Environmental Sciences, School of Interdisciplinary Arts and Sciences, University of Washington Tacoma, Tacoma, Washington, United States of America.
Water and Land Resources Division, King County Department of Natural Resources and Parks, Seattle, Washington, United States of America.
PLoS One. 2023 Oct 19;18(10):e0293214. doi: 10.1371/journal.pone.0293214. eCollection 2023.
Lake sediments store metal contaminants from historic pesticide and herbicide use and mining operations. Historical regional smelter operations in the Puget Sound lowlands have resulted in arsenic concentrations exceeding 200 μg As g-1 in urban lake sediments. Prior research has elucidated how sediment oxygen demand, warmer sediment temperatures, and alternating stratification and convective mixing in shallow lakes results in higher concentrations of arsenic in aquatic organisms when compared to deeper, seasonally stratified lakes with similar levels of arsenic pollution in profundal sediments. In this study we examine the trophic pathways for arsenic transfer through the aquatic food web of urban lakes in the Puget Sound lowlands, measuring C and N isotopes-to determine resource usage and trophic level-and total and inorganic arsenic in primary producers and primary and secondary consumers. Our results show higher levels of arsenic in periphyton than in other primary producers, and higher concentrations in snails than zooplankton or insect macroinvertebrates. In shallow lakes arsenic concentrations in littoral sediment are similar to deep profundal sediments due to arsenic remobilization, mixing, and redeposition, resulting in direct arsenic exposure to littoral benthic organisms such as periphyton and snails. The influence of littoral sediment on determining arsenic trophic transfer is evidenced by our results which show significant correlations between total arsenic in littoral sediment and total arsenic in periphyton, phytoplankton, zooplankton, snails, and fish across multiple lakes. We also found a consistent relationship between percent inorganic arsenic and trophic level (determined by δ15N) in lakes with different depths and mixing regimes. Cumulatively, these results combine to provide a strong empirical relationship between littoral sediment arsenic levels and inorganic arsenic in edible species that can be used to screen lakes for potential human health risk using an easy, inexpensive sampling and analysis method.
湖泊沉积物中储存着历史上农药和除草剂使用以及采矿作业产生的金属污染物。普吉特海湾低地的历史区域性冶炼作业导致城市湖泊沉积物中的砷浓度超过 200μg As g-1。先前的研究已经阐明了在浅湖沉积物中，与具有相似砷污染程度的深层季节性分层湖泊相比，如何通过沉积物需氧量、较暖的沉积物温度以及交替分层和对流混合，导致水生生物中砷浓度更高。在这项研究中，我们研究了城市湖泊水生食物网中砷通过食物链的转移途径，测量了 C 和 N 同位素，以确定资源利用和营养水平，以及初级生产者和初级和次级消费者中的总砷和无机砷。我们的结果表明，底栖藻类中的砷含量高于其他初级生产者，而贻贝中的砷含量高于浮游动物或昆虫大型无脊椎动物。在浅湖中，由于砷的再迁移、混合和再沉积，湖滨沉积物中的砷浓度与深层深湖沉积物相似，导致直接暴露于湖滨底栖生物，如底栖藻类和贻贝。湖滨沉积物对确定砷营养转移的影响在我们的研究结果中得到了证明，这些结果表明，多个湖泊中，湖滨沉积物中的总砷与底栖藻类、浮游植物、浮游动物、贻贝和鱼类中的总砷之间存在显著相关性。我们还发现，在不同深度和混合模式的湖泊中，无机砷与营养水平（由 δ15N 确定）之间存在一致的关系。总之，这些结果结合起来，为湖滨沉积物砷水平与可食用物种无机砷之间提供了一个强有力的经验关系，可以使用一种简单、廉价的采样和分析方法，通过筛选湖泊来评估潜在的人类健康风险。
