A Soil Water Extractor That Minimizes CO₂ Degassing and pH Errors

Soil water extractors that are presently used to sample the unsaturated zone cause substantial CO 2 degassing within the sampler. The resultant p H errors are sufficiently large that the measured p H values are unacceptable for determining specific mineralogic controls on solution composition. The p H increases can also result in oxide and carbonate precipitation within the extractor thereby altering solution composition. The soil water samplers described here reduce CO 2 degassing by minimizing the gas‐liquid ratio in the extractor and by flushing several volumes of solution through the liquid‐filled sampling container before a sample is removed. The construction of both shallow and deep samplers is described.