Alomary Ahmed A, Belhadj Soraya
Department of Chemistry, Yarmouk University, Irbid, Jordan.
Environ Monit Assess. 2007 Dec;135(1-3):265-80. doi: 10.1007/s10661-007-9648-8. Epub 2007 Mar 7.
Surface sediment samples (n = 18) were collected from the Algerian Mediterranean coasts and analyzed for seven metals using inductively coupled plasma-optical emission spectrometry in order to asses the distribution and bioavailability of metals and to study the anthropogenic factors affecting their concentrations. Sediment samples were size-fractionated into three sizes: 1,080-500 (coarse), 500-250 (medium), and <250 mm (fine). Bulk sediments were subjected to both sequential extraction and total digestion to evaluate the reliability of the sequential extraction procedure (SEP), while the fractions have been only sequentially extracted for metals speciation. The metals were sequentially extracted into five phases namely exchangeable (P1), carbonates (P2), Fe-Mn oxides (P3), organic (P4) and residual (P5). Metal recoveries in sequential extractions were +/-20% of the independently measured total metal concentrations; the high recovery rates indicate the good reliability of the SEP used in this study. Correlation coefficients indicated that the grain size has an effect on the distribution of metals in the investigated samples. The order of metal levels in the fractions was medium > fine > coarse for all the metals. The average total extractable metal concentrations for Cd, Cr, Cu, Fe, Ni, Pb, and Zn were 1.1, 8.8, 4.7, 1,291.3, 13.9, 5.7 and 20.4 mug/g, respectively. The northeastern shelf had the lowest metal levels while the highest were in northwestern part mainly due to the significant tourism activities in the northwestern part. Comparison of our results to Earth's crust values and to previous studies points out that our samples were relatively unpolluted with respect to the heavy metals investigated; most of the metals are not from anthropogenic sources. Enrichment factors as the criteria for examining the impact of the anthropogenic sources of heavy metals were calculated, and it was observed that the investigated samples were not contaminated with Cr, Cu, and Fe, moderately contaminated with Ni, Pb, and Cd, and contaminated with Cd in some sites. The P5 phase had the highest percents of Cr, Cu, Fe, Ni, and Zn. Cadmium and lead were predominant in the P4 phase, while Cu, Fe and Zn were distributed in the order P5 > P3 > P4 > P2 > P1. The following order of bioavailability was found with the heavy metals Pb > Cr > Cd > Ni > Zn > Cu > Fe.
从阿尔及利亚地中海沿岸采集了18个表层沉积物样本,采用电感耦合等离子体发射光谱法分析了七种金属,以评估金属的分布和生物有效性,并研究影响其浓度的人为因素。沉积物样本按粒径分为三种:1080 - 500微米(粗粒)、500 - 250微米(中粒)和<250微米(细粒)。对整体沉积物进行了连续提取和全量消解,以评估连续提取程序(SEP)的可靠性,而各粒级仅进行了连续提取以分析金属形态。金属被依次提取到五个相,即可交换相(P1)、碳酸盐相(P2)、铁锰氧化物相(P3)、有机相(P4)和残留相(P5)。连续提取中的金属回收率为独立测量的总金属浓度的±20%;高回收率表明本研究中使用的SEP具有良好的可靠性。相关系数表明,粒径对所研究样本中金属的分布有影响。所有金属在各粒级中的含量顺序均为中粒>细粒>粗粒。镉、铬、铜、铁、镍、铅和锌的平均总可提取金属浓度分别为1.1、8.8、4.7、1291.3、13.9、5.7和20.4微克/克。东北大陆架的金属含量最低,而最高的在西北部,主要是由于西北部有大量的旅游活动。将我们的结果与地壳值和先前的研究进行比较指出,就所研究的重金属而言,我们的样本相对未受污染;大多数金属并非来自人为源。计算了作为检查重金属人为源影响标准的富集因子,观察到所研究的样本未受铬、铜和铁污染,镍、铅和镉受到中度污染,在某些地点镉受到污染。P5相中铬、铜、铁、镍和锌的百分比最高。镉和铅在P4相中占主导地位,而铜、铁和锌的分布顺序为P5>P3>P4>P2>P1。发现重金属的生物有效性顺序为铅>铬>镉>镍>锌>铜>铁。