Study of soil-to-plant transfer factors (TFs) of 226Ra, 232Th, and 40K on plants cultivated on ex-tin mining land in Bangka Belitung, Indonesia.

Soil-to-plant transfer factors (TFs) are of fundamental importance in measuring the environmental impact due to the presence of radioactivity in soil and agricultural crops. The present study thus to measure soil-to-plant TFs of 226Ra, 232Th, and 40K on horticultural plants cultivated on ex-tin mining land in Bangka Belitung islands. There were 21 samples of 15 species and 13 families from 17 locations comprising four vegetables species, five fruits species, three staple foods species, and three others. The TFs were measured in leaves, fruit, cereal, kernel, shoot, or rhizome. The results showed that 238U and 137Cs were almost not found in plants, whereas 226Ra, 232Th, and 40K were measured. In soursop leaf, common pepper leaf, and cassava peel, on 226Ra, the TFs for the non-edible parts, (0.42 ± 0.02; 1.05 ± 0.17; 0.32 ± 0.01 respectively) were significantly higher than soursop fruit, common pepper seed, and cassava root for the edible parts (0.01 ± 0.005; 0.29 ± 0.09; 0.04 ± 0.02 respectively).

Soils on exposed Sunda shelf shaped biogeographic patterns in the equatorial forests of Southeast Asia.

The marked biogeographic difference between western (Malay Peninsula and Sumatra) and eastern (Borneo) Sundaland is surprising given the long time that these areas have formed a single landmass. A dispersal barrier in the form of a dry savanna corridor during glacial maxima has been proposed to explain this disparity. However, the short duration of these dry savanna conditions make it an unlikely sole cause for the biogeographic pattern. An additional explanation might be related to the coarse sandy soils of central Sundaland. To test these two nonexclusive hypotheses, we performed a floristic cluster analysis based on 111 tree inventories from Peninsular Malaysia, Sumatra, and Borneo. We then identified the indicator genera for clusters that crossed the central Sundaland biogeographic boundary and those that did not cross and tested whether drought and coarse-soil tolerance of the indicator genera differed between them. We found 11 terminal floristic clusters, 10 occurring in Borneo, 5 in Sumatra, and 3 in Peninsular Malaysia. Indicator taxa of clusters that occurred across Sundaland had significantly higher coarse-soil tolerance than did those from clusters that occurred east or west of central Sundaland. For drought tolerance, no such pattern was detected. These results strongly suggest that exposed sandy sea-bed soils acted as a dispersal barrier in central Sundaland. However, we could not confirm the presence of a savanna corridor. This finding makes it clear that proposed biogeographic explanations for plant and animal distributions within Sundaland, including possible migration routes for early humans, need to be reevaluated.