Blue-green algae bloom is of great concern globally since they adversely affect the water ecosystem and also drinking water treatment processes. This work investigated the removal of Microcystis aeruginosa (M. aeruginosa) by combining the conventional coagulant polyaluminum chloride (PACl) with nano-Fe₃O₄ particles as a coagulant aid. The results showed that the addition of nano-Fe₃O₄ significantly improved the removal efficiency of M. aeruginosa by reducing the amount of PACl dosage and simultaneously hastening the sedimentation. At the M. aeruginosa density of an order of magnitude of 10⁷, 10⁶, and 10⁵ pcs/mL, respectively, the corresponding PACl dose of 200, 20, and 2 mg/L and the mass ratio of PACl to nano-Fe₃O₄ of 4:1, the removal efficiency of M. aeruginosa could be increased by 33.0, 44.7, and 173.1 %, respectively. Compared to PACl, PACl combined with the nano-Fe₃O₄ as a coagulant aid had higher removal efficiency at a wider pH range. SEM images showed that nano-Fe₃O₄ first combined with PACl to form clusters and further generated the flocs with algae. Results from the laser particle analyzer further suggested that the floc size increased with the addition of nano-Fe₃O₄. It was noted that the addition of nano-Fe₃O₄ led to aluminum species change after PACl hydrolyzed in the algae solution, from Alₐ to Alb and Alc subsequently. As a coagulant aid, the nano-Fe₃O₄, in conjunction with PACl, apparently provided nucleation sites for larger flocs to integrate with M. aeruginosa. In addition, increased floc density improved the removal of M. aeruginosa.

This study was conducted to determine whether phytoscreening techniques could be used to characterize the distribution of Hg in soil at the South River, VA. An estimated 500 to 1000 kg of Hg was released to the South River in the 1930s and 1940s from a synthetic fiber manufacturing plant located in Waynesboro, contaminating the floodplain downstream. Under background conditions (soil Hg <0.03 μg/g), phytoscreening sample Hg concentrations ranged from 1.9 to 3.9 ng/g. With soil Hg concentrations ranging from 0.1 to 94 μg/g in the top 30.5 cm of nearby soil, phytoscreening sample Hg concentrations ranged from 5.0 to 145 ng/g. The variability of Hg concentrations in soil solution over the scale of the entire rhizosphere of the large trees sampled was likely high. Furthermore, the mean depth of water uptake and the exact proximity of the soil profile samples for each tree could not be determined. Nevertheless, the phytoscreening results of this study could be used to reliably provide a qualitative delineation of Hg-contaminated soil.

Soil pollution with heavy metals is an increasingly serious threat to the environment, food security, and human health. Therefore, it is urgent to develop economic and highly efficient soil restoration technology for environmental improvement; phytoremediation is an option that is safe, has low cost, and is environmentally friendly. However, in selecting hyperaccumulators or tolerant plants, theories and operation technologies for optimal restoration should be satisfied. In this study, the switchgrass growth response and performance of phytoextraction under the coupling effect of Cd and pH were investigated by evaluating seed germination, seedling growth, and the Cd content in the plant to evaluate the potential use of switchgrass as a phytoremediation plant in cadmium contaminated soil. This study conducted three sets of independent experiments with five levels of Cd concentrations, including two orthogonal matrix designs of combining Cd with pH values. The results showed that switchgrass was germinated well under all treatments (Cd concentration of 0–500 μM), but the seedling growth was significantly affected by Cd and pH, as shown by multivariate regression analyses. Hormesis was found during the growth of switchgrass plants exposed to low Cd concentrations under hydroponic conditions, and switchgrass plants were capable of developing with a Cd concentration of 100–175 μM and pH of 4.1–5.9. Mild acidic conditions can enhance the ability of Cd to accumulate in switchgrass. Switchgrass was moderately tolerant to Cd and may be used as a phytoremediation plant for Cd-contaminated soils in the future. Our results also suggest that hormetic effects should be taken into consideration in the phytoremediation of Cd-contaminated soils. We discuss the physiological and biochemical mechanisms contributing to the effective application of the plant for the phytoremediation of Cd-contaminated soils.

Several studies have pointed to the potential benefits of riparian vegetation as buffer zones for agricultural and industrial pollutants harmful to aquatic ecosystems. However, other studies have called into question its use as an ecological filter, questioning the widths and conditions for which they are effective as a filter. In this work, we have investigated the buffering capacity of the riparian one to retain pesticides in the water-saturated zone, on 27 sites composed by riparian buffer zones with different vegetation structure (woody, shrubs, or grass vegetation) and width (12, 36, and 60 m). Five pesticides were analyzed. The effectiveness of the filtering was largely influenced by the width and vegetation type of the buffer zone. In general, decreasing pesticide removal followed in this order wood > shrubs > grass. The 60 m woody buffer zone was the most effective in the removal of all the pesticides. Only atrazine was detected in this case (0.3 μg L⁻¹). Furthermore, a linear correlation (R ² > 0.97) was observed in their removal for all compounds and buffer zones studied. Thus, preserving the woody vegetation in the riparian zone is important for watershed management and groundwater quality in the no-tillage system in temperate climate.

The cyanobacterium Synechocystis sp., an isolate from polluted water of Satluj river, India, was found resistant to chromium(VI) up to 200 nmol mL⁻¹. In this study, it has been demonstrated that this organism takes up Cr(VI) through a phosphate transporter. The organism removed 250 nmol Cr(VI), 210 nmol phosphate and 180 nmol sulphate mg⁻¹ protein from a buffer solution in 8 h. Cr(VI) uptake by the organism decreased to 135 nmol Cr(VI) removed per milligram protein in the presence of 200 nmol phosphate mL⁻¹, but the same concentration of sulphate did not affect the Cr(VI) uptake. Similarly, the presence of Cr(VI) in the solution affected the phosphate uptake but not sulphate uptake by the test organism. The kinetic studies on Cr(VI) uptake in the presence of phosphate revealed that phosphate and Cr(VI) acted as competitive inhibitors for one another. Phosphate-starved cells of the organism removed more amount of Cr(VI) than the basal medium-grown cells. The uptake of Cr(VI) as well as phosphate by the organism was observed to be a light-dependent process. Cinnamic acid, a phosphate transporter inhibitor, inhibited Cr(VI) uptake by the organism. Results clearly demonstrated that the test organism takes up chromate ions by phosphate transporter and not by the sulphate transporter. This organism is thus a potential candidate for the bioremediation of Cr(VI) from Cr(VI) and sulphate-laden water.

Little information is available on the role of glycinebetaine (GB) in chromium (Cr) tolerance while Cr toxicity is widespread problem in crops grown on Cr-contaminated soils. In this study, we investigated the influence of GB on Cr tolerance in wheat (Triticum aestivum L.) grown in sand and soil mediums. Three concentrations of chromium (0, 0.25, and 0.5 mM) were tested with and without foliar application of GB (0.1 M). Chromium alone led to a significant growth inhibition and content of chlorophyll a, b, proteins and enhanced the activity of antioxidant enzymes. Glycinebetaine foliar application successfully alleviated the toxic effects of Cr on wheat plants and enhanced growth characteristics, biomass, proteins, and chlorophyll contents. Glycinebetaine also reduced Cr accumulation in wheat plants especially in grains and enhanced the activity of antioxidant enzymes in both shoots and roots. This study provides evidence that GB application contributes to decreased Cr concentrations in wheat plants and its importance in the detoxification of heavy metals.

Dermal absorption of the herbicide chlorotoluron was measured using ex vivo pig skin in Franz diffusion cells in an automated system. The steady-state flux was calculated, as well as the permeability coefficient, which is 0.0038 cm h⁻¹. The permeability coefficient (Kₚ) is a key factor when predicting human health risks resulting from dermal exposition to a substance. The experimental determination of this parameter filled data gaps regarding the dermal absorption of chlorotoluron. The experimental permeability coefficient was subsequently used to calculate the dermal absorbed dose during some exposure scenarios. Reference doses were revised, and screening risk assessment process was done to calculate the risks resulting from exposure to chlorotoluron. This refined new approach proved to be a useful tool for human health risk assessment in the areas with these herbicide applications. Graphical Abstract An experimentally refined tool to assess the risks of the human dermal exposure to herbicide chlorotoluron - graphical abstract.

This study examines a matrix of synthetic water samples designed to include conditions that favour brominated disinfection by-product (Br-DBP) formation, in order to provide predictive models suitable for high Br-DBP forming waters such as salinity-impacted waters. Br-DBPs are known to be more toxic than their chlorinated analogues, in general, and their formation may be favoured by routine water treatment practices such as coagulation/flocculation under specific conditions; therefore, circumstances surrounding their formation must be understood. The chosen factors were bromide concentration, mineral alkalinity, bromide to dissolved organic carbon (Br/DOC) ratio and Suwannee River natural organic matter concentration. The relationships between these parameters and DBP formation were evaluated by response surface modelling of data generated using a face-centred central composite experimental design. Predictive models for ten brominated and/or chlorinated DBPs are presented, as well as models for total trihalomethanes (tTHMs) and total dihaloacetonitriles (tDHANs), and bromide substitution factors for the THMs and DHANs classes. The relationships described revealed that increasing alkalinity and increasing Br/DOC ratio were associated with increasing bromination of THMs and DHANs, suggesting that DOC lowering treatment methods that do not also remove bromide such as enhanced coagulation may create optimal conditions for Br-DBP formation in waters in which bromide is present.

Air and fallout samples were collected seasonally in an e-waste polluted region in southeast of China in 2013–2014. The annual polybrominated diphenyl ethers (PBDEs) concentrations in air and fallout samples were 200 ± 162 pg m⁻³ and 320 ± 255 ng g⁻¹, respectively. The deposition flux calculated from the fallout concentration was 110 ± 77.3 ng m⁻² day⁻¹. The PBDE levels and deposition fluxes of the samples deployed within the e-waste central area were three to four times higher than those in the surrounding area. The congener profiles in the air samples could be commonly found in commercial penta-BDE mixtures. BDE209 was the most dominant congener in fallout samples. Debromination processes were confirmed to occur both in the air and fallouts due to the minor amounts or inexistence of some congeners in technical PBDE products. The highest gaseous PBDE concentration was found during the summer while lowest during the autumn. PBDE concentration in fallouts turned up higher in the cold months while lower in the warm months. The similarity of deposition fluxes at sites in the e-waste central area indicated a steady PBDE emission source, whereas the significant relationship between deposition fluxes and particle weights at sites in the e-waste surrounding area suggested the scavenging of PBDEs in this area was largely associated with particles.

Endogenous phosphorus (P) release from sediments is an important factor to cause eutrophication and, hence, algal bloom in lakes in China. Algal decomposition depletes dissolved oxygen (DO) and causes anaerobic conditions and therefore increases P release from sediments. As sediment P release is dependent on the iron (Fe) cycle, electron acceptors (e.g., NO₃ ⁻, SO₄ ²⁻, and Mn⁴⁺) can be utilized to suppress the reduction of Fe³⁺ under anaerobic conditions and, as such, have the potential to impair the release of sediment P. Here, we used a laboratory experiment to test the effects of FeCl₃, MnO₂, and KNO₃ on soluble reactive phosphorus (SRP) concentration and related chemical variables in the overlying water column during algal decomposition at different algal densities. Results showed that algal decomposition significantly depleted DO and thereby increased sediment Fe-bound P release. Compared with the control, addition of FeCl₃ significantly decreased water SRP concentration through inhibiting sediment P release. Compared with FeCl₃, addition of MnO₂ has less potential to suppress sediment P release during algal decomposition. Algal decomposition has the potential for NO₃ ⁻ removal from aquatic ecosystem through denitrification and by that alleviates the suppressing role of NO₃ ⁻ on sediment P release. Our results indicated that FeCl₃ and MnO₂ could be efficient in reducing sediment P release during algal decomposition, with the strongest effect found for FeCl₃; large amounts of NO₃ ⁻ were removed from the aquatic ecosystem through denitrification during algal decomposition. Moreover, the amounts of NO₃ ⁻ removal increased with increasing algal density.