Arsenic Toxicity Studies— Clements and Munson 
159 
TABLE 4 TOMATO 
Data for the accumulation of arsenic (as ppm 
AS2O3) AND PHOSPHORUS (AS PER CENT OF DRY 
WEIGHT), OF PLANTS GROWN IN SOLUTIONS CON¬ 
TAINING VARIOUS INCREMENTS OF TRIVALENT AR¬ 
SENIC (AS SODIUM ARSENITE) AT DIFFERENT PHOS¬ 
PHORUS LEVELS. 
ARSENIC 
IN 
SOLUTION 
DRY 
WEIGHT 
ARSENIC 
IN 
PLANT 
PHOS¬ 
PHORUS 
IN PLANT 
ppm AS2O3 
gm. 
ppm AS2O3 
% dry wt. 
Low phosphorus level (P 10 ppm) 
0.00 
29 
trace 
0.66 
.25 
30 
trace 
.67 
.50 
31 
trace 
.69 
.75 
30 
trace 
.66 
1.00 
28 
1.6 
.77 
1.75 
26 
1.3 
.76 
2.50 
20 
3.9 
.78 
3.25 
10 
4.7 
.70 
4.00 
9 
10.9 
.81 
5.00 
4 
12.0 
.81 
Medium phosphorus level (P = 
60 ppm) 
0.00 
32 
trace 
.75 
1.00 
29 
trace 
.77 
2.00 
24 
3.3 
.75 
3.25 
9 
6.7 
.84 
7.00 
1 
12.5 
.69 
11.00 
1 
24.1 
.50 
High phosphorus 
level (P rr 120 ppm) 
0.00 
33 
trace 
.85 
1.00 
28 
trace 
.88 
3.25 
7 
7.8 
.88 
7.25 
3 
14.7 
.84 
of phosphorus on the absorption of trivalent 
arsenic is quite different from its action on 
pentavalent arsenic. From a given concen¬ 
tration of trivalent arsenic, the tomato plants 
absorbed approximately the same amount of 
the toxic element, irrespective of the phos¬ 
phorus level, and showed equal degrees of 
injury. In the studies with Sudan grass, the 
medium- and the high-phosphorus levels 
reduced the absorption of arsenic over that 
absorbed from the low level of phosphorus, 
with a corresponding reduction in injury. 
In the studies with the bean plants, the phos¬ 
phorus level had some effect on the absorp¬ 
tion of arsenic as shown in the analysis of 
the plant material, although it should be 
noted that the differences are so small as to 
be insignificant. 
These studies reveal, therefore, that the 
form in which the arsenic occurs is an im¬ 
portant factor in determining the effect of 
phosphorus. Hurd-Karrer (1937) in her 
studies on the antagonism of related ions 
found that sulfates more effectively reduced 
the absorption of selenium from selenates 
than from selenites. From these results she 
suggested that "by analogy, phosphates 
would be expected to have less effect on the 
toxicity of arsenite than on that of arsenate" 
(1939). The studies reported in this paper 
confirm that supposition. 
Part III. Toxic Levels of Arsenic 
in Certain Hawaiian Soils 
It is well known that arsenicals, when ap¬ 
plied to soil, are far less available to plants 
TABLE 5. SUDAN GRASS 
Data for the accumulation of arsenic (as ppm 
AS2O3) and phosphorus (as per cent of dry 
weight), of plants grown in solutions con¬ 
taining VARIOUS INCREMENTS OF TRIVALENT AR¬ 
SENIC (as sodium arsenite) at different phos¬ 
phorus LEVELS. 
ARSENIC 
IN 
SOLUTION 
DRY 
WEIGHT 
ARSENIC 
IN 
PLANT 
PHOS¬ 
PHORUS 
IN PLANT 
ppm AS2O3 
gm. 
ppm AS2O3 
% dry wt. 
Low 
phosphorus 
level (P = 10 ppm) 
0.00 
63 
trace 
0.44 
.25 
63 
5.2 
.36 
.50 
48 
7.8 
.59 
.75 
48 
11.9 
.45 
1.00 
32 
18.6 
.56 
1.75 
17 
20.7 
.56 
2.50 
5 
23.1 
.73 
3.25 
4 
22.7 
.48 
4.00 
2 
42.5 
.55 
5.00 
3 
46.9 
.88 
Medium phosphorus level (P =£ 
60 ppm) 
0.00 
63 
trace 
.94 
1.00 
39 
8.6 
.58 
2.00 
24 
10.9 
.53 
3.25 
4 
14.9 
.56 
7.00 
3 
27.5 
.67 
11.00 
2 
91.2 
.81 
High phosphorus 
level (P = 120 ppm) 
0.00 
68 
trace 
.98 
1.00 
45 
4.1 
.88 
3.25 
18 
12.8 
.99 
7.50 
8 
32.5 
.77 
15.00 
2 
87.5 
.81 
