A novel mobile laser radar system was used for mapping gaseous atomic mercury (Hg0) atmospheric pollution in the Wanshan district, south of Tongren City, Guizhou Province, China. This area is heavily impacted by legacy mercury from now abandoned mining activities. Differential absorption lidar measurements were supplemented by localized point monitoring using a Lumex RA-915M Zeeman modulation mercury analyzer. Range-resolved concentration measurements in different directions were performed. Concentrations in the lower atmospheric layers often exceeded levels of 100 ng/m3 for March conditions with temperature ranging from 5 °C to 20 °C. A flux measurement of Hg0 over a vertical cross section of 0.12 km2 resulted in about 29 g/h. Vertical lidar sounding at night revealed quickly falling Hg0 concentrations with height. This is the first lidar mapping demonstration in a heavily mercury-polluted area in China, illustrating the lidar potential in complementing point monitors.

The partitioning behavior of polycyclic aromatic hydrocarbons (PAHs) between gaseous and particulate phases from coal-fired power plants (CFPPs) is critically important to predict PAH removal by dust control devices. In this study, 16 US-EPA priority PAHs in gaseous and size-segregated particulate phases at the inlet and outlet of the fabric filter unit (FFs) of a circulating fluidized bed (CFB) boiler were analyzed. The partitioning mechanisms of PAHs between gaseous and particulate phases and in particles of different size classes were investigated. We found that the removal efficiencies of PAHs are 45.59% and 70.67–89.06% for gaseous and particulate phases, respectively. The gaseous phase mainly contains low molecular weight (LMW) PAHs (2- and 3-ring PAHs), which is quite different from the particulate phase that mainly contains medium and high molecular weight (MMW and HMW) PAHs (4- to 6-ring PAHs). The fractions of LMW PAHs show a declining trend with the decrease of particle size. The gas-particle partitioning of PAHs is primarily controlled by organic carbon absorption, in addition, it has a clear dependence on the particle sizes. Plot of log (TPAH/PM) against logDp shows that all slope values were below −1, suggesting that PAHs were mainly adsorbed to particulates. The adsorption effect of PAHs in size-segregated PMs for HMW PAHs is more evident than LMW PAHs. The particle size distributions (PSDs) of individual PAHs show that most of PAHs exhibit bi-model structures, with one mode peaking in the accumulation size range (2.1–1.1 μm) and another mode peaking in coarse size range (5.8–4.7 μm). The intensities of these two peaks vary in function of ring number of PAHs, which is likely attributed to Kelvin effect that the less volatile HMW PAH species preferentially condense onto the finer particulates. The emission factor of PAHs was calculated as 3.53 mg/kg of coal burned, with overall mean EFPAH of 0.55 and 2.98 mg/kg for gaseous and particulate phase, respectively. Moreover, the average emission amount of PAHs for the investigated CFPP was 1016.6 g/day and 371073.6 g/y, respectively.

The work was conducted to establish contamination from improper disposal of hazardous wastes containing lead (Pb) and antimony (Sb) into nearby soils. Besides other elements in the affected area, the biological role of Sb, its behaviour in the pedosphere and uptake by plants and the food chain was considered. Wastes contained 139532 ± 9601 mg kg−1 (≈14%) Pb and 3645 ± 194 mg kg−1 (≈0.4%) Sb respectively and variability was extremely high at a decimetre scale. Dramatically high concentrations were also found for As, Cd, Cu, Mn, Ni, Sn and Zn. In adjacent natural soils metal(oid)s amounts decreased considerably (Pb 5034 ± 678 mg kg−1, Sb 112 mg kg−1) though largely exceeded the directives for a given soil use. Metal(oid)s potential mobility was assessed by using H2O→KNO3→EDTA sequential extractions, and EDTA extracts showed the highest concentration suggesting stable humus-metal complexes formation. Nevertheless, selected plants showed high absorption potential of the investigated elements. Pb and Sb values for Dittrichia viscosa grown in wastes was 899 ± 627 mg kg−1 and 37 ± 33 mg kg−1 respectively. The same plant showed 154 ± 99 mg kg−1 Pb and 8 ± 4 mg kg−1 Sb in natural soils. Helichrysum stoechas had 323 ± 305 mg kg−1 Pb, and 8 ± 3 mg kg−1 Sb. Vitis vinifera from alongside vineyards contained 129 ± 88 mg kg−1 Pb and 18 ± 9 mg kg−1 Sb, indicating ability for metal uptake and warning on metal diffusion through the food chain. The biological absorption coefficient (BAC) and the translocation factor (TF) assigned phytoextraction potential to Dittrichia viscosa and Foeniculum vulgare and phytostabilization potential to Helichrysum stoechas. Dissolved metal (oid)s in the analysed water strongly exceeded the current directive being a direct threat for livings. Data warned against the high contamination of the affected area in all its compartments. Even though native plants growing in metal-contaminated sites may have phytoremediation potential, high risk of metal diffusion may threat the whole ecosystem.

Particulate organic matter (POM) acts as a metals sink in soil, but only a few studies focused on the interaction of POM and heavy metals in paddy soil. The aim of this study is to investigate the interaction between POM and Copper (Cu)/Zinc (Zn). Two levels of Cu (100, 400 mg kg⁻¹) and Zn (250, 500 mg kg⁻¹) were used in a soil culture experiment. Our results showed that POM was porous structure and varied in size. Hydroxyl and carboxyl involved in POM adsorption of Cu and Zn. Rhizosphere effects roughen the surface of POM and enhanced the capacity of POM on heavy metals absorption. Cu-humic (26.2–33.9%) and Cu-citrate (38.5–42.4%) were dominated in POM, and Cu-goethite (41.7–57.7%), Cu-sulphide (6.6–27.6%) was dominated in soil. Rhizosphere effects decreased the proportion of organic-bond Cu along with the increasing the proportion of Cu-sulphide in POM. Addition of Cu and Zn inhibited the degradation of POM but rhizosphere effects promoted. Carbon content was increased in POM by heavy metal and rhizosphere effects. Our findings indicated that POM tended to retain the heavy metals in soil and heavy metals inhibited the degradation of POM, however, rhizosphere effects decreased the stability of POM-metals interactions.

Graphene oxide (GO) may strongly interact with toxic metal ions and mineral particles upon release into the soil environment. We evaluated the mutual effects between GO and Ni (Ni(II)) with regard to their adsorption and co-adsorption on two minerals (goethite and hematite) in aqueous phase. Results indicated that GO and Ni could mutually facilitate the adsorption of each other on both goethite and hematite over a wide pH range. Addition of Ni promoted GO co-adsorption mainly due to the increased positive charge of minerals and cation–π interactions, while the presence of GO enhanced Ni co-adsorption predominantly due to neutralization of positive charge and strong interaction with oxygen-containing functional groups on adsorbed GO. Increasing adsorption of GO and Ni on minerals as they coexist may thus reduce their mobility in soil. Extended X-ray absorption fine structure (EXAFS) spectroscopy data revealed that GO altered the microstructure of Ni on minerals, i.e., Ni formed edge-sharing surface species (at RNᵢ₋Fₑ∼3.2 Å) without GO, while a GO-bridging ternary surface complexes (at RNᵢ₋C∼2.49 Å and RNᵢ₋Fₑ∼4.23 Å) was formed with GO. These findings improved the understanding of potential fate and toxicity of GO as well as the partitioning processes of Ni ions in aquatic and soil environments.

A comprehensive study was carried out from central part of Indo-Gangetic Plain (IGP; at Kanpur) to understand abundance, temporal variability, processes (secondary formation and fog-processing) and source-apportionment of PM₁-bound species (PM₁: particulate matter of aerodynamic diameter ≤ 1.0 μm) during wintertime. A total of 50 PM₁ samples were collected of which 33 samples represent submicron aerosol characteristics under non-foggy condition whereas 17 samples represent characteristics under thick foggy condition. PM₁ mass concentration during non-foggy episodes varied from 24–393 (Avg.: 247) μg m⁻³, whereas during foggy condition it ranged from 42–243 (Avg.: 107) μg m⁻³. With respect to non-foggy condition, the foggy conditions were associated with higher contribution of PM₁-bound organic matter (OM, by 23%). However, lower fractional contribution of SO₄²⁻, NO₃⁻ and NH₄⁺ during foggy conditions is attributable to wet-scavenging owing to their high affinity to water. Significant influence of fog-processing on organic aerosols composition is also reflected by co-enhancement in OC/EC and WSOC/OC ratio during foggy condition. A reduction by 5% in mineral dust fraction under foggy condition is associated with a parallel decrease in PM₁ mass concentration. However, mass fraction of elemental carbon (EC) looks quite similar (≈3% of PM₁) but the mass absorption efficiency (MAE) of EC is higher by 30% during foggy episodes. Thus, it is evident from this study that fog-processing leads to quite significant enhancement in OM (23%) contribution (and MAE of EC) with nearly equal and parallel decrease in SO₄²⁻, NO₃⁻ and NH₄⁺ and mineral dust fractions (totaling to 24%). Characteristic features of mineral dust remain similar under foggy and non-foggy conditions; inferred from similar ratios of Fe/Al (≈0.3), Ca/Al (0.35) and Mg/Al (0.22). Positive matrix factorization (PMF) resolves seven sources: biomass burning (19.4%), coal combustion (1.1%), vehicular emission (3%), industrial activities (6.1%), leather tanneries (4%), secondary transformations (46.2%) and mineral dust (20.2%).

Polybrominated diphenyl ether (PBDE) pollution in E-waste recycling areas has garnered great concern by scientists, the government and the public. In the current study, two typical kinds of E-wastes (printed wiring boards and plastic casings of household or office appliances) were selected to investigate the emission behaviors of individual PBDEs during the pyrolysis process. Emission factors (EFs), compositional profile, particle size distribution and gas-particle partitioning of PBDEs were explored. The mean EF values of the total PBDEs were determined at 8.1 ± 4.6 μg/g and 10.4 ± 11.3 μg/g for printed wiring boards and plastic casings, respectively. Significantly positive correlations were observed between EFs and original addition contents of PBDEs. BDE209 was the most abundant in the E-waste materials, while lowly brominated and highly brominated components (excluding BDE209) were predominant in the exhaust fumes. The distribution of total PBDEs on different particle sizes was characterized by a concentration of finer particles with an aerodynamic diameter between 0.4 μm and 2.1 μm and followed by less than 0.4 μm. Similarly, the distribution of individual species was dominated by finer particles. Most of the freshly emitted PBDEs (via pyrolysis) were liable to exist in the particulate phase with respect to the gaseous phase, particularly for finer particles. In addition, a linear relationship between the partitioning coefficient (KP) and the subcooled liquid vapor pressure (PL⁰) of the different components indicated non-equilibrium gas-particle partitioning during the pyrolysis process and suggested that absorption by particulate organic carbon, rather than surface adsorption, governed gas-particle partitioning.

While various investigations have been driven on polybrominated diphenyl ethers (PBDEs) and other flame retardants (FRs) in different framework around the world, information about contamination and fate of PBDEs and other FRs in developing countries especially in the Indian subcontinent is uncommon. Nepal being located in the Indian subcontinent, very little is known about contamination level of semi-volatile organic pollutants discharged into the environment. This motivated us to investigate the environmental fate of halogenated flame retardant (HFRs) in Nepalese condition. In this study, we investigated the concentration, fate, and sources of 9 PBDEs, 2 dechlorane plus isomers (DPs), and 6 novel brominated flame retardants (NBFRs). Moreover, air-soil exchange and soil–air partitioning were also evaluated to characterize the pattern of air-soil exchange and environmental fate. In general, the concentrations of NBFRs in soil were more prevalent than PBDEs and DPs, and accounted 95% of ∑HFRs. By and large, the concentrations of NBFRs and DPs were measured high in Kathmandu, while PBDEs level exceeded in Pokhara. Principal component analysis (PCA) study suggested contributions from commercial penta-, octa-, and deca-BDEs products and de-bromination of highly brominated PBDEs as the significant source of PBDEs. Likewise, low fₐₙₜᵢ ratio suggested DPs in soil might have originated from long-range atmospheric transport from remote areas, while high levels of decabromodiphenyl ethane (DBDPE) in soil were linked with the use of wide varieties of consumer products. The estimated fugacity fraction (ff) for individual HFR was quite lower (<0.05) than equilibrium value, suggesting that deposition and net transport from air to the soil is overwhelming. Soil-air partitioning study revealed neither octanol-air partition coefficient (KOA) nor black carbon partition coefficient (KBC₋A) is an appropriate surrogate for soil organic matter (SOM), subsequently, absorption by SOM has no or little role in the partitioning of HFRs.

A substantial amount of sulfate is often supplied in paddy fields with concomitant applications of chemical fertilizers and manure for rice growth. It is unclear how solubility and speciation of arsenic (As) are affected by the levels of soil sulfate and their relationship to soil redox status and sulfur (S) and iron (Fe) speciation in a short cycle of soil reducing (flooding) and oxidizing (drying) periods. The objective of this study was to investigate the solubility of As in relation to chemical speciation of As and S in different levels of soil sulfate through a time series of measurements during a 40-day reduction period (Eh < −130 mV) followed by a 32-day reoxidation period (Eh > 400 mV) using X-ray absorption fine structure (XAFS) spectroscopy. An excess of sulfate decreased extractable and dissolved As in the soil reducing period due to retardation of soil reduction process that decreased soluble As(III) in the soil solid phase. The As species at the end of soil reducing period were 38–41% As(V), 46–51% As(III), and 11–13% As2S3-like species, regardless of initial S treatments. In the following soil reoxidation, As2S3-like species were sensitive to oxidation and disappeared completely in the first 2 days when the Eh value increased rapidly above 160 mV. The addition of extra sulfate to the soil did not result in the formation of neither reduced S species nor As2S3-like species. About 50% of As(III) to the total As persisted over 32 days of soil reoxidation period (Eh > 400 mV), suggesting some mechanisms against oxidation of As(III) such as physical sequestration in soil microsites. This study demonstrates that the extra SO4 in paddy soils can help mitigate the dissolution of As in reduction and reoxidation periods.

Humic-like substances (HULIS) are a class of high molecular weight, light-absorbing compounds that are highly related to brown carbon (BrC). In this study, the sources and compositions of HULIS isolated from fine particles collected in Beijing, China during the 2014 Asia-Pacific Economic Cooperation (APEC) summit were characterized based on carbon isotope (¹³C and ¹⁴C) and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analyses, respectively. HULIS were the main light-absorbing components of water-soluble organic carbon (WSOC), accounting for 80.2 ± 6.1% of the WSOC absorption capacity at 365 nm. The carbon isotope data showed that HULIS had a lower non-fossil contribution (53 ± 4%) and were less enriched with ¹³C (−24.2 ± 0.6‰) relative to non-HULIS (62 ± 8% and −20.8 ± 0.3‰, respectively). The higher relative intensity fraction of sulfur-containing compounds in HULIS before and after APEC was attributed to higher sulfur dioxide levels emitted from fossil fuel combustion, whereas the higher fraction of nitrogen-containing compounds during APEC may have been due to the relatively greater contribution of non-fossil compounds or the influence of nitrate radical chemistry. The results of investigating the relationships among the sources, elemental compositions, and optical properties of HULIS demonstrated that the light absorption of HULIS appeared to increase with increasing unsaturation degree, but decrease with increasing oxidation level. The unsaturation of HULIS was affected by both sources and aging level.