Carbon dioxide (CO₂) concentration (CDC) is an essential parameter of underground atmospheres for safety and cave heritage preservation. In the Chauvet cave (South France), a world heritage site hosting unique paintings dated 36,000 years BP, a high-sensitivity monitoring, ongoing since 1997, revealed: 1) two compartments with a spatially uniform CDC, a large volume (A) (40,000 to 80,000 m³) with a mean value of 2.20 ± 0.01% vol. in 2016, and a smaller remote room (B) (2000 m³), with a higher mean value of 3.42 ± 0.01%; 2) large CDC annual variations with peak-to-peak amplitude of 2% and 1.6% in A and B, respectively; 3) long-term changes, with an increase of CDC and of its annual amplitude since 1997, then faster since 2013, reaching a maximum of 4.4% in B in 2017, decreasing afterwards. While a large effect of seasonal ventilation is ruled out, monitoring of seepage at two dripping points indicated that the main control of CDC seasonal reduction was transient infiltration. During periods of water deficit, calculated from surface temperature and rainfall, CDC systematically increased. The carbon isotopic composition of CO₂, correlated with water excess, is consistent with a time-varying component of CO₂ seeping from above. The CO₂ flux, which is the primary driver of CDC in A and B, inferred using box modelling, was found to confirm the relationship between water excess and reduced CO₂ flux into A, compatible with a more constant flux into B. A buoyancy-driven horizontal CO₂ flow model in the vadose zone, hindered by water infiltration, is proposed. Similarly, pluri-annual and long-term CDC changes can likely be attributed to variations of water excess, but also to increasing vegetation density above the cave. As CDC controls the carbonate geochemistry, an increased variability of CDC raises concern for the preservation of the Chauvet cave paintings.

二氧化碳（CO ₂）浓度（CDC）是地下大气安全和洞穴遗产保护的重要参数。在Chauvet洞穴（法国南部）中，一个世界遗产地保存着36,000年BP的独特画作，自1997年以来一直在进行高灵敏度监测，结果显示：1）两个隔室，其空间均匀CDC，体积较大（A）（ 40,000至80,000 m ³），平均值为2.20±0.01％vol。在2016年，以及一个较小的远程房间（B）（2000 m ³），平均值较高，为3.42±0.01％；2）CDC的年度变化较大，A和B的峰峰值分别为2％和1.6％；3）长期变化，CDC及其自1997年以来的年度振幅增加，然后自2013年以来更快，2017年B的最大值达到4.4％，此后下降。尽管排除了季节性通风的较大影响，但监测两个滴水点的渗漏表明，CDC季节性减少的主要控制是瞬时渗透。在根据地表温度和降雨计算的缺水时期，CDC有系统地增加。与水过量相关的CO ₂的碳同位素组成与从上方渗出的CO ₂的时变成分一致。一氧化碳₂使用盒模型推断出的通量是CDC在A和B中的主要驱动力，它被证实可以确认过量水分和减少的CO ₂通向A的通量之间的关系，这与通向B的恒定通量是相容的。提出了渗流阻碍渗流区CO ₂流动的模型。同样，多年期和长期CDC变化可能归因于水过量的变化，也可能归因于洞穴上方的植被密度增加。由于CDC控制着碳酸盐地球化学，CDC的变化性增加引起了对Chauvet洞穴壁画保存的关注。