中国内陆流域地表水体光电化学特征研究

Study on photoelectrochemical characteristics of surface water in China’s inland valley

太阳辐射是自然界中最主要的能量来源.目前人们对自然界利用太阳能途径的认识主要集中于具有生物光采集系统(如叶绿体)的光合作用,而对于非生物光采集系统是否广泛存在于地表水体中仍不清楚.本研究通过测定全国范围内151个地表水样光生电子的能力,绘制了中国内陆流域地表水体光电化学特征图谱.通过利用XPS、XRD和EEM等手段表征水样悬浮态和溶解态物质组成,揭示了地表水体光电化学活性来源及其影响因素.结果显示,我国地表水体普遍存在光电化学活性.按生物质换算,我国地表水体光生电子每年可转化生物质当量约为1.4×10^(3)~1.1×10^(4)万t葡萄糖,相当于光合作用固碳总量的0.51%~4.02%.地表水体的光电流大小与光强和光敏物质浓度呈正相关,相关系数分别达到0.99和0.99.水体的光电化学活性主要来源于悬浮态物质,其贡献度大于60%,与含Ti或含S的半导体矿物丰度呈正相关;而溶解态物质贡献较小(<40%),其光电化学成分主要为溶解性有机质,并与腐殖酸类或富里酸类物质浓度呈正相关.本研究为自然界微生物光电能营养作用的发生提供线索,同时也为量化自然地表水体太阳光引发的生物或非生物能量来源提供依据.

Solar radiation is the major source of energy in nature.At present,the understanding of solar energy utilization in nature mainly focuses on photosynthesis with biologic light harvesting systems(e.g.,chloroplasts).However,the nonbioligcal light harvesting system in natural surface water has yet to be recognized.In this work,the photoelectron-generating capacity of 151 surface water samples throughout the China were measured to map the photochemical characteristics of surface water in inland valleys of China.XPS,XRD and EEM were used to characterize the suspended and dissolved substances in water samples.It demonstrated that the photoelectric conversion was a fundamental and widespread feature for surface water.The estimated biomass equivalent driven by photoexcited electrons from the surface water of China was 1.4×10^(3)~1.1×10^(4)million tons of glucose per year,which was 0.51%~4.02%of that from photosynthesis.The ability of photoelectric conversion was positively correlecting to the light intensity and the concentration of light harvesting substrates,with correlation coefficients of 0.99 and 0.99,respectively.The suspended substance played dominant role(>60%)on the photoelectric conversion of surface water and its ability of photoelectric conversion was decided by the contents of Ti or S-containing substances.Whileres,the contribution of dissolved substances was lower than 40%and decided by the concentration of humic-or fulvic-like substrate.This study provides a key clue for indicating the occurrence of photoelectrophy in nature,and helps quantify the biotic or abiotic energy sources triggered by sunlight in natural surface water.