Effects of salinity in food waste on the growth of black soldier fly larvae and global warming potential analysis

Cultivating black soldier fly larvae (BSFL) has proved to be a potential technology to realize simultaneous recycling of food waste (FW) and production of biofuels or proteins. Due to different dietary habits, the FW salinity usually varies in regions and, thus, could affect the biotransformation of BSFL. The current study investigated the effects of FWs salinity on the BSFL growth and composition distribution in the salinity range of 0.2–6 %. Results showed the final body length, final body weight, and crude protein content of prepupa reached the maximum with 1 % salinity, which was 22.06 ± 0.18 mm, 198.18 ± 3.23 mg, and 40.93 ± 3.82 %, respectively. FW with 0.5 % salinity was the most favorable for BSFL to accumulate lipids, with crude lipids content of 34.76 ± 1.60 %. Due to the unique salt metabolic mechanism, salt can be effectively excreted by BSFL, which enabled it to grow normally in a 2 % salinity culture substrate. However, when the salinity exceeds 4 %, the growth parameters, such as the growth time and survival rate, were reduced by more than 50 %. BSFL treatment has more environmental value than landfill, and the salinity adjustment was beneficial to further reduce the global warming potential (GWP) net impact. In summary, the salinity of food waste has been established as a critical factor. Appropriate modulation of salinity will enhance the utilization of substrates by BSFL and contribute to the alleviation of global warming. This study offers valuable guidance for the efficient and sustainable rearing of BSFL

PMF and PSCF based source apportionment of PM2.5 at a regional background site in North China

To apportion regional PM2.5 (atmospheric particles with aerodynamic diameter < 2.5 mu m) source types and their geographic pattern in North China, 120 daily PM2.5 samples on Beihuangcheng Island (BH, a regional background site in North China) were collected from August 20th, 2014 to September 15th, 2015 showing one-year period. After the chemical analyses on carbonaceous species, water-soluble ions and inorganic elements, various approaches, such as Mann-Kendall test, chemical mass closure, ISORROPIA II model, Positive Matrix Factorization (PMF) linked with Potential Source Contribution Function (PSCF), were used to explore the PM2.5 speciation, sources, and source regions. Consequently, distinct seasonal variations of PM2.5 and its main species were found and could be explained by varying emission source characteristics. Based on PMF model, seven source factors for PM2.5 were identified, which were coal combustion + biomass burning, vehicle emission, mineral dust, ship emission, sea salt, industry source, refined chrome industry with the contribution of 48.21%, 30.33%, 7.24%, 6.63%, 3.51%, 3.2%, and 0.88%, respectively. In addition, PSCF analysis using the daily contribution of each factor from PMF result suggested that Shandong peninsula and Hebei province were identified as the high potential region for coal combustion + biomass burning; Beijing-Tianjin-Hebei (BTH) region was the main source region for industry source; Bohai Sea and East China Sea were found to be of high source potential for ship emission; Geographical region located northwest of BH Island was possessed of high probability for sea salt; Mineral dust presumably came from the region of Mongolia; Refined chrome industry mostly came from Liaoning, Jilin province; The vehicle emission was primarily of BTH region origin, centring on metropolises, such as Beijing and Tianjin. These results provided precious implications for PM2.5 control strategies in North China