This study aims to assess seasonal and spatial variations, contamination status, ecological risks, and metal sources (Ni, Pb, Cr, Cu, Mn, and Zn) in human-afforested mangrove sediments in a deltaic region. Five sampling locations were sampled during dry and wet seasons. Heavy metal concentrations followed the order: Mn > Zn > Ni > Cr > Cu > Pb. Metal loads, except Cu and Pb, were higher during the dry season, aligning with national and international recommendations. Sediment quality guidelines, contamination factor, geoaccumulation index, enrichment factors, and pollution load index indicated uncontaminated sediment in both seasons. Potential ecological risk assessment showed low risk conditions in all sites. However, modified hazard quotient indicated moderate pollution risk from all metals except Pb. Analysis suggests anthropogenic sources, particularly evident near shipbreaking yards in Sitakunda. While initially uncontaminated, ongoing metal influx poses a potential risk to mangrove ecosystems.

中文翻译：

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世界最大三角洲红树林沉积物中的重金属：分布图、污染状况、风险评估和来源追踪

本研究旨在评估三角洲地区人工造林红树林沉积物中的季节和空间变化、污染状况、生态风险和金属来源（镍、铅、铬、铜、锰和锌）。在旱季和雨季对五个采样点进行了采样。重金属浓度顺序为：Mn>Zn>Ni>Cr>Cu>Pb。除铜和铅外，金属含量在旱季较高，符合国家和国际建议。沉积物质量准则、污染因子、地累积指数、富集因子和污染负荷指数表明两个季节的沉积物均未受污染。潜在生态风险评估显示所有地点的风险状况均较低。然而，修改后的危险商数表明除铅以外的所有金属均具有中等污染风险。分析表明人为来源，尤其是在西塔昆达拆船场附近。虽然最初未受污染，但持续的金属流入对红树林生态系统构成了潜在风险。