江苏王港盐沼的现代沉积速率

Contemporary Sedimentation Rates on Salt Marshes at Wanggang, Jiangsu, China

江苏海岸湿地总面积超过5000km,但围垦活动的加剧使盐沼湿地面积迅速减少;为了达到海岸防护、保滩促淤的目的,先后引种了大米草和互花米草。通过采集江苏王港潮滩盐沼湿地9处柱状样和挖取探槽剖面,以及对沉积剖面样品进行210Pb和137Cs测年分析,探讨了210Pb的本底及影响210Pb富集的因素,估算了王港盐沼湿地的现代沉积速率。王港潮滩盐沼沉积物对210Pb的吸附作用较弱;受风暴潮、生物扰动、物源变化及实验误差等因素的影响,在210Pbex剖面上出现了数据异常点,将这些数据点剔除后计算得到的沉积速率为3.3cmyr-1。137Cs测年显示,该地区1963年以来的平均沉积速率3.1cmyr-1,与210Pb法及前人研究结果相一致。根据一个典型剖面的137Cs测年数据分析,王港潮滩盐沼的沉积过程根据地貌特征的不同可分3个阶段,大米草覆盖阶段滩面高程迅速增加,互花米草的生长提高了滩面淤积速率。

The total area of coastal wetlands exceeds 5000 km2 in Jiangsu Province, China, but it has been decreasing rapidly as a result of intense reclamation activities. Two types of plants, Spartina angelica and Spartina alterniflora, were introduced successively into the Jiangsu coast, in order to protect the coastline from erosion and to increase the accumulation rate. 210Pb and 137Cs analyses were carried out for sediment samples from the salt marshes of Wangang, to derive the sedimentation rate, on the basis of an evaluation of the background values and factors affecting the enrichment of 210Pb. Analysis of a typical sediment column of the tidal flat shows that the absorption of 210Pb in the silt-dominated sediment is weak. Influences of storm events, bioturbation, material sources and analytical error also have an effect. As a result, some abnormal data points are present. These data were removed before the calculation of the sedimentation rate. The sedimentation rate was 3.3 cm a-1 on average. Based upon analysis of the 137Cs dating, the rate since 1963 was 3.1 cm a-1 on average, similar to the data by 210Pb dating and from previous studies.