Polybrominated diphenyl ethers (PBDEs) undergo debromination when they were exposed in zerovalent metal or bimetallic systems. Yet their debromination pathways and mechanisms in these systems were not well understood. Here we reported the debromination pathways of three BDE congeners (BDE-21, 25 and 29) by nano-zerovalent iron (n-ZVI). All these BDE congeners have three bromine substituents that were located in ortho-, meta- and para-positions. Results demonstrated that BDE-21, 25 and 29 preferentially debrominate meta-, ortho- and para-bromines, respectively, suggesting that bromine substituent at each position (i.e. ortho-, meta- or para-) of PBDEs can be preferentially removed. Singly occupied molecular orbitals of BDE anions are well correlated with their actual debromination pathways, which successfully explain why these BDE congeners exhibit certain debromination pathways in n-ZVI system. In addition, microscale zerovalent zinc (m-ZVZ), iron-based bimetals (Fe/Ag and Fe/Pd) were also used to debrominate PBDEs, with BDE-21 as target pollutant. We found that the debromination pathways of BDE-21 in m-ZVZ and Fe/Ag systems are the same to those in n-ZVI system, but were partially different from those in Fe/Pd systems. The debromination of BDE-21 in Pd-H2 system as well as the solvent kinetic isotope effect in single metal and bimetallic systems suggests that H atom transfer is the dominant mechanism in Fe/Pd system, while e-transfer is still the dominant mechanism in Fe/Ag system.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal).This article has been retracted at the request of the authors due to the results of a detailed investigation of the data quality conducted by the Central Analytical Laboratory (CAL) after relocation to the University of Wisconsin (UW) – Wisconsin State Laboratory of Hygiene. Using a subset of the 30 samples with the highest bromide ion (Br-) concentrations, the CAL at UW found 6 samples that could not be verified or were incorrect. Because the extent of the incorrect data is unknown, the NADP Executive Committee voted unanimously in May 2019 to discontinue public access to these data, and they decided to sequester all Br- data prior to June 2018. These issues were not obvious to the authors when the paper was written.The authors apologize for the inconvenience caused.

Reliable detection and attribution of changes in nitrogen (N) runoff from croplands are essential for designing efficient, sustainable N management strategies for future. Despite the recognition that excess N runoff poses a risk of aquatic eutrophication, large-scale, spatially detailed N runoff trends and their drivers remain poorly understood in China. Based on data comprising 535 site-years from 100 sites across China's croplands, we developed a data-driven upscaling model and a new simplified attribution approach to detect and attribute N runoff trends during the period of 1990–2012. Our results show that N runoff has increased by 46% for rice paddy fields and 31% for upland areas since 1990. However, we acknowledge that the upscaling model is subject to large uncertainties (20% and 40% as coefficient of variation of N runoff, respectively). At national scale, increased fertilizer application was identified as the most likely driver of the N runoff trend, while decreased irrigation levels offset to some extent the impact of fertilization increases. In southern China, the increasing trend of upland N runoff can be attributed to the growth in N runoff rates. Our results suggested that increased SOM led to the N runoff rate growth for uplands, but led to a decline for rice paddy fields. In combination, these results imply that improving management approaches for both N fertilizer use and irrigation is urgently required for mitigating agricultural N runoff in China.

Source samples including crustal dust, cement dust, coal combustion were sampled and ambient samples of PM₂.₅ and PM₁₀ were synchronously collected in Hefei from April to December 2014. The size distributions of the markers in the measured source profiles were incorporated into ME-2 solution to develop a new method, called the SDABB model (an advanced ABB three-way factor analysis model incorporating size distribution information). The performance of this model was investigated using three-way synthetic and ambient dataset. For the synthetic tests, the size distributions of markers estimated by the SDABB model were more consistent with true condition. The AAEs between estimated and observed contributions of the SDABB ranged from 15.2% to 29.0% for PM₁₀ and 19.9%–31.6% for PM₂.₅, which is lower than those of PMF2. For the ambient PM, six source categories were identified by SDABB for both sizes, although the profiles were different. The source contributions were sulphate (33.33% and 24.53%), nitrate and SOC (22.33% and 18.16%), coal combustion (19.01% and 18.23%), vehicular exhaust (12.99% and 12.07%), crustal dust (10.69% and 19.40%) and cement dust (1.65% and 5.39%) for PM₂.₅ and PM₁₀ respectively. In addition, the estimated ratios of Al, Si, Ti and Fe in CRD were 0.76, 0.84, 1.10 and 0.85; those of Al and Si in CC were 0.42 and 0.66; Ca and Si in CD were 0.95 and 1.10; NO₃⁻ and NH₄⁺ in nitrate were 1.11 and 1.01; and SO₄²⁻ and NH₄⁺ in sulphate were 0.96 and 1.16. These modeled ratios were consistent with the measured ratios. The size distribution of contributions also came close to reality. Thus, the advanced SDABB three-way model can better capture the characteristics of sources between sizes by effectively incorporating the size distributions of the markers as physical constraints.

The urbanization and industrialization of cities around the coastal region of the Bohai Sea have produced large amounts of sewage sludge from sewage treatment plants. Research on the biodegradation of nonylphenol (NP) and the influencing factors of such biodegradation during sewage sludge composting is important to control pollution caused by land application of sewage sludge. The present study investigated the effect of aeration on NP biodegradation and the microbe community during aerobic composting under two intermittent aeration treatments in a full-scale plant of sewage sludge, sawdust, and returned compost at a ratio of 6:3:1. The results showed that 65% of NP was biodegraded and that Bacillus was the dominant bacterial species in the mesophilic phase. The amount of NP biodegraded in the mesophilic phase was 68.3%, which accounted for 64.6% of the total amount of biodegraded NP. The amount of NP biodegraded under high-volume aeration was 19.6% higher than that under low-volume aeration. Bacillus was dominant for 60.9% of the composting period under high-volume aeration, compared to 22.7% dominance under low-volume aeration. In the thermophilic phase, high-volume aeration promoted the biodegradation of NP and Bacillus remained the dominant bacterial species. In the cooling and stable phases, the contents of NP underwent insignificant change while different dominant bacteria were observed in the two treatments. NP was mostly biodegraded by Bacillus, and the rate of biodegradation was significantly correlated with the abundance of Bacillus (r = 0.63, p < 0.05). Under aeration, Bacillus remained the dominant bacteria, especially in the thermal phase; this phenomenon possibly increased the biodegradation efficiency of NP. High-volume aeration accelerated the activity and prolonged the survival of Bacillus. The risk of organic pollution could be decreased prior to sewage sludge reuse in soil by adjusting the ventilation strategies of aerobic compost measurements.

The last decades have seen the increasing prevalence of thyroid disorders. These augmentations could be the consequence of the increasing contamination of the environment by chemicals that may disrupt the thyroid function. Indeed, in vitro studies have shown that many chemicals contaminating our environment and highlighted in human serum, are able to interfere with the thyroid function. Given the crucial importance of thyroid hormones on neurodevelopment in fetus and newborns, the influence of these pollutants on newborn thyroid homeostasis is a major health concern. Unfortunately, the overall evidence for a deleterious influence of environmental pollutants on thyroid remains poorly studied. Therefore, we assessed the contamination by polychlorinated biphenyls (PCBs), organochlorine pesticides and perfluorinated compounds (PFC) in 221 cord blood samples collected in Belgium between 2013 and 2016. Our results showed that compared to previous studies performed on newborns recruited in Belgium during the two last decades, the present pollutant contamination is declining. Multivariate statistical analyses pointed out a decrease of thyroid stimulating hormone (TSH) level in male newborns with detectable level of 4,4′- dichlorodiphenyldichloroethylene (4,4′-DDE) in comparison with those with no detectable level (p = 0.025). We also highlighted a negative association between perfluorononanoic acid (PFNA) concentration and TSH in male newborns (p = 0.018). Logistic regression showed increased odds ratio for presentation of hypothyroid in mother for each one unit augmentation of log natural concentration of PFOA (OR = 2.30, [1.18–4.5]) and PFOS (OR = 2.03 [1.08–3.83]). Our findings showed that the residual contamination by PFCs and organochlorine pollutants in cord blood are correlated with thyroid hormone in the newborns and the risk of hypothyroid in mothers.

Acceleration of Fe³⁺/Fe²⁺ cycle and simultaneous reduction of particle size with enhanced stability is extremely important for iron-based heterogeneous Fenton catalysts. In this work, Fe⁰-Fe₂O₃ composite nanoparticles embedded ordered mesoporous carbon hybrid materials (Fe⁰-Fe₂O₃/OMC) were rationally designed as efficient heterogeneous Fenton catalysts. Because of the confinement and reduction of OMC, highly dispersed Fe⁰-Fe₂O₃ active species with diameter of ∼8 nm were generated by an optimized carbothermic reduction process. In addition, Fe⁰-Fe₂O₃/OMC possesses ordered mesoporous structure with uniform mesopore, high surface area and pore volume. For comparison, two other catalysts, including solely Fe⁰ nanoparticles supported on ordered mesoporous carbon (Fe⁰/OMC) and solely Fe₂O₃ nanoparticles supported on ordered mesoporous carbon (Fe₂O₃/OMC) were also prepared. The Fenton catalytic performance of synthesized catalysts was evaluated by using H₂O₂ as oxidizing agent to degrade Acid Orange II (AOII). The results show that almost 98.1% of 100 mg L⁻¹ AOII was removed by Fe⁰-Fe₂O₃/OMC in condition of neutral pH and nearly room temperature, which is much higher than those of compared catalysts. The enhanced catalytic activity of Fe⁰-Fe₂O₃/OMC for AOII removal is due to the efficient electron transfer between the Fe⁰ and iron oxide and the accelerated Fe³⁺/Fe²⁺ cycle. The stability and reusability of the catalyst was also investigated, which showed a good performance even after five consecutive runs. The as-synthesized catalyst is proved to be an attractive candidate in heterogeneous Fenton chemistry and practical application.

Potentially toxic elements are widespread soil contaminants, whose occurrence could entail a concern for human health upon ingestion of fruit and vegetables harvested in a polluted area. This work set out to evaluate the concentrations of lead and cadmium as well as the levels of thirteen heavy metals for which a limit value is yet to be established by the food safety authorities, in order to perform a risk characterization related to the dietary intake of these metals and to provide a scientific opinion with wider relevance in the light of current worldwide regulatory issues. The sampling consisted of fruit and vegetables grown in a potentially contaminated area of southern Italy due to the illegal dump of hazardous wastes. An evaluation of the dietary exposure through the calculation of the Hazard Index (HI), the Maximum Cumulative Ratio (MCR) and the Target Cancer Risk (TCR) was adopted to this end. The results revealed that about the 30% of samples showed quantifiable levels of chemicals and no significant difference emerged between the potentially polluted area and the nearby cities that were selected as a control landfill site. The overall risk characterization for non-carcinogenic endpoints showed that the HI did not reach unsafe values, except for a small number of samples mainly because of aberrant occurrences and, in any case, the cumulative toxicity was mainly driven by thallium and vanadium. As far as the carcinogenic effects of arsenic are concerned, the distribution of TCR values broadly lay below the safety threshold; a certain percentage of data, however, exceeded this limit and should be taken into account for the enforcement of future regulatory thresholds.

Colloids are ubiquitous in soils, and it has been reported that colloids can act as carriers to increase the mobility of poorly soluble contaminants in subsurface environments. Addition of sulfur (S) fertilizer greatly influences on heavy metal behavior in paddy soil, while the influence of S fertilizer on Cu migration and transformation in colloids of soil pore water has not yet been studied. The influence of S fertilizer (S⁰ and Na₂SO₄) applied in paddy soils on Cu migration and transformation in colloids of soil pore water from the rice rhizosphere region was explored in this study. The speciation of Cu in colloids of soil pore water from the rice rhizosphere region was explored by advanced synchrotron-based X-ray absorption near-edge spectroscopy (XANES) techniques. The morphology of colloids was characterized by field emission scanning electron microscopy coupled to energy dispersive X-ray spectroscopy (SEM-EDX). At a depth of 20 cm, the concentration of Cu in colloids of the rhizosphere soil pore water in the control was 2.4- and 6.5- fold higher than that in treatments of S⁰ and Na₂SO₄, respectively. The colloids in soil pore water were all positively charged, ranging from 2.4 to 7.8 mV, and the size of colloids was 440–740 nm. The proportion of Fe in colloids in the rhizosphere region decreased with S fertilizer application, while the proportions of C and O increased. Sulfur fertilizer application, increased the proportion of Cu-Cysteine, while the proportion of Cu₂S decreased in soil colloids. In conclusion, application of sulfur fertilizer in paddy soil decreased the Cu concentration in soil pore water and colloids of the rhizosphere region, thereby decreasing the vertical migration of Cu in soil pore water.

Process-based models have been widely used for predicting environmental fate of contaminants. Nevertheless, accurate modeling of pentachlorophenol (PCP) dissipation in soils at the millimeter-scale remains a challenge due to the scarcity of observation data and uncertainty associated with model assumptions and estimation of the model parameters. To provide quantitative analysis of PCP-dissipation at the anaerobic/aerobic interface of a rhizobox experiment, this study implemented Bayesian parameter estimation for a process-based reactive chemical transport model. The model considered the main transport and transformation processes of chemicals including diffusion, sorption and degradation. The contributions of the processes to PCP dissipation were apportioned both in space and time. Using the maximum-a-posteriori (MAP) estimation of parameters, our model fitted the experimental data better compared with the previous work. Our results indicated that the most reactive zone for PCP dissipation occurred in the layer of 0–2.4 mm where degradation in solid phase dominated the PCP dissipation, while upward diffusion was the main mechanism for the reduction of PCP concentration in deeper layer (2.4–4.8 mm). By considering the coupled reactive transport of PCP and Cl⁻, the average degrees of PCP dechlorination in each layer were estimated from corresponding total concentrations of PCP and Cl⁻. The degrees of PCP dechlorination in the ponding water and the top layer of soil profile were highest, while 2,3,4,5- TeCP and 3,4,5- TCP were identified as the main dechlorination products in the soil. This study demonstrated that combining Bayesian estimation with process-based reactive chemical transport model can provide more insights of PCP dissipation at the millimeter-scale. This approach can help to understand complex dissipation mechanisms for other contaminants.