Abstract:

In order to investigate speciation of rare-earth elements (REEs) in soils, contents of REEs in surface of soils and navel oranges collected from rare-earth mining area in southern Jiangxi, China, were determined. Soil samples were sequentially digested with HNO3-HF-HClO4 and microwave oven. Contents of fifteen REEs in samples were determined with inductively coupled plasma mass spectrometry (ICP-MS). The characterization of REEs in soils was further investigated to identify speciation. Results indicated that contents of REEs in orange-growing soils around rare-earth mining area were obviously higher than those in soils far away rare-earth mining area. An ion-adsorption type ore enriched in heavy REEs was observed in orangegrowing soils around mining area. Large amount of REEs in orange-growing soils were in oxidative and reducible states, which reached 61.6% and 31.9% of total amount, respectively. While contents of REEs in soils existed as acid-soluble and residual states were 4.4% and 1.98%, respectively, suggesting that REEs in orange-growing soils around rare-earth mining area were relatively stable and exhibited a lower bioavailability. The total content of REEs in navel oranges grown in soils around mining area was 0.215 mg/kg, and much lower than the maximum limit level (≤0.7 mg/kg) of contaminants in foods issued in China (GB 2762— 2005). All of these investigations also provided the information that navel orange grown in soils around rare-earth mining area had no harmful to human health.

Key words: rare-earth elements (REEs), navel orange, orange-growing soil, inductively coupled plasma mass spectrometry (ICP-MS)