西南极海碘的早期成岩作用和生物地球化学

EARLY DIAGENESIS AND BIOGEOCHEMISTRY OF IODINE IN WEST ANTARCTIC OCEAN

于1984—1985年南极夏季(12—2月),对南极半岛西部海域进行了多学科综合考察,获得27个表层(抓斗)沉积物和两个剖面样(箱式)的地球化学资料。从测区碘的成岩分布中,我们追索到某些与碘的早期成岩和生物地球化学有关的双向过程记录。碘的含量分布依赖于生源物质,生源碘的再生产主要发生在成岩早期,其再生产过程与沉积有机氮的释放密切相关。测区两个剖面样20cm以浅,碘含量降低幅度可达50％(M1)和36％(R2),M1站的平均再生产速率估算为2.3×10^(-2)μg/(g·a)。间隙水碘含量对埋藏时间作图的表观直线性,提出了上述沉积剖面早期成岩生源碘再生产中扩散释放的零级动力学方程: I^-=180+21T(M1),I^-=142+28T(R2)它们回归海水生物地球化学循环体系的通量分别为: F_(M1)=-5.8×10^(-7)μg/(cm^2·s),F_(R2)=-8.3×10^(-7)μg/(cm^2·s)早期成岩环境的酸碱度、碳酸盐平衡体系和氧化还原条件对生源碘的再生产释放有较大影响,碱性和还原条件有利于碘的释放。

During the First Chinese Antarctic Ocen Exploration from December 1984 to February 1985, 27 grab samples and 2 box samples were obtained. With tracing to the diagenetic distribution of iodine, some records relative to the reversible processes of early diagenesis and biogeochemis-try of iodine are obtained in this paper. The distribution of iodine depends on biogenic materials, and thus the regeneration of bioiodine mainly occurs in early diagenesis. Furthermore, its regeneration process is closely correlated with the release of sedimentary organic nitrogen. The decrease of iodine contents can be down to 50% (Ml) and 36% (R2) within the depth of the two twenty centimeter sediment cores. The estimated rate of iodine regeneration is 2.3×10-2μg/(g·a) in average (Ml). Linearity of iodine contents vs. buried time suggested the zero order dynamic equation which reveals the diffusion and release process of bioiodine in the regeneration during early diagenesis:I-= 180 + 21T(M1), I-= 142 + 28T(R2)The diffusion fluxes of iodine returned to the aquatic biogeochemical system are: FM1 = 5.8×10-7μg/(cm2·s), FR2 = 8.3×10-7μg/(cm2·s)It shows potential significant effects of pH, carbonate balance and redox conditions on the regeneration release of bioiodine; both basic or reductive condition will facilitated the release of iodine from sediments in early diageuetic environment.