Absorption and translocation of polybrominated diphenyl ethers (PBDEs) by plants from contaminated sewage sludge

Prioritization of chemical food safety hazards in the European feed supply chain

Extensive monitoring programs of chemical hazards in the animal feed chain are in place, both organized by public and private organizations. The objective of this review was to prioritize chemical hazards for monitoring in the European animal feed supply chain. A step-wise approach was designed for the prioritization, based on: historical occurrence of the chemicals in animal feed ingredients and animal feeds (in relation to European guidance values or maximum limits in feed); information on transfer of the chemical to edible animal products, and; the extent of human dietary intake of the products and possible adverse human health effects of the chemical. Possible prioritization outcomes were: high (H), medium (M), or low (L) priority for monitoring, or classification not possible (NC) because of limited available data on the transfer of the chemical to edible animal tissues. The selection of chemicals included (with results in parentheses): dioxins and polychlorinated biphenyls (H); brominated flame retardants (H); per- and polyfluorinated alkyl substances (H); the heavy metals arsenic (H) and cadmium (H) as well as lead (M) and mercury (M); aflatoxins (H), ochratoxin A (NC), and other mycotoxins (L); pyrrolizidine alkaloids (H) and other plant toxins (NC); organochlorine pesticides (H) and other pesticides (L); pharmaceutically active substances (M); hormones (NC); polycyclic aromatic hydrocarbons (L), heat-induced processing contaminants (NC), and mineral oils (NC). Results of this study can be used to support risk-based monitoring by food safety authorities and feed-producing companies in Europe.

Field study on the uptake pathways and their contributions to the accumulation of organophosphate esters, phthalates, and polycyclic aromatic hydrocarbons in upland rice

Plant uptake of organic contaminants generally occurs through either root, gas-phase foliar, or particle-phase foliar uptake. Understanding these pathways is essential for food-system practitioners to reduce human exposures, and to clean contaminated-sites with phytoremediation. Herein, we conducted a field-based experiment using an improved specific exposure chamber to elucidate the uptake pathways of organophosphate esters, phthalates, and polycyclic aromatic compounds, and quantitatively assessed their contributions to organic contaminant accumulations in field-grown rice. For most target compounds, all three uptake pathways (root, foliar gas, and foliar particle uptakes) contributed substantially to the overall contaminant burden in rice. Compounds with lower octanol-water partition coefficients (Kow) were more readily translocated from roots to leaves, and compounds with higher octanol-air partition coefficients (Koa) tended to enter rice leaves mostly through particle deposition. Most compounds were mostly stored in the inner leaves (55.3-98.2 %), whereas the relatively volatile compounds were more readily absorbed by the waxy layer and then transferred to the inner leaves. Air particle desorption was a key process regulating foliar uptake of low-volatility compounds. The results can help us to better understand and predict the environmental fate of those contaminants, and develop more effective management strategies for reducing their human exposure through food ingestion.

Chemicals/materials of emerging concern in farmlands: sources, crop uptake and potential human health risks

Certain chemicals/materials that are contaminants of emerging concern (CECs) have been widely detected in water bodies and terrestrial systems worldwide while other CECs occur at undetectable concentrations. The primary sources of CECs in farmlands are agricultural inputs, such as wastewater, biosolids, sewage sludge, and agricultural mulching films. The percent increase in cropland area during 1950-2016 was 30 and the rise in land use for food crops during 1960-2018 was 100-500%, implying that there could be a significant CEC burden in farmlands in the future. In fact, the alarming concentrations (μg kg^-1) of certain CECs such as PBDEs, PAEs, and PFOS that occur in farmlands are 383, 35 400 and 483, respectively. Also, metal nanoparticles are reported even at the mg kg^-1 level. Chronic root accumulation followed by translocation of CECs into plants results in their detectable concentrations in the final plant produce. Thus, there is a continuous flow of CECs from farmlands to agricultural produce, causing a serious threat to the terrestrial food chain. Consequently, CECs find their way to the human body directly through CEC-laden plant produce or indirectly via the meat of grazing animals. Thus, human health could be at the most critical risk since several CECs have been shown to cause cancers, disruption of endocrine and cognitive systems, maternal-foetal transfer, neurotoxicity, and genotoxicity. Overall, this comprehensive review provides updated information on contamination of chemicals/materials of concern in farmlands globally, sources for their entry, uptake by crop plants, and their likely impact on the terrestrial food chain and human health.

Integrating Biochar, Bacteria, and Plants for Sustainable Remediation of Soils Contaminated with Organic Pollutants

The contamination of soil with organic pollutants has been accelerated by agricultural and industrial development and poses a major threat to global ecosystems and human health. Various chemical and physical techniques have been developed to remediate soils contaminated with organic pollutants, but challenges related to cost, efficacy, and toxic byproducts often limit their sustainability. Fortunately, phytoremediation, achieved through the use of plants and associated microbiomes, has shown great promise for tackling environmental pollution; this technology has been tested both in the laboratory and in the field. Plant-microbe interactions further promote the efficacy of phytoremediation, with plant growth-promoting bacteria (PGPB) often used to assist the remediation of organic pollutants. However, the efficiency of microbe-assisted phytoremediation can be impeded by (i) high concentrations of secondary toxins, (ii) the absence of a suitable sink for these toxins, (iii) nutrient limitations, (iv) the lack of continued release of microbial inocula, and (v) the lack of shelter or porous habitats for planktonic organisms. In this regard, biochar affords unparalleled positive attributes that make it a suitable bacterial carrier and soil health enhancer. We propose that several barriers can be overcome by integrating plants, PGPB, and biochar for the remediation of organic pollutants in soil. Here, we explore the mechanisms by which biochar and PGPB can assist plants in the remediation of organic pollutants in soils, and thereby improve soil health. We analyze the cost-effectiveness, feasibility, life cycle, and practicality of this integration for sustainable restoration and management of soil.

Effects of ciprofloxacin on Eichhornia crassipes phytoremediation performance and physiology under hydroponic conditions

Antibiotics can be absorbed by aquatic plants, but they seriously affect the health of aquatic plants and threaten the steady state of aquatic ecosystem. The phytoremediation performance and physiology of floating macrophyte (Eichhornia crassipes) under antibiotic ciprofloxacin (CIP) hydroponic conditions were investigated. It was found that CIP absorption of E. crassipes was up to 84.38% and the root was the main absorption tissue. Hydrolysis and microbial degradation were the second removal pathway of CIP followed the plant absorption. After 7 days of CIP exposure, the photosynthesis efficiency of E. crassipes remained stable, and the presence of CIP did not inhibit the growth of the plant. On the 14th day, the superoxide dismutase and catalase activities were increased in response to the CIP stress. However, the tender leaves of E. crassipes turned white and shrivel, attributed to a decrease in chlorophyll content and chlorophyll fluorescence parameters after 21 days of CIP exposure. These findings will have significant implications for E. crassipes to absorb CIP on a limited time-scale and provide a phytoremediation technology for antibiotics in water.

First report on hydroxylated and methoxylated polybrominated diphenyl ethers in terrestrial environment from the Arctic and Antarctica

Terrestrial plants, which account for the world's largest biomass and constitute the basis of most food webs, take up, transform, and accumulate organic chemical contaminants from the ambient environment. In this study, we determined the concentrations and congener profiles of polybrominated diphenyl ethers (PBDEs) and hydroxylated and methoxylated polybrominated diphenyl ethers (OH-PBDEs and MeO-PBDEs) in surface soil and vegetation samples collected from the Arctic (Svalbard) and Antarctica (King George Island) during the Chinese Scientific Research Expeditions. The concentrations of total PBDEs (∑PBDEs) in soil and vegetation samples collected from the Arctic (5.6-270 pg/g dry weight) were higher than those from Antarctica (2.3-33 pg/g dw), whereas the concentrations of ∑MeO-PBDEs and ∑OH-PBDEs were lower in Arctic terrestrial samples (n.d.-0.75 and 0.0008-1.1 ng/g dw, respectively) than in samples from Antarctica (0.007-4.0 and 0.034-25 ng/g dw, respectively). Long-range atmospheric transport and human activities were potential sources of PBDEs in polar regions, whereas the dominance of ortho-substituted MeO-PBDE and OH-PBDE congeners in terrestrial matrices indicated the importance of natural sources. To the best of our knowledge, this study represents the first report on the levels and behaviors of MeO-PBDEs and OH-PBDEs in terrestrial environment of polar regions.

Polyethylene mesh knitted fabrics mulching the soil to mitigate China's haze: A potential source of PBDEs

The fate of polybrominated diphenyl ethers (PBDEs) from polyethylene mesh knitted fabrics (PMKFs) to mulched soil and nearby plants was studied. PBDEs in the soil sample collected from Tianjin University of Commerce in April 2019 increased significantly after 6 months of PMKF mulching owing to PMKFs as the main input source. The compositional profiles/congener patterns of the PBDEs in the soil and PMKFs became similar after 6 months. High correlations were found between ΣPBDEs in the soil and PMKFs in October 2019, with no significant correlation in April. Plants could take up, accumulate and biotransform PBDEs in contaminated soil. The uptake of BDE-209 by plants was the highest compared with other lesser brominated PBDE congeners, due to its higher log Kow value and molecular weight or size. BDE-47 taken up in the plant was biotransformed via hydroxylation. These results prove that the government's PMKF solution to haze is causing environmental problems in bare soil, i.e., PBDE pollution in both soil and nearby plants. The present study provides important pieces of evidence for government and policymakers, and it is recommended that one environmental problem is not solved by creating another.

Effects of iron plaque and fatty acids on the transfer of BDE-209 from soil to rice under iron mineral Fenton-like oxidation condition

To understand the effect mechanisms of iron plaque and fatty acids on the migration of PBDEs from soil to rice (Oryza sativa), pot experiments were conducted in the soil spiked with decabromodiphenyl ether (BDE-209) under the conditions of tourmaline and nano-goethite Fenton-like treatments. The results showed that iron mineral Fenton-like oxidation could effectively remove BDE-209 from rhizosphere soil, the highest removal rate obtained 89.29% with the addition of 0.4 mmol/L H₂O₂ and 8 g nano-goethite (G + 3H group). Iron mineral Fenton-like oxidation could produce iron plaque (IP) on rice roots and accumulate a part of contaminants on the surface of IP, further weakening BDE-209 uptake in the plants. Additionally, the occurrence of fatty acid variation induced by BDE-209 stress, iron mineral Fenton-like oxidation at high concentrations of H₂O₂ with 0.4 mmol/L affected the distribution of fatty acids in plant tissues, especially for C_18:0 fatty acid. While the IP on rice roots prevented the BDE-209 into plant, it was also closely related to the distribution of fatty acids in rice, altering BDE-209 accumulation in the rice. To safely use the iron mineral Fenton-like oxidation in the agricultural soil remediation, the safety of plant cells treated by mineral Fenton-like oxidation was evaluated using the transmission electron microscopy (TEM) and enzyme activity determination, which indicated that iron mineral Fenton-like oxidation would destroy the inner structures of plant cells, especially for G + 3H group.

Polybrominated diphenyl ethers (PBDEs) concentrations in soil and plants around municipal dumpsites in Abuja, Nigeria

Polybrominated diphenyl ethers (PBDEs) are listed as persistent organic pollutants (POPs) in the Stockholm Convention. It has been established that PBDEs may be released into the environment during improper handling and disposal of e-waste and other products containing PBDEs that is prevalent in developing countries. This research work assessed the status of PBDE contamination at dumpsites in Nigeria. Soil and edible plant samples were collected from the dumpsites and control sites for analysis. The concentrations of ∑₇PBDE in the topsoils around the dumpsites at 0-15 cm depth ranged from 112 to 366 ng/g dry weight (dw) while that of the topsoil of the control site 500 m from the dumpsite ranged from 26.8 to 39.7 ng/g dw. These high concentrations stem likely from open burning of waste including electronic waste on the landfills. Plant samples (bentgrass, spinach, tomatoes, pumpkin and sweet potatoes) around the dumpsites were found to be contaminated by PBDEs with levels ranging from 25.0 to 60.5 ng/g dw in plant roots and from 8.45 to 32.2 ng/g dw in plant shoots for ∑₇PBDE. This suggests that consumption of vegetables by humans and ingestion of contaminated soils and feed by chickens and cows can transfer PBDEs into the human food chain around the dumpsites. The comparison of PBDE levels in soils and the PBDE levels in chicken eggs from the former study indicate that PBDE levels in the soils are sufficient to explain the levels in the chicken eggs with a reasonable carry-over rate for PBDEs of 0.28 on average. The PBDE contamination in the soil was sufficient to result in a relevant exposure of humans via accumulation in eggs. The study shows that a better management of end-of-life products containing PBDEs is needed to reduce PBDE exposure risk in Africa.

Enhanced remediation of BDE-209 in contaminated mangrove sediment by planting and aquaculture effluent

Toxic and persistent flame retardant (BDE-209) and aquaculture effluent (AE) are ubiquitous in coastal environments, but how their co-existence influences their fate is not yet investigated. This study investigated AE effects on remediation and uptake of BDE-209 by Kandelia obovata (Ko) and Avicennia marina (Am), true and dominant mangrove species. After 12-months, a significant removal of BDE-209 was achieved in planted mangrove sediment and the removal was significantly enhanced by AE addition, possibly due to the enhancement of nitrogen (N) and phosphorous (P) content in sediment. Residual percentages of parent BDE-209 in Ko and Am planted sediments without AE were 61.4% and 70.9%, respectively, but decreased to 46.9% and 48.0% with AE addition after 12-months. A similar trend was found in unplanted sediment, with 86.5% and 65.3% of BDE-209 retained in sediments without and with AE addition, respectively. The results demonstrated that AE addition not only increased the debromination of BDE-209 in all treated sediments with the production of debrominated congeners (de-PBDEs) like di- to nona-BDEs in unplanted and planted sediments, but also enhanced the take up of BDE-209 in Ko root, and de-PBDEs in both Ko and Am, thus enhancing the phytoremediation of BDE-209 in contaminated sediments.

Field study on bioaccumulation and translocation of polybrominated diphenyl ethers in the sediment-plant system of a national nature reserve, North China

Polybrominated diphenyl ethers (PBDEs) are the ubiquitous contaminants in the coastal wetlands, with high persistence and toxicity. Environmental behaviors of PBDEs in sediment-plant system is a hot research area, where much uncertainties still occurred in field environment. In this study, the sediments and Suaeda heteroptera were synchronously collected to investigate the bioaccumulation and translocation of PBDEs in Liaohe coastal wetland. Mean concentrations of PBDEs in sediments, roots, stems and leaves were 8.37, 6.64, 2.42 and 1.40 ng/g d.w., respectively. Tissue-specific accumulation of PBDEs were detected in Suaeda heteroptera, with predominant accumulation in roots. Congener patterns of PBDEs were similar between sediments and roots, demonstrating root uptake as the key pathway of PBDE bioaccumulation. The proportions of lower brominated congeners increased from roots to leaves, implying the congener-specific translocation. Meanwhile, the lower brominated congeners exhibited higher sediment-tissue bioaccumulation (AFs) and translocation factors (TFs) compared to higher brominated congeners in Suaeda heteroptera, further verifying their preferential translocation. AFs and TFs of PBDEs were both not correlated with their log K_ow, which was inconsistent with those of laboratory studies, reflecting the complicated behaviors of PBDEs in field environment. This is the first comprehensive report on bioaccumulation and translocation of PBDEs within Suaeda heteroptera in Liaohe coastal wetland.

Effects of tourmaline catalyzed Fenton-like combined with bioremediation on the migration of PBDEs in soil-plant systems: Soil properties and physiological response of lettuce and selective uptake of PBDEs

A series of pollutants can be removed from soil using a Fenton-like oxidation and biological treatment. As a natural mineral, tourmaline has been used for as a material of Fenton-like reaction. In the present study, the risks of remediation technology tourmaline catalyzed Fenton-like reaction (TCFR) combined with Phanerochaete chrysosporium (TCFR + P) were assessed through measuring soil properties, physiological response of plant, and PBDEs migration from soil to plant. Batch pot experiments showed that the silicon contents, specific surface area and soil pore size of soil in TCFR and 5%TCFR + P groups increased obviously. TCFR and TCFR + P treatments promoted the lettuce growth compared to control. Moreover, chlorophyll content of lettuce in 2%TCFR + P and 5%TCFR + P group increased by 46.74% and 44.57% than that in the CK, respectively. The treatment of 2%TCFR decreased the total concentration of PBDEs in rhizosphere soil and non-rhizosphere soil by 52.0.2% and 64.17%, respectively, after 60 days compared to the soil of CK, and did not prompt the uptake of lower-brominated PBDEs by lettuce. TCFR and TCFR + P can alter the migration of BDE isomers from soil to plant, the ratio of BDE99/BDE100 in lettuce shoots decreased slightly. BDE-99/BDE-100 ratios in the shoots were lower than those in the roots, while BDE153/BDE154 ratios were higher than 1.0 and ratios in shoots were higher than those in roots. Therefore, our findings illustrated that the TCFR could be applied to remediate the agricultural soil, considering the appropriate doses of tourmaline.

Accumulation and translocation of polybrominated diphenyl ethers into plant under multiple exposure scenarios

Plant foliar uptake is an essential part of the overall biogeochemical cycling of semivolatile organic compounds. Chambers were therefore designed to expose wheat to polybrominated diphenyl ethers (PBDEs) via various combinations of exposure routes (i.e., soil, air and particle). Under the simulated scenarios, most of PBDEs in wheat leaves originated from foliar uptake (including gaseous and particle-bound depositions) rather than translocation from root uptake. Our results further revealed that higher brominated PBDEs (h-PBDEs; i.e. hepta- through deca-BDEs) were inclined to enter wheat leaves via particle-bound deposition while gaseous deposition could not be ignored for less-brominated PBDEs (l-PBDEs; i.e., tri- through hexa-BDEs). Sequential extraction of wheat leaf displayed that the transfer velocities of h-PBDEs were lagged behind l-PBDEs during their deposition to leaf cuticle and subsequent erosion to mesophyll, where a large fraction of the target chemicals were ultimately stored (29-93% of total PBDEs burden). Applying McLachlan's framework to our data suggested that the uptake of PBDEs was controlled primarily by kinetically limited gaseous deposition for l-PBDEs and by particle-bound deposition for h-PBDEs. The combined use of exposure chamber measurement and framework provides a robust tool for interpreting the behaviors of PBDEs between the atmosphere and plant foliage.

Uptake and transformation of decabromodiphenyl ether in different rice cultivars: Evidence from a carbon-14 study

The differences of PBDE absorption, accumulation, and metabolism in different cultivars of the same crop are rarely explored. This study used ¹⁴C tracing to fully demonstrate the uptake and transformation of soil-borne BDE209 in three rice cultivars, including two indica (HHZ and YD1) and one japonica cultivars (NJ3). Results showed that about 6.9, 17.2, and 17.4% of the applied ¹⁴C-BDE209 were transformed to ¹⁴C-metabolites in soils planted with HHZ, YD1, and NJ3, respectively. The ¹⁴C-BDE209 and its ¹⁴C-metabolites in soil could be absorbed by the rice and gradually transported to its root, stem, leaf, and grain, with the total whole-plant uptake of 8.52, 4.55 and 3.43 nmol for HHZ, YD1, and NJ3, respectively. The cultivar of HHZ had the greatest whole-plant ¹⁴C absorption but the lowest ΣPBDEs residues in its grain, with the ΣPBDEs of 421.8, 454.2 and 967.0 ng g^-1 for HHZ, YD1, and NJ3, respectively. BDE-209 accounted for 90%, 31% and 50% of the ΣPBDEs in the grain from HHZ, YD1, and NJ3, respectively. The estimated daily intake (EDI) amounts of ΣPBDEs were 928, 1056, and 2675 ng kg^-1 bw d^-1 via consuming rice grains from HHZ, YD1, and NJ3, respectively, which were below the safe threshold limits for human consumption. This study proved the different BDE-209 absorption, accumulation and transformation in different rice cultivars, which potentially suggests the need of considering cultivar differences in assessing the dietary risks of PBDEs.

Concentrations and uptake pathways of polychlorinated biphenyls from soil to grass

Field coupled samples in soil and grass were collected to determine the concentrations and identify the uptake pathways of PCBs into the grass at a pasture from Scotland, UK. Concentrations of indicator PCBs (∑₇PCBs) in soils ranged from 0.20 to 0.88 ng g^-1 dw (dry weight), with a mean of 0.33 ng g^-1 dw, and in grass ranged from 0.20 to 2.14 ng g^-1 dw, with a mean of 0.48 ng g^-1 dw. The comprehensive factors of low concentrations and detection rate (PCB28: 18.8%; PCB52: 37.5%) of PCBs in soil, as well as continuously declined air concentrations of PCBs in the UK since the 1990s suggested that the secondary emission from the soil is becoming the supplied source of PCBs to air and grass. The significant correlations between bioconcentration factor (BCF) values and the log K_OW (R = -0.850, p < 0.05) and log K_OA (R = -0.860, p < 0.05) of indicator PCB congeners were found in the present study, indicating that these two parameters are likely to affect the bioaccumulation and uptake of grass. A generic one-compartment model was employed to identify uptake pathways of grass and evaluate the uptake amounts for PCBs. This suggested that the most important pathway for uptake of PCBs by grass was at the aerial part, and the difference of PCBs concentrations between leaves and roots was about four orders of magnitude. Removing and risk transfer of PCBs or other organic pollutants by grass need to be investigated and assessed further.

Could mangrove plants tolerate and remove BDE-209 in contaminated sediments upon long-term exposure?

Polybrominated diphenyl ethers (PBDEs) such as BDE-209, the commonest congener, are known to be toxic. A 24-months study using mangrove mesocosms with mixed mangrove species, namely Avicennia marina (Am), Aegiceras corniculatum (Ac) and Kandelia obovata (Ko), or without any plant was conducted to examine toxicity, removal, translocation and uptake of BDE-209. At month 24, BDE-209 stimulated the production of root superoxide radical (O₂^-*), and leaf and root malondialdehyde (MDA) of Ko, enhanced leaf O₂^-* of Ac, but did not affect the production of O₂^-* and MDA in Am. These findings indicated that the tolerance to BDE-209 was species-specific, with Am being the most tolerant and Ko the most sensitive species. In leaf and root, BDE-209 stimulated peroxidase (POD) activity in both Ac and Ko, and superoxide dismutase (SOD) in Am. After 24-months, more than 60% and 40% of BDE-209 in contaminated sediments were removed in planted and unplanted groups, respectively, with more PBDEs in upper than bottom sediment layers. This study demonstrates that planting tolerant species such as Avicennia marina with high uptake could remedy PBDEs in contaminated sediments.

Biochar combined with compost to reduce the mobility, bioavailability and plant uptake of 2,2',4,4'-tetrabrominated diphenyl ether in soil

Biochar application to soil is recognised for its capacity to immobilise pollutants (through sorption) while composted inputs can accelerate the biodegradation of organic pollutants. However, little is known about the influence of combined incorporation on plant uptake of organic pollutants. Therefore, we investigated the effects of maize straw-derived biochar (MSB), compost derived from maize straw and pig manure (SMC), and their combination (MSB-SMC) as soil amendments on bioavailability of 2,2',4,4'-tetrabrominated diphenyl ether (BDE-47) and carrot (Daucus carota L.) uptake in a horticultural soil. We found that biochar alone performed well in reducing BDE-47 bioavailability, but was less effective at degrading the pollutant. Conversely, addition of compost stimulated BDE-47 biodegradation. MSB-SMC enhanced BDE-47 biodegradation in soil, reduced contamination of carrot roots, and caused significant reductions in soil extractable BDE-47. The combination of contrasting approaches to remediation thus resulted in the most favorable outcome for a contaminated soil: immobilisation of contaminant from vegetable crops (via biochar) with simultaneous bioremediation of the growing medium. These findings point towards an effective strategy for reducing plant uptake of PDBEs through the combined use of biochar and compost as soil amendment - reducing mobility and facilitating degradation of the accessible contaminant fractions.

Solubility, uptake, and translocation of BDE 47 as affected by DOM extracted from agricultural wastes

Dissolved organic matter (DOM) extracted from wheat straw (SDOM) and cow manure (MDOM) were used to investigate their effects on the solubilization, uptake, and translocation of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47). Partition coefficients (K_DOC) of BDE 47 between water and the two types of DOM were measured by the solubility enhancement method. The uptake and translocation of BDE 47 by wheat plants were explored by hydroponic exposure experiments. In the range of 0 to 100 mg/L of DOM, the solubility of BDE 47 increased with increasing concentrations of DOM. The log [K_DOC] values of BDE 47 in SDOM and MDOM solutions were 5.77 and 5.31, respectively. The log [K_DOC] values of BDE 47 in SDOM solutions were higher than those in MDOM solutions, which might be ascribed to the higher content of aliphatic carbon and lower molecular weight of SDOM. The addition of DOM (50 mg/L) significantly increased the accumulation of BDE 47 in the shoots of wheat plants. Wheat straw DOM had greater effect than MDOM in enhancing the accumulation of BDE 47. This study demonstrated the potential risk of BDE 47 to plants resulting from DOM-facilitated transport or the changes in metabolic properties.

Reducing plant uptake of a brominated contaminant (2,2',4,4'‑tetrabrominated diphenyl ether) by incorporation of maize straw into horticultural soil

Application of crop residues is a conventional practice that contributes to crop production through nutrient returns and other benefits to soil health: driving soil physicochemical and biological functions. However, little is known about the impacts of straw residue incorporation on the bioavailability of organic pollutants and associated changes in microbial community structure in contaminated soils. In this study, maize straw was added to a soil contaminated with a model polybrominated diphenyl ether (BDE-47). A pot experiment was conducted and planted with carrot (Daucus carota L.). We found that straw addition greatly reduced the bioavailability of BDE-47, changed the bacterial community structure and affected a range of soil physiochemical properties. Moreover, the amount of BDE-47 that had accumulated in carrot roots and aboveground tissues was significantly reduced. This study may therefore describe an effective agronomic strategy to reduce the bioavailability of polybrominated diphenyl ethers (PBDEs) in a soil used to grow high value vegetable crops. This strategy draws on traditional wisdom and shows promise as a practical method to support horticultural production systems, remediate soils, and help to ensure food safety.

Translocation of polybrominated diphenyl ethers from field-contaminated soils to an edible plant

Polybrominated diphenyl ethers (PBDEs), recognised emerging contaminants, widely exist and persist in the environment. Samples were taken from a heavily contaminated farm in Taiwan located near a factory known to regularly use PBDEs. Sweet potato vines (Ipomoea batatas L., a commonly consumed vegetable in Asia) growing in the surrounding farmlands were found to contain a high concentration of PBDEs of 19.36 ng/g. The possibility of PBDEs translocation into sweet potato vines from soil samples was evaluated. To prevent the PBDEs from air through that factory, the pot experiments were performed in a greenhouse, which showed that the PBDEs concentration of 24 congeners (tri- through deca-BDE) in the sweet potato vine after 14-days cultivation was 29.90 ng/g, 40-times higher than that in the contaminated soil. After another 14-days, the PBDE concentration decreased to 12.30 ng/g as high-brominated PBDEs were transformed to medium- and/or low-brominated PBDEs in the sweet potato vine. The bioconcentration factor (BCF) values exceeded 20.0 for most of the deca-, nona-, and octa-BDEs but BCFs were below 18.9 for the rest of the medium- and low-brominated PBDEs. Our results demonstrate that high-brominated PBDEs can translocate into leafy vegetables from soils, and sweet potato vines tend to accumulate high-brominated PBDEs into their edible parts.

Phytoremediation of soil co-contaminated with Cd and BDE-209 using hyperaccumulator enhanced by AM fungi and surfactant

Pot experiments were conducted to investigate the uptake and translocation of both Cd and decabromodiphenyl ether (BDE-209) in Solanum nigrum, under the treatments of two arbuscular mycorrhizal fungi [AMF, Funneliformis mosseae (FM) and Rhizophagus intraradices (RI)] and surfactant β-cyclodextrin (β-CD). Results showed that S. nigrum treated with either FM or β-CD significantly elevated shoot biomass and Cd concentrations and contents in shoots. The concentrations of BDE-209 in shoots and the dissipation and debromination efficiencies of BDE-209 in soil were significantly enhanced in S. nigrum treated with β-CD, inoculated with or without AMF. Moreover, significant positive correlations were found between the BDE-209 dissipation efficiency, the BDE-209 concentrations and contents in roots, and the soil enzymatic activities (polyphenol oxidase or dehydrogenase activities) and between the Cd and BDE-209 contents in shoots or roots. Higher concentrations of lower-brominated products and total PBDEs were detected in shoots than in roots suggesting that BDE-209 might be initially absorbed by roots, then translocated to shoots, and then degraded into lower brominated products in shoots. Considering the plant uptake of Cd and BDE-209 and the efficient removal of those chemicals in soils, the combination of S. nigrum and β-CD inoculated with or without AMF may be viable alternatives for phytoremediation of the co-contaminated soil.

Effects of biochar on phytotoxicity and translocation of polybrominated diphenyl ethers in Ni/Fe bimetallic nanoparticle-treated soil

In this study, soil culture experiments were conducted to explore the effects of biochar-supported Ni/Fe nanoparticles on the accumulation and translocation of polybrominated diphenyl ethers (PBDEs) in soil-plant system and its phytotoxicity to Brassica chinensis. Compared with those in BDE209 contaminated soils (S ₁) and Ni/Fe nanoparticle-treated soil (S ₃), the plant biomass, root, and shoot lengths in biochar-supported Ni/Fe nanoparticle-treated soil (S ₄) were increased by 23 mg, 1.35 cm, and 2.08 cm and 27.2 mg, 1.75 cm, and 2.52 cm, respectively, suggesting that the phytotoxicity in S ₄ treatment was significantly decreased. Moreover, in all treatments, the contents of BDE209, the total PBDEs, Ni, and Fe in sample plant tissues of S ₄ were the lowest. In addition, the superoxide dismutase, peroxidase, and catalase activities in S ₄ treatment were found to decrease by 33.8, 47.2, and 24.1%, respectively, compared to those in S ₃. Results also showed that biochar addition not only reduced the uptake of PBDEs and heavy metals but also effectively improve soil fertility and reduce the leachability of Ni and Fe caused by Ni/Fe. Finally, the translocation factors (TFs) of PBDEs in four treatments followed the orders as S ₁ > S ₃ > S ₄ > S ₂, indicating that biochar has an inhibition effects on PBDE translocation in the plants. In summary, all of the results suggested that the phytotoxicity, translocation of PBDEs, and the negative effects caused by neat Ni/Fe nanoparticles in B. chinensis were decreased as a result of the effects of the biochar.

Antioxidative response of Kandelia obovata, a true mangrove species, to polybrominated diphenyl ethers (BDE-99 and BDE-209) during germination and early growth

A 3-months microcosm experiment with mangrove sediment spiked with PBDEs and planted with propagules of Kandelia obovata was conducted to investigate PBDE toxicity and antioxidative responses of the germinated seedlings. BDE-99 suppressed germination rate, leaves formation and growth of mangrove seedlings. The leaves and roots of BDE-99 treated seedlings had significantly higher superoxide (O₂^-) release, malondialdehyde (MDA) and total polyphenol (TP) content, and peroxidase (POD) activity than the control. BDE-209 increased activities of all three antioxidative enzymes, catalase (CAT), POD and superoxide dismutase (SOD) in roots, but in leaves, only CAT activity was stimulated. The MDA content of BDE-209 treated seedlings was less than the control. PBDEs were found in plant tissues of the treated seedlings. These results indicated that even though PBDEs were taken up in tissues, K. obovata, due to its antioxidative defense enzymes, could tolerate PBDEs and could be used for the bioremediation of PBDE-contaminated environments.

Occurrence, distribution and bioaccumulation behaviour of hydrophobic organic contaminants in a large-scale constructed wetland in Singapore

This study involved a field-based investigation to assess the occurrence, distribution and bioaccumulation behaviour of hydrophobic organic contaminants in a large-scale constructed wetland. Samples of raw leachate, water and wetland plants, Typha angustifolia, were collected for chemical analysis. Target contaminants included polychlorinated biphenyls (PCBs), organochlorine pesticides (OCP), as well as several halogenated flame retardants (HFRs) and personal care products (triclosan and synthetic musks). In addition to PCBs and OCPs, synthetic musks, triclosan (TCS) and dechlorane plus stereoisomers (syn- and anti-DPs) were frequently detected. Root concentration factors (log RCF L/kg wet weight) of the various contaminants ranged between 3.0 and 7.9. Leaf concentration factors (log LCF L/kg wet weight) ranged between 2.4 and 8.2. syn- and anti-DPs exhibited the greatest RCF and LCF values. A strong linear relationship was observed between log RCF and octanol-water partition coefficient (log K_OW). Translocation factors (log TFs) were negatively correlated with log K_OW. The results demonstrate that more hydrophobic compounds exhibit higher degrees of partitioning into plant roots and are less effectively transported from roots to plant leaves. Methyl triclosan (MTCS) and 2,8-dichlorodibenzo-p-dioxin (DCDD), TCS degradation products, exhibited relatively high concentrations in roots and leaves., highlighting the importance of degradation/biotransformation. The results further suggest that Typha angustifolia in this constructed wetland can aid the removal of hydrophobic organic contaminants present in this landfill leachate. The findings will aid future investigations regarding the fate and bioaccumulation of hydrophobic organic contaminants in constructed wetlands.

Efficiency and mechanism of the phytoremediation of decabromodiphenyl ether-contaminated sediments by aquatic macrophyte Scirpus validus

Phytoremediation is an economic and promising technique for removing toxic pollutants from the environment. Freshwater sediments are regarded as the ultimate sink of the widely used PBDE congener decabromodiphenyl ether (BDE-209) in the environment. In the study, the aquatic macrophyte Scirpus validus was selected to remove BDE-209 from three types of sediments (silt, clay, and sand) at an environmentally relevant concentration. After 18 months of phytoremediation experiment, S. validus significantly enhanced the dissipation rates of BDE-209 in all the sediments compared to the controls. Average removal rates of BDE-209 in the three treatments of silt, clay, and sandy sediments with S. validus were respectively 92.84, 84.04, and 72.22%, which were 148, 197, and 233% higher than that in the control sediments without S. validus. In the phytoremediation process, the macrophyte-rhizosphere microbe combined degradation was the main pathway of BDE-209 removal. Sixteen lower brominated PBDE congeners (di- to nona-) were detected in the sediments and plant tissues, confirming metabolic debromination of BDE-209 in S. validus. A relatively higher proportion of penta- and di-BDE congeners among the metabolites in plant tissues than that in the sediments indicated further debromination of PBDEs within plants. The populations and activities of microorganisms in the sediments were greatly promoted by S. validus. Bacterial community structure in BDE-209-contaminated rhizosphere sediments was different from that in the control rhizosphere sediment, as indicated by the dominant proportions of β-proteobacteria, δ-proteobacteria, α-proteobacteria, Acidobacteria, and Chloroflexi in the microbial flora. All these results suggested that S. validus was effective in phytoremediation of BDE-209 by the macrophyte-rhizosphere microbe combined degradation in aquatic sediments.

Partition uptake of a brominated diphenyl ether by the edible plant root of white radish (Raphanus sativus L.)

Polybrominated diphenyl ethers (PBDEs) are of a class of emerging contaminants. In this study, the accumulation of 4-bromodiphenyl ether (BDE-3) by different parts of a live white radish was investigated. Different cultural media (hydroponics, silica sand, and soil) were used to sustain the radish plant during its uptake and in-plant translocation of BDE-3. The results showed that BDE-3 can be translocated from the roots to the aboveground organs and the accumulated levels of BDE-3 in different parts of the white radish followed the order for the three types of cultivation: fibrous roots > peels > main roots > leaves. The results were analyzed by the aid of the partition-limited model for the plant uptake. The relevant partition coefficients (K_OC and K_d) and uptake parameters of BDE-3 with plant components (K_pt and K_lip) were obtained for analyzing the BDE-3 distribution. The partition-limited model offers a significant insight into the uptakes of BDE-3 by the various components of live white radishes. The types of cultivation affected the total sorption level, translocation factors (TFs), extent to equilibrium (α_pt), and root concentration factors (RCFs).

Plant-bacteria partnerships for the remediation of persistent organic pollutants

High toxicity, bioaccumulation factor and widespread dispersal of persistent organic pollutants (POPs) cause environmental and human health hazards. The combined use of plants and bacteria is a promising approach for the remediation of soil and water contaminated with POPs. Plants provide residency and nutrients to their associated rhizosphere and endophytic bacteria. In return, the bacteria support plant growth by the degradation and detoxification of POPs. Moreover, they improve plant growth and health due to their innate plant growth-promoting mechanisms. This review provides a critical view of factors that affect absorption and translocation of POPs in plants and the limitations that plant have to deal with during the remediation of POPs. Moreover, the synergistic effects of plant-bacteria interactions in the phytoremediation of organic pollutants with special reference to POPs are discussed.

Linking toxicity profiles to pollutants in sludge and sediments

Obtaining a complex picture of how pollutants synergistically influence toxicity of a system requires statistical correlation of chemical and ecotoxicological data. In this study, we determined concentrations of eight potentially toxic metals (PTMs) and four groups of organic pollutants in 15 sewage sludge and 12 river sediment samples, then linked measured contaminant concentrations to the toxicity of each matrix through constrained correspondence analysis (CCA). In sludge samples, Hg, As, hexachlorohexane (HCH), polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCD) influenced the toxicity profiles, with the first four having significant effects and HBCD being marginally significant. In sediment samples, Hg, As, PBDEs, hexachlorobenzene (HCB), dichlorodiphenyltrichloroethane (DDT), HBCD, HCH and polycyclic aromatic hydrocarbons (PAHs) were found to explain toxicity profiles with Hg, As, PBDEs, HCB, DDT, HBCD, and HCH having significant effects and PAHs being marginally significant. Interestingly, HCH was present in small amounts yet proved to have a significant impact on toxicity. To the contrary, PAHs were often present in high amounts, yet proved to be only marginally significant for sediment toxicity. These results indicate that statistical correlation of chemical and ecotoxicological data can provide more detailed understanding of the role played by specific pollutants in shaping toxicity of sludge and sediments.

Insight into the long-term effect of mangrove species on removal of polybrominated diphenyl ethers (PBDEs) from BDE-47 contaminated sediments

Polybrominated diphenyl ethers (PBDEs) have become ubiquitous environmental contaminants, particularly in mangrove wetlands. However, little is known about the long-term effect of mangrove plants on PBDE removal from contaminated sediments. A 12-month microcosm experiment was conducted to understand the effect of two mangrove species, namely Avicennia marina (Am) and Aegiceras corniculatum (Ac), on PBDE removal from the sediments spiked with 2000ngg^-1 dry weight of BDE-47, and to explore the microbial mechanism responsible for the planting-induced effects on BDE-47 removal. Results showed that planting of mangrove species, either Am or Ac, could accelerate BDE-47 removal from contaminated sediments during the 12months experiment, mainly through enhancing microbial degradation process. In particular, Am sediment had significantly higher BDE-47 degradation efficiency compared with Ac sediment, which may be mainly attributed to higher activities of urease and dehydrogenase, as well as higher 16S rRNA gene copies of total bacteria and organohalide-respiring bacteria (OHRB) in Am sediment. Moreover, planting could shift sediment bacterial community composition and selectively enrich some bacterial genera responsible for PBDE degradation. Such selective enrichment effect of Am on the potential PBDE-degrading bacteria differed distinctly from that of Ac. These results indicated that long-term planting of mangrove species, especially Am, could significantly promote BDE-47 removal from the contaminated sediments by enhancing microbial activity, increasing total bacterial and OHRB abundances and altering bacterial community composition.

Brominated flame retardants and perfluoroalkyl acids in groundwater, tile drainage, soil, and crop grain following a high application of municipal biosolids to a field

Dewatered municipal biosolids (DMB) were applied at a rate of 22Mgdwha^-1 to an agricultural field in fall 2008. Concentrations of polybrominated diphenyl ethers (PBDEs; BDE-47, -99, -100, -153, -154, -183, -197, -207, -209), other brominated flame retardants (BFRs; HBB, PBEB, DBDPE, BTBPE) and perfluoroalkyl acids (PFAAs; PFHxS, PFOS, PFDS, PFOSA, PFHpA, PFOA, PFNA, PFDA, PFUnA, PFDoA, PFTA) were monitored in tile drainage, groundwater (2m, 4m and 6m depth), soil cores (0-0.3m) pre- and post-application, DMB aggregates incorporated into the soil post-application, and in wheat (Triticum spp.) planted post-application. Several compounds were detected in soil and water pre-application and on a reference field plot. PBDEs, other BFRs and PFAAs were detected in tile drainage and 2m groundwater throughout the post-application study period; a few PBDEs were also detected sporadically at lower depths in groundwater. Some of these compounds had not been detected pre-application, while some exceeded reference field plot/pre-application levels (some significantly (p<0.05) in tile drainage); both cases indicating biosolid-based water contamination. In DMB aggregates, several PBDE congeners were found to have dissipated exponentially, with reductions >90% in many of them within 1year post-application. Exponential dissipation of other BFRs and PFAAs in DMB aggregates were not significant. No PBDEs, other BFRs, or PFAAs were detected in wheat grain.

Uptake of perfluoroalkyl substances and halogenated flame retardants by crop plants grown in biosolids-amended soils

The bioaccumulation behavior of perfluoroalkyl substances (PFASs) and halogenated flame retardants (HFRs) was examined in three horticultural crops and earthworms. Two species, spinach (Spinacia oleracea) and tomato (Solanum lycopersicum L.), were grown in field soil amended with a single application of biosolids (at agronomic rate for nitrogen), to represent the scenario using commercial biosolids as fertilizer, and the third crop, corn (Zea mays) was grown in spiked soil (~50mg PFOS/kg soil, ~5mg Deca-BDE/kg soil and a mixture of both, ~50mg PFOS and ~5mg Deca-BDE/kg soil) to represent a worst-case scenario. To examine the bioaccumulation in soil invertebrates, earthworms (Eisenia andrei) were exposed to the spiked soil where corn had been grown. PFASs and HFRs were detected in the three crops and earthworms. To evaluate the distribution of the compounds in the different plant tissues, transfer factors (TFs) were calculated, with TF values higher for PFASs than PBDEs in all crop plants: from 2 to 9-fold in spinach, 2 to 34-fold in tomato and 11 to 309-fold in corn. Bioaccumulation factor (BAF) values in earthworms were also higher for PFASs (4.06±2.23) than PBDEs (0.02±0.02).

Plant selective uptake of halogenated flame retardants at an e-waste recycling site in southern China

The concentrations and homolog patterns of halogenated flame retardants (HFRs) in vegetables grown at an e-waste contaminated site were investigated. Polybrominated diphenyl ethers (PBDEs) were the dominant HFRs in vegetable tissues, with concentrations ranging from 10.3 to 164 ng g(-1) and 1.16-107 ng g(-1) in shoots and roots, respectively, followed by novel brominated flame retardants (NBFRs) and dechlorane plus (DPs). This is an indication that PBDE contamination in vegetables grown around e-waste recycling sites may pose a risk to the local terrestrial ecosystem and residents. In addition, this is the first report on the concentrations and compositions of NBFRs in vegetables around e-waste recycling sites. The HFRs concentrations in vegetables varied greatly with the vegetable species, with the highest concentrations observed in Brassica oleracea var. capitata. Root concentration factors (RCF) decreased with increasing log Kow of HFRs, which indicated that the uptake of HFRs was controlled mainly by log Kow. Dissimilar HFRs profiles in shoots and roots suggested that the uptake and translocation of HFRs by plants were selective, with lower halogenated congeners prone to accumulation in vegetable tissues. Positive relationships between PBDEs and their substitutes were observed in vegetable tissues, suggesting that the replacement of PBDEs by NBFRs has not resulted in an obvious transition in plants within the study area.

Sorption equilibrium of emerging and traditional organic contaminants in leafy rape, Chinese mustard, lettuce and Chinese cabbage

Emerging and petroleum contaminants could transfer into food chains by plant uptake, potentially causing food security problems. To build a prediction model, the sorption equilibrium and uptake kinetics of toluene, p-xylene, naphthalene, bisphenol A, and 4-bromo-diphenyl ether in some common leafy vegetables including leafy rape, Chinese mustard, lettuce and Chinese cabbage were examined. The kinetic experiments revealed that high sorption rates were observed for these plants that had high lipid contents. For two emerging contaminants with polar functional groups, their resulting isotherms were strongly linear (R(2) = 0.92 to 1.00), indicating that the sorption was dominated by partitioning. Moreover, regression correlation showed that log Klip, the lipid-water partition coefficient, and log Kow, the octanol-water coefficient, for these organic chemicals were strongly linear-related, following the equation: log Klip = 0.894 × log Kow+0.219 (R(2) = 0.953). The correlation equation allows the prediction of the sorption capacity of plant species for an organic compound when the plant composition and the log Kow of the chemical are determined. This improved model containing different organic chemicals with a wide range of log Kow (2.73-4.80) and including emerging contaminants was established, which shows further utilization for predicting the sorption of organic contaminants by plants.

Uptake, translocation and metabolism of decabromodiphenyl ether (BDE-209) in seven aquatic plants

Terrestrial plant uptake of PBDEs from contaminated soils has been widely reported recently. In this study the fate of deca-BDE within a plant/PBDEs/aquatic environment system was investigated through simulated pot experiments. Accumulations of the total PBDEs and deca-BDE were observed in tissues of seven test aquatic plant species, namely Phragmites australis, Cyperus papyrus, Alternanthera philoxeroides, Colocasia esculenta, Scirpus validus, Acorus calamus and Oryza sativa. In all seven plants, O. sativa leads the uptake and accumulation both in the total PBDEs (444.8 ng g(-1)) and deca-BDE (368.0 ng g(-1)) in roots. Among the six common phytoremediation aquatic plants, A. calamus leads the uptake (236.2 ng g(-1)), and P. australis leads the translocation (Cshoot/Croot = 0.35), while A. philoxeroides (43.4%) and P. australis (80.0%) lead in the metabolism efficiencies in the root and shoot, respectively. The detection of seventeen lesser brominated PBDE congeners provided the debromination evidence, and the specific PBDEs profiles in test plant species indicated there is no common metabolic pattern. Furthermore, a relative high proportion of lesser brominated PBDE congeners in shoots suggested the possible metabolic difference between roots and shoots. Finally, a noticeable percentage of penta- and octa-BDE derived from deca-BDE also hint the ecological risk in deca-BDE use. This comparative research on the aquatic plants provide a broad vision on the understanding of plant/PBDEs/aquatic environment interaction system, and may be applied to remediate PBDEs in contaminated waters and sediments.

Could Uptake and Acropetal Translocation of PBDEs by Corn Be Enhanced Following Cu Exposure? Evidence from a Root Damage Experiment

Cocontamination by heavy metals and persistent organic pollutants (POPs) is ubiquitous in the environment. Fate of POPs within soil/water-plant system is a significant concern and an area where much uncertainty still exists when plants suffered cotoxicity from POPs and metals. This study investigated the fate of polybrominated diphenyl ethers (PBDEs) when copper (Cu) was present within the soil/water-plant system using pot and hydroponic experiments. The presence of Cu was found to induce damage to the root cell membranes of corn (Zea mays L. cv. Nongda 108) with increasing concentration in both shoots and roots. The PBDE congeners BDE209 and BDE47 in shoots were also enhanced with the increasing electrolytic leakage from root, attributed to Cu damage, and the highest shoot BDE209 and BDE47 levels were observed under the highest Cu dosage. In addition, positive correlations were observed between the PBDE content of corn shoots and the electrolytic leakage of corn roots. These results indicated that within a defective root system, more PBDEs will penetrate the roots and are acropetally translocated in the shoots. The potential ecological risk associated with the translocation and accumulation of POPs into plant shoots needs careful reconsideration in media cocontaminated with metals and POPs, whereas often ignored or underestimated in environmental risk assessments.

Phenols, flame retardants and phthalates in water and wastewater - a global problem

Organic pollutants in water and wastewater have been causing serious environmental problems. The arbitrary discharge of wastewater by industries, and handling, use, and disposal constitute a means by which phenols, flame retardants (FRs), phthalates (PAEs) and other toxic organic pollutants enter the ecosystem. Moreover, these organic pollutants are not completely removed during treatment processes and might be degraded into highly toxic derivatives, which has led to their occurrence in the environment. Phenols, FRs and PAEs are thus highly toxic, carcinogenic and mutagenic, and are capable of disrupting the endocrine system. Therefore, investigation to understand the sources, pathways, behavior, toxicity and exposure to phenols, FRs and PAEs in the environment is necessary. Formation of different by-products makes it difficult to compare the efficacy of the treatment processes, most especially when other organic matters are present. Hence, high levels of phenols, FRs and PAEs removal could be attained with in-line combined treatment processes.

Dynamics of brominated flame retardants removal in contaminated wastewater sewage sludge under anaerobic conditions

Disposal of solid waste to landfills from waste water sewage treatment plants (WWTPs) serves as a potential source of contamination by polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCD). Native microbial communities have been found to degrade a variety of xenobiotics, such as PBDEs and HBCDs. This study investigates the potential of autochthonous microflora to remove 11 PBDE congeners and HBCDs in waste water sludge under anaerobic conditions. Laboratory microcosms were constructed with sewage sludge from the WWTPs of Hradec Kralove and Brno. BDE 209 was detected as the prevailing congener in concentrations 685 and 1403 ng/g dw and the total amounts of 10 lower PBDEs (BDE 28, 47, 49, 66, 85, 99, 100, 153, 154, 183) were 605 and 205 ng/g dw in sludge from Hradec Kralove and Brno, respectively. The levels of HBCD were detected in both sludge lower than 24 ng/g dw. The experiment was carried out for 15 months. After three months of incubation, HBCD was completely degraded to below detection limits. In sewage from both WWTPs, the higher brominated DEs were removed faster than the lower brominated congeners. One exception was tri-BDE, which was degraded completely within 15 months of cultivation. A significant increase in congener tetra-BDE 49 concentrations was observed over the course of the experiment in all tested sewage. The relative distribution of individual congeners among all PBDEs changed after 15 months of the incubation in favour of lower brominated congeners. This indicates that debromination is the major mechanism of anaerobic biodegradation. Despite of the increase of BDE 49, the overall removal of all 11 PBDEs achieved the levels of 47.4 and 68.7% in samples from WWTPs Hradec Kralove and Brno, respectively.

Bioaccumulation and translocation of polyhalogenated compounds in rice (Oryza sativa L.) planted in paddy soil collected from an electronic waste recycling site, South China

The bioaccumulation and translocation of polyhalogenated compounds (PHCs) in rice planted in the paddy soils of an electronic waste (e-waste) recycling site were investigated, along with the effect of contaminated soils on rice growth. The PHCs included polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), decabromodiphenyl ethane (DBDPE), 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE), and dechlorane plus (DPs). The morphological development and all measured physiological parameters of rice plants except for peroxidase were significantly inhibited by e-waste contaminated soils. Specifically, soil-root bioaccumulation factors (RCFs) increased with increasing logarithm of octanol-water partition coefficient (logKow) for PCBs, but decreased for PBDEs. During translocation from root to stem, translocation factors (TFs) and logKow were positively correlated. However, the accumulation mechanism in the leaf was concentration-dependent. In the high concentration exposure group, translocation play more important role in determination PHCs burden in leaf than atmospheric uptake, with logTF (from stem to leaf) being positively correlated with logKow. In contrast, in the low exposure and control groups, logTF (from stem to leaf) was negatively correlated with logKow. In addition, Syn-DP was selectively accumulated in plant tissues. In conclusion, this study demonstrates that e-waste contaminated soils affect rice growth, revealed the rule of the bioaccumulation and translocation of PHCs in rice plants.

Polychlorinated biphenyls (PCBs) and polybrominated biphenyl ethers (PBDEs) in environmental samples from Ny-Ålesund and London Island, Svalbard, the Arctic

Polychlorinated biphenyls (PCBs) and polybrominated biphenyl ethers (PBDEs) were determined in environmental samples collected from Ny-Ålesund and London Island, Svalbard, the Arctic. Total PCB concentrations (∑25PCBs) varied from 0.57 to 2.52 ng g(-1) dry weight (dw) in soil, 0.30 to 1.16 ng g(-1) dw in plants and 0.56 to 0.98 ng g(-1) dw in reindeer dung. The non-Aroclor congener of CB-11 was predominant in most samples compared to other congeners, accounting for 16.0±9.8% to the ∑25PCBs. The ∑13PBDEs concentrations were 1.7-416, 36.7-495 and 28.1-104 pg g(-1) dw in soil, plants and reindeer dung, respectively. The signature of enantioselective biotransformation was observed in all samples for chiral CB-95, whereas in parts of samples for other chiral PCBs. Bioaccumulation factors (BAFs) in six plant species varied within individual contaminant congeners and plant species, with BAFs less than 1 for ∑PCBs and higher than 1 for ∑PBDEs. BAF values decreased with increasing soil concentrations, suggesting that high background levels in soil restricted the accumulation of these contaminants by plants.

Fate of flame retardants and the antimicrobial agent triclosan in planted and unplanted biosolid-amended soils

A comprehensive understanding of the fate of contaminant-laden biosolids is needed to fully evaluate the environmental impacts of biosolid land application. The present study examined the fate of several flame retardants and triclosan in biosolid-amended soil in a 90-d greenhouse experiment. Objectives included evaluating the persistence of these compounds in soil, their phytoaccumulation potential by alfalfa (Medicago sativa), and potential degradation reactions. Concentrations of the polybrominated diphenyl ether (PBDE) congeners BDE-47 and BDE-209 and the antimicrobial triclosan declined significantly over time in biosolid-amended soil planted with alfalfa and then reached a steady state by day 28. In contrast, no significant losses of those analytes were observed from soil in nonvegetated pots. The amount of an analyte lost from vegetated soil ranged from 43% for the flame retardant di(2-ethylhexyl)-2,3,4,5-tetrabromophthalate to 61% for triclosan and was significantly and negatively related to the log octanol-water partition coefficient. Alfalfa roots and shoots were monitored for the compounds, but no clear evidence of phytoaccumulation was observed. Methyl triclosan formation was observed in the biosolid-amended soils during the study period, indicating in situ biotransformation of triclosan. The present study demonstrates that, although they are highly recalcitrant, PBDEs, selected alternate brominated flame retardants, and triclosan are capable of undergoing dissipation from biosolid-amended soils in the presence of plants.

Brominated flame retardants and seafood safety: a review

Brominated flame retardants (BFRs), frequently applied to industrial and household products to make them less flammable, are highly persistent in the environment and cause multi-organ toxicity in human and wildlife. Based on the review of BFRs presence in seafood published from 2004 to 2014, it is clear that such pollutants are not ideally controlled as the surveys are too restricted, legislation inexistent for some classes, the analytical methodologies diversified, and several factors as food processing and eating habits are generally overlooked. Indeed, while a seafood rich diet presents plenty of nutritional benefits, it can also represent a potential source of these environmental contaminants. Since recent studies have shown that dietary intake constitutes a main route of human exposure to BFRs, it is of major importance to review and enhance these features, since seafood constitutes a chief pathway for human exposure and biomagnification of priority environmental contaminants. In particular, more objective studies focused on the variability factors behind contamination levels, and subsequent human exposure, are necessary to support the necessity for more restricted legislation worldwide.

Field study on the uptake and translocation of PBDEs by wheat (Triticum aestivum L.) in soils amended with sewage sludge

Field experiments were conducted to explore the effects of different sewage sludge amendment strategies on the accumulation and translocation of polybrominated diphenyl ethers (PBDEs) in soil-wheat systems. Two types of application methods (single or annual application) and four annual application rates (5, 10, 20, and 40 t ha(-1) year(-1)) were investigated. BDE 209 was detected in all of the sewage sludge amended soils and different parts of wheat plants collected from the contaminated soils. However, the other seven PBDE congeners (BDE 28, BDE 47, BDE 99, BDE 100, BDE 153, BDE 154, and BDE 183) were not detected or were only observed at very low levels. A single application of sewage sludge in large quantities would likely increase accumulation of BDE 209 in soil and its subsequent uptake and translocation by wheat. The concentrations of BDE 209 in soils, wheat roots and straws increased with the increasing sewage sludge application rate. There is a negative correlation between the root accumulation factors (the ratios of concentrations in wheat roots to those in soils) and soil total organic carbon (R(2)=0.84,P<0.05), demonstrating that the bioavailability of BDE 209 was controlled by the soil total organic carbon. BDE 209 concentrations in the grains from the sewage sludge amended soils were not significantly different from those of the control soils, suggesting that atmospheric deposition was the main source of BDE 209 detected in the grains.

Aerobic biodegradation of selected polybrominated diphenyl ethers (PBDEs) in wastewater sewage sludge

Due to widespread accumulation of polybrominated diphenyl ethers (PBDEs) in our surroundings, it is important to clarify their fate in the environment and the options of their elimination. The aim of this study was to monitor the biodegradation of the most frequent congeners (BDE 28, 47, 49, 66, 85, 99, 100, 153, 154, 183 and 209) under aerobic condition by indigenous microflora in 2 industrially contaminated sewage sludge samples. BDE 209 was detected as the predominating congener in concentrations 685 ng/g and 1403 ng/g dry weight in sewage sludge from WWTPs (waste water treatment plants) Hradec Kralove and Brno, respectively. The total amount of 10 lower PBDEs was 605 and 205 ng/g dry weight, respectively. The aerobic degradation was significantly enhanced by the addition of yeast extract and 4-bromobiphenyl. The total concentrations of all 11 PBDE congeners were lowered and their elimination was detected reaching 62–78% of their initial amounts after 11 months of cultivation. The degradation of most abundant congener BDE 209 followed the first-order kinetics with constant detected between 2.77 × 10(−3) d(−1) and 3.79 × 10−(3)d(−1) and the half-lives of BDE 209 degradation ranged between 6.0 and 8.2 months. This work clearly demonstrates that both lower brominated PBDEs as well as the major representative BDE 209 could be successfully removed from municipally contaminated sludge under aerobic conditions.

Co-Planting Cd Contaminated Field Using Hyperaccumulator Solanum Nigrum L. Through Interplant with Low Accumulation Welsh Onion

Monoculture and intercrop of hyperaccumulator Solanum nigrum L. with low accumulation Welsh onion Renbentieganchongwang were conducted. The results showed that the remove ratio of S. nigrum to Cd was about 7% in intercrop plot when top soil (0-20 cm) Cd concentration was 0.45-0.62 mg kg(-1), which did not significantly impact the yield of low accumulation Welsh onion compared to the monoculture. The consistency of remove ratio in practice and theory indicated the remediation of S. nigrum to Cd was significant. The Cd concentration and yield of Welsh onion were not affected by the growth of S. nigrum either in intercrop plot. The Cd concentration in edible parts of Welsh onion was available either. In short, inter-planting hyperaccumulator with low accumulation crop could normally remediate contaminated soil and produce crop (obtain economic benefit), which may be one practical pathway of phytoremediating heavy metal contaminated soil in the future.

Endophytic bacteria: prospects and applications for the phytoremediation of organic pollutants

Recently, there has been an increased effort to enhance the efficacy of phytoremediation of contaminated environments by exploiting plant-microbe interactions. The combined use of plants and endophytic bacteria is an emerging approach for the clean-up of soil and water polluted with organic compounds. In plant-endophyte partnerships, plants provide the habitat as well as nutrients to their associated endophytic bacteria. In response, endophytic bacteria with appropriate degradation pathways and metabolic activities enhance degradation of organic pollutants, and diminish phytotoxicity and evapotranspiration of organic pollutants. Moreover, endophytic bacteria possessing plant growth-promoting activities enhance the plant's adaptation and growth in soil and water contaminated with organic pollutants. Overall, the application of endophytic bacteria gives new insights into novel protocols to improve phytoremediation efficiency. However, successful application of plant-endophyte partnerships for the clean-up of an environment contaminated with organic compounds depends on the abundance and activity of the degrading endophyte in different plant compartments. Although many endophytic bacteria have the potential to degrade organic pollutants and improve plant growth, their contribution to enhance phytoremediation efficiency is still underestimated. A better knowledge of plant-endophyte interactions could be utilized to increase the remediation of polluted soil environments and to protect the foodstuff by decreasing agrochemical residues in food crops.

Polybrominated diphenyl ether accumulation in an agricultural soil ecosystem receiving wastewater sludge amendments

Few studies have addressed bioaccumulation of organic pollutants associated with land-application of biosolids. We thus examined PBDE burdens within a soil ecosystem receiving long-term sludge amendments and a reference soil ecosystem receiving only manure inputs. No PBDEs were detected in reference site samples, but sludge-amended soils contained 17 600 ± 2330 μg/kg ∑3-7PBDE (total organic carbon (TOC) basis). ∑3-7PBDE burdens were highest in soil invertebrates with the greatest contact with sludge-amended soil (e.g., ∑3-7PBDE of 10 300 ± 2670 and 3000 ± 200 μg/kg lipid for earthworms and detritivorous woodlice, respectively). PBDEs were below quantitation limits in vegetation from the sludge-amended site. Surprisingly, we measured quantifiable PBDE burdens in only a single sample of predaceous ground spiders from the sludge-amended site. BDE-209 burdens in sludge-amended soil and earthworms were 7500 ± 2800 μg/kg TOC and 6500 ± 4100 μg/kg lipid, respectively. BDE 209 was detected in fewer taxa, but the burden in a detritivorous millipede composite was high (86 000 μg/kg lipid). PBDE congener patterns differed among species, with worms and ground beetles exhibiting Penta-BDE-like patterns. Penta-BDE biota-soil accumulation factors (BSAFs) ranged from 0.006 to 1.2, while BDE-209 BSAFs ranged from 0.07 to 10.5. δ(13)C and δ(15)N isotope signatures were poorly correlated with PBDE burdens, but sludge-amended samples were significantly δ(15)N enriched.

Congener-specific accumulation and environmental risk assessment of polybrominated diphenyl ethers in diverse Korean sewage sludge types

Industrial, domestic wastewater, and livestock sludge samples were collected from 23 wastewater treatment plants in Korea and analyzed for polybrominated diphenyl ethers (PBDEs). The concentrations of Σ19PBDE ranged from 4.01 to 10,400 ng/g dry weight. The average Σ19PBDE concentrations in industrial, domestic wastewater, and livestock sludge were 1,560 ± 3,610, 402 ± 148, and 27.6 ± 50.4 ng/g dry weight, respectively. The composition of PBDEs differed according to the type of sludge. Among the PBDE congeners, BDE 209 was dominant in all sludge samples. After BDE 209, relatively high levels were found for BDE 28 and 47 from industrial sludge, BDE 47 and 99 from domestic wastewater sludge, and BDE 206, 207, and 208 from livestock sludge. Using hierarchical cluster analysis, sludges were divided into three groups according to PBDE congener composition. A risk assessment of PBDEs in sludge used for soil amendment was carried out. Preliminary results indicated that the potential risk of soil exposed to PBDEs in sludge was relatively low.

Microcosm study on fate of polybrominated diphenyl ethers (PBDEs) in contaminated mangrove sediment

Polybrominated diphenyl ethers (PBDEs) are toxic and ubiquitous environmental contaminants, but their fate in aquatic environments is not clear. A mangrove microcosm study was employed to investigate the fate of two abundant congeners, BDE-47 and BDE-209, in contaminated sediment. After seven months, more than 90% of the spiked BDE-47 in the mangrove sediment was removed with the formation of lower brominated PBDEs, including BDE-28, -17, -15, -8, -7/4, suggesting that microbial debromination was the main contributor. Debromination of BDE-209 was also observed in the sediment but its dissipation rate was significantly lower than BDE-47. All these congeners were taken up, translocated and accumulated into the tissues of two typical mangrove plants, Kandelia obovata and Avicennia marina. PBDEs, even at very high contamination levels, in the sediment (5000ngg(-1)) and the debrominated congeners did not pose any adverse effect on the dry weight, augmentation and root/shoot ratio of either mangrove species. This is the first study to reveal that anaerobic microbial debromination and uptake by mangrove plants are the key processes controlling the fate of PBDEs in mangrove sediment.

BDE-154 induces mitochondrial permeability transition and impairs mitochondrial bioenergetics

Brominated flame retardants are used in various consumer goods to make these materials difficult to burn. Polybrominated diphenyl ethers (PBDE), which are representative of this class of retardants, consist of two benzene rings linked by an oxygen atom, and contain between 1 and 10 bromine atoms in their chemical structure, with the possibility of up to 209 different congeners. Among these congeners, BDE-154 (hexa-BDE) is persistent in the environment and easy to detect in the biota, but no apparent information regarding the mechanism underlying action and toxicity is available. Mitochondria, as the main energy-producing organelles, play an important role in the maintenance of various cellular functions. Therefore, mitochondria were used in the present study as an experimental model to determine the effects of BDE-154 congener at concentrations ranging from 0.1 μM to 50 μM. Our results demonstrated that BDE-154 interacts with the mitochondrial membrane, preferably by inserting into the hydrophobic core of the mitochondrial membrane, which partially inhibits respiration, dissipates Δψ, and permeabilizes the inner mitochondrial membrane to deplete ATP. These effects are more pronounced at concentrations equal to or higher than 10 μM. Results also showed that BDE-154 did not induce reactive oxygen species (ROS) accumulation within the mitochondria, indicating the absence of oxidative stress. Therefore, BDE-154 impairs mitochondrial bioenergetics and permeabilizes the mitochondrial membrane, potentially leading to cell death but not via mechanisms involving oxidative stress.