武汉东湖沉积物孔隙度与含水量

Porosity and Water Content of Sediments in Lake Donghu,Wuhan

对采自武汉东湖Ⅰ站、Ⅱ站的沉积物采用一种新的方法计算孔隙度:拍摄扫描式电子显微镜(SEM)图像,采用局部区域阈值化的方法对图像进行阈值化(thresholding)处理,运用自编程序求出孔隙度的垂直变化.结合含水量的垂直变化,分析孔隙度与含水量之间的关系,并对影响它们垂直变化的因素进行了讨论.结果表明:SEM图像局部区域阈值化法是研究沉积物孔隙度的有效方法;孔隙度与含水量表层较大,从表层到底层呈明显的下降趋势;孔隙度(K)与含水量穴H雪有比较好的正相关.运用拟合的相关方程式,可以由较易获得的东湖Ⅰ站和Ⅱ站的含水量反推较难获得的孔隙度.

Two undisturbed sediment cores of95cm and150cm at the StationⅠandⅡin Lake Donghu,Wuhan,were collected respectively.A new method was used to calculate the samples'porosity with the following pro-cedures:the images of the samples were taken in scanning electron microscope(SEM);thresholding of the images were taken by the selection method for local threshold;and the variations of porosity and water con-tent with the depth were analysised by the self-made program.Furthermore,the factors that affect the varia-tions of porosity and water content with the depth were discussed.The relationship of porosity with water content was studied as well.The results show that:(1)SEM images local thresholding method was a new feasible and effective method of researching sedi-ments'porosity.The results were reliable.(2)At StationⅠand StationⅡin Lake Donghu,sediment porosity fluctuated greatly in the surface layer due to water disturbance.Reduction of sediment porosity with depth was the results of decrease of the or-ganic matter(OM)content and disturbance and increase of the gravitational compaction.Gravitational com-paction was modelled by an logarithm equation that gave the sediment porosity as a function of burial depth.The variations of the sediment porosity with depth were modelled by logarithm equations.(3)In the surface layer,the water content exhibited an abrupt decrease with depth due to the decrease of bio-perturbation and organic matter content(OM).Under gravitational compaction,the water content exhibited an obvious decrease with depth from surface layer to substrate.(4)Porosity(K)was well correlated with water content(H),and they were both in positive correlation.The correlation equations were:H 1 =7.3571×K 1 -240.60(r=0.80);H 2 =2.65×K 2 -55.07(r=0.84).Using the equations,we could calculate porosity of the sediments at StationⅠand StationⅡin Lake Donghu,which can not be easily made,from water content that can be easily obtained.