Environmental Management Science

Project (EMSP) Strategic Plan for

Deployment

Dot. Pierwiastków promieniotwórczych: metoda wykrywania małych ilości

Physical methods for assessing moisture flux in arid soils are inadequate. Chemical and isotopic

tracers such as chlorine and 36Cl, that move conservatively with the moisture and therefore define

flux by their distribution over time are preferred. Allison et al. (1994), in a review of available

techniques for measuring moisture flux in the unsaturated zone, have pointed out that

"[w]hen recharge rates are only a few millimeters per year or less, chemical and isotopic methods are likely to be more successful than physical methods, such as water balance methods, which rely on measured or estimated values of water flux....An advantage of tracers is that they integrate all of the processes that combine to affect water flow in the unsaturated zone."

The most important tracers discussed by Allison et al. (1994) are chlorine and 36Cl. A field scale tracer is also valuable because laboratory experiments are extremely difficult for dry soils. While soil column experiments are often conducted, there has been a growing realization that centrifugal devices are required to adequately simulate unsaturated moisture flow. However, these small devices are inadequate to assess field-scale phenomenon, such as lateral heterogeneity or preferential flow

due to soil structure

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