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引用本文:张运林,秦伯强,杨龙元.太湖梅梁湾有色可溶性有机物的空间分布及光学行为.湖泊科学,2006,18(4):319-326. DOI:10.18307/2006.0401
ZHANG Yunlin,QIN Boqiang,YANG Longyuan.Spatial distribution and absorption characteristics with relation to fluorescence of chromophoric dissolved organic matter (CDOM) in Meiliang Bay of Lake Taihu. J. Lake Sci.2006,18(4):319-326. DOI:10.18307/2006.0401
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太湖梅梁湾有色可溶性有机物的空间分布及光学行为
张运林, 秦伯强, 杨龙元
中国科学院南京地理与湖泊研究所, 南京 210008
摘要:
2004年3月对太湖梅梁湾有色可溶性有机物(CDOM))的吸收和荧光等光学行为进行研究,并由此探讨了CDOM的空间分布.结果表明,溶解性有机碳(DOC)的浓度在10.48-19.72 mg/L间变化,其均值为13.20±2.79 mg/L)CDOM在280 nm,355 nm和440 nm的吸收系数分别为18.73-31.91 m-1(平均值23.19±4.36 m-1)、4.63-7.14 m-1(平均值5.76±0.91 m-1)、1.45-2.99 m-1(平均值1.92±0.40 m-1))355 nm波长处CDOM的比吸收系数为0.34-0.57 L/(mg·m),平均值0.44±0.06 L/(mg·m))表征CDOM分子大小的比值a(250)/a(365)变化范围为5.05-7.55)355 nm的激发波长、450 nm的发射波长处的荧光值的变化范围0.79-3 04 nm-1(平均值1.69±0.77 nm-1).CDOM吸收系数、DOC浓度、荧光强度的分析显示CDOM浓度呈现从河口往湾内、湾口递减的趋势.CDOM吸收与DOC浓度的相关性随波长的降低而增加,在短波部分存在明显的正相关.355 nm处的荧光值、DOC浓度与CDOM吸收系分别存在如下显著性正相关关系:Fn(355)=0.692(±0.135)a(355)-2.297(±0.786),a(355)=0.233(±0.061)DOC+2.690(±0.816).280-500 nm、280-360 nm、360-440 nm指数函数斜率S值分别为13.86±0.91、18.54±1.11、12.93±0.92μm-1,S值与比吸收系数之间存在显著的负线性相关关系,而与a(25)/a(365)值则存在显著的正线性关系.比吸收系数越大,a(250)/a(365)值和S值就越小,对应的CDOM分子量就越大,腐质酸的比例就越高.
关键词:  有色可溶性有机物(CDOM)  荧光  溶解性有机碳(DOC)  指数函数斜率  太湖
DOI:10.18307/2006.0401
分类号:
基金项目:中国科学院知识创新工程项目(KZCX3-SW-334);国家自然科学基金项目(40573062,40501078);联合资助
Spatial distribution and absorption characteristics with relation to fluorescence of chromophoric dissolved organic matter (CDOM) in Meiliang Bay of Lake Taihu
ZHANG Yunlin, QIN Boqiang, YANG Longyuan
Nanjing Institute of Geography Limnology, Chinese Academy of Sciences, Nanjing 210008, P. R. China
Abstract:
Chromophoric dissolved organic matter (CDOM) is the light absorption fraction of dissolved organic carbon (DOC) that absorbs light in both the ultraviolet and visible ranges. The spatial and temporal distribution of CDOM in aquatic ecosystems can have important effects on ecosystem productivity, negatively impacting primary productivity due to CDOM absorbs light at both ultraviolet and visible wavelengths while positively impacting secondary productivity by fueling of microbial respiration by photo-degraded CDOM. In water color remote sensing, overlaps of pigment absorption spectra with CDOM absorption at blue wavelength generally complicate the use of chlorophyll a retrieval algorithms that are based on remotely sensed ocean color and lead to overestimated chlorophyll a concentration. In addition, high concentrations of CDOM can also act as a photoprotectant against UV damage for aquatic organisms. However, the protection against UV radiation provided by dissolved humic material for aquatic biota may be diminished if photodegradation of CDOM by UV radiation and acidification increase the UV transparency in lakes. CDOM absorption measurements and their relationship with DOC, and fluorescence are presented in Meiliang Bay of Lake Taihu based on a field investigation and lab analysis to show the spatial distribution of CDOM. Absorption spectral of CDOM was measured from 240 to 800 nm. Concentrations of DOC ranged from 10.48 to 19.72 mg/L with an average of 13.20 ±2.78 mg/L. CDOM absorption coefficients at 280 nm and 355 nm were in the range 18. 73-31. 91 m-1 ( average 23.19±4.36mm-1) and 4. 63-7. 14 mm-1 (average 5. 76±0. 90 mm-1),respectively. The values of the DOC-specific absorption coefficient at 355 nm ranged from 0. 34 to 0. 57 L/( mg · m). Fluorescence emission at 450 nm, excited at 355 nm, had a mean value of 1. 69 ±0. 77 nmm-1. A significant lake zone difference is found in DOC concentration, CDOM absorption coefficient and fluorescence. This regional distribution pattern was in agreement with the location of sources of yellow substance : highest concentrations close to river mouth under the influence of river inflow, lower values in outlet of Meiliang bay. CDOM fluorescence and absorption coefficient were significantly and positively correlated. The results show a good correlation between CDOM absorption and DOC coefficients during 280-500 nm short wavelength intervals. The coefficient of variation between CDOM absorption and DOC concentration decreased with the increase of wavelength from 280 to 500 nm. The linear regression equations between fluorescence, DOC concentration and absorption coefficients at 355 nm are: Fn ( 355 ) = 0.692( ±0. 135)a(355)-2.291 (±0.786),a(355) =0.233(±0.061)DOC +2.690(±0.816),respectively. The exponential slope coefficient ranged from 11.0 to 14.9 um-1 with a mean value 13. 86 ± 0. 91um-1, 15. 8-20. 7 um-1 with a mean value 18. 54 ± 1. 11 um-1 and 9.9-13. 9 um-1 with a mean value 12. 93 ± 0. 92um-1 over the 280-500 nm, 280-360 nm and 360-440 nm intervals. A significant negative linear correlation was found between spectral slope coefficient and DOC specific absorption coefficient, but a significant positive linear correlation for spectral slope coefficient and the ratio of a( 250)/a( 365 ). Larger specific absorption coefficient corresponds to smaller a (250)/a (365) and spectral slope coefficient, which shows higher ratio humic in CDOM.
Key words:  Chromophoric dissolved organic matter (CDOM)  fluorescence  dissolved organic carbon (DOC)  spectral slope coefficient  Lake Taihu
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