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| Effects of modified biochar on Cr speciation and enzyme activity in farmland soil |
| Received:May 25, 2021 |
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| KeyWord:soil;modified biochar;Cr(Ⅵ);speciation distribution;enzyme activity |
| Author Name | Affiliation | E-mail | | CHEN Yijie | College of Coastal Agricultural Sciences, Guangdong Ocean University, Zhanjiang 524088, China | | | WU Weijian | College of Coastal Agricultural Sciences, Guangdong Ocean University, Zhanjiang 524088, China | | | LI Gaoyang | College of Coastal Agricultural Sciences, Guangdong Ocean University, Zhanjiang 524088, China | | | ZHANG Weijian | College of Coastal Agricultural Sciences, Guangdong Ocean University, Zhanjiang 524088, China | | | WEI Ting | College of Coastal Agricultural Sciences, Guangdong Ocean University, Zhanjiang 524088, China | | | LIN Zhong | College of Chemistry and Environmental Sciences, Guangdong Ocean University, Zhanjiang 524088, China | | | ZHEN Zhen | College of Coastal Agricultural Sciences, Guangdong Ocean University, Zhanjiang 524088, China | zz19830302@163.com |
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| Abstract: |
| In order to study the effects of the modified cow dung biochar on Cr speciation and enzyme activity in soil, we investigated the effects of HNO3-modified biochar, FeCl3-modified biochar, and unmodified cow manure biochar on Cr morphology and distribution, soil physicochemical properties, and enzyme activities. The results showed that external surface area, total pore volume, and micropore surface area of HNO3-modified biochar were 2.86 m2·g-1, 0.004 cm3·g-1, and 0.01 m2·g-1 and those of FeCl3-modified biochar were 11.09 m2·g-1, 0.013 cm3·g-1, and 2.20 m2·g-1 higher than those of unmodified biochar, respectively. However, the average pore size decreased by 1.28 nm and 3.86 nm for HNO3-modified biochar and FeCl3-modified biochar, respectively. Modified biochars had similar types of functional groups, with an increased abundance of hydroxyl(-OH), carboxyl(-COOH), and carbonyl(C=O). Batch sorption experiments revealed that all biochars had remarkable sorption performance; the highest Cr(Ⅵ) reduction was observed with FeCl3-modified biochar application (up to 15.90 mg·g-1). After a soil incubation test(60 d), the acid soluble, reducible, and oxidizable fractions of Cr(Ⅵ) in soil amended with added biochar were approximately 0.97%~2.15%, 0.28%~0.94% and 4.70%~9.40%, respectively, lower than the values for the controlled study. The residue fraction(approximately 42.3%~45.2%) of Cr(Ⅵ) was significantly(P<0.05) higher in soil amended with modified biochar than in soil amended with unmodified biochar(38.6%) and not amended with biochar(32.8%). Correlation analysis results show that biochar remarkably changed soil physiochemical properties by increasing soil pH, organic matter, and cation exchange capacity and promoted the conversion of Cr(Ⅵ) from an acid soluble state to a residue state in soil; these are the greatest effects of FeCl3- modified biochar. The added biochar in soil caused a significant increase in the levels of urease, sucrase, and dehydrogenase in soil and reduced the toxicity of Cr(Ⅵ). Furthermore, soil enzyme activity with modified biochar was significantly higher than that of the controlled study and that with unmodified biochar. Our findings prove that modified biochar can be used as a low-cost and environment-friendly adsorbent to effectively remediate soils contaminated with Cr(Ⅵ). |
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