Hexachlorobutadiene (HCBD) has been listed as persistent organic pollutants (POPs) in the Stockholm Convention, and is now drawing more and more research interests. However, the understanding on its bioaccumulation, especially in plants, is still very limited. In this work, the behavior of HCBD in aqueous solution and pumpkin seedlings were studied through in-lab hydroponic exposure experiments. It was found that 69% HCBD volatilized from water to atmosphere after one day exposure, and only 1% remained in the solution after four days. The high volatility might be the main cause for low HCBD levels in the aqueous environment. Though a great amount of HCBD volatilized into the atmosphere, only a small proportion of airborne HCBD was captured by the leaves and stems of the blank pumpkin. The translocation of HCBD from the leaves to the bottom roots, as well as the release from roots to water, was detected. For the exposure groups, pumpkin absorbed HCBD from both hydroponic solution and air by roots and leaves, respectively. The concentration of HCBD in exposed pumpkin roots linearly increased with the continuous addition of HCBD in the exposure system. Upward translocation from roots to leaves and downward translocation from leaves to roots existed simultaneously in the exposed pumpkin. However, the concentrations of HCBD in leaves, stems and roots in exposure group were much higher than that of blank plant controls, suggesting little contribution of the airborne HCBD in the hydroponically exposed pumpkin. Lipid contents did not show obvious effects on the bioaccumulation and biodistribution of HCBD in pumpkin, indicating that the translocation of HCBD within the pumpkin might be an active process. This study provided new findings on the environmental behavior of HCBD, which would be helpful for understanding their exposure risks.

中文翻译：

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暴露于水后南瓜幼苗中六氯丁二烯的生物累积

六氯丁二烯（HCBD）在《斯德哥尔摩公约》中被列为持久性有机污染物（POPs），目前正引起越来越多的研究兴趣。但是，对其生物蓄积，特别是在植物中的生物蓄积的理解仍然非常有限。在这项工作中，通过实验室内水培暴露实验研究了六氯丁二烯在水溶液和南瓜幼苗中的行为。发现在暴露一天后，有69％的六氯丁二烯从水挥发到大气中，而在四天后，溶液中仅残留了1％的六氯丁二烯。高挥发性可能是水性环境中六氯丁二烯含量低的主要原因。尽管大量六氯丁二烯挥发到大气中，但空白南瓜的叶和茎却捕获了少量的空气传播六氯丁二烯。六氯丁二烯从叶子到根部的易位，以及从根到水的释放。对于接触人群，南瓜分别从根部和叶片从水培溶液和空气中吸收六氯丁二烯。随着暴露系统中不断添加六氯丁二烯，暴露的南瓜根中六氯丁二烯的浓度线性增加。从根到叶的向上易位和从叶到根的向下易位在暴露的南瓜中同时存在。然而，暴露组的叶，茎和根中六氯丁二烯的浓度要比空白对照高得多，这表明在水培暴露的南瓜中，空气传播的六氯丁二烯的贡献很小。脂质含量对南瓜中六氯丁二烯的生物积累和生物分布没有明显影响，表明南瓜内六氯丁二烯的易位可能是一个活跃的过程。这项研究提供了关于六氯丁二烯环境行为的新发现，这将有助于了解六氯丁二烯的暴露风险。