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In recent years, the removal of hexavalent chromium by green iron nanoparticles (FeNPs) has attracted attention due to the environmental friendliness, low price, and good durability of this adsorbent. In this paper, a new synthetic method was developed and optimized under the aspects of improved synthesis yield and Cr(VI) removal. For the first time, peel extracts of yali pear and FeSO4 were employed in the synthesis of FeNPs (YL-FeNPs), and the synthesis conditions were optimized for five factors including extraction temperature, extraction time, peel mass, Fe2+-extract ratio, and drying method. For optimized synthesis conditions, the following parameters were determined: 27 g of pear peel was extracted with 360 mL of 50 vol% ethanol solution in water at 80 °C for 60 min, the Fe2+-extracts volume ratio was 1:1, and vacuum freeze drying was employed. The optimized YL-FeNPs formed particles of irregular shape with a size in the range of 40–80 nm. As the initial Cr(VI) concentration decreased and the adsorption temperature increased, its removal efficiency improved. After 2 h, a Cr(VI) removal efficiency of 96.8% was achieved for a solution with an initial Cr(VI) concentration of 12 mg/L. The adsorption of Cr(VI) conformed to pseudo-second-order kinetics and the Langmuir adsorption isotherm model. YL-FeNPs exhibited a maximum adsorption capacity of 43.99 mg/g at pH = 5 and 55 °C and demonstrated good adsorption performance in solutions with coexisting anions and real natural water. This research can support the recycling of pear peel waste and provide technical aspects for improving the synthesis efficiency of FeNPs. [ABSTRACT FROM AUTHOR]

As one of the factors affecting water resources, land use is influenced by humans and is of great significance to water resources management. This paper used SWAT model parameter calibration and verification to study the impacts of land use change on green and blue water in Xixi Basin of China from the 1970s to 2000 and 2018, and the inter-annual, monthly and spatial variations of green and blue water were analyzed using multiple averages from 1974 to 1979. The results showed that (1) under rainfall conditions from 1974 to 1979, land use change caused the annual average quantity of green water to decrease from 625.35 mm in 1970s to 619.88 mm in 2018, a decline of 5.47 mm; the annual average quantity of blue water increased from 1019.44 to 1029.59 mm, a change of 10.15 mm. Because of land use change, green water coefficient generally decreased slightly. (2) During the 12 months of a year, green water decreases, and blue water increases were mainly concentrated in May and June. In June with the greatest changes, green water decreased by 5.12 mm, at a rate of 6.28%; blue water increased by 4.33 mm, at a rate of 2.65%. (3) Because of land use change, the green water decreases and blue water increases were mainly concentrated in the upper sub-basins of the basin, and changes were mainly caused by green water decreases and blue water increases from 1970s to 2000. (4) In Taozhou Township, the possible impact of the reduction in green water on rain-fed agriculture should be paid attention to; during the flood season, especially in June, the possible influence of increased blue water on floods in areas such as Hutou Town and Bailai Township should be considered. This study can provide a scientific basis for the rational and efficient use of water resources in a region. [ABSTRACT FROM AUTHOR]

The release of mercury from intertidal sediment to atmosphere was studied based on the simulated experiment. The experiment samples were collected from the Haibo Estuary (S1) and the Licun Estuary (S2) of the Jiaozhou Bay in China, which are seriously polluted with mercury. The results show that the mercury in sediment releases rapidly to atmosphere under solar radiation. After 8 hours of solar radiation, mercury concentrations decrease from 5.62 μg/g and 2.92 μg/g to 2.34 μg/g and 1.39 μg/g in S1 and S2 sediments respectively in summer, and decrease from 5.62 μg/g and 2.92 μg/g to 4.58 μg/g and 2.13 μg/g respectively in winter. The mercury species in the sediment change markedly under solar radiation. The concentrations of mercury bound to organic matter decrease significantly from 2.73 μg/g to 0.31 μg/g in S1 and from 2.07 μg/g to 0.31 μg/g in S2, and the released mercury mainly comes from mercury bound to organic matter. Mercury flux shows distinguishing characteristic of diurnal change, and it increases rapidly in the morning with the rising of solar radiation intensity, but decreases in the afternoon. The mercury flux increases with sediment temperature and solar radiation intensity. The rapid release of mercury in intertidal sediment plays an important role in the regional mercury cycle. [ABSTRACT FROM AUTHOR]