Do geopolitical risk and energy consumption contribute to environmental degradation? Evidence from E7 countries.

Environmental degradation is frequently cited as one of the eminent issues in the modern era. To limit environmental degradation, prior literature discerns several macroeconomic, socio-economic, and institutional factors that affect environmental degradation. However, the relationship between geopolitical risk and environmental degradation is understudied in the previous literature. To fill this gap, the inquiry at hand aims to scrutinize the influence of geopolitical risk on environmental degradation for E7 countries while controlling the effect of renewable energy, non-renewable energy, and GDP. Further, we utilize both the ecological footprint and CO2 emissions as proxies of environmental degradation and employ second-generation panel methods for robust findings. In addition to this, the present study uses augmented mean group (AMG) estimator to provide long-run relationship among the selected variables. The findings from the AMG estimator expound that there exists environmental Kuznets curve (EKC) for E7 countries. Moreover, renewable energy ameliorates environmental quality because it plunges both ecological footprint and CO2 emissions. On the contrary, non-renewable energy consumption escalates both ecological footprint and CO2 emissions. Finally, geopolitical risk tends to decrease CO2 emissions as well as ecological footprint. Our findings deduce a few policy implications to replenish environmental quality. For instance, the share of renewables in the energy mix should be surged to ameliorate the environmental quality. Further, to control both the geopolitical risk and environmental degradation at the same time, policymakers should put forward reforms and initiatives (e.g., policies to escalate R&D, technological innovations, and tax exemptions on imports of renewables) that can help to improve environmental quality without affecting geopolitical risk. At times of low geopolitical risk, environmental degradation will surge; therefore, the rate of environmental control taxes should be increased by the policymakers.

Combined effects of green manure and zinc oxide nanoparticles on cadmium uptake by wheat (Triticum aestivum L.).

Cadmium (Cd) toxicity in agricultural soils is serious concern these days which needs continuous attention. Little is known about the combined use of berseem and/or maize residues soil applied as a green manure alone or along with foliar dressing of zinc oxide nanoparticles (ZnONPs) on Cd accumulation in wheat (Triticum aestivum L.). A pot experiment under ambient conditions with wheat grown in Cd-contaminated soil was performed after soil applied different green manure amendments and foliar dressing of ZnONPs was done during plant growth and plants were harvested at full maturity. Compared with control, plant growth attributes and biomass of above ground parts substantially increased with applied amendments being maximum with combined use of ZnONPs + B75 (berseem residue, 75 mg/kg) followed by ZnONPs + M75 (maize residue, 75 mg/kg). All the treatments improved the leaf chlorophyll contents and improved the leaf antioxidant enzyme activities thereby reduced the leaf electrolyte leakage. The Cd accumulation in roots and aboveground parts of the wheat was reduced especially in ZnONPs + B75 followed by ZnONPs + M75. The higher rate of soil applied amendments along with NPs minimized the available Cd in soil extracts but soil post-harvest pH was not much affected by the applied amendments. In conclusion, incorporation of berseem and maize residues as a green manure applied in Cd-contaminated soil combined with foliar NPs may decrease Cd phytoavailability and its accumulation in wheat grains. However, substantial field studies are required under various environmental conditions before final recommendations at field levels.

Impact of agricultural land use and economic growth on nitrous oxide emissions: Evidence from developed and developing countries.

The environmental Kuznets curve (EKC) establishes a hypothetical link between economic growth and environmental degradation and has been tested empirically using various measures of pollution, including carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emissions. However, few studies have focused on N2O emissions, despite their projected lifetime of 114 years and 300 times greater warming potential than CO2. Employing panel data for the period 1980 to 2012, this study uses the EKC to investigate N2O emissions, including those resulting from agriculture, economic growth, agricultural land use, and exports. Two groups of data are extracted from the panel data: the first group contains the top 15 countries, ranked by N2O emissions, measured in thousand metric tons of CO2, while the second group contains the top 18 countries, ranked by share of agriculture in GDP. A pooled mean group approach developed by Pesaran et al. (1999) is used to determine whether long-run relationships exist between the variables after determined by the Hausman test. The results show that N2O emissions and economic growth are co-integrated in both panels, providing evidence in favour of the EKC. In addition, agricultural land use has a positive and significant effect on N2O emissions. That is, if countries wish to reduce their N2O emissions or agricultural N2O emissions, they should optimize or reduce the use of agricultural land.

Effect of composted organic amendments and zinc oxide nanoparticles on growth and cadmium accumulation by wheat; a life cycle study.

Cadmium (Cd) availability in arable soils is a serious issue while little is known about the role of co-composted organic amendments and zinc oxide nanoparticles (ZnO-NPs) foliar spray on biomass and Cd accumulation in wheat grains. The current study investigated the soil application of organic amendment (composted biochar and farmyard manure) at a level of 0, 1, and 2% w/w and foliar spray of ZnO-NPs (0, 100, and 200 mg/L) on biomass, yield, and Cd in wheat grains cultivated in an aged Cd-contaminated agricultural soil. The results indicated that organic amendment increased the biomass, chlorophyll concentrations, yield, and activities of peroxidase and superoxide dismutase of wheat while decreased the electrolyte leakage and Cd concentrations in different parts of wheat such as shoots, roots, husks, and grains. This effect of organic amendment was further enhanced by the foliar spray of ZnO-NPs in a dose-additive manner. Cadmium concentration in grains was below threshold level (0.2 mg/kg DW) for cereals in combined application of 200 mg/L ZnO-NPs and 1% organic amendment as well as in higher treatment (2%) of organic amendment and NPs. Thus, combined use of organic materials and NPs might be a suitable way of reducing Cd and probably other toxic trace element concentrations in wheat and other cereals.

Application of co-composted farm manure and biochar increased the wheat growth and decreased cadmium accumulation in plants under different water regimes.

Toxic trace element pollution in the agricultural soils may negatively affect the plant growth. This study mainly focused on investigating the impact of co-composted biochar and farmyard manure (FYM) on wheat growth and cadmium (Cd) accumulation by plants. The different ratios of FYM and biochar were composted for two and half months and mixed in Cd-contaminated soil at a rate of 2% w/w of each treatment. After this, wheat seeds were sown in the soil at normal soil moisture (70% of soil water holding capacity (WHC)) level. After 50-day of sowing, both normal and drought stress (35% WHC) levels were applied and plants were harvested at 122 days after seed sowing. The results depicted that Cd and drought alone depressed the wheat growth, elevated the oxidative stress and Cd contents in wheat tissues. However, application of co-composted treatments increased the growth, yield, chlorophyll contents and minimized the oxidative stress in the leaves along with the reduction of Cd concentrations in wheat tissues mainly in grains. The amendments enhanced the post-harvest soil pH and minimized the soil bioavailable Cd. The increasing ratios of biochar in the compost were most effective in improving the growth and alleviating Cd toxicity and its concentration in grains. Overall, co-composted biochar and FYM might be suitable for reducing Cd in grains, but the field studies in different soils and plants are required to further explore the effects of these amendments before final recommendations.

Effect of foliar-applied iron complexed with lysine on growth and cadmium (Cd) uptake in rice under Cd stress.

Contamination of soils with cadmium (Cd) is a serious problem worldwide. Rice (Oryza sativa L.) is reported to accumulate relatively higher Cd contents in consumable parts and is considered a main source of Cd toxicity to humans from rice-derived products. The aim of this pot trial was to investigate the effect of foliar-applied iron (Fe) complexed with lysine on growth, photosynthesis, Cd concentration in plants, oxidative stress, and activities of antioxidants of rice in soil contaminated with Cd. Rice seedlings (30-day-old) were transferred to the soil, and after 2 weeks, different concentrations of Fe-lysine (0, 1.5, 3.0, 4.5, 6.0, and 7.5 mg L-1) were applied as a foliar spray once in a week for 4 weeks and plant samples were taken after 10 weeks of growth in the soil under ambient conditions. Foliar supply of Fe-lysine complex significantly enhanced the plant height, dry weights of plants, concentration of chlorophyll, and gas exchange attributes in Cd-stressed rice. Fe-lysine decreased the Cd concentrations in plants while increasing the Fe concentrations in rice seedlings being maximum with Fe-lysine of 6.0 mg L-1. Electrolyte leakage decreased while activities of key antioxidant enzymes increased with Fe-lysine compared to the control. According to the present results, Fe-lysine complex can effectively be used to reduce Cd concentrations in rice and probably in other crop species.

Management of tannery wastewater for improving growth attributes and reducing chromium uptake in spinach through citric acid application.

The use of chromium (Cr)-contaminated tannery wastewater for irrigation is a common practice, especially in developing countries like Pakistan. This practice is due to the shortage of good quality irrigation water for crop growth as well as the issue of tannery wastewater disposal. The current study was done to evaluate the effect of citric acid (CA) (0, 1.0, and 2.0 mM) on the growth and Cr uptake by spinach irrigated with different mixtures of tap water and tannery wastewater (100:0, 50:50, and 0:100 tap water to wastewater ratio). Plants were grown for 8 weeks under ambient conditions. Results showed that 50:50% tap water and wastewater increased plant height, dry weights of shoots and roots, total chlorophyll contents, and gas exchange attributes than the plants treated with only tap water or only wastewater. Increasing wastewater ratio increased electrolyte leakage (EL) in plants and enhanced the leaf key antioxidant enzyme activities as well as increased Cr contents. Foliar application of CA increased the plant dry weights, photosynthesis, and enzyme activities, whereas reduced the EL and Cr concentrations in plants than respective treatments without CA application. It can be concluded that 50:50 tap water and wastewater irrigation along with foliar CA application might be an effective strategy for increasing vegetable growth with reduced metal concentrations.

Cadmium phytoremediation potential of Brassica crop species: A review.

Cadmium (Cd) is a highly toxic metal released into the environment through anthropogenic activities. Phytoremediation is a green technology used for the stabilization or remediation of Cd-contaminated soils. Brassica crop species can produce high biomass under a range of climatic and growing conditions, allowing for considerable uptake and accumulation of Cd, depending on species. These crop species can tolerate Cd stress via different mechanisms, including the stimulation of the antioxidant defense system, chelation, compartmentation of Cd into metabolically inactive parts, and accumulation of total amino-acids and osmoprotectants. A higher Cd-stress level, however, overcomes the defense system and may cause oxidative stress in Brassica species due to overproduction of reactive oxygen species and lipid peroxidation. Therefore, numerous approaches have been followed to decrease Cd toxicity in Brassica species, including selection of Cd-tolerant cultivars, the use of inorganic and organic amendments, exogenous application of soil organisms, and employment of plant-growth regulators. Furthermore, the coupling of genetic engineering with cropping may also help to alleviate Cd toxicity in Brassica species. However, several field studies demonstrated contrasting results. This review suggests that the combination of Cd-tolerant Brassica cultivars and the application of soil amendments, along with proper agricultural practices, may be the most efficient means of the soil Cd phytoattenuation. Breeding and selection of Cd-tolerant species, as well as species with higher biomass production, might be needed in the future when aiming to use Brassica species for phytoremediation.