Does foreign direct investments impair the ecological footprint? New evidence from the panel quantile regression

This study examines the impact of foreign direct investments on ecological footprint along with other explanatory variables of 92 countries from the year 2001 to 2016. Here, we applied the panel quantile regression model to meet the purpose of our study as it considers unobserved country heterogeneity, unlike other statistical methods. The study reveals that foreign direct investment has a positive relationship with the ecological footprint in each quantile except one, which proves the constancy of the pollution haven hypothesis. Moreover, we also tried to detect the impact of economic growth, manufacturing value-added, the percentage of world exports, and institutional quality on the ecological footprint in this study. The findings of this study also reveal that economic growth and manufacturing value-added are negatively associated with the ecological footprint. With respect to the percentage of world exports and institutional quality, we found a positive relationship with the ecological footprint. From the result of our study, different policy implications have been proposed for host countries and foreign investors on improving the economy through foreign direct investment with minimal ecological footprint.

     

Treatment of tannery wastewater in a pilot-scale hybrid constructed wetland system in Bangladesh

This paper reports the pollutant removal performances of a hybrid wetland system in Bangladesh for the treatment of a tannery wastewater. The system consisted of three treatment stages: a subsurface vertical flow (VF) wetland, followed by a horizontal flow (HF) and a VF wetland. The wetlands were planted with common reed (Phragmites australis), but employed different media, including organic coco-peat, cupola slag and pea gravel. In the first stage, experimental results demonstrated significant removal of ammonia (52%), nitrate (54%), BOD (78%), and COD (56%) under high organics loading rate (690 g COD m⁻² d⁻¹); simultaneous nitrification, denitrification, and organics degradation were attributed to the unique characteristics of the coco-peat media, which allowed greater atmospheric oxygen transfer for nitrification and organic degradation, and supply of organic carbon for denitrification. The second stage HF wetland produced an average PO₄ removal of 61%, primarily due to adsorption by the iron-rich cupola slag media. In the third treatment stage, which was filled with gravel media, further BOD removal (78%) from the tannery wastewater depleted organic carbon, causing the accumulation of NO₃ in the wastewater. Overall, the average percentage removals of NH₃-N, NO₃-N, BOD, COD, and PO₄ were 86%, 50%, 98%, 98% and 87%, respectively, across the whole hybrid system. The results provided a strong evidence to support widespread research and application of the constructed wetland as a low-cost, energy-efficient, wastewater treatment technology in Bangladesh.     

Elevated water temperature reduces the acute toxicity of the widely used herbicide diuron to a green alga, Pseudokirchneriella subcapitata

In the actual environment, temperatures fluctuate drastically through season or global warming and are thought to affects risk of pollutants for aquatic biota; however, there is no report about the effect of water temperature on toxicity of widely used herbicide diuron to fresh water microalgae. The present research investigated inhibitory effect of diuron on growth and photosynthetic activity of a green alga Pseudokirchneriella subcapitata at five different temperatures (10, 15, 20, 25, and 30 °C) for 144 h of exposure. As a result, effective diuron concentrations at which a 50 % decrease in algal growth occurred was increased with increasing water temperature ranging from 9.2 to 20.1 μg L^–1 for 72 h and 9.4–28.5 μg L^–1 for 144 h. The photochemical efficiency of photosystem II (F _v/F _m ratio) was significantly reduced at all temperatures by diuron exposure at 32 μg L^–1 after 72 h. Inhibition rates was significantly increased with decreased water temperature (P?<?0.01). Intracellular H₂O₂ levels as an indicator of oxidative stress were also decreased with increasing temperature in both control and diuron treatment groups and were about 2.5 times higher in diuron treatment groups than that of controls (P?<?0.01). Our results suggest water temperatures may affect the toxicokinetics of diuron in freshwater and should therefore be considered in environmental risk assessment.     

Behavioural correlates of urbanisation in the Cape ground squirrel Xerus inauris

Urbanisation critically threatens biodiversity because of habitat destruction and novel selection pressures. Some animals can respond to these challenges by modifying their behaviour, particularly anti-predator behaviour, allowing them to persist in heavily transformed urban areas. We investigated whether the anti-predator behaviour of the Cape ground squirrel Xerus inauris differed in three localities that differed in their level of urbanisation. According to the habituation hypothesis, we predicted that ground squirrels in urban areas would: (a) be less vigilant and forage more; (b) trade-off flight/vigilance in favour of foraging; and (c) have shorter flight initiation distances (FID) when approached by a human observer. Observations were made in winter and summer at each locality. As expected, ground squirrels in urbanised areas were less vigilant and had shorter FIDs but did not trade-off between foraging and vigilance. In contrast, a population in a non-urbanised locality showed greater levels of vigilance, FID and traded-off vigilance and foraging. A population in a peri-urban locality showed mixed responses. Our results indicate that Cape ground squirrels reduce their anti-predator behaviour in urban areas and demonstrate a flexible behavioural response to urbanisation.     

Influence of source characteristics, chemicals, and flocculation on chemically enhanced primary treatment.

The overall objective of this research was to investigate various methods and parameters to increase the efficiency of chemically enhanced primary treatment (CEPT). The performance of CEPT was evaluated based on its efficiency of removal of nonsettleable solids (NSS). Some of the source characteristics that influenced NSS concentration included influent total suspended solids, influent turbidity, and influent total chemical oxygen demand. A higher concentration of the influent constituents led to a higher NSS concentration, suggesting that NSS represented a somewhat fixed fraction or percent of these influent constituents. The specific particle surface area (SPSA) was found to correlate with percent NSS in the effluent. A higher SPSA is a result of smaller-sized nonsettleable colloidal particles, thus leading to an increase in percent NSS. In summary, there are several parameters that affect NSS, which could be used to control NSS to improve CEPT, as demonstrated by this study.     

Effect of nonionic surfactant partitioning on the dissolution kinetics of residual perchloroethylene in a model porous medium

At concentrations above the critical micelle concentration, surfactants can significantly enhance the solubilization of residual nonaqueous phase liquids (NAPL) and, for this reason, are the focus of research on surfactant-enhanced aquifer remediation (SEAR). As a consequence of their amphiphilic nature, surfactants may also partition to various extents between the organic and aqueous phases, thereby affecting SEAR performance. We report here on the observation and analysis of the effect of surfactant partitioning on the dissolution kinetics of residual perchloroethylene (PCE) by aqueous solutions (1000 mg/L) of the non-ionic surfactant Triton X-100 in a model porous medium. For this fluid system, batch equilibration experiments showed that the surfactant partitions strongly into the NAPL (NAPL-water partition coefficient equal to 12.5). Dynamic interfacial tension (IFT) measurements were employed to study surfactant diffusion and interfacial adsorption. The dynamic IFT measurements were consistent with partitioning of the surfactant between the two liquid phases. PCE dissolution experiments, conducted in a transparent glass micromodel using an aqueous surfactant solution, were contrasted to experiments using clean water. Surfactant partitioning was observed to delay significantly the onset of micellar solubilization of PCE, an observation reproduced by a numerical model. This effect is attributed to the reduction of surfactant concentration in the immediate vicinity of the NAPL-water interface, which accompanies transport of the surfactant into the NAPL. Accordingly, it is suggested that both the rate and the extent of diffusion of the surfactant into the NAPL affect the onset of and the driving force for micellar solubilization. While many surfactants do not readily partition in NAPL, this possibility must be considered when selecting non-ionic surfactants for the enhanced solubilization of residual chlorinated solvents in porous media.     

Pollutant removal from municipal wastewater employing baffled subsurface flow and integrated surface flow-floating treatment wetlands

This article reports pollutant removal performances of baffled subsurface flow, and integrated surface flow-floating treatment wetland units, when arranged in series for the treatment of municipal wastewater in Bangladesh. The wetland units （of the hybrid system） included organic, inorganic media, and were planted with nineteen types of macrophytes. The wetland train was operated under hydraulic loading fluctuation and seasonal variation. The performance analyses （across the wetland units） illustrated simultaneous denitrification and organics removal rates in the first stage vertical flow wetland, due to organic carbon leaching from the employed organic media. Higher mean organics removal rates （656.0 g COD]（m2.day）） did not completely inhibit nitrification in the first stage vertical flow system; such pattern could be linked to effective utilization of the trapped oxygen, as the flow was directed throughout the media by the baffle walls. Second stage horizontal flow wetland showed enhanced biodegradable organics removal, which depleted organic carbon availability for denitrification. The final stage integrated wetland system allowed further nitrogen removal from wastewater, via nutrient uptake by plant roots （along with nitrification）, and generation of organic carbon （by the dead macrophytes） to support denitrification. The system achieved higher E. coli mortality through protozoa predation, E. coli oxidation, and destruction by UV radiation. In general, enhanced pollutant removal efflciencies as demonstrated by the structurally modified hybrid wetland system signify the necessity of such modification, when operated under adverse conditions such as： substantial input organics loading, hydraulic loading fluctuation, and seasonal variation.     

Waste battery disposal and recycling behavior: a study on the Australian perspective

Environmental Science and Pollution Research - Consumer behavior is a critical consideration for the development of sustainable waste management systems, including waste batteries, which pose a...