2006年春季长江口砷形态分析及其生物有效性

Arsenic Speciation and Bioavailability in the Yangtze Estuary in Spring,2006

于2006年春季在长江河口开展野外调查,采集水和表层沉积物样品,并进行总砷、砷形态分析和生物有效性评估.将过滤水样用于测定溶解态砷含量,而未过滤水样经酸消解后用于测定总砷含量,两者之差则为颗粒态砷含量.结果表明,长江口青草沙水源地各层水体中总砷含量为0.88-1.35μg·L^-1（涨憩）,2.37-3.35μg·L^-1（落憩）.溶解态和颗粒态砷含量均随潮汐变化明显,各形态砷含量在落憩时均高于涨憩时,颗粒态砷所占总砷的比例也是落憩时明显高于涨憩时.以0.3 mol·L^-1磷酸溶液为萃取剂,在微波辅助下可以有效地将沉积物中砷酸盐[As（Ⅴ）]、亚砷酸盐[As（Ⅲ）]、一甲基胂酸盐（MMA）和二甲基胂酸盐（DMA）提取出来,然后利用高效液相色谱-氢化物发生-原子吸收光谱（HPLC-HG-AAS）联用技术进行检测.结果表明,长江口表层沉积物中总砷含量为6.3-30.7 mg·kg^-1,主要为无机砷形态,在江心沙洲及离岸沉积物中且以砷酸盐为主,而在近岸沉积物中以亚砷酸盐为主;利用醋酸纤维素/氧化铁复合膜方法（FeO/CAM）所得沉积物中有效砷含量占总砷含量0.6%-3.9%,平均约为2.1%,有效砷含量与总砷含量没有显著相关性,与亚砷酸盐含量呈显著正相关性,与砷酸盐含量呈显著负相关性.结果还表明,长江口南支沉积物中的砷形态分布特征及其生物有效性受城市支流输入和排污活动影响显著.

Field work was conducted in the Yangtze（Changjiang River） estuary in April,2006.Water and surface sediment samples were collected to analyze total arsenic and different arsenic species,and to assess the bioavailability.Water samples were filtered through 0.45 μm filter membrane to determine the concentrations of dissolved arsenic,while the unfiltered water samples were digested by acid to determine the concentrations of total arsenic,and the difference between them was the concentrations of particulate arsenic.It is showed that the concentrations of total arsenic varied from 0.88μg·L^-1o 1.35μg·L^-1t the slack of flood tide,and from 2.37μg·L^-1o 3.35μg·L^-1t the slack of ebb tide in water column of the Qingcaosha waters in the Yangtze estuary.The concentrations of both dissolved and particulate arsenic varied with the tide time.The concentrations of arsenic species at the slack of ebb tide were higher than those at the slack of flood tide,so did the percentage of particulate arsenic accounting for total arsenic.Phosphoric acid of 0.3mol·L^-1can effectively extract arsenate,arsenite,monomethylarsenate（MMA） and dimethylarsenite（DMA） from the sediments with the aid of microwave.The arsenic species in the extracts were detected by the hyphenated method of High Performance Liquid Chromatography-Hydrogenation-Atom Absorption Spectrometry（HPLC-HGAAS）.The concentrations of total arsenic in surface sediments varied between 6.3mg·kg^-1and 30.7mg·kg^-1which were mainly contributed by inorganic arsenic species.Arsenate was dominated in the sediments in the offshore waters while arsenite was dominated in the sediments in longshore waters.The concentrations of available arsenic in the sediments,which were estimated by the method of acetate cellulose composite membrane embedded with iron oxides（FeO/CAM）,accounted for 0.6% to 3.9%（averaged as 2.1%） of the total arsenic concentrations.The available arsenic concentrations had no significant correlation with the total arsenic concentrations,but had significant positive correlation with the arsenate concentrations and had significant negative correlation with the arsenite concentrations.The results also showed that the distribution of arsenic species in the sediments and their bioavailability in the South Branch of the Yangtze estuary were significantly influenced by the tributary river flows and effluents from the urban area.