3. Results
Table 2 shows that HF-treatment increased the C content of the soils by a factor of 4.2–26.0 (average 12.1) and that carbon recovery on HF-treatment varied between 37% and 104% (average 67%). Diuron KOC values are also shown in Table 2 for both the whole soils and the HF-treated soils. From Fig. 1 it is apparent that corresponding KOC values for whole soils and HF-treated soils are only weakly correlated, a fact confirmed by linear regression (R = 0.26, p = 0.10). It is also clear that KOC is generally larger for the HF-treated soils ( Table 2 and Fig. 1). The average KOC value for the HF-treated soils is greater than that for the whole soils by a factor of 2.4 ( Table 2), although for individual soils this factor ranges from 0.9 to 19.5, with a mean value of 3.5 ( Table 2).