利用活体固相微萃取技术研究短链和中链氯化石蜡在小麦体内的吸收转运和累积

Short-chain chlorinated paraffins (SCCPs) are persistent organic pollutants (POPs), and medium-chain chlorinated paraffins (MCCPs) have been intensively manufactured and applied as the substitutes of SCCPs. Nevertheless, the characteristics and mechanisms of the uptake of SCCPs and MCCPs have been rarely reported. In this study, wheat (Triticum aestivum L.) was selected as the model plant, and the in vivo SPME was developed for SCCPs and MCCPs tracing their translocation, accumulation and distribution in Triticum aestivum L. The relationships of SCCPs and MCCPs uptake with their concentrations, chain lengths, and chlorine contents were investigated, and the key factors were identified. The adsorption of SCCPs and MCCPs by excised root was conducted to explore the passive uptake of SCCPs and MCCPs. Meanwhile, the active uptake of SCCPs and MCCPs was tested with the aid of low temperature treatment, and inhibition of energy metabolism and ATPase activities of plasma membrane. In combination with transmission electron microscope (TEM) and vacuum infiltration centrifugation, the mechanisms of SCCPs and MCCPs uptake by Triticum aestivum L. were discussed. Totally, the results would improve our understanding of plant uptake of non-ionic organic pollutants and give hints on comprehensive ecological risk assessment of SCCPs and MCCPs.

短链氯化石蜡是一类新型持久性有机污染物，中链氯化石蜡作为短链氯化石蜡的替代品被大量生产和使用。目前，对于植物吸收短链和中链氯化石蜡的特征及机制还未明确。本项目拟以小麦为受试作物，拟建立和优化活体固相微萃取技术（in vivo SPME），实现小麦体内短链和中链氯化石蜡的活体采样及检测；并结合盆栽试验，研究他们在小麦体内的迁移、累积和分布规律，建立其与土壤性质、氯化石蜡浓度、碳链长度及氯原子取代数的关系，揭示主控因子。采用离体根试验研究根系吸收短链和中链氯化石蜡的被动过程；利用能量代谢抑制、质膜酶活性抑制和低温处理等手段考察根系吸收短链和中链氯化石蜡与主动运输的关系；并结合透射电镜（TEM）和真空渗透离心法等技术手段，综合探讨小麦根系吸收短链和中链氯化石蜡的方式和途径，明确关键影响因素。研究结果为加深植物吸收非离子型有机污染物的理论认识及评估此类污染物的生态风险提供科学依据。

短链氯化石蜡（short-chain chlorinated paraffins，SCCPs）是一类新型持久性有机污染物，中链氯化石蜡（medium-chain chlorinated chlorinated paraffins，MCCPs）作为短链氯化石蜡的替代品被大量生产和使用。他们在我国农田土壤中普遍存在。研究植物对短链和中链氯化石蜡的吸收累积对于评估土壤中这两类污染物的风险及进行植物修复具有重要意义。本项目以我国主要粮食作物小麦为受试植物，研究小麦吸收转运和累积SCCPs和MCCPs的特征和规律。首先，基于自动化纤维萃取SPME系统，建立了水样中短链和中链氯化石蜡快速高通量的样品前处理方法，该方法可以同时处理96个水样，共耗时4个小时，提高了样品检测的效率，方法定量限为0.01 mg/L。利用土壤盆栽试验，明确了小麦吸收累积SCCPs和MCCPs的特征。生物有效性是影响小麦根系吸收SCCPs和MCCPs的关键因素。SCCPs和MCCPs从环境介质（土壤或水）进入小麦根系的能力不依赖碳链长度和氯原子个数，另一方面，SCCPs和MCCPs从小麦根系向茎叶转运时，表现出碳链长度小的和氯原子个数少的同系物更易于向茎叶转运。同时，考察了小麦苗期常用的植物生长调节剂（复硝酚钠、芸苔素内酯、三十烷醇和14-羟基芸苔素甾醇）对小麦吸收转运SCCPs和MCCPs的影响。芸苔素内酯和14-羟基芸苔素甾醇显著降低了根系对MCCPs的吸收，14-羟基芸苔素甾醇显著降低了MCCPs从根系向茎叶的转运。复硝酚钠显著增加了根系对SCCPs吸收，芸苔素内酯、三十烷醇和14-羟基芸苔素甾醇显著降低了根系对SCCPs的吸收。最后，利用水培试验，开展了小麦吸收累积SCCPs和MCCPs的动力学特征研究，以及结合剪根、避光、低温处理等手段，初步探明了小麦根系吸收SCCPs和MCCPs的方式，蒸腾拉力是小麦根系吸收SCCPs和MCCPs的一个主要驱动力。不同浓度下，小麦根系吸收SCCPs和MCCPs的速率符合Michaelis-Menten方程，表明主动运输也参与了根系对SCCPs和MCCPs的吸收。研究结果可为氯化石蜡的生态风险评估提供依据。基于本项目试验结果，我们提出了利用植物生长调节剂调控植物吸收累积有机污染物的设想，为强化土壤中有机污染物的植物修复提供新思路。后续将针对这一设想开展相关研究。