Particle- and gas-phase PAHs toxicity equivalency quantity emitted by a non-road diesel engine with non-thermal plasma technology

Effect of gas temperature on carbon soot oxidation via non-thermal plasma: two-dimensional numerical study integrating reactive flow and discharge models

Non-thermal plasma (NTP) efficiently regenerates diesel particulate filters by oxidizing carbon soot (CS) at low temperatures. However, numerical studies on the spatial characteristics of CS oxidation by NTP are scarce. In addition, the influence of background gas heating on the CS-oxidizing performance by NTP remains inadequately understood. This research investigates the impact of gas temperature (323-573 K) on heterogeneous CS oxidation using NTP in a two-dimensional configuration. The results indicate that CS is mainly oxidized by [Formula: see text], [Formula: see text], and [Formula: see text] during NTP treatment. The energy efficiency of CS removal by NTP ranges from 0.1 to 2.6 g kWh-1 for varying gas temperature and applied voltage, consistent with previous research. Higher gas temperatures enhance both CS removal rate and efficiency, whereas higher applied voltages enhance rate at the expense of efficiency. The study also assesses energy conversion efficiency from electrical power input to chemical bonding energy during CS oxidation by NTP, yielding 0.03 to 0.23% efficiency for the considered gas temperature and voltage ranges, with higher temperatures leading to better efficiency.

Effect of temperature control conditions on DPF regeneration by nonthermal plasma

A regeneration test of a diesel particulate filter (DPF) was conducted under different temperature conditions with air as the gas source and a nonthermal plasma (NTP) injection system. We investigated the influence of the ambient temperature on the DPF regeneration performance and the oxidative decomposition amount of particulate matter (PM) and analyzed the changes in the PM oxidation characteristics by thermogravimetric analysis (TGA). The higher the temperature, the lower the decomposition amount of PM was under constant temperature conditions. The decomposition amount of PM was the highest at 80 °C (3.74 g), and the PM at interface P2 was not completely removed. The volume concentrations of the DPF regeneration products (CO and CO₂) were higher under variable than constant temperature conditions. In addition, the peak temperature of interface P1 occurred 10-30 min earlier, complete regeneration occurred at interface P2, and DPF regeneration occurred faster than under temperature conditions. The initial temperature of the control device was 110 °C, and the maximum mass of PM oxidation decomposition was 4.26 g after regeneration for 15 min cooling to 80 °C. The main form of elemental carbon (EC) transformed into the low ignition point component and the oxidation activity was improved after NTP injection.

Changes of diesel particle diameter and surface area distributions by non-thermal plasma

A wide literature has demonstrated that internal combustion engines are the main responsible for the emission of fine particles in urban areas. Within this scope, ultrafine particles within diesel exhausted gas have been widely proven to exert a significantly harmful impact on human health and environment. This scenario has led the research community to turn the attention from particle mass to diameter and surface area. In this paper, non-thermal plasma (NTP) technology was applied to a heavy duty diesel engine. Chemical reactions of diesel particles in plasma zone were analyzed. Additionally, variation in diesel particles' number and surface area distributions, engendered by above reactions, were thoroughly investigated. The results showed that diesel exhausted particles experienced oxidation, aggregation, and crush because of enhanced plasma transports and active species in plasma zone. NTP presents excellent reduction effectiveness of diesel particles covering different sizes. Being more than 50%, the most considerable surface area concentration drop was found in correspondence of 1800 RPM. Differently, the lowest drop of surface area concentration was seen at 1200 RPM. As a result of the NTP actions, surface area concentration distributions were almost the same for diameters being larger than 0.5 μm at different engine modes, except at 900 RPM. This research made a foundation of dropping particle emissions and evaluating the effectiveness of NTP dropping particle harms to human health.

Characterization of a multianalyte GC-MS/MS procedure for detecting and quantifying polycyclic aromatic hydrocarbons (PAHs) and PAH derivatives from air particulate matter for an improved risk assessment

A correct description of the concentration and distribution of particle bound polycyclic aromatic hydrocarbons is important for risk assessment of atmospheric particulate matter. A new targeted GC-MS/MS method was developed for analyzing 64 PAHs including compounds with a molecular weight >300, as well as nitro-, methyl-, oxy- and hydroxyl derivatives in a single analysis. The instrumental LOD ranged between 0.03 and 0.7 pg/μL for PAHs, 0.2-7.9 pg/μL for hydroxyl and oxy PAHs, 0.1-7.4 pg/μL for nitro PAHs and 0.06-0.3 pg/μL for methyl-PAHs. As an example for the relevance of this method samples of PM₁₀ were collected at six sampling sites in Medellin, Colombia, extracted and the concentration of 64 compounds was determined. The 16 PAHs from the EPA priority list contributed only from 54% to 69% to the sum of all analyzed compounds, PAH with high molecular weight accounted for 8.8%-18.9%. Benzo(a)pyrene equivalents (BaP_eq) were calculated for the estimation of the life time cancer (LCR). The LCR according to the samples ranged from 2.75 × 10^-5 to 1.4 × 10^-4 by a calculation with toxic equivalent factors (TEF) and 5.7 × 10^-5 to 3.8 × 10^-4 with potency equivalent factor (PEF). By using the new relative potency factors (RPF) recommended by US Environmental Protection Agency (U.S.EPA) the LCR ranged from 1.3 × 10^-4 to 7.2 × 10^-4. Hence, it was around six times higher than the well-known TEF. The novel method enables the reliable quantification of a more comprehensive set of PAHs bound on PM and thus will facilitate and improve the risk assessment of them.

Polycyclic aromatic hydrocarbon (PAHs) geographical distribution in China and their source, risk assessment analysis

In China, the huge amounts of energy consumption caused severe carcinogenic polycyclic aromatic hydrocarbon (PAHs) concentration in the soil and ambient air. This paper summarized that the references published in 2008-2018 and suggested that biomass, coal and vehicular emissions were categorized as major sources of PAHs in China. In 2016, the emitted PAHs in China due to the incomplete combustion of fuel was about 32720 tonnes, and the contribution of the emission sources was the sequence: biomass combustion > residential coal combustion > vehicle > coke production > refine oil > power plant > natural gas combustion. The total amount of PAHs emission in China at 2016 was significantly decreased due to the decrease of the proportion of crop resides burning (indoor and open burning). The geographical distribution of PAHs concentration demonstrated that PAHs concentration in the urban soil is 0.092-4.733 μg/g. At 2008-2012, the serious PAHs concentration in the urban soil occurred in the eastern China, which was shifted to western China after 2012. The concentration of particulate and gaseous PAHs in China is 1-151 ng/m3 and 1.08-217 ng/m3, respectively. The concentration of particle-bound PAHs in the southwest and eastern region are lower than that in north and central region of China. The incremental lifetime cancer risk (ILCR) analysis demonstrates that ILCR in the soil and ambient air in China is below the acceptable cancer risk level of 10-6 recommended by US Environmental Protection Agency (EPA), which mean that there is a low potential PAHs carcinogenic risk for the soil and ambient air in China.