Abstract:Large-scale stacking of phosphogypsum (PG) poses potential environmental risks to groundwater and soil. Mercury (Hg), as one of the most toxic heavy metals, exhibits strong bioaccumulative and persistent characteristics, threatening ecosystems and human health. Therefore, accurate determination of Hg content in PG is critical for both the comprehensive utilization of PG and the assessment of its environmental risk. This study established a rapid method for direct solid sampling determination of Hg in PG using DMA-80 mercury analyzer, with optimal instrument conditions determined through orthogonal design experiments and method results validated by different method comparison. Under the high-purity oxygen atmosphere, PG samples were dried at 250 °C, thermally decomposed at 650 °C for 90 s, and the released mercury was catalytically reduced to elemental mercury, forming a gold amalgam. The amalgam was subsequently heated rapidly at 900 °C to release mercury vapor, which was measured by cold vapor atomic absorption at 253.7 nm. Calibration curves were established over Hg mass ranges of 0.5 ~ 400 ng (long detection cell: 0.1 ~ 25 ng, short detection cell: 25 ~ 400 ng) with r >0.9995. The method detection limit (LOD) was 0.006 ng. Relative standard deviations (RSD, n=7) for different samples were less than 2.7%, with the recoveries between 92.1% ~ 101.3%. The proposed method and the GB/T 23349-2020 atomic fluorescence spectrometry (AFS) method were applied to determine Hg content in PG samples collected from seven phosphorus chemical enterprises. The concentrations of Hg were all in the range of 0.1 ~ 0.6 mg/kg. Statistical analysis by t-test showed no significant difference between the datasets (t = 0.019 < t 0.05, 12 = 2.179), indicating that the determination results of the two methods were essentially consistent. Traditional AFS method requires wet-acid or microwave digestion during the pretreatment stage, which not only consumes large amounts of acid reagents and involves lengthy analytical procedures, but also leads to Hg volatilization losses during digestion, potentially resulting in the compromised accuracy and stability of the analytical results. In contrast, the direct mercury analyzer method eliminates chemical digestion, reduces the use of strong acid reagents, and completes single-test analysis automatically within 7 minutes, enabling accurate and rapid batch determination of Hg in industrial waste residue PG.