•Production activities caused strong spatial heterogeneity of heavy metal(loid)s.•The migration of heavy metal(loid)s in soils was ordered as cd > zn > pb > as.•Arsenic existed in soil with high ...total contents but weakly migrated.
Heavy metal(loid)s contamination is a constant issue at smelting sites. It is essential to investigate the spatial distribution and migration characteristics of heavy metal(loid)s in the soil for environmental management and remediation strategies of non-ferrous smelting sites. In this study, 203 soil samples from 57 sites were collected in a typical lead smelting site. The findings demonstrated that there were significant Pb, Zn, Cd, and As contamination in soil samples. The spatial distribution of heavy metal(loid)s showed strong spatial heterogeneity, the contaminated soil areas of Pb, As, Cd, and Zn were 99.5%, 98.9%, 85.3%, and 72.4%, respectively. Pb, Cd, and As contamination of the soil reached a depth of 5 m, which migrated from the surface to deep soil layers. The leaching contents of Zn, Pb, and As decreased obviously in 3-4 m soil layer, but the leaching content of Cd was still high, which indicated the high migration of Cd. With the increase of depth, the proportion of acid soluble fraction of heavy metal(loid)s decreased, and the residual fraction increased. The acid soluble fraction of Cd accounted for a higher proportion, and As mainly existed in reducible and residual fractions in soil. According to the calculation of the migration factor, the migration of heavy metal(loid)s in soils were ordered as Cd > Zn > Pb > As. The outcomes are advantageous for risk reduction and site remediation for non-ferrous metal smelting sites.
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•Fate of heavy metals during the hydrothermal treatment of sewage sludge.•Assessment indices of the contamination level and ecological risk of heavy metals.•The effect of reaction temperature and ...reaction time.•The effect of the addition of catalyst/other biomass.•The effect of the type of liquefaction solvent.
Various hydrothermal treatment methods, including hydrothermal carbonization, liquefaction and sub/super-critical water gasification, have been applied to the disposal of sewage sludge for producing bio-materials or bio-fuels. It has become a research hotspot whether the heavy metals contained in sewage sludge can be well treated/stabilized after the hydrothermal treatments. This review firstly summarized the methods of assessing heavy metals’ contamination level/risk and then discussed the migration and transformation behaviors of heavy metals from the following aspects: the effect of reaction temperature, the effect of additives (catalysts and other biomass), the effect of the type of solvent and the effect of reaction time. This review can provide an important reference for the further study of the migration and transformation behaviors of heavy metals during the hydrothermal treatment of sewage sludge.
Context. Exoplanet atmospheres are thought be built up from accretion of gas as well as pebbles and planetesimals in the midplanes of planet-forming disks. The chemical composition of this material ...is usually assumed to be unchanged during the disk lifetime. However, chemistry can alter the relative abundances of molecules in this planet-building material. Aims. We aim to assess the impact of disk chemistry during the era of planet formation. This is done by investigating the chemical changes to volatile gases and ices in a protoplanetary disk midplane out to 30 AU for up to 7 Myr, considering a variety of different conditions, including a physical midplane structure that is evolving in time, and also considering two disks with different masses. Methods. An extensive kinetic chemistry gas-grain reaction network was utilised to evolve the abundances of chemical species over time. Two disk midplane ionisation levels (low and high) were explored, as well as two different makeups of the initial abundances (“inheritance” or “reset”). Results. Given a high level of ionisation, chemical evolution in protoplanetary disk midplanes becomes significant after a few times 105 yr, and is still ongoing by 7 Myr between the H2O and the O2 icelines. Inside the H2O iceline, and in the outer, colder regions of the disk midplane outside the O2 iceline, the relative abundances of the species reach (close to) steady state by 7 Myr. Importantly, the changes in the abundances of the major elemental carbon and oxygen-bearing molecules imply that the traditional “stepfunction” for the C/O ratios in gas and ice in the disk midplane (as defined by sharp changes at icelines of H2O, CO2 and CO) evolves over time, and cannot be assumed fixed, with the C/O ratio in the gas even becoming smaller than the C/O ratio in the ice. In addition, at lower temperatures (<29 K), gaseous CO colliding with the grains gets converted into CO2 and other more complex ices, lowering the CO gas abundance between the O2 and CO thermal icelines. This effect can mimic a CO iceline at a higher temperature than suggested by its binding energy. Conclusions. Chemistry in the disk midplane is ionisation-driven, and evolves over time. This affects which molecules go into forming planets and their atmospheres. In order to reliably predict the atmospheric compositions of forming planets, as well as to relate observed atmospheric C/O ratios of exoplanets to where and how the atmospheres have formed in a disk midplane, chemical evolution needs to be considered and implemented into planet formation models.
•Biochar were obtained from cow manure under different pyrolysis temperatures.•Heavy metals were mostly enriched in biochar during pyrolysis.•The heavy metals were transformed from the bioavailable ...to stable fractions.•Leaching ability of heavy metals were effected by pH and pyrolysis temperatures.•The potential environmental risk and eco-toxicity of heavy metals were relieved.
This study analyzed the chemical speciation, leaching ability, and environmental risk of heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) in cow manure biochar (CMBC) pyrolyzed at various temperatures. The total content, chemical speciation, and leaching ability of the heavy metals were determined through microwave digestion, modified BCR three-step sequential extraction procedure, and leaching solution systems (TCLP, distilled water, and SPLP). The risk assessment code, Muller geo-accumulation index, potential ecological risk index, and germination index were used to evaluate the environmental safety and ecotoxicity of heavy metals. Significant differences were observed in the physicochemical properties of CMBCs. The heavy metal contents in CMBCs were higher than those in CM. The bioavailable fraction of heavy metals was transformed into a relatively stable fraction with increasing pyrolysis temperature. Furthermore, the potential risks and ecotoxicity of biochar were reduced, thus improving environmental safety. The study results provide important data for biochar applications.
Outdoor air pollution adversely affects human health and is estimated to be responsible for five to ten per cent of the total annual premature mortality in the contiguous United States
. Combustion ...emissions from a variety of sources, such as power generation or road traffic, make a large contribution to harmful air pollutants such as ozone and fine particulate matter (PM
)
. Efforts to mitigate air pollution have focused mainly on the relationship between local emission sources and local air quality
. Air quality can also be affected by distant emission sources, however, including emissions from neighbouring federal states
. This cross-state exchange of pollution poses additional regulatory challenges. Here we quantify the exchange of air pollution among the contiguous United States, and assess its impact on premature mortality that is linked to increased human exposure to PM
and ozone from seven emission sectors for 2005 to 2018. On average, we find that 41 to 53 per cent of air-quality-related premature mortality resulting from a state's emissions occurs outside that state. We also find variations in the cross-state contributions of different emission sectors and chemical species to premature mortality, and changes in these variations over time. Emissions from electric power generation have the greatest cross-state impacts as a fraction of their total impacts, whereas commercial/residential emissions have the smallest. However, reductions in emissions from electric power generation since 2005 have meant that, by 2018, cross-state premature mortality associated with the commercial/residential sector was twice that associated with power generation. In terms of the chemical species emitted, nitrogen oxides and sulfur dioxide emissions caused the most cross-state premature deaths in 2005, but by 2018 primary PM
emissions led to cross-state premature deaths equal to three times those associated with sulfur dioxide emissions. These reported shifts in emission sectors and emission species that contribute to premature mortality may help to guide improvements to air quality in the contiguous United States.
Organic aerosol (OA) is one of the major components of fine atmospheric aerosol particles. Recent field campaigns and modeling studies in Colombia have demonstrated the presence of a large OA ...fraction in urban and rural aerosols. In this work we focus on constraining the sources associated with OA and its precursors over the city of Bogotá, Colombia. We used PM2.5 chemical speciation data from field campaigns carried out during 2018 to evaluate the ability of a regional transport model to reproduce and explain the observed OA. The samples were collected at three sites during high- and low-aerosol concentration seasons in the region. We used The Weather Research and Forecasting Model coupled with Chemistry (WRF-Chem) with two different chemical mechanisms and aerosol schemes, RACM/MADE-VBS and MOZART/MOSAIC, in conjunction with the detailed in-situ aerosol chemical speciation observations to analyze the seasonality of OA in the city of Bogotá, and to establish the most relevant sources. Simulations were carried out for the same periods for which data is available, spanning a high biomass burning (BB) season (February 2018) and a low biomass burning season (September 2018). We demonstrated that long-range transport of BB emissions from Northern Amazonia can episodically increase aerosol loading during September, while BB activity in the Grasslands of the Orinoco River Basin are the main source during February. The two aerosol schemes utilized in this work reproduce the observed seasonal variations in total fine aerosol concentration, with a difference between February and September of 10 μg m−3. The comparison between aerosol schemes demonstrated that MOZART/MOSAIC consistently predicted more OA with a larger SOA:OA ratio than in the RACM/MADE-VBS experiment. SOA dominates the OA fraction by 66% for RACM/MADE-VBS and 74% for MOZART/MOSAIC during February and 69% for RACM/MADE-VBS and 71% for MOZART/MOSAIC during September. These differences between organic aerosol burden between the mechanisms used in this study may be attributed to the different treatment of SOA gas/particle partitioning in the schemes.
•WRF-Chem simulations and in-situ PM2.5 chemical composition data were used to understand the contribution of OA over Bogotá.•Biomass burning plumes from Northern Amazonia and from the Orinoco River Grassland can severely impact the region.•Field data shows that OA contributes over 40% to PM2.5 in the city.•The model underpredicts organic aerosols, with the MOZART/MOSAIC scheme predicting higher POA and SOA than RACM/MADE-VBS.
Given the globally increased waste stream of textile dyeing sludge (TDS), its co-combustion with agricultural residues appears as an environmentally and economically viable solution in a circular ...economy. This study aimed to quantify the migrations and chemical speciations of heavy metals in the bottom ashes and gas emissions of the co-combustion of TDS and waste tea (WT). The addition of WT increased the fixation rate of As from 66.70 to 83.33% and promoted the chemical speciation of As and Cd from the acid extractable state to the residue one. With the temperature rise to 1000 °C, the fixation rates of As, Cd, and Pb in the bottom ashes fell to 27.73, 8.38, and 15.40%, respectively. The chemical speciation perniciousness of Zn, Cu, Ni, Mn, Cr, Cd, and Pb declined with the increased temperature. The ash composition changed with the new appearances of NaAlSi3O8, CaFe2O4, NaFe(SO4)2, and MgCrO4 at 1000 °C. The addition of WT increased CO2 and NOx but decreased SO2 emissions in the range of 680–1000 °C. ANN-based joint optimization indicated that the co-combustion emitted SO2 slightly less than did the TDS combustion. These results contribute to a better understanding of ash-to-emission pollution control for the co-combustion of TDS and WT.
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•The co-combustion suppressed As volatilization from 66.70 to 83.33%.•RES of Zn, Cu, Ni, Mn, Cr, Cd, and Pb rose with the co-combustion or temperature rise.•The RES speciation of As turned into ACE, RED and OXI.•The co-combustion reduced SO2 emission at above 680 °C.•Joint emission reduction was quantified with TDS, optimal temperature and blend ratio.
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