沿海盐沼是沉积环境,可以积累人类活动引入环境的污染物。由于金属的寿命和毒性,它们是沿海环境中值得关注的污染物。我们评估了从缅因州到乔治亚州的美国东海岸9个盐沼地点的金属浓度和积累速率。在有氧/厌氧和淡水/盐水条件下,在富含有机物和矿物质为主的盐沼土壤中进行金属迁移率测定后,我们专注于铬的轮廓,镍,铜,锌,镉,铅,和铀在九种沼泽土壤中的两个岩心中,这些岩心以前使用铅210放射性同位素技术进行了测定。我们研究了土地覆盖和土地覆盖的空间分布,沼泽垂直吸积,和其他流域特征与金属浓度和金属的深度/时间积分积累相关。我们发现站点之间的金属浓度和/或库存存在统计学上的显着差异,金属的积累与流域发达的土地覆盖和潮汐沼泽的垂直积累速率呈正相关。铬的积累,镉,和铅与发达的土地覆盖显著相关,而铬的积累,镍,铜,锌,和铅与决定景观沉积物输送的因素相关(例如,河流悬浮沉积物,流域土壤可蚀性,和农业用地向海岸倾斜)并测量湿地吸积率。自1925年以来,我们观察到美国东海岸的许多金属浓度下降,表明污染缓解策略已经成功地减少了金属污染并将其运送到沿海地区。然而,近几十年来,盐沼垂直吸积率的增加在很大程度上抵消了金属浓度的降低,导致沿海盐沼土壤中金属的积累速率没有变化,或者,在某些情况下,随着时间的推移而增加。
Coastal salt marshes are depositional environments that can accumulate pollutants introduced to the environment from human activities. Metals are a contaminant of concern in coastal environments due to their longevity and toxicity. We assessed metal concentrations and accumulation rates in nine salt marsh sites along the U.S. East Coast from Maine to Georgia. Following a metal mobility assay in organic-rich and mineral dominated salt marsh soils under aerobic/anaerobic and freshwater/saltwater conditions, we focused on profiles of chromium, nickel, copper, zinc, cadmium, lead, and uranium in two soil cores from each of the nine marshes that had previously been dated using lead-210 radioisotope techniques. We examined how land cover and the spatial distribution of land cover, marsh vertical accretion, and other watershed characteristics correlated with metal concentrations and depth/time-integrated accumulation of metals. We found statistically significant differences in metal concentrations and/or inventories between sites, with accumulation of metals positively correlated with both developed land cover in the watershed and rates of vertical accretion in the tidal marsh. The accumulation of chromium, cadmium, and lead were significantly correlated with developed land cover while the accumulation of chromium, nickel, copper, zinc, and lead were correlated with factors that determine sediment delivery from the landscape (e.g., riverine suspended sediment, soil erodibility in the watershed, and agricultural land cover skewed towards the coast) and measured wetland accretion rates. We observed declines in the concentration of many metals since 1925 at sites along the U.S. East Coast, indicating pollution mitigation strategies have succeeded in reducing metal pollution and delivery to the coastal zone. However, increasing rates of salt marsh vertical accretion over recent decades largely offset reductions in metal concentrations, resulting in rates of metal accumulation in coastal salt marsh soils that have not changed or, in some instances, increased over time.