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Abstract Raising population, deteriorating environmental conditions and limiting natural resources to handle the key environmental health problems have critically affected human health and the environment. Policy makers and planners in Nepal are more concerned today than at any other time in the past about the deterioration of the environmental condition. Therefore, understanding the connection between pollution and human wellbeing is fundamental endeavors to control pollution exposures and secure human wellbeing. This ability is especially critical for countries like Nepal where the issues of environmental pollution have customarily taken a second place to request for economic development. In this study, spatial distribution and sources of 12 heavy metals (HMs) were investigated in surface soils (n = 24) and house dust (n = 24) from four major urban areas of Nepal in order to mark the pollution level. Additionally, a health risk was estimated to establish the link between HMs pollution and human health. Results showed that the median concentration of Ag, Cd, Co, Cr, Cu, Ni, Pb, Sb, Mn and Zn in soil and dust were 2–13 times greater than the background value. The As, Zn, Cu, Cd, and Pb showed a relatively higher spatial variability in soil and dust. Zn was the most abundant metal measured in dust and soil and accounted for 59% and 55% of ∑ 7 HMs, respectively. The HMs in soil and dust were poorly correlated with total organic carbon (TOC) and black carbon (BC), suggesting little or no influence on HMs contamination. Source analysis study indicated the distribution of Cr, Ni, Sb, Ag, Pb, Cu, and Zn in soil and dust are mainly affected by anthropogenic sources, particularly traffic emissions, industrial source, and domestic households materials, while Co, Fe, As, Mn and Cd were from natural sources. The estimated carcinogenic risk (CR) of HMs in soil and dust exceeded the acceptable level of human exposure, recommending significant CR to the local population. Graphical abstract Image 1 Highlights • Heavy metals concentration in dust was slightly higher than those in soil. • Zn was the most abundant metal measured both in dust and soil. • Majority of metals in both mediums were mainly affected by anthropogenic sources. • Co, Fe, As, Mn and Cd were mainly originated from natural sources. • The average cancer risk exceeded the acceptable level. [ABSTRACT FROM AUTHOR]

Black carbon (BC) is generated as a result of the pyrolysis of biomass and fossil fuels. Different approaches have been taken to analyse BC in the environment, including thermal, optical and chemical methods. The chemical approach which uses benzene polycarboxylic acids (BPCAs) as molecular markers of BC has gained popularity within the scientific community recently. These pyrogenic molecular markers can be used to reconstruct ancient fire history and human presence. Here we review the development of the BPCA protocols for the analysis of BC and the previous studies that have used these methods. Additionally, this review explores the biogeochemical factors that influence the content and composition of BPCAs, which in turn affect the sources attributed to BC. These factors include the generation temperature of char, photodegradation, biodegradation and the interference of non-pyrogenic organic matter (OM) in BPCA-BC analysis. Different combustion temperatures can yield charred BC with varying degrees of aromatic condensation throughout the BC continuum, while aged soot-BC undergoes photochemical degradation, causing the loss of its original condensed aromatic structure. Photodegradation reduces the degree of BC condensation by preferentially breaking down the most condensed forms, whereas biodegradation primarily mineralizes the smaller and more biolabile BC. Non-pyrogenic sources, such as humic acids (HAs), have been found to contribute up to 25% of BPCA-BC in soil, and their presence can lead to overestimations of BC. Future research should focus on calibrating contemporary BPCA protocols using known reference materials and investigating the role of non-pyrogenic OM in BPCA-BC analysis. [Display omitted] • The biogeochemical factors affecting BPCA-BC have been reviewed. • Combustion temperature, photo- and biodegradation affect BPCA composition. • BPCA production from plant parts and humic substances warrants further attention. • The study of the polyaromatic nature of environmental samples is recommended. [ABSTRACT FROM AUTHOR]

Abstract The status of seven currently used pesticides were assessed under the influence of soil parameters in surface soils of cash crop growing areas of Pakistan. Chlorpyrifos occurred in highest mean concentration (1.18 mg kg−1). Selected pesticides exhibited higher affinity towards both organic carbon and black carbon fractions. The δ 13C stable carbon isotopic fraction of inorganic carbon was also used as a tracer and disclosed high retention of total organic carbon in Swat and Swabi sites. Statistical analysis revealed that carbon storage was primarily influenced by altitude and temperature. Soil clay mineral oxides of aluminum and iron positively correlated with organic carbon and selected pesticides (chlorpyrifos and cyprodinil). Soil to plant bio-concentration ratios predicted heightened uptake of azinfos and diazinon in major cash crop bio mass. Occupational risk via soil ingestion expressed no significant threat to the farmer community. Graphical abstract Image 1 Highlights • Current-use pesticides status in soil for six cash crop growing areas of Pakistan. • TOC/BC levels in cash crop growing areas and their influential role in sorption of current-use pesticides. • Inspecting organic carbon distribution pattern using stable carbon isotope as a tracer. • Effect of clay minerals and climatic factors on organic carbon retention and pesticide sorption. [ABSTRACT FROM AUTHOR]

The interest in charcoal for agricultural use (biochar) has sharply increased in recent years. However, biochar can contain groups of compounds such as polycyclic aromatic hydrocarbons (PAHs) that are considered persistent pollutants, and are formed concomitantly with biochar during its production by pyrolysis. Soil samples were collected in three experimental areas at different intervals (1, 3, 5 or 6 years) after the application of 16 Mg ha −1 of biochar. The total concentrations of PAHs; benzo[ a ]pyrene; and the estimated total cancer risk in biochar treated plots were larger than found in the control ones, but they decreased over time, equaling the control values after three years in the high C content soil (11.2 g C kg −1 soil), or after six years in the low C content soil (6.8 g C kg −1 soil). Nevertheless, the sum of PAH concentrations found in the biochar amended plots, in the range of 15.80–39.40 ng g −1 , were around two orders of magnitude below the limits of prevention established by Brazilian legislation (8100 ng g −1 ) and some European regulations for soils (3000 ng g −1 ) and also lower than the observed in previous studies about biochar amended soils. Our results indicate that, under the conditions evaluated, the application of biochar to soil in the studied proportion (16 Mg ha −1 , every six years) is safe concerning soil contamination by PAHs. [ABSTRACT FROM AUTHOR]

Biochar effect on the potential mobility of dibutyl phthalate (DBP), cadmium (Cd), and lead (Pb) in co-contaminated soils is not well investigated. A laboratory leaching study was conducted to evaluate the effect of biochars derived from bamboo (BB) and pig (PB) on the leachability of DBP, Cd, and Pb through soil columns packed with two soils with low or high organic carbon content (LOC; 0.35% C: HOC; 2.24% C) and spiked with DBP, Cd, and Pb. Application of PB to the LOC soil significantly ( P  < 0.05) reduced the leaching loss by up to 88% for DBP, 38% for Cd, and 71% for Pb, whereas its impact was insignificant in the HOC soil. The higher efficacy of PB in reducing the leaching of DBP, Cd, and Pb in the LOC soil than that of BB might be related to PB's higher specific surface area, surface alkalinity, pH, and mineral contents compared to those of BB. Co-contamination of Cd and Pb enhanced leaching of DBP in the LOC soil treated with PB, possibly by competition for the sorption sites. Leaching of DBP, Cd, and Pb were significantly ( P  < 0.05) higher in the LOC soil than in the HOC soil. This study revealed that the effectiveness of biochars was dependent on the soil organic carbon content. Application of PB to the LOC soil was effective in reducing the leaching risk of DBP, Cd, and Pb. [ABSTRACT FROM AUTHOR]

Biochar (BC) and polymers are cost-effective additives for soil quality improvement and long-term sustainability. The additional use of the oyster shells (OS) powder in BC- or polymer-treated soils is recommended as a nutrient source, to enhance aggregation and to increase enzyme activities. The effects of soil treatments (i.e., BC (5 Mg ha −1 ) and polymers (biopolymer at 0.4 Mg ha −1 or polyacrylamide at 0.4 Mg ha −1 ) with or without the OS (1%)) on the short-term changes were evaluated based on a 30-day incubation experiment with respect to several variables (e.g., CO 2 release, NH 4 + and NO 3 − concentrations, aggregate-size classes, and enzyme activities in an agricultural Luvisol). The BC and BP with the addition of OS increased the portion of microaggregates (<0.25 mm) relative to the control soil without any additions, while PAM alone increased the portion of large macroaggregates (1–2 mm). Concentrations of NO 3 − also increased in soils treated with OS, OS + BC, and OS + BP as result of the increased chitinase and leucine aminopeptidase activities. The BC and BP when treated with the additional OS had significant short-term impacts on N mineralization without affecting C mineralization in soil. Consequently, the combination of BC or BP with OS was seen to accelerate N turnover without affecting C turnover (and related C losses) from soil. As such, the addition of these additives contributed considerably to the improvement of soil fertility and C sequestration. [ABSTRACT FROM AUTHOR]

Due to influence of wind patterns (monsoon and westerlies) and anthropogenic activities, lower stretch of Himalaya is at direct exposure to persistent organic pollutants (POPs). Current study was designed to monitor atmospheric concentrations of long lived organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) using polyurethane passive air sampling in the Lesser Himalayan Region (LHR) of Pakistan. Levels of ∑ HCHs, ∑ DDTs and ∑ PCBs were observed in a range between 3 and 210 pg m −3 , 0.75–67.1 pg m −3 and 8.49–458 pg m −3 , respectively. Though, air mass trajectories over LHR indicated long range transport as atmospheric source input which was further explained by Clausius–Clapeyron plots between ln P and inverse of temperature (1000/ T ; K ) where all OCPs and most of the PCBs have shown insignificant relationship ( r 2 = 5E-06–0.41; p -value = 0.06–0.995). However, local source emissions and valley transport may also implicate based on spatial distribution and altitudinal patterns. Additionally, soil-air partitioning of organochlorines was assessed using octanol-air partition ( K OA ) and black carbon-air partition ( K BC ) based models. Regression results indicated combined influence of both organic matter ( r 2 = 0.298–0.85) and black carbon ( r 2 = 0.31–0.86) via absorption and adsorption, respectively in soil-air partitioning of OCs in LHR. This paper sheds light on the atmospheric concentrations of OCs and help in better understanding of the processes involved in fate and transport of organic pollutants in Himalayan region. Further investigations are required to understand the role of carbon moieties in fate and transport of other groups of organic pollutants at higher altitudes of Himalayan region. [ABSTRACT FROM AUTHOR]

Urban public parks provide a recreational environment for residents, hence more and more citizens would spend time in parks, especially elderly and kids. Therefore, it is important to evaluate the quality of ecological environment inside parks. Therefore, this study conducted the first measurements in ten public parks of Shanghai to investigate heavy metals in air, soil and leaf, growth parameters of leaf, and ambient PM 2.5 and black carbon (BC) concentrations. Results showed Al and Mg appeared the highest in air. Cr, Cu, Mn and Zn were dominating in soil. Ca and Mg were much greater in leaves. It was concluded geographical locations were major reasons to explain the level of heavy metals, which mainly came from vehicle emissions. A small portion was attributing to chemical industries nearby. PM 2.5 concentrations ranged from 0.01 mg/m 3 to 0.10 mg/m 3 , which met up level I and level II of air quality standard in China. BC concentrations ranged from 1000 ng/m 3 to 6000 ng/m 3 . Via comparing the correlation between photosynthesis and PM 2.5 , as well as chlorophyll content and PM 2.5 , it was concluded that chlorophyll can be regarded as an indicator for assessing air quality, but not photosynthesis. Unexpectedly, a positive correlation was observed between the stomatal conductance and PM 2.5 as well as BC, which might be attributed to plants resisting the ambient stress. The results of this study can be used for assessments of air quality and health exposure inside parks, and also could provide urban policy maker with scientific evidences for urban park planning. [ABSTRACT FROM AUTHOR]

Air pollution is a complex mixture of gases and particulate matter (PM) with local and non-local emission sources, resulting in spatiotemporal variability in concentrations and composition, and thus associated health risks. To study this in the greater Stockholm area, a yearlong monitoring campaign with in situ measurements of PM 10 , PM 1 , black carbon, NO x , O 3 , and PM 10 -sampling was performed. The locations included an Urban and a Rural background site and a Highway site. Chemical analysis of PM 10 was performed to quantify monthly levels of polycyclic aromatic compounds (PACs), which together with other air pollution data were used for source apportionment and health risk assessment. Organic extracts from PM 10 were tested for oxidative potential in human bronchial epithelial cells. Strong seasonal patterns were found for most air pollutants including PACs, with higher levels during the winter months than summer e.g., highest levels of PM 10 were detected in March at the Highway site (33.2 μg/m3) and lowest in May at the Rural site (3.6 μg/m3). In general, air pollutant levels at the sites were in the order Highway > Urban > Rural. Multivariate analysis identified several polar PACs, including 6 H -Benzo[ cd ]pyren-6-one, as possible discriminatory markers for these sites. The main sources of particulate pollution for all sites were vehicle exhaust and biomass burning emissions, although diesel exhaust was an important source at the Highway site. In vitro results agreed with air pollutant levels, with higher oxidative potential from the winter samples. Estimated lung cancer cases were in the order PM 10 > NO 2 > PACs for all sites, and with less evident seasonal differences than in vitro results. In conclusion, our study presents novel seasonal data for many PACs together with air pollutants more traditionally included in air quality monitoring. Moreover, seasonal differences in air pollutant levels correlated with differences in toxicity in vitro. [Display omitted] • PM, gases, and PACs were determined over 1 year at three sites. • Strong seasonal patterns were found for most air pollutants including PM 10 and PACs. • Specific polar PACs were identified as discriminatory markers for the sites. • Vehicle emissions and biomass combustion were the major sources of PACs. • Seasonal differences in PAC levels correlated with oxidative potential in vitro. [ABSTRACT FROM AUTHOR]

Spheroidal carbonaceous particles (SCPs) are atmospherically mobile by-products of anthropogenic, high-temperature fossil fuel combustion. Since they are preserved in many geologic archives across the globe, SCPs have been identified as a potential marker for the onset of the Anthropocene. Our ability to reliably model the atmospheric dispersal of SCPs remains limited to coarse spatial scales (i.e., 102–103 km). We address this gap by developing the DiSCPersal model, a multi-iterative and kinematics-based model for dispersal of SCPs at local spatial scales (i.e., 10°–102 km). Although simple and limited by available measurements of SCPs, the model is nonetheless corroborated by empirical data of the spatial distribution of SCPs from Osaka, Japan. We find that particle diameter and injection height are the primary controls of dispersal distance, whereas particle density is of secondary importance. Further, stark differences in the modelled dispersal distances of SCPs between non-point vs. smokestack sources could explain the ambiguity of dispersal distances and the relative magnitude of long-range vs. localized sourcing of SCPs reported in the literature. This research underscores the need to incorporate understanding of the localized dispersal patterns of SCPs when interpreting their preservation in geologic archives. By extension, our findings have implications for the reliability of SCPs as a globally synchronous marker for the onset of the Anthropocene. [Display omitted] • We present the first model for local (∼10°–102 km) atmospheric dispersal of SCPs. • The model's efficacy is supported by environmental SCP data. • Particle size is the primary control of SCP dispersal distance. • Differences of non-point and smokestack sources could explain existing discrepancies. • Localized dispersal is important to understanding SCPs in sediments. [ABSTRACT FROM AUTHOR]

Epidemiological studies have showed an association between black carbon (BC) exposure and adverse health effects. This study intends to investigate the influence of oxidation processes in atmosphere on the initial cellular responses of BC. The changes of gene expressions induced by fresh BC (FBC) and ozone-oxidized BC (OBC) in human lung epithelial A549 cells were analyzed. And their toxic effects presented by viability, LDH release and DNA damage were compared. Totally 47, 000 genes in A549 cells were examined using Affymetrix Human U133 plus 2.0 chips. Some of the differentially expressed genes were verified by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The results showed that 1446 genes (including 756 up-regulated and 690 down-regulated) and 1594 genes (including 788 up-regulated and 806 down-regulated genes) were significantly changed by FBC and OBC respectively. Only 4 of 14 (FBC)/15 (OBC) oxidative stress related genes, up- or down-regulated by FBC and OBC, were identical; 13 of 29 (FBC)/31 (OBC) inflammation related genes, and 6 of 20 (FBC)/18 (OBC) autophagy related genes were identical. No obvious differences were observed between the toxic effects of FBC and OBC. The cytotoxicity of OBC and FBC in A549 cells is at least partially induced by oxidative stress and consequent inflammation or autophagy process. Previous studies indicated that OBC may be more toxic than FBC. However, our results suggested that FBC and OBC might lead to diverse toxic endpoints through activating different molecular pathways. [ABSTRACT FROM AUTHOR]

In this work, an innovative approach using biochar technology for hyperaccumulator disposal was developed and evaluated. The heavy metal enriched P. acinosa biomass (PBM) was pyrolyzed to produce biochar (PBC). Both PBM and PBC were characterized with X-ray diffraction (XRD) for crystal phases, scanning electron microscopy (SEM) for surface topography, and analyzed for elemental composition and mobility. The results revealed that whewellite, a dominant crystal form in biomass, was decomposed to calcite after pyrolysis. Elemental analysis indicated that 91–99% total non-volatile elements in the biomass were retained in the biochar. The toxicity characteristic leaching procedure (TCLP) results revealed that 94.6% and 0.15% of total Mn was extracted for biomass and biochar, respectively. This suggests that mobility and bioavailability of Mn in biochar was much lower relative to pristine biomass. Batch sorption experiment showed that excellent removal of aqueous silver, lead, cadmium, and copper ions can be achieved with PBC. Findings from this work indicated that biochar technology can provide a value-added solution for hyperaccumulator disposal. [ABSTRACT FROM AUTHOR]

This study evaluated the feasibility of using biochars produced from three types of crop residues for immobilizing Pb and As and their effects on the abundance of microbial community in contaminated lowland paddy (P-soil) and upland (U-soil) agricultural soils. Biochars were produced from umbrella tree [ Maesopsis eminii ] wood bark [WB], cocopeat [CP], and palm kernel shell [PKS] at 500 °C by slow pyrolysis at a heating rate of 10 °C min −1 . Soils were incubated with 5% (w w −1 ) biochars at 25 °C and 70% water holding capacity for 45 d. The biochar effects on metal immobilization were evaluated by sequential extraction of the treated soil, and the microbial community was determined by microbial fatty acid profiles and dehydrogenase activity. The addition of WB caused the largest decrease in Pb in the exchangeable fraction (P-soil: 77.7%, U-soil: 91.5%), followed by CP (P-soil: 67.1%, U-soil: 81.1%) and PKS (P-soil: 9.1%, U-soil: 20.0%) compared to that by the control. In contrast, the additions of WB and CP increased the exchangeable As in U-soil by 84.6% and 14.8%, respectively. Alkalinity and high phosphorous content of biochars might be attributed to the Pb immobilization and As mobilization, respectively. The silicon content in biochars is also an influencing factor in increasing the As mobility. However, no considerable effects of biochars on the microbial community abundance and dehydrogenase activity were found in both soils. [ABSTRACT FROM AUTHOR]

In order to determine the efficacy of vegetable waste and pine cone biochar for immobilization of metal/metalloid (lead and arsenic) and abundance of microbial community in different agricultural soils, we applied the biochar produced at two different temperatures to two contaminated soils. Biochar was produced by vegetable waste, pine cone, and their mixture (1:1 ww −1 ) at 200 °C (torrefied biomass) and 500 °C (biochar). Contaminated soils were incubated with 5% (ww −1 ) torrefied biomass or biochar. Sequential extraction, thermodynamic modeling, and scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy were used to evaluate the metal immobilization. Microbial communities were characterized by microbial fatty acid profiles and microbial activity was assessed by dehydrogenase activity. Vegetable waste and the mixture of vegetable waste and pine cone biochar exhibited greater ability for Pb immobilization than pine cone biochar and three torrefied biomass, and vegetable waste biochar was found to be most effective. However, torrefied biomass was most effective in increasing both microbial community and dehydrogenase activity. This study confirms that vegetable waste could be a vital biomass to produce biochar to immobilize Pb, and increase the microbial communities and enzyme activity in soils. Biomass and pyrolytic temperature were not found to be effective in the immobilization of As in this study. [ABSTRACT FROM AUTHOR]

Black carbon (BC) in fine particulate matter (PM 2.5 ) is an important air pollutant in a large area of China. We have reconstructed a 100-year-long history of BC deposition based on analyses of sediment samples in the coastal area of the Northern China Plain (NCP). During 1900–2010, the sedimentary BC concentrations at three cores increased from 0.2 to 1.3, from 0.2 to 2.3, and from 0.2 to 1.9 mg g −1 , and the ranges for the BC deposition fluxes were 0.1–4.7, 0.1–8.2, 0.2–7.4 g m −2 a −1 , suggesting the increase of ten times from the pre-industrial era. The BC deposition fluxes showed abrupt variation with two peaks in the 1970s and 2010s. Residential energy consumption and biomass burning (i.e., low-temperature combustion sources; thus, large-scale wildfires with high temperature may not be included) were responsible for the BC increase in the 1970s. Fossil fuel combustion generated by the industrial sectors, including industry, power plants, and transportation, was negligible before 1990 but significantly increased during 1990–2010. The historical increase in the BC deposition was accurately predicted by climate models, specifically the Coupled Model Intercomparison Project Phase 5 (CMIP5). However, the BC fluxes in the NCP sediments were an order of magnitude greater than those of the simulated depositions, suggesting an underestimation of the BC deposition in the severely polluted area in China. [ABSTRACT FROM AUTHOR]

PM 2.5 pollution has been alleviated significantly since implementing the Clean Air Action in China, whereas a concomitant increase in O 3 pollution has been observed. In the megacity of China, haze episodes can be aggravated by the interaction between aerosols and the planetary boundary layer (PBL). Such interactions have been largely investigated in the middle and upper PBL and less so near the ground. Here, using observations from the ground and in the PBL during summer, we find that haze pollution has decreased notably, but O 3 pollution has worsened in Nanjing. PM 2.5 , black carbon (BC), BC/PM 2.5 , O 3 and planetary boundary layer height (PBLH) changed at rates of −0.34 μg m−3·month−1, 13 ng m−3·month−1, 0.08%·month−1, -0.06 μg m−3·month−1 and 1.5 m month−1, respectively (3.5 m·month−1excluding data from 2020) during 2015–2020. The height of the lower boundary of the temperature inversion layer decreased first and then increased at a rate of 5.4 m month−1 between 2017 and 2020. As the PM 2.5 concentration has decreased by 42.4% over the last six years, aerosol extinction has weakened in the PBL. Subsequently, the solar radiation has strengthened near the ground, which is conducive to forming O 3 and is mainly concentrated between 0 and 600 m. Due to the heating effect of BC, which can increase the temperature near the ground, the lower boundary of the inversion layer has been elevated, which further mitigates and aggravates the haze and O 3 pollution, respectively. [Display omitted] • PM 2.5 and BC/PM 2.5 change −0.34 μg m−3·month−1 and 0.08%·month−1 during 2015–2020. • O 3 in PBL is mostly formed between the heights of 0–600 m. • Heating effect of BC increase T, bottom height of inversion layer (BHIL) elevates. • BHIL elevates mitigates and aggravates the haze and O 3 pollution, respectively. [ABSTRACT FROM AUTHOR]

In sediments several binding phases dictate the fate and bioavailability of organic contaminants. Black carbon (BC) has a high sorptive capacity for organic contaminants and can limit their bioavailability, while the fraction bound to organic carbon (OC) is considered to be readily desorbable and bioavailable. We investigated the bioavailability and mixture toxicity of sediment-associated contaminants by combining different extraction techniques with in vitro bioanalytical tools. Sediments from a harbour with high fraction of BC, and sediments from remote, agricultural and urban areas with lower BC were treated with exhaustive solvent extraction, Tenax extraction and passive sampling to estimate total, bioaccessible and bioavailable fractions, respectively. The extracts were characterized with cell-based bioassays that measure dioxin-like activity (AhR-CAFLUX) and the adaptive stress response to oxidative stress (AREc32). Resulting bioanalytical equivalents, which are effect-scaled concentrations, were applied in an effect-balance model, consistent with a mass balance-partitioning model for single chemicals. Sediments containing BC had most of the bioactivity associated to the BC fraction, while the OC fraction played a role for sediments with lower BC. As effect-based sediment-water distribution ratios demonstrated, most of the bioactivity in the AhR-CAFLUX was attributable to hydrophobic chemicals while more hydrophilic chemicals activated AREc32, even though bioanalytical equivalents in the aqueous phase remained negligible. This approach can be used to understand the fate and effects of mixtures of diverse organic contaminants in sediments that would not be possible if single chemicals were targeted by chemical analysis; and make informed risk-based decisions concerning the management of contaminated sediments. [ABSTRACT FROM AUTHOR]

Microbial degradation plays a crucial role in eliminating polybrominated diphenyl ethers (PBDEs) in environments. However, the microbial bioavailability of PBDEs in aquatic sediments is not well understood. In this work, the bioavailability of 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47), a typical PBDE congener, to PBDE-degrading microorganisms in natural sediments from six Chinese rivers under anaerobic conditions was investigated. The contents of black carbon (BC) and total organic carbon (TOC) in the six sediment samples were in the range of 0.025%–0.30% and 0.03%–3.38%, respectively. BDE-47 desorption from various sediments was fitted well with the first-order three-compartment desorption model. The desorbing fraction of sediment-associated BDE-47 at each desorption time interval exhibited a significant negative correlation with the BC content ( p < 0.01). In the sediments, the anaerobic debromination of BDE-47 by microorganisms underwent a stepwise debromination pathway generating mainly three lower brominated congeners (BDE-28, -17 and −4). The microbial debromination ratio of BDE-47 ranged from 4.21% to 7.89% in various sediments after 120 d incubation anaerobically, and it negatively correlated with the content of sediment BC significantly ( p < 0.01). However, the desorbing fraction and microbial debromination ratio of BDE-47 only showed weak correlations with the TOC content in sediments ( p > 0.05). Furthermore, there was a significant positive correlation of desorbing fraction of BDE-47 from sediments with its microbial debromination ratio ( p < 0.01) as well as with the level of its three lower brominated products ( p < 0.05) after the first 20 d incubation. This study suggests that the BDE-47 bioavailability to microorganisms in anaerobic river sediments is mainly influenced by the content of sediment BC which controls the desorbing fraction of sediment-associated BDE-47. [ABSTRACT FROM AUTHOR]

Organochlorine pesticides (OCPs) were investigated in passive air and soil samples from the catchment area of the Indus River, Pakistan. ∑ 15 OCPs ranged between 0.68 and 13.47 ng g −1 in soil and 375.1–1975 pg mˉ 3 in air. HCHs and DDTs were more prevalent in soil and air compartments. Composition profile indicated that β -HCH and p,p' -DDE were the dominant of all metabolites among HCHs and DDTs respectively. Moreover, f BC and f TOC were assessed and evaluated their potential role in the distribution status of OCPs. The f TOC and f BC ranged between 0.77 and 2.43 and 0.04–0.30% respectively in soil. Regression analysis showed the strong influence of f BC than f TOC on the distribution of OCPs in the Indus River catchment area soil. Equilibrium status was observed for β -HCH, δ -HCH, p,p' -DDD, o,p' -DDT, TC, HCB and Heptachlor with ff ranged between 0.3 and 0.59 while assessing the soil–air exchange of OCPs. [ABSTRACT FROM AUTHOR]

The use of biochar has been suggested as a means of remediating contaminated soil and water. The practical applications of conventional biochar for contaminant immobilization and removal however need further improvements. Hence, recent attention has focused on modification of biochar with novel structures and surface properties in order to improve its remediation efficacy and environmental benefits. Engineered/designer biochars are commonly used terms to indicate application-oriented, outcome-based biochar modification or synthesis. In recent years, biochar modifications involving various methods such as, acid treatment, base treatment, amination, surfactant modification, impregnation of mineral sorbents, steam activation and magnetic modification have been widely studied. This review summarizes and evaluates biochar modification methods, corresponding mechanisms, and their benefits for contaminant management in soil and water. Applicability and performance of modification methods depend on the type of contaminants (i.e., inorganic/organic, anionic/cationic, hydrophilic/hydrophobic, polar/non-polar), environmental conditions, remediation goals, and land use purpose. In general, modification to produce engineered/designer biochar is likely to enhance the sorption capacity of biochar and its potential applications for environmental remediation. [ABSTRACT FROM AUTHOR]

We monitored black carbon (BC) concentration for 6 months to understand the characteristics of atmospheric aerosols of an inland rural area in Korea. A multi-angle absorption photometer was used to continuously monitor the BC concentration, which was compared with elemental carbon (EC) concentration measured by an OC/EC Analyzer. For the atmospheric aerosols less than 10 μm, size distributions were measured using both an optical particle counter and a scanning mobility particle sizer. The diurnal variations for BC concentration show that the average BC concentration was 1.43 μg m −3 and exhibited peaks in the morning rush hours. However, the BC concentration measured at night from 20:00 to 08:00 was higher than that measured during the day. The reason why the BC concentration at night was higher would be partly due to the regional characteristics influenced by the combination of local fixed sources and traffic condition. It is suggested that the traffic and transporting of pollutants from the west influenced the increase in the BC concentration at inland rural area including fixed sources. [ABSTRACT FROM AUTHOR]

The objective of this work was to investigate the retention mechanisms of ammonium in aqueous solution by using progressively oxidized maple wood biochar at different pH values. Hydrogen peroxide was used to oxidize the biochar to pH values ranging from 8.1 to 3.7, with one set being adjusted to a pH of 7 afterwards. Oxidizing the biochars at their lowered pH did not increase their ability to adsorb ammonium. However, neutralizing the oxygen-containing surface functional groups on oxidized biochar to pH 7 increased ammonia adsorption two to three-fold for biochars originally at pH 3.7–6, but did not change adsorption of biochars oxidized to pH 7 and above. The adsorption characteristics of ammonium are well described by the Freundlich equation. Adsorption was not fully reversible in water, and less than 27% ammonium was desorbed in water in two consecutive steps than previously adsorbed, for biochars with a pH below 7, irrespective of oxidation. Recovery using an extraction with 2 M KCl increased from 34% to 99% of ammonium undesorbed by both preceding water extractions with increasing oxidation, largely irrespective of pH adjustment. Unrecovered ammonium in all extractions and residual biochar was negligible at high oxidation, but increased to 39% of initially adsorbed amounts at high pH, likely due to low amounts adsorbed and possible ammonia volatilization losses. [ABSTRACT FROM AUTHOR]

Molecular characterization of pyrogenic organic matter (PyOM) is of great interest to understand the formation and behavior of these increasingly abundant materials in the environment. Two molecular marker methods have often been used to characterize and trace PyOM: polycyclic aromatic hydrocarbon (PAH) and benzenepolycarboxylic acid (BPCA) analysis. Since both methods target pyrogenic polycyclic compounds, we investigated the linkages between the two approaches using chars that were produced under controlled conditions. Rye and maize straws and their analogues charred at 300, 400 and 500 °C, respectively, were thus analyzed with both methods. Moreover, we also measured BPCAs directly on the lipid extracts, on which PAHs were analyzed, and on the respective extraction residues, too. Both methods revealed important features of the chars, in particular the increasing degree of aromatic condensation with increasing highest heating temperature (HTT). The overlap between the two methods was identified in the lipid fraction, where the proportion of benzenetricarboxylic acids (B3CAs) correlated with PAH abundance. The results confirmed the validity and complementarity of the two molecular marker methods, which will likely continue to play a crucial role in PyOM research due to the recent developments of compound-specific PAH and BPCA stable carbon (δ 13 C) and radiocarbon ( 14 C) isotope methods. [ABSTRACT FROM AUTHOR]

Biochars are widely used in the remediation of Cd-contaminated soils. However, changes in the bacterial communities in the rhizosphere contaminated with Cd in response to biochar aging are poorly studied. Addressing this gap in knowledge is important to improving micro-ecological services on healthy growth of plants with mitigation strategies against Cd contamination. An aging experiment (270 days) was conducted with biochars derived from poultry litter and sugar-gum wood added to a Cd-contaminated acid soil. Bacterial communities in the rhizosphere of Brassica rapa and bulk soils were investigated after 1, 90 and 270 days of biochar aging. There was no significant difference (P > 0.05) in bacterial Shannon and Simpson indices between the control and biochar treatments. However, compared to the no-Cd control, the addition of Cd decreased the relative abundances of Firmicutes, Chloroflexi and Acidobacteriota but increased those of Actinobacteriota and Proteobacteria. Poultry-litter biochar had the largest effect on bacterial community composition, especially in the rhizosphere. Aging of poultry-litter biochar increased the abundance of Armatimonadota over time more than the sugar-gum-wood biochar, which was attributed to a lower pH and higher bioavailability of Cd in the sugar-gum-wood biochar treatment. The addition of poultry-litter biochar to the contaminated soil mitigated the bioaccumulation of Cd by increasing soil pH and restoring soil bacterial ecology in contaminated acid soils over time. [Display omitted] • Effects of biochar aging on rhizosphere bacterial community were examined. • Aging of poultry-litter biochar enhanced the growth of copiotrophs. • Aging of sugar-gum wood biochar increased the abundance of Actinobacteriota. • Poultry-litter biochar restored soil bacterial ecology in Cd-contaminated soils. [ABSTRACT FROM AUTHOR]

Particulate matter (PM) from automobile exhaust has drastic effects on human health. The enforcement of environmental laws has controlled vehicle emissions and reduced the total PM. However, another significant source of PM is debris from tire wear, break wear, and road wear. In particular, tire-wear particles (TWPs) are further fragmented into nanoparticles, similar to the PM x or black carbon (BC) sources. As approximately 30 wt% of carbon black (CB) is used as filler in tires, TWPs can fragment into free-bound nano-CB. This study evaluates the emission factors of BC from the ternary plots of PM x and BC to estimate the concentration of nano-CB in TWPs. Based on the emission factors of BC for TWP, approximately 500 monitoring data points were acquired at four different sites. Semi-closed sites in a field measurement test have 2.9–4.0 times larger BC concentration than open sites. The mass concentration of nano-CB evaluated with the BC data and emission factors at the open sites is 22.47–23.96 ng/m3, whereas that at the semi-closed sites is 66.32–90.33 ng/m3. Transmission electron microscopy analysis with scanning mobility particle sizer and selected-area electron diffraction reveals grape-like aggregated nanoparticles, which is considered as CB. To compare the effect of the washing out of airborne particulates by rain, further analysis is conducted on the interior and exterior of the tunnel on a rainy day. While the concentration of PMs was effectively reduced by rainfall, the amount of BC and CB in the interior of a tunnel was not changed. Namely, even under rainfall, nano-CB still exists in the tunnels and thus free-bound CB and nanoparticles released from TWP will be effected on the human health. [Display omitted] • Correlation between PM 10 , PM 2.5 , and black carbon (BC) was identified in situ. • New approach distinguishes between BC and carbon black (CB). • Open and semi-closed sites have 22.47–23.96 and 66.32–90.33 ng/m3 of nano-CB. • Rain cannot deposit nano-CB on the ground even in semi-closed sites. [ABSTRACT FROM AUTHOR]

Carbonaceous aerosol species, such as elemental carbon (EC), are important Short-Lived Climate Forcers (SLCFs), contributing to climate and health effects of air pollution. The quantification of carbonaceous aerosols has been conventionally carried out using active air sampling followed by various analytical techniques, such as thermal/thermal-optical analysis. Active sampling requires specific equipment and infrastructure with electricity and therefore may not be the best choice for studying carbonaceous aerosols at remote locations. Passive sampling on the other hand provides a simple and cost-effective alternative to study time-weighted temporal and spatial trends. For the first time in this study, we have developed a method to examine the viability of measuring EC using polyurethane foam passive air samplers (PUF-PAS) coupled with a thermal analysis, i.e., EnCan-Total-900 (ECT9). The method was found reproducible with coefficients of variation as low as 3% for EC measured in ambient passive samples. The method had relatively low background with EC levels in blanks being as low as 0.1% of those in deployed samples, allowing quantification within a wide range of concentrations. The results indicate a homogenous distribution of particles within the PUF-PAS substrate. EC concentrations measured with the passive method were not significantly different from those obtained from active samples at the study sites (p > 0.01). This proof of concept of the PUF-PAS method provides an opportunity to cost-effectively expand measurements of elemental carbon at the global scale, and could be further extended to include other carbonaceous aerosol species in the future. This helps address regional data gaps for improving uncertainties of SLCF impacts on global climate forcing and to inform policy decisions. [Display omitted] • New method to measure ambient elemental carbon using PUF-PAS. • Method features good reproducibility and low background contamination. • Distribution of elemental carbon within PUF-PAS was homogenous. • Elemental carbon concentrations from PUF-PAS were comparable to active samples. • Opportunity to expand measurements of elemental carbon globally. [ABSTRACT FROM AUTHOR]

Veterinary antibiotics are frequently detected in soils posing potential contamination of food crops. Sulfamethazine (SMT) uptake was investigated by lettuce (Lactuca sativa L.) grown in the soils treated with/without biochar derived from an invasive plant, burcucumber (Sicyos angulatus L.) (BBC700). Soils were contaminated with SMT at 5 and 50 mg kg-1, and treated with/without 5% BBC700 (w w-1). The lettuces were harvested after 5 weeks of cultivation and were analyzed for SMT by a high performance liquid chromatography-tandem mass spectrometry after solid-phase extraction. With 5% BBC700, the uptake of SMT was reduced by 86% in the soil spiked with 5 mg kg-1 SMT compared to the control whereas a 63% reduction was observed in the soil spiked with 50 mg kg-1 SMT. Application of BBC700, into soils effectively reduced the SMT uptake by lettuce. [ABSTRACT FROM AUTHOR]

Highlights: [•] Biochar (BC) amendment at rate <0.5% did not affect mineralization of 14C-catechol. [•] BC amendment significantly enhanced the 14C accumulation in earthworm body. [•] 14C-catecholic residues were stabilized in cast after gut passage of earthworms. [•] No additive or synergic effects of BC and earthworm on fate of catechol was found. [Copyright &y& Elsevier]

Highlights: [•] BC formation from open burning and controlled combustion are summarized. [•] Different sampling and measuring processes for open burning and controlled combustion are compared. [•] BC inventory prediction methods and results are reviewed. [•] Results of BC inventory estimation in China showed lower values than other researches. [Copyright &y& Elsevier]

Highlights: [•] This manuscript reviews recent findings published on biochar. [•] Physical architecture and composition of biochars are critical for soil and water remediation. [•] Sorption capacity depends on surface area, microporosity, and hydrophobicity of biochar. [•] Long-term effects of biochar on contaminant stability in soil should be investigated. [ABSTRACT FROM AUTHOR]

Highlights: [•] Mussel shell, cow bone and biochar immobilized Pb in soil of a small arms range. [•] Biochar significantly decreased both Pb and Sb phytoavailability. [•] Formation of Pb-phosphate by biochar resulted in decreased phytoavailability. [•] Biochar is a novel amendment for the remediation of soils contaminated with Pb and Sb. [ABSTRACT FROM AUTHOR]

Abstract: Three techniques were used to measure black carbon (BC) in samples from Chinese loess-paleosol sequences. The results obtained by (1) chemo-thermal oxidation (CTO, performed two ways), (2) acid dichromate oxidation (Cr2O7), and (3) thermal–optical reflectance (TOR) were intercompared because prior studies have shown that the methods can yield disparate results. BC concentrations did vary among the methods, most likely because they measured different components of the BC continuum, but the high-temperature BC (soot) determined by CTO was correlated with the BC and soot obtained by TOR. The CTO and TOR methods both yielded statistically significant linear relationships for loess and lake sediments that had incremental additions of a standard (SRM-1649a). The results also showed that charred material was more abundant in these test sediments than soot carbon. Data for BC in Luochuan loess generated using TOR showed a trend similar to that of magnetic susceptibility, that is, high BC and large susceptibilities during the last interglacial and low values for both variables in the last glacial. The results thus indicate that the TOR method is well suited for studies of sedimentary materials and that more biomass burned during the last interglacial than in the last glacial. [Copyright &y& Elsevier]

Abstract: We carried out an analysis of black carbon (BC) surface mass concentration, its radiative effects, and sources of origin in an urban atmosphere in east India, during winter season, through ground-based measurements and application of modelling tools. BC surface mass concentration exhibited diurnal variation with their higher values and a larger variability during evening to early morning hours than during daytime (1100–1600h, Local Time, LT) hours. Daytime mean surface BC mass concentration and BC mass fraction in total aerosol (size range 0.23–20μm) and in submicronic aerosol (size range 0.23–1μm) during the study period, corresponding to the well-mixed atmospheric layer were 11μgm−3, 3–10%, and 9–16% respectively. The mean BC optical depth (BC-AOD) and BC-AOD fraction at 0.5μm were estimated in an optical model as 0.11 and 13% respectively. Mean shortwave aerosol radiative forcing due to BC at top-of-atmosphere (TOA) during the study period was found to be +0.94Wm−2, which is about 59% the global mean radiative forcing due to carbon-dioxide gases. Estimates from BC simulations in a general circulation model showed BC surface concentration and BC optical depth in east India are primarily attributed to emissions from biofuel and fossil fuel combustion. Most of BC surface concentration (95%) and BC optical depth (60%) are contributed by emissions arising from the Indo-Gangetic plain (IGP) but there is a significant influence to BC columnar loading through elevated transport channels attributed mainly to emissions from open biomass burning from distant regions outside IGP. [Copyright &y& Elsevier]

Abstract: When applied to soils, it is unclear whether and how biochar can affect soil nutrients. This has implications both to the availability of nutrients to plants or microbes, as well as to the question of whether biochar soil amendment may enhance or reduce the leaching of nutrients. In this work, a range of laboratory experiments were conducted to determine the effect of biochar amendment on sorption and leaching of nitrate, ammonium, and phosphate in a sandy soil. A total of thirteen biochars were tested in laboratory sorption experiments and most of them showed little/no ability to sorb nitrate or phosphate. However, nine biochars could remove ammonium from aqueous solution. Biochars made from Brazilian pepperwood and peanut hull at 600°C (PH600 and BP600, respectively) were used in a column leaching experiment to assess their ability to hold nutrients in a sandy soil. The BP600 biochar effectively reduced the total amount of nitrate, ammonium, and phosphate in the leachates by 34.0%, 34.7%, and 20.6%, respectively, relative to the soil alone. The PH600 biochar also reduced the leaching of nitrate and ammonium by 34% and 14%, respectively, but caused additional phosphate release from the soil columns. These results indicate that the effect of biochar on the leaching of agricultural nutrients in soils is not uniform and varies by biochar and nutrient type. Therefore, the nutrient sorption characteristics of a biochar should be studied prior to its use in a particular soil amendment project. [Copyright &y& Elsevier]

Abstract: Understanding adsorption processes of butyltins (BTs) such as monobutyltin (MBT) and dibutyltin (DBT) by black carbons is important for the evaluation of BT exposure risks to organisms and humans. However, relevant knowledge is scarce. In this study, the acidity constants pK a,1 =2.3, pK a,2 =3.5 and pK a,3 =5.9 for MBT and pK a,1 =3.0 and pK a,2 =5.1 for DBT are estimated via potentiometric titration. Additionally, adsorption isotherms of BTs to a wheat charcoal were determined. The adsorption behavior was observed to be pH-dependent due to BT speciation and the pH-dependent surface charge of the charcoal. MBT adsorption to the charcoal decreases with increasing pH from 4 to 8, while the highest adsorption occurs at pH 6 for DBT. Adsorption of the BTs is successfully described in the pH range of 3–10 by using a newly developed pH-dependent Dual Langmuir model. The model has the potential to predict the interaction of BT species with charcoal, which can contribute to the risk assessments of BTs in the environment. [Copyright &y& Elsevier]

Abstract: The spatial distribution and potential source of polychlorinated biphenyls (PCBs) in surface sediments from Bering Sea, Chukchi Sea, and Canada Basin and the relationship between PCBs and sedimentary properties including grain size, water content, loss on ignition, total organic carbon, and black carbon were explored. ΣPCBs (the sum of the detected PCB congeners) concentrations fluctuated in the study area, ranging from 22–150, 60–640 and 24–600 pg g−1 dry weight for the Bering Sea, Chukchi Sea, and Canada Basin. A similar homologue pattern was observed at different locations, with tri-chlorinated PCBs being the dominant homologue, implying that the PCBs came mainly from the atmospheric transportation and deposition and ocean current transportation. No apparent co-relationships between PCB concentrations and sediment properties were obtained, indicating that the distribution of PCBs was not only controlled by their source, but also by the multi-factors such as atmospheric transport and depositing, mixing, partitioning and sorption in the water column and sediments. [Copyright &y& Elsevier]

Abstract: Qualitative identification of sorbed volatile organic compounds (VOCs) on biochar was conducted by headspace thermal desorption coupled to capillary gas chromatographic-mass spectrometry. VOCs may have a mechanistic role influencing plant and microbial responses to biochar amendments, since VOCs can directly inhibit/stimulate microbial and plant processes. Over 70 biochars encompassing a variety of parent feedstocks and manufacturing processes were evaluated and were observed to possess diverse sorbed VOC composition. There were over 140 individual chemical compounds thermally desorbed from some biochars, with hydrothermal carbonization (HTC) and fast pyrolysis biochars typically possessing the greatest number of sorbed volatiles. In contrast, gasification, thermal or chemical processed biochars, soil kiln mound, and open pit biochars possessed low to non-detectable levels of VOCs. Slow pyrolysis biochars were highly variable in terms of their sorbed VOC content. There were no clear feedstock dependencies to the sorbed VOC composition, suggesting a stronger linkage with biochar production conditions coupled to post-production handling and processing. Lower pyrolytic temperatures (⩽350°C) produced biochars with sorbed VOCs consisting of short carbon chain aldehydes, furans and ketones; elevated temperature biochars (>350°C) typically were dominated by sorbed aromatic compounds and longer carbon chain hydrocarbons. The presence of oxygen during pyrolysis also reduced sorbed VOCs. These compositional results suggest that sorbed VOCs are highly variable and that their chemical dissimilarity could play a role in the wide variety of plant and soil microbial responses to biochar soil amendment noted in the literature. This variability in VOC composition may argue for VOC characterization before land application to predict possible agroecosystem effects. [Copyright &y& Elsevier]

Abstract: Anhydrosugars, such as levoglucosan and its isomers (mannosan, galactosan), as well as the solvent-extractable lignin phenols (methoxylated phenols) are thermal degradation products of cellulose/hemicellulose and lignin, respectively. These two groups of biomarkers are often used as unique tracers of combusted biomass inputs in diverse environmental media. However, detailed characterization of the relative proportion and signatures of these compounds in highly heterogeneous plant-derived chars are still scarce. Here we conducted a systematic study to investigate the yields of solvent-extractable anhydrosugars and lignin phenols in 25 lab-made chars produced from different plant materials under different combustion conditions. Solvent-extractable anhydrosugars and lignin phenols were only observed in chars formed below 350°C and yields were variable across different combustion temperatures. The yields of mannosan (M) and galactosan (G) decreased more rapidly than those of levoglucosan (L) under increasing combustion severity (temperature and duration), resulting in variable L/M and L/(M+G) ratios, two diagnostic ratios often used for identification of combustion sources (e.g. hardwoods vs. softwoods vs. grasses). Our observations thus may provide an explanation for the wide ranges of values reported in the literature for these two ratios. On the other hand, the results of this study suggest that the ratios of the major solvent-extractable lignin phenols (vanillyls (V), syringyls (S), cinnamyls (C)) provide additional source reconstruction potential despite observed variations with combustion temperature. We thus propose using a property–property plot (L/M vs. S/V) as an improved means for source characterization of biomass combustion residues. The L/M–S/V plot has shown to be effective in environmental samples (soil organic matter, atmospheric aerosols) receiving substantial inputs of biomass combustion residues. [Copyright &y& Elsevier]

Abstract: PCDD/F and PCB field data (1041 samples) in five media (dissolved, suspended sediment, bed sediment, catfish, and blue crab) were studied to explore dual contaminant patterns in the Houston Ship Channel, Texas, USA. PCDD/Fs showed greater concentration than PCBs in suspended sediments while PCBs were higher in apparent dissolved (truly dissolved+DOC-associated), fish, and crab. PCDD/Fs at nearly all locations contributed more strongly to dioxin-like toxicity. The fraction of PCB TEQ was, however, enriched in biotic over abiotic media due in large part to the presence of PCB 126, which was mostly undetected in water and sediment and yet exhibited a BAF three times greater than 2,3,7,8-TCDD. Dissolved-suspended sediment and suspended-bed sediment relationships showed that (1) observed apparent dissolved concentration differences (as fraction of total water were mean 10% PCDD/Fs and 63% PCBs) can reasonably be explained by a four-phase partition model (truly dissolved, DOC-associated, suspended OC, and suspended BC) for PCBs but not for PCDD/Fs and (2) the contaminants behaved similarly in bed to suspended sediment concentration ratios (C bed/C susp) upstream of a major confluence but not downstream. PCA-cluster analysis pointed to the possibility that suspended sediment PCB contamination originates from resuspended bed sediment while PCDD/Fs in suspended sediment originates more probably from other sediment sources such as upstream wash load or air deposition. Finally, examinations of a congener marker ratio (PCB 209/206) seemed to indicate that a source of pure PCB 209 may exist in bed sediment near Patrick Bayou though the source was not completely localized. [Copyright &y& Elsevier]

Abstract: Floodplain soils containing elevated levels of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) were collected from several locations along the Tittabawassee River (Michigan, USA). The PCDD/F profiles of these soils exhibited distinct congener patterns consistent with byproducts from either chloralkali manufacturing or chlorophenols productions. Black carbon (BC) particles were isolated for the first time from floodplain soil impacted by PCDD/Fs. Petrographic analysis showed that BC particles, including coal, oxidized coal, metallurgical coke, depositional carbon, coal tar/pitch, cenosphere, and charcoal, comprised approximately 30% by volume of the organic fraction with size range of 250μm–2000μm from a typical floodplain soil. The BC particles with anthropogenic origin such as pitch and coke associated with the chloralkali production process served as both the source and subsequent transporter for the highly hydrophobic PCDD/Fs. These anthropogenic BC particles were enriched with high levels of PCDFs, containing approximately 1000-fold the concentration found in the bulk soil. The strong association of PCDD/Fs with anthropogenic BC directly impacts the physicochemical and biological availability thus the risk associated with these hydrophobic organochlorines in soils and sediments. [ABSTRACT FROM AUTHOR]

Abstract: The concentrations of black carbon (BC), total organic carbon (TOC) and polycyclic aromatic hydrocarbons (PAHs) have been determined in soils from urban and rural areas of Beijing. The rural area can be divided into plain and mountainous areas which are close to and relatively far from the urban area, respectively. Concentration of BC (5.83±3.05mgg−1) and BC/TOC concentration ratio (0.37±0.15) in Beijing’s urban soil are high compared with that in world background soils and rural soils of Beijing, suggesting the urban environment to be an essential source and sink of BC. Concentration of BC in the urban area decreases from the inner city to exterior areas, which correlates with the urbanization history of Beijing and infers accumulation of BC in old urban soils. Black carbon in Beijing soils mainly comes from fossil fuel combustion, especially traffic emission. Median PAH concentration in the urban area (502ngg−1) is one order of magnitude higher than that in the rural plain (148ngg−1) and mountainous area (146ngg−1) where PAHs are supposed to mainly come from atmospheric deposition from the urban area. Concentrations of BC correlate significantly with those of PAHs (p <0.01, except naphthalene) in the urban area and with those of heavier 4-, 5- and 6- ring PAHs (p <0.01) in the adjacent rural plain area, while there is no significant correlation with any PAH in the farther rural mountainous area. [ABSTRACT FROM AUTHOR]

Abstract: The effect of organic carbon (OC) and mineral surface on the sorption of polycyclic aromatic hydrocarbon (PAH) pyrene molecule to four Yangtze River sediments was investigated by sorption batch techniques using fluorescence spectroscopy. Pyrene sorption to the mineral fraction was estimated with model sorbent illite, the main clay mineral in Yangtze sediment. The Freundlich model fitted sorption to illite and to sediments was normalized to the specific surface area (SSA). Comparison of the SSA-normalized sorption capacities of illite and sediments suggests a negligible contribution of the pyrene sorption to the mineral fraction. In addition, composite models, such as the linear Langmuir model (LLM) and the linear Polanyi–Dubinin–Manes model (LPDMM) were applied for fitting the sorption of pyrene to the pristine sediments. The application of composite models allows assessing the partition of pyrene into amorphous organic carbon (AOC) and the adsorption in the porous structure of black carbon (BC). The modelling results indicate that the pyrene adsorption to the minor BC components (<0.2%) is more effective than the partition to AOC (0.5–1.3%). Besides the pristine sediments, sediments preheated at 375°C were also studied, in which the AOC fraction was removed during the preheating treatment. The modelling results with LPDMM and Polanyi–Dubinin–Manes model (PDMM) indicate a similar adsorption capacity of BC in pristine and preheated sediments, respectively. The low AOC concentrations in sediments do not diminish the BC micropore filling with pyrene. Simulation of pyrene distribution in the investigated Yangtze River sediments support the importance of the BC fraction in the PAH immobilization under environmental conditions. [Copyright &y& Elsevier]

Abstract: The development of phenanthrene catabolism in four soils amended with varying concentrations of activated charcoal (AC) (0%, 0.1%, 1% and 5%), a type of black carbon, was investigated. Mineralisation of 14C-phenanthrene was monitored after 1, 25, 50 and 100d soil-PAH contact time; lag phases, rates and extents of mineralisation of the 14C-phenanthrene to 14CO2 were determined. At concentrations >0.1% AC rates and extents of mineralisation were reduced by more than 99%. This revealed that the presence of >0.1% AC in soils may substantially diminish the rate at which the catabolic activity of indigenous soil microflora develops in contaminated soil. Soil C, which had the highest organic carbon (OC) content, consistently exhibited the highest extents of degradation. It is suggested that, in accordance with other researchers, OC may have blocked available phenanthrene sorption sites. This enhanced phenanthrene availability ultimately facilitated a greater level of catabolic activity within this soil. Such results reflect the complex nature of interactions between soil, biota and contaminants and their influence on the degradation of contaminants in the environment. [Copyright &y& Elsevier]

Abstract: Carbonaceous sorbents including black carbon (BC) and carbon nanotubes have attracted research attention around the world because of their effects on bioavailability of hydrophobic organic compounds (HOCs) in sediments and soils. In this research, 14C-labeled and unlabeled phenanthrene were spiked into three artificial sediments: (i) a sediment sample without amorphous organic carbon (OC) and with BC collected from the Yangtze River (BC-YR), (ii) a sediment without OC and with multi-walled carbon nanotubes (MWCNTs), and (iii) a sediment without OC and with fresh wood char. Biodegradation and mineralization of adsorbed phenanthrene by Agrobacterium and XAD-2 assisted abiotic desorption of adsorbed phenanthrene were studied. The results showed that microbes could utilize a fraction of adsorbed phenanthrene by BC and MWCNTs after aging for 21–40d. With aging for 28d, the biodegradation efficiencies of phenanthrene after incubation for 21d were 83.8%, 73.5% and 54.2% for BC-YR, char and MWCNTs, respectively; with aging for 40d, the mineralization rates of 14C-labeled phenanthrene after incubation for 25d were 38.3%, 25.1% and 24.6%, respectively. The desorption and biodegradation processes showed similar residual concentration of phenanthrene. However, the biodegradation rates were higher than the desorption rates during the fast biodegradation stage, suggesting that bacteria could promote desorption or access and utilize the sorbed phenanthrene. The biodegradation and mineralization efficiencies of phenanthrene associated with MWCNTs were significantly lower than with BC (p <0.01), implying adsorption by MWCNTs may lead to a greater decrease of HOCs bioavailability in the environment. [Copyright &y& Elsevier]

Abstract: Sorption of perfluorooctane sulfonate (PFOS) to oil and oil-derived black carbon (BC) from solutions varying in pH and [Ca2+] was investigated. Oil is a strong sorbent for PFOS, together with the independence of oil–water distribution coefficient (K oil) on solution parameters (pH values and [Ca2+]), suggesting that hydrophobic interactions of the hydrophobic moieties of PFOS with oil played a dominant role. BC sorption for PFOS is not stronger or more nonlinear than other natural organic carbon from solution in the case of 0.5mM [Ca2+] and pH 5.05, indicating that specific adsorption sites on BC were probably not fit for PFOS. However, both sorption capacity and nonlinearity of PFOS increased obviously with decreasing solution pH and increasing [Ca2+], resulting in the potential importance of BC at environmentally low PFOS level, from solution at high [Ca2+] or low pH. The role of BC in PFOS sorption was significantly influenced by environmental conditions and solute aqueous concentrations. [Copyright &y& Elsevier]

Abstract: We investigated the effectiveness of two types of biochars in reducing the bioavailability of two soil-applied insecticides (chlorpyrifos and carbofuran) to Spring onion (Allium cepa). The biochars prepared from the pyrolysis of Eucalyptus spp. wood chips at 450 and 850°C (BC850) were thoroughly mixed into the soil to achieve 0%, 0.1%, 0.5% and 1% by soil weight. A spring onion crop was grown for 5 wk in the biochar-amended soils spiked with 50mgkg−1 of each pesticide. The loss of both pesticides due to degradation and or sequestration in soils decreased significantly with increasing amounts of biochars in soil. Over 35 d, 86–88% of the pesticides were lost from the control soil, whereas it was only 51% of carbofuran and 44% of chlorpyrifos from the soil amended with 1.0% BC850. Despite greater persistence of the pesticide residues in biochar-amended soils, the plant uptake of pesticides decreased markedly with increasing biochar content of the soil. With 1% of BC850 soil amendment, the total plant residues for chlorpyrifos and carbofuran decreased to 10% and 25% of that in the control treatment, respectively. The BC850 was particularly effective in reducing phytoavailability of both pesticides from soil, due to its high affinity for and ability to sequester pesticide residues. [Copyright &y& Elsevier]

Black carbon (BC) is regarded as a chemically and biologically stable form of carbon and the changes of BC properties in nature are generally assumed to be minute. However, more and more observations have argued the inertness of BC. The objectives of this study were to characterize the changes of BC properties through ageing processes and to identify if these changes are associated with temperature. Our results showed that ageing of BC occurs over a temperature range from −22°C to 70°C within a short period of 12 months. The main changes of BC properties through ageing were found in elemental composition, surface chemistry, and adsorption properties, where the aged BCs were shown to have higher oxygen concentrations, surface acidity, and negative surface charge but lower C concentrations, pH, surface basicity, point of zero net charge, and also a lower adsorption capacity of hydroquinone, an allelopathic compound, than fresh BC. These ageing processes of BC were affected by temperature and changed over time, with higher temperature and longer incubation time enhancing BC ageing. Our results from a wide temperature range suggest that ageing of BC is likely to occur in any terrestrial regime and that the changes of BC properties through ageing should not be overlooked. [Copyright &y& Elsevier]

Black carbon in sediment, present natively or added as a treatment amendment in the form of activated carbon, reduces contaminant bioavailability. Field evaluation of activated carbon effectiveness in reducing contaminant bioavailability requires accurate methods to measure the amendment in sediments. The most commonly used method to separate black carbon from natural organic matter in soils and sediments is low temperature (375°C) thermal oxidation which resulted in significant losses of activated carbons. A method was developed to isolate activated carbon using a solution of concentrated sulfuric acid and potassium dichromate to oxidize the natural organic matter while preserving the activated carbon. The chemical oxidation method was applied to assess the delivery of activated carbon to sediments in a pilot-scale demonstration project carried out in Grasse River, NY. Using this method on sediment from the Grasse River, over 98% of the natural organic matter was removed while preserving at least 95% of the activated carbon. The method was also demonstrated on other carbonaceous geosorbents and native black carbon in several sediment samples. [Copyright &y& Elsevier]

We studied the influence of acid pretreatment on the effective distinction between elemental carbon (EC) and organic carbon (OC), and between char-EC and soot-EC. Though widely employed in the pretreatment of soils and sediments for EC quantification, the use of HCl, HF, and HNO3 could decrease soot thermal stability as acid remains, leading to an underestimation of soot-EC by thermal methods. We compared thermal optical reflectance (TOR) measurements of EC concentrations in char reference materials and in lacustrine and marine sediments following pretreatment with various acids. The results showed that pretreatment with 2M HCl, concentrated HNO3, 7M HNO3, and 1M HNO3 did not result in EC oxidation. However, hot concentrated HNO3 oxidized EC significantly, leading to lower concentrations of EC, char-EC and soot-EC. By comparing the removal of potentially interfering materials, which contain little fire-derived carbon, with different acid pretreatments, we recommend the HCl–HF–HCl and concentrated (not hot) HNO3–HF–HCl pretreatments for the determination of EC, char-EC, and soot-EC in soils and sediments using the TOR method. [Copyright &y& Elsevier]