China were examined to determine relationships between lake water sources (fresh versus saline) and their fluorescence/absorption characteristics. Results indicated significant differences regarding DOC concentration and a CDOM (254) between freshwater (6.68 mg C L-1 , 19.55 m-1) and saline lakes (27.4 mg C L-1 , 41.17 m-1). While humic-like (F 5) and fulvic-like (F 3) compounds contributed to CDOM fluorescence in all lake waters significantly, their contribution to total fluorescence intensity (F T) differed between saline and freshwater lakes. Significant negative relationships were also observed between lake altitude with either F 5 (R 2 =0.63, N=306) or F T (R 2 =0.64, N=306), suggesting that the abundance of humic-like materials in CDOM tends to decrease with increased in lakes altitude. In high-altitude lakes, strong solar irradiance and UV exposure may have induced photo-oxidation reactions resulting in decreased abundance of humic-like substances and the formation of low molecular weight compounds. These findings have important implications regarding our understanding of C dynamics in lacustrine systems and the contribution of these ecosystems to the global C cycle.
Abstract. The seasonal characteristics of fluorescent components in chromophoric dissolved organic matter (CDOM) for lakes in the semiarid region of Northeast China were examined by excitation–emission matrix (EEM) spectra and parallel factor analysis (PARAFAC). Two humic-like (C1 and C2) and protein-like (C3 and C4) components were identified using PARAFAC. The average fluorescence intensity of the four components differed under seasonal variation from June and August 2013 to February and April 2014. Components 1 and 2 exhibited a strong linear correlation (R2 = 0.628). Significantly positive linear relationships between CDOM absorption coefficients a(254) (R2 = 0.72, 0.46, p < 0.01), a(280) (R2 = 0.77, 0.47, p < 0.01), a(350) (R2 = 0.76, 0.78, p < 0.01) and Fmax for two humic-like components (C1 and C2) were exhibited, respectively. A significant relationship (R2 = 0.930) was found between salinity and dissolved organic carbon (DOC). However, almost no obvious correlation was found between salinity and EEM–PARAFAC-extracted components except for C3 (R2 = 0.469). Results from this investigation demonstrate that the EEM–PARAFAC technique can be used to evaluate the seasonal dynamics of CDOM fluorescent components for inland waters in the semiarid regions of Northeast China, and to quantify CDOM components for other waters with similar environmental conditions.
A bacterial strain C21 isolated from constructed wetland soil was identified as Arthrobacter sp. based on 16S rRNA gene sequence analysis and physio-biochemical characteristics and was capable of utilizing di-n-butyl phthalate (DBP) as a carbon and energy source for growth. Strain C21 can also utilize other phthalates (PAEs) up to a molecular weight of 390.56 and phthalic acid (PA). The biodegradability of these compounds decreased with the increase in the length of phthalate alkyl chains and molecular weight. Kinetic analysis indicated that the strain C21 cell growth on DBP fitted well with Haldane-Andrews' model (R (2) > 0.98) with μ max, K s, and K i of 0.12/h, 4.2 mg/L, and 204.6 mg/L, respectively. When the initial DBP concentration was lower than 100 mg/L, DBP biodegradation reaction fitted with the first-order kinetics. The results suggested that Arthrobacter strain C21 played an active role in the bioremediation of the wetland contaminated with phthalates.
Abstract:The application of crop residue has become increasingly important for providing a barrier against water and wind erosion and improving soil organic matter content, infiltration, evaporation, temperature, and soil structure. The objectives of this work were to: (i) estimate maize residue cover (MRC) from Landsat-8 OLI images using seven vegetation indices (VIs) and eight textural features; and (ii) compare the VI method, textural feature method, and combination method (integration of textural features and spectral information) for estimating MRC with partial least squares regression (PLSR). The results showed that the normalized difference tillage index (NDTI), simple tillage index (STI), normalized difference index 7 (NDI7), and shortwave red normalized difference index (SRNDI) were significantly correlated with MRC. The MRC model based on NDTI outperformed (R 2 = 0.84 and RMSE = 12.33%) the models based on the other VIs. Band3mean, Band4mean, and Band5mean were highly correlated with MRC. The regression between Band3mean and MRC was stronger (R 2 = 0.71 and RMSE = 15.21%) than those between MRC and the other textural features. The MRC estimation accuracy using the combination method (R 2 = 0.96 and RMSE = 8.11%) was better than that based on only the VI (R 2 = 0.88 and RMSE = 11.34%) or textural feature (R 2 = 0.90 and RMSE = 9.82%) methods. The results suggest that the combination method can be used to estimate MRC on a regional scale.
OPEN ACCESSRemote Sens. 2015, 7 14560
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.