It is traditionally accepted that urban vegetation contributes to improve air quality by intercepting and retaining the particulate matter. Although the mitigating role of plants has been recognized by several studies, the role of individual species is still poorly understood. This is particularly important in cities like Santiago (Chile), which has high levels of atmospheric particulate and also has high plant species diversity. In this study, we evaluated the retention of atmospheric particles by three widely distributed ornamental species (Nerium oleander, Pittosporum tobira, and Ligustrum lucidum) in Santiago. For this proposal, we took leaf samples in different sampling points across the city which vary in their concentration of atmospheric particulate. Samples were taken 12 and 16 days after a rainfall episode that washed the leaves of plants in the sampling sites. In the laboratory, leaves were washed to recover the surface retained particles that were collected to determine its mass gravimetrically. With this information, we estimated the foliar retention (mass of particulate matter retained in the foliar surface) and daily retention efficiency (mass of particulate matter retained in the foliar surface per day). We found that foliar retention and daily retention efficiency varied significantly between the studied species. The leaves of N. oleander retained 8.2 g m⁻² of particulate matter on average, those of P. tobira 6.1 g m⁻², and those of L. lucidum 3.9 g m⁻²; meanwhile, the daily retention efficiencies of particulate matter were 0.6, 0.4, and 0.3 g m⁻² day⁻¹ for N. oleander, P. tobira, and L. lucidum, respectively. These results suggest that the studied species retain atmospheric particulate matter differentially in Santiago. These results can be attributed to differences on leaf surface characteristics. The recognition of the most efficient species in the retention of the atmospheric particulate matter can help to decide which species can be used to improve the air quality in the city.

Revegetation in arid desert ecosystems is emerging as a practical strategy to cease sand dune encroachment and combat desertification worldwide. The revegetation is expected to affect the spatial distribution of rainfall to the ground within vegetation communities. However, the impact of revegetation on the temporal distribution of dry and/or wet dust fall trapped by shrub canopies via stemflow and throughfall remains a topic of concern for shrub “fertile islands.” This study investigated whether xerophytic shrub community acts as a sink of various cations (Na⁺, K⁺, Ca²⁺, and Mg²⁺), inorganic anions (Cl⁻ and SO₄ ²⁻), total nitrogen, and total phosphorus to the revegetated desert ecosystems. Gross rainfall, the stemflow, and throughfall of two codominated xerophytic shrubs (Caragana korshinskii and Artemisia ordosica) were volumetrically measured after natural rainfall events, and their samples were chemically analyzed in the laboratory. Results showed that ions had higher concentrations in stemflow than in throughfall, followed by gross rainfall. Ion concentrations in stemflow and throughfall strongly depends on the first flush effect, rainfall depth, and the antecedent dry period before a rainfall event occurring. Concentrations of most of the ions in stemflow and throughfall collected after the first rainfall event of a year were obviously higher than other rainfall events for both shrub species, suggesting a first flush effect. Ion concentrations generally decreased with the increasing depth of gross rainfall, stemflow, and throughfall, while increased with prolonged antecedent dry period. Based on nutrient input by stemflow and throughfall at the community scale, we conclude that chemical enrichment of stemflow and throughfall plays an important role in forming the shrub fertile islands and contributes significantly to a sustainable succession of the revegetated desert ecosystems.

In this paper, we present a simple methodological approach to assess the dissolution behaviour of residual light nonaqueous phase liquid (LNAPL) sources entrapped in saturated porous media and to estimate the actual risk to human health by water ingestion related to their presence in the subsurface. The approach consists of collecting experimental data on the release kinetics through lab-scale column tests and including these data in a modified version of the analytical model used to describe the groundwater ingestion pathway in risk analysis. The approach was applied to different test scenarios using toluene as a model compound and three types of porous media, i.e. glass beads and two sandy soils with slightly different textures. The experimental results showed that the concentration of toluene in the eluted water was far from the solubility value after a limited number of pore volumes. Furthermore, different behaviour was observed for the three types of porous media. In particular, higher residual saturation and a slower dissolution rate were observed for the soil characterized by the finest texture. This behaviour suggests that the release rate is inversely proportional to the total residual saturation due to the reduction in the porosity available for water flow and the permeability of the porous media. Using these data in a modified risk-based model showed that a remarkable reduction of the hazard index related to the water ingestion pathway can be achieved for a relatively high groundwater velocity and a small contamination source.

A considerable number of studies have been conducted to investigate the effect of physical and chemical variables on the transport of nanoscale zerovalent iron (nZVI) in granular media. However, the role of soil grain size as a crucial factor in nanoparticle mobility is less understood. The present research work sought to examine the simultaneous effects of soil grain size and particle concentration on the transport of nZVI coated with carboxymethyl cellulose (CMC-nZVI), using saturated sand packed column experiments. To this end, a total of 12 tests were conducted by combining four different particle concentrations (C = 10, 200, 3000, 10,000 mg/l) and three grain sizes (dc = 0.297–0.5 mm, 0.5–1 mm, 1–2 mm). The effluent nZVI concentration and water pressure drop along the column were measured. The results showed that during the injection time, decreasing the grain size and increasing the particle concentration reduces the mobility of CMC-nZVI due to ripening phenomena, while during the flushing time (introducing deionized water), such changes in grain size and particle concentration increase the mobility of CMC-nZVI due to a release from the secondary energy minimum well (in the DLVO theory).

Previous pilot-scale studies have shown outstanding levels of efficiency in phosphorus removal by using hydrated oil shale ash (HOSA) sediments in horizontal subsurface flow (HSSF) filters with low greenhouse gas emissions. However, no long-term full-scale experiment has been conducted using this material. From September 2013 to December 2015, two HSSF filters with different hydraulic loading regimes (NH1 with a stable loading regime and NH2 with a fluctuating regime), used to treat municipal wastewater, were analysed to estimate greenhouse gas (GHG) fluxes and to develop a treatment system with minimised GHG emissions. The fluxes of CO₂, CH₄ and N₂O, as well as their emission factors were significantly lower when compared with studies where regular filter materials (sand, gravel, etc.) are in use. The fluctuating loading regime significantly increased CO₂ and N₂O fluxes (median values of −3.3 and 2.6 mg CO₂−C m⁻² h⁻¹, and 5.7 and 8.6 μg N₂O−N m⁻² h⁻¹ for NH1 and NH2 regimes, respectively), whereas no impact could be seen on CH₄ emissions (median 93.3 and 95.6 μg CH₄−C m⁻² h⁻¹, for NH1 and NH2, respectively). All GHG emissions were strongly affected by the chemical composition of the water entering into the system. The water purification efficiency of the system was satisfactory for most water quality parameters and excellent for phosphorus. Thus, the HOSA-filled filters have a good potential for municipal wastewater treatment with low GHG emission.

The objective of this research was to determine the process of atrazine transport compared to bromide and δO¹⁸ transport in sands near Denver. Three 1.5 × 2 × 1.5-m plots were installed and allowed to equilibrate for 2 years before research initiation and were instrumented with 1.5 × 2-m zero-tension pan lysimeters installed at 1.5-m depths. Additionally, each plot was instrumented with suction lysimeters, tensiometers, time domain reflectometry (TDR) moisture probes, and thermocouples (to measure soil temperature) at 15-cm depth increments. All plots were enclosed with a raised frame (of 8-cm height) to prevent surface runoff. During the 2-year period before research began, all suction and pan lysimeters were purged monthly and were sampled for fluids immediately prior to atrazine and KBr application to obtain background concentrations. Atrazine illustrated little movement until after a significant rainfall event, which peaked concentrations at depths of about 90 to 135 cm. Both Br⁻ and δO¹⁸ moved rapidly through the soil, probably owing to soil porosity and anion exclusion for Br⁻. Concentrations of atrazine exceeding 5.0 μL⁻¹ were observed with depth (90 to 150 cm) after several months. It appears that significant rainfall events were a key factor in the movement of atrazine in the sand, which allowed the chemicals to move to greater depths and thus avoid generally found biodegradation processes.

Biochar produced from agricultural residues through pyrolysis has the characteristics of large specific surface area and porous structure and thus can be used as an adsorbent for various contaminants. In this study, five types of agricultural residues, peanut shells (PS), mung bean shells (MBS), rice husk (RH), corn cob (CC), and cotton stalks (CS), were selected as feedstocks to prepare biochars. Magnesium chloride (MgCl₂; 5 mol L⁻¹ m) solution was used as a modifier to prepare pre-modified and post-modified biochar adsorbents. The modified biochars were used in adsorption experiment to test their sorption ability to phosphate from aqueous solution. Model simulations and analysis were used to determine phosphorus removal mechanisms. Experimental results showed that the phosphate removal efficiency of the pre-modified cotton stalk paralyzed at 600 °C (Pre-CS600) was the best with adsorption capacity of 129.9 mg g⁻¹. The results also showed that the adsorption capacity of the biochar pre-modified by MgCl₂ was much better than that of unmodified and post-modified ones, suggesting the pre-modification method can be used to prepare modified biochars for the removal of phosphorus from aqueous solution.

The aim of this study is to evaluate the fluoride removal from contaminated water using a new adsorbent material of high efficiency to obtain drinking water. The ZrCl₄-graphene supported on vegetal activated carbon composite (G-ZrCl₄/VAC) was synthesized and characterized using transmission and scanning electron microscopy, N₂ physisorption, energy dispersive X-ray spectrometry, Fourier transform-infrared spectroscopy, X-ray diffraction, and Raman spectroscopy. Furthermore, the point of zero charge was determined. The G-ZrCl₄/VAC was evaluated for fluoride adsorptive removal from water under several operating conditions in batch system. The results indicated that fluoride adsorption by G-ZrCl₄/VAC is favored at low pH values with the maximum adsorption at pH 2, corresponding to 97.22% removal. Among the conditions of temperature and agitation evaluated, the best results were achieved at 30 °C and 130 rpm, with removal percentages equal to 47.78 and 48.48%, respectively. The equilibrium of the system was achieved in 5 h of operation. The pseudo-first order kinetic model was the one that best described the kinetic data, while the equilibrium data were best described by the Langmuir isotherm with maximum adsorption capacity equal to 3.89 mg g⁻¹. Therefore, the results obtained show that the material synthesized has a great capacity for adsorption and demonstrate the viability of use of G-ZrCl₄/VAC in the removal of fluoride to obtain drinking water.

This paper attempts to investigate the emissions embodied in Australia’s economic growth and disaggregate primary energy sources used for electricity production. Using time series data over the period of 1990–2012, the ARDL bounds test approach to cointegration technique is applied to test the long-run association among the underlying variables. The regression results validate the long-run equilibrium relationship among all vectors and confirm that CO₂ emissions, economic growth, and disaggregate primary energy consumption impact each other in the long-run path. Afterwards, the long- and short-run analyses are conducted using error correction model. The results show that economic growth, coal, oil, gas, and hydro energy sources have positive and statistically significant impact on CO₂ emissions both in long and short run, with an exception of renewables which has negative impact only in the long run. The results conclude that Australia faces wide gap between emission abatement policies and targets. The country still relies on emission intensive fossil fuels (i.e., coal and oil) to meet the indigenous electricity demand.

Pesticides are used for controlling the development of various pests in agricultural crops worldwide. Despite their agricultural benefits, pesticides are often considered a serious threat to the environment because of their persistent nature and the anomalies they create. Hence removal of such pesticides from the environment is a topic of interest for the researchers nowadays. During the recent years, use of biological resources to degrade or remove pesticides has emerged as a powerful tool for their in situ degradation and remediation. Fungi are among such bioresources that have been widely characterized and applied for biodegradation and bioremediation of pesticides. This review article presents the perspectives of using fungi for biodegradation and bioremediation of pesticides in liquid and soil media. This review clearly indicates that fungal isolates are an effective bioresource to degrade different pesticides including lindane, methamidophos, endosulfan, chlorpyrifos, atrazine, cypermethrin, dieldrin, methyl parathion, heptachlor, etc. However, rate of fungal degradation of pesticides depends on soil moisture content, nutrient availability, pH, temperature, oxygen level, etc. Fungal strains were found to harbor different processes including hydroxylation, demethylation, dechlorination, dioxygenation, esterification, dehydrochlorination, oxidation, etc during the biodegradation of different pesticides having varying functional groups. Moreover, the biodegradation of different pesticides was found to be mediated by involvement of different enzymes including laccase, hydrolase, peroxidase, esterase, dehydrogenase, manganese peroxidase, lignin peroxidase, etc. The recent advances in understanding the fungal biodegradation of pesticides focusing on the processes, pathways, genes/enzymes and factors affecting the biodegradation have also been presented in this review article.