a b s t r a c tThe speciation changes of antimony (Sb) in soil-plant system are largely unknown as compared with those of arsenic (As). In this study, indigenous plants and associated soils were sampled at the Xikuangshan Sb mine (XKS), China. The Sb in the soils (441-1472 mg/kg) were far greater than As (32-354 mg/kg), and the Sb and As availabilities in the soils, were 5.5% and 3.9% in average, respectively. HPLC-ICP-MS revealed the presence of four species of Sb in the soils and plants, including Sb III , Sb V , TMSb and UnkSb (unknown). The use of XANES revealed that the UnkSb consisted of inorganic Sb in the form of Sb V . Inorganic Sb were prevalent in the soil and plant samples at the eight sites, whereas TMSb was observed in only a few of the rhizosphere soils, and, in plants at a few of the sites, primarily in the leaves and to a lesser extent in the stems. Arsenic was detected in the soils primarily as inorganic forms, while, DMA was detected in high proportions in all of the plant tissues at all of the sites. The methylation of Sb was far less than that of As in the indigenous plants at XKS. The results suggest that As and Sb differ in transformation characteristics in the soil-plant system in XKS.

This study was conducted to develop a method for the simultaneous separation and detection of antimonite (Sb(III)), antimonate (Sb(V)) and trimethyl antinmony (TMSb) species in soils, using ultrasonic-aided citric acid extraction and high-performance liquid chromatography-inductively coupled plasma-mass spectrometry separation and detection. The extractions were performed using various chemical solutions. The separation was conducted on a PRP-X100 anion exchange column (25 cm × 4.1 mm i.d., 10 µm) using an isocratic elution program. The various factors of the elution procedure, e.g., pH, elution concentration and retention time, were optimized for the best separation of the three Sb species. It was found that two consecutive extractions using 100 mmol/L citric acid at pH 2.03 resulted in the highest extraction efficiency, 53%. The optimal elution procedure was obtained by using 200 mmol/L ammonium tartrate with 4% methanol as the mobile phase at pH 5.0. Under these conditions, the retention times for Sb(III), Sb(V) and TMSb species were 3.8, 2.1 and 6.8 min with detection limits of 0.03, 0.02 and 0.05 µg/L, respectively. Spiked recoveries for Sb(III), Sb(V) and TMSb ranged from 88 to 118%. The proposed method is reliable for antimony speciation in soil samples.