Wavelet-based multiscale analysis of cave CO₂ concentration in response to short-term high-intensity tourism activities: spatiotemporal heterogeneity and lag characteristics

Authors

• Mingda Cao, Chizhou University, ChinaFollow
• Wenwen Song, Chizhou University, ChinaFollow
• Yan Zhang, Chizhou University, ChinaFollow
• Jie Zhang, Chizhou Univesity, ChinaFollow
• Zhiqiang Yao, Chizhou University, ChinaFollow

Highlights

• Tourist respiration dominates cave CO₂ diurnal variation
• Cave ventilation controls spatial heterogeneity of CO₂
• Semi-diurnal CO₂ period appears during peak tourist period
• Lag time of CO₂ behind tourists is 3-6 h during peak period
• Full-period average lag (54-72 h) is controlled by memory effect

Abstract

High-intensity tourism activities can cause a significant increase in cave air CO₂ concentration, thereby affecting the cave micro-environment and secondary carbonate deposition. During the 2023 National Day Golden Week, high-frequency continuous monitoring of cave air CO₂ partial pressure (PCO_2(A)) and visitor numbers was conducted in Dawang Cave, Anhui Province. Wavelet transform and cross-correlation analyses were used to reveal the multi-scale response characteristics of CO₂ concentration to tourism activities. The results show that: (1) PCO_2(A) exhibited clear diurnal variations (higher during the day, lower at night) and decreased spatially with enhanced ventilation, controlled jointly by cave morphology, ventilation conditions, and tourist activity. (2) Wavelet periodicity analysis revealed that all three monitoring sites (DW1# near entrance, DW2# rest area, DW3# deep chamber) showed a 24‑hour diurnal period, but with different intensities; DW2# exhibited a distinct semi‑diurnal period during the peak tourist period, while DW3# showed longer‑period (>48 h) signals. (3) Coherence spectrum analysis indicated that the coherence coefficient between CO₂ and visitor numbers at the diurnal period exceeded 0.6 for all three sites (p0.8) at DW2#. (4) Cross‑correlation analysis showed that the lag time of CO₂ behind visitor numbers during the peak tourist period was 3–6 h (DW1#: 6 h, DW2#: 3 h, DW3#: 5 h), whereas the full‑period average lag was as long as 54–72 h, the latter being controlled by a “memory effect” during off‑peak hours. This study provides a scientific basis for assessing environmental carrying capacity, visitor management, and sedimentary landscape protection in tourist caves.

DOI

https://doi.org/10.5038/1827-806X.ijs2618

Creative Commons License

This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 License.

Recommended Citation

Cao, M., Song, W., Zhang, Y., Zhang, J., Yao, Z., 2026. Wavelet-based multiscale analysis of cave CO2 concentration in response to short-term high-intensity tourism activities: spatiotemporal heterogeneity and lag characteristics. International Journal of Speleology, 55(2), ijs2618. https://doi.org/10.5038/1827-806X.ijs2618