The impacts of natural processes and anthropogenic input on riverine nitrate (NO-3) could be identified by NO-3 concentrations and nitrogen and oxygen isotope ratios (δ15N-NO-3 and δ18O-NO-3); however, the effects of variable land use on riverine NO-3 sources and transformations remain unclear. In particular, the human impacts on riverine NO-3 in mountain areas are still unknown. The Yihe River and Luohe River were used to elucidate this question due to their spatially heterogeneous land use. Hydrochemical compositions, water isotope ratios (δD-H2O and δ18O-H2O), and δ15N-NO-3 and δ18O-NO-3 values were utilized to constrain the NO-3 sources and transformations affected by different land use types. The results indicated that ① the mean nitrate concentrations in the Yihe River and Luohe River waters were 6.57 and 9.29 mg·L-1, the mean values of δ15N-NO-3 were 9.6‰ and 10.4‰, and the average δ18O-NO-3 values were -2.2‰ and -2.7‰, respectively. Based on the analysis of δ15N-NO-3 and δ18O-NO-3 values, the NO-3 in the Yihe and Luohe Rivers were derived from multiple sources, and nitrogen removal existed in the Luohe River, but the biological removal in the Yihe River was weak. ② The contributions of different nitrate sources were calculated using a Bayesian isotope mixing model (BIMM) based on δ15N-NO-3 and δ18O-NO-3 values of river water in the mainstream and tributaries with spatial locations. The results revealed that sewage and manure had major impacts on riverine nitrate in the upper reaches of both the Luohe River and Yihe River, where forest vegetation was widely distributed. However, the contributions from soil organic nitrogen and chemical fertilizer were higher in the upper reaches than in downstream ones. The contributions of sewage and manure still increased in the downstream reaches. Our results confirmed the primary impacts of point sources, e.g., sewage and manure, on riverine nitrate in the studied area, and the contributions of nonpoint sources, e.g., chemical fertilizer, had not increased as the agricultural activities elevated the downstream. Therefore, more attention should be paid to point source pollution treatment, and the high-quality development of ecological civilization in the Yellow River Basin should be maintained.
Driving fatigue and even arm numbness can be caused by steering wheel jitters with engine idling.Objective measurement and subjective evaluation are applied of the analysis on the influencing factor of steering wheel jitter in two conditions, engine idling with air conditioning on and off.The prior optimization on steering system stiffness result shows that steering wheel vibration center acceleration is 0.053g when the air condition is off, as reduced by 30%, this value reduced to 0.139g when the air conditioner is activated, as reduced by 26%.The first order frequency of the steering system is higher than 32Hz, having avoided the engine idle vibration frequency .The score of subjective evaluation with air conditioning off and on is 6 and 6.5 respectively, as acceptable.
A new tubular bio-trickling filter (M-BTF) which integrated the theory of microbial fuel cell by building in the proton exchange membrane was designed in this study. For comparison, an original bio-trickling filter (O-BTF) was started parallelly to better understand the effect of closed circuit. Performance of both the BTFs in purifying ethyl acetate (EA) under different conditions containing inlet EA loadings and empty bed residence time were evaluated. Results showed that the closed-circuit condition could stimulate the growth of microorganisms and speed up the start-up of the BTF. Removal efficiency (Re) of M-BTF was about 5% higher than O-BTF under different conditions with the maximum output voltage of 536mV. Biomass was mainly influenced by the inlet EA loadings and changed little after 38 days of operation. Microorganism community construction showed that the electrode had high selectivity to the bacterial strains which resulted in more electroactive bacteria surviving in M-BTF.
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