This article investigates the long-run and causal linkages between economic growth, CO₂ emissions, renewable and non-renewable (fossil fuels) energy consumption, the Composite Trade Intensity (CTI) as a proxy for trade openness, and the Chinn-Ito index as a proxy for financial openness for a panel of the Commonwealth of Independent States (CIS) region including Armenia, Azerbaijan, Belarus, Georgia, Kazakhstan, Kyrgyzstan, Moldova, Russia, Tajikistan, Turkmenistan, Ukraine, and Uzbekistan over the period of 1992–2015. It is the first time that CTI and the Chinn-Ito indexes are used in an economic-pollution model. Employing three panel unit root tests, panel cointegration estimation methods (DOLS and FMOLS), and two panel causality tests, the main empirical results provided evidence for the bidirectional long-run relationship between all the variables in all 12 sampled countries except for economic growth-renewable energy use linkage. The findings of causality tests indicated that there is a unidirectional short-run panel causality running from economic growth, financial openness, and trade openness to CO₂ emissions and from fossil fuel energy consumption to renewable energy use.

There is no clear understanding of microevolutionary changes in natural populations of plants and animals due to anthropogenic contamination of the environment with toxicants and mutagens. But such data are necessary to forecast long-term effects of human activity. In this research, we studied genetic polymorphism in T. pratense sampled from seven sites varying in radioactive and chemical soil contamination in the vicinity of Vodny settlement (Komi, Russia). Analysis of five SSR loci was shown to be similar in a whole (N), mean (Nₐ) and effective (Nₑ) numbers of alleles, heterozygosity indexes (Hₒ and Hₑ), and the Shannon index (I). Difference in the private allele numbers was registered: the most contaminated site has 5 and others from 0 up 2 private alleles. No difference was found in the genetic structure of T. pratense population growing at the conditions of radioactive and chemical contamination. The Bayesian analysis provided evidence of a single cluster (K = 1) due to a similar genetic structure of samples, while AMOVA results demonstrated a high variability within individuals (75%) and a low variability (1%) among groups of T. pratense from sites that differ in the contamination level. Thus, the long-term radioactive and heavy metal contamination of soil did not result in significant microevolutionary changes in T. pratense population.

Access to safe and reliable drinking water is amongst the important indicators of development in each society, and water scarcity is one of the challenges and limitations affecting development at national and regional levels and social life and economic activity areas. Generally, there are two types of drinking water sources: the first type is surface waters, including lakes, rivers, and streams and the second type is groundwaters existing in aquifers. Amongst aquifers, karst aquifers play an important role in supplying water sources of the world. Therefore, protecting these aquifers from pollution sources is of paramount importance. COP method is amongst the methods to investigate the intrinsic vulnerability of this type of aquifers, so that areas susceptible to contamination can be determined before being contaminated and these sources can be protected. In the present study, COP method was employed in order to spot the regions that are prone to contamination in the region. This method uses the properties of overlying geological layers above the water table (O factor), the concentration of flow (C factor), and precipitation (P factor) over the aquifer, as the parameters to assess the intrinsic vulnerability of groundwater resources. In this regard, geographical information system (GIS) and remote sensing (RS) were utilized to prepare the mentioned factors and the intrinsic vulnerability map was obtained. The results of COP method indicated that the northwest and the west of the region are highly and very vulnerable. This study indicated that regions with low vulnerability were observed in eastern areas, which accounted for 15.6% of the area. Moderate vulnerability was 40% and related to the northeast and southeast of the area. High vulnerability was 38.2% and related to western and southwestern regions. Very high vulnerability was 6.2% and related to the northwest of the area. By means of the analysis of sensitivity of the model, it was determined that the focus factor of the flow has the greatest impact on the creation of vulnerability in the region. Also, these results were validated through electrical conductivity and discharge time series of the regional springs that are located in the vulnerable zones.

As one of the most important contaminants, heavy metals can seriously influence human health via the food chain. In this study, the eco-toxicological effects of Cd²⁺, Pb²⁺, and Hg²⁺ on Moina mongolica Daday were investigated by feeding them Chlorella sp. that contained heavy metals. The relative body lengths of the M. mongolica changed rapidly, peaking at 2 days for Hg²⁺, 6 days for Cd²⁺, and 8 days for Pb²⁺. Moreover, grazing and clearance rates of the experimental group were apparently lower than those of the control group after immersion in heavy metals. Additionally, Cd²⁺ and Pd²⁺ in the food significantly influenced the mean lifespan of M. mongolica of the P and F₁ generations. Egg production per brood was also significantly impacted by Cd²⁺ and Pb²⁺ in the food in generation P. Interestingly, Pb²⁺ was the only metal that significantly influenced the reproduction times of F₂, while the reproductive times were significantly influenced by Cd²⁺ for generation P. Moreover, Cd²⁺, Pb²⁺, and Hg²⁺ in the food significantly influenced the fecundity of generation P. Evaluation of the population growth parameters of M. mongolica revealed that the intrinsic rate of increase, net reproduction rate, and finite rate of increase were significantly influenced by Cd²⁺, Pb²⁺, and Hg²⁺ in the food in generation P. Additionally, Hg²⁺ slightly impacted generation time for generation P. Finally, the acute toxicity toward M. mongolica was Hg²⁺ > Cd²⁺ > Pb²⁺. Overall, heavy metals in the food were likely to influence the growth, survival, and population growth of M. mongolica through the food chain.

Manganese (Mn) is considered as an emerging metal contaminant in the environment. However, its potential interactions with companying toxic metals and the associated mixture effects are largely unknown. Here, we investigated the toxicity interactions between Mn and two commonly seen co-occurring toxic metals, Pb and Cd, in a model organism the nematode Caenorhabditis elegans. The acute lethal toxicity of mixtures of Mn+Pb and Mn+Cd were first assessed using a toxic unit model. Multiple toxicity endpoints including reproduction, lifespan, stress response, and neurotoxicity were then examined to evaluate the mixture effects at sublethal concentrations. Stress response was assessed using a daf-16::GFP transgenic strain that expresses GFP under the control of DAF-16 promotor. Neurotoxicity was assessed using a dat-1::GFP transgenic strain that expresses GFP in dopaminergic neurons. The mixture of Mn+Pb induced a more-than-additive (synergistic) lethal toxicity in the worm whereas the mixture of Mn+Cd induced a less-than-additive (antagonistic) toxicity. Mixture effects on sublethal toxicity showed more complex patterns and were dependent on the toxicity endpoints as well as the modes of toxic action of the metals. The mixture of Mn+Pb induced additive effects on both reproduction and lifespan, whereas the mixture of Mn+Cd induced additive effects on lifespan but not reproduction. Both mixtures seemed to induce additive effects on stress response and neurotoxicity, although a quantitative assessment was not possible due to the single concentrations used in mixture tests. Our findings demonstrate the complexity of metal interactions and the associated mixture effects. Assessment of metal mixture toxicity should take into consideration the unique property of individual metals, their potential toxicity mechanisms, and the toxicity endpoints examined.

Lake water level fluctuations (WLF) are an important factor driving the selection and seasonal dynamics of phytoplankton and potentially toxigenic cyanobacteria. Nevertheless, the relative importance of environmental drivers connected to WLF may be completely different, depending on the typology and use of waterbodies, latitude and climatic regimes. In this study, we investigated the impact of WLF in a large subtropical reservoir in south-eastern China (Hongfeng Reservoir, Guizhou Province). The study was based on monthly samplings carried out in 2014 in six stations. The strong increase in the water level observed in early summer caused a radical shift in the phytoplankton community. While in the pre-flooding period phytoplankton was composed of large diatoms, chrysophytes and Oscillatoriales (mostly Limnothrix sp.), the post-flooding period showed an increase in smaller and more competitive chlorophytes, smaller diatoms and cryptophytes better adapted to a fast colonisation of new and nutrient-rich environments. The environmental drivers that drove the change were dilution, flushing and interference with the seasonal water stratification processes. We concluded that, because WLF represents a complex variable integrating different physical effects in one explanatory descriptor, its value as a predictor of phytoplankton and cyanobacteria dynamics in lake ecosystems is difficult to generalise and needs to be investigated on a case-by-case basis. For this reason, considering the year-to-year hydrological variability that potentially characterise reservoirs, definite indications for management should be outlined considering more than 1-year study.

Constructed wetlands (CWs) cultivated with Myriophyllum aquaticum showed great potential for total nitrogen (TN) removal from aquatic ecosystems in previous studies. To evaluate the growth characteristics, photosynthetic pigment content, and antioxidative responses of M. aquaticum, as well as its TN removal efficiency in CWs, M. aquaticum was treated with different levels of ammonium (NH₄⁺) and nitrate (NO₃⁻) for 28 days. The results indicated that M. aquaticum had strong nitrogen stress tolerance and was more likely to be suppressed by high levels of NH₄⁺ than NO₃⁻. High levels of NH₄⁺ also led to inhibition of synthesis of photosynthetic pigments and increased peroxidase activity in plant leaves, which was not found in the NO₃⁻ treatments. High levels of both NH₄⁺ and NO₃⁻ generated obvious oxidative stress through elevation of malondialdehyde content while decreasing superoxide dismutase activity in the early stage. A sustainable increase of TN removal efficiency in most of the CWs indicated that M. aquaticum was a candidate species for treating wastewater with high levels of nitrogen because of its higher tolerance for NH₄⁺ and NO₃⁻ stress. However, the increase of TN removal efficiency was hindered in the late stage when treated with high levels of NH₄⁺ of 26 and 36 mmol/L, indicating that its tolerance to NH₄⁺ stress might have a threshold. The results of this study will enrich the studies on detoxification of high ammonium ion content in NH₄⁺-tolerant submerged plants and supply valuable reference data for proper vegetation of M. aquaticum in CWs.

In this work, nano-manganese dioxide (nMnO₂)-modified biochar (BC) was synthesized in order to improve BC’s adsorption capacity for di-n-butyl phthalate (DBP) and oxytetracycline (OTC). The results showed that nMnO₂ on the BC surface exhibited a poor crystallinity and oxidation state (Mn (IV)). Sorption experiments showed that, compared to BC, DBP sorption capacity of nMnO₂-BC (1:20) and OTC sorption capacity of nMnO₂-BC (1:10) were 0.0364 and 0.0867 mmol/g, respectively, which are significantly higher than that of BC (0.0141 and 0.0151 mmol/g). Kinetics and isotherm experiments indicated that physical adsorption and chemical interactions have both exerted their impacts on the adsorption process. Further X-ray photoelectron spectroscopy (XPS) analysis showed that part of the Mn (IV) in nMnO₂-BC was reduced to Mn (III) and Mn (II) after DBP or OTC adsorption. Therefore, we suggest the nMnO₂ also acted as an oxidizer on modified BC, which may accelerate the degradation of DBP and OTC.

Whole plants and hypocotyl-derived calli of the halophyte plant species Atriplex atacamensis were exposed to 50 μM arsenate (As(V)) or 50 μM arsenite (As(III)). At the whole plant level, As(III) was more toxic than As(V): it reduced plant growth, stomatal conductance, photosystem II efficiency while As(V) did not. In roots, As accumulated to higher level in response to As(III) than in response to As(V). Within root tissues, both arsenate and arsenite were identified in response to each treatment suggesting that oxidation of As(III) may occur. More than 40% of As was bound to the cell wall in the roots of As(V)-treated plants while this proportion strongly decreased in As(III)-treated ones. In leaves, total As and the proportion of As bound to the cell wall were similar in response to As(V) and As(III). Non-protein thiol increased to higher extent in response to As(V) than in response to As(III) while ethylene synthesis was increased in As(III)-treated plants only. Polyamine profile was modified in a contrasting way in response to As(V) and As(III). At the callus level, As(V) and As(III) 50 μM did not reduce growth despite an important As accumulation within tissues. Calli exposed to 50 μM As did not increase the endogenous non-protein thiol. In contrast to the whole plants, arsenite was not more toxic than arsenate at the cell line level and As(V)-treated calli produced higher amounts of ethylene and malondialdehyde. A very high dose of As(V) (1000 μM) strongly reduced callus growth and lead to non-protein thiols accumulation. It is concluded that As(III) was more toxic than As(V) at the plant level but not at the cellular level and that differential toxicity was not fully explained by speciation of accumulated As. Arsenic resistance in A. atacamensis exhibited a cellular component which however did not reflect the behavior of whole plant when exposed to As(V) or As(III).

The concentration and fluxes of polycyclic aromatic hydrocarbons (PAHs) were investigated in a karst underground river system in southwest China. Groundwater, particles, and sediments from underground river, topsoil, and surface water were monitored, allowing establishment of a conceptual model of PAH transport at the watershed scale. The results showed that PAHs could be transported from the surface to the subsurface through two migration pathways, which were slow-flowing water in the karst fissure and fast-flowing water in conduits. During rainfall events, increasing PAH levels (concentrations and fluxes) at the underground river exit indicated that hydrodynamic force could facilitate PAH transport. The PAHs in water were dominated by dissolved PAHs, accounting for 58.7% of total, especially in the freely dissolved phase, in which SPM-associated PAHs accounted for 41.3% of the total PAHs. Low molecular weight PAHs dominated transport and were mainly transported in dissolved form, whereas high molecular weight PAHs were dominated by SPM-associated transport during the rainfall events. A significantly positive correlation was observed between two-ring and three-ring freely dissolved PAHs and dissolved organic carbon (p < 0.01), respectively. Moreover, PAHs with four to five rings were relatively more abundant in the dissolved organic matter (DOM) associated phase than in the freely dissolved phase, suggesting a major role of DOM in their transport during rainfall events. The trend of PAH fluxes suggested that particle-facilitated transport was another dominant cause of PAH mobilization.