基于X射线荧光成像技术研究海洋微藻对重金属吸收的机理

Water pollution has a long history along with the existence of mankind. It seems very convenient to dispose all kinds of liquid and solid wastes into aquatic systems. Nowadays, wastewater released from industrial and municipal sources is posing serious challenges to the aquatic environments, and becomes a global problem need to be solved in sustainable ways. The released wastewater rich in organic compounds and inorganic chemicals such as nitrates and phosphates can introduce eutrophication, and metals can inhibit the phytoplankton growth, metabolic activity, toxic to aquatic organisms and human being through bio-accumulation. Microalgae have been proved in many studies that have the ability to absorb metals from environment. .In this study, we will investigate the effects of Mn, Ni, Cu, Cd and Zn, single or combined, on the growth, photosynthesis performance, and biochemical compositions. By using high resolution X-ray fluorescent image system, investigate the mechanism of heavy metals uptake and accumulation by microalgae and the dynamic of cellular metal distribution, demonstrate the extracellular trace metals deposition location, their status after bound to functional groups on cell wall, and intracellular distribution, transportation and accumulation. Additionally, by studying the effects of metals on microalgal cellular biochemical composition changes, especially lipid production, will explore the potential of lowering the cost of microalgal heavy metals bioremediation, which is still not economically feasible yet..There have extensive studies of micoralgae used in bio-monitoring or bioremediation purposes, but the mechanism of the trace metals uptake, transportation and accumulation with and within the microalgal cells is still unclear. Meanwhile, the cellular metal allocation related to different cellular metabolic processes, such as photosynthesis performance, nutrient incorporation, and antioxidative defenses, must be better understood. This work will lead to effective use and accelerate the development of microalgae as effective metal biosorbents as well as biodiesel producers.

工业化与城市化快速发展大量引入的重金属元素除了抑制水生生物生长，在水生生物体内富集，还对初级生产力和生态系统结构产生深远复杂影响，海洋污染已成为全球性环境热点问题。本项目将针对多种微量元素（Mn、Ni、Cu、Cd和Zn），单一或复合存在时对海洋微藻细胞生理、光合作用、生物化学组成等主要生理指标的影响，完善复合重金属联合作用理论；利用X射线荧光成像技术，对微藻细胞吸附金属元素机理和分布动力学进行高解析度分析，研究微量元素在胞外沉积部位，在细胞壁上与功能基团的吸附和状态，及对其在胞内分布、输送及富集进行研究；研究重金属元素对微藻细胞内脂类含量和构成的影响，探讨吸附、富集重金属元素同时生产微藻燃料的前景。现阶段，关于重金属污染物对海洋微藻生物效应及利用微藻除污或开发新能源已有不少学者进行了研究，但藻细胞吸附富集重金属元素机理及优化条件仍需更多研究，这将为进一步探讨该研究在工业中应用提供理论依据。

海洋污染已经成为全球性环境热点问题，尤其以发展中国家为甚。有毒重金属可能导致对水生生物生长的抑制，造成重金属在水生生物体内富集，并对初级生产力和生态系统结构产生深远复杂影响。从生态意义上来说，探究重金属对微藻的毒性具有非常重要的价值。另外，微藻具有产油能力，尤其是海藻中的硅藻产油能力较强。在重金属胁迫条件下，微藻的产油能力可能会被提高。所以，从工程意义上来说，相关研究也非常必要。.本项目完成了五种不同藻株三角褐指藻，威氏海链藻，强壮前沟藻，杜氏盐藻以及舟形藻受铜、锌、镉三种单一重金属胁迫条件下，生理生长状况及产油能力的研究。研究发现当舟形藻和三角褐指藻对金属的耐受能力最强；单一重金属Cd2+、Cu2+和Zn2+在低浓度时显著促进舟形藻生长和光合作用，而高浓度时抑制生长和光合作用，导致细胞密度降低。.以舟形藻为研究对象，研究了不同浓度重金属Cd2+、Cu2+和Zn2+在复合时对舟形藻在生长生理和油脂积累的影响，探索了利用复合重金属促进其油脂生产的可行性。重金属Cu2+与Cd2+或Zn2+复合后对舟形藻生长生理的抑制产生协同作用；高浓度复合重金属对光合作用的抑制可能与活体荧光的抑制有一定关系；一定情况下，当舟形藻的生理代谢被较高浓度的重金属抑制时，舟形藻可以调节自身代谢合成并积累更多的油脂，但当重金属浓度过高时，包括油脂合成在内的生理代谢过程被全面抑制。在后续的研究中，再结合X射线成像技术，以期更大程度的获得金属在细胞内的富集转运过程的理解，揭示细胞吸收富集分布以及输送金属的机理。.本项目还系统地研究了新型纳米污染物的生态毒性，发现金属纳米颗粒能影响产毒赤潮藻塔玛亚历山大藻的生理、生长，还能促进塔玛亚历山大藻中麻痹性贝类毒素（PSTs）总含量的增加，并引起PSTs组成的显著变化。.通过本项目的研究，加深了我们对海洋微藻吸附、富集微量元素机理；研究重金属元素对微藻胞内脂类含量的影响，可为微藻柴油生产提供新的方向和理论依据。

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