Open AccessDesign and Testing of a Drop Counter for Use in Vadose Zone Water Samplers
Author(s) -
Mertens Jan,
Tuts Valentijn,
Diels Jan,
Vanderborght Jan,
Feyen Jan,
Merckx Roel
Publication year - 2008
Publication title -
vadose zone journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.036
H-Index - 81
ISSN - 1539-1663
DOI - 10.2136/vzj2007.0096
Subject(s) - leachate , vadose zone , drop (telecommunication) , data logger , environmental science , temporal resolution , soil science , capillary action , hydrology (agriculture) , materials science , chemistry , geology , geotechnical engineering , soil water , optics , composite material , computer science , environmental chemistry , physics , operating system , telecommunications
Measuring leachate mobility in the vadose zone is necessary to understand the processes controlling groundwater and river contamination, and requires recording leachate volumes with time. Many field studies manually measure the volume of leachate with a daily, weekly, or even biweekly resolution; however, measurement of leachate at higher temporal resolution is needed for the calibration of solute transport models and is useful in identifying the contribution of preferential flow to solute transport. We designed a simple, robust, and low‐cost drop counter for measuring leachate volumes at a high temporal resolution. Laboratory experiments showed a nearly perfect linear relationship between the applied flux and the number of drops per unit time, and indicate an average drop size of 35 μL. Due to manual manufacturing, variability between drop counters is not negligible and a one‐point calibration is necessary. The drop counter consists of an upper (guiding) tube from which a drop forms and a lower (capillary) tube that “sucks” the drop down before it falls. The presence of the lower tube makes the counter less vulnerable to temperature and ionic strength effects of the leachate. Counting of the drops can be easily achieved using any type of datalogger capable of logging electrical pulses.