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To study the effect of mineralogical assemblages and chemical characteristics of clays mineral particles on absorption properties in coastal waters of China, we designed a tank experiment and measured the optical properties of suspensions of clay mineral particles for samples collected in Yellow River Estuary (YRE), Changjiang River Estuary (CRE) and Pearl River Estuary (PRE). We designed eight kinds of suspensions of clay mineral particles with concentration of 5, 10, 20, 30, 40, 50, 100 and 200mg/L. The absorption coefficient was measured for all the samples. The results show that the mass-specific absorption coefficient of clay mineral particles (am*) varies for samples collected respectively in YRE, CRE and PRE. The magnitude of am* is higher for samples collected in PRE compared with samples collected in YRE and CRE, especially in the blue band, with am*(410) for the sample collected in PRE 1.5 times higher than that collected in YRE and CRE. We discovered that the composition of clay mineral in PRE is obviously different from that in YRE and CRE. In addition, the content of iron element is higher for samples collected in PRE than that collected in YRE and CRE. The difference in the composition of clay mineral and higher content of iron element could be the reason that the magnitude of am* is significant different for the samples collected in PRE than that collected in YRE and CRE. It suggests that the absorption coefficient of clay mineral particles suspended in waters is not only connected to the SPM concentration, but also mineral and element composition, such as iron. Although the composition of clay mineral and concentration of iron could explain only part of variability observed in the absorption coefficient of clay mineral particles, it is of significant importance for further discover the inherent optical properties in coastal waters and can be helpful for improving the algorithm accuracy in ocean color remote sensing.
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