Biosurfactant-assisted phytoremediation of potentially toxic elements in soil: Green technology for meeting the United Nations Sustainable Development Goals

Biosurfactants are biomolecules produced by microorganisms, low in toxicity, biodegradable, and relatively easy to synthesize using renewable waste substrates. Biosurfactants are of great importance with a wide and versatile range of applications, including the bioremediation of contaminated sites. Plants may accumulate soil potentially toxic elements(PTEs), and the accumulation efficacy may be further enhanced by the biosurfactants produced by rhizospheric microorganisms. Occasionally, the growth of bacteria slows down in adverse conditions, such as highly contaminated soils with PTEs. In this context,the plant's phytoextraction capacity could be improved by the addition of metal-tolerant bacteria that produce biosurfactants. Several sources, categories,and bioavailability of PTEs in soil are reported in this article, with the focus on the cost-effective and sustainable soil remediation technologies, where biosurfactants are used as a remediation method. How rhizobacterial biosurfactants can improve PTE recovery capabilities of plants is discussed, and the molecular mechanisms in bacterial genomes that support the production of important biosurfactants are listed. The status and cost of commercial biosurfactant production in the international market are also presented.     

Copper localization in Cannabis sativa L. grown in a copper-rich solution

Summary With the aim to examine its potential as a renewable resource to decontaminate polluted soils, electron microscopy combined with X-ray microanalysis was used to investigate the localization of copper in Cannabis sativa grown in hydroponic copper-rich culture. Cu was found to accumulate preferentially in the upper leaf epidermal cells; it was also detected in spiculae and in abaxial trichomes too. Primary bast fibres seem to be not involved in copper accumulation.     

东南景天提取污染土壤中锌的潜力研究

通过盆栽实验研究了两种生态型东南景天提取污染土壤中锌的能力,结果表明,超积累生态型东南景天具有很强的忍耐土壤中高浓度锌、铅和镉的能力,并能从土壤中吸收和转移大量锌到地上部,超积累生态型东南景天地上部的Zn含量为7062～9558mg／kg,非超积累生态型为256～407mg／kg,超积累生态型东南景天地上部的Zn总积累是非超积累生态型的4l～62倍。矿山土壤添加稻草后,促进了超积累生态型东南景天的生长,地上部生物量显著提高,且锌含量也明显增加。种植超积累生态型东南景天后土壤乙酸铵提取态锌有上升趋势,和种植前比较,在矿山土壤和污染土壤上分别增加了4．3％和9．4％,种植超积累生态型东南景天后土壤交换态锌和有机结合态锌明显增加,残渣态锌减少,而对非生态型,种植前后土壤中锌的化学形态没有什么变化。添加菜籽饼和稻草对两种土壤中Zn的化学形态转化均没有显著性影响,其原因有待进一步研究。这些研究结果表明,超积累生态型东南景天具有较强的修复锌污染土壤的潜力。     

土壤铅镉污染修复中植物修复技术的研究进展

近年来,由于工业"三废"治理不彻底、化肥农药的过量使用以及剩余污泥回用农田等原因,导致我国土壤重金属污染日趋严重。重金属无法被降解,易在土壤中累积,并通过生物富集和生物放大效应对环境和人类健康造成危害。土壤重金属污染修复与治理成为研究热点。重金属污染治理包括客土法、石灰改良法、化学淋洗法、植物修复等,这些方法各具特点,均有其适用范围,得到国内外学者的普遍关注。文章针对土壤铅镉污染的植物修复技术展开综述,并对可能影响植物修复的一些因素进行了介绍,最后对本领域的研究方向进行了展望,以期为同行业的从业者提供一定的借鉴。     

盐土植物提取修复重金属污染盐土研究进展

土壤盐渍化和重金属污染已成为世界性的环境问题,世界众多地区同时受到高浓度可溶性盐和重金属污染,其对人体健康构成严重威胁,盐土的重金属污染问题引起人们的广泛关注。与甜土植物相比,盐土植物可在含有高浓度Na+和Cl-的盐土中生存甚至旺盛生长,因此更利于植物修复盐土重金属污染。近年来,国内外众多学者相继开展了盐土植物修复重金属污染盐土的研究,一系列重要研究成果被报道,鉴于有关盐土植物提取修复重金属污染盐土的综述尚罕见报道,综述了盐土植物对盐和重金属胁迫的耐性机理、植物提取修复潜力及其影响因素的最新研究进展,并对盐土植物提取修复的可行性、植物修复效率、局限性和挑战进行了深入讨论,对未来研究方向进行了展望。以期为今后盐土植物提取修复盐土重金属污染提供有益参考。     

Examination of Correlation between Histidine,Sulfur, Cadmium,and Cobalt Absorption by Morus L., Robinia pseudoacacia L., and Populus nigra L.

We investigated the relationship between histidine, sulfur (S), cadmium (Cd), and cobalt (Co) in three hyperaccumulating plants, namely Morus L., Robinia pseudoacacia L., and Populus nigra L. The samples were collected around Gaziantep and Bursa cities because these two cities have more than 1,500,000 populations, in Turkey, as well as they are highly industrialized. Analyses for Cd, Co, and S were done by inductively coupled plasma mass spectrometer (ICP-MS) and for histidine by high-performance liquid chromatography-mass spectrometer (HPLC-MS). Related with role of histidine in detoxification, it was considered that histidine did not bind nickel (Ni) directly in the cytoplasm, but in transport vesicles because metal-rich vesicles had been observed in the cytoplasm of cells of hyperaccumulator plants. The linear correlations were r_his-Cd = 0.70 and r_his-Co = 0.74 for P. nigra L., r_his-Co = 0.52 and r_Co-S = 0.76 for R. pseudoacacia L. It was concluded that P. nigra L. leaves can be considered as hyperaccumulators.     

Phytoextractability of Cd from Soil by Some Oilseed Species as Affected by Sewage Sludge and Farmyard Manure

A pot experiment was conducted on cadmium (Cd)–enriched (0, 40, 80, 120, 160 mg Cd kg^?1 soil, using CdCl₂), untreated (Unamended), 3% sewage sludge–treated (SS-amended), and 3% farmyard manure–treated (FYM-amended) soils to evaluate the phytoextractibility of Cd by three oilseed crop species (viz., Brassica juncea, Brassica napus, and Eruca sativa). Visual observation showed that at or above 40 ppm Cd, some light chlorotic symptoms, resembling iron (Fe) chlorosis, appeared after 2 to 3 weeks of germination. The extent of chlorosis followed the order Eruca sativa > Brassica napus > Brassica juncea, and for amendment treatments Unamended > SS-amended > FYM-amended soils. Both the amendments resulted in an increased biomass production in comparison to the Unamended soil, with the effect being more pronounced for FYM. The dry-matter yield of different plant parts followed the order FYM-amended > SS-amended > Unamended soils. For plant species, it followed the order Brassica juncea > Brassica napus > Eruca sativa. The Cd concentration in different plant parts followed the order leaf > stem > seed in all the three species. Amongst the species, the concentration followed the order Brassica napus > Brassica juncea > Eruca sativa, and for amendment treatments SS-amended > Unamended > FYM-amended soils. The mean Cd uptake by different plant species followed the order Brassica juncea > Brassica napus > Eruca sativa, and for amendment treatments SS-amended soil > Unamended soil > FYM-amended soil. The amounts of exchangeable, carbonate bound, Fe-Mn oxide bound, and organic-matter-bound fractions of Cd in the postharvest soil samples increased with the addition of Cd in soil. However, the residual fraction did not change much. At comparable levels of Cd additions, application of sewage sludge as well as FYM resulted in decreases in the exchangeable and Fe-Mn oxide–bound fractions and an increase in the organic-matter-bound fraction. The beneficial effect of sewage sludge and FYM on biomass production was attributed to (i) improvement in the physicochemical and biological environment of the growth medium, (ii) additional supply of essential nutrients, and (iii) possible decrease in toxic effect of added Cd through organo-metallic complexation reactions.     

EDTA-Enhanced Phytoremediation of Lead-Contaminated Soil by Corn

EDTA-enhanced phytoremediation by corn (Zea mays L.) of soil supplemented with 500 mg L^?1 lead (Pb) was examined. The chelate EDTA was used in order to increase Pb bioavailability at four levels: 0 (control), 0.5 (low), 1.0 (medium), and 2.5 mmol kg^?1 (high). Plants were grown under controlled conditions in a growth-chamber with supplementary light. An EDTA concentration of 5.0 mmol kg^?1 was lethal to plants. At high and medium EDTA levels plants grew significantly less than control ones. Lead concentrations in corn leaves increased with increased EDTA levels. Plants subjected to medium EDTA level had the greatest root to shoot Pb translocation. Plants subjected to high EDTA level showed high phosphorus (P) uptake and translocation within plants. Therefore, possibly it was not only Pb that caused toxic effect on plants, but also the high internal concentration of P that in turn could have complexed active Fe.     

锰尾渣改良对4种植物吸收锰的影响

采用盆栽法研究锰尾渣改良对商陆（Phytolacca acinosa）、美洲商陆（Phytolacca americana）、繁穗苋（Amaranthus paniculatus）和酸模叶蓼（Polygonum lapathif olium）4种植物吸收锰的影响。将锰尾渣与土壤混合进行基质改良,有利于植物生长。基质含80%锰尾渣时,商陆、美洲商陆和繁穗苋3种植物生长正常,吸收锰多。商陆和美洲商陆2种植物对锰尾渣耐受性强,生物量大,植物提取锰多;繁穗苋对锰尾渣耐受性较强。在锰尾渣污染区进行植物修复时,商陆和美洲商陆可作为首选植物,繁穗苋可作为辅助共生植物,采用锰尾渣含量为80%的基质改良方式最佳。     

Phytoremediation of Vineyard Copper-Contaminated Soil and Copper Mining Waste by a High Potential Bioenergy Crop (Helianthus annus L.)

Phytoremediation is a helpful technique to remediate copper-contaminated areas. The aim of this study was to evaluate sunflower phytoremediation capacity in two vineyard copper-contaminated soils (Inceptisol and Mollisol) and a copper mining waste. Nutrient uptake, copper phytoaccumulation, translocation factor (TF), and bioaccumulation factor (BCF) of sunflower were evaluated after 57 days of growth. Plants grown in both the Mollisol and Inceptisol soils showed high plant height. Fresh biomass was high in the Mollisol in the shoots and roots and also demonstrated the highest values on the tolerance index (TI). The BCF after growth in all three of the copper contaminated soils as Inceptisol, Mollisol, and copper mining waste showed reduction of this index value to 0.19, 0.24, and 0.03, respectively against native soil (Mollisol under natural conditions (4.71). Sunflowers have some important characteristics such as high phytomass production, copper phytoaccumulation, and potential use to biofuel. Thus, sunflower is a potential candidate to phytoremediation of vineyard copper-contaminated soils.