[Identification of Nitrate Sources and the Fate of Nitrate in Downstream Areas: A Case Study in the Taizi River Basin].

A total of 14 samples were collected in May 2016(dry season)and August 2016 (wet season) in the downstream area of the Taizi River. △15 N-NO3- and △18 O-NO3- were determined using the azide method, and △18 O-H2O was determined using a CO2-H2O equilibration technique. To identify NO3- sources and transformations in the downstream area of Taizi River Basin, ion chromatography, Nessler's reagent spectrophotometry, the azide method, and CO2-H2O equilibration methods were utilized to determine the concentrations of NO3-, Cl-, NH4+-N, and isotopic compositions (△15 N and △18 O) of NO3- and the △18 O-H2O in surface water. The results showed that the NO3- was mainly derived from mixed sources. During the dry season, the nitrate in the surface water was derived from soil nitrogen, manure, and sewage in the upper reaches, and mainly derived from synthetic fertilizer, manure, and sewage in the middle and lower reaches of the Beisha River. The nitrate was mainly derived from manure and sewage in the Nansha River. The nitrate was mainly derived from soil nitrogen in the upper reaches, mainly derived from synthetic fertilizer, manure, and sewage in the middle reaches, and mainly derived from manure and sewage in the lower reaches of the Haicheng River. During the wet season, the nitrate sources in surface water were soil nitrogen, synthetic fertilizer, manure, and sewage in the Beisha River; synthetic fertilizer, manure, and sewage in the middle and lower reaches of the Haicheng River and the Nansha River; and soil nitrogen and synthetic fertilizer in the upper reaches of the Haicheng River. NO3- and NH4+-N concentrations decreased with increasing △15 N-NO3- from the dry season to the wet season, indicating that volatilization of NH4+-N and denitrification of NO3- might occur during the wet season. There is a slightly positive relationship between the reciprocal of the concentration of 1/ρ(NO3-) and △15 N-NO3- during the wet season, indicating that mixing processes occurred in surface water. The results will provide information on nitrate sources during seasonal variations in the plain areas.

Pd supported on carbon containing nickel, nitrogen and sulfur for ethanol electrooxidation.

Carbon material containing nickel, nitrogen and sulfur (Ni-NSC) has been synthesized using metal-organic frameworks (MOFs) as precursor by annealing treatment with a size from 200 to 300 nm. Pd nanoparticles supported on the Ni-NSC (Pd/Ni-NSC) are used as electrocatalysts for ethanol oxidation in alkaline media. Due to the synergistic effect between Pd and Ni, S, N, free OH radicals can form on the surface of Ni, N and S atoms at lower potentials, which react with CH3CO intermediate species on the Pd surface to produce CH3COO- and release the active sites. On the other hand, the stronger binding force between Pd and co-doped N and S is responsible for enhancing dispersion and preventing agglomeration of the Pd nanoparticles. The Pd(20 wt%)/Ni-NSC shows better electrochemical performance of ethanol oxidation than the traditional commercial Pd(20 wt%)/C catalyst. Onset potential on the Pd(20 wt%)/Ni-NSC electrode is 36 mV more negative compared with that on the commercial Pd(20 wt%)/C electrode. The Pd(20 wt%)/Ni-NSC in this paper demonstrates to have excellent electrocatalytic properties and is considered as a promising catalyst in alkaline direct ethanol fuel cells.

[Identification of Nitrate Sources and Transformation Processes in Midstream Areas:A Case in the Taizi River Basin].

This study analyzed the nitrate (NO3-), ammonia nitrogen (NH4+-N), chloride (Cl-), δ15 N-NO3-, δ18O-NO3-, and δ18O-H2O in the surface water to identify the nitrate sources and transformation processes in midstream areas of the Taizi River basin in May and August 2016, corresponding to the dry season and wet season, respectively. The results indicated that the NO3-, Cl-, and NH4+-N concentrations and the δ18O-NO3- in the dry season were greater than those in the wet season, and the δ15 N-NO3- did not show significant seasonal variations based on the Man-Whitney U test. The NO3- was derived mainly from the mixed sources according to the ranges of NO3-/Cl-, δ15 N-NO3-, and δ18O-NO3-. The nitrate sources in the surface water were synthetic fertilizer, soil nitrogen, manure, and sewage in the Xihe River (XR), Lanhe River (LR), and Xiada River (XDR) and soil nitrogen and synthetic fertilizer in the Er dao River (EDR) during the wet season. The sources were synthetic fertilizer and soil nitrogen in the XDR and soil nitrogen, manure, and sewage in the XR, LR, and EDR during the dry season. The significant negative relationship between NO3- and NH4+ and the significant positive relationship between NO3- and δ15 N-NO3- in the wet season indicated that the volatilization and nitrification of soil N might be related to NO3- sources in the wet season. NH4+-N and δ15 N-NO3- increased with decreasing NO3- and Cl- in EDR and LR during the wet season, which indicated denitrification processes occurred. There was a significant relationship between NO3- and Cl-, indicating that mixing processes occurred in the surface water during the two sampling periods. This study will provide a better understanding for nitrate sources related to seasonal variations and transformation processes in hilly areas.