/pdf/the-mobility-and-degradation-of-pesticides-in-soils-and-the-525y80aetr.pdf

The mobility and degradation of pesticides in soils and the pollution of groundwater resources

Bioremediation approaches for organic pollutants: a critical perspective

https://www.cell.com/trends/biotechnology/pdf/S0167-7799(05)00023-5.pdf

Accessing microbial diversity for bioremediation and environmental restoration

The sorption behavior of hydrophobic organic compounds (HOCs) in the environment has been the focus of numerous studies. In most of them, the role of aliphatic domains in sorption has been ignored, even although aliphatic components make up a significant portion of the soil organic matter (SOM). The objective of this review is to elucidate the role of the molecular descriptors − aromaticity and aliphaticity − of natural and engineered sorbents as sorption domains for HOCs in the environment. The data, collected from a large and diverse literature data set, show that phenanthrene, like other HOCs, has a strong affinity for aliphatic SOM domains. In many cases, sorption coefficients are higher than those with aromatic-rich sorbents. No significant correlations between either aromaticity or aliphaticity and sorption affinity were recorded for such a large and diverse data set. On the basis of the data set from our literature review of natural and engineered sorbents, we conclude that (i) aliphatic structures...

/pdf/relative-role-of-aliphatic-and-aromatic-moieties-as-sorption-163mr7hw3j.pdf

Relative role of aliphatic and aromatic moieties as sorption domains for organic compounds: a review.

Kinetics of microbial sulfate reduction in estuarine sediments

Bioavailability of pesticides sorbed to soils is an important determinant of their environmental fate and impact. Mineralization of sorbed atrazine was studied in soil and clay slurries, and a desorption-biodegradation-mineralization (DBM) model was developed to quantitatively evaluate the bioavailability of sorbed atrazine. Three atrazine-degrading bacteria that utilized atrazine as a sole N source (Pseudomonas sp. strain ADP, Agrobacterium radiobacter strain J14a, and Ralstonia sp. strain M91-3) were used in the bioavailability assays. Assays involved establishing sorption equilibrium in sterile soil slurries, inoculating the system with organisms, and measuring the CO(2) production over time. Sorption and desorption isotherm analyses were performed to evaluate distribution coefficients and desorption parameters, which consisted of three desorption site fractions and desorption rate coefficients. Atrazine sorption isotherms were linear for mineral and organic soils but displayed some nonlinearity for K-saturated montmorillonite. The desorption profiles were well described by the three-site desorption model. In many instances, the mineralization of atrazine was accurately predicted by the DBM model, which accounts for the extents and rates of sorption/desorption processes and assumes biodegradation of liquid-phase, but not sorbed, atrazine. However, for the Houghton muck soil, which manifested the highest sorbed atrazine concentrations, enhanced mineralization rates, i.e., greater than those expected on the basis of aqueous-phase atrazine concentration, were observed. Even the assumption of instantaneous desorption could not account for the elevated rates. A plausible explanation for enhanced bioavailability is that bacteria access the localized regions where atrazine is sorbed and that the concentrations found support higher mineralization rates than predicted on the basis of aqueous-phase concentrations. Characteristics of high sorbed-phase concentration, chemotaxis, and attachment of cells to soil particles seem to contribute to the bioavailability of soil-sorbed atrazine.

Assessment of Bioavailability of Soil-Sorbed Atrazine

Limited bioavailability of organic pollutants in soil may be a detriment to the successful application of bioremediation. The availability of soil-sorbed biphenyl to two biphenyl-degrading bacteria, Pseudomonas putida P106 and Rhodococcus erythropolis NY05, was assessed using a kinetic mineralization assay. Biphenyl was aged in four soils of different organic carbon (OC) contents (0.4−7.8%) for up to 274 days. With a biphenyl-soil contact time of 24 h, the initial mineralization rates (IMRs) ranged from 2.6 to 3.5 μg·L-1·min-1 for strain P106 and from 3.8 to 0.92 μg·L-1·min-1 for strain NY05. These IMRs were higher than those of soil-free controls and those predicted by a coupled desorption/biodegradation model, suggesting both strains of bacteria could access soil-sorbed biphenyl. For strain P106, biphenyl mineralization curves in slurries of four different soils were nearly coincident with those in soil-free systems containing the same total mass of biphenyl. This strain appeared to have immediate and c...

Bioavailability of soil-sorbed biphenyl to bacteria

The degradation of naphthalene was studied in soil-slurry systems, and a quantitative model was developed to evaluate the bioavailability of sorbed-phase contaminant. Four soils with different organic matter contents were used as sorbents. Two naphthalene-degrading organisms, Pseudomonas putida G7 and NCIB 9816-4, were also selected. Sorption isotherms and single and series dilution desorption studies were conducted to evaluate distribution coefficients, desorption parameters, and the amount of non-desorbable naphthalene. Biodegradation kinetics were measured in soil extract solutions and rate parameters estimated. Bioavailability assays involved establishing sorption equilibrium, inoculating the systems with organisms, and measuring naphthalene concentrations in both sorbed and dissolved phases over time. For all four soils, the sorption isotherms were linear, and desorption could be described by a model involving three types of sites: equilibrium, nonequilibrium, and non-desorption. Enhanced bioavailability, as evidenced by faster than expected degradation rates based on liquid-phase concentrations, were observed in soils with the higher sorption distribution coefficients. These observations could be described using model formulations that included solid-phase degradation. In all soils studied, degradation of non-desorbable naphthalene was observed.

Biodegradation of non-desorbable naphthalene in soils.

Field studies have demonstrated that prolonged pesticide-soil contact times (aging) may lead to unexpected persistence of these compounds in the environment. Although this phenomenon is well documented in the field, there have been very few controlled laboratory studies that have tested the effects of long-term aging and the role of differing sorbates on contaminant sorption-desorption behavior and fate in soils. This study examines the sorption-desorption behavior of chlorobenzene, ethylene dibromide (1,2-dibromomethane), atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), and 2, 4-D (2,4-dichlorophenoxyacetic acid) on one soil type after 1 d, 30 d, and 14 mo of aging. Sorption isotherms were evaluated after each aging period to observe changes in the uptake of each compound by soil. Desorption kinetic data were generated after each aging period to observe changes in release from soil, and desorption parameters were evaluated using a three-site desorption model that includes equilibrium, nonequilibrium, and nondesorption sites. The data indicate no statistically significant increase in sorption for ethylene dibromide or chlorobenzene from 1 to 30 d, although sorption of 2,4-D increased slightly, and sorption of atrazine decreased slightly. Statistically significant increases in linear sorption coefficients (Kd), from 1 d to 14 mo of aging, were apparent for ethylene dibromide and 2,4-D. The Kd values for chlorobenzene, measured after 1 d, 30 d, and 14 mo of aging, were statistically indistinguishable. Aging affected the distribution of chemicals within sorption sites. With aging, the desorbable fraction decreased and the nondesorbable fraction, which was apparent after only 1 d of pesticide-soil contact, increased for all chemicals studied.

Jeong Hun Park

Papers

Assessment of Bioavailability of Soil-Sorbed Atrazine

Bioavailability of soil-sorbed biphenyl to bacteria

Biodegradation of non-desorbable naphthalene in soils.

Aging Effects on the Sorption–Desorption Characteristics of Anthropogenic Organic Compounds in Soil

Sorbed atrazine shifts into non-desorbable sites of soil organic matter during aging.