Despite the broad use of lichens as biomonitors of airborne trace elements, the surface chemistry and metal adsorption parameters of these organisms are still poorly known. The current investigation is aimed at (i) quantifying the acid-base surface properties and the first-order physical-chemical parameters of Cu²⁺ and Zn²⁺ adsorption of devitalized Pseudevernia furfuracea, a lichen commonly used in biomonitoring of airborne trace elements, and (ii) comparing the results with those available for moss biomonitors. Equilibrium constants and metal-binding site concentrations were calculated with a thermodynamic model by taking into account the presence/absence of ancillary extracellular cell wall compounds, namely melanin and acetone-soluble lichen substances. An acid–base titration experiment performed in the pH range of 3–10 showed that melanised and non-melanised P. furfuracea samples have lower pHPZC (3.53–3.99) and higher metal-binding site concentrations (0.96–1.20 mmol g⁻¹) compared to that of the mosses investigated so far at the same experimental conditions. Melanin biosynthesis increased the content of carboxyl and phosphoryl groups and reduces that of amine/polyphenols. Cu²⁺ and Zn²⁺ adsorption was unaffected by the degree of melanisation while the removal of extracellular lichen substances slightly decreased Zn²⁺ adsorption. Although Cu²⁺ and Zn²⁺ adsorption parameters related to P. furfuracea surfaces were 3 times lower than in the mosses, lichen samples adsorbed the same amount of Cu²⁺ and 30% more Zn²⁺. The present study contributes in understanding the role of ancillary cell wall compounds in Cu²⁺ and Zn²⁺ adsorption in a model lichen. It also provides a first comparison between the surface physico-chemical characteristics of lichens and mosses frequently used as biomonitors of trace elements.

This work for the first time showed that sulfated BPA could be directly analyzed as BPA with GC-MS after the derivatization with N,O-bis-(trimethylsilyl) trifluoroacetamide (BSTFA)+1% trimethylchlorosilane (TMCS), i.e. the deconjugation step was not necessary. This was because sulfated BPA indeed could be simultaneously deconjugated and derivatized to BPA derivative during derivatization, suggesting that any co-elution of BPA and sulfated BPA during sample extraction led to BPA overestimation in the GC-MS method with BSTFA +1% TMCS as the derivative reagent. Using BPA 4,4′-disulfates (BPA diS) as the pure standard, the co-elution phenomena of sulfated BPA was confirmed with two widely used elution solvents (i.e. methanol and ethyl acetate) or their mixed solutions with different ratios, which further suggested if only sulfated BPA existed in any wastewater sample, BPA was likely over-determined. To further confirm this finding, both influent and effluent samples collected from a local municipal wastewater treatment plant were analyzed, which clearly showed the overestimation of BPA in the two wastewaters due to co-existence of sulfated BPA in the wastewater samples. In addition to BPA, the results also showed the overestimation of other nine bisphenol analogues. As sulfated micropollutants including estrogens, androgens, phytoestrogens, etc., have been widely found in municipal wastewater, the overestimating phenomenon observed in this study may also be extended to determination of other micropollutants, which should be addressed in future.

Heterosigma akashiwo is a commonly found harmful microalgae, however, there are only few studies on its control using algicidal components particularly those identified from algicidal bacteria. In our previous study, ortho-tyrosine and urocanic acid identified from Bacillus sp. B1 showed a significantly high algicidal effect on H. akashiwo. The growth inhibition rates of H. akashiwo after 96 h of treatment with 300 μg/mL o-tyrosine and 500 μg/mL urocanic acid were 91.06% and 88.07%, respectively. Through non-destructive testing by Pulse Amplitude Modulation fluorometry and flow cytometer, the effects of o-tyrosine and urocanic acid on H. akashiwo PS II and physiological parameters (cell volume, mitochondrial membrane potential, and membrane permeability) were estimated. This study shows that o-tyrosine affected the photosynthesis system of H. akashiwo, decreased the mitochondrial membrane potential, and increased the membrane permeability of the algal cells. Treatment with urocanic acid decreased the mitochondrial membrane potential, resulting in the inhibition of algal cell growth and reproduction, but had little effect on membrane permeability and photosynthetic system. Our results may imply that when uridine degrades, surviving H. akashiwo cells may be reactivated. Therefore, o-tyrosine and urocanic acid have the potential to become new biological algicides, which can effectively control the growth of H. akashiwo.

This study characterizes the impacts of transported peat-forest (PF) burning smoke on an urban environment and evaluates associated source burning conditions based on carbon properties of PM₂.₅ at the receptor site. We developed and validated a three-step classification that enables systematic and more rapid identification of PF smoke impacts on a tropical urban environment with diverse emissions and complex atmospheric processes. This approach was used to characterize over 300 daily PM₂.₅ data collected during 2011–2013, 2015 and 2019 in Singapore. A levoglucosan concentration of ≥0.1 μg/m³ criterion indicates dominant impacts of transported PF smoke on urban fine aerosols. This approach can be used in other ambient environments for practical and location-dependent applications. Organic carbon (OC) concentrations (as OC indicator) can be an alternate to levoglucosan for assessing smoke impacts on urban environments. Applying the OC concentration indicator identifies smoke impacts on ∼80% of daily samples in 2019 and shows an accuracy of 51–86% for hourly evaluation. Following the systematic identification of urban PM₂.₅ predominantly affected by PF smoke in 2011–2013, 2015 and 2019, we assessed the concentration ratio of char-EC/soot-EC as an indicator of smoldering- or flaming-dominated burning emissions. When under the influence of transported PF smoke, the mean concentration ratio of char-EC to soot-EC in urban PM₂.₅ decreased by >70% from 8.2 in 2011 to 2.3 in 2015 but increased to 3.8 in 2019 (p < 0.05). The reversed trend with a 65% increase from 2015 to 2019 shows stronger smoldering relative to flaming, indicating a higher level of soil moisture at smoke origins, possibly associated with rewetting and revegetating peatlands since 2016.

Worldwide increasing levels of lead in water systems require the search for efficient ecologically friendly strategies to remove it. Hence, lead accumulation by the free-living algae-like Euglena gracilis and its effects on cellular growth, respiration, photosynthesis, chlorophyll, calcium, and levels of thiol- and phosphate-molecules were analyzed. Photosynthetic cells were able to accumulate 4627 mg lead/kgDW after 5 days of culture with 200 μM Pb²⁺. Nevertheless, exposure to 50, 100 and 200 μM Pb²⁺ for up to 8 days did not modify growth, viability, chlorophyll content and oxygen consumption/production. Enhanced biosynthesis of thiol molecules and polyphosphates, i.e. the two canonical metal ion chelation mechanisms in E. gracilis, was not induced under such conditions. However, in cells cultured in the absence of phosphate, lead accumulation and polyphosphate content markedly decreased, while culturing in the absence of sulfate did not modify the accumulation of this metal. In turn, the total amount of intracellular calcium slightly increased as the amount of intracellular lead increased, whereas under Ca²⁺ deficiency lead accumulation doubled. Therefore, the results indicated that E. gracilis is highly resistant to lead through mechanisms mediated by polyphosphates and Ca²⁺ and can in fact be classified as a lead hyperaccumulator microorganism.

In order to solve the low sorption capacity of pristine biochar for anionic pollutants, e.g., reactive red 120 (RR120), a novel mesoporous Fe-biochar composite was fabricated in this study by combination of Fe-loading and ball-milling methods. The ball-milling Fe-biochar composite could effectively remove RR120 by up to 90.1 mg g⁻¹ at pH of 7.5, and slightly alkaline condition was preferred. Adsorption kinetics showed that ball-milling Fe-biochar composite could quickly sorb RR120 with the rate constant (k₂) of 2.07 g mg⁻¹ min⁻¹ (pH = 7.5). Positive surface charge and large surface area were responsible for the outstanding removal performance of RR120 by ball-milling Fe-biochar composite: (1) The adscititious Fe would be converted to β-FeOOH during pyrolysis, which significantly improved the zeta potential of biochar and thus facilitated the electrostatic adsorption for RR120, which contributed to 42.3% and 85.5% at pH of 3 and 7.5, respectively; (2) Ball-milling effectively increased the specific surface area and uniformed the pore size distribution, which could provide more sorption sites and expedite the diffusion of RR120 molecules, shortening the time from several hours to less than 15 min. Findings of this study not only provide a feasible modification method for biochar to adsorb anionic pollutants efficiently and rapidly, but also help to reveal the roles of Fe-loading and ball-milling in enhancing adsorption capacity.

Cadmium (Cd) is one of the predominant anthropogenic pollutants in aquatic systems. As Cd has negative effects on species at all trophic levels, the community composition in aquatic habitats can be changed as a result of Cd stress. The response of mixotrophic protists to environmental stressors is particularly important as they act as both producers and consumers in complex planktonic communities. In this study, we used mixotrophic Ochromonas gloeopara to study its growth and photosynthetic responses to Cd, and specially focused on the effects of initial Cd concentrations and nutrient levels on its capacity to remove Cd. Results showed that when Cd concentration reached 0.5 mg L⁻¹, the growth rate and carrying capacity were significantly inhibited, whereas the photosynthesis was markedly decreased when Cd concentration reached 0.15 mg L⁻¹. Moreover, under Cd concentration 0.15, 0.5, 0.9, 1.6, and 2.0 mg L⁻¹, the removal efficiencies of Cd by O. gloeopara were 83.2%, 77.7%, 74.6%, 70.1%, and 68.8%, respectively. The increase of nitrogen did not cause significant effect on the removal capacity of Cd by O. gloeopara, but increased concentration of phosphorus significantly enhanced the removal capacity of Cd. Our findings indicated that the mixotrophic O. gloeopara has strong tolerance and capacity to remove Cd, and increasing concentration of phosphorus can increase its removal capacity, suggesting that O. gloeopara has great potential application value in mitigating Cd pollution in waters.

Ammonia (NH₃) volatilization is one of the main pathways of nitrogen loss from cropland, resulting not only in economic losses, but also environmental and human health impacts. The magnitude and timing of NH₃ emissions from cropland fertilizer application highly depends on agricultural practices, climate and soil factors, which previous studies have typically only considered at coarse spatio-temporal resolution. In this paper, we describe a first highly detailed empirical regression model for ammonia (ERMA) emissions based on 1443 field observations across China. This model is applied at county level by integrating data with unprecedented high spatio-temporal resolution of agricultural practices and climate and soil factors. Results showed that total NH₃ emissions from cropland fertilizer application amount to 4.3 Tg NH₃ yr⁻¹ in 2017 with an overall NH₃ emission factor of 12%. Agricultural production for vegetables, maize and rice are the three largest emitters. Compared to previous studies, more emission hotspots were found in South China and temporally, emission peaks are estimated to occur three months earlier in the year, while the total amount of emissions is estimated to be close to that calculated by previous studies. A second emission peak is identified in October, most likely related to the fertilization of the second crop in autumn. Incorporating these new findings on NH₃ emission patterns will enable a better parametrization of models and hence improve the modelling of air quality and subsequent impacts on ecosystems through reactive N deposition.

Continuous tightening emission standards (ESs) facilitate the reduction of organic gas emissions from gasoline vehicles. Correspondingly, it is essential to update the emissions and chemical speciation of total organic gases (TOGs), including volatile organic compounds (VOCs), intermediate volatility organic compounds (IVOCs), CH₄, and unidentified non-methane hydrocarbons (NMHCs) for assessing the formation of ozone and secondary organic aerosol (SOA). In this study, TOG and speciation emissions from 12 in-use light-duty gasoline vehicle (LDGV) exhausts, covering the ESs from China II to China V, were investigated on a chassis dynamometer under the Worldwide Harmonized Light-duty Test Cycle (WLTC) in China. The results showed that the most effectively controlled subgroup in TOG emissions from LDGVs was VOCs, followed by the unidentified NMHCs and IVOCs. The mass fraction of VOCs in TOGs also reduced from 61 ± 9% to 46 ± 18% while the IVOCs gently increased from 2 ± 0.4% to 8 ± 4% along with the more stringent ESs. For the VOC subsets, the removal efficiency of oxygenated VOCs (OVOCs) was lower than those of other VOC subsets in the ESs from China IV to V, suggesting the importance of OVOC emission controls for relatively new LDGVs. The IVOC emissions were mainly subject to the ESs, then driving cycles and fuel use. The formation potentials of ozone and SOA from LDGVs decreased separately 96% and 90% along with the restricted ESs from China II-III to China IV. The major contributor of SOA formation transformed from aromatics in the VOC subsets for China II-III vehicles to IVOCs for China IV/V vehicles, highlighting that IVOC emissions from LDGVs are also needed more attentions to control in future.

Microplastic ingestion has been widely documented in marine zooplankton, but the retention time of microplastics in their digestive gut are still poorly studied, especially among species from different climatic zones and marine habitats. This study evaluated the ingestion and gut retention time of four sizes of fluorescent microplastic beads (1.3, 7.3, 10.6, and 19.0 μm) in stage II naupliar larvae of nine barnacle species from different habitats (epibiotic on turtles, mangroves, coral reefs, and rocky shores) and climatic zones (subtropical/tropical and temperate). Microbeads were not lethal to all species (climatic zones/habitats) tested from the four sizes of non-fluorescent virgin microbeads (1.7, 6.8, 10.4 and 19.0 μm, each at concentrations 1, 10, 100, and 1000 beads mL⁻¹). Gut retention time of microplastic beads in barnacle naupliar larvae significantly increased with decreasing size. Microbeads resided in digestive tracts generally 3–4 times longer in rocky shore and coral reef barnacles than in muddy shore and epibiotic ones. However, species from different climatic zone did not differ in retention time. Our results suggested nauplius larvae from rocky shore and coral reef barnacles appear to be more susceptible to the impacts of longer retained microplastics (e.g., toxic chemicals present on the surface).