Hexachlorobutadiene (HCBD) has been listed as a persistent organic pollutant (POP) in the Stockholm Convention, and is now drawing more and more research interest. However, the understanding of its bioaccumulation, especially in plants, is still very limited. In this work, the behavior of HCBD in aqueous solution and pumpkin seedlings was studied through in-lab hydroponic exposure experiments. It was found that 69% of HCBD volatilized from water to the atmosphere after one day of exposure, and only 1% remained in the solution after four days. This high volatility might be the main cause of the low HCBD levels in aqueous environments. Although 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 seedling controls. The translocation of HCBD from the leaves to the bottom roots, as well as its release from the roots into the water, was detected. For the exposure groups, the pumpkin seedlings absorbed HCBD from both the hydroponic solution and the air via the roots and leaves, respectively. The concentration of HCBD in the exposed pumpkin roots linearly increased with the continuous addition of HCBD into the exposure system. Upward translocation from the roots to the leaves and downward translocation from the leaves to the roots existed simultaneously in the exposed pumpkin seedlings. However, the concentrations of HCBD in the leaves, stems and roots in the exposure group were much higher than those of the blank plant controls, suggesting little contribution from the airborne HCBD in the hydroponically exposed pumpkin seedlings. The lipid content did not show obvious effects on the bioaccumulation and biodistribution of HCBD in the pumpkin seedlings, indicating that the translocation of HCBD within the pumpkin seedlings might be an active process. This study provided new findings on the environmental behavior of HCBD, which will be helpful for understanding the 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》中已被列为持久性有机污染物（POP），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。发现暴露一天后，六氯丁二烯从水中挥发到大气中的比例为69％，四天后溶液中仅残留了1％的六氯丁二烯。这种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，但空白南瓜幼苗对照的叶子和茎干仅捕获了少量的空气传播六氯丁二烯。检测到六氯丁二烯从叶子到根部的易位以及从根部向水中的释放。对于暴露人群，南瓜幼苗从水培溶液和空气中都吸收了六氯丁二烯通过根和叶分别。随着向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。在裸露的南瓜幼苗中，从根到叶的向上易位和从叶到根的向下易位同时存在。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幼苗中，空气传播的六氯丁二烯的贡献很小。脂质含量对南瓜幼苗体内六氯丁二烯的生物积累和生物分配没有明显影响，表明六氯丁二烯在南瓜幼苗内的易位可能是一个活跃的过程。