Abstract
Establishing an analytical method to interpret trace element changes is crucial for methane hydrate seepage tracking, exploration, and exploitation. However, research on this important issue is still limited, posing a challenge for trace element determination in marine mud samples. In this study, we first applied t-tests on independent samples for XRF tests with soil QC samples and sea mud samples. The results showed no statistically significant difference between sea mud samples and soil QC samples. Thus, soil QC samples were used for the methodology study.
We investigated the microwave digestion procedure, the selection of spectral line wavelengths for analytical tests, the limit of detection (LOD) and quantification (LOQ), spiked recoveries, precision, accuracy, and the interference of coexisting elements on spectral line selection. Results indicated that the use of inverse aqua regia and 1 mL HF as a mixed acid system is effective. Copper and zinc elements require temperatures above 150 °C, lead and cadmium above 180 °C, and chromium should not exceed 210 °C to avoid volatilization. Analytical spectra for copper, zinc, chromium, and lead were selected at 324.752, 213.857, 267.716, and 220.353 nm wavelengths. The correlation coefficients of the standard curves were above 0.9997, with detection limits ranging from 0.0004 to 0.0105 mg/L and quantification limits from 0.0017 to 0.0419 mg/L. Spiked recoveries ranged from 95.5% to 103.7%. The method's accuracy was verified using soil standard samples (GSS-4 and GSS-5). The ICP-MS method tested sea mud samples for t-test comparison, and statistical results showed no significant difference.