南沙群岛海域沉积物环境与间隙水中的铁锰

IRON AND MANGANESE IN INTERSTITIAL WATERS AND SEDIMENT ENVIRONMENTS OF NANSHA ISLANDS,SOUTH CHINA SEA

研究了南沙群岛海域泻湖及礁外沉积物间隙水中的Ｆｅ￣（２＋）、Ｍｎ￣（２＋）、浓度及其比值、沉积物海水界面扩散通量、沉积物类型及其氧化还原环境。结果表明，间隙水中的Ｆｅ２＋、Ｍｎ￣（２＋）浓度泻湖高于礁外，Ｆｅ￣（２＋）（礁）／Ｆｅ￣（２＋）（泻）浓度比为０．２８，Ｍｎ￣（２＋）（礁）／Ｍｎ￣（２＋）（泻）浓度比为０．６６，Ｍｎ￣（２＋）／Ｆｅ￣（２＋）比值泻湖内为１．４７，礁外为３．５２．Ｆｅ￣（２＋）、Ｍｎ￣（２＋）均是从沉积物向上覆海上扩散，Ｍｎ２＋／Ｆｅ￣（２＋）扩散量的比值泻湖为１．３８，礁外为３．８４．Ｆｅ￣（２＋）、Ｍｎ￣（２＋）浓度及其扩散特征的不同是由其氧化还原速率、扩散速度控制体系及其氧化还原环境共同作用的结果。南沙群岛海域泻湖沉积物的还原性比礁外沉积物强。

The paper lays emphasis on Fe2+, Mn2+, Mn/Fe and their outer-reef/lagoon ratios in interstitial waters, diffuse fluxes across sediment-seawater interface, sediment types and redox environment in the lagoons and in the outer of reefs in the Nansha Islands, South China Sea.The main results are as follows: Fe2+ and Mn2+ concentrations are higher in lagoon interstitial waters than in the outer of reef and Mn2+ higher than Fe2+. The average ratio outer-reef/lagoon of Fe2+ in interstitial waters is 0. 28 and the ratio of Mn2+ is 0. 66. The ratios of Mn/Fe is 1. 47 in lagoon and 3. 52 in outer of reef of sediment interstitial waters. The diffusion directions of Fe2+, Mn2+ are from sediment to overlying seawater. The Mn/Fe ratios of diffusion fluxes are 1. 38 in lagoon and 3. 84 in outer of reef. The characteristics of Fe2+, Mn2+ in sediment interstitial waters are controlled by their redox rates, diffusion speeds, controlling systems and redox environment. The lagoon sedimnt composition is silty sand and the lagoon envrionment is reductive. The outer-reef sediment is mainly silty mud and has weak reductive feature. The inconsistent result obtained from Fe2+ , Mn2+ concnetrations, Mn/Fe ratios and their outer-reef/lagoon ratios, diffusion fluxes across sediment-seawater interface and their Mn/Fe ratio and sediment redox degree (ROD) is the sediment reductive characteristics is stronger in lagoon than outer-reef.