Synergy of the Tropical Earthworm Pontoscolex corethrurus and Oil Palm Bagasse in the Removal of Heavy Crude Oil.

The tropical endogeic earthworm Pontoscolex corethrurus, a non-standard species used in ecotoxicity, has been found in crude oil-contaminated habitats. We estimated the removal of total hydrocarbons from heavy crude "Maya" oil on an artificially contaminated soil with a median lethal concentration of P. corethrurus and an addition of oil palm bagasse. P. corethrurus had a high survival rate, and the addition of oil palm bagasse led to a greater growth and an increase in abundance of bacteria and fungi. The activity of P. corethrurus and the nutritional quality of oil palm bagasse had a significant impact on the removal of a larger amount of petroleum hydrocarbons from contaminated soil. We concluded that the endogeic earthworm P. corethrurus and oil palm bagasse acted synergistically to achieve a more effective removal of total petroleum hydrocarbons from soil. These results show the potential for using P. corethrurus to remove, either directly or indirectly, crude oil from soil.

Evaluation of in situ biosurfactant production by inoculum of P. putida and nutrient addition for the removal of polycyclic aromatic hydrocarbons from aged oil-polluted soil.

This work aimed to conduct a laboratory study to evaluate the use of Pseudomonas putida CB-100 and nutrient addition for the removal of PAHs from an aged oil-polluted soil of Veracruz, Mexico. Pseudomonas putida is a biosurfactant-producing bacterium capable of metabolizing polycyclic aromatic hydrocarbons (PAHs), which are toxic compounds with low water solubility, high melting, and boiling points, and low vapor pressure; characteristics that increase as their molecular weight increases and make them more recalcitrant. The methodology consisted in sampling the long-term oil-polluted soil and testing the use of Gamma irradiation (25 kGy) for the sterilization of the soil for abiotic control. We evaluated serological bottles containing 20 g of 35% moist soil (irradiated and non-irradiated) with the following treatments: the addition of nutrients (NH4Cl, NaNO3, KH2PO4, and K2HPO4), an inoculum of P. putida, and both P. putida and nutrients. The parameters assessed were pH, organic matter, humidity, available phosphorus, total nitrogen, cultivable heterotrophic microorganisms, CO2 production, rhamnolipids, surface tension, and the removal of eleven PAHs. The non-irradiated soil added with P. putida was the most efficient in the removal of PAHs; the pattern was: Benzo(a)anthracene > Phenanthrene > Fluoranthene > Benzo(k)fluoranthene > Chrysene > Pyrene > Anthracene > Acenaphthylene > Benzo(b)fluoranthene. In conclusion, P. putida in the non-irradiated soil produced in situ biosurfactants (1.55 mg/kg of rhamnolipids and an 11.9 mN/m decrease in surface tension) and removed PAHs in 10 days.

Phytotoxicity and upper localization of Ag@CoFe2O4 nanoparticles in wheat plants.

Environmental concern related to Ag+ release from conventional AgNPs is expected to be prevented once contained into a magnetic core like magnetite or CoFe2O4. Accordingly, we obtained CoFe2O4 NPs by microwave-assisted synthesis, which AgNO3 addition rendered Ag@CoFe2O4 NPs. NPs were characterized, and before exploring potential applications, we carried out 7-day wheat toxicity assays. Seed germination and seedling growth were used as toxicity endpoints and photosynthetic pigments and antioxidant enzymes as oxidative stress biomarkers. Total Fe, Co, and Ag determination was initial indicative of Ag@CoFe2O4 NPs uptake by plants. Then NPs localization in seedling tissues was sought by scanning electron microscopy (SEM) and darkfield hyperspectral imaging (DF-HSI). Not any silver ion (Ag+) was detected into the ferrite structure, but results only confirmed the presence of metallic silver (Ag0) adsorbed on the CoFe2O4 NPs surface. Agglomerates of Ag@CoFe2O4 NPs (~10 nm) were fivefold smaller than CoFe2O4 NPs, and ferrimagnetic properties of the CoFe2O4 NPs were conserved after the formation of the Ag@CoFe2O4 composite NPs. Seed germination was not affected by NPs, but root and shoot lengths of seedlings diminished 50% at 54.89 mg/kg and 168.18 mg/kg NPs, respectively. Nonetheless, hormesis was observed in roots of plants exposed to lower Ag@CoFe2O4 NPs treatments. Photosynthetic pigments and the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), guaiacol peroxidase (GPX), and ascorbate peroxidase (APX) indicated oxidative damage by reactive oxygen species (ROS) generation. SEM suggested NPs presence in shoots and roots, whereas DF-HSI confirmed some Ag@CoFe2O4 NPs contained in shoots of wheat plants.

DNA damage in earthworms by exposure of Persistent Organic Pollutants in low basin of Coatzacoalcos River, Mexico.

Persistent Organic Pollutants (POPs) are stable organic chemicals that represent a potential risk for ecosystems due to their high toxicity, persistence and biomagnification through food chains. Bioindicators in ecosystems have emerged to assess the effect of environmental pollutants. Earthworms are some of the most common bioindicator organisms in terrestrial ecosystems. The main objective of this study was to evaluate the geontoxicity of POP exposure in wild earthworms captured at different levels of urbanization throughout the lower basin of the Coatzacoalcos River (industrial, urban and rural areas). POP soil and earthworm tissue concentrations were measured via Gas-Mass Chromatography, and earthworm DNA damage was evaluated through the comet assay. The greatest concentrations of ΣPOPs, DDT and HCH were found in soil from industrial sites, followed by urban and rural areas (504.68, 383.10, 298.16; 22.6, 4.6, 2.6 and 433.7, 364, 255.6 mg/kg, respectively). Unlike other pollutants, mean ΣPCBs values were highest for industrial soil samples, followed by those from rural and urban areas (41.10, 33.97 and 12.44 mg/kg respectively). For all earthworm tissue POP analyses, the highest concentrations were found in individuals from industrial sites, followed by the urban and rural areas. Furthermore, the highest levels of DNA damage were registered in the industrial area, followed by the urban and rural areas. These assays suggest a strong links among regional soil contamination, POPs bioavailability and the potential risk of detrimental health effects for organisms that inhabit surface soil (soil life). Earthworms contribute vital ecosystem services that could be affected by these results. This work provides evidence of the potential ecological risk that exists in the Lower Basin of the Coatzacoalcos River.

Sensitivity of the Endogeic Tropical Earthworm Pontoscolex corethrurus to the Presence of Heavy Crude Oil.

Contamination of soil with petroleum is common in oil-producing areas across the tropical regions of the world. There is limited knowledge on the sensitivity of endogeic tropical earthworms to the contamination of soil with total petroleum hydrocarbons (TPH) present in crude oil. Pontoscolex corethrurus is a dominant species in tropical agroecosystems around oil-processing facilities. The sensitivity of P. corethrurus to soil artificially contaminated with "Maya" Mexican heavy crude oil was investigated through avoidance and acute ecotoxicity tests, using the following measured concentrations: 0 (reference soil), 551, 969, 4845, 9991 and 14,869 mg/kg. The avoidance test showed that P. corethrurus displayed a significant avoidance behavior to heavy crude oil at a concentration of 9991 mg/kg or higher. In contrast, acute toxicity tests indicate that the median lethal concentration (LC50) was 3067.32 mg/kg; however, growth (weight loss) was more sensitive than mortality. Our study revealed that P. corethrurus is sensitive to TPH, thus highlighting the importance of P. corethrurus for petroleum ecotoxicological tests.