Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology, Higashi 1-1-1, Tsukuba, Ibaraki, 305-8567, Japan.
Geological Survey of Hokkaido, Environmental and Geological Research Department, Hokkaido Research Organization, Kita 19 Nishi 11, Kita-ku, Sapporo, Hokkaido, 060-0819, Japan.
Environ Sci Pollut Res Int. 2018 Jun;25(16):15680-15691. doi: 10.1007/s11356-018-1779-7. Epub 2018 Mar 25.
The stability and dispersion of naturally occurring As have been receiving increasing attention, because As is toxic and its contamination is a widespread problem in many countries. This study investigated As fractionation and speciation in organic sediments collected from different depositional settings to elucidate the existence of stable As in humic substances. Eleven organic sediment samples were collected from marine and terrestrial alluvial regions in Hokkaido prefecture, Japan, and the chemical fraction of As and species of humic substances were identified by sequential extraction. In addition, stable As bound in organic matter was evaluated by FT-IR spectroscopy. The As fraction mainly comprised inorganic substances, especially sulfur, iron, and manganese, and terrestrial sediments (lacustrine and inland deposits) were rich in sulfides and Fe and Al (hydr)oxides. When the residual fraction was excluded, the organic fraction of As was higher in seawater sediments than in terrestrial sediments. Among humic substances, cellulose, humic acid, and hydrophilic fulvic acid were clearly associated with As accumulation, and As speciation showed that the As was of organic origin. Cellulose, an organic compound of plant origin, was abundant in As=S and As (III)=O bonds, and As accumulation was higher in sulfur-rich peat sediments, corresponding with the physiological activities of As in plants. Hydrophilic fulvic acid and humic acid in these sediments, originating from small animals and microorganisms in addition to plants, denote higher As contents and abound in As (III, V)=C and C-H, CH bonds even in sulfur-rich sediments. The methylated As bonds reflect the ecological transition of organisms.
自然存在的砷的稳定性和分散性越来越受到关注，因为砷是有毒的，其污染是许多国家普遍存在的问题。本研究调查了从不同沉积环境中采集的有机沉积物中砷的形态和形态，以阐明腐殖质中稳定砷的存在。从日本北海道的海洋和陆地冲积地区收集了 11 个有机沉积物样品，并通过连续提取法确定了砷的化学形态和腐殖质的形态。此外，还通过傅里叶变换红外光谱法评估了稳定结合在有机物中的砷。砷的形态主要包括无机物质，特别是硫、铁和锰，陆地沉积物（湖泊和内陆沉积物）富含硫化物和铁、铝（水合）氧化物。当排除残留部分时，海水沉积物中的有机砷形态高于陆地沉积物。在腐殖质中，纤维素、腐殖酸和亲水性富里酸与砷的积累明显相关，砷的形态表明砷具有有机来源。纤维素是一种植物来源的有机化合物，富含 As-S 和 As(III)-O 键，富含有机硫的泥炭沉积物中砷的积累量较高，这与植物中砷的生理活性相对应。这些沉积物中的亲水性富里酸和腐殖酸除了来自植物之外，还来自小动物和微生物，这表明它们含有更高的砷含量，并富含 As(III、V)=C 和 C-H、CH 键，即使在富硫沉积物中也是如此。甲基化砷键反映了生物体的生态转变。
