Kouping Lu

Using biochar for remediation of soils contaminated with heavy metals and organic pollutants

Soil contamination with heavy metals and organic pollutants has increasingly become a serious global environmental issue in recent years. Considerable efforts have been made to remediate contaminated soils. Biochar has a large surface area, and high capacity to adsorb heavy metals and organic pollutants. Biochar can potentially be used to reduce the bioavailability and leachability of heavy metals and organic pollutants in soils through adsorption and other physicochemical reactions. Biochar is typically an alkaline material which can increase soil pH and contribute to stabilization of heavy metals. Application of biochar for remediation of contaminated soils may provide a new solution to the soil pollution problem. This paper provides an overview on the impact of biochar on the environmental fate and mobility of heavy metals and organic pollutants in contaminated soils and its implication for remediation of contaminated soils. Further research directions are identified to ensure a safe and sustainable use of biochar as a soil amendment for remediation of contaminated soils.

Lead accumulation and tolerance of Moso bamboo (Phyllostachys pubescens) seedlings: applications of phytoremediation *

A hydroponics experiment was aimed at identifying the lead (Pb) tolerance and phytoremediation potential of Moso bamboo (Phyllostachys pubescens) seedlings grown under different Pb treatments. Experimental results indicated that at the highest Pb concentration (400 μmol/L), the growth of bamboo seedlings was inhibited and Pb concentrations in leaves, stems, and roots reached the maximum of 148.8, 482.2, and 4282.8 mg/kg, respectively. Scanning electron microscopy revealed that the excessive Pb caused decreased stomatal opening, formation of abundant inclusions in roots, and just a few inclusions in stems. The ultrastructural analysis using transmission electron microscopy revealed that the addition of excessive Pb caused abnormally shaped chloroplasts, disappearance of endoplasmic reticulum, shrinkage of nucleus and nucleolus, and loss of thylakoid membranes. Although ultrastructural analysis revealed some internal damage, even the plants exposed to 400 μmol/L Pb survived and no visual Pb toxicity symptoms such as necrosis and chlorosis were observed in these plants. Even at the highest Pb treatment, no significant difference was observed for the dry weight of stem compared with controls. It is suggested that use of Moso bamboo as an experimental material provides a new perspective for remediation of heavy metal contaminated soil owing to its high metal tolerance and greater biomass.摘要目的探索毛竹在修复铅污染土壤的植物修复潜力。创新点使用了毛竹作为一种全新的植物修复材料进行研究。 得到了毛竹幼苗在铅胁迫下的生长与生理反应情况, 不同植物组织对铅的吸收与积累情况, 铅胁迫下毛竹幼苗表层与细胞超微结构的特征。方法根系形态分析(图3)、 植物重金属含量分析(表1)、 扫描电镜分析(图4)和透射电镜分析(图5)。结论各组织部位铅浓度的值揭示了, 毛竹是一个很好的固定铅污染土壤的植物材料; 但是由于毛竹茎的高生物量, 也可以作为铅污染土壤的植物修复材料。 在0∼200 μmol/L铅处理下, 毛竹的生物量与根系形态没有显著性差异, 生长正常未出现中毒症状。 通过扫描电镜观察铅胁迫导致叶片的气孔减少, 根与茎内含物增多。 通过透射电镜观察高浓度的铅胁迫导致部分细胞内部叶绿体变形、 内质网消失、 细胞核与核仁缩小和类囊体膜消失。 尽管超微结构观察到细胞内部的损害, 但是未出现视觉的毒性症状。 毛竹铅的高耐性与茎的高生物量, 提供了毛竹作为材料修复土壤重金属铅更大的可能性。

Cu induced changes of ultrastructure and bioaccumulation in the leaf of Moso bamboo (Phyllostachys pubescens)

ABSTRACT The effects of Copper (Cu) on growth of Moso bamboo (Phyllostachys heterocycla (Carr.) Mitford cv. pubescens) were investigated. The dry weight of Moso bamboo was inhibited and significant differences were evident under Cu stress as compared to the control (CK). Solution culture experiments indicated that Moso bamboo had a strong ability to accumulate Cu in shoots. Copper accumulation in the stem was stronger than the leaves; the stem/root ratio could reach 0.20 under Cu stress. The changes in cell walls, stomata, vacuoles, and starch grains content were observed via scanning electron microscopy and transmission electron microscopy. The ultrastructural analysis revealed that the excessive Cu concentrations caused deformities in the chloroplasts and transformation and even disappearance of endoplasmic reticulum. Moso bamboo as an experimental material serves as a new tool for remediation of heavy metal contaminated soils due to its metal tolerance and excessive biomass production.

Using Biochar for Remediation of Contaminated Soils

In recent years, soil contamination has become a global environmental problem. Biochar is a porous and carbon-rich material produced from pyrolysis of biomass residues from agricultural and forestry production. It can be used to immobilize heavy metals and organic pollutants in soil through adsorption. Here we report results obtained from our recent studies focusing on the interactions between biochar and soil contaminants. Incubation and pot experiments were carried out to investigate the effect of biochar type, application rate, and particle size on soil properties, bioavailability, mobility, and redistribution of the heavy metals in soil and the accumulation of heavy metals in the plants. Batch equilibration method was used to explore the effect of biochar type, aging process, dosage, and soil organic carbon content on adsorption and desorption of organic pollutants (e.g., phthalic acid esters, or PAEs) in soil. Incubation and pot trials were conducted to evaluate the impact of biochar on the degradation and bioavailability of PAEs in soils. Our results demonstrate that biochar can potentially be used as soil amendment for remediation of soils contaminated with heavy metals and organic pollutants. The efficacy of biochar application on immobilization of contaminants varies with the type, application rate, and particle size of biochars, soil properties, and contaminant types.