Seasonal variations in the nitrogen isotopic composition of dissolved nitrate(δ 15 NO 3) were investigated in the surface waters of the Changjiang River estuary in 2009 and 2010. δ 15 NO 3 varied between-4.6‰ and ...Seasonal variations in the nitrogen isotopic composition of dissolved nitrate(δ 15 NO 3) were investigated in the surface waters of the Changjiang River estuary in 2009 and 2010. δ 15 NO 3 varied between-4.6‰ and 8.9‰ with changes in temperature, salinity, dissolved oxygen concentrations, and the composition of the dissolved inorganic nitrogen pool. In February, biological processes decreased because of low temperature, and the mean δ 15 NO 3 near the river mouth was 2.4‰. In May, δ 15 NO 3 was the highest in the surface waters among all seasons. Analysis on the conservative mixing revealed assimilation, and this fi nding is supported by positive relationship between Chl a and δ 15 NO 3. The fractionation factor of assimilation was estimated to be 2.0‰ by the Rayleigh equation. Nitrifi cation was supported based on the mixing behaviors in November 2010 and the low δ 15 NO 3 values in May and November 2009. The high ammonium concentrations in the adjacent marine area and positive relationships between total organic nitrogen and δ 15 NO 3 in November 2010 indicated that mineralization was taking place.展开更多
综述了Q SRR中的多元线性回归(M ult ple L inear Reg resio n,M L R)、偏最小二乘回归(Part ial L east Squares Regr ession,P LSR)、人工神经网络(Ar tificial N eural N et wor ks,AN N)几种常用建模方法、分子描述符的选取的要点...综述了Q SRR中的多元线性回归(M ult ple L inear Reg resio n,M L R)、偏最小二乘回归(Part ial L east Squares Regr ession,P LSR)、人工神经网络(Ar tificial N eural N et wor ks,AN N)几种常用建模方法、分子描述符的选取的要点及原则及相关模型的建立和评价等方法在化学与环境化合物分析中的应用现状,并对QSRR在该领域的研究方向和发展前景进行了展望,以期为今后更深层次的研究作综合性的参考。展开更多
基金Supported by the National Natural Science Foundation of China(No.41276116)the Fund for Creative Research Groups by NSFC(No.41121064)the National Basic Research Program of China(973 Program)(No.2010CB428706)
文摘Seasonal variations in the nitrogen isotopic composition of dissolved nitrate(δ 15 NO 3) were investigated in the surface waters of the Changjiang River estuary in 2009 and 2010. δ 15 NO 3 varied between-4.6‰ and 8.9‰ with changes in temperature, salinity, dissolved oxygen concentrations, and the composition of the dissolved inorganic nitrogen pool. In February, biological processes decreased because of low temperature, and the mean δ 15 NO 3 near the river mouth was 2.4‰. In May, δ 15 NO 3 was the highest in the surface waters among all seasons. Analysis on the conservative mixing revealed assimilation, and this fi nding is supported by positive relationship between Chl a and δ 15 NO 3. The fractionation factor of assimilation was estimated to be 2.0‰ by the Rayleigh equation. Nitrifi cation was supported based on the mixing behaviors in November 2010 and the low δ 15 NO 3 values in May and November 2009. The high ammonium concentrations in the adjacent marine area and positive relationships between total organic nitrogen and δ 15 NO 3 in November 2010 indicated that mineralization was taking place.
文摘综述了Q SRR中的多元线性回归(M ult ple L inear Reg resio n,M L R)、偏最小二乘回归(Part ial L east Squares Regr ession,P LSR)、人工神经网络(Ar tificial N eural N et wor ks,AN N)几种常用建模方法、分子描述符的选取的要点及原则及相关模型的建立和评价等方法在化学与环境化合物分析中的应用现状,并对QSRR在该领域的研究方向和发展前景进行了展望,以期为今后更深层次的研究作综合性的参考。
