Real-time control technology for enhancing biofiltration performances and ecosystem functioning of decentralized bioretention cells.

Urban stormwater management has become a major issue over the last decades for flood prevention as well as water resource preservation. The development of green infrastructures such as bioretention systems since the 1990s has often been reported as an effective means of runoff mitigation with subsequent conveyed pollutant capture. Nevertheless, climate change involving more frequent extreme weather events as well as the variety of emerging pollutants in urban runoff have put an increasing strain on bioretention processes. Within this context, this mini-review deals with the opportunity of upgrading vegetated bioretention systems with active control technology to enhance their pollutant treatment capacity through proper control of critical bioretention operational variables and relying on improved ecological functioning and resilience. It is envisioned that such nature-based solutions hybridized with real-time control technology would help to improve stormwater reuse for more sustainable urban water management within the nexus of water-energy-food and greenhouse gases in future cities.

Supporting evidences for vegetation-enhanced stormwater infiltration in bioretention systems: a comprehensive review.

Stormwater mitigation efficiency of bioretention systems relies for a large part on their capacity to infiltrate rapidly received runoff. Within this context, the primary aim of this literature review was to clarify the vegetation influences on bioretention media hydraulic conductivity, with the ultimate goal of improving guidance on plant choice for system durability. A thorough synthesis of studies dealing with the comparison of plant species, functional types, or traits on infiltration-related processes in biofilters was achieved. Overall, results converged to a positive impact of plants on water infiltration and percolation, either under greenhouse or field conditions. In most cases, vegetation selection had a determining role in maintaining initial media infiltration rates, with in terms of improvement: turfgrass < prairie grass < shrubs < trees. Wind-induced movements of rigid foliage or stems are believed to avoid complete surface clogging. Species with thick, rhizomatous or fleshy (with maximum root diameter near the centimeter range), and tap or deep root systems could be preferred to maximize infiltration rates in permeable bioretention media. In fine-textured soils, higher specific root length, root length density, or mass density could also enhance infiltration. Root mass densities (0.1-2.2 kg.m3) were positively linked with infiltration rates in unlined systems while roots around 1 mm diameter would favor macropore-related preferential flows and increased hydraulic conductivity. Finally, implementation of high-diversity plant communities would ensure the presence of a more functionally rich vegetation community with species possessing adequate physiological adaptations (including root system architecture) to local environmental conditions for perennial cover and proper bioretention hydrological functioning.

Not merely noxious? Time-dependent hormesis and differential toxic effects systematically induced by rare earth elements in Escherichia coli.

Progressive rare earth element (REE) enrichment in aquatic environments worldwide and their resulting anthropogenic anomalies have highlighted the need for a better understanding of their biological effects, with a special emphasis on microbial cells since they play a crucial role in good ecosystem functioning. Therefore, the primary aim of this work was to achieve simultaneous characterization of the 16 REE toxicity effects on the growth kinetics of the commonly found Gram-negative bacterium E. coli (BW25113 strain). Bacterial growth curve modelling showed hormetic effects in the presence of REEs, while EC50 determination (in the mid-log phase) indicated that the four HREEs from Er to Lu in addition to Y were the most toxic metals (EC50 in the range of 8.3 to 3 µM), just after Sc (EC50 of 1.1 µM). Additional subcellular parameter assessment revealed cell membrane lipid peroxidation as well as enhanced membrane depolarization and permeability in the presence of La, Gd, or Yb as representatives of LREEs and HREEs. These subcellular effects appeared to be more intense with Gd and Yb compared with La-exposed cells, in relation to the overall higher toxicity potential reported for HREEs on bacterial growth. Also, the cellular ATP production decreased after REE exposure at their EC50. Finally, these results emphasize the importance of growth kinetic consideration as well as the complexity of REE biological effect mechanisms towards bacteria.

Evaluation of two contrasted activated carbon-based sequestration strategies to reduce soil-bound chlordecone bioavailability in piglets.

Chlordecone (Kepone) (CLD) is a highly persistent pesticide formerly used in the French West Indies. High levels of this pesticide are still found in soils and represent a subsequent source of contamination for outdoor-reared animals which may ingest involuntary non negligible amounts of soil. In that context, sequestering matrices like activated carbons (ACs) may be used to efficiently decrease the bioavailability of such organic pollutants. The present study intends to assess the respective efficiency of two sequestering strategies where two different ACs were provided either via feed incorporation or via soil amendment. This study involved 20 piglets randomly distributed into 5 experimental groups (4 replicates). All groups were exposed to 10 µg of CLD per kg of BW per day during 10 days via a contaminated soil. In both "Soil-ACs" treatment groups, the contaminated soil was amended by 2% (mass basis) of one of the two ACs. The two "Feed-ACs" groups received the contaminated soil and one dough ball containing 0.5% (mass basis) of one of the ACs. The piglets were then euthanized before collection of pericaudal adipose tissue and the whole liver and CLD analysis. A significant decrease of CLD concentrations in liver and adipose tissue was observed only in the "Soil-ACs" groups in comparison with the control group (P < 0.001). This decrease was particularly important for the coconut shell activated carbon where relative bioavailability was found lower than 1.8% for both tissues.

Contrasted effects of an anti-cyanobacterial ultrasound device on the non-target freshwater invertebrate species Gammarus roeseli.

The aim of this work was to investigate the effects of an anti-cyanobacterial ultrasound device (supplied by an electrical power of 15 W and emitting at 23 and 46 kHz) on the widespread freshwater amphipod species Gammarus roeseli. First, laboratory scale experiments in 8-L glass tanks showed that an ultrasound exposure of 2 h and 40 min was sufficient to produce 50% mortality, along with a 6.5 °C water temperature increase. Avoiding excessive heating by using a water-cooling and recirculation system permitted an exposure time of 29 h for the same mortality rate. A potential relationship between temperature's rise and amphipod mortality was hence highlighted. Moreover, the use of plastic mesh bag (0.5 mm mesh size) as a physical barrier has not shown any lethal effects of ultrasound exposure. Furthermore, the induction of GPx or GST activity as oxidative stress biomarkers was not observed. This could be explained by reduced ultrasound intensity inside the mesh bags. Thus, according to these results, the tested ultrasound system is not expected to be acutely harmful in the field.

Sublethal effect assessment of a low-power and dual-frequency anti-cyanobacterial ultrasound device on the common carp (Cyprinus carpio): a field study.

The use of ultrasonication for cyanobacterial control in freshwater bodies has become increasingly popular during the last decades despite controversial efficiency on large scale application. Apart from that, little information is currently available regarding ultrasound toxicity potential towards non-target species. This work was designed to address this issue in the common carp using a low-power (7-9 W output) and dual-frequency (23 and 46 kHz) anti-cyanobacterial ultrasound device. Results showed that carps were unaffected by ultrasound exposure when exposed in floating cages in fish ponds over a 30-day period. The experiment duration was the main factor influencing all measured biological parameters in exposed and non-exposed organisms. Indeed, it was positively associated with an increase in fish condition factor. Cortisol level also tended to slightly increase over the number of days of experiment but its variation did not enable to sort out any ultrasound exposure-related stress. Moreover, an overall diminution along the experimental period of the expression level of a set of biomarkers could be reported, encompassing cellular antioxidant enzyme activities such as superoxide dismutase (SOD), glutathione peroxydase (GPx), catalase and glutathione S-transferase (GST), and lactate dehydrogenase activity. Subtle changes in these biomarkers were dependent of the type of enzyme activity and especially of the origin of fish (i.e., sampled pond) regardless of the presence of ultrasound equipment, reflecting thereby fish adaptation to local environmental conditions in each pond. In conclusion, this study does not provide indication that ultrasonication in the aforementioned conditions affects the welfare and physiological homeostasis of carps.

Influence of waterborne gallic and pelargonic acid exposures on biochemical and reproductive parameters in the zebrafish (Danio rerio).

Gallic and pelargonic acids are biologically derived substances receiving a growing interest as eco-friendly biocides with potential applications in freshwater system management. However, some data gaps remain to address their chronic ecotoxicity issue, particularly for fish. This work aimed at investigating the sublethal effects of a long-term waterborne exposure of zebrafish to these compounds. Mature fish were exposed to gallic or pelargonic acid at the concentrations of 0, 0.05, 0.5 and 5 mg/L during one month under semi-static conditions. Fecundity, hatching rate and median hatching time were regularly evaluated. Circulating sex hormone levels (11 ketotestosterone -11 KT, 17 ßestradiol -E2-), plasma vitellogenin (Vtg), and gonad histology were monitored in males and females after exposure. Lactate dehydrogenase (LDH), total glutathione peroxydase (GPx) and glutathione-S transferase (GST) activities were assessed as enzymatic biomarkers of exposure in fish liver. Significant increases of GPx activity were reported in females exposed to both type of chemicals regardless the contamination level. Moreover, 5 mg/L gallic acid induced a decrease in 11-KT levels for males. For fish exposed to pelargonic acid, decreases in circulating hormone levels were reported respectively at 0.05 and 5 mg/L for 11-KT in males, and at 0.5 mg/L for E2 in females. However, no histological alteration in gonads neither significant variation in reproductive performances were detected following zebrafish exposure to gallic or pelargonic acid. Additional investigations concerning the mode of application and the environmental fate of these substances may warrant their further use in freshwater systems at concentrations compatible with biocidal/allelochemical effects. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 227-240, 2017.

Allelopathic potential and ecotoxicity evaluation of gallic and nonanoic acids to prevent cyanobacterial growth in lentic systems: A preliminary mesocosm study.

The increase in anthropogenic nutrient loading affecting many freshwater ecosystems combined with global warming may lead to cyanobacterial blooms on an increasingly frequent basis. Among the various physicochemical and biological methods which have been proposed to rapidly control blue-green algae growth, the use of plant-derived substances such as allelochemicals has gained great interest as an environment-friendly approach. The primary aim of this work was to evaluate the efficiency of gallic and nonanoic acid application to preemptively inhibit cyanobacterial growth in lentic hydrosystems. In order to address the process feasibility under realistic exposure scenarios, thirteen outdoor freshwater mesocosms (unit volume: 3m(3)) were designed, each containing phytoplankton (including local blue-green algae species) and various non-target organisms from higher trophic levels (Physa, Lymnaea, Gammarus, and Scardinius erythrophthalmus). After an 8-week mesocosm stabilization period, a full factorial design based on the presence/absence of gallic acid (GA) and nonanoic acid (NA) (including a control group) was implemented into the exposure tanks. Regular monitoring of major phytoplankton taxa was conducted during a 28-day experiment using an on-line fluorometer. The main results suggested that gallic acid was more efficient than nonanoic acid at limiting cyanobacterial growth at concentrations as low as 1 mg L(-1). Successive gallic acid applications (at 1, 2 and 4 mg L(-1)) at the early stages of cyanobacterial growth did not allow the complete elimination of blue-green algae from the mesocosms. However, the specificity of the allelopathic effect of gallic acid towards cyanobacteria was compatible with the maintenance of a primary productivity in the treated tanks as indicated by the photoautotrophic growth of other algal taxa. Finally, no biomarker induction signal could be reported in non-target species. Further gallic acid application trials in lentic systems such as small freshwater ponds may help to design innovative allelopathy-based aquatic ecotechnologies.

Acute toxicity and sublethal effects of gallic and pelargonic acids on the zebrafish Danio rerio.

Gallic and pelargonic acids are naturally found in a variety of plants and food products. Despite their extensive use in man-made applications, little is known regarding their potential risks to aquatic vertebrates. The aim of this work was to assess the acute toxicity of these polyphenolic and fatty acid compounds to the zebrafish. In order to get insights into sublethal effects, the enzyme activity of usual biomarkers related to oxidative stress and biotransformation were also assessed in fish. These latter included total superoxide dismutase, catalase as well as total glutathione peroxidase for antioxidant defence mechanisms and glutathione S-transferase for biotransformation related enzyme. Gallic acid was practically non-toxic (96-h lethal concentration (LC50) > 100 mg/L) whereas pelargonic acid was slightly toxic (96-h LC50 of 81.2 mg/L). Moreover, biomarker analyses indicated enhanced superoxide dismutase activity in fish exposed to 20, 40 and 100 mg/L of gallic acid compared to control. A dose-dependent induction of glutathione peroxidase and glutathione S-transferase was reported following gallic acid exposure at the tested concentrations of 10, 20 and 40 mg/L, with the exception of 100 mg/L of substance where basal activity levels were reported. In the case of pelargonic acid, there was no change in antioxidant enzyme activity while an inhibition of glutathione S-transferase was observed from organisms exposed to 45, 58 and 76 mg/L of test solution. The results concerning sublethal effects on biological parameters of zebrafish highlighted thereby the need for further investigations following chronic exposure to both organic acids.

Hemocyte responses of Dreissena polymorpha following a short-term in vivo exposure to titanium dioxide nanoparticles: preliminary investigations.

The widespread use of titanium-based nanoparticles and their environmental release may pose a significant risk to aquatic organisms within freshwater ecosystems. Suspension-feeder invertebrates like bivalve molluscs represent a unique target group for nanoparticle toxicology. The aim of this work was to investigate the short-term responses of Dreissena polymorpha hemocytes after in vivo exposure to titanium dioxide nanoparticles (TiO(2) NP). For this purpose, freshwater mussels were exposed to P25 TiO(2) NP at the concentrations of 0.1, 1, 5 and 25mg/L during 24h. Viability, phagocytosis activity and mitogen activated protein kinase (MAPK) phosphorylation level of ERK 1/2 and p38 in hemocytes extracted from exposed mussels were compared to those from control specimens. Results demonstrated an inhibition of the phagocytosis activity after exposure to TiO(2) NP at 0.1 and 1mg/L. Similar trends, albeit less pronounced, were reported for higher concentrations of NP. Transmission electron microscopy showed for the first time the internalization of TiO(2) NP into Dreissena polymorpha hemocytes. Besides, exposure to NP increased the ERK 1/2 phosphorylation levels in all treatments. Concerning the phosphorylation level of p38, only exposures to 5 and 25mg/L of NP induced significant p38 activation in comparison to that of the control. Finally, these short-term effects observed at environmentally relevant concentrations highlighted the need for further studies concerning ecotoxicological evaluation of nanoparticle release into an aquatic environment.

Contribution of Miscanthus x giganteus root exudates to the biostimulation of PAH degradation: an in vitro study.

Phytoremediation is considered as a promising and cost-effective method to enhance bioremediation of polluted soils. Exudation of plant root secondary metabolites similar to organic pollutants may induce the expression of microbial degradative enzymes and favour cometabolism of xenobiotics. We investigated the contribution of Miscanthus x giganteus root exudates in the biostimulation of PAH-degradation. This perennial grass was chosen because of its capability to grow on polluted soils and its high biomass production for non-food purposes. First, the impact of cometabolism phenomena was evaluated on the selective enrichment of pyrene-degrading bacterial consortia. The identification of each isolated strains following incubation with pyrene only, "pyrene+phenanthrene", "pyrene+salycilate" or "pyrene+diesel fuel" showed a varying bacterial diversity and pyrene-degrading ability, depending on the co-substrate used. Then, a microplate assay was designed, based on the simultaneous measurement of bacterial consortia growth and degradation activity, in the presence of PAH and total root exudates. Results showed that i) the addition of root exudates was efficient for promoting bacterial growth, ii) but a selective enrichment of PAH-degraders compared to aliphatic ones could be clearly demonstrated, thereby conducing to an enhanced PAH catabolism. The identification of plant secondary metabolites showed the presence of a broad range of flavonoid-derived compounds that could play a role in cometabolic processes. Microplate assays with the two major molecules, quercetin and rutin, suggested a partial involvement of these compounds in biostimulation processes. Further investigations with the other identified secondary metabolites (apigenin, isovitexin, catechin, gallic and caffeic acid) should provide more information on the exudate-PAH cometabolic degradation phenomenon.