A large anthropogenic source of mercury pollution is mercury-dependent artisanal and small-scale gold mining (ASGM). Thabeikkyin Township is a small-scale gold mining township located in Pyin Oo Lwin District in the Mandalay Region, Myanmar. The villages of Thabeikkyin Township engage in gold ore crushing, screening, refining, and other mining activities for a living. Miners in this area commonly use mercury for gold recovery by heating amalgam at their homes, gold shops, on the street, and near the riverbank. The evaporated mercury is released into the atmosphere during the heating process and then transported and deposited in the surrounding environments, resulting in the mercury pollution of air, water, soil, etc. To assess atmospheric mercury pollution, a preliminary study on the environmental mercury contamination from ASGM was conducted in Thabeikkyin Township. High mercury concentrations were observed in plant samples collected near the refining sites, ranging 0.33–6.51 ug/g, compared with 0.02 ug/g in Wet Thay Village, where no mercury use was reported. Correlation coefficients between Hg and other heavy metals showed that no heavy metal concentration significantly correlated with that of Hg. The results indicated that the atmospheric environment in the ASGM area of Thabeikkyin Township was contaminated with mercury originating from ASGM, which could very likely deteriorate the health of surrounding residents.

Phytoremediation is an emerging green technology that uses plants and their associated microbes to remediate different environments contaminated with various pollutants. Phytoremediation, as an effective soil remediation technology, has gained popularity in the past ten years both in developed and developing countries. The main goal of the current article is to improve the understanding of phytoremediation of organic pollutants with emphasis on hydrocarbons. To design phytoremediation systems and also enhancement of their efficiency, either in laboratory or in field experiments, there is a serious need for better knowledge of phytoremediation mechanisms and also of factors affecting phytoremediation. In addition to phytoremediation applications, advantages, and limitations, its mechanisms and related new developments have been discussed in this article.

Possibilities of the use of progressive methods in artificial regeneration of areas affected by air pollutants are namely modification of soil environment, active protection of planting stock against root desiccation, use of containerized planting stock for artificial regeneration of clearings, which resulted from air pollution

Current understanding of how environmental aging of microplastics contributes to their ecotoxicity is low. We investigated whether incubation of microplastics in waters with different organic load and toxic potential alters the toxicity of microplastics to crustacean Daphnia magna, fish embryos Danio rerio and plant Lemna minor. Polyethylene primary microplastics; specifically microbeads from facial scrub; were subjected to 3-weeks incubation in low affected spring water, river water, effluent from the municipal wastewater treatment plant (WWTP) and municipal landfill leachate. Primary microplastics had no acute effect on D. magna mobility and D. rerio embryos development. While high organic load wastewaters; WWTP effluent and landfill leachate; showed evident toxicity for D. magna and D. rerio embryos, microplastics aged in these wastewaters had no effect. This suggests that adsorption of pollutants from wastewaters to microplastic particles was not high enough to induce acute toxicity to D. magna and D. rerio. On the contrary, primary microplastics affected the root growth of L. minor. Interestingly, aging of microplastics in low organic-load waters mitigated the toxicity of microplastics for L. minor, while microplastics aged in high-organic load waters had the same adverse effect as primary microplastics. Partly, these effects can be explained by different extent of coating on microplastics in different water samples. This study suggests that aging of microplastics in wastewaters and natural waters did not significantly enhance the toxicity to selected test species, but further studies on plants may be of interest.

In urbanized regions with expansive impervious surfaces and often low vegetation cover, air pollution due to motor vehicles and other combustion sources, is a problem. The poor air quality days in Montreal, Quebec are mainly due to fine particulate matter and ozone. Businesses using wood ovens are a source of particulates. Careful vegetation selection and increased green roof usage can improve air quality. This paper reviews different green roofs and the capability of plants in particulate matter (PM), ozone (O3) as well as nitrogen dioxide (NO2) level reductions. Both the recommended green roof category and plants to reduce these pollutants in Montreal's zone 5 hardiness region are provided. Green roofs with larger vegetation including shrubs and trees, or intensive green roofs, remove air pollutants to a greater extent and are advisable to implement on existing, retrofitted or new buildings. PM is most effectively captured by pines. The small Pinus strobus ‘Nana’, Pinus mugho var. pumilio, Pinus mugho ‘Slowmound’ and Pinus pumila ‘Dwarf Blue’ are good candidates for intensive green roofs. Drought tolerant, deciduous broadleaved trees with low biogenic volatile organic compound emissions including Japanese Maple or Acer palmatum ‘Shaina’ and ‘Mikawa-Yatsubusa’ are options to reduce O3 levels. Magnolias are tolerant to NO2 and it is important in their metabolic pathways. The small cold-tolerant Magnolia ‘Genie’ is a good option to remove NO2 in urban settings and to indirectly reduce O3 formation. Given the emissions by Montreal businesses' wood ovens, calculations performed based on their respective complex roof areas obtained via Google Earth Pro indicates 88% Pinus mugho var. pumilio roof coverage can annually remove 92.37 kg of PM10 of which 35.10 kg is PM2.5. The removal rates are 4.00 g/m2 and 1.52 g/m2 for PM10 and PM2.5, respectively. This paper provides insight to addressing air pollution through urban rooftop greening.

Current risk assessment models for metals such as the biotic ligand model (BLM) are usually applied to individual metals, yet toxic metals are rarely found singly in the environment. In the present research, the toxicity of Cu and Zn alone and together were studied in wheat (Triticum aestivum L.) using different Ca2+ and Mg2+ concentrations, pH levels and Zn:Cu concentration ratios. The aim of the study was to better understand the toxicity effects of these two metals using BLMs and toxic units (TUs) from single and combined metal toxicity data. The results of single-metal toxicity tests showed that toxicity of Cu and Zn tended to decrease with increasing Ca2+ or Mg2+ concentrations, and that the effects of pH on Cu and Zn toxicity were related not only to free Cu2+ and Zn2+ activity, respectively, but also to other inorganic metal complex species. For the metal mixture, Cu–Zn interactions based on free ion activities were primarily additive for the different Ca2+ and Mg2+ concentrations and levels of pH. The toxicity data of individual metals derived by the BLM, which incorporated Ca2+ and Mg2+ competition and toxicity of inorganic metal complexes in a single-metal toxicity assessment, could predict the combined toxicity as a function of TU. There was good performance between the predicted and observed effects (root mean square error [RMSE] = 7.15, R2 = 0.97) compared to that using a TU method with a model based on free ion activity (RMSE = 14.29, R2 = 0.86). The overall findings indicated that bioavailability models that include those biochemistry processes may accurately predict the toxicity of metal mixtures.

The effects of elevated concentrations of atmospheric tropospheric ozone (O3) on DNA damage in five trembling aspen (Populus tremuloides Michx.) clones growing in a free-air enrichment experiment in the presence and absence of elevated concentrations of carbon dioxide (CO2) were examined. Growing season mean hourly O3 concentrations were 36.3 and 47.3 ppb for ambient and elevated O3 plots, respectively. The 4th highest daily maximum 8-h ambient and elevated O3 concentrations were 79 and 89 ppb, respectively. Elevated CO2 averaged 524 ppm (+150 ppm) over the growing season. Exposure to O3 and CO2 in combination with O3 increased DNA damage levels above background as measured by the comet assay. Ozone-tolerant clones 271 and 8L showed the highest levels of DNA damage under elevated O3 compared with ambient air; whereas less tolerant clone 216 and sensitive clones 42E and 259 had comparably lower levels of DNA damage with no significant differences between elevated O3 and ambient air. Clone 8L was demonstrated to have the highest level of excision DNA repair. In addition, clone 271 had the highest level of oxidative damage as measured by lipid peroxidation. The results suggest that variation in cellular responses to DNA damage between aspen clones may contribute to O3 tolerance or sensitivity. Ozone tolerant clones and sensitive Populus tremuloides clones show differences in DNA damage and repair.

The current study provides an information on the combined effect of pollution with potentially toxic elements (PTEs) and polycyclic aromatic hydrocarbons (PAHs) in hydromorphic soils on the accumulation, growth, functional and morphological-anatomical changes of macrophyte plant, i.e., Phragmites australis Cav., as well as information about their bioindication status on the example of small rivers of the Azov basin. The territory of the lower reaches of the Kagalnik River is one of the small rivers of the Eastern Azov region was examined with different levels of PTEs contamination in soils, where the excess of the lithosphere clarkes and maximum permissible concentrations (MPC) for Mn, Cr, Zn, Pb, Cu, and Cd were found. The features of the 16 priority PAHs quantitative and qualitative composition in hydromorphic soils and P. australis were revealed. The influence of soil pollution on accumulation in P. australis, as well as changes in the morphological parameters were shown. It has been observed that morphometric changes in P. australis at sites experiencing the сontamination and salinity are reflected with the changes in the ultrastructure of plastids, mitochondria, and EPR elements of plant cells. PTEs accumulated in inactive organs and damaged cell structures. At the same time, PAHs penetrated through the biomembranes and violated their integrity, increased permeability, resulted cell disorganization, meristem, and conductive tissues of roots. The nature and extent of the structural alterations found are dependent on the type and extent of pollution in the examined regions and can be utilized as bioindicators for evaluating the degree of soil phytotoxicity characterized by the accumulation of PTE and PAHs.

Among emerging organic contaminants (EOCs), triclosan (TCS) is an antibacterial agent and frequently detected in sludge. In this study, RNA sequencing (RNA-seq) was used to obtain the first transcriptomic profile of tobacco with TCS treatment in comparison with control. The results of transcriptome profiling indicated that salicylic acid (SA) signalling pathway actively participated in the tobacco’s response to TCS treatment. The accumulation of endogenous SA in transgene tobacco lines transformed with a homologous gene of SA binding protein (LcSABP) was significantly enhanced. The resistance of transgenic tobacco lines to TCS was markedly enhanced revealed by morphological and physiological indexes while the total Chl level and Pₙ of transgenic individuals showed about 180% and 250% higher than that of WT on average, and the accumulation of H₂O₂ and O₂⁻ induced by TCS in SABP overexpressing tobacco was 35.3%–37.3% and 53.0%–56.0% lower than that of WT. In order to further explore the mechanism of TCS tolerance in transgenic plants, RNA-seq was then performed to obtain the second transcriptomic profile between wild type and transgenic samples with TCS exposure. The results indicated that differentially expressed genes (DEGs) were most highly enriched in MAPK signalling pathway, amino acid synthesis pathway and plant hormone transduction pathway. Especially, genes encoding key proteins such as cytochrome P450, laccase, peroxidase, glycosyl transferase, glutathione S-transferase and ATP-binding cassette were considered to be related to the increased tolerance ability of transgenic tobacco to the treatment of TCS stress. This research will likely provide novel insights into the molecular mechanism of SA-mediated amelioration of TCS stress on tobacco.

With the intended application of engineered nanomaterials (ENMs) in agriculture, accurate assessment the effect of these ENMs on soil microbial communities is especially necessary. Here, maize plants were cultivated in soil amended by SiO₂, TiO₂, and Fe₃O₄ ENMs (100 mg kg⁻¹ soil) for four weeks. The impact of ENMs on bacterial community structure of the rhizosphere soil was investigated by using high-throughput sequencing. In addition, metabolites of maize rhizosphere soil were quantified by gas chromatography-mass spectrometry (GC-MS) based metabolomics. We found that the disturbance of ENMs on soil microbes are in the follow of Fe₃O₄>TiO₂>SiO₂. Exposure of Fe₃O₄ ENMs significantly reduced the abundance of nitrogen-fixation related bacteria Bradyrhizobiaceae (from 2.94% to 2.40%) and iron-redox bacteria Sediminibacterium (from 2.15% to 2.07%). Additionally, Fe₃O₄ ENMs significantly increased populations of Nocardioides (from 1.63% to 1.77%), Chitinophaga sancti (from 1.12% to 2.08%), Pantoea (from 1.31% to 2.22%), Rhizobiumand (from 1.41% to 1.74%) and Burkholderia-Paraburkholderia (from 1.50% to 2.09%), which are associated with carbon cycling and plant growth promoting. This study provides a perspective on the response of rhizosphere microbial community and low molecular weight metabolites to ENMs exposure, providing a comprehensive understanding of the environmental risk of ENMs.