Removal of carotene-like colored compounds by liquid-liquid extraction during polycyclic aromatic hydrocarbons analysis of plant tissue

Biodegradation of polycyclic aromatic hydrocarbons by Sphingomonas sp. enhanced by water-extractable organic matter from manure compost

The effectiveness of in-situ bioremediation of polycyclic aromatic hydrocarbons (PAHs) may be inhibited by their low aqueous solubility and strong absorption to soil constituents. The aim of this research was to evaluate the effect of water-extractable organic matter (WEOM) from manure compost on the biodegradation of various PAHs. The aqueous solubilities of PAHs including phenanthrene, pyrene and benzo[a]pyrene under different concentrations of WEOM from cow manure compost were initially evaluated. The contribution of WEOM on the degradation of PAHs by Sphingomonas sp. was then investigated. Dissolution results confirmed the ability of WEOM to increase the apparent solubility of the 3PAHs. Time course of biodegradation also revealed its positive contribution to their removal. For example, the degradation of pyrene was 118% higher in the presence of 1000 mg-C L(-1) WEOM as compared to the mineral salt medium (MSM) alone after 48 h incubation. In addition, degradation was 12% higher with WEOM than with Glucose-Ammonium nitrate despite the more than 6 times higher cell concentration in the latter. WEOM from other manure composts such as chicken and pig were found to have the same effect. Finally, additional tests confirmed that high molecular weight WEOM (>1000 Da) contributed mainly to solubility and biodegradation enhancements. On the basis of these results, the increase in apparent solubility of PAHs in WEOM solutions may have a significant impact on their biodegradation. It is postulated that the application of WEOM-rich manure composts may be extended in the in-situ bioremediation of PAHs-polluted soil.

Equilibrium partitioning behavior of naphthalene and phenanthrene with axenic microplantlets of the temperate green seaweed Acrosiphonia coalita

The partitioning behavior of the polycyclic aromatic hydrocarbon (PAH) compounds naphthalene and phenanthrene with the temperate green seaweed Acrosiphonia coalita was characterized. The uptake and partitioning experiments were designed to prevent PAH volatilization, and the PAH concentration was measured in both the seawater liquid medium and in the algal biomass. Axenic microplantlets of A. coalita were used in all experiments to eliminate the possibility of microbial PAH biotransformation. Gas chromatography/mass spectrometry analysis did not reveal any putative metabolites of phenanthrene oxidative biotransformation in either the seawater medium or the algal biomass, but did show that dissolved organic matter from algal biomass constituents were in the liquid medium. The algal biomass grew by 30% over the 114h duration of the partitioning experiments, suggesting PAH compounds did not harm the organism. Both living and heat-killed microplantlets partitioned PAH compounds into the biomass. Naphthalene and phenanthrene reversibly partitioned into the lipid fraction of the algal biomass with equilibrium partitioning constants of 0.130+/-0.007 and 1.58+/-0.03Lg(-1) dry cell mass, respectively, which scaled proportionally to their octanol-water partitioning constants. The PAH material balance for the partitioning process closed between 86% and 100% for naphthalene adsorption and phenanthrene desorption, but closed at 52% for phenanthrene adsorption. To account for the loss, it was proposed that phenanthrene interacted with dissolved organic matter released by the living algal biomass. This study has provided fundamental information needed to assess how seaweeds can play a role in the bioaccumulation and bioremediation of PAH compounds in the marine environment.

Influence of compost amendment on pyrene availability from artificially spiked soil to two subspecies of Cucurbita pepo

The dissolved organic matter (DOM) fraction of soil organic matter (SOM) may positively contribute to polycyclic aromatic hydrocarbons (PAHs) bioavailability. This work investigated the effects of DOM-rich and PAHs-free compost amendment on the plant uptake of pyrene. Two subspecies of Cucurbita pepo (ssp. pepo cv. Raven and ssp. texana cv. Sunray) were grown for three weeks in a spiked soil containing 83.9 mg kg(-1) pyrene under four different treatments; inorganic fertilizer (IF) alone, 15% (v/v) mixed gardening compost with IF (MX15%+IF), MX30% alone, and no fertilization (NF). Equilibrium pyrene desorptions from a spiked soil (104 mg kg(-1)) under different concentrations (35-590 mg-C L(-1)) of DOM extracts derived from two types of composts including MX and cow manure were also conducted. After harvest, the decrease in the pyrene concentration of the soil ranged from 46-65% for the different treatments. The total dry biomass for both plants was highest under MX15%+IF. The bioconcentration factors of pyrene for both also tended to decrease with increasing MX dose from 15% to 30%. However, the total uptakes of pyrene with IF and MX15%+IF were not statistically different (36.7 and 33.7 microg for Raven, and 5.20 and 7.90 microg for Sunray, respectively). These values were around 100% higher than that with NF (17.4 microg for Raven and 2.0 microg for Sunray). The pyrene desorption data confirmed the ability of DOM to associate with pyrene as indicated by its increase in apparent water solubility. On the basis of these results, MX application at 15% (v/v) does not significantly reduce the phytoextraction of pyrene due to the enhancement of plant growth as well as the possible contribution of DOM fractions to pyrene bioavailability. The application of compost may not pose serious concerns regarding the efficiency of phytoremediation of PAHs-polluted soil.