Air And Water In Volatile Organic Sulfur Detection Method And System Design

Sulfur cycle is an important component of global biogeochemical cycles. Volatileorganic sulfur compounds （VSCs） are Principal Precursors of sulfate aerosol andcloud condensation nuclei in troposphere and stratospheric and thus have greatimpacts on global climate change and acid rain. The basis of the study the VSCs is toestablish a kind of practical and accurate method of determining the concentration ofVSCs and then to evaluate the impact of VSCs on climate and environment.According to current research results, we independently developed detection systemfor analyzing the VSCs in the air and water. The main studies and results in the paperare outlined as follows:A detection system was established to detect total concentration of trace volatilesulfur compounds （VSCs） in air and water. A cryogenic trap-thermal desorptiondevice which was composed of a semiconductor cryogenic unit with a trap tube filledwith Tenax-TA sorbent and a semiconductor heating unit. These two units weredeveloped to concentrate VSCs from environmental water samples and desorbed themfrom the trap tube, respectively. Under high temperature and combustion-supportinggas, the VSCs were completely oxidized into sulfur dioxide. Analyzing the content ofsulfur dioxide through ultraviolet fluorescence method indirectly help to gain the totalconcentration of volatile organic sulfur compounds. The detection system comprised atemperature-controlled purge tube, a drying assembly, an inorganic sulfur scrubbingassembly, a cryogenic trap-thermal desorption device, a flameless furnace unit, anU.V. Fluorescence SO2Analyzer. TENAX material was adopted to trap VSCs.The best experimental conditions for measuring atmospheric and water sampleswere determined. TENAX trap tube at5℃can achieve the effective capture ofstandard gas DMS and CS₂as the flow rate of carrier gas was300mL/min. DMS andCS₂can be resolved from the trap tube and be oxidized into SO₂with the desorptiontemperature of150℃, the oxidation temperature of1000℃. The purge time, purgetube temperature at20min and65℃were considered as optimized condition whenwater purging are proceeding. The relative standard deviation of DMS and CS₂wereless than6%. The drying assembly, an inorganic sulfur scrubbing assemblies wereverified no influence to the standard gases of DMS and CS₂.The system was applied to test the concentration of total VSCs in the air around Qingdao from February2011to January2012. The range of total VSCsconcentrations in air was from82to1421ng/m3and the relative standard deviationwas less than9.7%. The total concentration VSCs in fish pond water were determinedby the system under optimized conditions and the range of total VSCs concentrationsin fish pond water was from1503to1911ng/m3and the relative standard deviation ofmeasuring water samples is8.91¹0.21%. The limit of detection was6ng/L, spikedrecovery was92.6%¹04.7%.