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洱海水华高风险期水体氮磷变化及指示意义
肖梦琦1, 倪兆奎2, 赵海超3,3, 王圣瑞1,2,4
1.南昌大学资源环境与化工学院;2.北京师范大学水科学研究院;3.河北北方学院农林科技学院;4.云南省高原湖泊流域污染过程与管理重点实验室
摘要:
为揭示水华高风险期水体氮磷变化对洱海的指示意义,研究了洱海2009年、2013年和2018年9月上覆水氮磷组成和结构变化及影响因素。结果表明:①ρ(TN)和ρ(TP)均先降后升,由2009年氮磷以DON(0.231 mg/L,占36.90%)和DOP(0.016 mg/L,占42.05%)为主,转变为2018年以NH4+-N(0.197 mg/L,占32.89%)和PP(0.033 mg/L,占70.00%)为主,NH4+-N和溶解性有机氮磷质量浓度变化是引起氮磷变化的主要因子。各形态氮磷质量浓度空间变化差异较大,北部和中部湖区ρ(TN)、ρ(TP)及其增幅均大于南部;ρ(DON)在北部和南部总体呈下降的趋势,中部ρ(DON)先降后升,增幅为3.32%;ρ(DOP)在北部和中部呈递减,南部则先升后降,增加了70.21%;ρ(NH4+-N)在中部和南部湖区显著增加,北部先降后升。②上覆水氮磷质量浓度及形态时空变化受外源负荷、内源释放和藻类生长共同影响,其中入湖河流是影响氮磷质量浓度变化的主因,且农村生活污染和农田面源污染影响也较大;有机氮磷变化主要受外源输入和湖泊微生物代谢影响,而ρ(NH4+-N)变化则主要受沉积物释放和藻类生长影响。③洱海水华高风险期上覆水腐殖化程度明显降低,有机氮磷分子量减小,而活性增加,一定程度上可促进藻类生长。研究显示近10年洱海氮磷质量浓度有增加趋势,有机氮磷质量浓度虽有所下降,但其活性较高,藻类水华风险并未降低,除进一步加强外源负荷控制,关注TN和TP的同时,洱海保护治理还应关注有机氮磷输入及中部和南部湖区沉积物氮磷释放的水质影响。
关键词:  氮磷  形态组成  上覆水  水华高风险期  指示意义
DOI:
分类号:
基金项目:国家自然科学基金云南联合基金(No. U1902207);国家万人计划项目(No.312232102),
Characteristics and Significance of Nitrogen and Phosphorus Variation at the High Risk Period of Algal Bloom in Lake Erhai
Ni Zhaokui,Zhao Haichao,et al
Abstract:
In order to reveal the significance of the changes of nitrogen (N) and phosphorus (P), and the changes of N, P forms and the structure of dissolved organic N (DON) and P (DOP) in Erhai Lake during the high algal bloom risk period September of 2009, 2013 and 2018 were studied. The results showed that ① DON and DOP were the dominant nutrients forms in 2009, with average concentration of 0.231 mg/L (accounting for 36.90% of the TN) and 0.016 mg/L (42.05%), respectively. Thereafter, NH4+-N and particulate phosphorus (PP) became to the dominant nutrient forms, with average concentrations of 0.197 mg/L (32.89%) and 0.033 mg/L (70%) in 2018, respectively. The main factors that cause the change of N were related to NH4+-N and DON, while TP was closely associated with DOP. In addition, the spatial change of N and P forms showed great variability, and ρ(TN) and ρ(TP) in the northern and central areas were higher than those in the south areas. DON showed decrease trend in the northern and southern areas, while decreased at first and then increased in middle area. DOP decreased in the north and middle areas while increased firstly and then decreased in the south areas. NH4+-N in the central and southern areas increased significantly. ② The changes of N and P concentration and forms in the overlying water were affected by external load, sediment release and algal growth, among which the rivers entering the lake were the main factors that affect the changes of N and P concentration, and the rural living pollution and non-point source pollution of farmland were also greatly affected. The variations of DON and DOP were mainly affected by exogenous load and microbial activities, while NH4+-N was mainly affected by sediment release and algae growth. ③ The humification degree of the overlying water decreased obviously, the molecular weight of organic N and P decreased, and the activity increased, which promoted the growth of algae to a certain extent during the high risk period of Erhai water bloom. Therefore, the mass concentration of N and P in Erhai Lake has increased in recent 10 years. Although the mass concentration of organic N and P has decreased, its activity was relatively high, and the risk of algal bloom has not decreased. In addition to further strengthening the control of external load, while the protection and treatment of Erhai Lake should also pay more attention to the impact of organic N and P input and the release of N and P from the sediments in the central and southern lakes on the water quality.
Key words:  nitrogen and phosphorus variation  forms  overlying water  high risk period of algal bloom  significance