In addition to the often-cited advantages of using Arabidopsis thaliana as a model system in plant biological research (1), Arabidopsis has many additional characteristics that make it an attractive experimental organism for studying lea d (Pb) accumulation and tolerance in plants. These include its fortuitous familial relationship to many known metal hyperaccumulators (Brassicaceae), as well as similar Pbaccumulation patterns to most other plants. Using nutrient-agar plates, hydroponic culture, and Pb-contaminated soils as growth media, we found significant variation in Arabidopsis thaliana ecotypes in accumulation and tolerance of Pb. In addition, we have found that Pb accumulation is not obligatorily linked with Pb tolerance, suggesti ng that different genetic factors control these two processes. We also screened ethyl methanesulfonate-mutagenized M2 populations and identified several Pb-accumulating mutants. Current characterization of these mutants indicates that their phenotypes are likely due to alteration of general metal ion uptake or translocation processes since these mutants also accumulate many other metals in shoots. We expect that further characterization of the ecotypes and mutants will shed light on the basic genetic and physiological underpinnings of plant-based Pb remediation. 7. Aromatic nitroreduction of acifluorfen in soils, rhizospheres, and pure cultures of rhizobacteria. Zablotowicz, R. M., Locke, M. A., and Hoagland, R. E. Phytoremediation of soil and water contaminants. Washington, DC : American Chemical Society, 1997. p. 38-53. NAL Call #: QD1.A45-no.664 Abstract: Reduction of nitroaromatic compounds to their corresponding amino derivatives is one of several pathways in the degradation of nitroxenobiotics. Our studies with the nitrodiphenyl ether herbicide acifluorfen showed rapid metabolism to am inoacifluorfen followed by incorporation into unextractable soil components in both soil and rhizosphere suspensions. Aminoacifluorfen was formed more rapidly in rhizospheres compared to soil, which can be attributed to higher microbial populations, espec ially of Gram-negative bacteria. We identified several strains of Pseudomonas fluorescens that possess nitroreductase activity capable of converting acifluorfen to aminoacifluorfen. Factors affecting acifluorfen nitroreductase activity in pure cultures an d cell-free extracts, and other catabolic transformations of acifluorfen, ether bond cleavage, are discussed. Plant rhizospheres should be conducive for aromatic nitroreduction. Nitroreduction by rhizobacteria is an important catabolic pathway for the ini tial degradation of various nitroherbicides and other nitroaromatic compounds in soils under Reduction of nitroaromatic compounds to their corresponding amino derivatives is one of several pathways in the degradation of nitroxenobiotics. Our studies with the nitrodiphenyl ether herbicide acifluorfen showed rapid metabolism to am inoacifluorfen followed by incorporation into unextractable soil components in both soil and rhizosphere suspensions. Aminoacifluorfen was formed more rapidly in rhizospheres compared to soil, which can be attributed to higher microbial populations, espec ially of Gram-negative bacteria. We identified several strains of Pseudomonas fluorescens that possess nitroreductase activity capable of converting acifluorfen to aminoacifluorfen. Factors affecting acifluorfen nitroreductase activity in pure cultures an d cell-free extracts, and other catabolic transformations of acifluorfen, ether bond cleavage, are discussed. Plant rhizospheres should be conducive for aromatic nitroreduction. Nitroreduction by rhizobacteria is an important catabolic pathway for the ini tial degradation of various nitroherbicides and other nitroaromatic compounds in soils under phytoremediation management. 8. Ascorbate: a biomarker of herbicide stress in wetland plants. Lytle, T. F. and Lytle, J. S. Phytoremediation of soil and water contaminants. Washington, DC : American Chemical Society, 1997. p. 106-113. NAL Call #: QD1.A45-no.664 Abstract: In laboratory exposures of wetland plants to low herbicide levels (<0.1 micrograms/mL), some plants showed increased total ascorbic acid suggesting a stimulatory effect on ascorbic acid synthesis occurred; at higher herbicide conce ntrations (greater than or equal to 0.1 micrograms/mL) a notable decline in total ascorbic acid and increase in the oxidized form, dehydroascorbic acid occurred. Vigna luteola and Sesbania vesicaria were exposed for 7 and 21 days respectively to atrazine (0.05 to 1 microgram/mL); Spartina alterniflora 28 days at 0.1 micrograms/mL trifluralin; Hibiscus moscheutos 14 days at 0.1 and 1 microgram/mL metolachlor in fresh and brackish water. The greatest increase following low dosage occurred with S. alterniflo ra, increasing from <600 micrograms/g wet wt. total ascorbic acid to >1000 micrograms/g. Ascorbic acid may be a promising biomarker of estuarine plants exposed to herbicide runoff; stimulation of ascorbic acid synthesis may enable some wetland plant s used in phytoremediation to cope with low levels of these compounds. In laboratory exposures of wetland plants to low herbicide levels (<0.1 micrograms/mL), some plants showed increased total ascorbic acid suggesting a stimulatory effect on ascorbic acid synthesis occurred; at higher herbicide conce ntrations (greater than or equal to 0.1 micrograms/mL) a notable decline in total ascorbic acid and increase in the oxidized form, dehydroascorbic acid occurred. Vigna luteola and Sesbania vesicaria were exposed for 7 and 21 days respectively to atrazine (0.05 to 1 microgram/mL); Spartina alterniflora 28 days at 0.1 micrograms/mL trifluralin; Hibiscus moscheutos 14 days at 0.1 and 1 microgram/mL metolachlor in fresh and brackish water. The greatest increase following low dosage occurred with S. alterniflo ra, increasing from <600 micrograms/g wet wt. total ascorbic acid to >1000 micrograms/g. Ascorbic acid may be a promising biomarker of estuarine plants exposed to herbicide runoff; stimulation of ascorbic acid synthesis may enable some wetland plant s used in phytoremediation to cope with low levels of these compounds. 9. Atmospheric nitrogenous compounds and ozone--is NO(x) fixation by plants a possible solution. Wellburn, A. R. New phytol. 139: 1 pp. 5-9. (May 1998). NAL Call #: 450-N42 Descriptors: ozoneair-pollution nitrogen-dioxide nitric-oxide air-quality tolerancebioremediationacclimatizationnutrient-sources nutrient-uptake plantscultivarsgenetic-variation literature-reviews 10. Atrazine degradation in pesticide-contaminated soils: phytoremediation potential. Kruger, E. L., Anhalt, J. C., Sorenson, D., Nelson, B., Chouhy, A. L., Anderson, T. A., and Coats, J. R. Phytoremediation of soil and water contaminants. Washington, DC : American Chemical Society, 1997. p. 54-64. NAL Call #: QD1.A45-no. 664 Abstract: Studies were conducted in the laboratory to determine the fate of atrazine in pesticide-contaminated soils from agrochemical dealer sites. No significant differences in atrazine concentrations occurred in soils treated with atrazine i ndividually or combinations with metolachlor and trifluralin. In a screening study carried out in soils from four agrochemical dealer sites, rapid mineralization of atrazine occurred in three out of eight soils tested, with the greatest amount occurring i n Bravo rhizosphere soil (35% of the applied atrazine after 9 weeks). Suppression of atrazine mineralization in the Bravo rhizosphere soil did not occur with the addition of high concentrations of herbicide mixtures, but instead was increased. Plants had a positive impact on dissipation of aged Studies were conducted in the laboratory to determine the fate of atrazine in pesticide-contaminated soils from agrochemical dealer sites. No significant differences in atrazine concentrations occurred in soils treated with atrazine i ndividually or combinations with metolachlor and trifluralin. In a screening study carried out in soils from four agrochemical dealer sites, rapid mineralization of atrazine occurred in three out of eight soils tested, with the greatest amount occurring i n Bravo rhizosphere soil (35% of the applied atrazine after 9 weeks). Suppression of atrazine mineralization in the Bravo rhizosphere soil did not occur with the addition of high concentrations of herbicide mixtures, but instead was increased. Plants had a positive impact on dissipation of aged atrazine in soil, with significantly less atrazine extractable from Kochia-vegetated soils than from nonvegetated soils. 11. Bacterial inoculants of forage grasses that enhance degradation of 2-chlorobenzoic acid in soil. Siciliano, S. D. and Germida, J. J. Environ toxicol chem. 16: 6 pp. 1098-1104. (June 1997). NAL Call #: QH545.A1E58 Descriptors: polluted-soils bioremediationAbstract: Biological remediation of contaminated soil is an effective method of reducing risk to human and ecosystem health. Bacteria and plants might be used to enhance remediation of soil pollutants in situ. This study assessed the potential of bacteria (12 isolates), plants (16 forage grasses), and plant-bacteria associations (selected pairings) to remediate 2-chlorobenzoic acid (2CBA)-contaminated soil. Initially, grass viability was assessed in 2CBA-contaminated soil. Soil was contaminated wi th 2CBA, forage grasses were grown under growth chamber conditions for 42 or 60 d, and the 2CBA concentration in soil was determined by gas chromatography. Only five of 16 forage grasses grew in 2CBA-treated (816 mg/kg) soil. Growth of Bromus inermis had no effect on 2CBA concentration, whereas Agropyron intermedium, B. biebersteinii, A. riparum, and Elymus dauricus decreased 2CBA relative to nonplanted control soil by 32 to 42%. The 12 bacteria isolates were screened for their ability to promote the germ ination of the five grasses in 2CBA-contaminated soil. Inoculation of A. riparum with Pseudomonas aeruginos

Phytoremediation : 植物による環境/土壌浄化

Disinfection by-products in drinking water: Occurrence, toxicity and abatement.

Heavy metals (HMs) and radionuclides are released through geological and anthropogenic activities and enter the environment through wastewater, soil and sediment. Large amounts of Pb (>1000 ppm), Zn (>4000 ppm) and Cd (40-400 ppm) have recently been reported in soils near Picher, USA that are harmful to the living organism. These inorganic pollutants cannot be degraded and cause damage to vital human organs and ecosystems. Different industrial and municipal solid waste was a major source of HMs in soil, including airborne aerosols. In the same manner, nuclear waste and radioactive materials used (e.g., medical facilities) or released in different processes contribute to the environmental pollution of radionuclides. The release of such toxic ions from different sources leads to mutagenesis, carcinogenesis and serious risks to the living organisms. As a result, proper management of waste from these sources, as well as environmentally friendly remediation methods, is warranted. However, recent studies have shown that it is more difficult to remove HMs and radionuclides from the source, but they can be effectively neutralized or converted into a less toxic metabolites. The combination of a unique plant-microbe system plays a key role in the remediation process. However, new bioremediation methods are now being used to eliminate HMs and radionuclides. Microbes are capable of bio-transforming, bio-sorbent and biomineralizing HMs and radionuclides through their inherent catabolic process. Enhancing phytoremediation using different strategies for the remediation of HMs and radionucleotides is necessary to ensure that the land resource is safe, fertile and productive for sustainable use.

Understanding the holistic approach to plant-microbe remediation technologies for removing heavy metals and radionuclides from soil

This study aimed to examine the concentrations and environmental health risk of the potentially toxic metals including Pb, Zn, Cu, Cd, Cr, and As in street dusts and surface soils of Ahvaz, the capital of Khuzestan province, located in the southwest of Iran. To this end, a total of 81 street dusts and 96 surface soils were collected from Ahvaz urban areas. Toxic metals were measured by inductively coupled plasma-mass spectrometry and evaluated using enrichment factors, potential ecological risk index and human health risk assessment. Lead in street dusts and Pb and Cu in surface soil showed the highest enrichment factor. The results revealed that there are two major sources of toxic metals in Ahvaz, including industrial activities and road traffic emissions and also resuspension of soil and dust particles. Cu, Pb, Zn, and Cr in Ahvaz soil and dust particles are strongly influenced by anthropogenic activity, mainly industrial and traffic emissions, while As and Co originate from resuspension of soil natural parent particles. The potential ecological risk index (RI) values for dust samples indicated that 58.02% of all samples showed low potential ecological risk. Moreover, 33% and 9% of samples showed moderate and considerable ecological risk, respectively. In addition, the RI values for soil samples indicated that 57% and 40% of all samples had low and moderate ecological risk, respectively, and 3% had a high ecological risk. The hazard index (HI) values of studied potentially toxic metals showed that there is no non-carcinogenic risk for children and adults. Furthermore, the HI value for children was 2–7 times upper than those for adults, which confirm that children show more potential health risks for exposition to these potential toxic metals. Cancer risks of the studied potential toxic elements for both adults and children decreased in the following order Crdust > Crsoil > Cddust > Cdsoil > Asdust > Assoil > Pbdust > Pbsoil. The carcinogenic risk values of Cd, As, and Pb for adults and children was lower than 1 × 10−6, suggesting carcinogenic risk of potentially toxic metals in the street dust and surface soil could be neglected. On the other hand, the carcinogenic risk value of Cr was greater than 1 × 10−6 for both adults and children revealing that the carcinogenic risks of Cr essentially need more consideration for environmental management control.

Ecological and human health risk assessment of toxic metals in street dusts and surface soils in Ahvaz, Iran.

Distribution, contents and health risk assessment of metal(loid)s in small-scale farms in the Ecuadorian Amazon: An insight into impacts of oil activities.

https://cyberleninka.org/article/n/653827.pdf

Localization of polycyclic aromatic hydrocarbons and heavy metals in surface soil of Asia’s oldest oil and gas drilling site in Assam, north-east India: Implications for the bio-economy

The increasing trends of metals in the environment creates a significant concern. These metals are infiltrated in various environmental media and destroy the quality of the soil. The contaminated soil remains unproductive and needs to be improved to allow for the growth of crops. Recent research has identified that some rhizobacteria possess metal-resistant genes, which enhance crop productivity and plant resistance under heavy metal stress. Many strains of rhizobacteria, upon inoculation, have shown the ability to protect their host plants from heavy metal toxicity. This ability covers different strains of Alphaproteobacteria (e.g., the genera Mesorhizobium, rhizobium, Sinorhizobium, Bradyrhizobium), Betaproteobacteria (e.g., Achromobacter), γ-proteobacteria (e.g., Azotobacter, and Pseudomonas) to Firmicutes (e.g., Bacillus sp.). Although rhizobacteria have the potential to remove metals and metalloids from the soil, some rhizobacteria are at times unpredictable. However, genetically engineered (GE) rhizobacteria finally gives some perspectives for research-based remediation of various heavy metal pollutants. Many bacteria have been genetically manipulated and applied, which are well adapted to help metal bioremediation process. However, many challenges are to be addressed concerning the release of GE bacteria in field conditions. There are possible risks associated with the use of GE bacteria in field conditions, with particular emphasis on ways in which molecular genetics could contribute to risk mitigation. The symbiotic relationship between bacteria and plants has been exploited for in situ bioremediation of a wide range of organic pollutants. However, few reports have attempted to concentrate on the heavy metal remediation using such a symbiotic relationship.

Metabolic Engineering of Rhizobacteria Associated With Plants for Remediation of Toxic Metals and Metalloids

Disinfection by-products (DBPs) are posing a threat to both human and animal health since the last few decades. DBPs are produced when natural organic matter and other anthropogenic substances present in water react with disinfecting chemicals used for treating water. Disinfecting compounds belong to the heterogeneous group, most commonly chlorine, chloramines, and ozone. Human epidemiological studies revealed that DBPs are emerging contaminants of concern (ECCs) responsible for both short-term and long-term adverse health consequences. Over 600 DBPs have been reported from diverse water environment, and out of which very few of them were regulated and correlated with possible health risk. The cytotoxic and genotoxic effects of the unregulated DBPs are still unclear or very little known. The detection, deactivation, or removal of these emerging DBPs in the water environment is the biggest challenge. In this chapter, an attempt has been made to discuss new generation water micropollutants—DBPs, their detection, and remediation through novel biofiltration techniques. The chapter discusses the approaches that were taken in transforming the conventional disinfecting methods to modern advanced techniques to mitigate the problem

Emerging disinfection by-products in water: novel biofiltration techniques

Metagenomics Approach for Selection of Biosurfactant Producing Bacteria from Oil Contaminated Soil

The aim of this study was to ascertain whether nitrate reductase (NR) and alkaline phosphatase activity (ALP) can be used as biochemical marker to screen lemon grass [Cymbopogon flexuosus (Steud) Wats] genotypes for higher herbage yield. In the study, 11 strains of essential oil bearing cash crop lemongrass were used. The results revealed that in vivo NR activity has significant positive correlation with herbage yield; however, no significant correlation was found for ALP. Thus, NR activity can be used as biochemical marker for screening lemon grass genotypes for growth and herbage yield.

/pdf/nitrate-reductase-a-biochemical-marker-for-screening-4dbotirsch.pdf

Hemen Sarma

Papers

Localization of polycyclic aromatic hydrocarbons and heavy metals in surface soil of Asia’s oldest oil and gas drilling site in Assam, north-east India: Implications for the bio-economy

Metabolic Engineering of Rhizobacteria Associated With Plants for Remediation of Toxic Metals and Metalloids

Emerging disinfection by-products in water: novel biofiltration techniques

Metagenomics Approach for Selection of Biosurfactant Producing Bacteria from Oil Contaminated Soil

Nitrate reductase: A biochemical marker for screening superior strain of lemongrass [ Cymbopogon flexuosus (Steud) Wats]