Quern (“/kern/”) is a non-parametric estimator of Heavily Tailed Breakthrough Curves from Particle Tracking simulations, based on Adaptive Kernel Density Estimators. The code is based on D. Pedretti and D. Fernandez-Garcia (2013) "An automatic locally-adaptive method to estimate heavily-tailed breakthrough curves from particle distributions", Advances in Water Resources Vol. 59 p. 52-65 (doi: 10.1016/j.advwatres.2013.05.006) which we refer for details about the selection of the adaptive factor (alpha). The zip folder contains the executable and the input files. An example drawn from the paper (case k=1,\beta=1, n=10^4) is also added with the input file (times.dat). This ASCII file is a column of arrival times. We have not tested the Binary entry mode, which can generate bugs and that would be fixed in future versions of the code. The current version (1.0) allows only one species. Future versions will expand it to multispecies calculations.