Land surface evapotranspiration (ET) is an important component of the surface energy budget and water cycle. To solve the problem of the spatial-scale mismatch between in situ observations and remotely sensed ET, it is necessary to find the most appropriate upscaling approach for acquiring ground truth ET data at the satellite pixel scale. Based on a data set from two flux observation matrices in the middle stream and downstream of the Heihe River Basin, six upscaling methods were intercompared via direct validation and cross validation. The results showed that the area-weighted method performed better than the other five upscaling methods introducing auxiliary variables (the integrated Priestley-Taylor equation, weighted area-to-area regression kriging [WATARK], artificial neural network, random forest [RF], and deep belief network methods) over homogeneous underlying surfaces. Over moderately heterogeneous underlying surfaces, the WATARK method performed better. However, the RF method performed better over highly heterogeneous underlying surfaces. A combined method (using the area-weighted and WATARK methods for homogeneous and moderately heterogeneous underlying surfaces, respectively, and using the RF method for highly heterogeneous underlying surfaces) was proposed to acquire the daily ground truth ET data at the satellite pixel scale, and the errors in the ground truth ET data were evaluated. The Dual Temperature Difference (DTD) and ETMonitor were validated using ground truth ET data, which solve the problem of the spatial-scale mismatch and quantify uncertainties in the validation process.

A method was developed for determination of Cu(II) ions quantitatively by measuring fluorescent intensity of pheophytin-a (Pheoa) solution. The Pheoa was obtained by de-intercalation of magnesium from the porphyrin ring of chlorophyll-a (Chla) extracted from fresh spinach leaves. Its two UV-Vis absorption peaks at 505 and 535 nm in acetone solution have been observed but disappeared when the acetone solution of Pheoa was mixed with a Cu(II) ion aqueous solution. A fluorescence quenching phenomenon was thus observed when the acetone solution of Pheoa was mixed with an aqueous solution of Cu(II) ions. However, other physiologically relevant cations rarely caused any quenching fluorescence of Pheoa under the same experimental conditions. Kinetics of the fluorescence fading process was investigated by measuring the effects of Cu(II) ion concentration, reaction time and reaction temperature on the fluorescence intensity of the Pheoa acetone solution. An activation energy of (10±1) kJ•mol -1 was estimated from Arrhenius empirical relation assuming that the interaction between the Pheoa and the Cu(II) ions was the first order reaction. The calibration graph obtained with the fluorescence was linear over the Cu(II) concentration range of 8.0×10-5 -8.0×10 -7 mol•dm -3 with a detection limit of 8.0×10 -7 mol•dm -3 for Cu(II)ion.

No abstract

No abstract

No abstract