The background value of cadmium (Cd) in soil and water sediments in the karst area is 0.31 mg kg⁻¹, with a typical high background of cadmium geochemistry. It is well-known that Cd is classified as a highly toxic metal. Therefore, at the Yelang reservoir in Guizhou province, eco-toxicological tests were carried out using Daphnia pulex. The Geo-Accumulation Index and Potential Ecological Risk Index were used to assess the environmental risk of Cd in sediments. The Cd contents in the sediments of Yelang reservoir ranged from 2.51 to 5.23 mg kg⁻¹, while the LC₅₀ values of the acute toxicity test of Daphnia pulex and Cd at 24, 48, 72, and 96 h were 1.17, 0.50, 0.24, and 0.12 mg L⁻¹, respectively, giving a Safe Concentration threshold of Cd of 1.20 × 10⁻³ mg L⁻¹ in the water body. Based on curve fitting the solid–liquid two-phase distribution model of cadmium in Yelang reservoir was Y = 7.59 × 10⁻⁹ × X^2.58 (R² = 0.9995). The safety threshold sediment Cd concentration was 103 mg kg⁻¹, and was much higher than the Cd content in the sediment of the Yelang reservoir. The Geo-Accumulation Index (I_geo 2.432–3.491) results show that the sediments had reached medium-strong or strong risk levels. The Potential Ecological Risk Index ($E_r^i$ 242.8–505.9) reached a very high or extremely high-risk level. However, due to high concentrations of Ca²⁺ and Mg²⁺, and the pH being in the neutral–alkaline range of water body in karst areas, the Daphnia ecotoxicology evaluation method showed slight ecological risk, quite different from other assessment results, thus this method could be considered to use in such areas.

中文翻译：

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基于水蚤生态毒理学的喀斯特湖底沉积物中镉的生态风险评价

喀斯特地区水土沉积物中镉（Cd）的背景值为0.31 mg kg ^-1，具有典型的镉地球化学背景。众所周知，Cd 被归类为剧毒金属。因此，在贵州省夜郎水库，利用溞水蚤进行生态毒理学试验。地积累指数和潜在生态风险指数用于评估沉积物中镉的环境风险。夜郎水库沉积物中Cd含量为2.51～5.23 mg kg ^-1，而水蚤和Cd在24、48、72和96 h急性毒性试验的LC ₅₀值为1.17、0.50、0.24 , 和 0.12 mg L ^-1，分别给出了水体中1.20 × 10 ^-3 mg L ^-1的 Cd 安全浓度阈值。根据曲线拟合夜浪油藏镉的固液两相分布模型为Y=7.59×10 ^-9 ×X ^2.58（R ² = 0.9995）。安全阈值沉积物Cd 浓度为103 mg kg ^-1，远高于夜郎水库沉积物中Cd 的含量。Geo-Accumulation Index ( I _geo 2.432–3.491) 结果表明沉积物已达到中强或强风险水平。潜在生态风险指数（${乙}_r^{\mathrm{一世}}$242.8–505.9) 达到非常高或极高的风险水平。但由于Ca ²⁺和Mg ²⁺浓度较高，且岩溶地区水体pH值在中性-碱性范围内，水蚤生态毒理学评价方法生态风险较小，与其他评价结果存在较大差异，因此这种方法可以考虑在这些领域使用。