摘要
地球表层是一个极为复杂的开放系统,其中所充满的阳光、大气、水分、有机酸、无机酸/盐、矿物质和微生物等彼此之间无时无刻不在发生着人们尚未充分认识到的多种自然作用。本文采用环境矿物学、半导体物理学与光电化学等交叉学科研究手段,在我国南方红壤、西南喀斯特和西北戈壁等典型陆地生境中,发现直接暴露于太阳光下的土壤/岩石表面广泛发育有几十纳米到数百微米厚度的铁锰氧化物"矿物膜";详细研究了铁锰氧化物"矿物膜"中矿物组成及其精细结构特征,发现半导体性能优异的水钠锰矿普遍存在,其晶体结构中富含促进其光催化功能的稀土元素Ce。在这些生境中,矿物岩石表面所包覆的铁锰氧化物"矿物膜"总是朝着太阳光发育,岩石背面却不出现"矿物膜",揭示出太阳光照射下的地球陆地表面普遍存在的"矿物膜"与太阳光有着直接的响应关系。光电化学测试结果显示,天然"矿物膜"具有较好的日光响应性能,由其制成的电极在可见光照射下皆能产生明显的光电流,而不含铁锰氧化物矿物的岩石基质样品及石英、长石等矿物样品几乎不产生光电流,表明"矿物膜"光电流的产生主要与铁锰氧化物有关。进一步测得"矿物膜"中主要铁锰氧化物的禁带宽度均小于2. 5eV,证明其均为对可见光具有广泛而良好吸收的天然半导体矿物。以全球日光平均辐照强度100mW/cm^2计以及全球典型生境中"矿物膜"分布面积估算,全球"矿物膜"吸收太阳能等效为生物质能的最大量与2017年度全球糖类产量(1. 92亿吨)相当。铁锰氧化物"矿物膜"不仅存在于陆地地表,还存在于海洋透光层中。可以认为地表"矿物膜"是地球上分布最广的天然"太阳能薄膜",从功能上"矿物膜"相当于继地核、地幔和地壳之后的地球第四大圈层,事实上构成了地球"新圈层",也是地球在太阳光能量驱动下发
The terrestrial system on Earth surface is a very complicated open system,where the sunlight,air,water,organic acids,inorganic acids/salts,minerals and microorganisms are always closely interacting with each other. And these natural interactions still await further scientific investigations. Based on the cross-field research methods of environmental mineralogy,semiconducting physics and photoelectron-chemistry,this study revealed a ferromanganese"mineral membrane"widely developed on rock and soil surfaces and directly exposed under sunlight,in such various typical terrestrial environments as Gobi desert,karst regions and red soils areas. This"mineral membrane"is usually of several tens of nanometer to hundreds of micrometer in thickness. The fine structural characteristics of the Mn oxides in"mineral membrane"were investigated,and the prevalent existence of layered-type birnessite was proved. Besides,the rare earth element Ce was found to be structurally-correlated with birnessite in "mineral membrane",which could promote its semiconducting function. The "mineral membrane"is always developed on the surface sides of rocks rather than the reverse sides,indicating a direct correspondence with sunlight exposure. As revealed by photoelectron-chemistry experiments,electrodes made of natural"mineral membrane"powders could generate remarkable photocurrents under illumination of visible light,whereas the rock substrates and quartz and feldspar minerals could barely achieve that. These results indicated the generation of photocurrent was mainly due to the Fe-and Mn-oxides. Further measurements showed the bandgap of main Fe-and Mn-oxides in"mineral membrane"are all below 2. 5 eV,suggesting they are all visible light responsive semiconducting minerals. Based on the worldwide average solar irradiation intensity of 100 mW/cm2 and the global distribution areas of"mineral membrane",it was estimated that the energy mass of solar energy converted to biomass energy by "mineral membrane"could parallel with the global sugar productio
作者
鲁安怀
李艳
丁竑瑞
王长秋
LU AnHuai;LI Yan;DING HongRui;WANG ChangQiu(School of Earth and Space Sciences,Peking University,MOE Key Laboratory of Orogenic Belts and Crustal Evolution,Beijing Key Laboratory of Mineral Environmental Function,Beijing 100871,China)
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2019年第1期119-128,共10页
Acta Petrologica Sinica
基金
科技部"973"项目(2007CB815600
2014CB846000)
国家自然科学基金重点项目(41230103
91851208)
国际合作重点项目(41820104003)
优秀青年基金项目(41522201)和面上项目(41872042)联合资助
