Carbon and nitrogen allocations in corn grown in Central and Northeast China: different responses to fertilization treatments

In order to reveal the impact of various fertilization strategies on carbon（C） and nitrogen（N） accumulation and allocation in corn（Zea mays L.）, corn was grown in the fields where continuous fertilization management had been lasted about 18 years at two sites located in Central and Northeast China（Zhengzhou and Gongzhuling）, and biomass C and N contents in different organs of corn at harvest were analyzed. The fertilization treatments included non-fertilizer（control）, chemical fertilizers of either nitrogen（N）, or nitrogen and phosphorus（NP）, or phosphorus and potassium（PK）, or nitrogen, phosphorus and potassium（NPK）, NPK plus manure（NPKM）, 150% of the NPKM（1.5NPKM）, and NPK plus straw（NPKS）. The results showed that accumulated C in aboveground ranged from 2 550–5 630 kg ha^–1 in the control treatment to 9 300–9 610 kg ha^–1 in the NPKM treatment, of which 57–67% and 43–50% were allocated in the non-grain organs, respectively. Accumulated N in aboveground ranged from 44.8–55.2 kg ha^-1 in the control treatment to 211–222 kg ha^–1 in the NPKM treatment, of which 35–48% and 33–44% were allocated in the non-grain parts, respectively. C allocated to stem and leaf for the PK treatment was 65 and 49% higher than that for the NPKM treatment at the both sites, respectively, while N allocated to the organs for the PK treatment was 18 and 6% higher than that for the NPKM treatment, respectively. This study demonstrated that responses of C and N allocation in corn to fertilization strategies were different, and C allocation was more sensitive to fertilization treatments than N allocation in the area.

背景离子类型和浓度对聚苯乙烯微塑料/铅在饱和石英砂中共运移的影响

为阐明水化学条件对微塑料和重金属运移的影响,初步明确两种环境污染物共运移过程中的耦合效应及其对环境条件的响应机制,研究了背景电解质离子不同价态和浓度组成条件下1μm聚苯乙烯微塑料(PS-MPs)和Pb^(2+)在饱和一维砂柱中的单独及共迁移行为.结果表明:背景离子浓度的增加或价态的升高均会抑制PS-MPs的单独运移能力,当Na^(+)浓度从1mmol/L增加到100mmol/L,PS-MPs和石英砂之间的排斥势垒下降了1348kT;当Ca^(2+)浓度从1mmol/L增加到100mmol/L,PS-MPs和石英砂之间的排斥势垒下降了956kT.PS-MPs/Pb^(2+)二元体系中Pb^(2+)能降低PS-MPs的迁移能力,背景离子浓度和价态的提升可削弱Pb^(2+)对PS-MPs运移能力的抑制性.当Na^(+)浓度从1mmol/L增加到100mmol/L,PS-MPs和石英砂之间的排斥势垒下降了1100kT;当Ca^(2+)浓度从1 mmol/L增加到100mmol/L,PS-MPs和石英砂之间的排斥势垒下降了543kT.背景离子浓度的增加或价态的升高能促进Pb^(2+)的单独运移能力.P S-MP s/Pb^(2+)二元体系中,PS-MPs能够促进Pb^(2+)的运移,背景离子浓度较低时,P S-MPs负载Pb^(2+)的迁移率较高,反之亦然.对于PS-MPs和Pb^(2+)单运移体系,背景阳离子浓度和价态的提升可进一步屏蔽PS-MPs及石英砂表面负电荷,竞争吸附石英砂表面结合位点,抑制PS-MPs运移,促进Pb^(2+)运移;对于PS-MPs和Pb^(2+)共运移体系,背景离子浓度和价态的提升可通过调节Pb^(2+)与PS-MPs及石英砂表面的相互作用,削弱Pb^(2+)对PS-MPs迁移能力的抑制作用.背景离子对P S-MPs表面位点的竞争吸附及对电荷的屏蔽效应影响PS-MPs对Pb^(2+)的负载迁移能力.