The relationship between the atmospheric concentration of cosmogenic isotopes, the change of solar activity and hence secondary neutron flux has already been proven. The temporal atmospheric variation of the most studied cosmogenic isotopes shows a significant anti-correlation with solar cycles. However, since artificial tritium input to the atmosphere due to nuclear-weapon tests masked the expected variations of tritium production rate by three orders of magnitude, the natural variation of tritium in meteoric precipitation has not previously been detected. For the first time, we provide clear evidence of the positive correlation between the tritium concentration of meteoric precipitation and neutron flux modulated by solar magnetic activity. We found trends in tritium time series for numerous locations worldwide which are similar to the variation of secondary neutron flux and sun spot numbers. This variability appears to have similar periodicities to that of solar cycle. Frequency analysis, cross correlation analysis, continuous and cross wavelet analysis provide mathematical evidence that the correlation between solar cycle and meteoric tritium does exist. Our results demonstrate that the response of tritium variation in precipitation to the solar cycle can be used to help us understand its role in the water cycle.

No abstract

Guano is a typical deposit found in caves derived from the excretions of bats and in minor cases of birds. These organic deposits decompose and form a series of acid fluids and gases that can interact with the minerals, sediments, and rocks present in the cave. Over sixty phosphates are known and described from caves, but guano decay also often leads to the formation of nitrates and sulfates. In this study twenty-two European caves were investigated for their guano-related secondary minerals. Using various analytical techniques, seventeen phosphates, along with one sulfate (gypsum), were recognized as secondary products of guano decay. Among those minerals, some are very rare and result from the interaction of guano leachates with clays, fluvial deposits, or pyrite. Some of these minerals are even found only in the studied caves (spheniscidite, robertsite). The most common minerals belong to the apatite group. The common mineral association present in fresh decaying guano is brushiteardealite-gypsum, minerals that usually are not present in older deposits because of their higher solubility. Most minerals are in hydrated form because of the wet cave environment; however, some specific dry conditions may favor the presence of dehydrated minerals, such as berlinite, formed during guano combustion. Investigation on the acidity of guano piles shows pH values as low as 3.5 with an increase of acidity with age and depth. Finally, cave guano deposits should be better studied in the future because of their role in paleoenvironmental and paleoclimatic reconstructions and because it is important to better understand the origin of guano-related minerals, especially the phosphates and sulfates. Among all of the caves studied, Corona 'e sa Craba (Italy) and Domica-Baradla Cave (Slovakia-Hungary) are considered to be outstanding sites with respect to their phosphate mineralogy. secondary cave minerals, phosphates, minerogenesis, limestone caves, bat guano

No abstract