The combination of anthropogenic activities and long-term atmospheric transport has resulted in a sustained increase in global mercury concentrations in air, in water and on land. The Minamata ...Convention on Mercury (MCM), is a global treaty with the goal of protecting human health and the environment from anthropogenic releases of mercury. This study aimed to quantify the mercury inputs and outputs in China in 2016–2019 according to five source categories and investigate the effect of an accelerated scenario/technology transformation required by the MCM on the subsequent distribution of mercury among environmental and intermediate reservoirs. Mercury releases to natural environment decreased dramatically after the MCM, such that around 840 t of mercury was released to those reservoirs in 2019, which is less than 21% of that in 2016 (1,063 t) when an accelerated scenario/technology transformation (STranf) was taken into consideration. Applying the accelerated STranf can hardly change the total release amount to the natural environment, also can reduce 53 t and 58 t of atmospheric emission in 2018 and 2019 respectively. Atmospheric emission was most sensitive to STranf, followed by emissions to land and water. This is the first attempt to provide a systematic evaluation of the effectiveness of the MCM based on the hypothetical expectations. As the MCM moves into the implementation phase, further information from scientific data and studies is critically needed to support decision-making and management. The results of this study can provide such information, facilitating the creation of strategic management policies for mercury as the MCM is implemented in China.
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•China is the largest emitter of anthropogenic mercury worldwide.•The input and output, as well as the subsequent distribution of mercury among environmental and intermediate reservoirs in 2016–2019 were investigated.•Anthropogenic releases to the natural environment was 910–954 t in which 408–467 t emitted to air in 2019.•Atmospheric emission was most sensitive to scenario/technology transformation.•This is the first attempt for an evaluation of the effectiveness of the MCM based on hypothetical expectation.
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•Lipid in microalgae is effectively extracted by subcritical dimethyl ether.•Effect of moisture content in sample on extraction performance is clarified.•Cell disruption highly ...improves the extraction efficiency.•Mechanism of the improvement relies on increasing cell wall’s permeability.•Microalgal residue after the extraction is sufficient to be used as solid fuel.
Subcritical dimethyl ether, a green solvent, was used to extract lipids from microalgae. The effect of the water content on the process was firstly investigated. Secondly, microalgal samples were subjected to five cell disruptions, and the effects on raw lipid and fatty acid methyl ester, and its profile were evaluated. Among them, heating, microwave, and ultrasonic treatments greatly improved extraction. Mechanism analysis revealed the improvements by the three treatments were due to increased cell wall permeability rather than to complete cell disruption. After the extraction, microalgal cells with lipid being well-extracted were shriveled with extensive surface folds, indicating a loss of intracellular substances, but the cell structure was undamaged. As for dewatering performance, extraction process removed almost all of the free water but left bound water. Finally, the potential of the residues after lipid extraction to serve as solid fuel was evaluated by combustion characteristics and heating value calculation.
Dissolved organic matter (DOM) influences the bioavailability and behavior of trace metals and other pollutants in landfill leachate. This research characterized fluorescent dissolved organic matter ...(FDOM) in leachate from an old landfill in Japan during a 13-month investigation. We employed excitation-emission matrix (EEM) fluorescence spectroscopy with parallel factor analysis (PARAFAC) to deconvolute the FDOM complex mixture into three fluorophores: microbial humic-like (C1), terrestrial humic-like (C2), and tryptophan-like fluorophores (C3). These FDOM components were compared with findings from other studies of leachate in landfills with different waste compositions. The correlations among EEM-PARAFAC components, dissolved organic carbon (DOC) concentration, and ultraviolet-visible and fluorescence indices were evaluated. The FDOM in leachate varied spatially among old and extended leachate collected in the landfill and leachate treatment facility. The FDOM changed temporally and decreased markedly in August 2019, November 2019, and April 2020. The strong positive correlation between HIX and %C2 (r = 0.87, rho = 0.91, p 0.72, rho > 0.78, p 0.41, p < 0.001), suggesting the importance of hydrological effects and leachate pump operation on FDOM.
We investigated the potential of waste materials from wastewater treatment plants (WWTPs) to serve as an alternative lipid feedstock for biodiesel production. The average lipid recoveries from fat ...balls (46.4%) and primary scum (49.5-54.5%) were higher than the lipid recovery of primary sludge (15.8-16.4%). The yield of biodiesel produced from the extracted lipids ranged from 5.7 to 20.1%. There were considerable site- and season-dependent variations in the characteristics of the lipid waste materials. Radiocarbon analysis indicated the presence of fossil-derived carbon (26.0-42.0%) in the biodiesel obtained from wastewater lipids. Finally, we estimated the potential for biodiesel production from WWTP-derived lipids; about 333.0 metric tons of biodiesel per year could be produced from fat balls and primary scum in Japan. The results indicate that lipid-rich materials from WWTPs represent a valuable alternative feedstock for biodiesel production.
Open burning of PVC-coated cables is a major source of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F). In the present study, the formation characteristics of PCDD/F from burning of ...PVC-based samples with and without metallic copper were evaluated over the dioxin formation temperature window (200–500 °C). This temperature range also inevitably occurs under open burning conditions. The PCDD/F yield from PVC added with Cu increased by factors of 1390 (300 °C), 65 (400 °C) and 17 (500 °C) compared with that from PVC alone, confirming the stimulatory effect of metallic Cu on PCDD/F production. For the first time, a relatively complete isomer-specific analysis is established for PVC acting as source of PCDD/F. Formation pathways of PCDD/F and the reaction mechanisms were investigated using a combined analysis of PCDD/F isomer signatures, thermogravimetric results and Cl K-edge X-ray absorption spectra. De novo synthesis is the major pathway leading to massive production of PCDD/F. Copper extends the temperature range for the concurrence of de(hydro)chlorination of PVC with cross-linking and aromatisation of polyenes and then stimulates cracking of the chlorine-embedded carbon network. Together, these processes contribute to the strongly enhanced formation of PCDD/F via de novo synthesis.
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•Comparision of PCDD/F formation behaviour from PVC with and without metallic Cu.•Establishment of the isomer-specific analysis for PVC as source of PCDD/F.•Investigation of reaction mechanisms by combining TG and Cl-XANES.•Formation pathways of PCDD/F from PVC and PVC-coated cable are proposed.•Cu acts on the process by affecting both chlorine and carbon.
Flocculation showed the potential for harvesting microalgae at a low cost. The inorganic flocculant (AlCl
3
) and organic flocculant (chitosan) are two representative and common flocculants, which ...were suited for different conditions (pH, salinity, and cell density). To investigate the effects of the three factors on the flocculation performance of the two flocculants, especially for the interaction effects among these factors, single-factor experiments and response surface methodology (RSM) were conducted. The results indicated that AlCl
3
performed better under alkaline conditions, whereas chitosan showed better performance at acidic pH. Salinity had little influence on the flocculation efficiency (FE) of AlCl
3
. By contrast, increasing salinity reduced the FE of chitosan, especially above 8.4 g/L. As cell density increased, the optimal dosage of AlCl
3
increased to a constant ~ 26 g/L. In contrast, the optimal dosage of chitosan continuously increased within the studied range. Also, RSM revealed significant interaction effects of salinitycell density for AlCl
3
, due to which AlCl
3
showed a good flocculation performance under either high cell density or high salinity conditions but poor with both high together. Significant interaction effects of salinitycell density for chitosan was observed, and one of the two factors hence alleviated the negative influence from the other. Considering their performance under the different condition and the interaction effects, dual flocculation with AlCl
3
+ chitosan on multiplex conditions was evaluated, and the results indicated that higher FE with wider applicability could be achieved with lower dosages of the dual flocculant compared with utilization of the two flocculants individually under most of the conditions.
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•The distribution of 18 elements was compared between different incinerators.•Different behavior was observed for the semi-volatiles (Zn, Pb, Ag, As, and Cd) only.•The ISSA from step ...grate is of much lower toxicity than that from fluidized bed.•Step grate seems to be more suitable for sludge incineration than fluidized bed.
We investigated the distribution of 18 elements including non-volatiles (Al, P, Ca, Fe, Mg, K, Mn, Cu, Na, Cr, and Ni), semi-volatiles (Zn, Pb, Ag, As, and Cd), and volatiles (Hg and S) and compared their behaviors in two types of full-scale sewage sludge mono-incinerators, namely, a step-grate stoker (GS) and two fluidized bed incinerators (F-types), with the same feed sludge. Most of the non-volatile elements were enriched five-fold in all incinerated sewage sludge ash (ISSA), while the volatile S and Hg were barely enriched in ash due to the combustion components generated in the gas phase. While the semi-volatile elements were also enriched five-fold in the F-types, a different enrichment behavior was observed in the GS. Boiler and multi-cyclone dust in the GS showed higher enrichments of Pb and Cd compared to ash due to the combined effects of lower temperature and smaller particle size. Compared to the F-types, the GS generated ashes with lower toxicity as the major component (99.7%) and hazardous dust as the minor component. In the future, more attention should be paid to grate stokers in terms of recycling ISSA.
Open burning of electronic waste (E-waste) produces numerous organochlorine compounds (OCs). Although the presence of unidentified OCs has been suggested, the mass balance of identified and ...unidentified OCs in E-waste open burning soils (EOBSs) still remains unknown. In this study, the concentrations of Cl bonded with aromatic carbon (aromatic-Cl) and aliphatic carbon (aliphatic-Cl), and inorganic Cl in EOBSs were determined by focusing on chlorine (Cl) in water-insoluble fractions (insoluble Cl) and applying Cl K-edge X-ray absorption spectroscopy in conjunction with combustion ion chromatography. The concentrations of identified Cl (Cl in five individual OCs: polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, chlorinated polycyclic aromatic hydrocarbons and chlorinated benzenes) were calculated from the concentrations previously reported for the same samples. The proportions of identified Cl were less than 1% to aromatic-Cl, indicating the abundance of unidentified OCs. The concentrations of both aromatic-Cl and identified Cl were highest in the sample collected from the site in Vietnam (VN), where wires and cables were mainly burned, suggesting that unidentified aromatic-Cl were produced through pathways similar to those of identified OCs, and the pathway could be related to burning of wires and cables. Further, insoluble Cu (II) compound, Cu2(OH)3Cl were assumed to be present in EOBSs and the concentration was highest in VN, implying that insoluble inorganic chlorides could be related to the formation of aromatic-Cl and identified Cl.
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•Quantitative speciation of insoluble Cl enabled us to quantify organochlorine.•Cl in PCBs, PCDD/DFs, ClPAHs, and CBzs contributed only 1% to the aromatic-Cl mass.•Insoluble inorganic Cl were present and Cu2(OH)3Cl was identified as a component.•Wire burning could lead higher concentrations of aromatic-Cl and identified Cl.•Aromatic-Cl may have a similar formation pathway to PCBs, PCDD/DFs, and ClPAHs.
