Temporal variation in dripwater chemistry in the Cueva del Pindal (Asturias, NW of Spain)

Resumen

The Pindal Cave (Asturias, NW of Spain) is hosted by limestones of the Barcaliente Formation 24 m above sea level and in close proximity (50 m) to the coastal sea cliffs For eleven months, dripwater flow was collected in 153 discrete samples each representing integrated flow over 48 hours. Dripwater flow rate is compared with precipitation and the major element chemistry of dripwaters. Dripwaters flow rates vary dramatically from samiple to sample typically lagging pecripitation peaks by 1-3 days. Overall dripwater flow is highest in the wet winter season and lowest in the dry summer season. Concentrations of Ca vary dramatically from sample to sample and are highly positively correlated with the daily-weekly variations in dripwater flow. Mean Ca concentrations are comparable during summer and winter months, despite lower summer drip flow, probably because higher soil CO2 during the summer growing season increases dissolution of host rock during infiltration, compensating for longer Ca residence times. Sr/Ca ratios and Mg/Ca ratios correlate inversely with dripwater flow rates, and together with Ca variations imply variable precipitation of calcite during aquifer throughflow. The concentration of Na in dripwaters reflects prevailing wind direction and transport of sea salt aerosols into the cave drainage basin and correlates with the NAO index, where as concentrations of K are influenced by biological uptake and episodic anthropogenic imputs.