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Since non-methane hydrocarbons (NMHCs) include numerous species of volatile organic compounds (VOCs), they are the only indicators that can characterize the total amount of VOCs in ambient air. More than 90 % of NMHC instruments in the market use the indirect method for NMHC determination, utilizing a gas chromatograph to determine the concentrations of total hydrocarbons (THCs) and methane in air. However, we found indirect NMHC measurements incorrectly characterized the low NMHC concentrations in the urban air. These measurements were hindered by the uncertain changes in the errors associated with low THC concentrations, humidity and macroscopic substances (oxygen) in the atmosphere. In this study, we conducted intercomparisons between 10 instruments in the market using different operation principles; among these, two used the direct method, and eight used the indirect method. For the indirect method, experiments showed that when the NMHC concentration was 50 ppbC , the errors in the measurement results were 32 % (CH4) and 98 % (THC) when compared to theoretical values. The oxygen content in the sample gas directly affected the response of the THC. The effect of increased oxygen content on the analysis of oxygen-containing substances was more significant than that of the increase in hydrocarbon substances. The response of dry zero was blank, and the response value increased non-linearly with relative humidity (RH). RH had a great impact on low NMHC concentrations of nearly 50 %. For the direct method, although various flow designs were applied for different instruments, the results indicated that they generally showed lower interference and higher accuracy for the ambient NMHC measurements. With the online direct methods, we obtained more reliable data and characteristics for low-concentration NMHCs in downtown Shanghai. The median of hourly data was 163.1 ppbC , and the highest ratio of the maximum and minimum concentrations of NMHCs reached 9.56 in a single day. [ABSTRACT FROM AUTHOR]

Since non-methane hydrocarbons (NMHCs) include numerous species of volatile organic compounds (VOCs), they are the only indicators that can characterize the total amount of VOCs in ambient air. More than 90 % of NMHC instruments in the market use the indirect method for NMHC determination, utilizing a gas chromatograph to determine the concentrations of total hydrocarbons (THCs) and methane in air. However, we found indirect NMHC measurements incorrectly characterized the low NMHC concentrations in the urban air. These measurements were hindered by the uncertain changes in the errors associated with low THC concentrations, humidity, and macroscopic substances (oxygen) in the atmosphere. In this study, we conducted intercomparisons between 10 instruments in the market using different operation principles; among these, two used the direct method and eight used the indirect method. For the indirect method, experiments showed that when the NMHC concentration was 50 ppbC, the errors in the measurement results were 32 % (CH4) and 98 % (THC) when compared to theoretical values. The oxygen content in the sample gas directly affected the response of the THC. The effect of increased oxygen content on the analysis of oxygen-containing substances was more significant than that of the increase in hydrocarbon substances. The response of dry zero was blank, and the response value increased non-linearly with relative humidity (RH). RH had a great impact on low NMHC concentrations of nearly 50 %. For the direct method, although various flow designs were applied for different instruments, the results indicated that they generally showed lower interference and higher accuracy for the ambient NMHC measurements. With the online direct methods, we obtained more reliable data and characteristics for low-concentration NMHCs in downtown Shanghai. The median of hourly data was 163.1 ppbC, and the highest ratio of the maximum and minimum concentrations of NMHCs reached 9.56 in a single day. [ABSTRACT FROM AUTHOR]

Given the increasingly serious ecological and environmental problems in China, research on enterprises' low-carbon sustainable development behavior (LCSDB) has become a heated discussion. This is also because enterprises are a primary source of carbon emissions and environmental pollution. From the perspective of the board of directors' capital (BODC), this study considers empirical evidence from 286 enterprises listed on the Shanghai and Shenzhen stock exchanges in China from 2008 to 2016 to examine the BODC's impact on enterprises' LCSDB and its mechanisms. A group test is conducted using the enterprise's property, nature of rights, and region, among other factors, to investigate the heterogeneity of the impact of board capital on enterprises' LCSDB and its regulatory role. The research indicates (1) an increase in BODC promotes enterprises' LCSDB. (2) An awareness of social responsibility (AOSR) plays an intermediary role in the relationship between BODC and corporate LCSDB. (3) Media attention enhances the BODC's role in promoting enterprises' LCSDB. (4) Government regulatory factors promote the BODC's positive impact on LCSDB. These findings significantly impact the effectiveness of decision-makers within the company, the governance mechanism to address climate change risks, and the possible connection between corporate governance reform and carbon-related policies. [ABSTRACT FROM AUTHOR]