College of Environment and Resource, Shanxi University, Taiyuan 030006, China; Department of Environmental Sciences, University of California, Riverside, CA 92521, USA; Guangzhou Key Laboratory of Environmental Exposure and Health, School of Environment, Jinan University, Guangzhou 510632, China.
College of Environment and Resource, Shanxi University, Taiyuan 030006, China.
Ecotoxicol Environ Saf. 2018 Oct 30;162:10-16. doi: 10.1016/j.ecoenv.2018.06.059. Epub 2018 Jun 26.
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 cm 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) with the sequence of soybean > maize and 3-NFla > 9-NAnt. The occurrence of GQDs enlarged the q 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 -NO 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 -NO 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.
硝多环芳烃（NPAHs）是对生态系统具有更高毒性效应的多环芳烃衍生物，其在作物系统中的分配构成了通过饮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法并结合石墨烯量子点（GQDs）作为荧光探针原位检测活体大豆和玉米幼苗叶片表面吸附的 9-硝基蒽（9-NAnt）和 3-硝基荧蒽（3-NFla）的新方法。两种吸附 NPAHs 的原位定量检测限范围为 0.8 至 1.6ng/斑点（斑点表示测定单元，每个斑点为 0.28cm）。使用新方法，原位研究了 GQDs 对活体大豆和玉米叶片表面对单个 9-NAnt 和 3-NFla 吸附的影响。GQDs 的存在改变了从单一膜扩散到膜扩散和颗粒内扩散相结合的吸附机制，并将达到吸附平衡所需的时间缩短了 15.8-21.7%。在平衡吸附容量（q）方面，存在明显的种间和种内化学变异性，顺序为大豆>玉米和 3-NFla>9-NAnt。与大豆相比，GQDs 将 9-NAnt 和 3-NFla 的 q 值分别扩大了 22.8%和 28.7%，与玉米相比，GQDs 将 9-NAnt 和 3-NFla 的 q 值分别扩大了 16.2%和 20.3%，这主要归因于 GQDs 诱导的用于吸附 NPAHs 的表面积扩大和 NPAH 分子的-NO 与 GQDs 外表面的官能团（例如，-COOH，-OH）之间的更强静电相互作用。并且，3-NFla>9-NAnt 的变化增强程度可能可以用空间位阻效应来解释，这使得 3-NFla 的-NO 更容易接近 GQDs 的外表面。总之，GQDs 增加了 NPAHs 在作物叶片表面的保留，可能对作物安全构成威胁。
