Search

A visual/smartphone colorimetric system was developed for the sensitive and selective detection of sulfide ion (S2−) using chemical vapor generation (CVG) as a gaseous sampling technique. S2− in samples were converted into H2S after the addition of H2SO4, which separated from the solution during CVG process, ensuring high efficiency of vapor generation (sensitivity) and eliminated interferences (selectivity). The H2S was subsequently reacted with Pb-BTC and PbS was thus formed, causing the test paper turned to black. It was utilized for the detection of S2− by visual/smartphone colorimetric system. Detectable limits of 0.05 μg/mL and 0.2 μg/mL were obtained under smartphone mode and visual mode, respectively. Furthermore, this colorimetric system was successfully used for the analysis of S2− in several beer samples and water samples, with recoveries ranging 97 %–111 %. This system represents a potential miniaturized, easy used and high-effective method for rapid and on-site detection of S2−.

A gas pressure meter-based portable/miniaturized analytical kit was established for rapid and on-site detection of oxalate. Potassium permanganate (KMnO4) and oxalate solution were mixed together in bottle-in-bottle reaction device, a simple oxidation reaction process occurred within 6 min and carbon dioxide (CO2) was generated, inducing the pressure of the sealed bottle changed, which was measured by a portable gas pressure meter. A detectable range of 0.1–6 μmol mL−1 and a detection limit of 0.064 μmol mL−1 were achieved. The proposed analytical method was further used for the analysis of several real samples (spinach, beverages and water samples), with the recoveries of 89–111%. Considering the interferences from the complicated matrix, calcium chloride (CaCl2) was served as a precipitant, oxalate (C2O42−) was precipitated with Ca2+ to form precipitation (CaC2O4), CaC2O4 was then separated from the matrix by centrifuge/filter, eliminating the interferences. It is a rapid, easy-used and interference-free analytical system/device for oxalate on-site and real time analysis.

A miniaturized/portable dual-mode colorimetric analytical system was established for inorganic arsenic determination in honey and drinking water samples. Hydride generation (HG) was utilized as a sampling technique for this colorimetric system, because of its high generation efficiency and efficient matrix separation. AsH3 was generated via HG and then reacted with HAuCl4, gold nanoparticles (Au NPs) were formed on the paper sheet, leading the paper color changed from light yellow to dark blue, it could be readout by naked-eye (visual colorimetric mode) and a smartphone (RGB readout mode) simultaneously. The accuracy and potential application for field analysis were further confirmed by the analysis of two water samples, four honey samples and two certified reference water samples (BWB2440-2016 and GBW08650), good recoveries (90–116%) were obtained for those samples and their spiked samples.

The modular heat storage wall is a new type of solar greenhouse wall structure, which has the advantages of fast construction and good heat storage ability. This study provides data reference and practical value for producing modular heat storage wall in the construction of a solar greenhouse. In this paper, we used different heat storage materials to construct the modular wall. In the winter thermal environment test, soil module solar greenhouse (SG) and stone module solar greenhouse (PG) were controlled against each other in two greenhouses. The test results for 28 consecutive days (31 January 2021 9:00 to 28 February 2021 9:00) showed that both greenhouses could effectively increase the temperature in greenhouse by 10–12 °C. The average temperature of SG was 0.86 °C lower than that of PG during the daytime (09:00–17:00) and 0.44 °C higher than that of PG during the nighttime (17:00–09:00). Under typical sunny conditions, the average temperature differences between the inlet and outlet of SG in the heat storage and exothermic stage was less than that of PG, and the relative humidity difference was greater than that of PG. This indicated that SG had a better performance of heat preservation than PG and could raise the nighttime temperature rapidly. Under the condition of a typical cloudy day, the average temperature difference between the inlet and outlet was SG < PG and the relative humidity difference was SG > PG in the exothermic stage, which was consistent with the conclusion of sunny days. In the storage and exothermic stages of typical sunny days and cloudy days, the total heat exchange of SG was 464.87, 110.44 and 54.82 MJ and the total heat exchange of PG was 264.16, 61.60 and 46.89 MJ, respectively. Moreover, the heat storage and release of SG were more than that of PG in all stages. In summary, the thermal performance of the modular heat storage wall heliogreenhouse could meet the growth of tomato crop, in which the heat transfer performance of SG was optimum.

In order to improve the thermal insulation and storage performance of Chinese solar greenhouses in winter, a novel assembled Chinese solar greenhouse (ACSG) without energy supplement in cold climatic areas was designed to evaluate and compare its thermal performance with that of conventional Chinese solar greenhouse (CSG). The thermal properties of both greenhouses were tested in field on cold winter days in Ningxia, China. The results indicated that the land utilization rate of ACSG was 19.3% higher than that of CSG. On a typical sunny day (the lowest outdoor temperature was -22.0°C) and typical cloudy day (the lowest outdoor temperature was -19.7°C) during the experiment, the minimum indoor temperature of ACSG was respectively 1.7°C and 2.0°C higher than that of CSG. The results for 24 consecutive days (the average outdoor daily minimum air temperature was -19.0°C) showed that the average minimum indoor temperature of ACSG was 1.4°C higher than that of CSG (p<0.05). The modular soil wall attached with colored steel polystyrene boards would be exploited as the north wall of CSG in Yinchuan area. [ABSTRACT FROM AUTHOR]

In order to investigate the application performances of the solar greenhouses with new types of backwalls (greenhouse W2, and greenhouse W3) and the ordinary clay brick backwall greenhouse (greenhouse W1), and provide a theoretical basis for the construction of solar greenhouses in Yangling Demonstration Zone, Shaanxi, China, two greenhouses with different new types of backwall were designed. One of the backwall was built with lightweight aggregate concrete block (greenhouse W2) and that of the other one was assembled with a row of sand-filled cement pipes (greenhouse W3). The tested greenhouses were constructed in Yangling Demonstration Zone. Based on the data collected on typical sunny and cloudy days, the indoor temperature, inside wall temperature, and the heat flow of the greenhouses with new types of backwalls were compared with those detected in the ordinary clay brick backwall solar greenhouse, and the tested results were numerically simulated. According to the comparison of the physiological indicators of tomatoes planted in the greenhouses and the construction costs, the greenhouse type with the best practicability was found. The results indicated that: The average air temperature in greenhouses W1, W2, and W3 and outside was 15.1°C, 15.9°C, 17.3°C, and -0.4°C on the night of a sunny day, and the air temperature in W3 was the highest. The average air temperature in greenhouses W1, W2, and W3 and outside were 9.5°C, 13.3°C, 11.0°C, and -5.5°C on the night of a cloudy day, the air temperature in W2 was the highest. In the depth of 0-330 mm from the interface of the backwalls, the walls were obviously affected by the solar radiation, and the temperature changed greatly. The wall temperature on the sunny days exhibited an ascending order of W1, W2, and W3, while on the cloudy days was in the ascending order of W1, W3, and W2. The wall of W3 absorbed the most heat during the daytime and released the most heat at night on a sunny day, while W2 exhibited the second most heat absorption during the daytime, however, it exhibited the highest heat release at night on a cloudy day, which were almost equaled to its heat absorption. Tomatoes in W3 grew well and exhibited the highest yield, and this greenhouse had the lowest construction costs. Comprehensively considering the physiological indicators of tomatoes and the corresponding construction costs of greenhouses, W3 has the best application performance in Yangling Demonstration Zone. [ABSTRACT FROM AUTHOR]