Sunlight-induced phototransformation of transphilic and hydrophobic fractions of Suwannee River dissolved organic matter.

Sunlight-induced chemical changes of both transphilic (SWR-TPH) and hydrophobic (SWR-HPO) fractions of Suwannee River dissolved organic matter (DOM) were followed by ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). Irradiated SWR-TPH exhibited increase of chemodiversity, loss of some aromatic compounds, and almost no change in terms of average values of m/z, O/C and double bond equivalents (DBE). Irradiated SWR-HPO showed decrease of chemodiversity, average values of m/z, O/C and DBE. Irradiation of SWR-HPO produced oxygenated (O/C > 0.7) and aliphatic new compounds and removed some aromatics and carboxyl-rich alicyclic molecules (CRAM). Comparatively, CHO-compounds of SWR-TPH were relatively stable with a minor class of aromatic compounds disappeared under sunlight irradiation. Photochemical processing of SWR-HPO generated highly oxygenated new compounds that were readily present in SWR-TPH, implying that sunlight changes the hydrophobicity of DOM and that SWR-HPO is a photochemical precursor for SWR-TPH. This study contributed to the developing knowledge on organic matter phototransformation, particularly the transformation pattern of SWR-TPH that was never described previously; it also demonstrated the role of sunlight in producing SWR-TPH compounds from SWR-HPO and consequently driving the transformation of organic matter

Droplet-based compartmentalization of chemically separated components in two-dimensional separations

We demonstrate that nanolitre-sized droplets are an effective tool in coupling two-dimensional separations in both time and space. Using a microfluidic droplet connector, chemically separated components can be segmented into nanolitre droplets. After oil filtering and droplet merging, these droplets are loaded into a second dimension for comprehensive separation

Evaluation of EPIC Model of Soil NO3-N in Irrigated and Wheat-Maize Rotation Field on the Loess Plateau of China

International audienceEPIC model has been evaluated and used world wide, however there is still some disagreements on the simulation results of nitrogen cycle. Based on field experimental data, simulation results of soil NO3-N was evaluated and the parameter sensitivity for simulated NO3-N was analyzed in irrigated winter wheat / summer maize field on the Loess Plateau of China. Results showed 1) EPIC model estimated soil NO3-N content and its movement among different soil layers well, with the mean RRMSE value of 0.46, for irrigated winter wheat / summer maize cropping system in the semi-humid region of the Loess Plateau. 2) Simulation results of soil NO3-N was more sensitive to soil parameters, compared with crop parameters and meteorological parameters. 3)To improve the parameter value of BN2, HI, TB, WA, CNDS, BD and FC was better to the EPIC model to simulate soil NO3-N on the Loess Plateau of China