A novel adsorbent of covalently bounded quaternary ammonium activated carbon (CQA) was prepared by silylation reaction with both organosilicon quaternary ammonium salt (QA) and activated carbon (AC) as raw materials. The CQA was characterized by FTIR, SEM and BET. The results showed that QA was successfully loaded on the surface of AC by covalent binding, and had an important influence on the morphology and structure of AC. The nitrate and phosphate adsorption capacities for CQA were greatly improved. The adsorption behaviors of nitrate and phosphate from aqueous solutions on CQA were investigated using batch experiments. The kinetics study revealed that adsorption of nitrate and phosphate onto CQA followed the pseudo-second-order kinetic model, indicating that the adsorption process was mainly controlled by the chemisorptions. The adsorption data fitted Langmuir and Freundlich isotherm models well, and the maximum nitrate and phosphate adsorption capacities for CQA were 14.829 and 8.442 mg/g, respectively. The effects of pH on the adsorption of nitrate and phosphate were also investigated. The results showed that when pH was from 4 to 9, it was suitable for simultaneous removal of nitrate and phosphate from aqueous solution by CQA.
A 50-cm core (hereafter referred to as “XFYC12-2”) was retrieved from western Foye Chi (Buddha Pond), a glacier-scour lake on southern slope of Taibai Mountain that is the main massif and peak of Qinling Mountain Range. Accelerator mass spectrometry (AMS) 14C dating and analyses of isotopic carbon and nitrogen of organic matter were performed on samples from XFYC12-2. Climatic and environmental changes occurring around this alpine during over the past ~1800 years were therefore reconstructed. Climatic and environmental conditions were still fairly cool and arid during 1811−1380 (or 1440) aBP. In 1380 (or 1440)−840 aBP, the climate and environment were warm and humid. This episode is probably corresponding to Medieval Warm Period (MWP). Climatic and environmental conditions deteriorated subsequently and were thus cold and dry over the period of 840?460 (or 520) aBP. This phase may correspond to Little Ice Age (LIA). Climatic and environmental conditions have turned to be warm and wet again during 460 (or 520)−100 aBP. The aforementioned process of climatic and environmental changes appears quite similar to what was reconstructed around another two lakes at the high altitudes of Taibai Mountain, what was generalized for eastern China and what was identified at another four study areas in eastern China.
Foye Chi is a small lake developing in a cirque in the alpine belt of southern slope of Taibai Mountain which is the peak of the Qinling Mountain Range. A 70 cm deep pit was excavated on the desiccated floor of this lake and sediments were sampled from the pit’s wall. AMS 14C dating was performed for three samples from this sediment profile. For all the 56 samples, analysis of total organic carbon content (TOC) and carbon-nitrogen ratio (C/N) and measurements of low-frequency magnetic susceptibility (χlf) and anhysteretic remanent magnetization (ARM) were undertaken. So were analyses of particle-size and pollen. ARM/χlf was further calculated as well. A chronological framework was developed based on the dating results. Variations in TOC, C/N, χlf, ARM, ARM/χlf, mean particle-size and percentage of Quercus pollen of this sequence were interpreted and climatic and environmental changes occurring around Foye Chi since 5520 aBP were so preliminarily inferred. The climate and environment were generally cold and arid during 5520-3800 aBP and the coldest and driest during 5100-4300 aBP. During 3800-2300 aBP, the climate and environment have turned to be warm and humid. The climate and environment were even wetter during 2300-1300 aBP and warmer during 1300-700 aBP which might be the warmest phase of the last ~5500 years. During 700-500 aBP, the climate and environment tended to be cool and arid again. These climate-environment changes happening during the middle and late Holocene in alpine belt of Taibai Mountain are generally similar to the changes at some sites in the region influenced by the East Asian monsoon in China since these sites are all under the influence of East Asian monsoon.
By virtue of kinetic proofreading theory, the puzzles of selectivity and specificity common in cellar activities are successfully explained. The chemical master equation is adopted to describe stochastic processes of kinetic proofreading models with two and three middle steps. Stochastic properties around the steady state are analyzed with the linear noise approximation under various parameters. Relations between noise density and parameters are revealed with numerical simulation. The result suggest that noises propagate and escalate as reactions proceed, furthermore multiple reaction rates determine noise intensity.
