Heavy metal remediation in soil with chemical amendments and its impact on activity of antioxidant enzymes in Lettuce (Lactuca sativa) and soil enzymes

Abstract

Chemical amendments have been used to remediate soils contaminated with heavy metals. However, there is little understanding on the impacts of these amendments on the physiological and biochemical functions of plants and soil. This study used in situ microcosm experiment to understand the effect of chemical amendments on antioxidant and soil enzyme activity in plant and soil with respect to heavy metal reduction. Three chemical amendments-acid mine drainage sludge (AMDS), limestone (LS), and steel slag (SS)-were applied to soil at 3, 5, and 10% mixing ratios, and lettuce (Lactuca sativa) was cultivated in that soil for 30 days. The results showed that bioavailable Cd and Pb in soil was reduced by 9.8-40.5% and 4.2-92.5%, respectively. The most efficient amendment for heavy metal reduction was AMDS. The uptake of Cd and Pb also decreased by 0.5-66.1 and 21.6-79.5%, respectively, depending on the amendment type and application ratio. The activity of three antioxidants-catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR)-was generally higher than the control with no amendments. This result indicated that there was minimal inhibition of antioxidant activity due to the reduction of heavy metal uptake. Also, no significant difference was observed in chemical amendments applied soil compared to control in terms of soil enzyme activity. However, correlation analysis between heavy metal concentration in soil and two soil enzyme activities showed that significantly negative correlation (p < 0.01) was observed between bioavailable Pb in soil and acid-phosphatase activity. This result might indicate that impact of bioavailable Pb was much higher than Cd in terms of inhibition of soil enzyme activity. Overall, the application of chemical amendments to heavy metal polluted had a positive effect on plant physiological function and soil enzyme activity with a reduction in bioavailable heavy metals in soil and plants.

Analysis of Major Bacteria and Diversity of Surface Soil to Discover Biomarkers Related to Soil Health

“…The pH and electrical conductivity of the samples were determined for a 1:5 soil:water ( w / v ) suspension using a pH meter and conductivity meter (MP220, Mettler Toledo, Columbus, OH, USA) [ 4 ]. The cation exchange capacity was analyzed using the 1 M CH 3 COOH extraction method [ 2 ]. The soil organic content was measured as described by Walkley and Black.…”

“…The soil organic content was measured as described by Walkley and Black. Effective phosphoric acid was determined using the Bray No.1 method with molybdenum blue dye and measured on a UV spectrophotometer (UV-1800, Shimadzu, Kyoto, Japan) [ 2 ]. The inorganic nitrogen content, as NH 4 -N and NO 3 -N, was determined using a QuikChem automated ion analyzer (QuikChem 6000 Series, Lachat Instruments, Milwaukee, WI, USA), after extraction with 2 M KCl [ 3 ].…”

“…Next-generation sequencing (NGS)-based molecular techniques have been used to study soil microbial diversity and soil microorganisms useful for producing high-quality plants (agricultural soil environment and agriculture-related microorganisms). These studies reported the bacterial and fungal diversity according to the specific treatment of field soil; microbial diversity according to soil depth on a poplar farm; association between soil depth and native and exotic plant species; and comparison of the soil microbiota in natural and re-seeded grassland [ 2 , 3 , 4 , 5 ]. The results suggested that the soil depth is a major factor affecting the networking between the microbiota structure and abiotic factors, including interactions with fungi at approximately 1 m below the soil surface and microbial diversity at depths of 0–20 and ≥21 cm.…”

Cotton straw biochar and compound Bacillus biofertilizer reduce Cd stress on cotton root growth by regulating root exudates and antioxidant enzymes system

“…Heavy metals, especially Cd, can interfere with plant physiological processes by stimulating H 2 O 2 generation and inhibit plant growth ( Lai et al., 2020 ). Previous studies have shown that soil Cd pollution in farmlands is closely related to the excessive application of chemical fertilizers and pesticides and wastewater irrigation ( Hong et al., 2020 ). Cd in soil is easily absorbed by plant roots and transmitted upward to other tissues.…”

Applications of Biochar and Modified Biochar in Heavy Metal Contaminated Soil: A Descriptive Review

“…At present, the remediation methods of heavy-metal-contaminated soil are mainly divided into physicochemical remediation [10,11], chemical remediation [12], phytoreme-Sustainability 2021, 13, 14041 2 of 18 diation [13], and bioremediation [14]. Physicochemical remediation involves changing the pH, redox conditions, or ion composition of soil by adding amendments to achieve the purpose of passivating heavy metals in the soil [15].…”