Institute of Wetland Research, Chinese Academy of Forestry, Beijing, China.
Beijing Key Laboratory of Wetland Services and Restoration, Beijing, China.
PLoS One. 2021 Jan 22;16(1):e0245438. doi: 10.1371/journal.pone.0245438. eCollection 2021.
Bamen Bay is located at the intersection of the Wenjiao River and Wenchang River in Hainan Province (China), where mangroves have been facing a threat of water quality deterioration. Therefore, it is imperative to study the characteristics of the surface water quality on a watershed scale. Water samples were collected three times from 36 monitoring sites from 2015 to 2016. It was found that nitrate was the main inorganic nitrogen form and all the surface water types were alkaline. Meanwhile, aquaculture water had high content of nitrogen, total phosphorus, chlorophyll a (Chl.a), total organic carbon (TOC), and chemical oxygen demand (COD). Significant spatial and temporal variations were found for most parameters. However, stable isotopes of δD and δ18O indicated that river water mainly originated from atmospheric precipitation and experienced strong evaporation. The water chemistry and isotopes of the Bamen Bay, mangroves, and aquaculture water were initially affected by the mixing of fresh water and seawater, followed by evaporation. The river and reservoir water chemistry were mainly controlled by water-rock interactions and cation exchange as deduced from the ionic relationships and Gibbs plots. These interactions involved the dissolution of calcite-, bicarbonate-, carbonate-, and calcium-containing minerals. Oxidized environments (river, reservoir, and Bamen Bay) were conducive for nitrification, while anaerobic conditions (mangrove and aquaculture water) were beneficial to the reduced nitrogen forms.
八门湾位于中国海南省文教河和文昌河的交汇处，这里的红树林面临着水质恶化的威胁。因此，研究流域尺度上的地表水水质特征势在必行。从 2015 年到 2016 年，在 36 个监测点采集了三次水样。结果表明，硝酸盐是主要的无机氮形式，所有地表水类型均呈碱性。同时，养殖水含有高浓度的氮、总磷、叶绿素 a（Chl.a）、总有机碳（TOC）和化学需氧量（COD）。大多数参数都存在明显的时空变化。然而，δD 和 δ18O 的稳定同位素表明，河水主要来源于大气降水，并经历了强烈的蒸发。八门湾、红树林和养殖水的水化学和同位素最初受到淡水和海水混合的影响，随后是蒸发。河流水和水库水化学主要受水岩相互作用和阳离子交换控制，这可以从离子关系和 Gibbs 图推断得出。这些相互作用涉及到方解石、碳酸氢盐、碳酸盐和含钙矿物的溶解。氧化环境（河流、水库和八门湾）有利于硝化作用，而厌氧条件（红树林和养殖水）有利于还原态氮的形成。
