Due to the overuse of fossil energy, fossil energy is facing exhaustion. Agricultural biomass such as wheat straw waste is a kind of clean energy which can replace fossil energy and has important scientific research value and broad application prospect. In this paper, wheat straw was used as raw materials, and the straw was converted into lactic acid, oxalic acid and fumaric acid under alkaline hydrothermal conditions. Improve the yield of organic acid by optimizing the reaction conditions such as NaOH concentration, reaction time and reaction temperature. The optimum reaction conditions were as follows: NaOH concentration 1.5 mol/L, reaction temperature 250ºC, reaction time 3 hours, total organic acid yield 13.5%, lactic acid yield 12.1%. The results can provide a new way for the green production of organic acids, and realize the efficient utilization of agricultural waste, reduce environmental pollution. At the same time, can produce good economic benefits, ecological benefits and social benefits.

In order to determine the generating capacity of negative air ions (NAIs) and its relationship with human activities, the NAIs in different functional areas of Hefei, China, were analyzed. And the half residence time was studied by simulated experiments. The results showed that the natural attenuation law of NAIs was complied with this equation: C (t) = 2986.6 × e -0.0141t . Based on the attenuation equation, the coagulation rate α = 0.0141, and the lifespan was about 49.16 min. Combined with the NAIs concentration monitored in different functional areas, it was found that there was a huge difference in background concentration and environmental production or consumption. The background concentration in urban forest area was much higher, indicating that plants were the main source of NAIs. Among them, the urban forest area (UF), water area (WA), culture and education area (CEA) and residential area (RA) produced NAIs, while others consumed. There was a threshold value for the consumption by human activities, which was generally no more than 30% and can reach 50% when the activity was intense. However, no threshold value was found for vehicle activities. These results can provide reference for other mid-latitude inland cities to optimize urban design, and build 'resilient cities'.