Nitrite is a naturally-occurring inorganic compound that occurs in aquatic environments as an intermediary between nitrate and ammonia in the nitrogen cycle. It is a contaminant of potential concern resulting from anthropogenic activities in some cases. While the acute toxicity of nitrite has been characterized in previous studies, its sublethal toxicity is less understood. To determine the sublethal toxicity of nitrite on freshwater organisms, a suite of organisms was tested including: two salmonids (Oncorhynchus mykiss and O. kisutch), an alga (Pseudokirchneriella subcapitata), an aquatic macrophyte (Lemna minor), and three invertebrates (Ceriodaphnia dubia, Chironomus dilutus, and Neocloeon triangulifer). Test organisms were exposed to nitrite concentrations ranging between 0.02 and 1.28 mg/L nitrite (NO₂-N). The toxicity tests were conducted according to procedures specified in standardized methods, allowing for the estimation of multiple endpoints for each test species. Species sensitivity distributions (SSDs) were generated using endpoints from the toxicity testing results, as well as data from previous studies, from which water chemistry approximated that used in the tests (i.e., < 5 mg/L chloride, an important toxicity-modifying factor for nitrite). The mayfly, N. triangulifer, was the most sensitive species, followed by the two salmonids (which represented the second and third most sensitive species), although they were not as sensitive to nitrite exposure as reported in previous studies. The fifth percentile hazard concentration (HC5) generated from the SSD could be used for derivation of regulatory benchmarks and threshold values for site-specific aquatic risk assessments.

Graphic Abstract

中文翻译：

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亚致死毒性亚硝酸盐对一组水生生物的评价，以支持慢性环境水质基准的推导

亚硝酸盐是一种天然存在的无机化合物，作为氮循环中硝酸盐和氨之间的中间体存在于水生环境中。在某些情况下，它是由人为活动引起的潜在关注的污染物。虽然以前的研究已经描述了亚硝酸盐的急性毒性，但对其亚致死毒性的了解较少。为了确定亚硝酸盐对淡水生物的亚致死毒性，对一组生物进行了测试，包括：两种鲑鱼（Oncorhynchus mykiss和O. kisutch）、一种藻类（Pseudokirchneriella subcapitata）、一种水生植物（Lemna small）和三种无脊椎动物（Ceriodaphnia ） dubia、Chironomus dilutus和Neocloeon triangulifer）。测试生物体暴露于浓度范围在 0.02 和 1.28 mg/L 亚硝酸盐 (NO ₂ -N) 之间的亚硝酸盐中。毒性测试是根据标准化方法中规定的程序进行的，允许估计每个测试物种的多个终点。物种敏感性分布 (SSD) 是使用来自毒性测试结果的端点以及来自先前研究的数据生成的，其中水化学近似于测试中使用的数据（即 < 5 mg/L 氯化物，一个重要的毒性调节因子亚硝酸盐）。蜉蝣，N. triangulifer，是最敏感的物种，其次是两种鲑鱼（代表第二和第三最敏感的物种），尽管它们对亚硝酸盐暴露的敏感性不如先前研究中报道的那么敏感。SSD 产生的第五个百分位危害浓度 (HC5) 可用于推导针对特定地点的水生风险评估的监管基准和阈值。

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