Contaminated soil phytoremediation by Cyperus laxus Lam. cytochrome p450 EROD-activity induced by hydrocarbons in roots

Costus speciosus (Koen ex. Retz.) Sm.: a suitable plant species for remediation of crude oil and mercury-contaminated soil

The aim of this study was to evaluate the efficiency of Costus speciosus (Koen ex. Retz.) Sm. in the degradation of crude oil and reduction of mercury (Hg) from the contaminated soil in pot experiments in the net house for 180 days. C. speciosus was transplanted in soil containing 19150 mg kg-1 crude oil and 3.2 mg kg-1 Hg. The study includes the evaluation of plant biomass, height, root length, total petroleum hydrocarbon (TPH) degradation, and Hg reduction in soil, TPH, and Hg accumulation in plants grown in fertilized and unfertilized pots, chlorophyll production, and rhizospheric most probable number (MPN) at 60-day interval. The average biomass production and heights of C. speciosus in contaminated treatments were significantly (p < 0.05) lower compared to the unvegetated control. Plants grown in contaminated soil showed relatively reduced root surface area compared to the uncontaminated treatments. TPH degradation in planted fertilized, unplanted, and planted unfertilized pot was 63%, 0.8%, and 38%, respectively. However, compared to unvegetated treatments, TPH degradation was significantly higher (p < 0.05) in vegetated treatments. A comparison of fertilized and unfertilized soils showed that TPH accumulation in plant roots and shoots was relatively higher in fertilized soils. Hg degradation in soil was significantly (p < 0.05) more in planted treatment compared to unplanted treatments. The fertilized soil showed relatively more Hg degradation in soil and its accumulation in roots and shoots of plants in comparison to unfertilized soil. MPN in treatments with plants was significantly greater (p < 0.05) than without plants. The plant's ability to produce biomass, chlorophyll, break down crude oil, reduce Hg levels in soil, and accumulate TPH and Hg in roots and shoots of the plant all point to the possibility of using this plant to remove TPH and Hg from soil.

Enzymatic defense of Cyperus brevifolius in hydrocarbons stress environment and changes in soil properties

Hydrocarbons or crude oil contamination of soil is still a burning problem around the globe. The herbs competent that are to survive in hydrocarbons contaminated habitats have some adaptive advantages to cope up with the adverse situations prevailing in that environment. In the present study, the adaptive response of Cyperus brevifolius in the heavily polluted soil with crude oil has been investigated in terms of survivability, changes in productivity, antioxidants, phytochemicals and functional group pro files of the plant species. Besides, changes in enzymes, beneficial bacterial population and physico-chemical conditions of contaminated soil were also studied during 60 days of experimental trials. The results showed significant enhancement in activities of soil dehydrogenase, urease, alkaline phosphatase, catalase, and amylase whereas reduction in cellulase, polyphenol oxidase and peroxidase activities. There was a significant increase in nitrogen fixing, phosphate and potassium solubilizing bacterial population, improvement in physico-chemical conditions and a decrease in total oil and grease (TOG) levels. Besides there was significant variations in the productivity parameters and antioxidant profiles of Cyperus brevifolius in hydrocarbons stress condition suggesting enzymatic defense of the herb. The fourier-transform infrared (FT-IR) analysis indicated uptake and metabolism of some hydrocarbon components by the experimental plant from the hydrocarbons polluted soil.

Hormesis under oil-induced stress in Leersia hexandra Sw. used as phytoremediator in clay soils of the Mexican humid tropic

The oil industry has inherent risks of spills or leaks due to natural or anthropogenic causes, which cause alterations in the soil and damage to the plant. An experiment was carried to investigate the effect of oil on the growth, biomass production, biosynthesis of crude protein of Leersia hexandra grass and the remove of oil from the soil. The results showed different responses by L. hexandra depending on the age, low concentrations of oil induced a significant increase in stolon length, in relative growth rate, in dry matter production and in the biosynthesis of crude protein. The same parameters decreased at high concentrations of oil. However, at the end of the evaluation period of 180 days, high concentrations of oil induced a significant increase in the number of young plants and secondary roots, the terminal third of the main root and root dry matter. The dose response curves had the shape of an inverted U, showing that at days 15, 45, 90 and 180, in stolon length, aerial dry matter production, crude protein (day 90) and young plants (days 45 and 90) exhibited a typical biphasic response. The increase in oil concentration correlated with increases in young plants, number of secondary roots, number of roots at the middle, terminal third and root dry matter. After 180 days exposure the rhizosphere of L. hexandra a total oil removal of oil of 76.7 ± 4 was achieved; 61.7, 51, 44.6, 38 and 52% in soils that initially contained 7.9, 54, 102, 126, 145 and 238 g oil.

Effects of basal fertilizer and perlite amendment on growth of zinnia and its remediation capacity in oil-contaminated soils

In a previous study we demonstrated that Zinnia hybrida 'Profusion White' can be effective in the remediation of oil-contaminated soil. However, the rates of removal of total petroleum hydrocarbons (TPH) were greatest in soils containing 9000 mg/kg TPH and less in soils with higher concentrations of TPH. This study was conducted to investigate the effects of basal fertilizer rates and perlite amendments on the growth of zinnia and its remediation capacity in soils with TPH concentrations of 26,000 mg/kg.

METHODOLOGY

Soils were prepared with or without TPH at an initial concentration of 26,194 mg/kg, and then each of these soils was amended with either a basal fertilizer rate with or without 20% perlite, or twice the basal fertilizer rate with or without 20% perlite. Pots were prepared with the following treatments in these soils: contaminated soil planted with zinnia (planted-contaminated), uncontaminated soil planted with zinnia (planted-uncontaminated), and contaminated soil not planted with zinnia (unplanted-contaminated). Plant growth, soil dehydrogenase activity (DHA), and TPH concentrations were analyzed at 30 and 60 days after sowing.

RESULTS

Plant growth in oil-contaminated and uncontaminated soils was superior in pots with twice the basal fertilizer and with perlite. The DHA values in the planted-uncontaminated treatments were significantly lower than those in the planted-contaminated and unplanted-contaminated treatments. However, the effects of basal fertilizer amount and perlite on the DHA values of the soils were small. The TPH concentrations in the planted-contaminated soils were significantly lower than those in the unplanted-contaminated soils after 30 and 60 days. Furthermore, the TPH concentrations in the planted-contaminated soils were lowest in pots with twice the basal fertilizer and with perlite.

CONCLUSIONS

These results show how phytoremediation of soils with high levels of oil contamination by Z. hybrida 'Profusion White' can be practically enhanced by amending the soil with perlite and higher basal fertilizer rates.

Field note: phytoremediation of petroleum sludge contaminated field using sedge species, Cyperus rotundus (Linn.) and Cyperus brevifolius (Rottb.) Hassk

The aim of this study was to degrade total petroleum hydrocarbon (TPH) in a petroleum sludge contaminated site (initial TPH concentration of 65,000-75,000 mg kg(-1)) with two native sedge species namely Cyperus rotundus (Linn.) and Cyperus brevifolius (Rottb.) Hassk. Fertilized and unfertilized treatments were maintained separately to record the influence of fertilizer in TPH degradation. The average biomass production (twenty plants from each treatment) of C. rotundus was 345.5 g and that of C. brevifolius was 250.6 g in fertilized soil during 360 days. Decrease in soil TPH concentration was higher in fertilized soil (75% for C. rotundus and 64% for C. brevifolius) than in unfertilized soil (36% for C. rotundus and 32% for C. brevifolius). In unvegetated treatments, decrease in soil TPH concentration in fertilized (12%) and unfertilized soil (8%) can be attributed to natural attenuation and microbial degradation. TPH accumulation in roots and shoots was significantly higher in fertilized soil in comparison to unfertilized soils (p < 0.05). Most probable number (MPN) in planted treatments was significantly higher than in unplanted treatments (p < 0.05).

Phytoremediation and removal mechanisms in Bouteloua curtipendula growing in sterile hydrocarbon spiked cultures

Tolerance index and phytoremediation factors of side oats grama (Bouteloua curtipendula) with recalcitrant polycyclic aromatic hydrocarbons (PAH) phenanthrene (PHE), pyrene (PYR), and benzo[a]pyrene (BaP) and the resulting impact on phenotypic response, were evaluated in sterile conditions with whole plant growing in test-tube cultures with MS medium with PAH and compared with Tall fescue (Festuca arundinacea), control for this study. PAH mixture of PHE, PYR and BaP (1:1:1 w/w/w) blended with Maya crude oil (1:1 w/w), final concentration of 1500 mg kg(-1) was used. After 40 days, BaP removal, in the presence of Maya crude was superior compared with PHE and PYR removal Although the presence of PAH negatively affects the phenotypic response of the plants; sterile conditions experiments were helpful to evaluate phytoremediation factors to elucidate some important questions regarding phytoremediation mechanisms; in this study, B. curtipendula was able to phytostabilizate BaP associated to a significant hydrocarbon removal (57.4%) with high root accumulation but attenuated transport to stems, here reported as translocation factor. To our knowledge, this is the first time that quantifiable phytoremediation factors were used to evaluate the tolerance and removal capacity of a native semi-arid climate plant which is probably able to phytoremediate hydrocarbon contaminated soils.