Abstract

Results of metal(loid)s pollution history, their enrichment and contamination factors in sediments of Wami River Estuary, Tanzania are presented. Two sediment cores (WE1 and WE2) were retrieved from the Estuary using hand-driven PVC coring tubes. Levels of metal(loid)s in sediment samples were determined using EDXRF spectrometer coupled with X-lab Pro^TM software. Metal(loid)s enrichment factors (EF) were determined using metal(loid)s baseline values established during this study. Contamination factors were determined by dividing measured metal(lod)s concentrations in the samples by their respective baseline concentrations. Sediment physical chemical parameters were determined in order to establish their relationship with metal(loid)s concentrations. Sediment chronologies were established using the Constant Initial Concentration (CIC) lead-210 sediment-dating model in order to convert sediment depth profile into timescales. The lowest concentrations of As in sediments was measured in sediments deposited during 1960s, followed by increase reaching the highest concentrations in sediments deposited between ca. 2015 and 2017. Lowest and highest concentrations of Cd were measured in 1960’s and ca. 2000, respectively. Cu and Zn had their maximum concentrations in ca. 1971 and their significant positive correlation (r = 0.94, p = 0.01) suggest common origin of these metals. Average metals enrichment factors in the core were established and are in the order As = Cd = Cu = Pb = Zn = 0.1. This EF value suggests that all metals in sediments of Wami originate from natural sources (EF < 1). Metal(loid)s contamination factors (CF) were low to moderate for As, Cu and Zn; moderate for Pb; and low to considerable for Cd. CIC model revealed that the sediment at the bottom of cores WE1 and WE2 date back about 33 and 55 years, respectively. Sediments of Wami Estuary is characterized by mixing as evidenced in the established chronologies. Therefore, reported radiometric dates should be considered as a preliminary chronological estimate and further research is needed focused on terrestrial records of anthropogenic activities.

摘要

介绍了坦桑尼亚瓦米河口沉积物中金属（类）的污染历史及其富集和污染因素的结果。使用手动 PVC 取芯管从河口取回了两个沉积物芯（WE1 和 WE2）。使用结合 X-lab Pro ^{TM的 EDXRF 光谱仪测定沉积物样品中金属（类固醇）的含量}软件。使用本研究期间建立的金属（类固醇）基线值确定金属（类固醇）富集因子（EF）。通过将样品中测量的金属（lod）浓度除以它们各自的基线浓度来确定污染因子。确定了沉积物的物理化学参数，以确定它们与金属（类）浓度的关系。沉积物年表是使用恒定初始浓度 (CIC) 铅 210 沉积物年代测定模型建立的，以便将沉积物深度剖面转换为时间尺度。沉积物中 As 的最低浓度是在 1960 年代沉积的沉积物中测得的，随后增加到 ca 之间沉积的沉积物中的最高浓度。2015 年和 2017 年。Cd 的最低和最高浓度是在 1960 年代和 ca 时测量的。2000，分别。Cu 和 Zn 的最大浓度在 ca。1971 年及其显着正相关（r = 0.94，p  = 0.01) 表明这些金属的共同来源。建立了岩心中的平均金属富集因子，顺序为 As = Cd = Cu = Pb = Zn = 0.1。该 EF 值表明 Wami 沉积物中的所有金属都来自自然资源（EF < 1）。As、Cu 和 Zn 的金属（类）污染因子（CF）为低到中等；中等铅含量；并且 Cd 含量低到可观。CIC 模型显示，WE1 和 WE2 岩心底部的沉积物分别可追溯到 33 年和 55 年前。瓦米河口沉积物的特点是混合，这在既定的年代学中得到了证明。因此，报告的辐射日期应被视为初步的时间估计，需要进一步研究，重点是人类活动的陆地记录。