Caetano Miguel, Fonseca Nuno, Cesário Carlos Vale Rute
National Institute for Agronomy and Fisheries Research -- IPIMAR, Av. Brasília 1449-006, Lisbon, Portugal.
Sci Total Environ. 2007 Jul 15;380(1-3):84-92. doi: 10.1016/j.scitotenv.2006.11.026. Epub 2007 Feb 23.
Total lead and its stable isotopes were analysed in sediment cores, leaves, stem and roots of Sacorconia fruticosa and Spartina maritima sampled from Tagus (contaminated site) and Guadiana (low anthropogenic pressure) salt marshes. Lead concentration in vegetated sediments from the Tagus marsh largely exceeded the levels in non-vegetated sediments. Depth profiles of (206)Pb/(207)Pb and (206)Pb/(208)Pb showed a decrease towards the surface ((206)Pb/(207)Pb=1.160-1.167) as a result of a higher proportion of pollutant Pb components. In contrast, sediments from Guadiana marsh exhibited low Pb concentrations and an uniform isotopic signature ((206)Pb/(207)Pb=1.172+/-0.003) with depth. This suggests a homogeneous mixing of mine-derived particles and pre-industrial sediments with minor inputs of anthropogenic Pb. Lead concentrations in roots of plants from the two marshes were higher than in leaves and stems, indicating limited transfer of Pb to aerial parts. A similar Pb isotopic signature was found in roots and in vegetated sediments, indicating that Pb uptake by plants reflects the input in sediments as determined by a significant anthropogenic contribution of Pb at Tagus and by mineralogical Pb phases at Guadiana. The accumulation in roots from Tagus marsh (max. 2870 microg g(-1) in S. fruticosa and max. 1755 microg g(-1) in S. maritima) clearly points to the dominant role of belowground biomass in the cycling of anthropogenic Pb. The fraction of anthropogenic Pb in belowground biomass was estimated based on the signature of anthropogenic Pb components in sediments ((206)Pb/(207)Pb=1.154). Since no differences exist between Pb signature in roots and upper sediments, the background and anthropogenic levels of Pb in roots were estimated. Interestingly, both background and anthropogenic Pb in roots exhibited a maximum at the same depth, although the proportion of anthropogenic Pb was relatively constant with depth (83+/-4% for S. fruticosa and 74+/-8% for S. maritima).
对从塔霍河（污染场地）和瓜迪亚纳河（人为压力较小）盐沼采集的矮盐角草和滨海 Spartina 的沉积物岩芯、叶片、茎和根中的总铅及其稳定同位素进行了分析。塔霍河盐沼植被覆盖沉积物中的铅浓度大大超过了无植被沉积物中的水平。(206)Pb/(207)Pb 和 (206)Pb/(208)Pb 的深度剖面显示，由于污染物铅成分比例较高，向地表方向降低((206)Pb/(207)Pb = 1.160 - 1.167)。相比之下，瓜迪亚纳河盐沼的沉积物铅浓度较低，且随深度具有均匀的同位素特征((206)Pb/(207)Pb = 1.172 ± 0.003)。这表明矿山来源颗粒与工业化前沉积物均匀混合，且人为铅输入较少。两个盐沼植物根中的铅浓度高于叶片和茎中的铅浓度，表明铅向地上部分的转移有限。在根和植被覆盖的沉积物中发现了相似的铅同位素特征，表明植物对铅的吸收反映了沉积物中的输入情况，在塔霍河是由显著的人为铅贡献决定的，在瓜迪亚纳河则由矿物学铅相决定。塔霍河盐沼根中的积累量（矮盐角草中最高为 2870 μg g(-1)，滨海 Spartina 中最高为 1755 μg g(-1)）清楚地表明地下生物量在人为铅循环中的主导作用。基于沉积物中人为铅成分的特征((206)Pb/(207)Pb = 1.154)估算了地下生物量中人为铅的比例。由于根和上部沉积物中的铅特征没有差异，因此估算了根中铅的背景值和人为水平。有趣的是，根中的背景铅和人为铅在同一深度都出现了最大值，尽管人为铅的比例随深度相对恒定（矮盐角草为 83 ± 4%，滨海 Spartina 为 74 ± 8%）。
