Study Of Enrichment Of Molybdenum From The Soils By Different Crops

The contents of molybdenum of the edible parts of 21 crops and the corresponding surface soils collected from different areas of Fujian Province were investigated.The main soil factors influencing the contents and the availability of Mo in the soils and the concentrations of the crops,the enrichment characteristics of Mo from the soils to the edible parts of the crops in the region were studied.The molybdenum contamination of the soils and crops was also evaluated.The environmental reference values of Mo in the soils were estimated on the base of the above results.The main results were as follows:1.The total Mo concentration of the soils ranged from 0.54 mg�kg-1 to 35.75 mg�kg-1 with a mean of 2.57 mg�kg-1.The total Mo content of nearly one-fifth of the soils exceeded the soil environment background value of Mo in Fujian province(3.7 mg�kg-1),indicating that these soils have been contaminated with Mo in varying degrees.The total soil Mo had significant and positive linear correlations with the contents of free iron oxide and available P of the soils while it had no significant correlation with the other soil properties.2.The available Mo contents of the soils were from 0.01 mg�kg-1 to 3.88 mg�kg-1 with an average of 0.36 mg�kg-1.The available degree of the soil Mo varied from 0.7%to 97.1%with a mean of 15.6%.The available Mo of the soils had significant and positive linear correlations with soil pH,the contents of free iron oxides and available phosphorus.The available degree of the soil Mo had significant and negatively correlated with the total soil Mo and silt content of the soils while significantly and positively correlated with the content of organic matter.3.The concentrations of Mo in the edible parts of crops(FW)ranged from not detected to 16.53 mg�kg-1 with a mean of 0.70 mg�kg-1.Legumes contained more Mo than the others.Cabbage vegetables and root crops contained less Mo than the others.On the whole,the Mo concentrations in the edible parts of all crops showed a significant and positive correlation with both the total and the available soil Mo.As for individual crops,the Mo contents of the edible parts of cowpea,peanut,celery,pakchoi and cabbage had significant and positive correlations with the total soil Mo,that of cowpea,peanut,pakchoi,celery,sweet pepper,haricot,lettuce and cabbage were significantly and positively correlated with the available Mo.The stepwise multiple regression analysis between the concentrations of Mo in the edible parts of crops and the soil properties,total soil Mo and the available Mo showed that the available soil Mo and the organic matter contents were the major factors affecting crop Mo content.4.The medians of the enrichment factors based on total Mo based and available soil Mo of the crops were between 0.002 and 1.156,and 0.024 to 4.873,respectively.The clustering analysis showed that legumes were the crops which had higher enrichment capacity.The enrichment factors of Mo based on total Mo and available Mo showed a curvilinear decrease with the increase of the total and available soil Mo.5.The molybdenum intake by 45 year-old male and female in this area are 97.87 ?g and 88.42 ?g,respectively if only the four kinds of crops are considered as Mo resources from daily diet.The health risk values were 0.28 and 0.25,respectively,indicating that there is no risk of Mo intake to human health from daily diet.6.The limit values of Mo for the soils were calculated based on the tolerable upper intake levels of Mo for adult in China.The calculated soil limit value of Mo were 9.13 mg�kg-1(total Mo)and 2.17 mg�kg-1(available Mo),respectively.