A seven-year (2006–2013) analysis of rain, soil, and drip waters allowed to distinguish between geogenic and anthropogenic influences on the hydrochemistry of the Bunker cave.
The decreasing pattern in infiltration/precipitation from 2000 to 2013 is not very pronounced; however, the continuous draining of the aquifer is visible in decreasing drip rates over the seven-year monitoring period. This is reflected in the long-term increasing trends of Mg/Ca, Sr/Ca ratios induced by PCP, and Cl− concentrations, as well as in the decreasing long-term trend of the Sulfate ion concentrations in several drip sites. For a better understanding of the cave system with its complex processes, a multi-element-proxy long-term cave monitoring of rain, soil, and drip waters appears to be a reasonable step to be followed by the interpretation of the element proxies of speleothems. This monitoring emphasizes Mg/Ca and Sr/Ca ratios, as well as Cl− and in particular sulfate ion concentrations as potential past infiltration/precipitation proxies. Mg/Ca and Sr/Ca ratios are the strongest proxies to reconstruct infiltration/precipitation of measured elements in stalagmites, in cases Sr/Ca is not overprinted by growth rate influences. In addition, the sulphur concentration in speleothems may be an infiltration/precipitation proxy in the case of a geogenic source from the host rock.
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