Transformation of 4-nonylphenol isomers during biosolids composting

New findings on the occurrence, removal, and risk assessment of nonylphenol and octylphenol in industrial wastewater treatment plants in Korea

Nonylphenol (NP) and octylphenol (OP), extensively used in industries, can disrupt the human endocrine system and cause significant ecological toxicity. Therefore, in this study, we aimed to reveal the occurrence and removal characteristics of NP and OP in 30 industrial wastewater treatment plants (IWWTPs). Specifically, this study focused on 13 NP isomers that have not been previously reported. Additionally, the potential environmental risk of NP and OP discharged from IWWTPs was assessed using a minimum dilution factor (MDF), proposed for the first time in this study. We showed that the concentration and proportion of the isomer NP11 were higher than those of the other isomers in the IWWTP influents and effluents. We also identified an activated sludge-activated carbon adsorption process suitable for removing NP and OP. Finally, we proposed the MDF value of 11 for the potential environmental risk assessment of NP and OP, revealing that OP poses a higher risk than NP when discharged into surface water. These findings underscore the importance of focusing on the isomer NP11 and OP in IWWTPs.

Structure–Biodegradability Relationship of Nonylphenol Isomers in Two Soils with Long-Term Reclaimed Water Irrigation

Nonylphenol (NP), as one of the typical endocrine disrupter chemicals (EDCs), has a high detection concentration and frequency in reclaimed water. This research focused on the degradation of NP isomers in two typical reclaimed water irrigation fields in Daxing, China, and Florida, USA. The results showed that the half-lives of NP isomer degradation in the soil of China and Florida were 2.03–8.66 d and 5.16–11.83 d, respectively. The degradation of NP isomers was structure-specific. Isomers of NP5, NP2, NP11, and NP3 had the highest degradation rates in the two soils; NP12, NP7, and NP6 were the isomers with medium degradation rates; and NP4, NP1, NP10, NP9, and NP8 had the slowest degradation rates. Steric hindrance and mean information index for the magnitude of distance (IDWbar) were found to be the better indexes for measuring the degradation of NP isomers compared with the length of the side chain, the type of the substitute, and the molecular connectivity. This study offers insights into the characteristics of NP isomers and two reliable indicators for measuring the degradation of NP isomers, which could provide data support for the environmental fate and the health risk assessment of NP in the future.

Occurrence, potential ecological risks, and degradation of endocrine disrupter, nonylphenol, from the aqueous environment

Nonylphenol (NP) is considered a potential endocrine-disrupting chemical affecting humans and the environment. Due to widespread occurrence in the aquatic environment and neuro-, immuno, reproductive, and estrogenic effects, nonylphenol calls for considerable attention from the scientific community, researchers, government officials, and the public. It can persist in the environment, especially soil, for a long duration because of its high hydrophobic nature. Nonylphenol is incorporated into the water matrices via agricultural run-off, wastewater effluents, agricultural sources, and groundwater leakage from the soil. In this regard, assessment of the source, fate, toxic effect, and removal of nonylphenol seems a high-priority concern. Remediation of nonylphenol is possible through physicochemical and microbial methods. Microbial methods are widely used due to ecofriendly in nature. The microbial strains of the genera, Sphingomonas, Sphingobium, Pseudomonas, Pseudoxanthomonas, Thauera, Novosphingonium, Bacillus, Stenotrophomonas, Clostridium, Arthrobacter, Acidovorax, Maricurvus, Rhizobium, Corynebacterium, Rhodococcus, Burkholderia, Acinetobacter, Aspergillus, Pleurotus, Trametes, Clavariopsis, Candida, Phanerochaete, Bjerkandera, Mucor, Fusarium and Metarhizium have been reported for their potential role in the degradation of NP via its metabolic pathway. This study outlines the recent information on the occurrence, origin, and potential ecological and human-related risks of nonylphenol. The current development in the removal of nonylphenol from the environment using different methods is discussed. Despite the significant importance of nonylphenol and its effects on the environment, the number of studies in this area is limited. This review gives an in-depth understanding of NP occurrence, fate, toxicity, and remediation from the environments.

Reduced phytotoxicity of nonylphenol on tomato (Solanum lycopersicum L.) plants by earthworm casts

Concentrations as high as thousands of milligrams per kilogram (dry weight) of nonylphenol (NP), an endocrine-disrupting chemical of great concern, have been reported in soil. Soil is considered one of the primary pathways for exposure of crop plants to NP. However, there have been few studies on the toxicity of soil NP to crop plants, especially with comprehensive consideration of the application of organic fertiliser which is a common agricultural practice. In this study, tomato plants were grown in soils treated with NP in the presence and/or absence of earthworm casts (EWCs). After four weeks, we tested the physiological and biochemical responses (accumulative levels of hydrogen peroxide (H₂O₂) and superoxide anion radicals (O₂-·), total chlorophyll content, degree of membrane lipid peroxidation, activities of defence-related enzymes, and level of DNA damage) and the changes in plant growth (elongation and biomass). The growth inhibition, reactive oxygen species (H₂O₂ and O₂-·) accumulation, decrease in chlorophyll content, increase in activity of defence-related enzymes (including superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, glutathione S-transferase and glutathione reductase), enhancement of membrane lipid peroxidation, and DNA damage in NP-treated seedlings were clearly reversed by the intervention of EWCs. In particular, the suppressed elongation, biomass, and chlorophyll content in tomato plants exposed to NP alone were significantly restored by EWCs to even greater levels than those of the undisturbed control. In other words, EWCs could efficiently invigorate the photosynthesis of crops via up-regulating the chlorophyll content, thereby overwhelming the NP stress on plant growth. Accordingly, except for reducing the bioavailability of soil NP as reported in our previous study, EWCs could also help crop plants to cope with NP stress by strengthening their stress resistance ability. Our findings are of practical significance for the formulation of strategies to relieve the negative effects of soil NP on crop growth.

Degradation and transformation of nitrated nonylphenol isomers in activated sludge under nitrifying and heterotrophic conditions

Nitrated nonylphenols (2-nitro-nonylphenols, NNPs) are metabolites of the endocrine-disrupter nonylphenols (NPs). While they have been detected in the environment, their fate in activated sludge has yet to be determined. In this study, we used synthesized NNP isomers and a ¹⁴C-tracer technique to study the degradation and transformation of four NNP isomers (NNP₁₁₁, NNP₁₁₂, NNP₃₈, and NNP₆₅) in nitrifying activated sludge (NAS) and heterotrophic bacteria-enhanced activated sludge (HAS). Our results showed that the degradation of NNPs in both NAS and HAS was isomer-specific. The half-lives of the NNPs decreased in the order: NNP₁₁₁ > NNP₁₁₂ > NNP₃₈ > NNP₆₅. After 36 days of incubation, 9.48 % and 4.01 % of the ¹⁴C-NNP₁₁₁ was mineralized in NAS and HAS, respectively. In addition to mineralization, five metabolites of NNPs containing hydroxyl, carbonyl, and carboxyl substituents on the alkyl chains were formed in NAS but not in HAS. The transformation of NNPs differed in NAS and HAS, mainly due to the differences in their microbial communities and the activities thereof in NAS and HAS. This is the first study of the isomer-specific fate of NNP isomers in activated sludge. Future studies should assess the toxicity, stability and potential risks of NNP metabolites in the environment.

Influence of the geophagous earthworm Aporrectodea sp. on fate of bisphenol A and a branched 4-nonylphenol isomer in soil

Large amounts of endocrine disrupting chemicals (EDCs) including bisphenol A (BPA) and nonylphenol (NP) are released into the soil due to the application of biosolids. Earthworms are the predominant biomass in many terrestrial ecosystems and profoundly influence the physico-chemical and biological properties of soils. However, information about the effects of earthworm activities on the behaviors of EDCs in soil is still limited. Here, the effects of earthworms on mineralization, degradation, and bound residue formation of BPA and NP were investigated using the ¹⁴C tracer technique. The results showed that earthworms did not affect mineralization of BPA, but significantly inhibited bound residue formation of BPA and changed the size distribution of BPA residues within humic substances. Regarding NP, earthworms significantly inhibited mineralization and bound residue formation, and thus significantly promoted the degradation of NP and NP's metabolites in soil. After nine days of incubation, 75% and 46% of the initially applied ¹⁴C-BPA and ¹⁴C-NP were already present in bound residues, respectively, indicating that the major route of degradation of BPA and NP in soil was bound-residue formation. Among total ¹⁴C-BPA or ¹⁴C-NP residues accumulated in earthworms, bound residues were also predominant (>50%), implying that risk assessment of EDCs based on their concentrations of free form in earthworms might be significantly underestimated. Taken together, our results suggest that fate of EDCs in soil not only depended on their physico-chemical properties but also was intensively affected by earthworm activities, underlining that effects of earthworms should be considered when evaluating environmental behavior and potential risk of EDCs in soil.

Nonylphenol causes shifts in microbial communities and nitrogen mineralization in soil microcosms

The aims of this work was to investigate, in soil microcosms, the effects on soil microbial community structure and function of increasing concentrations of 4-Nonylphenol (NP). The lasts is a product of degradation of NPEOs (Nonylphenol polyethoxylates) with a known toxic and estrogenic capacity able to disrupt animal's hormonal systems. The effect of increasing concentrations of NP (0, 10, 30, 90, and 270 mg NP kg^-1 of dry soil) in soil microcosms in three sampling dates (28, 56, and 112 days) over soil microbial activity and function were assessed. Soil microbial activity was estimated by microbial ATP content, and both bacterial and fungal communities composition were estimated using the terminal restriction fragment length polymorphism technique (T-RFLP). Abundance of ammonia-oxidizing bacteria (AOB) was estimated by qPCR of gene encoding for the bacterial ammonia-monoxygenase (amoA). Changes in biologically mediated soil properties were also assessed, namely water-soluble NH⁺₄, NO^-₂ and NO^-₃ content, the two last allowing the assessment of mineralization rates. NP-spiking had some unexpected impacts on microbial community structure and functions, since (i) impacted both bacterial and fungal communities structure at the highest NP concentration tested, bacterial communities were resistant to lower concentrations, while fungal communities were increasingly impacted until the end of the incubation at day 112; (ii) no community structure resilience was observed in bacteria at the highest NP concentration nor for fungi at any concentration; (iii) microbial activity decreased with NP after 28 and 56 d, but increased in the last sampling at the highest concentrations tests, coupled to an enrichment in AOB taxa after 56 and 112 days, that at least partly explain also explain the observed speed up of nitrification rates.

Accumulation and toxicological effects of nonylphenol in tomato (Solanum lycopersicum L) plants

Nonylphenol (NP) is one of the most worrisome and ubiquitous environmental endocrine disruptors. The tomato is one of the most important agricultural plants in the world. However, little is known about the toxicological effects of NP on tomato crops or the accommodative responses of tomato plants to NP stress. Thus, in this study, relevant tests were performed using pot experiments, and they indicated that when the NP concentration in the soil was elevated from 25 mg kg-1 to 400 mg kg-1, NP was progressively accumulated by the tomato plants. The NP induced growth inhibition and a declined in the total chlorophyll content, and it aggravated membrane lipid peroxidation in tomato plants. When confronted with NP stress, the tomato plants correspondingly induced their antioxidant enzymes via both molecular and protein pathways to relieve the NP-induced oxidative stress. All the above results would be illuminating for developing strategies to address NP-induced damage to agricultural output, food quality and public health.

Degradation of triclosan by environmental microbial consortia and by axenic cultures of microorganisms with concerns to wastewater treatment

Triclosan is an antimicrobial agent, which is widely used in personal care products including toothpaste, soaps, deodorants, plastics, and cosmetics. Widespread use of triclosan has resulted in its release into wastewater, surface water, and soils and has received considerable attention in the recent years. It has been reported that triclosan is detected in various environmental compartments. Toxicity studies have suggested its potential environmental impacts, especially to aquatic ecosystems. To date, removal of triclosan has attracted rising attention and biodegradation of triclosan in different systems, such as axenic cultures of microorganisms, full-scale WWTPs, activated sludge, sludge treatment systems, sludge-amended soils, and sediments has been described. In this study, an extensive literature survey was undertaken, to present the current knowledge of the biodegradation behavior of triclosan and highlights the removal and transformation processes to help understand and predict the environmental fate of triclosan. Experiments at from lab-scale to full-scale field studies are shown and discussed.

Effects of earthworm casts on sorption-desorption, degradation, and bioavailability of nonylphenol in soil

Up to hundreds of milligrams per kilogram (dry weight) of nonylphenol (NP) reportedly entered the soil and sediment through the agricultural reuse of biosolids, pesticide application, etc. Organic pollutants in soil could not only further trigger groundwater contamination via leaching (that highly depends upon sorption-desorption and degradation phenomena) but also harm food safety by crop uptake (that mainly rests with the bioavailability of pollutants in soil). Thus, we first investigated the effects of earthworm casts (EWCs) on the sorption-desorption, degradation, and bioavailability of NP in soil under laboratory microcosm conditions, and then, analyzed the FT-IR spectra of EWC and soil samples (with and without EWC). The application of EWC could notably increase the sorption capacity of soils for NP and in turn significantly inhibited the desorption of NP from soil; responsively lengthened the half-time of NP in the soil; and reduced the uptake and translocation of NP in tomato seedlings and promoted their growth during the first 3 weeks. Finally, FT-IR spectra of EWC and soil samples indicated that the application of EWC increased the content of N, P, and organic matter in soil.

Composting of 4-nonylphenol-contaminated river sediment with inocula of Phanerochaete chrysosporium

A composting study was performed to investigate the degradation of 4-nonylphenol (4-NP) in river sediment by inoculating Phanerochaete chrysosporium (Pc). Pc was inoculated into composting Reactor A, C and D, while Reactor B without inocula was used as control. The results showed that composting with Pc accelerated the degradation of 4-NP, increased the catalase and polyphenol oxidase enzyme activities in contaminated sediment. The dissipation half-life (t_1/2) of 4-NP in Reactor A, C and D with inocula of Pc were 2.079, 2.558, 2.424days, while in Reactor B without inocula of Pc it was 3.239days, respectively. Correlation analysis showed that the contents of 4-NP in sediment in Reactor A and D were negatively correlated with the actives of laccase, whereas no obvious correlation was observed in Reactor B and C. All these findings also indicated that Pc enhanced the maturity of compost, and the best composting C/N ratio was 25.46:1.

Degradation and toxicity reduction of the endocrine disruptors nonylphenol, 4-tert-octylphenol and 4-cumylphenol by the non-ligninolytic fungus Umbelopsis isabellina

Nonylphenol (NP), 4-tert-octylphenol (4-t-OP) and 4-cumylphenol (4-CP) are pollutants that are known as endocrine disruptors mainly due to their estrogen-mimicking activity. These phenolic substances are used in a wide range of industrial and commercial applications. In the present study, biodegradation of tNP, 4-t-OP and 4-CP using the non-ligninolytic fungus Umbelopsis isabellina was investigated. After 12h of incubation, more than 90% of initially applied tNP, 4-t-OP and 4-CP (25mgL(-1)) were eliminated. GC-MS analysis revealed several derivatives mainly (hydroxyalkyl)phenols. Moreover, xenobiotic biotransformation led to the formation of intermediates with less harmful effects than the parent compounds. For all xenobiotics, a decrease in growth medium toxicity was observed, using Artemia franciscana and Daphnia magna as bioindicators. The results indicate that U. isabellina has potential in the degradation and detoxification of contaminants with endocrine activity. Moreover, this is the first report demonstrating that a microorganism is capable of effective 4-CP elimination.

Trace organic contaminants in biosolids: Impact of conventional wastewater and sludge processing technologies and emerging alternatives

This paper critically reviews the fate of trace organic contaminants (TrOCs) in biosolids, with emphasis on identifying operation conditions that impact the accumulation of TrOCs in sludge during conventional wastewater and sludge treatment and assessing the technologies available for TrOC removal from biosolids. The fate of TrOCs during sludge thickening, stabilisation (e.g. aerobic digestion, anaerobic digestion, alkaline stabilisation, and composting), conditioning, and dewatering is elucidated. Operation pH, sludge retention time (SRT), and temperature have significant impact on the sorption and biodegradation of TrOCs in activated sludge that ends up in the sludge treatment line. Anaerobic digestion may exacerbate the estrogenicity of sludge due to bioconversion to more potent metabolites. Application of advanced oxidation or thermal pre-treatment may minimise TrOCs in biosolids by increasing the bioavailability of TrOCs, converting TrOCs into more biodegradable products, or inducing complete mineralisation of TrOCs. Treatment of sludge by bioaugmentation using various bacteria, yeast, or fungus has the potential to reduce TrOC levels in biosolids.

Impact of composting strategies on the degradation of nonylphenol in sewage sludge

Nonylphenol can be present in sewage sludge, and this can limit the use of the sewage sludge to amend soil. Composting is one of the most efficient and economical methods of making sewage sludge stable and harmless. The nonylphenol degradation rates during composting with added bulking agents and with aeration applied were studied. Three organic bulking agents (sawdust, corn stalk, and mushroom residue) were added to sewage sludge, and the effects of the bulking agents used and the amount added on nonylphenol degradation were determined. The highest apparent nonylphenol degradation rate (71.6%) was found for sewage sludge containing 20% mushroom residue. The lowest apparent nonylphenol degradation rate (22.5%) was found for sewage sludge containing 20% sawdust. The temperature of the composting pile of sewage sludge containing 20% sawdust became too high for nonylphenol to be efficiently degraded, and the apparent nonylphenol degradation rate was lower than was found for sewage sludge containing 10% sawdust. Increasing the ventilating time from 5 to 15 min increased the apparent nonylphenol degradation rate from 19.7 to 41.6%. Using appropriate aerobic conditions facilitates the degradation of nonylphenol in sewage sludge, decreasing the risks posed by sewage sludge applied to land. Adding too much of a bulking agent can decrease the amount of the nonylphenol degraded. Increasing the ventilating time and the amount of air supplied can increase the amount of nonylphenol degraded even if doing so causes the composting pile temperature to remain low.

Analysis, toxicity, occurrence and biodegradation of nonylphenol isomers: a review

Over the last two decades, nonylphenols (NPs) have become to be known as a priority hazardous substance due primarily to its estrogenicity and ubiquitous occurrence in the environment. Nonylphenols are commonly treated as a single compound in the evaluation of their environmental occurrence, fate and transport, treatment or toxicity. However, technical nonylphenols (tNPs) are in fact a mixture of more than 100 isomers and congeners. Recent studies showed that some of these isomers behaved significantly differently in occurrence, estrogenicity and biodegradability. The most estrogenic isomer was about 2 to 4 times more active than tNP. Moreover, the half lives of the most recalcitrant isomers were about 3 to 4 times as long as those of readily-biodegradable isomers. Negligence of NP's isomer specificity may result in inaccurate assessment of its ecological and health effects. In this review, we summarized the recent publications on the analysis, occurrence, toxicity and biodegradation of NP at the isomer level and highlighted future research needs to improve our understanding of isomer-specificity of NP.

Nonylphenol biodegradation in river sediment and associated shifts in community structures of bacteria and ammonia-oxidizing microorganisms

Nonylphenol (NP) is one of commonly detected contaminants in the environment. Biological degradation is mainly responsible for remediation of NP-contaminated site. Knowledge about the structure of NP-degrading microbial community is still very limited. Microcosms were constructed to investigate the structure of microbial community in NP-contaminated river sediment and its change with NP biodegradation. A high level of NP was significantly dissipated in 6-9 days. Bacteria and ammonia-oxidizing archaea (AOA) were more responsive to NP amendment compared to ammonia-oxidizing bacteria (AOB). Gammaproteobacteria, Alphaproteobacteria and Bacteroidetes were the largest bacterial groups in NP-degrading sediment. Microorganisms from bacterial genera Brevundimonas, Flavobacterium, Lysobacter and Rhodobacter might be involved in NP degradation in river sediment. This study provides some new insights towards NP biodegradation and microbial ecology in NP-contaminated environment.

Effects of the geophagous earthworm Metaphire guillelmi on sorption, mineralization, and bound-residue formation of 4-nonylphenol in an agricultural soil

Effects of earthworms on fate of nonylphenol (NP) are obscure. Using (14)C-4-NP111 as a representative, we studied the fate of 4-NP in an agricultural soil with or without the earthworm Metaphire guillelmi and in fresh cast of the earthworm. Sorption of 4-NP on the cast (Kd 1564) was significantly higher than on the parent soil (Kd 1474). Mineralization of 4-NP was significantly lower in the cast (13.2%) and the soil with earthworms (10.4%) than in the earthworm-free soil (16.0%). One nitro metabolite of 4-NP111 (2-nitro-4-NP111) was identified in the soil and cast, and the presence of the earthworm significantly decreased its amounts. The presence of earthworm also significantly decreased formation of bound residues of 4-NP in the soil. Our results demonstrate that earthworms could significantly change the fate of 4-NP, underlining that earthworm effects should be considered when evaluating behavior and risk of 4-NP in soil.

Degradation and bound-residue formation of nonylphenol in red soil and the effects of ammonium

Fate of nonylphenol (NP) in soils and the effects of nitrogen fertilizers are unclear. Using (14)C-tracer, we studied the aerobic and anaerobic degradation of 4-NP111 in a paddy red soil amended without and with ammonium chloride. Under oxic conditions, 4-NP111 had a half-life of 16.1 ± 1.6 days and minor mineralization (3.84 ± 0.02%), forming no extractable metabolite but abundant bound residues (60.9 ± 1.7%, mostly bound to humin) after 49 days of incubation. The ammonium amendment (8 mmol/kg soil) significantly inhibited the degradation (half-life of 68.0 ± 7.7 days), mineralization (2.0 ± 1.1%), and bound-residue formation (23.7 ± 0.2%). Under anoxic conditions, 4-NP111 did not degrade during 49 days of incubation and the ammonium amendment (40 mmol/kg soil) did not affect its persistence. Our results demonstrate that bound-residue formation was a major mechanism for NP dissipation in the red soil under oxic conditions and that chemical nitrogen fertilizer at average field application rate may already considerably increase NP recalcitrance in agricultural soils.

Fate of (14)C-organic pollutant residues in composted sludge after application to soil

Organic micropollutants may be present in biosolids, leading to soil contamination when they are recycled in agriculture. A sludge spiked with (14)C-labelled glyphosate (GLY), sodium linear dodecylbenzene sulphonate (LAS), fluoranthene (FLT) or 4-n-nonylphenol (NP) was composted with green waste and the fate of the (14)C-micropollutant residues remaining after composting was assessed after the compost application to the soil. (14)C-residues were mineralised in the soil and represented after 140d 20-32% of the initial activity for LAS, 16-25% for GLY, 6-9% for FLT and 4-7% for NP. The (14)C-residues at the end of composting that could not be extracted with methanol or ammonia were minimally remobilised or even increased for FLT. After 140d, non-extractable residues represented 38-52% of all of the (14)C-residues remaining in the soil for FLT, 50-67% for GLY, 91-92% for NP and 94-97% for LAS and in most cases, less than 1% of the (14)C-residues were water soluble, suggesting a low direct availability for leaching and microbial or plant assimilation. FLT was identified as the main compound among the methanol-extractable (14)C-residues that may be potentially available. The fate of the (14)C-organic pollutant residues in composts after application to soil could be assessed through a sequential chemical extraction scheme and depended on the chemical nature of the pollutant.

Dissipation pathways of organic pollutants during the composting of organic wastes

The organic pollutants (OPs) present in compostable organic residues can be recovered in the final composts leading to environmental impacts related to their use in agriculture. However, the composting process may contribute to their partial dissipation that is classically evaluated through the concentration decrease in extractable OPs, without identification of the responsible mechanisms as mineralization or stabilization of OP as non-extractable residues (NER) or bound residues. The dissipation of four (14)C-labeled OPs (fluoranthene; 4-n-nonylphenol, NP; sodium linear dodecylbenzene sulfonate, LAS; glyphosate) was assessed during composting of sewage sludge and green waste. The dissipation of LAS largely resulted from its mineralization (51% of initial LAS), whereas mineralization was intermediate for NP (29%) and glyphosate (24%), and negligible for fluoranthene. The NER pathway mostly concerned NP and glyphosate, with 45% and 37% of the recovered (14)C being found as NER at the end of composting, respectively. In the final composts, the proportions of water soluble residues of OPs considered as readily available were <11% of recovered (14)C-OPs. However, most fluoranthene remained solvent extractable (72%) and potentially available, whereas only 18% of glyphosate and less than 7% of both NP and LAS remained solvent extractable in the final compost.

The distribution of 4-nonylphenol in marine organisms of North American Pacific Coast estuaries

One of the chemical breakdown products of nonylphenol ethoxylates, 4-nonylphenol (4-NP), accumulates in organisms and is of concern as an environmental pollutant due to its endocrine disrupting effects. We measured 4-NP levels in the seawater, sediment, and twelve organisms within the California estuary, Morro Bay, and examined biomagnification of 4-NP using stable isotope abundances (δ(15)N and δ(13)C) to quantify trophic position. 4-NP concentrations in organisms from Morro Bay included 25000±8600 ng g(-1) lw in liver of California sea lion, 14000±5600 ng g(-1) lw in liver of harbor porpoise, 138000±55000 ng g(-1) lw in liver of sea otters, 15700±3600 ng g(-1) lw in liver of seabirds, 36100±6100 ng g(-1) lw in arrow goby fish, 62800±28400 ng g(-1) lw in oysters, and 12700±1300 ng g(-1) lw in mussels. 4-NP levels generally showed a pattern of trophic dilution among organisms in Morro Bay, with exceptions of biomagnification observed between three trophic links: mussel to sea otter (BMF 10.9), oyster to sea otter (BMF 2.2), and arrow goby to staghorn sculpin (BMF 2.7). Our examination of other west coast estuaries of USA and Canada revealed that mean 4-NP concentrations in gobies and mussels from Morro Bay were significantly higher than those from a more urbanized estuary, San Francisco Bay (goby: 11100±3800 ng g(-1) lw) and from a remote estuary, Bamfield Inlet, Canada (goby: 9000±900 ng g(-1) lw, mussel: 6100±700 ng g(-1) lw). Relative to other estuaries worldwide, 4-NP levels in seawater (0.42±0.16 μg L(-1)) and sediment (53±14 ng g(-1) dw) of Morro Bay are low, but gobies and oysters have higher 4-NP levels than comparable fauna.

Occurrence and biodegradation of nonylphenol in the environment

Nonylphenol (NP) is an ultimate degradation product of nonylphenol polyethoxylates (NPE) that is primarily used in cleaning and industrial processes. Its widespread use has led to the wide existence of NP in various environmental matrices, such as water, sediment, air and soil. NP can be decreased by biodegradation through the action of microorganisms under aerobic or anaerobic conditions. Half-lives of biodegradation ranged from a few days to almost one hundred days. The degradation rate for NP was influenced by temperature, pH and additions of yeast extracts, surfactants, aluminum sulfate, acetate, pyruvate, lactate, manganese dioxide, ferric chloride, sodium chloride, hydrogen peroxide, heavy metals, and phthalic acid esters. Although NP is present at low concentrations in the environment, as an endocrine disruptor the risks of long-term exposure to low concentrations remain largely unknown. This paper reviews the occurrence of NP in the environment and its aerobic and anaerobic biodegradation in natural environments and sewage treatment plants, which is essential for assessing the potential risk associated with low level exposure to NP and other endocrine disruptors.

Isomer-specific degradation of branched and linear 4-nonylphenol isomers in an oxic soil

Using (14)C- and (13)C-ring-labeling, degradation of five p-nonylphenol (4-NP) isomers including four branched (4-NP(38), 4-NP(65), 4-NP(111), and 4-NP(112)) and one linear (4-NP(1)) isomers in a rice paddy soil was studied under oxic conditions. Degradation followed an availability-adjusted first-order kinetics with the decreasing order of half-life 4-NP(111) (10.3 days) > 4-NP(112) (8.4 days) > 4-NP(65) (5.8 days) > 4-NP(38) (2.1 days) > 4-NP(1) (1.4 days), which is in agreement with the order of their reported estrogenicities. One metabolite of 4-NP(111) with less polarity than the parent compound occurred rapidly and remained stable in the soil. At the end of incubation (58 days), bound residues of 4-NP(111) amounted to 54% of the initially applied radioactivity and resided almost exclusively in the humin fraction of soil organic matter, in which chemically humin-bound residues increased over incubation. Our results indicate an increase of specific estrogenicity of the remaining 4-NPs in soil as a result of the isomer-specific degradation and therefore underline the importance of understanding the individual fate (including degradation, metabolism, and bound-residue formation) of isomers for risk assessment of 4-NPs in soil. 4-NP(1) should not be used as a representative of 4-NPs for studies on their environmental behavior.

Soil bioassays as tools for sludge compost quality assessment

Composting is a waste management technology that is becoming more widespread as a response to the increasing production of sewage sludge and the pressure for its reuse in soil. In this study, different bioassays (plant germination, earthworm survival, biomass and reproduction, and collembolan survival and reproduction) were assessed for their usefulness in the compost quality assessment. Compost samples, from two different composting plants, were taken along the composting process, which were characterized and submitted to bioassays (plant germination and collembolan and earthworm performance). Results from our study indicate that the noxious effects of some of the compost samples observed in bioassays are related to the low organic matter stability of composts and the enhanced release of decomposition endproducts, with the exception of earthworms, which are favored. Plant germination and collembolan reproduction inhibition was generally associated with uncomposted sludge, while earthworm total biomass and reproduction were enhanced by these materials. On the other hand, earthworm and collembolan survival were unaffected by the degree of composting of the wastes. However, this pattern was clear in one of the composting procedures assessed, but less in the other, where the release of decomposition endproducts was lower due to its higher stability, indicating the sensitivity and usefulness of bioassays for the quality assessment of composts.

Fate of endocrine-active compounds during municipal biosolids treatment: a review

For two decades, the fates of endocrine-disrupting compounds (EDCs) across various wastewater treatment processes have been studied using chemical and in vitro bioassay measurements. In comparison, little work has been conducted to track the fates of EDCs during municipal biosolids stabilization, particularly using bioassay approaches. This leads to knowledge gaps with respect to understanding which single or combined biosolid treatments facilitate EDC removal, and what the total endocrine-active potency of treated biosolids might be. These unknowns in turn heighten public opposition and distrust of biosolids reuse applications. This review aims to summarize what is currently known regarding EDC removal during commonly used full-scale biosolids treatment processes and highlights analytical challenges that are relevant when in vitro bioassays and chemical analyses are applied to biosolids samples.

Synthesis of defined endocrine-disrupting nonylphenol isomers for biological and environmental studies

Nonylphenols are very important environmentally relevant substances in the focus of the world-wide endocrine disrupter research for over 25 years. Thus, they are among the 10 priority hazardous substances of the new European Union Water Framework Directive. They consist of a very complex mixture of isomers representing therefore a multi-component problem like dioxins or PCBs. As estrogenic effect and degradation behavior in the environment of individual 4-nonylphenols are heavily dependent on the structure and bulkiness of the side chain, it is absolutely necessary to consider the nonylphenol problem from an isomer-specific viewpoint. Therefore a range of 28 differently branched nonylphenol isomers were synthesized for biological and environmental studies. Nonylphenols with a quaternary alpha-carbon, like 4-(1,1,3,4-tetramethylpentyl)phenol (4-NP(95)) and 4-(1-ethyl-1,3,3-trimethylbutyl)phenol (4-NP(170)), were obtained by Friedel-Crafts alkylation of anisole with tertiary nonyl bromides and demethylation with BI(3). Nonylphenols with a tertiary alpha-carbon, such as 4-(1,2-dimethylheptyl)phenol (4-NP(10)) and 4-(1,2,4-trimethylhexyl)phenol (4-NP(41)), were accessible via coupling of p-methoxyphenylmagnesium bromide with ketones. Nonylphenols bearing a quaternary beta-carbon, like 4-(2,2-dimethylheptyl)phenol (4-NP(15)) and 4-(1,2,2-trimethylhexyl)phenol (4-NP(39)), were synthesized starting from 4'-methoxyisobutyrophenone. The compounds were characterized by GC-MS and NMR-spectroscopy. The individual isomers were designated according to the Juelich Nomenclature.

Sorption and mineralization of organic pollutants during different stages of composting

The organic pollutant (OP) content is a key factor when determining compost quality. The OPs present in feedstock materials may either be degraded during composting or stabilized in the compost by sorption interactions with organic matter (OM), which may reduce the availability of OP to microorganism degradation. It is particularly important to identify the key stages during composting that are involved in OP mineralization so as to be able to optimize the composting process and determine whether OP sorption on OM is a limiting factor to OP mineralization. Four (14)C-labeled OPs were used during the study: a polycyclic aromatic hydrocarbon (fluoranthene), two surfactants (4-n-nonylphenol - NP and sodium linear dodecylbenzene sulfonate - LAS) and a herbicide (glyphosate). The potential for compost microflora to degrade OP, and compost sorption properties, were characterized at different stages of composting. The highest levels of LAS and glyphosate mineralization were found during the thermophilic stage, at the beginning of maturation for NP and at the end of maturation for fluoranthene. A specific microflora was probably involved in the biodegradation of fluoranthene while NP, LAS and glyphosate mineralization were linked to total microbial activity. OP sorption on compost was linked to their hydrophobicity, decreasing in the order: fluoranthene>NP>LAS>glyphosate. Moreover, sorption decreased as compost maturity increased, except for glyphosate. The sorption coefficients were positively correlated to mineralization kinetics parameters for NP, LAS and glyphosate, suggesting a positive effect of sorption on increasing mineralization rates.

Triclocarban, triclosan, polybrominated diphenyl ethers, and 4-nonylphenol in biosolids and in soil receiving 33-year biosolids application

Land application of biosolids is a common practice throughout the world. However, concerns continue to be raised about the safety of this practice, because biosolids may contain trace levels of organic contaminants. The present study evaluated the levels of triclocarban (TCC), triclosan (TCS), 4-nonylphenol (4-NP), and polybrominated diphenyl ethers (PBDEs) in biosolids from 16 wastewater treatment plants and in soils from field plots receiving annual applications of biosolids for 33 years. All of the four contaminants evaluated were detected in most of the biosolids at concentrations ranging from hundreds of microg/kg to over 1,000 mg/kg (dry wt basis). They were detected at microg/kg levels in the biosolids-amended soil, but their concentrations decreased sharply with increasing soil depth for 4-NP, PBDEs, and TCC, indicating limited soil leaching of those compounds. However, potential leaching of TCS in the biosolids-amended soils was observed. The levels of all four compounds in the surface soil increased with increasing biosolids application rate. Compared with the estimated 33-year cumulative input to the soil during the 33-year consecutive biosolids application, most of the PBDEs and a small percentage of 4-NP, TCC, and TCS remained in the top 120-cm soil layer. These observations suggest slow degradation of PBDEs but rapid transformation of 4-NP, TCC, and TCS in the biosolids-amended soils.

Isomer-specific determination of 4-nonylphenols using comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry

Technical nonylphenol (tNP), used for industrial production of nonylphenol polyethoxylate surfactants, is a complex mixture of C(3-10)-phenols. The major components, 4-nonylphenols, are weak endocrine disruptors whose estrogenicities vary according to the structure of the branched nonyl group. Thus, accurate risk assessment requires isomer-specific determination of 4-NPs. Comprehensive two-dimensional gas chromatography/time-of-flight mass spectrometry (GC x GC/ToFMS) was used to characterize tNP samples obtained from seven commercial suppliers. Under optimal chromatographic conditions, 153-204 alkylphenol peaks, 59-66 of which were identified as 4-NPs, were detected. The 4-NPs comprised approximately 86-94% of tNP, with 2-NPs and decylphenols making up approximately 2-9% and approximately 2-5%, respectively. The tNP products were analyzed for eight synthetic 4-NP isomers, and results were compared with published data based on GC/MS analysis. Significant differences were found among the products and between two samples from a single supplier. The enhanced resolution of GC x GC coupled with fast mass spectral data acquisition by ToFMS facilitated identification of all major 4-NP isomers and a number of previously unrecognized components. Analysis of tNP altered by the bacterium, Sphingobium xenophagum Bayram, revealed several persistent 4-NPs whose structures and estrogenicities are presently unknown. The potential of this technology for isomer-specific determination of 4-NP isomers in environmental matrices is demonstrated using samples of wastewater-contaminated groundwater and municipal wastewater.

Environmental fate of phenolic endocrine disruptors: field and laboratory studies

Alkylphenolic compounds derived from microbial degradation of non-ionic surfactants became a major focus of environmental research in the early 1980s. More toxic than the parent compounds and weakly oestrogenic, certain metabolites of nonylphenol polyethoxylate (NPnEO) surfactants, especially nonylphenol (NP), raised sustained concern over the risk they pose to the environment and triggered legal measures as well as partly voluntary actions by the manufacturing industry. Continuous progress in the development of analytical techniques is crucial to understand how these alkylphenolic compounds behave in wastewater treatment, the aquatic environment and in laboratory experiments. Measured concentrations and mass flows of phenolic endocrine disruptors, particularly nonylphenolic compounds, bisphenol A and parabens in municipal wastewater effluents and in the Glatt River, Switzerland, show that rain events leading to discharges of untreated wastewater into rivers have a great impact on the riverine mass flows of contaminants. Biotransformation experiments in our laboratory with nonylphenoxyacetic acid and individual NP isomers enabled the elucidation of degradation pathways of these compounds. The finding that nonylphenoxyacetic acid is metabolized via NP further underscores the role of NP as the most relevant metabolite in the degradation of NPnEO. Several Sphingomonadaceae bacterial strains were found to degrade alpha-quaternary 4-NP isomers by an ipso-substitution mechanism, and to use only the aromatic part of the molecule. These reactions turned out to be isomer specific, meaning that rate and extent of transformation depend on constitution, and possibly also on the absolute configuration of the alkyl side chain of a specific isomer. The observation that NP isomers with distinct oestrogenic activities are differentially degraded has significant implications for risk assessment.

Nonylphenol, octylphenol, and bisphenol-A in the aquatic environment: a review on occurrence, fate, and treatment

This paper reviews the current knowledge on the occurrence, biodegradation, and photooxidation of nonylphenol (NP), octylphenol (OP), and bisphenol-A (BPA) in aquatic environment. Generally, the concentrations determined were 0.006-32.8, < 0.001-1.44, and 0.0005-4.0 mu g L(-1) for NP, OP, and BPA respectively in river waters worldwide. Anthropogenic activities that can lead to run-off and storm water discharge may contribute to such concentrations in rivers. Pathways for biodegradation of NP and BPA appear to be similar. The influence of ferric ions, oxalate, hydrogen peroxide, and dissolved organic matter (DOM) on the photooxidation of NP and BPA in natural water is presented. Several techniques including nanofiltration, adsorption, sonochemical, photocatalytic, chlorination, ozonation, and ferrate(VI) oxidation for removals of NP, OP, and BPA are also reviewed.

Fate of 4-nonylphenol in a biosolids amended soil

The fate of the endocrine disrupting compound 4-nonylphenol (NP) in an agricultural soil amended with biosolids was assessed in a greenhouse study. A biosolids with a total NP concentration of 900 mg kg(-1) was incorporated into the 4 cm surface layer of soil columns at an agronomic rate equivalent to 1.7 kg m(2). Half of the columns were planted with Triticum aestivum L., red hardy winter wheat seeds, whereas the remaining columns were unplanted to evaluate the influence of plant growth on the fate of NP. The degradation of total NP and eight NP isomers was monitored over 45 d. The half-life of NP in this soil system ranged from 16 to 23 d depending on treatment. After 45 d from the start of the trail, 15% of the initial biosolids-NP remained in the planted columns, whereas approximately 30% remained in the unplanted columns, indicating enhanced degradation in the presence of plants. The eight NP isomers exhibited different degradation rates, but minimal amounts of all isomers persisted after 45 d. Movement of NP below the zone of incorporation was slight (<2% of total NP present at any sampling interval) and no NP was detected in column leachates or in wheat leaves.

Isomer-specific degradation and endocrine disrupting activity of nonylphenols

Degradation of technical nonylphenol by Sphingobium xenophagum Bayram led to a significant shift in the isomers composition of the mixture. By means of gas chromatography-mass spectrometry, we could observe a strong correlation between transformation of individual isomers and their alpha-substitution pattern, as expressed by their assignment to one of six mass spectrometric groups. As a rule, isomers with less bulkiness at the alpha-carbon and those with an optimally sized main alkyl chain (4-6 carbon atoms) were degraded more efficiently. By mass spectrometric analysis, we identified the two most recalcitrant main isomers of the technical mixture (Group 4) as 4-(1,2-dimethyl-1-propylbutyl)phenols (NP193a and NP193b), which are diastereomers with a bulky alpha-CH3, alpha-CH(CH3)C2H5 substitution. Our experiments with strain Bayram show that the selective enrichment of isomers with bulky alpha-substitutions observed in nonylphenol fingerprints of natural systems can be caused by microbial ipso-hydroxylation. Based on the yeast estrogen assay (YES), we established an estrogenicity ranking with a variety of single isomers and compared it to rankings obtained with different reporter cell systems. Structure-activity relationships derived from these data suggest that Group 4 isomers have a high estrogenic potency. This indicates a substantial risk that enrichment of highly estrogenic isomers during microbial degradation by ipso-substitution will increase the specific estrogenicity of aging material.