Role of reactive manganese and oxygen species in the KMnO4/Na2SO3 process for purification of algal-rich water and membrane fouling alleviation.

Ultrafiltration (UF) is a highly efficient technique for algal-rich water purification, but it is heavily contaminated due to the complex water characteristics. To solve this problem, potassium permanganate (KMnO4) oxidation enhanced with sodium sulfite (Na2SO3) was proposed as a pretreatment means. The results showed that the end-normalized flux was elevated from 0.10 to 0.91, and the reversible fouling resistance was reduced by 99.95%. The membrane fouling mechanism also changed obviously, without the generation of cake filtration. Regarding the properties of algal-rich water, the zeta potential was decreased from -29.50 to -5.87 mV after KMnO4/Na2SO3 pretreatment, suggesting that the electrostatic repulsion was significantly reduced. Meanwhile, the fluorescent components in algal-rich water were significantly eliminated, and the removal of dissolved organic carbon was increased to 67.46%. In the KMnO4/Na2SO3 process, reactive manganese species (i.e., Mn(V), Mn(III) and MnO2) and reactive oxygen species (i.e., SO4•- and •OH) played major roles in purifying algal-rich water. Specifically, SO4•-, •OH, Mn(V) and Mn(III) could effectively oxidize algal pollutants. Simultaneously, the in-situ adsorption and coagulation of MnO2 could accelerate the formation of flocs by decreasing the electrostatic repulsion between cells, and protect the algal cells from being excessive oxidized. Overall, the KMnO4/Na2SO3 process showed significant potential for membrane fouling alleviation in purifying algal-rich water.

Heat transfer processes in 'Shine Muscat' grapevine leaves in solar greenhouses under different irrigation treatments.

The use of solar greenhouses in China is increasing because they permit environmental conditions to be controlled. Studies of the heat transfer processes in the leaves of plants cultivated within solar greenhouses are needed. Here, we studied heat transfer processes in 'Shine Muscat' grapevine leaves under moderate deficit irrigation (MDI), severe deficit irrigation (SDI), and full irrigation (FI) treatments under varying weather conditions. The stomatal conductance, leaf temperature, and transpiration rate of both shade and sun grapevine leaves were measured, and the effects of ambient temperature and relative humidity on these variables were determined. A thermal physics model of the leaves was established to explore the heat dissipation process. On sunny days, the transpiration heat transfer of sun leaves in the MDI, SDI, and FI treatments was 2.62 MJ m-2·day-1, 2.44 MJ m-2·day-1, and 3.86 MJ m-2·day-1and 0.818 MJ m-2·day-1, 0.782 MJ m-2·day-1, and 1.185 MJ m-2·day-1 on rainy days, respectively. There was a significant difference in transpiration heat transfer under fully irrigated and deficit irrigation conditions under different weather conditions. Furthermore, transpiration heat transfer accounted for 41.49 % and 25.03 % of the total heat transfer of sun leaves in the FI treatment and 33.94 % and 29.43 % of the total heat transfer of shade leaves on rainy days, respectively, indicating that relative humidity plays a key role in determining transpiration heat transfer and leaf temperature and that its effect was greater on sun leaves than on shade leaves.

Field investigation of non-uniform environment in a Venlo-type greenhouse in Yangling, China.

Non-uniform environmental conditioning has established substantial energy-saving and conditioning effects in residential buildings, however, few studies on the technology applied in greenhouses have been conducted. Semi-enclosed greenhouse development is hindered by energy consumption. To better apply non-uniform environmental conditioning technology in greenhouses, it is necessary to investigate the non-uniform characteristics of field environment parameters. Therefore, spatial and temporal measurements of indoor temperature and relative humidity in a Venlo-type greenhouse in Yangling, China, were conducted on June 5-11, 2022. Temperature and humidity sensors were arranged in the greenhouse at 4.5 m intervals, in the canopy, cultivation, center, and root areas. Temperature and humidity measurement points on the greenhouse walls were selected. The measurement results showed large fluctuations in the indoor temperature and relative humidity over time. The difference between indoor and outdoor average temperatures ranged from -5-10 °C and temperatures unsuitable for tomato growth were identified, although some passive conditioning methods such as ventilation and water spraying were employed, which indicates the necessity of active heating and cooling. Based on the measured data, the nonuniformity coefficients of temperature and relative humidity in different directions in the greenhouse were calculated. A larger non-uniformity in the vertical direction was found compared to that in the horizontal direction. These results suggest the possibility of non-uniform environmental conditioning. A rough estimation of the energy consumption by the two different condition modes, namely zone-specific and overall conditioning, was made. A huge energy saving of 69.6 % by the zone-specific conditioning mode was revealed compared to the overall conditioning. This implies a huge advantage in energy efficiency by non-unform environmental conditioning technologies applied in greenhouses. The study provides useful data for understanding non-uniform environments in greenhouses and the application of non-uniform environmental conditioning technologies.