洱海水体溶解氧及其与环境因子的关系

Relationship Between the DO and the Environmental Factors of the Water Body in Lake Erhai

通过分析多年洱海水体中溶解氧、氮、磷和叶绿素浓度,结合沉积物氮、磷形态结果,研究了水体中溶解氧与其氮、磷浓度和叶绿素浓度间的相互关系.结果表明,1992～2009年洱海水体中溶解氧在6.61～7.42 mg.L-1之间变化,多年月均值9月最低为6.42 mg.L-1,总体呈下降趋势.水体溶解氧浓度呈由北向南递减趋势,随水深呈下降趋势,最底层为5.15 mg.L-1.水体中溶解氧浓度与其氮、磷浓度呈负相关,且月份间的相关性大于年度间的相关性.水体溶解氧浓度与沉积物中弱吸附态磷、有机态磷和氨氮的质量分数呈负相关,与铁铝氧化态磷、无机磷和硝态氮的质量分数呈正相关.水体溶解氧浓度与叶绿素浓度呈负相关,表明洱海为好氧湖泊,但已接近厌氧水平.氮磷营养盐含量的增加促进水体含氧量的降低,随着洱海水体溶解氧浓度的降低,也促进了其沉积物中氮磷释放,藻类数量增加和水体富营养化的加剧.

The contents of DO and nitrogen（N）,phosphorus（P）,chlorophyll a in water from Lake Erhai were analyzed by combining the nitrogen and phosphorus forms in sediment.The results indicated that the DO contents of the water from Lake Erhai varied from 6.61 to 7.42 mg/L from 1992 to 2009,which is generally decreased.The minimum mean value was 6.42 mg/L in September.The trend of the DO contents from north to south was decreasing,and also decreased with the increasing of the water depth in Lake Erhai,the DO content was 5.15 mg/L at the water bottom.The relationship between the contents of DO and N,P was negative,and the relativity of different months was greater than that of different years.The relationship between the contents of DO and the contents of labile-P,organic-P,NH4^＋-N in sediment was negative,which was positive with the contents of Fe/Al-P,inorganic P and NO-3-N.The relationship between the contents of DO and chlorophyll a in water was negative,which indicated that Lake Erhai is aerobic,and is approaching anaerobic gradually.With the increasing of released content of N and P,the increasing of alga biomass was accelerated and the worsening of water body eutrophication also can be promoted by the decreased DO content in water from Lake Erhai.