Nitrated polycyclic aromatic hydrocarbons (NPAHs) are PAH derivatives with more toxic effects to ecosystem, and the partitioning of NPAHs in crop system constitutes the potential exposure to human health through the dietary pathway. In the present study, a novel method for in situ detection of 9-nitroanthracene (9-NAnt) and 3-nitrofluoranthene (3-NFla) adsorbed onto the leaf surfaces of living soybean and maize seedlings was established based on the fiber-optic fluorimetry combined with graphene quantum dots (GQDs) as a fluorescent probe. The detection limits for the in situ quantification of the two adsorbed NPAHs ranged from 0.8 to 1.6 ng/spot (spot represents determination unit, 0.28 cm² per spot). Using the novel method, the effects of GQDs on the adsorption of individual 9-NAnt and 3-NFla by the living soybean and maize leaf surfaces were in situ investigated. The presence of GQDs altered the adsorption mechanism from the sole film diffusion to the combination of film diffusion and intra-particle diffusion, and shortened the time required to achieving adsorption equilibrium by 15.8–21.7%. Significant inter-species and inter-chemical variability existed in terms of the equilibrated adsorption capacity (q_e) with the sequence of soybean > maize and 3-NFla > 9-NAnt. The occurrence of GQDs enlarged the q_e values of 9-NAnt and 3-NFla by 22.8% versus 28.7% for soybean, and 16.2% versus 20.3% for maize, respectively, which was largely attributed to GQDs-induced expansion to the surface area for adsorbing NPHAs and the stronger electrostatic interaction between the -NO₂ of NPAH molecules and the functional groups (e.g., -COOH, -OH) of GQDs outer surfaces. And, the varied enhancement degrees in the order of 3-NFla > 9-NAnt might be explained by the steric effects that resulted in the easier accessibility of -NO₂ of 3-NFla to the outer surface of GQDs. Summarily, the GQDs increased the retention of NPAHs on crop leaf surfaces, potentially threatening the crop security.

硝化多环芳烃（NPAHs）是对生态系统具有较大毒性作用的PAHs衍生物，NPAHs在作物系统中的分配构成了通过膳食途径对人类健康的潜在暴露。本研究建立了一种基于光纤荧光测定法原位检测活体大豆和玉米幼苗叶面吸附的9-硝基蒽（9-NAnt）和3-硝基荧蒽（3-NFla）的新方法与石墨烯量子点（GQD）结合作为荧光探针。两种吸附的NPAHs的原位定量检测限为0.8至1.6 ng/点（点代表测定单位，每个点0.28 cm ² ）。利用这种新方法，原位研究了 GQD 对活体大豆和玉米叶表面吸附单个 9-NAnt 和 3-NFla 的影响。 GQDs的存在将吸附机制从单一的膜扩散转变为膜扩散和颗粒内扩散相结合，并将达到吸附平衡所需的时间缩短了15.8%~21.7%。平衡吸附容量（ q _e ）存在显着的种间和化学间变异，顺序为大豆 > 玉米，3-NFla > 9-NAnt。 GQD 的出现使大豆的 9-NAnt 和 3-NFla 的q _e值增大了 22.8% ，而大豆为 28.7%，大豆为16.2%。玉米分别为3%，这主要归因于GQDs引起的NPHA吸附表面积的扩大以及NPAH分子的-NO ₂和NPAH分子的官能团（例如-COOH、-OH）之间更强的静电相互作用。 GQD 外表面。并且，按3-NFla>9-NAnt顺序的不同增强程度可能是通过空间效应来解释的，空间效应导致3-NFla的-NO ₂更容易接近GQD的外表面。总之，GQD 增加了作物叶片表面 NPAH 的保留，可能威胁作物安全。