水稻秸秆腐解液对水稻根部吸收纳米银(AgNP)速率的影响

Effect of Decomposed Rice Straw Solution on AgNP Uptake by Rice Roots

以水稻秸秆腐解液作为有机质加入纳米银(Ag NP)体系中,考察总有机碳(TOC)浓度和分子量组分对水稻根部吸收Ag NP速率的影响。结果表明,当ρ(TOC)为0~20 mg·L^(-1)时,水稻根部对Ag NP的吸收速率随TOC浓度的升高呈线性降低;当ρ(TOC)达20~80 mg·L^(-1)时,水稻根部对Ag NP的吸收速率趋于稳定。溶液中Ag NP的动力学过程表明,水稻秸秆腐解液抑制了Ag NP溶出的过程,不同TOC浓度处理组ρ(Ag+)比对照降低27.5%~95.5%,且ρ(TOC)越高,溶液中Ag+浓度越低。水稻秸秆腐解液能促进Ag NP颗粒的团聚,增大Ag NP颗粒尺度,使Ag NP不易被水稻吸收。水稻秸秆腐解液的不同分子量组分也会影响水稻根部对Ag NP的吸收速率,且低分子量组分(<3 k Da)和未超滤的对照组水稻秸秆腐解液对水稻根部吸收Ag NP速率的影响相近,说明低分子量组分对水稻根部吸收Ag NP起重要作用。

Decomposed rice straw solution was used as amendment of organic matter to investigate effects of natural organic matter（ NOM） on Ag NP phyto-availability. Ag NP uptake rate decreased with increasing levels of total organic carbon（ TOC,0-20 mg·L-1） and then tended to level off when TOC rose beyond 20 mg·L-1till 80 mg·L-1in concentration. Analysis of the dynamic process of Ag NP in the solution demonstrates that dissolution of Ag NP was inhibited by NOM and decreased by 27. 5%-95. 5% in a dose-dependent manner as against the CK. Obviously the amendment of NOM leads to a reduction of the concentration of silver ion dissolved in the exposure medium and consequently a lower Ag NP uptake rate of the crop. Meanwhile,the NOM tended to promote aggregation of Ag NP,thus expanding the size of Ag NP particles,and making them hard to be absorbed by rice. In addition,composition of NOM in molecular weight would also affect AgNP uptake. NOM low in molecular weight（ 〈3 k Da） was found to have an effect on Ag NP uptake comparable to that the pristine NOM did,indicating that the fraction of low molecular weight NOM plays an important role in Ag NP uptake by rice roots.