基于高光谱遥感的沿海河口无机氮浓度空间分布特征解译

Interpretation of Spatial Distribution Pattern for Dissolved Inorganic Nitrogen Concentration in Coastal Estuary Using Hyperspectral Data

利用39组样本的野外实测光谱结合Hyperion影像资料,建立了高悬沙含量沿海河口可溶性无机氮(dissolved inorganic nitrogen,DIN)的高光谱定量遥感解译模型,实现DIN浓度空间分布规律的遥感反演及动态监测.研究发现,当悬沙浓度>0.1kg/m3时,DIN浓度与悬沙含量之间呈显著的倒数相关关系,相关系数R2为0.617.据此首先将重采样处理后的野外实测光谱与同步DIN浓度数据进行统计相关分析,筛选出2个对DIN浓度变化敏感的波段,中心波长分别为630nm和804nm;然后利用波段反射率R804和R630计算出仿泥沙遥感参数因子R804×R630/(R804-R630),建立其与实测DIN浓度的非线性遥感模型,29组建模样本和10组检验样本的相关系数R2分别为0.746和0.67,DIN浓度平均绝对误差分别为109.07μg/L和147.58μg/L.将该非线性遥感模型应用于Hyperion影像,获得了射阳河口DIN浓度的空间分布特征,DIN浓度的变化范围为52～513μg/L.可以看出,在以悬沙为主要悬浮物的沿海河口,遥感解译得到的DIN浓度扩散趋势与潮流的运动以及悬沙的运移规律密切相关.因此,在无需了解水动力状况的条件下,高光谱遥感是对DIN浓度进行动态监测的有效手段.

Choosing dissolved inorganic nitrogen（DIN） as one of the representative nutritional salt monitoring indexes,a hyperspectral remotely sensed inversion model was built and applied to quantitatively retrieve water quality parameters with its spatial distribution patterns in coastal estuary with high suspended sediment concentration（SSC）.It was found that when SSC was larger than 0.1 kg /m3,DIN concentration had a notable inverse correlation with SSC and the correlation coefficient R2 reached 0.617.Based on this conclusion,firstly the in-situ observed water surface remote sensing reflectance was resampled according to the spectral response characters of Hyperion sensor.And then,statistical correlation analysis between reflectance and DIN concentration was carried out.The results showed that band reflectance of R804 and R630 representing the second and first reflectance peak of water spectrum curve were sensitive to the variation of DIN concentration.And then,a pseudo remotely sensed sand parameter index R804 × R630 /（R804-R630） was calculated for the construction of the nonlinear DIN quantitative reversion model.Correlation coefficient R2 between observed and simulated DIN concentrations for 29 calibrating samples and 10 validating samples were 0.746 and 0.67,while their mean absolute errors reached 109.07 and 147.58 μg /L,respectively.The model was then applied on Hyperion hyperspectral image to get the spatial distribution character of DIN concentration in Sheyanghe river estuary and the DIN concentration was between 52 to 513 μg /L.Results indicated that in coastal estuary which was dominated by suspended sediments,the diffusive trends of DIN concentration reversed by remote sensing techniques had an intimate relationship with motions of tidal current and transportation attributes of SSC.As the hydrodynamic conditions were unclear,hyperspectral remote sensing technique was an effective technical way for dynamic survey of DIN concentration.