海南八门湾红树林保护区海水富营养化评价及其主成分分析

Eutrophication assessment and principal component analysis of bamen mangrove natural reserve of Hainan

2019年丰水季和平水季,采集八门湾红树林保护区及其邻近水域(八门湾海域)海水,测定水温、盐度、pH、溶解氧、活性磷酸盐(DIP)、亚硝酸盐-氮(NO_(2)-N)、硝酸盐-氮(NO_(3)-N)、氨-氮(NH_(4)-N)、化学需氧量(COD_(Mn))、叶绿素α(Chl-α)及悬浮物等11项指标,利用主成分分析法、营养状态质量指数、富营养化指数研究该海域的水质状况,并分析影响该海域水质的主要影响因子。结果表明:八门湾海域丰水季和平水季海水水质都处于劣四类海水水质,DIP为主要超标因子,丰水季62.5%站位和平水季87.5%站位的DIP为劣四类海水水质。相关分析表明,影响该海域水质的主要影响因子为水温、盐度、COD_(Mn)、NH_(4)-N、DIP、pH、NO_(2)-N、NO_(3)-N、Chl-α。应用主成分分析将11项水质指标提取3个主成分,共解释了81.34%的方差。主成分综合得分分析表明,平水季水质状况优于丰水季,平水季污染较轻,丰水季水质污染严重。富营养化指数评价结果表明,八门湾海域丰水季和平水季均处于严重富营养化状态,其中丰水季以氮限制潜在性富营养为主,平水季以氮中等限制潜在性富营养为主。营养状态质量指数评价,八门湾海域丰水季和平水季营养水平总体上都是属于富营养水平,站位达到100%,该海域水质受到污染。空间上总体呈现出从湾内至口门外海域浓度逐渐变小趋势。文昌河和文教河径流输送污染物是主要污染源,应加强外源污染物输入控制及八门湾海域的水环境保护,从而改善其水质状况。

In wet season and normal season of 2019,the seawater of the Bamen Mangrove Natural Reserve and its adjacent waters(the Bamen Lagoon area)were collected and 11 environmental variables including temperature,salinity,pH,dissolved oxygen,active phosphate(DIP),nitrite-nitrogen(NO_(2)-N),nitrate-nitrogen(NO_(3)-N),ammonia-nitrogen(NH_(4)-N),chemical oxygen demand(COD_(Mn)),chlorophyll-α(Chl-α)and suspended solids were measured.The water quality of Bamen Lagoon area was studied and the main driving factors affecting its water quality were analyzed by principal component analysis(PCA),nutrient quality index(NQI)and eutrophication index.The results showed that the seawater quality of the Bamen Lagoon in wet season and normal season of 2019 were exceeded the fourth grade Seawater Quality Standard of China.High concentrations of DIP occurred mainly factor,with which 62.5% station in wet season and 87.5%station in normal season were exceeded the fourth grade.PCA demonstrated that temperature,salinity,COD_(Mn),NH_(4)-N,DIP,pH,NO_(2)-N,NO_(3)-N,Chl-α were the dominating factors influencing the seawater quality.Three principal components were extracted from 11 seawater quality variables by PCA,which explained 81.34% of the total variance.The PCA analysis indicated that the water quality in normal season was better than that in wet season and the water pollution in wet season was serious than that in normal season.According to the evaluation of eutrophication index,the Bamen Lagoon area was in serious eutrophication in wet season and normal season,in which the potential eutrophication with nitrogen limited was dominated in wet season,and the potential eutrophication with medium nitrogen limited in normal season.According to the assessment of nutritional quality index,the nutritional level of the Bamen Lagoon in wet season and normal season was generally eutrophic with 100% station,and the water quality was polluted.On the whole,the concentration of pollution was more serious in Bamen Lagoon than the entrance of South China Sea.The runoff of the Wenchang River and the Wenjiao River was the main pollution sources.The water environment protection of the Bamen Lagoon should be strengthened to improve its water quality and control of exogenous pollutants input.