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Assessing environmental change through chemical-sediment chronologies from inland lakes

机译：通过内陆湖泊的化学沉积年代学评估环境变化

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This paper examines the hypothesis that the spatial pattern of metal accumulation rates in inland lake sediments provides insight into the causes of the historical and continued loadings of contaminants to the environment. To address this, copper and lead accumulation rates in the Great Lakes' watershed were studied. A multi-element approach was used, in which many non-toxic chemicals were measured along with the toxic chemicals of interest, rather than a target-specific approach. The multi-element approach also allowed for assessing the environmental state of the lake with respect to its surrounding watershed. Sediment cores were collected from the deepest portion of five Michigan inland lakes, sectioned, metals extracted by nitric acid, microwave digestion and leachates analysed for 26 metals using an inductively coupled, plasma, mass spectrometer with hexapole technology. Sedimentation rates, ages and focusing factors were calculated via ~(210)Pb. Dasymetric mapping was used to estimate population distributions in lake watersheds. Watershed area was estimated from digital elevation data using Arc/INFO (ESRI, Redlands, California). The data show that as loadings from dominant (regional) sources decrease (e.g. atmospheric deposition in the case of lead), new patterns provide insight into causes for continued contaminant loadings (e.g. population density). The data also show the universal response of the watersheds to the onset of the anthropogenic loadings of lead but not that of copper. Individual watersheds had different onset times for anthropogenic copper loadings. Recent lead loadings to the environment can be related to population density, and those of copper reflect, in part, a spatial pattern that is similar to the regional pattern for lead during the mid-1970s. As this pattern for lead could be related to a regional gradient of lead concentrations in atmospheric deposition, the same relation cannot be made for copper. The cause for this spatial pattern for copper is not clear.
机译：本文研究了以下假设：内陆湖泊沉积物中金属积累速率的空间格局可以洞悉污染物向环境的历史和持续负荷的原因。为了解决这个问题，研究了五大湖流域的铜和铅积累速率。使用了一种多元素方法，其中测量了许多无毒化学品以及感兴趣的有毒化学品，而不是针对特定目标的方法。多元方法还可以评估湖泊周围流域的环境状况。从密歇根州内陆五个湖泊的最深处收集沉积物芯，将其切成薄片，然后使用六极杆技术通过电感耦合等离子体质谱仪对硝酸，微波消解和渗滤液中的26种金属进行分析。通过〜（210）Pb计算沉积率，年龄和聚焦因子。幅测图用于估计湖泊流域的人口分布。使用Arc / INFO（ESRI，加利福尼亚州雷德兰兹），根据数字高程数据估算了流域面积。数据表明，随着来自主要（区域）源的负荷减少（例如，铅的情况下为大气沉积），新的模式提供了深入了解污染物持续负荷的原因（例如人口密度）的信息。数据还显示了流域对铅的人为负荷的开始的普遍反应，但对铜的人为的负荷没有反应。各个流域的人为铜负荷量出现时间不同。最近对环境的铅负荷可能与人口密度有关，而铜的铅负荷在某种程度上反映了与1970年代中期铅的区域格局相似的空间格局。由于这种铅的模式可能与大气沉积中铅浓度的区域梯度有关，因此对于铜无法建立相同的关系。铜的这种空间图案的原因尚不清楚。

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