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Underground TWH caverns in salt rock have high construction efficiency and large usable volumes and provides an ideal space for large-scale natural gas storage. In this study, the solution mining process of TWH cavern is thoroughly analyzed. Applying basic principles of the Navier-Stokes equation method and reasonable assumptions, we established a new 3D mathematical model which includes flow and mass transfer and boundary movement for TWH salt cavern construction. Then, the velocity field and the concentration field can be solved by the SIMPLE algorithm, while the boundary movement of cavern expansion can be solved by the VOF algorithm. We developed a new VC++ computer code program TWHSMC for solution mining and herein we present the numerical results. Finally, the simulation cavern shapes results by program are compared with the experimental ones. The results indicate that our model successfully and accurately predicts the cavern shape and demonstrates the reliability and applicability of the model.

Atmospheric nitrous oxide (N2O) contributes directly to global warming, yet current models1-5 overlook bedrock-contained nitrogen (rock-N), the largest terrestrial N pool6, as a N2O source. Although rock-N release rates are large6-9, incomplete understanding on the fate of released rock-N has obscured connections between rock-N and atmospheric N2O. This connection emerged through our field studies of a hillslope underlain by marine shale. Bedrock weathering within the zone of the seasonally fluctuating water table controls the weathering depth, hence the release of rock-N. At this site, rock-N weathering contributes 78% of the subsurface reactive-N, with ~22% derived from atmospheric deposition and biological nitrogen fixation, commonly regarded as the sole sources of reactive-N in pristine environments10,11. About 56% of reactive-N denitrifies, including 14% emitted as N2O into the atmosphere. The remaining reactive-N discharges in porewaters to a floodplain where additional denitrification likely occurs. Using global rock-N releases of 11–18 Tg y-1 8, our measurements extrapolate to a weathering driven efflux of 1.3–2.1 Tg N-N2O y-1, consistent with a flux of 1.0–1.7 Tg N- N2O y-1 solely derived from the literature. Thus, bedrock weathering contributes approximately 10-17 % of nitrous oxide to the current global estimate of ~10 Tg y-1.

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