We present ground-based atmospheric measurements of ratios between anthropogenic carbon monoxide (CO_an) and carbon dioxide (CO_2an) (β^–1 ratios) in Cookeville, Tennessee (36.1628° N, 85.5016° W), a medium-sized city located within the Eastern Highland Rim region of the United States, obtained using a continuous wavelength-scanned cavity ring-down spectrometer (CRDS). In contrast to the summer season, the winter and spring β^–1 values are reasonably high, where a tight correlation between the above-background mole fractions of CO and CO₂ is exhibited (as given by the high R² value). The winter season is characterized by relatively high CO_an than biospheric CO₂ signals (CO_2Bio) due to fossil fuel heating sources and reduced biospheric uptake of CO₂. The lowest estimated seasonal background CO₂ and CO mole fractions during the study period are 407.1 ± 11.3 ppm and 144.9 ± 2.1 ppb, respectively. During the summer, the biogenic CO source from isoprene oxidation collocates with direct anthropogenic CO sources, leading to uncertainties in the calculated summertime β^–1 values. For 2017, β^–1 values (ppb:ppm) of 9.7 ± 0.4, 5.3 ± 0.4, and 2.0 ± 0.2 were obtained for the winter, spring and summer seasons, respectively. In 2018, a similar seasonal variability in the β^–1 ratios was obtained with values of 8.7 ± 0.5, 7.4 ± 0.7, and 2.6 ± 0.5 for winter, spring, and summer seasons, respectively. While the estimated percentage contribution of the oxidation reaction between the OH radical and isoprene (CH₂═C(CH₃)–CH═CH₂ + OH) to the total summertime CO budget is less than 50%, the relative amounts may be significant enough to imply that any future study based on the CO as a tracer of combustion emission should account for its photochemical production through biogenic volatile organic compounds in the summertime.

中文翻译：

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使用CO示踪技术对东部高原沿岸的CO：CO ₂比率进行地基大气测量

我们提供了田纳西州库克维尔市（36.1628°N，85.5016°W）（位于中型城市）的人为一氧化碳（CO _an）与二氧化碳（CO _2an）之比（β ^–1比率）的地面大气测量值。使用连续波长扫描型腔衰荡光谱仪（CRDS）获得的美国东部高地边缘地区的辐射。与夏季相反，冬季和春季的β ^–1值相当高，在上述背景下，CO和CO _2的摩尔分数之间表现出紧密的相关性（如高R ²值所示）。冬季的特征在于相对高的CO_的由于化石燃料加热源和生物圈对CO _2的吸收减少，生物圈CO ₂信号（CO _2Bio）比生物圈CO ₂信号要大。在研究期间，估计的最低季节性本底CO ₂和CO摩尔分数分别为407.1±11.3 ppm和144.9±2.1 ppb。在夏季，来自异戊二烯氧化的生物CO源与直接的人为CO源并存，导致计算得出的夏季β ^–1值存在不确定性。对于2017年，冬季，春季和夏季的β ^–1值（ppb：ppm）分别为9.7±0.4、5.3±0.4和2.0±0.2。2018年，β ^–1的季节性变化类似冬季，春季和夏季的比率分别为8.7±0.5、7.4±0.7和2.6±0.5。尽管OH自由基和异戊二烯（CH之间的氧化反应的估计百分比贡献₂ = C（CH ₃）-CH = CH ₂ + OH）对总夏季CO预算是小于50％，相对量可以是显著足以暗示任何基于CO作为燃烧排放示踪剂的未来研究都应考虑到夏季通过生物源性挥发性有机化合物产生的光化学产物。