Mangrove ecosystems are essential to society, providing ecological and economic services, and play a crucial role in the geochemical land-ocean interface as a sink for potentially toxic metals. This study assessed metals (Al, Ba, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Sr and Zn) and arsenic in sediments from three mangrove zones (Tidal Flat, Rhizophora mangle L. and Avicennia schaueriana Stapf & Leechman ex Moldenke forests) during two seasons: spring of 2015 and autumn of 2016, with the latter being a severe drought year. Overall results suggest that Fe/Mn oxyhydroxides and clay minerals control the distribution of metal and arsenic in the Tidal Flat zone. In the mangrove forest however, sulfur and organic matter dominate complexation, with Fe mainly present as insoluble sulfide, and As, Cd, Cu and Zn as metal sulfides or organometallic complexes. In the autumn of 2016, all elements except Cd and Pb had lower concentrations compared to the spring of 2015. Cd and Pb were probably transferred from sources other than mangrove sediments, due to increased saline water intrusion, a consequence of reduced riverine flow, and precipitated in the Rhizophora mangle and Avicennia schaueriana mangrove forests. This increase of Cd and Pb in the mangrove forest suggests potential storage of metal contaminants in the organic rich areas, a change in availability and potential toxicity to fauna and flora and a need for regulatory responses to sediment quality. These results indicate a change in sediment metal contaminant dynamics with the increasing occurrence of extreme weather events – an increased risk to the ecosystem.

红树林生态系统对社会至关重要，可提供生态和经济服务，并在地球化学陆地-海洋界面作为潜在有毒金属的汇聚区中发挥关键作用。本研究评估金属（铝，钡，镉，铬，铜，铁，锰，镍，铅，Sr和Zn）的和砷的沉积物从三个红树区域（滩涂，红海碾压大号。和白骨schaueriana麻黄＆Leechman离摩尔登克森林）在两个季节：2015年春季和2016年秋季，后者是严重干旱的一年。总体结果表明，Fe / Mn羟基氧化物和粘土矿物控制着潮滩带中金属和砷的分布。然而，在红树林中，硫和有机物占主导地位，络合物主要以铁为不溶性硫化物，而砷，镉，铜和锌以金属硫化物或有机金属络合物形式存在。2016年秋季，与2015年春季相比，除Cd和Pb以外的所有元素的浓度均较低。由于咸水入侵增加，河水流量减少以及在根瘤菌和Avicennia schaueriana中沉淀红树林。红树林中Cd和Pb的增加表明，有机污染物丰富的地区可能存在金属污染物的储存，对动植物的可用性和潜在毒性的变化，以及对沉积物质量的监管反应的需求。这些结果表明，随着极端天气事件发生的增加，沉积物金属污染物动力学发生了变化，这增加了对生态系统的风险。