CIRCULATION OF HEAT, SALT AND WATER 

 IN SALT MARSH SOIL 



by 



Alfred C. Redfield 

 Woods Hole Oceanographic Institution 



The annual cycle of temperature in salt marsli peat has been measured 

 to determine whether water moves through the soil fast enough to disturb the 

 predictable relations expected if the water is stagnant. 



The distribution of temperature in a solid of uniform composition, when 

 subject to a sinusoidal change in temperature at the surface is given by (Joos 

 1934): 



6/ = e''^'^^^^''' cos co(t--^==^) 



where Q = difference between recorded and average temperature 



= maximum value of ©at the surface 



t = time since _,a occurred 



X - depth below surface 



CO = angular frequency (2 fT/period) 



m - thermal diffusivity 



The predicted relations are shown in Figures 13 and 14 which indicate con- 

 venient methods of deriving the diffusivity, m, from experimental data. When 

 plotted as in Figure 14 the attenuation of the thermal wave is given by the en- 

 velope of maximum or minimum temperatures and is described by the expo- 

 nential term. When plotted as in Figurel3 the line describing the change in 

 depth with time of the average temperature { Q — O ) has a slope equal to the 

 wave velocity «r = Jztntt). Thus either term may be used independently to de- 

 termine the diffusivity of the material. 



Measurements made in the marsh at Barnstable 100 yards from the high 

 land where 4.5 meters of relatively homogeneous peat occurred conformed 

 approximately to the predicted pattern shown in Figures 13andl4. Prelimin- 

 ary estimates of the value of v and m are given in Table 1 together with their 

 accepted values for water. Determination of the density, specific heat, and 

 water content of the peat indicate that the interstitial water in the marsh if 

 stagnant would yield values about ZO percent less than that of pure water. 



77 



