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首页> 外文期刊>Journal of Environmental Radioactivity >Quantifying historical releases and pre-operation levels of metals and radionuclides
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Quantifying historical releases and pre-operation levels of metals and radionuclides

机译：量化历史释放和金属和放射性核素的前操作水平

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摘要

Assessing the recovery of aquatic ecosystems from metal and radionuclide contamination requires knowledge of the concentration of radionuclides and metals before anthropogenic releases. Pre-operational conditions, or baseline, are often unknown for many mining operations initiated decades ago. The objectives of this study were to quantify baseline levels of metals and radionuclides and describe historical releases of an industrialised watershed in Northern Ontario where mining operations were carried out from 1955 to 1996. For this purpose, water and surface sediment samples were collected from this watershed and in an adjacent non-industrialised watershed every 2 km. Using metal and radionuclide concentrations in the non-impacted watershed, we calculated water and sediment baseline concentrations as upper 95th percentile values. Baseline pH, 226Ra and uranium in water of lakes and rivers were similar at pH of 6.8, 10 mBq center dot l- 1, and 2.5 mu g center dot l- 1, respectively. For sediments, baseline lake sediment exhibited concentrations of radionuclides that were higher than river sediments. We calculated baseline concentrations in lake sediment at 2,115 Bq center dot kg- 1 210Pb, 535 Bq center dot kg- 1 210Po, 218 Bq center dot kg- 1 226Ra, 235 Bq center dot kg- 1 228Th, 184 Bq center dot kg- 1 230Th, and 223 Bq center dot kg- 1 232Th. Baseline concentrations of metal levels in lakes were at 98 mg kg- 1 Ni, 119 mg kg- 1 Cu, 2300 mg kg- 1 Zn, 112 mg kg- 1 Pb and 19 mg kg- 1 U. In Lake Huron, we collected two sediment core profiles along with surface sediment to estimate baseline radionuclide activities and metal concentrations and quantify historical releases from the industrialised watershed. The sediment core profiles reflected baseline conditions prior to releases from the uranium mining operation and contamination from its onset in 1955 to its closure in 1996. Concentration of metals in pre-industrial sediment layers were lower than in surface sediment of Lake Huron, suggesting atmospheric depositions. Our study indicates that collecting surface sediment in this non-impacted watershed may yield baseline concentrations for uranium and radionuclides. For metal, collecting surface sediment may yield ambient metal concentrations because of long-range atmospheric transport from remote sources. By comparison, sedimentary profiles can provide baseline concentrations of both metals and radionuclides. In the case of the Serpent River watershed, we report that water quality has recovered downstream of Quirke Lake as of 1993 and that additional sediment cores would better assess sediment recovery.
机译：评估来自金属和放射性核素污染的水生生态系统的回收需要了解人为释放前的放射性核素和金属浓度。在几十年前发起的许多采矿业务中，运营前的条件或基线往往是未知的。本研究的目标是量化金属和放射性核素的基线水平，并描述在安大略省北部工业化流域的历史版本，其中采矿业务从1955年到1996年进行。为此目的，从该流域收集水和表面沉积物样品在邻近的非工业化水域每隔2公里。在非受影响的流域中使用金属和放射性核素浓度，我们将水和沉积物基线浓度计算为上部95百分位值。湖泊和河流水中的基线pH，226ra和铀在6.8,10mbq中心点L-1和2.5 mu g中心点L- 1中相似。对于沉积物，基线湖沉积物表现出高于河流沉积物的放射性核素浓度。我们计算了湖泊沉积物的基线浓度在2,115 BQ中心点kg-1 210pb，535 bq中心点kg-1 210po，218 bq中心点kg-1 226ra，235 bq中心点kg-1 228th，184，184 bq中心点kg- 1 230和223 BQ中心点kg-1 232th。我们收集的，湖泊湖泊中金属水平的基线浓度为98mg kg-1ni，119mg kg-1 zn，112mg kg-1 pb和19 mg kg-1。两个沉积物核心曲线以及表面沉积物，以估计基线放射性核素活性和金属浓度，并从工业化流域中量化历史释放。沉积物核心曲线反映了基线条件，在1996年1955年从1955年开始释放的基线条件，并于1996年将其污染到其封闭。预工业沉积物层中的金属浓度低于休伦湖的表面沉积物，表明大气沉积。我们的研究表明，在这种非受影响的流域中收集表面沉积物可产生铀和放射性核素的基线浓度。对于金属，由于远程来源的远程大气运输，收集表面沉积物可以产生环境金属浓度。相比之下，沉积型材可以提供金属和放射性核素的基线浓度。在蛇流域的情况下，我们报告说，截至1993年Quirke Lake的水质已恢复，额外的沉积物核心将更好地评估沉积物恢复。

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