Bioavailability Of Pollutants Research Articles

土壤有机污染物的吸附–生物降解耦合模型研究进展

污染物的微生物可利用性是控制其环境归趋的主要因素之一，也是决定受污染土壤的微生物修复技术成败的关键。有机污染物进入土壤后发生吸附作用，进而影响其生物可利用性。正确预测有机污染物在土壤环境中的微生物可利用性，需要建立可靠的吸附–降解动力学模型。本文介绍了五种国内外常用的有关农药和多环芳烃在土壤/沉积物上的吸附–降解耦合模型，综述了模型建立过程、评价方法、适用范围，探讨了现有模型在实际应用中的共性问题，以期为土壤污染的控制和修复提供思路。 Bioavailability of pollutants in soil is one of the main factors that determine their environmental fate. It is a key to the successful implementation of bioremediation of polluted soil. Sorption of organic pollutants occurs once they enter soil, and subsequently influence the bioavailability of the pollutants. To accurately predict the bioavailability of organic pollutants in soil, coupled sorption-biodegradation models need to be established. This paper introduces five coupled sorption-biodegradation models used in the literature to account for the bioavailability of pesticides and polycyclic aromatic hydrocarbons in soil and sediment as influenced by sorption. The overall objective of this paper is to offer proper ideas for soil pollution control and remediation. This is achieved by summarizing the establishment of these models, their evaluations and applications, and by discussing potential problems associated with these models.

Fraction distribution and migration of heavy metals in mangrove-sediment system under sulphur and phosphorus amendment

ABSTRACT In this study, mangrove seedlings (Kandelia obovata (S. L.)) were cultivated in rhizo-boxes, which contain sediments collected from natural mangrove forest and modified with different rates of sulphate and phosphate. The fraction distributions of Zn, Cd, Cu, Ni and Pb in rhizosphere and non-rhizosphere sediments were studied by using a sequential extraction method. Metal concentrations in plant tissues and iron plaque on root surface were also determined to reveal migration variation of heavy metals in the plant-sediment system. The results showed that the activities of K. obovata roots enhance the reducible metals while reducing acid-extractable and oxidisable metals; sulphur amendment benefits the combination of metal ions with S2– and therefore reduces the bioavailability of metal pollutants; addition of sulphur also improves the content of iron plaque on the root surface, which plays an important role in metal accumulation by K. obovata root tissue; the addition of sulphur markedly reduces the concentration of Cd in roots, but significantly enhanced the concentrations of Cu, Zn, Ni and Pb in roots. The results indicate that sulphur and phosphorus content in mangrove sediment, and the growth of mangrove plant can significantly influence the migration of heavy metals in the mangrove wetland ecosystem.

Natural Organic Amendments for Improved Phytoremediation of Polluted Soils: A Review of Recent Progress

Environmental pollution caused by metals, radionuclides and organic pollutants affects quality of the biosphere: soil, water and air. Currently, great efforts have been made to reduce, remove or stabilize contaminants in polluted sites. There has been increasing interest in phytoremediation—the use of plants to reduce concentration of pollutants or to render them harmless. This paper provides a brief review of recent progress in the research and practical application of phytoremediation techniques. Improvements in phytoremediation due to utilization of organic amendments, namely, agro- and industrial wastes (such as sugar beet residue, composted sewage sludge or molasses), biochar, humic substances, plant extracts and exudates are discussed, as well as their influences on soil structure and characteristics, plants growth and bioavailability of pollutants. Both plant-assisted phytoremediation and the use of natural materials in the absence of remediating plant are believed to be cost-effective and environmentally friendly approaches for soil cleanup. However, the characterization and quantification of a range of natural materials used in phytoremediation are essential in order to implement these approaches to practice.

Sorption of Atrazine, 17α-Estradiol, and Phenanthrene on Wheat Straw and Peanut Shell Biochars

Biochars from two different feedstocks (peanut shell-PB; wheat straw-WB) were used in this study to understand the sorption mechanisms of atrazine (ATR), 17α-ethinyl estradiol (EE2), and phenanthrene (PHEN) to help minimize the bioavailability of the organic pollutants in the environment. Sorption isotherms of ATR, EE2, and PHEN by WB and PB biochars followed the Freundlich model where the sorption parameter (n) shows the trend: ATR > EE2 and PHEN, while the sorption capacity (log K oc ) increases from ATR < EE2 < PHEN and indicate that the most hydrophobic and planar organic pollutant (PHEN) is the most easily adsorbed organic compound on PB and WB. The higher H/C and (O + N)/C ratios of WB (0.099 and 0.525, respectively) suggest its stronger aliphaticity and polarity than PB (0.078 and 0.352, respectively) that induced stronger sorption affinity for ATR and PHEN. Higher specific surface area (m2 g−1) of PB (19.7) may be responsible for the higher sorption capacity for EE2 than WB (8.8) because it can accommodate the large molecule of EE2. Results from this study may be helpful to predict the bioavailability of organic pollutants when soils contaminated with pollutants are remediated with biochars produced from wheat straw and peanut shells.

Redox processes in water remediation

Groundwater is the main source of drinking water and water for agricultural and industrial usage. Therefore, groundwater contamination is prevented and contaminated groundwater is remediated to protect public health and the environment. Methods to remediate groundwater contamination have been recently developed. The use of redox processes in water remediation technologies has not been properly reviewed. Numerous water remediation technologies, such as ultrasonication, bioremediation, electrokinetics and nanotechnology, are closely related to redox processes. Redox processes control the chemical speciation, bioavailability, toxicity, mobility and adsorption of water pollutants in environment. Here, we review (1) general introduction of redox processes, (2) applicability of redox processes in water remediation, and (3) catalytic enhancement of redox potentials to explore its wide applicability in environmental remediation.

Chemical characteristics of chromophoric dissolved organic matter in stormwater runoff of a typical residential area, Beijing

Stormwater runoff acts as a vital intermediate between wet precipitation, terrestrial, and aquatic ecosystems, in which chromophoric dissolved organic matter (CDOM) plays an important role in influencing the transport, toxicity, bioavailability, and ultimate fate of many pollutants. It is important and necessary to characterize the CDOM in stormwater runoff, which is useful to clarify the relationship between CDOM with the other coexisting organic and/or inorganic components. In this study, 30 stormwater runoff samples were collected from three different stormwater events in a typical residential area in Beijing, and CDOM in the samples was characterized by UV–visible spectroscopy, excitation–emission matrix fluorescence and proton nuclear magnetic resonance (1H NMR) spectroscopy to investigate its compositions, structures, and sources. Being compared to the previous studies on wet precipitation, average molecular weight of CDOM in this study was much larger, implying the presence of more aromatic components with carbonyl, carboxyl, hydroxyl and unsaturated carbon atoms functional groups. Furthermore, both allochthonous and autochthonous sources contributed to the local CDOM, and their chemical properties were influenced by anthropogenic and biogenic factors. Thus, the CDOM in stormwater runoff is a compositionally different matrix than that discovered in wet precipitation.

Assessment of the bioavailability and phytotoxicity of sediment spiked with polycyclic aromatic hydrocarbons.

Large amounts of sediment are dredged globally every year. This sediment is often contaminated with low concentrations of metals, polycyclic aromatic hydrocarbons, pesticides and other organic pollutants. Some of this sediment is disposed of on land, creating a need for risk assessment of the sediment disposal method, to minimize the degradation of environmental quality and prevent risks to human health. Evaluating the available fractions of certain polycyclic aromatic hydrocarbons is very important, as in the presence of various organisms, they are believed to be easily subject to the processes of bioaccumulation, biosorption and transformation. In order to determine the applicability of applying these methods for the evaluation of pollutant bioavailability in sediments, the desorption kinetics from the sediment of various polycyclic aromatic hydrocarbons in the presence of Tenax and XAD4 were examined over the course of 216 h. Changes in the PAH concentrations in dredged sediments using five different seed plants during a short time of period (10 days) were also followed. Using chemical extraction techniques with Tenax and XAD4, a time of around 24 h is enough to achieve equilibrium for all four PAHs. Results showed good agreement between the seed accumulation and PAH extraction methods with both agents. If we compare the two extraction techniques, XAD4 gave better results for phenanthrene, pyrene and benzo(a)pyrene, and Tenax gave better results for chrysene.

Editorial: Environmental phytoremediation: plants and microorganisms at work.

Editorial: Environmental phytoremediation: plants and microorganisms at work.

Microscopic biomineralization processes and Zn bioavailability: a synchrotron-based investigation of Pistacia lentiscus L. roots.

Plants growing on polluted soils need to control the bioavailability of pollutants to reduce their toxicity. This study aims to reveal processes occurring at the soil-root interface of Pistacia lentiscus L. growing on the highly Zn-contaminated tailings of Campo Pisano mine (SW Sardinia, Italy), in order to shed light on possible mechanisms allowing for plant adaptation. The study combines conventional X-ray diffraction (XRD) and scanning electron microscopy (SEM) with advanced synchrotron-based techniques, micro-X-ray fluorescence mapping (μ-XRF) and X-ray absorption spectroscopy (XAS). Data analysis elucidates a mechanism used by P. lentiscus L. as response to high Zn concentration in soil. In particular, P. lentiscus roots take up Al, Si and Zn from the rhizosphere minerals in order to build biomineralizations that are part of survival strategy of the species, leading to formation of a Si-Al biomineralization coating the root epidermis. XAS analysis rules out Zn binding to organic molecules and indicates that Zn coordinates Si atoms stored in root epidermis leading to the precipitation of an amorphous Zn-silicate. These findings represent a step forward in understanding biological mechanisms and the resulting behaviour of minor and trace elements during plant-soil interaction and will have significant implications for development of phytoremediation techniques.

Effect of aging process on adsorption of diethyl phthalate in soils amended with bamboo biochar

Biochar is a carbonaceous sorbent and can be used as a potential material to reduce the bioavailability of organic pollutants in contaminated soils. In the present study, the adsorption and desorption of diethyl phthalate (DEP) onto soils amended with bamboo biochar was investigated with a special focus on the effect of biochar application rates and aging conditions on the adsorption capacity of the soils. Biochar amendment significantly enhanced the soil adsorption of DEP that increased with increasing application rates of biochar. However, the adsorption capacity decreased by two aging processes (alternating wet and dry, and constantly moist). In the soil with low organic carbon (OC) content, the addition of 0.5% biochar (without aging) increased the adsorption by nearly 98 times compared to the control, and exhibited the highest adsorption capacity among all the treatments. In the soil with high OC content, the adsorption capacity in the treatment of 0.5% biochar without aging was 3.5 and 3 times greater than those of the treatments of biochar aged by alternating wet and dry, and constantly moist, respectively. Moreover, constantly moist resulted in a greater adsorption capacity than alternating wet and dry treatments regardless of biochar addition. This study revealed that biochar application enhanced soil sorption of DEP, however, the enhancement of the adsorption capacity was dependent on the soil organic carbon levels, and aging processes of biochar.

Phytotoxicity of Citric Acid and Tween® 80 for Potential Use as Soil Amendments in Enhanced Phytoremediation

Enhanced phytoremediation adding biodegradable amendments like low molecular weight organic acids and surfactants is an interesting area of current research to overcome the limitation that represents low bioavailability of pollutants in soils. However, prior to their use in assisted phytoremediation, it is necessary to test if amendments per se exert any toxic effect to plants and to optimize their application mode. In this context, the present study assessed the effects of citric acid and Tween® 80 (polyethylene glycol sorbitan monooleate) on the development of alfalfa (Medicago sativa) plants, as influenced by their concentration and frequency of application, in order to evaluate the feasibility for their future use in enhanced phytoremediation of multi-contaminated soils. The results showed that citric acid negatively affected plant germination, while it did not have any significant effect on biomass or chlorophyll content. In turn, Tween® 80 did not affect plant germination and showed a trend to increase biomass, as well as it did not have any significant effect on chlorophyll levels. M. sativa appeared to tolerate citric acid and Tween® 80 at the tested concentrations, applied weekly. Consequently, citric acid and Tween® 80 could potentially be utilized to assist phytoremediation of contaminated soils vegetated with M. sativa.

Biosurfactant production from marine hydrocarbon-degrading consortia and pure bacterial strains using crude oil as carbon source.

Biosurfactants (BSs) are “green” amphiphilic molecules produced by microorganisms during biodegradation, increasing the bioavailability of organic pollutants. In this work, the BS production yield of marine hydrocarbon degraders isolated from Elefsina bay in Eastern Mediterranean Sea has been investigated. The drop collapse test was used as a preliminary screening test to confirm BS producing strains or mixed consortia. The community structure of the best consortia based on the drop collapse test was determined by 16S-rDNA pyrotag screening. Subsequently, the effect of incubation time, temperature, substrate and supplementation with inorganic nutrients, on BS production, was examined. Two types of BS – lipid mixtures were extracted from the culture broth; the low molecular weight BS Rhamnolipids and Sophorolipids. Crude extracts were purified by silica gel column chromatography and then identified by thin layer chromatography and Fourier transform infrared spectroscopy. Results indicate that BS production yield remains constant and low while it is independent of the total culture biomass, carbon source, and temperature. A constant BS concentration in a culture broth with continuous degradation of crude oil (CO) implies that the BS producing microbes generate no more than the required amount of BSs that enables biodegradation of the CO. Isolated pure strains were found to have higher specific production yields than the complex microbial marine community-consortia. The heavy oil fraction of CO has emerged as a promising substrate for BS production (by marine BS producers) with fewer impurities in the final product. Furthermore, a particular strain isolated from sediments, Paracoccus marcusii, may be an optimal choice for bioremediation purposes as its biomass remains trapped in the hydrocarbon phase, not suffering from potential dilution effects by sea currents.

Pollutants bioavailability and toxicological risk from microplastics to marine mussels

Microplastics represent a growing environmental concern for the oceans due to their potential of adsorbing chemical pollutants, thus representing a still unexplored source of exposure for aquatic organisms. In this study polyethylene (PE) and polystyrene (PS) microplastics were shown to adsorb pyrene with a time and dose-dependent relationship. Results also indicated a marked capability of contaminated microplastics to transfer this model PAH to exposed mussels Mytilus galloprovincialis; tissue localization of microplastics occurred in haemolymph, gills and especially digestive tissues where a marked accumulation of pyrene was also observed. Cellular effects included alterations of immunological responses, lysosomal compartment, peroxisomal proliferation, antioxidant system, neurotoxic effects, onset of genotoxicity; changes in gene expression profile was also demonstrated through a new DNA microarray platform. The study provided the evidence that microplastics adsorb PAHs, emphasizing an elevated bioavailability of these chemicals after the ingestion, and the toxicological implications due to responsiveness of several molecular and cellular pathways to microplastics.

Biogeochemical processes at soil-root interface

Rhizosphere is a microsite where interactions among roots, microorganisms, soil constituents (minerals and organic matter), and soil solution take place. Biomolecules produced by plants and microorganisms and soil organic substances are involved in many biogeochemical processes at soil-root interface such as: a) weathering of clay minerals and release of Al and Fe, b) formation of nanoprecipitates and organo-mineral complexes, c) sorption/desorption of cations and anions on/from soil colloids and d) bioavailability of nutrients and pollutants. Many exudates form strong complexes with Fe and Al ions, retard or inhibit their hydrolytic reactions and promote the formation of noncrystalline or short-range ordered Al and Fe nanoprecipitates. The so-called iron plaques, present on many wetland plant roots, are Fe(III)-oxyhydroxides (mainly ferrihydrite). These precipitates may interact with biopolymers (proteins, polysaccharides, DNA, RNA and so on), phyllosilicates, soil organic substances as well as microorganisms forming organo-mineral complexes. Root exudates play a vital role on the sorption/desorption of nutrients and pollutants at soil-root interface. The processes, which affect the sorption of cations and anions on sorbents present in the rhizosphere are particularly complex, being sorption of cations quite different from that of anions. Root exudates usually inhibit the sorption of anions, but may promote or inhibit the sorption of cations. They may desorb, at least partially, nutrients and pollutants previously sorbed on soil components, promoting their bioavailability for plants and microorganisms. Finally, some plants release chelating organic ligands able to complex metals (e.g. Al) which become less toxic. Many factors control these processes, for example; pH, nature and concentration of the biomolecules present in the rhizosphere, nature of sorbent and sorbate, reaction time.

ADVANCED OXIDATION PROCESSES FOR FOOD INDUSTRIAL WASTEWATER DECONTAMINATION

High organic matter content is a basic problem in food industry wastewaters. Typically, the amount and composition of the effluent varies considerably. In the article four groups of advanced processes and their combination of food industry wastewater treatment have been reviewed: electrochemical oxidation (EC), Fenton’s process, ozonation of water and photocatalytic processes. All advanced oxidation processes (AOP`s) are characterized by a common chemical feature: the capability of exploiting high reactivity of HO• radicals in driving oxidation processes which are suitable for achieving decolonization and odour reduction, and the complete mineralization or increase of bioavailability of recalcitrant organic pollutants.

Comparative characterisation of two fulvic acids from East Lake and Liangzi Lake in central China

Environmental context Fulvic acids account for a large proportion of dissolved organic matter in aquatic environments and affect the transportation and bioavailability of organic and inorganic pollutants. The structural and spectroscopic characteristics of fulvic acids mainly depend on the sources, seasons and anthropogenic activity. We present an advanced approach using fluorescence spectroscopy as a rapid and cost-effective method to investigate the composition, properties and origins of fulvic acids. Abstract Fulvic acids (FAs) isolated seasonally from the sediments of East Lake and Liangzi Lake in central China were comparatively investigated. The structural features of the FAs were characterised using chemical and spectroscopic methods, including elemental analysis, UV-Vis spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and three-dimensional excitation emission matrix (EEM) fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC). The O/C, (O+N)/C and C/N ratios of FA extracted from Liangzi Lake (FAL) were higher than those of FA extracted from East Lake (FAE), indicating higher oxygen-containing functionality and polarity and less nutrient in FAL compared with FAE. The two FAs had similar UV-Vis spectra with different absorbance intensities. The FT-IR spectra showed that the two FAs had similar functional groups. The total fluorescence intensity and aromaticity of samples from Liangzi Lake were higher than those of East Lake except for those taken in the summer. The two FAs were largely terrestrially derived organic materials. Five fluorescent components, including four humic-like and two fulvic-like components, were identified by PARAFAC modelling of the EEM spectral data. The fluorescence was dominated by two components. The findings suggest that EEM fluorescence spectroscopy together with PARAFAC is a rapid and cost-effective method for understanding the characteristics and origins of FAs in natural water systems.

Assessment of tolerance and efficiency of crop species in the phytoremediation of DDT polluted soils

Soil contamination by organic compounds is of great concern worldwide since it could act as a major environmental repository. The success of phytoremediation is conditioned by two main factors: the availability and toxicity of the compound to be remediated, and the plant species ability to incorporate or degrade the contaminants. This study aimed to assess the potential of different plants species for remediation of aged DDTs residues in soil. Tomato, sunflower, soybean and alfalfa plants were grown in contaminated soils (p,p′-DDE 455.3, p,p′-DDT 63.5ngg−1 dry weight) for 15 and 60 days. Phytoremediation was evaluated by studying the pollutant dynamics in the soil–plant system and lipid peroxidation (LPO) as an effect biomarker. Results showed that soil DDTs levels were diminished after 60 days of plant growth, due to the combined effect of DDTs uptake by roots and rhizospheric degradation. The relative accumulation of each compound was dependent on soil levels (p,p′-DDE>p,p′-DDT>p,p′-DDD) and all species presented root >aerial accumulation pattern, evidencing DDTs translocation. Tomato plants were the most effective in the enhancement of pollutants bioavailability in the rizospheric soil. Plants growth induced physicochemical changes in soil and those are evidenced by increasing dehydrogenase activity and DDTs metabolism, mainly in soybean and tomato soil fractions. Root bioconcentration factors >1 were observed in 15 days tomato and alfalfa plants. Growth dilution effect was observed in roots of all species at 60 days, except soybean. DDTs uptake nor affected tomato and alfalfa plants growth neither caused oxidative stress. Considering the accumulation potential, tolerance (expressed as no evident phytotoxicity effects) and interaction with soil matrix in terms of metabolism and availability, tomato plants seems to be the best phytoremediator candidates for aged soil DDTs residues.

XRF scanners as a quick screening tool for detecting toxic pollutant elements in sediments from Marín harbour in the Ría de Pontevedra (NW Spain)

X-ray fluorescence scanners, such as the Itrax™ Core Scanner (Itrax) (Cox Analytical Systems, Mölndal, Sweden), provide high-resolution geochemical data within several hours. However, the semi-quantitative nature of these analysers has hampered their use to study pollution. This study explores Itrax’s capabilities to detect trace metals, such as Hg and Cd, in the Ría de Pontevedra harbour (NW Spain). A set of Itrax detection levels were proposed for each metal after comparison with quantitative measurements obtained from Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and Vapour Atomic Absorption Spectrometry (CVAAS) analyses. These quantitative data obtained after a sequential extraction were used to evaluate pollutant bioavailability and to determine metal pollution levels exhibiting Hg pollution. The reliability of inc/coh and Br/Cl ratios to assess the total organic matter variability was also evaluated. The results indicated that the Itrax is an efficient and fast option to monitor contamination, thereby avoiding laborious discrete analyses and reducing analytical cost and time.

Use of isotope dilution method to predict bioavailability of organic pollutants in historically contaminated sediments.

Many cases of severe environmental contamination arise from historical episodes, where recalcitrant contaminants have resided in the environment for a prolonged time, leading to potentially decreased bioavailability. Use of bioavailable concentrations over bulk chemical levels improves risk assessment and may play a critical role in determining the need for remediation or assessing the effectiveness of risk mitigation operations. In this study, we applied the principle of isotope dilution to quantify bioaccessibility of legacy contaminants DDT and PCBs in marine sediments from a Superfund site. After addition of 13C or deuterated analogues to a sediment sample, the isotope dilution reached a steady state within 24 h of mixing. At the steady state, the accessible fraction (E) derived by the isotope dilution method (IDM) ranged from 0.28 to 0.89 and was substantially smaller than 1 for most compounds, indicating reduced availability of the extensively aged residues. A strong linear relationship (R2 = 0.86) was found between E and the sum of rapid (Fr) and slow (Fs) desorption fractions determined by sequential Tenax desorption. The IDM-derived accessible concentration (Ce) was further shown to correlate closely with tissue residue in the marine benthic polychaete Neanthes arenaceodentata exposed in the same sediments. As shown in this study, the IDM approach involves only a few simple steps and may be readily adopted in laboratories equipped with mass spectrometers. This novel method is expected to be especially useful for historically contaminated sediments or soils, for which contaminant bioavailability may have changed significantly due to aging and other sequestration processes.

Time evolution of Pb(II) speciation in Pampa soil fractions

Soil pollution by heavy metals, particularly lead, is an important environmental concern; the bioavailability of such pollutants is strongly dependent on their chemical form. Here, the speciation of Pb(II) in soil fractions as a function of time shortly after its incorporation is studied, using a selective sequential extraction method. The sample came from an Argentinean Pampas region and was extensively characterised, including Rietveld analysis of the silt+clay fraction XRD pattern to find the major mineral components. Experiments were run twice, once in the winter and once in the summer. The results show different speciation time profiles in both cases, showing faster changes in winter due to the higher water content. The summer experiment corresponds to an earlier stage in the speciation profile evolution compared with winter. The soluble/exchangeable fraction decreases with time in summer but shows a lower and constant value in the winter. A high proportion is found to be adsorbed onto the stable (aluminosilicates+quartz) mineral fraction. The results strongly suggest that, even at a short time following soil pollution with Pb, a high proportion is adsorbed onto the mineral fraction, with only a low fraction being bioavailable. The most stable (mineral incorporated) form is observed to increase with time. Soil water content appears to be more important than temperature in determining the differences between the two.