摘要:
2005年4~10月,对长江口崇明东滩潮间带高潮滩站位沉积物间隙水中营养盐成分进行了每月一次的连续观测。结果表明,该站点间隙水中营养盐NH4+和S iO32-的浓度一般在200~400μmol/L之间;NO2-+NO3-以及PO43-浓度一般在1μmol/L以下,但9月份后的3次采样得到的沉积柱表层(0~10 cm)NO2-+NO3-浓度则一般超过10μmol/L,甚至接近100μmol/L。沉积物中有机N含量以及受粘土矿物含量影响的蛋白石(BS i)的溶解度是决定间隙水中NH4+和S iO32-的浓度的主要因素。间隙水中S iO32-浓度和温度之间存在着显著的正相关关系(P<0.01),说明其主要是受温度影响的溶解过程的控制;而NH4+浓度与温度之间没有明显的相关关系,说明与S iO32-相比,沉积物中NH4+产出的控制因素较为复杂。我们采用了经典的早期成岩方程对NH4+和S iO32-浓度剖面进行了数学模拟,在模型中考虑了扩散作用、埋藏作用以及营养盐的代谢作用等因素。模拟结果表明,通过改变扩散项系数基本可以模拟出营养盐剖面中间浓度高、上下浓度低的总体趋势。此外,沉积速率和代谢反应速率也在不同程度上对模拟结果产生影响。
Abstract:
Distribution of NH+4 and SiO2-3, the dominant nutrient species, in pore water of the sediments at Dongtan, Chongming has been determined once a month from April to October, 2005. Compared with the data of other study areas, our results indicate that the particulate N contents and the opal (BSi) solubility, influenced by the clay of terrestrial origin, are the main reason controlling the NH+4 and SiO2-3 concentrations. Also, these data reveal that the temperature can draw its positive effect on SiO2-3 concentration in pore water, but no apparent relationship is observed between temperature and NH+4 concentration. In the next part of the study, a steady state, coupled, non-linear model for early diagenesis has been induced to reproduce the NH+4 and SiO2-3 nutrient profiles in pore water. The diffusion, sedimentation and metabolic reaction are included in the model equations. The model profiles can match well with pore water nutrient profiles by altering the diffusive coefficient (D). Moreover, the sedimentary rate (ω) and reaction parameters (ks and kn) can also have their significant impacts on the model results.
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