研究生知识库

A series of recent progress on the study of the carbon sink of rock weathering have been made with the increase of CO2 concentration in the world. A lot of research shows that karst process plays an enormous role in carbon sinks. Furthermore, metabolic activity of microbes plays a positive role in the carbon sinks of karst. Microalgae as the oldest and the most important primary productivity, interaction effect between the growth of microalgae and the rock weathering and the regulatory mechanism are discussed in this thesis. The study results are extended to geochemical environment background. This work has profound implications to further discuss the geological significance of microbe’s corrosion and effects on the world's carbon cycle.It can provide scientific basis in search of “missing carbon sink” to study the silicate rock corrosion of microalgae (using olivinite as an example) and the discussion on the silicate rock corrosion effect of microalgae and the changes of microalgae carbon sink during the process of silicate rock corrosion and weathering. Finally, a technology of biology carbon sinks addition. Acetazolamide (AZ, for short) is one of inhibitors of CAex and the CAex activity can be specifically inhibited by AZ. The 4, 4-diisothiocyanatostilbene-2,2-disulfonate (DIDS, for short) is the inhibitor of anion channel and the activity of anion channel can be specifically inhibited by DIDS. The metabolic pathways of inorganic carbon are affected by the two inhibitors. Thus，olivinite biological corrosion effect of microalgae and its carbon sink are studied by adding DIDS and AZ in the thesis. Chlamydomonas and chlorella are chosen as experimental materials in this thesis. Mg-olivinite corrosion weathering has been studied by controlling different conditions, for example, the two kinds of microalgae in nutrient-rich and nutrient-poor environment, adding AZ, adding DIDS and different pH values. Meanwhile, the calculation method of inorganic carbon utilization share was used to probe into the response mechanism of carbon sink effect of microalgae in above different conditions. Following principal achievements have been obtained in this thesis:(1) Calculation method of stable carbon isotope fractionation value has been established during the process of CO2 assimilation of microalgae in this thesis. Additionally, the calculation method was used to study the inorganic carbon utilization share. The study found that the share of HCO3- way is usually very high in the three kinds of karst lake microalgae named Chlamydomonas reinhardtii(C.R), Chlorella pyrenoidosa(C.P) and compound algae collected from surface water of Hongfeng Lake. The result shows that the HCO3- way is mainly the inorganic carbon utilization share of microalgae in the karst lake. It is the result of survive strategy choices of microalgae in a long-term lack of CO2 aquatic environment.(2) Corrosion weathering of olivinite promotes biological carbon sink function of microalgae; Microalgae all increase amount of dissolution and weathering, whether external environment lack of magnesium. Microalgae may use ions produced from olivinite corrosion to provide the nutriment for its own life and promote its growth. In this way, biological carbon sinks are added. Chlamydomonas reinhardtii can still grow normally and keep higher biological carbon sink function in nutrient-poor external environment. Two kinds of microalgae can be a great boost for dissolution and weathering of olivinite, whether external environment lack of magnesium. So olivinite dissolution function of microalgae may not change dramatically with the change of external environment. According to previous estimate model of global carbon sink, rock chlorella microbes of all river watersheds in Karst weathering areas are ignored. It leads to carbon sink effect of rock weathering is underestimated. Thus, this conclusion provides a new direction to find the “missing carbon sink”. (3) Biological carbon sink of may be added when microalgae is restrained; Meanwhile, discover CAex activity is the important impact factor of corrosion weathering of olivinite and promote the corrosion weathering function. The HCO3- way produced from the CAex catalysis may be restrained when microalgae is restrained. So the growth of microalgae reduces and the demand for required carbon source decrease, thus reducing the low carbon source stress and biomass increase and biological carbon sink of microalgae increase. CAex activity may be especially restrained by AZ. Biological corrosion function of microalgae may be restrained when the HCO3- way produced from the CAex catalysis is restrained. The results show that CAex of microalgae plays a great role in dissolution and weathering of olivinite.(4) DIDS can promote the biomass growth of microalgae and add the biological carbon sink; Anion channel is the important positive impact factor for the olivinite dissolution and weathering of microalgae. A clear anion channel plays a promoting role in olivinite dissolution and weathering. Biological corrosion function of microalgae is restrained by the DIDS.(5) The share variation values of HCO3- utilization way among the two kinds of microalgae is different when anion channel is restrained by DIDS. The reason of phenomenon relates closely with the CAex activity of this two kinds of microalgae. Chlorella with low activity of CAex shows higher share values of HCO3- utilization way when it is restrained by DIDS. It shows that HCO3- utilization way of CAex catalysis of microalgae start to activate at the moment. However, the share values of HCO3- utilization way decrease obviously when chlamydomonas reinhardtii is restrained by DIDS. The result shows that the CAex activity of chlamydomonas reinhardtii is high and its catalytic HCO3- utilization way has been express fully.(6) In the case of external pH change, dissolution and weathering of olivinite may be restrained while adding microalgae. This result is not inconsistent with the conclusion that the microalgae growth can promote to dissolution and weathering of olivinite. The main reason is that this phenomenon is related to microalgae biomass. The microalgae biomass during experimental treatment pH reduces compared with initial value, which should lead to reductions in biological corrosion of microalgae for olivinite. Microalgae may restrain olivinite corrosion to accommodate life action with changed pH during the collapse of the microalgae. The growth of microalgae is influenced by many factors in field akes. If impact of the growth of microalgae is ignored in estimating corrosion and weathering of silicate rocks, weathering carbon sink would be underestimated or over estimated.(7) The variation share of the inorganic carbon utilization way is mainly related with pH change. The share of HCO3- utilization way of chlamydomonas reinhardtii gradually decreases with the increase in pH value. However, the share of HCO3- utilization way of chlorella first rise and then drop. This rule is not changed by adding olivinite and shows that the share of the inorganic carbon utilization way is mainly related with pH value. 

随着全球CO2浓度不断上升的，科学家对岩石风化碳汇研究取得一系列进展，大量研究表明：岩溶过程有巨大的碳汇作用，其中微生物通过一系列的生命代谢活动对岩溶碳汇起到积极作用。微藻作为地球上最古老、最重要的初级生产力，对“微藻生长受岩石风化影响、其对岩石风化作用的影响及其调节机制”进行研究，把微环境的研究成果扩大到大的地球化学环境中，更近一步讨论微生物溶蚀的地质意义，对整个碳循环的影响将具有深远的意义。开展微藻对硅酸盐岩（以橄榄岩为例）生物溶蚀的研究，探讨微藻对硅酸盐岩溶蚀效应的影响及其硅酸盐岩溶蚀过程中对微藻碳汇的影响，为寻找 “遗失碳汇”提出科学依据，发掘生物增汇技术。乙酰唑胺（Acetazolamide, AZ）是碳酸酐酶胞外酶（CAex）抑制剂，能特异性抑制胞外碳酸酐酶的活性。4,4’-二异硫氰-2,2’-二黄酸芪（4,4-diisothiocyanatostilbene-2,2-disulfonate, DIDS）能特异性抑制微藻的阴离子通道。两种抑制剂影响着微藻的无机碳代谢途径，因此论文通过向实验处理中添加DIDS、AZ以探究微藻对橄榄岩的生物溶蚀效应及其过程中的碳汇效应。本论文选取莱茵衣藻、蛋白核小球藻两种微藻为实验材料，通过实验室控制的方法，研究了贫富镁营养环境中两种微藻对含镁较高的橄榄岩的溶蚀风化作用、AZ影响下微藻对橄榄岩的溶蚀风化作用、DIDS影响下微藻对橄榄岩的溶蚀风化作用、不同pH 梯度下微藻对橄榄岩的溶蚀风化作用，同时利用无机碳利用途径份额的计算方法探究了微藻在各个处理情况下碳汇效应的响应机理。得到以下的研究成果：(1) 本论文建立了微藻CO2同化过程中的稳定碳同位素分馏值方法，并以此探讨了微藻的无机碳利用份额。发现莱茵衣藻、蛋白核小球藻，及野外红枫湖混合藻三种岩溶湖泊微藻的碳酸氢根离子途径份额很高，表明在喀斯特岩溶湖泊中，微藻的无机碳利用途径主要是以碳酸氢根离子途径为主，这是微藻在长期缺乏CO2水体环境中，进行了生存策略的选择的结果。(2) 橄榄岩的溶蚀风化作用促进了微藻的生物碳汇的增加，并且不管外界环境是否缺镁，微藻都会增加橄榄岩的溶蚀风化量。微藻能吸收利用橄榄岩溶蚀风化产生的离子，为自身生命活动提供营养物质，促进其生长，增加微藻的生物碳汇作用；其中莱茵衣藻的生长情况在外界贫镁营养时依然保持正常的生长，保持较高的生物碳汇作用。无论外界条件是不是缺镁，两种微藻都能极大的促进橄榄岩的溶蚀风化作用，所以微藻对橄榄岩的溶蚀作用并不会因为外环境的变化而急剧变化。结合前人对全球碳汇的估算模型，忽略岩溶风化地区各水体流域中微生物的对岩石的溶蚀作用，会使得岩石风化的碳汇效应被低估，此结论为“遗失碳汇”的寻找带来新的方向。(3) 微藻受到AZ作用时生物碳汇增加；同时微藻的CAex活性是微藻对橄榄岩溶蚀风化作用的重要影响因子，对橄榄岩溶蚀风化作用为促进作用。微藻受到AZ抑制，由CAex催化的碳酸氢根离子途径受到抑制，此时微藻生长所需的镁离子含量降低，受到贫镁胁迫减少，导致生物量增加，微藻的生物碳汇增加。胞外碳酸酐酶（CAex）活性会受到AZ的特异性抑制，由CAex催化途径的碳酸氢根离子途径受到抑制，此时微藻的生物溶蚀作用受到抑制，表明了微藻CAex对橄榄岩溶蚀风化有极大的促进作用。(4) DIDS能促进微藻的生物量的增加，增加微藻的生物碳汇；同时阴离子通道是微藻对橄榄岩的溶蚀风化作用的重要影响因子，微藻的阴离子通道的畅通对橄榄岩溶蚀风化起到促进作用。微藻在DIDS作用下，对橄榄岩的生物溶蚀作用受到抑制作用。(5) 当微藻阴离子通道受到DIDS抑制时，两种微藻的碳酸氢根离子利用途径份额值变化表现不一致，这与两种藻的胞外碳酸酐酶活力，密切相关。胞外碳酸酐酶活性较弱的小球藻，受到DIDS抑制时反而表现出更高的碳酸氢根离子利用途径份额值，说明此时小球藻的胞外碳酸酐酶催化的碳酸氢根离子作用途径启动。然而衣藻受到DIDS抑制时，碳酸氢根离子利用途径份额值明显降低，这表明衣藻的胞外碳酸酐酶活性高，其催化的碳酸氢根离子利用途径作用已得到完全的表达。(6) 在外界pH值变化的情况下，微藻会抑制橄榄岩的溶蚀风化作用。这并不与微藻生长会促进橄榄岩溶蚀风化的结论相矛盾，出现此现象的原因主要与微藻的生物量相关，pH处理中微藻的生物量均较初始值减少，所以微藻生长带来的对橄榄岩的生物溶蚀作用必将降低。微藻在衰亡期时，微藻为响应水体pH值改变进行的生命活动会抑制橄榄岩的溶蚀，在野外湖泊水体中，微藻的生长会受到各种因素的影响，在估算硅酸盐岩的溶蚀风化作用时忽略微藻生长带来的影响，将会低估或高估风化碳汇。(7)随着pH增加，衣藻的碳酸氢根离子途径利用份额逐渐降低，小球藻的碳酸氢根离子途径利用份额先增加后降低，添加橄榄岩不会改变这种规律，表明微藻的无机碳利用途径份额主要与pH值相关。