湖泊沉积物溶解性有机氮组分特征及其与水体营养水平的关系

Compositional Characteristics of Sediment Dissolved Organic Nitrogen in Typical Lakes and Its Relationship on Water Trophic Status

通过紫外-可见光吸收光谱,三维荧光光谱和气相色谱质谱联用(GC-MS)方法,比较研究了不同湖区与不同营养水平五个典型湖泊(洱海、滇池、鄱阳湖、武汉东湖、太湖)沉积物DON组分特征及其与水体营养水平间关系。结果表明:1与东部平原湖区相比,云贵高原湖泊沉积物DON结构较为稳定,生物可利用率较低;2同属云贵高原湖区,污染较严重的滇池,其沉积物DON来源和结构组分较复杂,生物可利用率较高;而污染程度相对较轻的洱海,其沉积物DON来源较简单,结构组分稳定性相对较高,有利于维持较好的水质;3东部平原湖区中,太湖和武汉东湖营养水平接近,其沉积物DON结构组分相近且相对复杂,但芳香度较低,芳香环取代基较少,对营养盐的固持能力较弱,对水污染的贡献较大,而鄱阳湖,其沉积物DON结构组分相对简单,但对营养盐的固持能力较强,对维持良好水质起积极作用;4P_((Ⅲ+Ⅴ,n))/P_((Ⅰ+Ⅱ,n))指数(类腐殖质与类蛋白质含量的比值)依次为滇池(33.14)>洱海(21.49)>太湖(15.65)>东湖(8.49)>鄱阳湖(5.21),E_4/E_6指数(465与665nm处的吸光度比值)依次为滇池(27.00)>东湖(6.65)>鄱阳湖(5.47)>太湖(3.50)>洱海(2.31),即P_((Ⅲ+Ⅴ,n))/P_((Ⅰ+Ⅱ,n))与E_4/E_6指数对不同营养水平湖泊的区分度较好,此外,两种指数与沉积物中多种氮具有较好的相关性,两者可在一定程度上指示湖泊营养水平。

UV-Vis absorbance,fluorescence,and Gas Chromatography Mass Spectrometry（GC-MS）were applied to the comparative study on sediment dissolved organic nitrogen（DON）in five typical lakes（Erhai lake,Dianchilake,Poyang lake,Wuhan Dong lake,and Taihu lake）in different lake regions with different nutrition status,revealing the relationship between structural and compositional characteristics of sediment DON and trophic level of lakes.The obtained results showed that：1Structure of lake sediment DON in Yungui Plateau region is more stable,compared with those in Eastern Plain region,indicating its lower bioavailability.2In Yungui Plateau region,the source and compositional characteristics of sediment DON weremore complex in Dianchi lake（a seriously polluted lake）,and its sediment DON bioavailabilitywas relatively higher.While,with respect to the less polluted Erhai lake,the source of sediment DON is more simple with a higher stability in DON structure and composition,which is beneficial for maintaining its good water quality.3In Eastern Plain region,nutrition status of Taihu lake was similer to Donghu lake.The structure and composition of sediment DON was complex.But the lower aromaticityand fewer Aromatic ring substituents abundance made their relatively weak nutrient retention ability,posing risk to water quality.With regard to Poyang Lake,the structure and composition of sediment DON was relatively simple,but nutrient retention ability was relatively strong,which played a positive role in maintaining good water quality.4P（Ⅲ＋Ⅴ,n）/P（Ⅰ＋Ⅱ,n）values（the content ratio of humic-like substanceto protein-like substances）were in sequence of Dianchi Lake（33.14）〉Erhai Lake（21.49）〉Taihu Lake（9.06）〉Donghu Lake（7.04）〉Poyang Lake（4.83）,while E_4/E_6values（the ratio of UV-Vis absorbance at 465 and 665nm）were in sequence of Dianchi Lake（27.00）〉Donghu Lake（6.65）〉Poyang Lake（5.47）〉Taihu（3.50）〉Erhai Lake（2.31）.In addition,P_（（Ⅲ＋Ⅴ,n））/P_（（Ⅰ＋Ⅱ,n））and E_4/E_6 valueswere positively correlated with thecontents of the different nitrogen（N）forms in the sediments.The above information suggested that P_（（Ⅲ＋Ⅴ,n））/P_（（Ⅰ＋Ⅱ,n））and E_4/E_6 values exhibited good discrimination degree among different trophic status lakes,and they were considered to indirectly indicate the nutrition levels of lakes to a certain extent.