近海沉积物中铁锰水合氧化物结合态金属元素的提取研究

Study on the Extraction Method of Metal Elements Bound to Iron and Manganese Oxyhydroxides in Coastal Marine Sediments

铁锰水合氧化物结合态金属是沉积物中的易还原形态,具有化学活性。在水体的氧化还原条件发生变化时,会释放到水体当中,造成二次污染,对海洋环境和生物有潜在的风险。为了较准确地了解铁锰水合氧化物结合态中金属元素的含量,选择胶州湾、青岛近海以及南黄海7个站的表层沉积物用盐酸羟胺进行连续提取,对其中铁锰水合氧化物结合态的提取和测定条件进行了实验,优化了近海表层沉积物中铁锰水合氧化物结合态的提取方法。结果表明,NH2OH·HCl的浓度基本不影响提取结果;连续振荡条件下的提取平衡时间约在4h且基本提取完全;提取过程中有轻微过度溶出现象,可采用重复提取的方法校正;连续振荡与间歇振荡对提取结果没有显著影响。沉积物铁锰水合氧化物结合态金属元素的适宜提取条件确定为,采用0.04mol/L NH2OH·HCl-0.02mol/L HNO3作为提取剂,室温下连续振荡2次提取,第1次为4h,第2次为1h可用于过度溶出校正。

Metal elements bound to iron and manganese oxyhydroxides are easily reducible fraction of metals in marine sediments. As a reactive chemical form in sediment, these metals are easily released into the water during the redox condition changes and thus cause the secondary pollution of heavy metals. In order to determine the contents of metals bound to Fe-Mn oxyhydroxides, seven surface sediments from the Jiaozhou Bay, the coastal area near to Qingdao city and the South Yellow Sea were subjected to the experiment to optimize the extraction conditions with hydroxylamine hydrochloride. The experiment showed the concentration of hydroxylamine hydrochloride had little influence on the extraction results. The equilibration time was 4 hours under continuous oscillation. Slight excessive dissolution from aluminosilicate may occur during the extraction, which can be corrected with the second leaching. The appropriate extraction conditions of the method were suggested as follows= 0.04 mol/L NH2OH · HCl-0.02 mol/L HNOa is used as the extracting reagent under continuous oscillation at room temperature for 4 hours for the first extraction and 1 hour for the second extraction to correct the excessive dissolution.