LAUSR

Abstract. Spatiotemporal variations in the characteristics of fluorescent dissolved organic matter (FDOM) components from 63 lakes across the Tibet Plateau, China, are examined using excitation-emission matrix spectra (EEM) and fluorescence regional integration (FRI) from 2014 to 2017. Freshwater (N = 135) and brackish water (N = 109) samples from 63 lakes were grouped according to salinity or electrical conductivity. In order to compare results between the lakes, cumulative volumes beneath the EEM values (φi, i = I, II, III, IV, V) were normalized to a DOC concentration of 1 mg/L. EEM-FRI identified tyrosine-like (φI), tryptophan-like (φII), fulvic-like (φIII), microbial protein-like (φIV), and humic-like (φV) fluorescence regions, as well as their proportions (Pi). Chromophoric dissolved organic matter (CDOM) absorption parameters, fluorescence indices, average fluorescence intensities of the five fluorescent components and total fluorescence intensities (φT) differed under spatial variation among brackish and freshwater lakes (ANOVA, p   0.79, t-test, p   19 ‰ (averaged EC, 23 764 μs cm −1) (t-test, p   2900 h. Redundancy analysis (RDA) indicates that a(254) and a(350) have a correlation with CDOM in brackish lakes. a(254), HIX and a(350) were also correlated with water quality. Strong evapoconcentration, intense ultraviolet irradiance and landscape features of the Tibet Plateau may be responsible for the FDOM characteristics identified in this study.