闽江福州段沉积物中多环芳烃的空间分布异质性研究

多环芳烃(PAHs)是环境中一类典型的持久性有机污染物,为探明PAHs在闽江福州段沉积物中的空间分布规律,采用传统统计学和地统计学相结合的方法对PAHs的空间异质性进行了研究.结果表明,PAHs含量变异系数(CV)在39%～90%之间,属于中等强度变异.3环PAHs含量的块金值与基台值之比C0/(C+C0)]为0.307,具有中等强度的空间相关性,其余不同环数PAHs以及PAHs总量的C0/(C+C0)值都小于0.25,具有强烈的空间相关性.低环PAHs的分维数D值高于高环PAHs,空间异质性较高.3环及3环以上PAHs的Moran’s I系数随距离的增大而下降,且在0～25.0 km之间其空间自相关性随间隔距离的增大而减弱;而Moran’s I系数分析结果进一步说明了2环PAHs的空间变异特征的复杂性.受到水流影响,PAHs含量在南-北方向的半方差函数值与其它方向有所不同,但在东北-西南、东南-西北和东-西方向上的半方差函数值重合性较好,近似各向同性.用交叉验证法检验的结果表明,普通克里插值法能够很好地预测闽江福州段沉积物中PAHs的空间分布情况,PAHs含量沿水流流向大致呈下降的趋势.

Spatial Heterogeneity and Autocorrelation of Polycyclic Aromatic Hydrocarbons in the Sediment of Minjiang River in Fuzhou City

Polycyclic aromatic hydrocarbons (PAHs) are a typical persistent organic pollutants in environment. In order to explore the spatial distribution pattern of PAHs in the sediment of Minjiang River in Fuzhou City, the spatial heterogeneity analyses of PAHs in the sediment were studied with traditional statistics and geostatistics. The results showed that the variation degree of PAHs concentrations was moderate, the coefficient of variations (CV) ranged from 39% to 90%. The nugget/sill ratio of 3-ring PAH concentration was 0.307, which indicated a moderate spatial correlation, while the nugget/sill ratios of other PAHs were less than 0.25, which indicated strongly spatial correlations. The fractal dimension values and Moran's I values indicated that the spatial heterogeneity of lower-ring PAHs was stronger than those of high-ring PAHs. Moran's I values of three or more ring PAHs decreased with the increase of the distance. And as the distance ranged from 0 to 25.0 km, their spatial autocorrelations were weaken with the distance. A good superposition and the approximate isotropic of the semivariogram values in the northeast-southwest, southeast-northwest and east-west were observed. However, with the effect of water flow, the semivariation values of the PAHs concentrations in the south-north were different from those in the other three directions. The result of cross-validation showed that the ordinary Kriging interpolation method can well predict the spatial distribution of PAHs in the sediment of Minjiang river in Fuzhou City. The PAH concentrations approximately showed a downward trend with the water flow direction.