低温等离子体降解微囊藻毒素机理及其生态安全性研究

Microcystins (MCs) pollution caused by harmful algal blooms imposes serious threat on the safety of drinking water. Due to the chemical stability of microcystins，the conventional water treatment methods such as coagulation, sedimentation and filtration plus oxygen cannot destroy them readily. Existing physical, chemical and biological processing techniques have also some limitations, or lack of ecological safety evaluation, so they are not widely used. In our laboratory we have found that discharge plasma can destroy or degrade peptides efficiently. Microcystins belong to a class of cyclic peptides containing seven amino acid residues. Our preliminary results indicated that discharge plasma can also degrade MCs efficiently. Some intermediates were found during the degradation. Because this non-thermal plasma treatment can produce large amounts of various free radicals, we postulate that the free radicals play an important role in the degradation process. But what and how the free radicals play the role remain elusive, and no study through this treatment method has been reported. The effect of external environment conditions on the degradation has not been reported, either. Therefore, this project will conduct the study of the degradation kinetics and dynamics of microcystins through the non-thermal plasma oxidation. The roles of free radicals, the reaction pathways for producing intermediates, and the influence of environmental factors on degradation efficiency will be investigated in detail. Also, the ecological safety will be evaluated by the method based on Caenorhabditis elegans model. This work will provide a new approach to cyanobacterial toxins pollution control.

蓝藻水华引起微囊藻毒素污染严重威胁人类饮用水安全。由于微囊藻毒素化学性质稳定，采用常规水处理方法，如：混凝沉淀、过滤加氧等技术均不能将其有效降解或去除。光催化降解、超滤、生物降解等方法也各具局限性，且缺乏生态安全性评价而未被广泛使用。本实验室前期研究发现放电等离子体作用于生物体可以损伤或降解多肽分子。微囊藻毒素一类含有七个氨基酸的环肽，初步研究表明放电等离子体能有效将其降解，并检测到一些降解中间产物。低温等离子体处理产生大量自由基，推测自由基在毒素降解过程中起重要作用，但何种自由基如何起作用，中间产物形成途径等问题尚不清楚，而放电处理藻毒素的方法以及各种环境条件对降解影响也尚未见报道。为此，本项目将仔细研究低温等离子处理微囊藻毒素的降解动力学、降解途径和机理，以及各种实际水体环境因子对降解效率的影响，并用秀丽隐杆线虫对该方法生态安全性进行评价，从而为蓝藻毒素污染治理提供新方法和应用基础。

微囊藻毒素污染使人类饮用水安全遭受严重威胁。本项目开展低温等离子体降解微囊藻毒素的机理及其生态安全性进行研究，详细研究微囊藻毒素降解动力学、水体环境因子对降解效率的影响和毒素降解机理，并对降解产物进行了生态安全性检测。降解动力学研究显示，低温等离子体降解微囊藻毒素的速率符合一级降解速率，并随pH值的升高而降低，增加溶液中总氮和总磷的含量可以改变其降解速率。实际水体（藻类培养基，巢湖藻华发生时含有蓝藻毒素的水体）中的降解速率明显低于纯水中的速率，并合理解释了降解速率变化的原因。降解机理研究结果显示，羟自由基在毒素降解过程中其主要作用。羟自由基通过在蓝藻毒素分子中双键位置加成，取代等反应使毒素分子发生羟化反应，进一步发生酮基化，脱羧化反应使毒素分子开环降解，最终降解成了小分子化合物。生态安全性检测结果显示微囊藻毒素的降解产物具有生态安全性。另外本项目还探索性研究了等离子体对微囊藻细胞的的损伤和杀灭作用以及等离子体发生时伴随发射的紫外光在降解污染物中的作用。通过本项目的研究，为等离子体水处理技术包括降解蓝藻毒素在内的降解水体污染物提供了详实的理论和实验基础。