UI ^± I SJ J U 



to the tolerance of plants to cadmium. Considerable variation in 

 cadmium accumulation has been demonstrated for many vegetable and 

 grain crops grown on the same soil (Davis 1984). 



In recent years interest in cadmium in soils and plants has 

 intensified because of its presence in sewage sludge. This aspect 

 has been the subject of much research and several reviews (Hansen 

 and Chaney 1984, Logan and Chaney 1983, Sommers 1980, Singh 1981, 

 Standish 1981, Webber et al . 1983, Williams 1982, Rundle et al. 

 1984, Page 1974, Page et al . 1983, and Lutrick et al . 1982). Land 

 application of sludge may potentially cause phytotoxici ty pro- 

 blems, but of greater concern is the high potential for introduc- 

 tion of cadmium into the food chain, where it may create health 

 hazards (Nriagu 1980). A summary of many scientific studies of 

 plant uptake of soil cadmium is presented in Tables 36, 37 and 38. 



3.2.2 Cadmium in soils 



3.2.2.1 Total cadmium in soil 



A total soil cadmium hazard level of 100 ppm was selected for 

 the Helena Valley based on two major factors: 1) all total soil 

 cadmium concentrations greater than 100 ppm found in the reviewed 

 literature were associated with yield reductions regardless of 

 plant type, and 2) the lack of and variability of data, especially 

 with respect to higher pH levels (6-7), in the total soil cadmium 

 range of 40 to 100 ppm (Table 36). Other phytotoxic total soil 

 cadmium criteria reported in the literature ranged from 3 to 8 ppm 

 (Melsted 1973, Linzon 1978). However, nonsignificant or no yield 

 reductions were reported for several plant species at 40 ppm total 

 soil cadmium (John 1973). Data of Khan and Frankland (1984) 

 suggested highly significant yield reductions occur in the biomass 

 of wheat, oat and radish roots at 50 ppm total soil cadmium. 



Available data may support a lower (50 ppm) total soil 

 cadmium phytotoxic hazard level than the 100 ppm level selected 

 for the Helena Valley (Table 36). It is imperative that persons 

 applying this hazard level be cognizant of the high concentrations 



90 



