Research of Hydrochemical Properties of Hyporheic Zone along the WeiHe River in Shanxi Segment

By sampling the undercurrent belts of riverfront, shoal and riverbed at Xianyang, Xi’an, Lintong and Huaxian in Weihe basin of Shaanxi province in the summer and winter of 2014 and analyzed the water chemical character through Piper trilinear chart, This thesis has come to the following conclusions: (1) PH in shoal range from 7.42 to 7.98, and in riverfront, the average is 7.58, present alkaline. The TDS in riverfront is higher than that of river water, it range from 506.5 to 824, 616.06 mg?L?1 in average. (2) All of the water at riverfront, shoal and riverbed under the influence of carbonate. The concentration of ionic concentration at shoal is between riverbed and riverfront, by contrast, it close to riverfront. This result means the shoal recharged by both surface and river water, and the groundwater recharge is more conspicuous than surface water. Besides, from upstream to downstream, the two kinds of main ions ( and Ca2+) have little change in the same river, it related to such factors as river evaporation, the exchange interaction of surface and underground water and so on.

Nitrous Oxide and Methane Fluxes During the Maize Season Under Optimized Management in Intensive Farming Systems of the North China Plain

Addressing concerns about mitigating greenhouse gas （GHG） emissions while maintaining high grain yield requires improved management practices that achieve sustainable intensification of cereal production systems. In the North China Plain, a field experiment was conducted to measure nitrous oxide （N2O） and methane （CH4） fluxes during the maize （Zea mays L.） season under various agricultural management regimes including conventional treatment （CONT） with high N fertilizer application at a rate of 300 kg N ha-1 and overuse of groundwater by flood irrigation, optimal fertilization 1 treatment （OPTIT）, optimal fertilization 2 treatment （OPT2T）, and controlled-release urea treatment （CRUT） with reduced N fertilizer application and irrigation, and a control （CK） with no N fertilizer. In contrast to CONT, balanced N fertilization treatments （OPT1T, OPT2T, and CRUT） and CK demonstrated a significant drop in cumulative N20 emission （1.70 v.s. 0.43-1.07 kg N ha-l）, indicating that balanced N fertilization substantially reduced N20 emission. The vMues of the N20 emission factor were 0.42%, 0.29%, 0.32%, and 0.27% for CONT, OPTIT, OPT2T, and CRUT, respectively. Global warming potentials, which were predominantly determined by N20 emission, were estimated to be 188 kg CO2-eq ha-1 for CK and 419-765 kg CO2-eq ha-1 for the N fertilization treatments. Global warming potential intensity calculated by considering maize yield was significantly lower for OPT1T, OPT2T, CRUT, and CK than for CONT. Therefore, OPTIT, OPT2T, and CRUT were recommended as promising management practices for sustaining maize yield and reducing GHG emissions in the North China Plain.