Polycyclic aromatic hydrocarbon occurrence in forest soils in response to fires: a summary across sites.

Forest fires are important sources of polycyclic aromatic hydrocarbons (PAHs) in soils. However, factors controlling PAH production in soils subjected to fires in different sites are poorly understood. Here, we analyzed 143 sets of previously published data to evaluate the concentrations and composition profiles of PAHs in ash and soils associated with forest fires and to assess the impacts of soil depth, fire intensity, post-fire duration, and vegetation type on their occurrence. Compared to unburned soils, the total PAH concentrations increased by 205% (95% confidential interval of 152-269%; n = 136) in soils associated with fires. This increase surpassed that of PAH toxic equivalents (73%) because fires produce dominantly low-ring PAHs with relatively low toxicity. PAH concentrations in fire-impacted sites increased by 684%, 258%, and 155% in the ash, 0-5 cm soil depth interval, and >5 cm soil depth interval, respectively. The increases in PAH concentrations associated with mild-intensity fires (412%) exceeded those associated with moderate-intensity (163%) and high-intensity (168%) fires, which is possibly due to pyromineralization or volatilization of organic matters at high burning temperatures. These increases were highest within a month after the fire (280%), gradually decreasing over time, and showed no significant difference compared to the reference sites after 24 months. The concentration increases exhibit no major difference between various vegetation types (broad-leaved forest vs. coniferous forest vs. shrub). Assessments reveal that exposure to post-fire soil PAHs involves no serious human health risk. However, potential adverse effects of soil PAHs on other organisms (e.g., microbes and plants) and ecosystems should be further examined. The present study highlights the strong impacts of soil depth, fire intensity, and post-fire duration, and the relatively weak impact of the vegetation type on PAH concentrations in soils associated with fires in different areas.

Contribution of mulch film to microplastics in agricultural soil and surface water in China.

Agricultural mulch film (AMF) is deemed an important source of microplastics (MPs) in agricultural soil (AS). However, quantitating the contribution of AMFs to MPs in farmland soil and surface water remains a considerable challenge to date. In the present study, a basic framework was developed to address these concerns. First, the concentrations of MPs in soil derived from AMF abrasion (CMP) and the total MPs from all sources in AS (CTMP) were measured. Then, the ratios of CMP to CTMP, i.e., the contribution of AMFs to MPs in AS, were calculated. The contribution of AMFs to MPs in surface water via soil erosion was calculated based on CTMP values, the ratios of CMP to CTMP, soil erosion intensities (SEIs), and farmland areas. Furthermore, the potential contribution of soil erosion to MPs in the ocean was estimated. In China, the inventory of MPs in surface AS in 2018 ranged from 4.9 × 106 to 1.0 × 107 tons according to our results. AMFs contributed 10%-30% of the CTMP with certainties of 60-95%. Assuming that all MPs in AS can be exhaustively transferred to surface water via soil erosion, the national mass transfer amount of MPs (MTTMP) from AS to surface water reached 1.2 × 105-2.2 × 105 tons (∼2% of the inventory of MPs in the AS of China); the fluxes of MPs into the ocean from AS were 3.4 × 104-6.6 × 104 tons, assuming that all MPs in the AS of coastal provinces enter the ocean. It is likely that AMFs contributed 10%-30% MTTMP and fluxes of MPs to the ocean according to the ratios of CMP to CTMP. Apparently, approximately 30% of the national MTTMP (i.e., the rate of MP flux to the ocean to MTTMP) was input to the ocean.

Urinary triclosan in south China adults and implications for human exposure.

Triclosan (TCS) is widely applied in personal care products (PCPs) as an antimicrobial preservative. Due to its toxicity and potential risk to human health, TCS has attracted mounting concerns in recent years. However, biomonitoring of TCS in large human populations remains limited in China. In this study, 1163 adults in South China were recruited and urinary TCS concentrations were determined. TCS was detected in 99.5% of urine samples, indicating broad exposure in the study population. Urinary concentrations of TCS ranged from below the limit of detection (LOD) to 270 µg/L, with a median value of 3.67 µg/L. Urinary TCS concentrations from individuals were all lower than the Biomonitoring Equivalents reference dose, suggesting relatively low health risk in the participants. TCS concentrations did not differ significantly between sexes or education levels (p > 0.05). Nevertheless, marital status and age were found to be positively influence TCS levels (p < 0.001). After adjustment for body mass index (BMI), age was determined to be positively associated with TCS concentrations (p < 0.05), particularly in the age group from 31 to 51 years old. This study provides a baseline of urinary TCS exposure in South China general adult populations.

Cu/N doped lignin for highly selective efficient removal of As(v) from polluted water.

Lignin is a widely used adsorbent for removing heavy metal ions from water. Lignin can be extracted from black liquor and its inert surface properties limit its adsorption performance. In this paper, a new type of modified lignin adsorbent doped with Cu/N was prepared by the reaction of lignin with triethylenetetramine (TETA) and CuCl2. The adsorption capacities of the Cu/N-doped lignin (Cu/N-Lignin) adsorbents, N-doped lignin (N-Lignin) adsorbents and undoped lignin (U-Lignin) on three anions (As (V), Cl- and Cr (VI)) were systematically studied. In the solution with these three mixed ions, the removal rate of the Cu/N-Lignin adsorbents on As (V), Cl- and Cr (VI) was 86.44%, 0% and 39.48%. The adsorption capacity of Cu/N-Lignin to As(V) was 253.5 mg/g. Under the same adsorption conditions, the selectivity of the Cu/N-Lignin adsorbents to anions was Cl-

Controllable antibacterial and bacterially anti-adhesive surface fabricated by a bio-inspired beetle-like macromolecule.

Drug resistance to bacteria becomes an emerging intractable problem, therefore, developing novel antibacterial agents has become urgently needed. Herein, a bio-inspired design strategy was adopted to synthesize a series of beetle-like macromolecule of multiple quaternary ammonium salts (QASs), which was designed with different cationic charge densities and numbers of hexadecane chains by adjusting their different quaternization degree (QD). It was found that the fabricated fabric surface with them exhibited controllable and outstanding antibacterial and bacterially anti-adhesive properties. More importantly, the antibacterial efficiency was demonstrated to be enhanced with the increasing of QD, and related to the zeta potential, and surface tension. Additionally, the proposed bacterially anti-adhesive model of action revealed the "resisting effect" of hydration layer which greatly resisted the adhesion of bacteria.

Syngas production by two-stage method of biomass catalytic pyrolysis and gasification.

A two-stage technology integrated with biomass catalytic pyrolysis and gasification processes was utilized to produce syngas (H(2)+CO). In the presence of different nickel based catalysts, effects of pyrolysis temperature and gasification temperature on gas production were investigated. Experimental results showed that more syngas and char of high quality could be obtained at a temperature of 750°C in the stage of pyrolysis, and in the stage of gasification, pyrolysis char (produced at 750°C) reacted with steam and the maximum yield of syngas was obtained at 850°C. Syngas yield in this study was greatly increased compared with previous studies, up to 3.29Nm(3)/kg biomass. The pyrolysis process could be well explained by Arrhenius kinetic first-order rate equation. XRD analyses suggested that formation of Mg(0.4)Ni(0.6)O and increase of Ni(0) crystallite size were two main reasons for the deactivation of nickel based catalysts at higher temperature.

Production of lightweight ceramisite from iron ore tailings and its performance investigation in a biological aerated filter (BAF) reactor.

The few reuse and large stockpile of iron ore tailings (IOT) led to a series of social and environmental problems. This study investigated the possibility of using the IOT as one of starting materials to prepare lightweight ceramisite (LWC) by a high temperature sintering process. Coal fly ash (CFA) and municipal sewage sludge (SS) were introduced as additives. The LWC was used to serve as a biomedium in a biological aerated filter (BAF) reactor for municipal wastewater treatment, and its purification performance was examined. The effects of sintering parameters on physical properties of the LWC, and leaching concentrations of heavy metals from the LWC were also determined. The microstructure and the phase composition of the LWC were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Results revealed that: (1) IOT could be used to produce the LWC under the optimal sintering parameters; (2) the leaching concentrations of heavy metals from the LWC were well below their respective regulatory levels in the China Environmental Quality Standards for Surface Water (CEQS); and (3) the BAF reactor with the LWC serving as the biomedium achieved high removal efficiencies for COD(Cr) (>92%), NH(4)(+)-N (>62%) and total phosphate (T-P) (>63%). Therefore, the LWC produced from the IOT was suitable to serve as the biomedium in the municipal wastewater treatment.

Novel technology for sewage sludge utilization: preparation of amino acids chelated trace elements (AACTE) fertilizer.

This study developed a novel technology for sewage sludge utilization. The bacteria proteins in the sewage sludge were extracted to produce the amino acid chelated trace elements (AACTE) fertilizer by virtue of several chemical processes. Firstly, the sewage sludge was hydrolyzed under hot hydrochloric acid solution to obtain protein solution. The effects of hydrolysis temperature, reaction time and pH on the extraction ratio of protein from the sewage sludge were investigated. Secondly, the protein solution was further hydrolyzed into amino acids under hot acid condition. The effects of the HCl dosage, hydrolysis temperature and reaction time on the yields of amino acids were investigated in detail. Thirdly, the raw amino acids solution was purified by activated carbon decolorization and glacial acetic acid dissolution. Finally, the purified amino acids were used to produce the AACTE fertilizer by chelating with trace elements. Results showed that, under optimum hydrolysis conditions, 78.5% of protein was extracted from the sewage sludge and the amino acids yield was 10-13 g per 100g of dry sludge. The AACTE fertilizer produced was in accordance with China Standard for Amino Acids Foliar Fertilizer. This novel technology is more environmentally friendly compared with the conventional sludge treatments.

Indoor air concentrations of mercury species in incineration plants for municipal solid waste (MSW) and hospital waste (HW).

Until now, there is limited information about mercury exposures inside solid waste incineration plants although incineration has been considered as one of major solid waste treatments. This study investigated indoor air concentrations of gaseous elemental mercury (GEM), reactive gaseous mercury (RGM) and particulate mercury (Hgp) and indoor dust mercury concentrations in a municipal solid waste incineration (MSWI) plant and a hospital waste incineration (HWI) plant during December 2003 and July 2004. The final results showed that the employees in incineration plants are not only exposed to GEM, but also to RGM and Hgp. For the HWI plant, only concentration of total mercury (HgT) in operation center in summer was below 1000ngm(-3) due to frequent ventilation, while those of GEM and HgT in hospital waste depot exceeded 3000ngm(-3). For the MSWI plant, only concentration of HgT in workplace in winter exceeded 1000ngm(-3). Therefore, more attention should be paid to mercury exposures in HWI plants than in MSWI plants. Indoor dust containing approximately 3968microgHgTkg(-1) (dry matter) possibly served as the potential source for indoor air mercury pollution, especially in the HWI plant.