I. Background

The atmospheric concentration of methane (CH₄), a potent greenhouse gas, has been increasing at an unprecedented rate in recent years, reaching historical highs since 2020. Methane has a lifespan of about 10 years in the atmosphere, compared to carbon dioxide (CO₂) which lasts around 100 years. Methane's greenhouse effect is 25 times stronger than that of CO₂, primarily originating from sources such as agriculture, fossil fuel extraction, and waste management. These characteristics make reducing methane emissions a priority for short-term mitigation of anthropogenic global warming. Accurate measurement of methane concentration in the atmosphere is crucial for understanding its environmental impact and formulating emission reduction policies.

This test aims to compare the performance of the HT8600 CH₄ Open-path Analyzer produced by HealthyPhoton with another mature commercial methane analyzer. By comparing the measurements of methane flux and concentration in a farmland setting, the evaluation assesses their performance in precision, sensitivity, and stability.

II. Test Method

The test was conducted in a farmland area in Jinan, a typical agricultural ecosystem that reflects the impact of agricultural activities on atmospheric methane concentration. Specific steps included:

Setting up test points at different locations in the farmland and installing both analyzers.

Conducting multiple measurements from July 7 to July 9, 2024, and recording data.

Analyzing the data to compare the sensitivity, accuracy, and stability of the analyzers.

III. Test Performance

Concentration/EC Flux Comparison

1. Methane Concentration (CH₄ Concentration): The middle section shows the methane concentration measurement values of both analyzers in parts per billion by volume (ppbv). From the graph, it is evident that the measurements of both analyzers are very close, with slight differences observed at certain times.

2. Turbulent Flux (EC Flux): The bottom section displays the variation in turbulent flux (μmol+1s^-1m^-2) measured by both analyzers. While the overall trends of the measurements from both analyzers are consistent, significant differences were observed at certain times, especially during high flux periods.

These findings indicate that the HT8600 and the commercial methane analyzer demonstrate high consistency in measuring methane concentration and turbulent flux, while also revealing some differences under varying conditions.

Original Flux vs. Corrected Flux Comparison

The X-axis represents the corrected turbulent flux (μmol+1s^-1m^-2) measured by the commercial analyzer, and the Y-axis represents the original turbulent flux data (μmol+1s^-1m^-2) from the HT8600. The points in the graph are distributed along a regression line close to Y=1.09X, with an R² value of 0.9868, indicating a very high correlation between the two. This demonstrates that the original flux measured by the HT8600 and the corrected flux measured by the commercial analyzer exhibit high linearity and consistency. The HT8600's performance is well validated, with a data processing process that is easier and potentially less prone to errors caused by correction processes.

Co-Spectral Density Comparison

The Y-axis represents standardized co-spectral density, and the X-axis represents standardized frequency. The co-spectral densities of the three measurement methods are very consistent across most frequency ranges, conforming to classic turbulent spectrum theory (slope of -4/3).

These results indicate that the HT8600 exhibits performance in co-spectral density across different frequencies that is very close to that of the commercial analyzer and the benchmark temperature, demonstrating good performance in dynamic response and frequency resolution.

V. Conclusion

The HT8600 and commercially available methane analyzers demonstrate high consistency in measuring methane concentration and turbulent flux, as well as good performance in dynamic response and frequency resolution.

Both analyzers show high measurement accuracy and stability, providing reliable technical support for environmental monitoring and scientific research, making them ideal choices for atmospheric methane monitoring.

Related Product：HT8600 Open-path CH₄ Anaylzer