Environmental Biogeochemistry Charateristics Of Rare Earth Elements In Soil, Crop And Fish

The REEs contents in soils, and biological materials were measured by Instrumental Neutron Activation Analysis (INAA). The biogeochemical characteristics of REEs in soils, plants and soil– plant system were studied. For soil, the mean value of total REEs in soils of China is 176.8 mg/kg, the mean ratio of∑LREE/∑HREE in soils is only 8.0 and cerium accounts for 42% of the total REEs. The amount of the seven forms of the REEs follows the order: residual >> bound to organic matter > bound to Fe - Mn oxides > bound to carbonates >> exchangeable and water-soluble. For soil-plant system, the REEs contents in plant, especially in root, was marked related to the concentration in soil culture. The bioavailability of REEs in soils mainly depends on the exchangeable fraction of REEs that is strongly affected by the physico-chemical properties of soils. Long-term location test of foliage - dressing with"Changle"microfertilizer of REEs (net content of REEs 204g. Ha-1) does not affect contents and distribution patterns of REEs in the upper soil layer and mainly affects contents and distribution patterns of REEs in leaves during jointing age of wheat plant, but this does not affect those in stem and crust. Compared with control, no distinct accumulation effects of REEs in grains have been found.Contents of fifteen rare earth elements (REEs) in the seeds of sixty breeds of wheat collected from seed bank were measured by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The distribution patterns of contents of REEs in wheat seeds (n=58) were observed and compared with their average level in soils. Differences among regions and between spring and winter wheat were tested. Comparison with literature data was also made. The results show that the content of REEs in wheat seed ranges between 10-11 g·g-1 and 10-8 g·g-1, 3– 4 levels lower than that in soils. The distribution patterns are that light REEs are higher in contents and Eu-anomaly is slightly inadequate, similar to the soil case. No obvious differences were found among different regions and breeds. The data obtained in this study can accurately represent the contents of the fifteen REEs in wheat seeds.Four groups of field experiments that include REEs foliage dressing, soil dressing, triple amounts of soil dressing and control were carried out. Contents of REEs in wheat under different stages were measured by ICP-MS. The result show that REEs amount in leaf is significant increased with foliage dressing in jointing stage. It also shows accumulation with soil dressing method in jointing stage. Either using foliage dressing or soil dressing, there are no significant accumulation in mature stage. Comparison with two methods, lower amounts of REEs foliage dressing can be higher utilized than REEs soil dressing.Wheat samples under different application processes (soil dressing, foliage...