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Monitoring of Water and Solute Transport in the Vadose Zone


Soils and the groundwater are increasingly contaminated by agrochemicals (such as fertilizers, pesticides), heavy metals, pathogenic microbes, hormones and pharmaceuticals from livestock production. Above ground land use and land cover change, especially deforestation and fallow agricultural land during winters can increase the amount of runoff, soil erosion and leaching of excess nutrients. Soil water in the vadose zone is an important source of groundwater, which can potentially change water chemistry of groundwater as well as water in streams. Therefore, it is important to monitor soil solution to better understand the movement and fate of contaminants through the vadose zone. A recent paper in Vadose Zone Journal provides a review of various soil-solution samplers and provide criteria for selection and use of soil-solution samplers. In this paper, more than 300 journal articles are classified on the basis of soil-solution sampler type, soil type, land use land cover, and analytes measured. The soil-solution samplers reviewed in this paper are: drainage lysimeters, pan lysimeters, resin bags/membranes, wick lysimeters and suction cups samplers and suction plate samplers.

The lysimeters have been used for the past 300 years to measure evapotranspiration, excess nutrient and contaminant leaching or leaching from landfills and for understanding soil water movement in the vadose zone. There are different types of soil-solution samplers but most widely used are drainage lysimeters and ceramic suction cup samplers. Many modifications in the design of soil-solution samplers have been proposed and tested which are reviewed in this paper. Selection of appropriate soil-solution sampler depends on a number of factors which are discussed in details and the relative importance of each factor depends on individual research objectives. The soil-solution can be sampled to monitor pH, electrical conductivity, cations and trace elements and cations (such as Ca, Mg, Na, K) and anions (NO3-, NO2-, PO43-, F, SO42-). In addition, these soil-solution samplers can also be used to monitor isotopes, dissolved organic carbon, pesticides, soil colloids, and microorganisms. 

Read the full open access paper in Vadose Zone Journal

Preview image from Wikimedia Commons, by Giancarlo Dessì