Heavy metal pollution is a global ecological safety issue, especially in crops, where it directly threatens regional ecological security and human health. Selecting scientific evaluation methods is an important prerequisite for understanding the distribution of heavy metals in a region. To evaluate the distribution characteristics of arsenic (As), cadmium (Cd), copper (Cu), and zinc (Zn) in farmland soil–rice system in Doumen District of Zhuhai City, Pearl River Delta, we analyzed the high geological background area and heavy metal contents in soil by inverse distance–weighted interpolation and single-factor pollution index. Bioconcentration factor (BCF) was used to study the migration and accumulation characteristics of heavy metals. Then, the soil–rice system was evaluated comprehensively with a novel evaluation method, i.e., the influence index of comprehensive quality (IICQ). Results showed that As, Cd, Cu, and Zn in the soil of the study area followed normal distribution. Cd and Cu were the main pollutants whose point contamination rates were 50% and 22.86%, respectively. A total of 2.86% of the soil were contaminated by As, and no Zn contamination was observed in the soil. At the same time, As and Cd in rice were partially polluted, and the Cu and Zn were not polluted. The order of bioaccumulation coefficient was Cd > Zn > Cu > As, and no evident enrichment was observed. According to the impact index of IICQ to evaluate the pollution of heavy metals in the soil–rice system, 96.98% of the soil in study area was in a state of moderate, heavy, and extreme pollution, which were concentrated in the northern and central parts of the study area. The soil–rice system in the high geological background area was in a subhealthy state. A total of 90.69% of the soil were polluted, but the rice met the national food safety standards.

This study investigates the asymmetric effects of economic growth, energy use, and financial development, on carbon dioxide emissions in Saudi Arabia, from 1971 to 2014, using the nonlinear autoregressive distributed lag (NARDL) model. Prior to the application of the model, the integration proprieties of the variables were examined employing the recently RALS-LM (Residual Augmented Least squares—Lagrange Multiplier) unit root test, with two endogenous structural breaks. The main finding is that there exists an asymmetric cointegration relationship among the variables. In the long-run, both positive and negative shocks in economic growth rise emissions, but the effect of positive shocks is larger. In addition, both positive shocks in energy consumption and negative shocks in financial development surge CO₂ emissions. In the short-run, the increasing economic growth is being made at the expense of the polluted environment. In contrast, any decrease in the economic growth would contribute to the improvement of environmental quality. Furthermore, positive shocks on energy consumption surges CO₂ emissions and positive shocks in financial development reduces emissions. The asymmetric causality test of Hatemi-J (2012) suggests that economic growth (positive shocks) causes carbon dioxide emissions. At the same time, CO₂ emissions (positive shocks) cause energy consumption. However, no significant causal relationship is found between financial development and CO₂ emissions. In light of these findings, some policy implications are recommended.

We found an error in the materials and methods section. Since our team used two methodsfor anesthesia in rats and the anesthesia method used in this paper was 3.5% chloralhydrate anesthesia, we mistakenly wrote the anesthetic as 3% sodium pentobarbital.

The ecological consequences of military spending is a hugely neglected area, and a veil of mystery surrounds this topic. The environmental threats posed by militaries remain insufficiently investigated in the name of national security. Prompted by the internal and external conflicts and prolonged military dictatorships, the Pakistani military assumes a role that goes beyond that of a traditional army. The current study addresses this significant gap in the literature by investigating the impacts of military spending on economic growth and the ecological footprint in Pakistan from 1971 to 2016 using the combined cointegration test and the bootstrap causality test. The findings of the study unveil a positive impact of military spending on the ecological footprint, while a negative impact on economic growth. The outcomes of the bootstrap causality test of Hacker and Hatemi-J (2012) highlight that economic growth Granger causes military spending, while causality runs from military spending to the ecological footprint. Energy consumption contributes to the ecological footprint and economic growth, whereas education expenditures do not influence economic growth and the environment in the long run. Further, the findings suggest a U-shaped link between GDP and footprint in Pakistan. The authorities should focus on resolving external and internal conflicts, on a priority basis, and reduce military spending to improve economic growth and the environment.

Urbanized rivers flowing through polluted megacities receive substantial amount of carbon from domestic sewage and industrial effluents which can significantly alter the air-water CO₂ flux rates. In this regard, we quantified the partial pressure of CO₂ in the surface water (pCO₂(water)), air-water CO₂ fluxes, and associated biogeochemical parameters in the Hooghly River, India, flowing through two of the most polluted cities of the country, Kolkata and Howrah, over a complete annual cycle during spring tidal phase (SP) and neap tidal phase (NP). This urbanized part of Hooghly River was always supersaturated with CO₂ having an annual mean pCO₂(water) and air-water CO₂ flux of ~ 3800 μatm and ~ 49 mol C m⁻² year⁻¹, respectively. Significant seasonal variability was observed for both pCO₂(water) and air-water CO₂ flux (pre-monsoon, 3038 ± 539 μatm and 5049 ± 964 μmol m⁻² h⁻¹; monsoon, 4609 ± 711 μatm and 7918 ± 1400 μmol m⁻² h⁻¹; post-monsoon, 2558 ± 258 μatm and 4048 ± 759 μmol m⁻² h⁻¹, respectively). Monthly mean pH and total alkalinity varied from 7.482 to 8.099 and from 2437 to 4136 μmol kg⁻¹, respectively, over the annual cycle. pCO₂(water) showed significant positive correlation with turbidity and negative correlation with electrical conductivity and gross primary productivity (GPP). High water discharge could have facilitated high turbidity, especially during the monsoon season, which led to depletion in GPP and enhancement in pCO₂(water) which in turn led to very high CO₂ effluxes. The CO₂ efflux rate in this urbanized riverine stretch was substantially higher than that observed in previous studies carried out in the less urbanized estuarine stretch of Hooghly. This indicates that the presence of highly urbanized and polluted metropolis potentially enhanced the pCO₂(water) and CO₂ effluxes of this river. Similar observations were made recently in some Asian and Australian urban rivers.

Water hyacinth (WH) has high tolerance in extreme environmental conditions. Here, we examined the potentials of WH (Eichhornia crassipes (Mart) solms) to remove excess nutrients from sewage wastewater. We used four prototypes of water systems: prototypes A (WH + underlay water) and C (WH + sewage water), whereas prototypes B and D were experimental control for A and C, respectively. For prototype A, the percentage removal efficiencies (%Rₑ) for nitrate and phosphate achieved were 75.12 ± 4.22% and 78.90 ± 8.72%, respectively, with a pH increase from 6.29 to 7.69; whereas for prototype C, the values were 54.7 ± 8.11% and 86.10 ± 7.34%, respectively, with a pH decrease from 8.13 to 7.15. For the 3-week retention time, the biomass weight increased in both prototype A (33.26%; [Formula: see text] rate = 15.46 g/week) and prototype C (26.43%; [Formula: see text] rate = 12.54 g/week). Further, the respective mechanical strength and nutritional values of the WH’s fiber and the organic extracts were examined. The air-dried WH stem showed an average tensile stress of 0.04 MPa on a load at maximum stress of 137.1 N. By comparison, a strand of WH has a tensile strength of 14 MPa, inferior to 15, 61, and 400 MPa shown by timber, wood, and steel, respectively. However, by knitting, four strands of WH yielded a much-improved tensile strength of 315 MPa. Finally, a gas chromatography-mass spectrometer analysis of the plant’s extract showed that it contains 35.51% oleic acid, a nutritional extract of high value. Thence, we established a profound economic significance of WH, a macrophyte with latent immense benefits.

Currently, to reduce the use of nonrenewable energy sources in energy matrices, some industries have already incorporated biomass as a source of energy for their processes. Additionally, filters are used in an attempt to retain the particulate matter present in exhaust gases. In this work, the emission gases of a cashew nut shell (CNS) combustion reactor and the deleterious effects on the respiratory system of mice exposed to gaseous fraction present in CNS emissions (GF-CNS) are analyzed. The system for CNS combustion is composed of a cylindrical stainless steel burner, and exhaust gases generated by CNS combustion were directed through a chimney to a system containing two glass fiber filters to retain all the PM present in the CNS exhaust and, posteriorly, were directed to a mice exposure chamber. The results show changes in the variables of respiratory system mechanics (G, H, CST, IC, and PV loop area) in oxidative stress (SOD, CAT, and NO₂⁻), as well as in the histopathological analysis and lung morphometry (alveolar collapse, PMN cells, mean alveolar diameter, and BCI). Through our results, it has been demonstrated that even with the use of filters by industries for particulate material retention, special attention should still be given to the gaseous fraction that is released into the environment.

Bamboo forests are one of the most important forest resources in subtropical China. A pure, single-layer bamboo forest is considered an optimal habitat for intercropping medicinal herbs. Soil microorganisms have an important role in various ecological processes and respond quickly to environmental changes. However, changes in soil nutrients and microbial communities associated with agroforestry cultivation methods remain poorly documented. In the present study, a pure moso bamboo (Phyllostachys edulis) forest (Con) and three adjacent moso bamboo–based agroforestry (BAF) systems (moso bamboo–Paris polyphylla (BP), moso bamboo–Tetrastigma hemsleyanum (BT) and moso bamboo–Bletilla striata (BB)) were selected; and their soil chemical properties and bacterial communities were studied and compared to evaluate the effects of agroforestry on soil bacterial communities and the relationship between soil properties and bacterial communities in BAF systems. Results showed that compared with soils under the Con, soils under the BAF systems had more (p < 0.05) soil organic carbon (SOC) and available nitrogen (AN) but lower (p < 0.05) pH and available potassium (AK). In addition, compared with the Con system, the BB and BT systems had significantly greater (p < 0.05) available phosphorus (AP). Compared with that in the Con system, the Shannon index in the BAF systems was significantly greater (p < 0.05), but the Chao1 index not different. On the basis of relative abundance values, compared with the Con soils, the BAF soils had a significantly greater abundance of (p < 0.05) Bacteroidetes and Planctomyces but a significantly lower abundance of (p < 0.05) Verrucomicrobia, Gemmatimonadetes and Candidatus Xiphinematobacter. Moreover, compared with the Con system, the BB and BT systems had a greater (p < 0.05) abundance of Actinobacteria, Rhodoplanes, Candidatus Solibacter and Candidatus Koribacter. Redundancy analysis (RDA) revealed that soil pH, SOC and AP were significantly correlated with bacterial community composition. Results of this study suggest that intercropping medicinal herbs can result in soil acidification and potassium (K) depletion; thus, countermeasures such as applications of K fertilizer and alkaline soil amendments are necessary for BAF systems.

The modern agricultural practices have led to improve the contaminated soils with a variety of heavy metals that have become a major environmental concern. The use of arbuscular mycorrihizal fungi (AMF) is considered a potential tool for the sustainable agriculture especially in contaminated sites. Moreover, recently, the use of AMF has become a fascinating and multidisciplinary subject for the scientists dealing with plant protection. The present study was carried out to evaluate the interaction among arsenic (As) species, AMF, and two plant species: Pteris vittata and Astragalus sinicus, differing in their metal tolerance. Results about A. sinicus revealed that the biomass was affected as As (III and V) accumulated in the roots of A. sinicus, and in rachis and pinnae of P. vittata. The inoculation of AMF markedly increased the biomass yield of the both plants when exposed to As species. The exposure to the As species resulted variation and non-significant results about antioxidant enzymes and non-enzymes when grown in As stress with and without AMF. The inoculation of AMF under As species improved the organic acids concentrations in both plant species. Overall, the concentration of oxalate acid was more than formic and malic acids; however, AMF inoculation improved more organic acids in A. sinicus. P. vittata exhibited more activities of antioxidant enzymes and non-enzymes under As stress with and without AMF than A. sinicus, and hence had a more efficient defense mechanism.

Ammonia (NH₃) volatilization from paddy soils is a main source of atmospheric NH₃ and the magnitude is affected by many factors. Because of the complex field condition, it is difficult to identify the relative importance of individual factor on NH₃ volatilization process in different locations and at different times. In this study, the grey relational entropy method was used to evaluate the relative impact of four main factors (i.e., nitrogen fertilizer application rate, NH₄-N concentration, pH, and temperature of the floodwater) on NH₃ volatilization loss from three different field experiments. The results demonstrated that floodwater NH₄-N concentration was the most important factor governing NH₃ volatilization process. Floodwater pH was the second most important factor, followed by temperature of the floodwater and nitrogen fertilizer application rate. We further validated the grey relational entropy method with NH₃ volatilization loss data from other published study and confirmed the order of importance for the four factors. We hope the findings of this study will be helpful for guiding design to reduce paddy soil NH₃ emission.