13 



ARSENIC (As 2 0 3 ) AT DIFFERENT DEPTHS IN SOIL IN 

 LYSIMETERS. 

 Soil No. 1 Soil No. 2 Soil No.3 



Not Not Not 



Depth leached Leached leached Leached Depth leached Leached 

 p. cent. p. cent. p. cent. p. cent. p. cent. p. cent. 



1-3 in. 



.280 



.224 



.450 



.237 



1-2 in. 



.97 



.95 



3-5 in. 



.198 



.211 



.170 



.092 



2-4 in. 



.50 



.47 



5-7 in. 



.171 



.145 



.118 



.092 



4-6 in. 



.00 



.00 



7-9 in. 



.184 



.170 



.013 











In the above table the first column represents the depths to 

 which samples were taken from soils 1 and 2. Soil No. 3 was 

 sampled at different depths as indicated in column 6. Apparently 

 the organic matter is most active toward arsenic as in the highly 

 organic soil (ISTo. 3) it was practically impossible to wash out the 

 arsenic. These data show the extent to which arsenic is held in 

 the soil by absorption and indicate the danger to be expected from 

 the accumulation of excessive applications. 



The tract of land which has been sprayed longest in these 

 islands is at Nahiku. Here the weeds have been kept down for the 

 last 5 years by three sprayings per year at the rate of 5 pounds per 

 acre per application. No plowing has been done and hence the 

 soil has remained undisturbed. During this time the rainfall has 

 amounted to about 200 inches per year, and the soil during this 

 time has been subjected to heavy washing. A large percentage of 

 the water has penetrated into the soil as the loss of water through 

 surface washing is very low in this district. Through the kind- 

 ness of Mr. Anderson samples were obtained from this district to 

 a depth of 12 inches, being taken every 4 inches. The first 4 

 inches contained .00924 per cent arsenic (As 2 0 3 ), the samples 

 below this depth contained none at all. This is entirely in accord 

 with the results obtained in the lysimeters. 



The nature of the reaction between the sodium arsenite and 

 the soil is apparently one of complex proportions. The greatest 

 activity is with the iron and humus and to a less extent the lime 

 and magnesia. A complete analysis of the filtrate collected from 

 the percolation experiments, using a solution containing 200 parts 

 per million arsenic, disclosed very little conclusive data. However, 

 the concentration was, in most instances, found to be greatest in 



