TREATMENTS FOR FARMLAND CONTAMINATED WITH RADIOACTIVE MATERIAL 



13 



Large moldboard or disk plows are available in 

 limited numbere. Some of these plows might not 

 give efficient burial of contaminated soil (15). 

 The uptake of radioactivity is much less when 

 sodium carbonate is placed on the contaminated 

 soil before deep plowing. 



Feasibility ratings for plowing treatments are 

 summarized in table 4. Plowing to 7 or 12 inches 

 deep could be carried out with common farm 

 plows, but it has little effect on uptake of radio- 

 active strontium. If the hazard were from ex- 

 ternal gamma radiation from uptake of radio- 

 activity into plants, plowing would reduce the 

 hazard very greatly. Plowing 36 inches deep re- 

 quires special machinery, and the effects on stron- 

 tium uptake may vary greatly with different soils 

 and crops. Only by using some material or tech- 

 nique to stop root growth into the contaminated 

 soil volume can a highly effective reduction in 

 uptake be achieved. 



The effort required for plowing increases 

 sharply with increasing depth of plowing. Two 

 large crawler tractors were required to pull the 

 plow 36 inches deep in Pullman silty clay loam 

 (12). About one acre was plowed per hour of 

 operating time. Two tractor drivers and one man 

 at the controls of the plow were used. During 

 large field operations, the rear tractor driver 

 could possibly control the plow. However, it was 

 convenient to station an extra man on the front 

 tractor to warn its driver in case of equipment 

 breakdown. Thus, from 2 to 4 man-hours were 

 required per acre plowed. 



Many soils would produce poor crops after 

 deep plowing. This could result from low fertility, 

 high acidity, soluble salts, or poor texture or 

 structure of the soil brought to the surface. Fer- 

 tility and acidity problems could be corrected by 

 mixing fertilizers and lime into the new topsoil. 

 Correcting poor soil structure is more difficult 

 since it may require large additions of sand, com- 

 post, or manure, and long periods of time for the 

 improvement of structure. These measures would 

 add to the already great effort of deep plowing. 

 Soils with deep, fertile subsoils would be most 

 likely to produce good crops after deep plowing. 

 Some impervious soils are benefited by improved 

 water infiltration after deep plowing (30, 32) . 



Irrigation and Leaching 



The effectiveness, effort, and productivity rat- 

 ings of irrigation and leaching treatments for 

 contaminated land are listed in table 4. Irrigation 

 does not reduce uptake of radioactive strontium. 

 Leaching removes little radioactive strontium 

 from the soil profile unless large quantities of 

 chemicals are added to increase the movement of 

 strontium. Therefore, irrigation and leaching 

 would not be feasible treatments for contami- 

 nated soils, even though little extra effort might 

 be needed in some irrigated areas to change the 

 frequency of irrigation or to leach with large 

 amounts of water. Soil productivity would be 

 lowered by leaching because essential nutrient 

 elements would be removed with the strontium. 



Applications of Lime, Fertilizers, 

 and Other Soil Amendments 



The effectiveness, effort, and productivity 

 ratings of various soil amendments are also given 

 in table 4. Unfortunately, none of the soil amend- 

 ments are highly effective in reducing uptake of 

 radioactive strontium. Large applications of 

 ammonium or potassium phosphates and, on very 

 acid soils, the application of lime, will reduce the 

 uptake of radioactive strontium by 75 percent. 

 With lime, this is about the maximum reduction 

 that can be achieved, and it has been observed 

 only on soils that were initially very low in ex- 

 changeable calcium. With the phosphates, re- 

 ductions in the range of 75 to 95 percent have 

 been observed on a number of soil types in the 

 greenhouse, but phosphates are much less readily 

 obtainable than lime, and detrimental effects on 

 plant growth liave been observed. Field tests have 

 not been made with the phosphates. 



Applications of soil amendments could be made 

 more easily than most other treatments for con- 

 taminated land. They would be limited mainly 

 by the availability of the materials, the effort 

 required to spread them on the land, and response 

 of the soil to the amendment. Optimum use of 

 lime and fertilizers for economic crop production 

 gives nearly as much reduction in radiostrontium 

 uptake as can be achieved with heavier applica- 

 tions of these materials. 



