Temporal–spatial distribution of synthetic pyrethroids (SPs) in overlying water and surface sediments and ecological risk to aquatic systems were investigated, where paired water and surface sediments were collected during dry and wet periods in Guangzhou urban waterways. Eight target SPs (i.e., tefluthrin, bifenthrin, cyhalothrin, permethrin, cyfluthrin, cypermethrin, esfenvalerate, and deltamethrin), with cypermethrin and permethrin as major components, were ubiquitously detected in both water (dissolved and particle phases, separately) and sediments. Significant increases of ΣSP (sum of eight SPs) concentrations were observed in both water and sediment from the dry period to the wet period. The spatial distribution of SPs was mostly impacted by land-use type, with the highest ΣSP concentrations in the residential areas, which indicates the massive application of pyrethroids in household mosquito control. It is demonstrated that SPs preferred to be adsorbed to the particles, and rainfall-induced runoff was suggested as an important mechanism that moved SPs to the receiving waterways. A rising trend on sediment concentrations of SPs in the Guangzhou area in the last decade implied increasing application of pyrethroid insecticides, with cypermethrin and permethrin as the dominant components, where the contamination of SPs was positively related with urbanization rate (e.g., resident population and green coverage area). A special emphasis was placed on the potential effects of both individual SPs and their mixtures in three trophic levels (i.e., algae, daphnia, and fish) using toxic units (TUs) and risk quotients (RQs) for water and sediments. In spite of no acute effects due to SPs in the sediments, the toxic units showed daphnia as the most sensitive species in water, with acute risks to daphnia exhibited in several sampling sites. The risk assessment points out that a chronic toxicity (RQ index) caused by SPs in three trophic levels (algae, daphnia, and fish) exists, especially in Daphnia magna. Graphical abstract

The purpose of this piece of work is to study the process of adsorption of paracetamol on activated carbon, silica and alumina and their degradation using UV radiation. The results demonstrate a higher adsorption of paracetamol on alumina and activated carbon, while a minor value was observed in the case of silica. The H-bonding and π-stacking interactions between paracetamol and supports can be explained by the variation in the adsorption capacity values. When the paracetamol adsorbed was irradiated with two different UV irradiance values (59.78 mW cm⁻² and 119.56 mW cm⁻²) for 120 min, the higher degradation percentage was observed on activated carbon with a value of 79%. In the case of alumina and silica, the maximum percentages obtained were 65% and 77%, respectively. The incorporation of H₂O₂ in the reaction medium increases the rate of degradation, mainly at higher irradiance, reaching the maximum values in less time.

The anode configuration determined the performance of power generation and contaminant removal in microbial fuel cell (MFC). In this study, double anodes were constructed along an up-flow MFC for mitigating the suppression of refractory organic azo dye Reactive Brilliant Red X-3B and increasing the power output. Results revealed that high concentration of X-3B suppressed the power generation of MFC. The maximum power density decreased from 0.413 to 0.161 W/m³, and the inner resistance rose from 448 to 698 Ω. However, double anodes weakened the suppression of X-3B to the current generation. Compared with single anode, the attenuation of MFC current decreased from 48 to 40%. Meanwhile, the X-3B removal efficiency in double-anode MFC was 19.81% higher compared with a single-anode condition when the X-3B was 1000 mg/L. The degradation pathway analysis indicated that aromatic amines formation and further oxidation were achieved sequentially in the MFC. Furthermore, microbial communities in the lower and upper anodes were analyzed, revealing that the microorganisms in the lower anode were more inclined to degrade the pollutant, whereas those in the upper anode were more inclined to generate electricity. This double-anode structure showed the potential for large concentration range of azo dye removal and the current recovery in real textile wastewater.

Bioretention is one of the most popular technical practices for urban runoff pollution control. However, the efficiency of nutrient removal from urban stormwater runoff by bioretention systems varies significantly. To improve the nutrient removal performance, innovative up-flow and mixed-flow bioretention systems were proposed in this study, and a laboratory study was conducted to investigate the runoff retention and nutrient removal performance. During the leaching experiment using tap water as the inflow, turbidity, chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) leaching phenomenon was obvious. COD and TN leaching controls were obviously improved when the up-flow and mixed-flow bioretention systems were adopted comparing with the conventional bioretention. During the semi-synthetic runoff experiments, after the leaching experiments’ performance (accumulated 2.78 times of empty bed volume), there were no significant differences in COD mass removal efficiencies of conventional and up-flow bioretention processes (p > 0.05); however, the COD mass removal efficiencies of the mixed-flow bioretention processes increased by 10% when compared with conventional bioretention. The TN mass removal efficiencies of the up-flow and mixed-flow bioretention increased obviously from 17% ± 13% (conventional) to 41% ± 23% (up-flow) and 31% ± 16% (mixed-flow). However, there were no significant differences in TP mass removal or runoff reduction among the three bioretention columns (p > 0.05). Both up-flow and mixed-flow bioretention can effectively improve TN mass removal, and the mixed-flow bioretention did not show a better TN removal performance than the up-flow bioretention because these two bioretention had almost the same volume of the saturated zone. Overall, the results indicate the mixed-flow bioretention proposed in this study can effectively improve TN mass removal and slightly improve COD mass removal relative to conventional methods via increases in hydraulic retention time and in-flow paths, respectively.

The quantity, intensity, and quality of urban stormwater runoff are changing as a consequence of urbanization and climate change. Low impact development (LID) techniques (e.g., bioretention systems) are emerging to manage runoff quantity and quality. Street tree pits were used as bioretention units in Montreal, Canada. The concentration and mass flux of contaminants (Na, Cr, Ni, Cu, Zn, Cd, Pb) and dissolved organic carbon (DOC) were measured in soil solution samples from the tree pits. The soil organic matter (SOM) and the permeability of the area nearby the tree pit (sidewalk and front lawn) were tested. The SOM did not affect contaminant concentrations. However, tree pits with higher SOM reduced the mass flux of contaminants more than tree pits with lower SOM. Sidewalk permeability decreased the concentration and mass flux of contaminants observed (e.g., Na and Cr). The estimated water flux in the open part of the tree pit changed from 6.15 to 1.64 mm week⁻¹ from the less permeable units (absence of lawn + impermeable sidewalk) to the more permeable units (presence of lawn + permeable sidewalk). Urban runoff quality and quantity were locally affected by the tree pits. This indicates that the increase in surface permeability and SOM in street tree pits is advisable. Street tree pits have the potential as bioretention units to locally mitigate some of the impacts of urbanization. City planners could consider the use of street tree pits as bioretention units to help the management of urban runoff.

The California Department of Pesticide Regulation conducted indoor air monitoring to estimate sulfury fluoride (SO₂F₂) emissions that bystanders around fumigated houses were potentially exposed to during structural fumigation of residential houses. Monitoring was conducted for 23 fumigations between September 2014 and March 2015. The SO₂F₂ indoor concentrations were measured from four locations inside the fumigated houses once an hour. The decreases of indoor concentrations are due to gas leakage (treatment period) and aeration (aeration period) from the structure to the outdoor environment. Analysis on the monitoring data showed considerable variability of half loss time (11–60 h) and mass loss (22–81%) during treatment periods. The decline of indoor concentrations followed the first-order kinetics; therefore, the hourly flux (g/m²s) of a treatment period can be calculated using initial SO₂F₂ concentration, treatment period mass loss, and house height. Although the California Aeration Plan requires a minimum 12–24 h of aeration after a treatment, the monitoring data showed that 93 ± 5% of the mass at the end of the treatment periods was emitted through the ducting system within the first 2 h. The average ratio of the loss amount in the first hour to the loss in the second was 6:1. These monitoring results provided the critical input for the computer modeling to estimate bystander exposure during structural fumigations of residential houses.

Despite the Mediterranean Sea basin is among the most sensitive areas over the world for climate change and air quality issues, it still remains less studied than the oceanic regions. The domain investigated by the research ship Minerva Uno cruise in Summer 2015 was the Tyrrhenian Sea. An overview on the marine boundary layer (MBL) concentration levels of carbonyl compounds, ozone (O₃), and sulfur dioxide (SO₂) is reported. The north-western Tyrrhenian Sea samples showed a statistically significant difference in acetone and SO₂ concentrations when compared to the south-eastern ones. Acetone and SO₂ values were higher in the southern part of the basin; presumably, a blend of natural (including volcanism) and anthropogenic (shipping) sources caused this difference. The mean acetone concentration reached 5.4 μg/m³; formaldehyde and acetaldehyde means were equal to 1.1 μg/m³ and 0.38 μg/m³, respectively. Maximums of 3.0 μg/m³ for formaldehyde and 1.0 μg/m³ for acetaldehyde were detected along the route from Civitavecchia to Fiumicino. These two compounds were also present at levels above the average in proximity of petrol-refining plants on the coast; in fact, formaldehyde reached 1.56 μg/m³ and 1.60 μg/m³, respectively, near Milazzo and Augusta harbors; meanwhile, acetaldehyde was as high as 0.75 μg/m³ at both sites. The levels of formaldehyde agreed with previously reported measurements over Mediterranean Sea and elsewhere; besides, a day/night trend was observed, confirming the importance of photochemical formation for this pollutant. According to this study, Mediterranean Sea basin, which is a closed sea, was confirmed to suffer a high anthropic pressure impacting with diffuse emissions, while natural contribution to pollution could come from volcanic activity, particularly in the south-eastern Tyrrhenian Sea region.

This article presents a review of the main physical, chemical, electrochemical, and biological technologies used for treating heavy metals in the wastewater of industrial processes and in synthetic aqueous solutions which could be applied to leachate from landfills. This paper outlines the generalities, operating principles, and modifications made to the technologies described. It discusses and assesses which of these have better removal rates and higher levels of efficiency in minimizing the heavy metal concentrations contained in leachates, such as mercury, chromium, lead, nickel, and copper among others. The first part of the document presents the so-called conventional technologies, such as chemical, physical, and electrochemical treatment. These have been used to treat different wastewater, especially industrial waste, operating adequately from the technical topic, but with high costs and the secondary products’ production. The second part exposes biological treatments tend to be most widely used due to their versatility, effectiveness, and low cost, when compared with traditional technologies. It is important to note that there is no single treatment and that each of the technologies reviewed has different heavy metal decontamination rates. All technologies search to reduce concentrations of heavy metals to values that are safe for the natural resources where they are discharged or disposed, thereby complying with the regulatory limits regulated in each of the regions.

The aim of this paper is to select feasible agricultural straws as high-quality sustained-release carbon source and examine the effect of determined agricultural organic waste on improving denitrification efficiency. Five kinds of agricultural straws, i.e., the rice straw, the corn straw, the wheat straw, the broomcorn straw, and the reed straw, were evaluated in a self-designed drawer-type biological filter. Results showed that the contents of C, H, and N in the five straws were 34.0~41.0%, 4.9~5.4%, and 1.1~1.5% respectively. The highest TOC release capacity of the rice straw was 12.4 ± 1.3 mg g⁻¹ and the average TOC release of other waste straws ranged from 6.0 to 9.2 mg g⁻¹. The TN release capacities of all the five straws were at a low level, ranging from 0.2 to 1.4 mg g⁻¹. Preliminary denitrification studies showed that the corn and the rice straw could be used as high-quality carbon sources, achieving a COD removal rate of 47.3~50.2% and a TN removal rate of 21.8~24.8% for wastewater with low C/N ratio. The rice straw and the corn straw founctioned both as favorable solid carbon sources and biofilm carriers; the carbon source quality of the corn straw lixivium is more beneficial to microbial utilization. The drawer-type biological filter has showed a good efficiency of denitrification for nitrogen removal when using agricultural straws as biofilm carriers.

Controlled-release fertilizers (CRFs) are an effective approach in providing essential nutrients for plant growth while minimizing the loss of nutrients in water and air, reducing contamination risks. However, commercial CRFs often release nutrients either too quickly or slowly due to the properties of their coating materials (polymer or sulfur). In this work, a novel CRF technology was developed using chitosan (CS) and graphene oxide (GO) nanocomposites as coating materials. CS and GO solutions were applied at varying ratios in preparing different nanocomposites. CS and GO formed homogeneous nanocomposite films through their interactions with each other. Fertilizer beads were successfully encapsulated by the CS-GO films using the simple dipping method. Resulting CRFs showed controlled-release behaviors, with nutrient release lasting for about a week. Although additional investigations are required for further evaluation and optimization, this method presents a promising concept for an alternative fertilizer-coating technology.