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A rotation experiment was conducted in a greenhouse with three vegetable crops on red yellowish soil (RYS) and silt loamy soil (SLS) to study Cd accumulation in pak choi ( Brassica chinensis L.), tomato ( Lycopersicon esculentum), and radish ( Raphanus sativus L.). Critical Cd concentrations in the two soils were evaluated for these vegetables based on human dietary toxicity. Cadmium was added as Cd(NO 3) 2 at a rate of 0-7.00 mg Cd kg (-1) soil. Shoot growth was not inhibited by Cd except for radish grown on RYS. A small amount of Cd stimulated growth of the vegetables. Cadmium concentration in edible parts of the vegetables generally increased with Cd concentration in soils but was higher in RYS than SLS. The distribution of Cd in pak choi and tomato decreased in the order root > shoot > fruit, but the order was shoot > root for radish. When Cd content in the edible parts reached maximum contaminant levels for safety food standards, the soil total Cd concentrations were 0.327 and 0.120 mg kg (-1) in RYS and 0.456 and 0.368 mg kg (-1) in SLS for pak choi stem and radish, respectively, whereas ammonium acetate-extractable Cd was 0.066 and 0.089 mg kg (-1) in RYS and 0.116 and 0.092 mg kg (-1) in SLS for pak choi leaf and tomato, respectively, based on food safety standards.

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Chitin biomass, a rich renewable resource, is the second most abundant natural polysaccharide after cellulose. Conversion of chitin biomass to high value-added chemicals can play a significant role in alleviating the global energy crisis and environmental pollution. In this review, the recent achievements in converting chitin biomass to high-value chemicals, such as 5-hydroxymethylfurfural (HMF), under different conditions using chitin, chitosan, glucosamine, and N-acetylglucosamine as raw materials are summarized. Related research on pretreatment technology of chitin biomass is also discussed. New approaches for transformation of chitin biomass to HMF are also proposed. This review promotes the development of industrial technologies for degradation of chitin biomass and preparation of HMF. It also provides insight into a sustainable future in terms of renewable resources.