼亚州一次严重空气污染事件中，采用了 SOWC（面向源的 WRF/Chem 模型）进行模拟，该模型假设所有非道路柴油机中 75%的生物柴油与 ULSD 混合，这使得地表 EC 浓度降低了高达 50%，但硝酸盐和总 PM2.5 质量浓度的变化不到±5%。这些浓度的变化将带来公共健康效益，但对大气顶层的辐射强迫影响不大。由于采用生物柴油而去除的 EC 导致其他含有残留 EC 的大气颗粒上形成更大的二次颗粒物涂层，从而导致与这些颗粒相关的吸收增强。尽管大气 EC 浓度发生了很大变化，但净效应是大气光学性质的微小变化。这些结果强调了在气候研究中考虑 EC 混合状态的重要性。
