Fengliang Zhao

Sorption of ammonium and phosphate from aqueous solution by biochar derived from phytoremediation plants

The study on biochar derived from plant biomass for environmental applications is attracting more and more attention. Twelve sets of biochar were obtained by treating four phytoremediation plants, Salix rosthornii Seemen, Thalia dealbata, Vetiveria zizanioides, and Phragmites sp., sequentially through pyrolysis at 500 °C in a N2 environment, and under different temperatures (500, 600, and 700 °C) in a CO2 environment. The cation exchange capacity and specific surface area of biochar varied with both plant species and pyrolysis temperature. The magnesium (Mg) content of biochar derived from T. dealbata (TC) was obviously higher than that of the other plant biochars. This biochar also had the highest sorption capacity for phosphate and ammonium. In terms of biomass yields, adsorption capacity, and energy cost, T. dealbata biochar produced at 600 °C (TC600) is the most promising sorbent for removing contaminants (N and P) from aqueous solution. Therefore, T. dealbata appears to be the best candidate for phytoremediation application as its biomass can make a good biochar for environmental cleaning.

PURIFICATION OF REFINERY WASTEWATER BY DIFFERENT PERENNIAL GRASSES GROWING IN A FLOATING BED

Four species of perennial grasses [Geophila herbacea O Kumtze (GHK), Lolium perenn CV. Caddieshack (LCC), Lolium perenne Topone (LPT) and Lolium perenne L. (LPL)] were used to remove nutrients and pollutants from refinery wastewater, of which the average concentration of total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (CODMn), total petroleum hydrocarbons (TPH) were 15.6 mg L−1, 0.6 mg L−1, 142.8 mg L−1 and 1720 mg L−1, respectively. These perennial grasses had performed extremely well in removing the nutrients and pollutants and were capable of removing up to 60% of TN and 56% of TP from the refinery wastewater during 35 days treatment period, to which plant uptake contributed only 5%–10% and 10%–20%. The removal rates of CODMn and TPH were fluctuating within 52% to 67% and 40% to 55%, respectively. The nutritional value of these perennial grasses as animal feeds such as crude protein, crude fat, crude fiber, crude ash and nitrogen-free extraction after growing in refinery wastewater for 35 days were analyzed and the results suggested that these indicators were superior to national animal feed thresholds, with its nitrites and several heavy metals including zinc (Zn), arsenic (As), cadmium (Cd), and lead (Pb) concentration far below the thresholds. We concluded that perennial grass floating-bed system was effective for purifying refinery wastewater during its growing season and harvested perennial grass had great value as animal feeds.

Variation in copper and zinc tolerance and accumulation in 12 willow clones: implications for phytoextraction *

Willows (Salix spp.) have shown high potential for the phytoextraction of heavy metals. This study compares variations in copper (Cu) and zinc (Zn) tolerance and accumulation potential among 12 willow clones grown in a nutrient solution treated with 50 μmol/L of Cu or Zn, respectively. The results showed differences in the tolerance and accumulation of Cu and Zn with respect to different species/clones. The biomass variation among clones in response to Cu or Zn exposure ranged from the stimulation of growth to inhibition, and all of the clones tested showed higher tolerance to Cu than to Zn. The clones exhibited less variation in Cu accumulation but larger variation in Zn accumulation. Based on translocation factors, it was found that most of the Cu was retained in the roots and that Zn was more mobile than Cu for all clones. It is concluded that most willow clones are good accumulators of Zn and Cu.概要研究目的柳树(Salix spp.)已广泛用于修复重金属污染, 而且修复效率与树种及无性系有关。 目前涉及柳树研究主要为铜(Cu)和锌(Zn)的毒性效应, 而不是富集能力。 本研究以中国常见的柳树无性系评价对Cu 和Zn 耐性与富集能力。创新要点目前大多数研究仍集中Cu 和Zn 对柳树的毒性效应, 尤其是Cu, 对它们富集能力仍没有评价。 中国为柳树的主要分布区。 本文以12 种优良的常见柳树无性系, 通过温室营养液法评价对Cu 和Zn 耐性及富集潜力差异。 利用柳树无性系的耐性与富集变异, 旨在选择高耐性与高富集的无性系, 提高环境修复效率和加快修复进程。研究方法选择高生物量12 种柳树无性系, 采用温室营养液培养法添加Cu 或Zn 处理, 测定生物量参数并计算耐性指数, 估计耐性差异; 用原子吸收法测定组织中金属浓度并计算金属位移系数, 评价富集差异。重要结论无性系对Cu 和Zn 耐性显著不同, 生物量变化从无影响、 抑制到促进生长。 无性系对Cu 耐性高于对Zn 耐性, 无性系对Zn 富集变异幅度大于对Cu 富集变异幅度。 Cu 主要富集于根部, 而Zn 较易运输到地上部分。 总之测定的大部分柳树无性系为Cu 与Zn 高富集植物, 显示出较高的植物提取能力。

Variations of growth, nitrogen accumulation and nitrogen use efficiency among 18 willow clones under two nitrogen regimes

Willows (Salix spp.) have excellent capacity for acquiring nutrients, and are widely used for removing excess nutrients in wastewater purification system. In this study, 18 willow clones were evaluated in terms of growth parameters, nitrogen (N) accumulation and N use efficiency under two N regimes (low N and high N) with a sand culture system. Clonal differences were observed in biomass production, relative growth rate, N accumulation and use efficiency under two N regimes, which were contributed to the clone level. For all clones, nitrogen use efficiency was lower under high N condition than under low N condition. Nitrogen removal efficiency differed by 7-fold (low N regime) and 10-fold (high N regime) based on shoot N contents between the lowest and the highest clone. Among all the clones, J799 had the highest N content in shoots, showing largest N removal potential. These results confirmed that growth analysis and nutrient use strategy are efficient method of selecting Salix clones for improving the N removal potential.

Purification of eutrophic water by ryegrass

The present study was carried out to investigate the growth characteristics of different ryegrass (Lolium perenne L.) cultivars and their ability to remediate eutrophic water using floating plant-bed technology. Greenhouse and lake experiments were conducted to evaluate the grass genotypes for water remediation. Twelve cultivars of ryegrass including Grazer, Secale Cerale, Energa, Rustmaster, AngusI, Abundant, AngusII, Jivet, Gulf, Surrey, Major and Barwoltra were grown in the floating plant-bed system. The plant biomass, plant NP (nitrogen and phosphorus) accumulations and the water purification capacity of selected grasses were significantly different (P < 0.05). Abundant, AngusII and Major showed most efficient purification capacity of eutrophic water. In a greenhouse, after 26 days of growth, the eutrophic water was purified to various extents by the different ryegrass cultivars. Nitrogen removal efficiency varied from 52.20% to 73.82% and phosphorus removal efficiency ranged from 75.12% to 84.77%. In a lake experiment at Huajiachi pond, after 162 days of growth, the plant shoot biomass increased from 321.5 to 922.8 g/m(2) dry weight basis, shoot NP accumulation ranged from 61.5 to 168.2 mg m(-2) d(-1) and 11.9 to 47.2 mg m(-2) d(-1) respectively. NP accumulation rate by the various cultivars of ryegrass was highly positively correlated to their biomass production and water purification capacity. Thus, plant biomass could be used as an indicator for assessing purification capacity of a ryegrass cultivar.