Effect of humic acid on seedling growth and trace metal accumulation of pak choi ( Brassica chinensis L.) cultivated on
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RESEARCH ARTICLE
Effect of humic acid on seedling growth and trace metal accumulation of pak choi (Brassica chinensis L.) cultivated on molybdenum slag-spiked soil Dong Chen 1,2 & Zhong-wen Meng 1 & Yi-ping Chen 1 Received: 3 January 2020 / Accepted: 17 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The growth performance and trace metal accumulation of pak choi (Brassica chinensis L.) were investigated to evaluate the ameliorative effect of humic acid on molybdenum (Mo) slag-spiked calcareous soil. Calcareous soil spiked with 5.0% (w/w) slag was amended with humic acid derived from leonardite from 0 to 5.0% (w/w). With increasing application rate, humic acid enhanced the antioxidative capacity of pak choi seedling, as indicated by increases in the activities of antioxidant enzymes (superoxide dismutase, catalase, and peroxidase) and a decrease in malondialdehyde content; humic acid application also increased total chlorophyll content, leaf area, seedling height, and fresh biomass of pak choi. These stimulation effects started to decrease above 2.5–5.0% application of humic acid. The contents of trace metals (Cu, Mn, Zn, As, Cd, and Pb) in the aboveground part of pak choi seedling generally decreased at low rates (0.5% and 1.0%), and then increased with higher rates (2.5% and 5.0%) of humic acid application. Health risk assessment of trace metals based on target hazard quotient (THQ) suggested that consuming pak choi grown on these soils is safe. Low rate (0.5%) of humic acid reduced the potential health risk, while high rates (2.5% and 5.0%) accumulated trace metals and increased health risk. Humic acid could be added to Mo slag-spiked calcareous soil for the yield and food safety of pak choi, but the overuse of humic acid should be avoided. Keyword Soil amendment . Industrial slag . Antioxidant enzyme . Trace metal . Calcareous soil . Health risk
Introduction The utilization of metallurgical slag, especially from the iron and steel smelting processes, as soil fertilizers or amendments has been well investigated over the past years (Das et al. 2019). Slag generally contain high amounts of inorganic oxides; a typical example is steel slag, which mainly consists of CaO, SiO2, and Fe2O3/FeO, with small parts of MnO, MgO, and P2O5 (Yi et al. 2012). These oxides change soil physicochemical properties through mineral nutrition, acid neutralization, adsorption, precipitation, ion-exchange, and acting as
Responsible Editor: Gangrong Shi * Yi-ping Chen [email protected] 1
State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, No. 97 Yanxiang Road, Xi’an 710061, Shaanxi, China
2
University of Chinese Academy of Sciences, Beijing 100049, China
electron acceptors (Das et al. 2019). Numerous studies have shown that slag supplies inorganic nutrients to crops (Haynes et al. 2013), limes acidic soils (Li et al. 2010), stabilizes arsenic (As) and trace metals in acidic multi-metal contaminated soil (Gu et al. 2011; Lee et al. 2
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