One of the main herbicides used in the agricultural environments is 2,4-dichlorophenoxyacetic acid (2,4-D). It is a synthetic plant hormone auxin employed in many crops including rice, wheat, sorghum, sugar cane, and corn to control wide leaf weeds. The indiscriminate use of pesticides can produce numerous damages to the environment. Therefore, this review has the objective to provide an overview on the main characteristics of the herbicides based on 2,4-D, mostly on the role of microorganisms in its degradation and its main degradation metabolite, 2,4- dichlorophenol (2,4-DCP). The remediation processes carried out by microorganisms are advantageous to avoid the pollution of the environment as well as to safeguard the population health.

Nonpoint source phosphorus (P) and nitrogen (N) pollution from agriculture is a global concern. Planting a cover crop after harvesting annual crops such as maize may help mitigate nutrient transport risk to surface and groundwater. Few studies have focused on the impact of a winter rye cover crop on both surface runoff (SR) and tile drainage (TD) water quality. Here, we measured N and P losses in SR and TD from maize plots grown with and without a winter rye cover crop. Four plots (46 × 23 m) in northern New York, USA, equipped with automated SR and TD flow monitoring were planted with winter rye (Secale cereal) in 2016 and 2017 after maize silage harvest. Plots were managed as typical silage fields for dairy farms in the region and received fertilizer and manure applications. Dissolved reactive P (DRP), total P (TP), nitrate-N, total N (TN), and total suspended solids (TSS) loads were monitored from 4/7/16 to 6/29/17. Cumulative SR (volumetric depth equivalent) was 1.8-fold lower for rye compared to control plots. Although runoff and loading were variable, cumulative TSS, TP, and DRP losses were approximately 3-fold lower for rye plots compared to control. Cumulative TN and nitrate-N loads for TD were similar; however, cumulative TN loss for SR was lower for rye plots. Surface runoff was the main pathway of P loss (> 90% of DRP and TP loss) with > 90% of cumulative P exported from 2017 snowmelt events. Results suggest winter rye mitigated N and P transport risk in SR compared to the common practice of leaving maize silage fields bare after harvest.

The scholars of environmental economics have attempted the investigation of the impact of foreign direct investment-growth nexus, but they have missed the essential role played by technological innovation and financial development regarding the environmental costs. The notable economic growth and the consequent speedy process of urbanization in BRICS countries have brought about colossal escalation of energy needs leading to environmental degradation. The present study endeavors to explore the effect of foreign direct investment, technological innovation, and financial development on carbon emissions in BRICS member countries, with data from 1990 to 2017. The results verify a strong cross-sectional dependence within the panel countries. The Augmented Mean Group (AMG) estimator shows that foreign direct investment, technological innovation, and financial development in the BRICS countries possess a negative and statistically significant long-run association with CO₂ emissions, while economic growth, trade openness, urbanization, and energy use are found to contribute statistically significant and positive with carbon emissions. The current study chose to employ the Dumitrescu and Hurlin panel causality test for examining the direction of causality. Findings reveal a bidirectional long-run causality running among financial development, economic growth, trade openness, urbanization, energy use, and CO₂ emissions; on the contrary, unidirectional causality is found between foreign direct investment and carbon emissions. Consequently, for the BRICS member countries, the development of industries, financial institutions, and development of technological innovation are required to attract quality foreign direct investment. Moreover, urbanization contributes enormously to environmental degradation and necessitates urgent policy responses in these countries.

This study aimed to investigate the leaf epicuticular wax and the presence of heavy metals in leaves of Avicennia shaueriana, a halophyte found in Brazilian mangroves. We evaluated plants collected in mangroves located around Sepetiba Bay, Rio de Janeiro State. Heavy metals were analyzed by energy dispersive X-ray spectroscopy (EDS or EDX) and inductively coupled plasma optical emission spectrometry (ICP-OES). Chemical analysis of epicuticular wax was made by gas chromatography–mass spectrometry (GC-MS). We also evaluated the micromorphology of leaf surface using scanning electronic and light microscopy. The leaves from each mangrove presented alterations in wax layer. Fagarasterol (lupeol) in high quantity was the main triterpene identified in the leaf wax from plants collected in all mangroves: Coroa Grande (76.43%), Pedra de Guaratiba (38.91%), and Marambaia (62.56%). Al, Fe, Mn, and Zn were the main heavy metals detected in leaves from the three mangroves by ICP-OES. Thus, we show that that plants able to survive in the mangrove swamp can adapt to the exposure of heavy metals, accumulate them in their leaves, and be used in coastal area recovery projects as a phytoremediator.

In this study, the concentrations of Zn, Cr, Ni, Cu, Pb, As, Cd, and Hg in the surface sediments of 94 sites sampled from six water systems in the Lake Taihu Basin in China were measured, and the pollution risks and sources of the metals were identified. The results showed that the mean concentrations of Zn, Cr, Ni, Cu, Pb, As, Cd, and Hg in the riverine surface sediments were 163.6, 102.5, 45.5, 44.7, 37.0, 13.3, 0.5, and 0.1 mg/kg, respectively, higher than the corresponding background values (except for Hg). According to the geoaccumulation index (Igₑₒ), the Pb, Ni, Zn, Cu, and Cd concentrations in the riverine surface sediments were generally at low levels of pollution. Based on a pollution load index (PLI) evaluation, the Pb, Ni, Zn, and Cu concentrations in the riverine surface sediments were generally at moderate levels of pollution. According to the thresholds of potential ecological risk, the Cd and Hg concentrations in the riverine surface sediments exhibited moderate potential ecological risks. Multivariate statistical analysis indicated that the Pb in the riverine surface sediments primarily originated from domestic sewage, agricultural wastewater discharge, and petroleum combustion; the concentrations of Cr, Ni, and Zn were influenced by the electroplating and alloy manufacturing industries; the concentrations of Cu and As mainly originated from pesticide use and industrial wastewater discharge; and those of Cd and Hg primarily stemmed from industrial wastewater discharge. This research provides information regarding metallic contamination and the possible associated ecological risks to benthic organisms in the surface sediments of river systems and is useful for developing sustainable strategies for environmental pollution control and management in the Lake Taihu Basin.

The potential of using iron-oxidizing and sulfur-oxidizing bioleaching process for removal of heavy metals (HMs) was investigated at initial unadjusted pH of pig manure (PM). The indigenous iron-oxidizing and sulfur-oxidizing microorganisms enriched from PM were primarily Alicyclobacillus and Acidithiobacillus thiooxidans, respectively. After 12 days of bioleaching, 95% of Cu, 96.5% of Zn, 93.6% of Mn, and 92.7% of Cd were removed from the PM in sulfur-oxidizing bioleaching process. Besides, 92.9% of Cu, 94.1% of Zn, 91.9% of Mn, and 90.5% of Cd were removed in iron-oxidizing bioleaching process. Furthermore, 18.1% of TN, 63.3% of TP, 65.4% of TK, and 45.6% of TOC were leached from the PM in the sulfur-oxidizing bioleaching process, whereas only 21.6% of TN, 32.8% of TP, 4% of TK, and 49% of TOC were solubilized in the iron-oxidizing bioleaching process. The X-ray diffraction analysis results demonstrated that there was a large amount of sulfur remained in bioleached manure from the sulfur-oxidizing process which poses a potential risk of soil re-acidification. The Standards, Measurements and Testing Program extraction protocol study on fraction of P in PM showed that the amount of bioavailable P in the sulfur-oxidizing bioleaching process was dramatically declined, whereas it was elevated by 25.9% in the iron-oxidizing bioleaching process. The results obtained in this study indicated that both the sulfur- and iron-oxidizing bioleaching process were able to efficiently remove HMs from PM at initial unadjusted pH, whereas the iron-oxidizing process was proved better method in reserving the fertilizing property and more friendly to the environment.

Nepal’s efforts to reduce manufacturing-related water pollution have faltered because they rely on traditional methods and regulation. We employed an environmentally extended input–output model to establish direct and indirect relations between water pollution and production in 19 Nepalese manufacturing sectors. We identify which are chief emitters of biochemical oxygen demand and total suspended solids. We categorize three sectors as pollution abatement industries (heavy polluters that portend relatively low clean-up costs) and three as pollution prevention industries (polluters responsible for accelerating pollution by inducing the release of pollutants from other linked sectors). We then draw upon statistical analysis to recommend appropriate pollution-reducing incentives or penalties for both categories. We find that incentives to meet discharge standards are effective for pollution abatement industries and that penalties (e.g., polluter pay) are effective in pollution prevention industries because they underpin Nepal’s economy. If these policies do not succeed as desired, emission control policies are warranted.

Respiratory quotient (RQ) is a parameter proposed as a tool for practical and online monitoring of petroleum hydrocarbon biodegradation. Various environmental factors and remediation conditions affect RQ values. Occasionally, actual RQ values deviate from theoretical RQ values of petroleum hydrocarbon biodegradation. In addition, different RQ calculation and interpretation approaches investigated in literature make it difficult to compare the results. In this study, different RQ calculation and interpretation methods given in the literature were compared and the effects of nitrogen biostimulation with ammonium and nitrate salts on RQ values of petroleum hydrocarbon biodegradation were investigated. Respirometric reactors were used in bioremediation of diesel fuel–contaminated soils. Ammonium sulfate and potassium nitrate were amended to enhance hydrocarbon biodegradation. Total n-alkane levels in the soils were analyzed after the incubation period. RQ values were calculated based on continuous CO₂ and O₂ measurements. Biostimulation with ammonium and nitrate led to significant contaminant biodegradation. The nitrogen source type affected RQ values significantly. It was concluded that in evaluating hydrocarbon biodegradability properties and interpreting biostimulation properties, the use of graphical RQ evaluation methods that include plotted statistical approaches allows access to more useful information than using individual theoretical RQ values.

Fluoride (F) and cadmium (Cd) are two common water pollutants. There is low information about their co-exposure in low doses. So, in this study, we evaluated the combination effects of non-toxic doses of F and Cd and the possible mechanism of their combined interaction. Male rats were exposed to non-toxic doses of sodium fluoride (30 mg/l) and/or cadmium chloride (40 mg/l) in drinking water for 6 weeks. Then, liver tissues were separated and several factors including oxidative stress, mitochondrial toxicity, inflammation, apoptosis, and biochemical and histopathological changes were evaluated. Cd and F alone did not induce any significant changes in evaluated factors compared to control group, while significant elevation in liver enzymes as well as histopathological changes were observed in rats treated with F+Cd. Also, a remarkable increase in oxidative stress markers including reactive oxygen species, lipid peroxidation, and protein carbonyl and also decreasing glutathione and superoxide dismutase levels were detected following co-exposure to F and Cd. Furthermore, a combination of F and Cd resulted in mitochondrial dysfunction, swelling, as well as a reduction in mitochondrial membrane potential in isolated liver mitochondria. On the other hand, TNF-α, IL-1β, and NF-kB inflammatory genes were upregulated in the liver after combined exposure to F and Cd compared to individual treatments. Also, F+Cd treatment increased the Bax expression but decreased the expression of Bcl-2 significantly. These findings suggest that Cd and F can potentiate their individual toxic effects on the liver tissue through disruption of the cellular redox status, inflammation, and apoptosis pathway.

Rivers play an irreplaceable role in nature and human society but are the most vulnerable ecosystem in the world to multiple environmental stressors. However, the global-scale research status and the distribution patterns of major stressors in large rivers remain unclear. This study analysed research publications (12,807 documents from 1900 to 2019) related to six large rivers with continental representativeness to tackle these knowledge gaps. The results showed that the total outputs have grown rapidly over the study period, particularly since the 1990s. Consistent with the varied environmental characteristics and problems among the rivers, the research outputs and focuses demonstrated clear differences, which could further be attributed to geographical location, journal preferences and the economic strength of the country in which the river is located. Overall, climate change was the most frequently and widely considered environmental stressor in large rivers. Regardless of climate change, species diversity and hydropower development were widely addressed in the Amazon, Congo and Mekong river basins. Water pollution was the main stressor studied in the Rhine River and Mississippi River, while agricultural irrigation and drought were the most frequently addressed research subjects in the Murray-Darling River. This study provides a comprehensive understanding of the research status and stressor distribution in large global rivers, highlighting the relationship between river research and geographical regions, pointing out future research directions and providing management guidance for large rivers.