Total staphylococci as performance surrogate for greywater treatment

Faecal indicator bacteria (FIB) are commonly used as water quality indicators; implying faecal contamination and therefore the potential presence of pathogenic enteric bacteria, viruses, and protozoa. Hence in wastewater treatment, the most commonly used treatment process measures (surrogates) are total coliforms, faecal coliforms, Escherichia coli (E. coli), and enterococci. However, greywater potentially contains skin pathogens unrelated to faecal load, and E. coli and other FIB may grow within greywater unrelated to pathogens. Overall, FIB occurs at fluctuating and relatively low concentrations compared to other endogenous greywater bacteria affecting their ability as surrogates for pathogen reduction. Therefore, unlike municipal sewage, FIB provides a very limited and unreliable log-reduction surrogate measure for on-site greywater treatment systems. Based on our recent metagenomic study of laundry greywater, skin-associated bacteria such as Staphylococcus, Corynebacterium, and Propionibacterium spp. dominate and may result in more consistent treatment surrogates than traditional FIB. Here, we investigated various Staphylococcus spp. as potential surrogates to reliably assay over 4-log₁₀ reduction by the final-stage UV disinfection step commonly used for on-site greywater reuse, and compare them to various FIB/phage surrogates. A collimated UV beam was used to determine the efficacy of UV inactivation (255, 265 and 285 nm) against E. coli, Enterococcus faecalis, E. faecium, E. casseliflavus, Staphylococcus aureus, and S. epidermidis. Staphylococcus spp. was estimated by combining the bi-linear dose-response curves for S. aureus and S. epidermidis and was shown to be less resistant to UV irradiation than the other surrogates examined. Hence, a relative inactivation credit is suggested; whereas, the doses required to achieve a 4 and 5-log₁₀ reduction of Staphylococcus spp. (13.0 and 20.9 mJ cm^?2, respectively) were used to determine the relative inactivation of the other microorganisms investigated. The doses required to achieve a 4 and 5-log₁₀ reduction of Staphylococcus spp. resulted in a log₁₀ reduction of 1.4 and 4.1 for E. coli, 0.8 and 2.8 for E. faecalis, 0.8 and 3.6 for E. casseliflavus and 0.8 and 1.2 for MS2 coliphage, respectively. Given the concentration difference of Staphylococcus spp. and FIB (3 to 5-log₁₀ higher), we propose the use of Staphylococcus spp. as a novel endogenous performance surrogate to demonstrate greywater treatment performance given its relatively high and consistent concentration and therefore ability to demonstrate over 5-log₁₀ reductions.     

Treatment of Arctic wastewater by chemical coagulation,UV and peracetic acid disinfection

Conventional wastewater treatment is challenging in the Arctic region due to the cold climate and scattered population. Thus, no wastewater treatment plant exists in Greenland, and raw wastewater is discharged directly to nearby waterbodies without treatment. We investigated the efficiency of physicochemical wastewater treatment, in Kangerlussuaq, Greenland. Raw wastewater from Kangerlussuaq was treated by chemical coagulation and UV disinfection. By applying 7.5 mg Al/L polyaluminium chloride (PAX XL100), 73% of turbidity and 28% phosphate was removed from raw wastewater. E. coli and Enterococcus were removed by 4 and 2.5 log, respectively, when UV irradiation of 0.70 kWh/m³ was applied to coagulated wastewater. Furthermore, coagulated raw wastewater in Denmark, which has a chemical quality similar to Greenlandic wastewater, was disinfected by peracetic acid or UV irradiation. Removal of heterotrophic bacteria by applying 6 and 12 mg/L peracetic acid was 2.8 and 3.1 log, respectively. Similarly, removal of heterotrophic bacteria by applying 0.21 and 2.10 kWh/m³ for UV irradiation was 2.1 and greater than 4 log, respectively. Physicochemical treatment of raw wastewater followed by UV irradiation and/or peracetic acid disinfection showed the potential for treatment of arctic wastewater.     

Evaluation of the giant reed (<Emphasis Type="Italic">Arundo donax</Emphasis>) in horizontal subsurface flow wetlands for the treatment of recirculating aquaculture system effluent

Introduction

Two emergent macrophytes, Arundo donax and Phragmites australis, were established in experimental subsurface flow, gravel-based constructed wetlands (CWs) receiving untreated recirculating aquaculture system wastewater.

Materials and methods

The hydraulic loading rate was 3.75 cm day^?1. Many of the monitored water quality parameters (biological oxygen demand [BOD], total suspended solids [TSS], total phosphorus [TP], total nitrogen [TN], total ammoniacal nitrogen [TAN], nitrate nitrogen [NO₃], and Escherichia coli) were removed efficiently by the CWs, to the extent that the CW effluent was suitable for use on human food crops grown for raw produce consumption under Victorian state regulations and also suitable for reuse within aquaculture systems.

Results and discussion

The BOD, TSS, TP, TN, TAN, and E. coli removal in the A. donax and P. australis beds was 94%, 67%, 96%, 97%, 99.6%, and effectively 100% and 95%, 87%, 95%, 98%, 99.7%, and effectively 100%, respectively, with no significant difference (p?>?0.007) in performance between the A. donax and P. australis CWs. In this study, as expected, the aboveground yield of A. donax top growth (stems + leaves) (15.0?±?3.4 kg wet weight) was considerably more than the P. australis beds (7.4?±?2.8 kg wet weight). The standing crop produced in this short (14-week) trial equates to an estimated 125 and 77 t ?ha^?1 year^?1 biomass (dry weight) for A. donax and P. australis, respectively (assuming that plant growth is similar across a 250-day (September–April) growing season and a single-cut, annual harvest).

Conclusion

The similarity of the performance of the A. donax- and P. australis-planted beds indicates that either may be used in horizontal subsurface flow wetlands treating aquaculture wastewater, although the planting of A. donax provides additional opportunities for secondary income streams through utilization of the energy-rich biomass produced.

     

Use of halophytes in pilot-scale horizontal flow constructed wetland treating domestic wastewater

Recent findings encourage the use of halophytes in constructed wetlands for domestic wastewater treatment due to their special physiological characteristics as the ability to accumulate heavy metals and salts in their tissues makes them ideal candidates for constructed wetland vegetation. In this particular study, we investigated the application of halophytic plants in a horizontal flow constructed wetland for domestic wastewater treatment purposes. The pilot plant which was situated in Crete (Greece) was planted with a polyculture of halophytes (Tamarix parviflora, Juncus acutus, Sarcocornia perrenis, and Limoniastrum monopetalum). The system’s performance was monitored for a period of 11 months during which it received primary treated wastewater from the local wastewater treatment plant. Results show that halophytes developed successfully in the constructed wetland and achieved organic matter and pathogen removal efficiencies comparable to those reported for reeds in previous works (63% and 1.6 log units, respectively). In addition, boron concentration in the effluent was reduced by 40% in comparison with the influent. Salinity as expressed by electrical conductivity did not change during the treatment, indicating that the accumulation of salts in the leaves is not able to overcome electrical conductivity increasing due to evapotranspiration. The results indicate an improvement in the treatment of domestic wastewater via the use of halophyte-planted CWs.     

Visible light photocatalytic antibacterial activity of Ni-doped and N-doped TiO<Subscript>2</Subscript> on <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> and <Emphasis Type="Italic">Escherichia coli</Emphasis> bacteria

The Ni-doped and N-doped TiO₂ nanoparticles were investigated for their antibacterial activities on Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) bacteria. Their morphological features and characteristics such as particle size, surface area, and visible light absorbing capacity were compared and discussed. Scanning electron microscopy, X-ray diffraction, and UV–visible spectrophotometry were used to characterize both materials. The inactivation of E. coli (as an example of Gram-negative bacteria) and S. aureus (as an example of Gram-positive bacteria) with Ni-doped and N-doped TiO₂ was investigated in the absence and presence of visible light. Antibacterial activity tests were conducted using undoped, Ni-doped, and N-doped TiO₂. The N-doped TiO₂ nanoparticles show higher antibacterial activity than Ni-doped TiO₂. The band gap narrowing of N-doped TiO₂ can induce more visible light absorption and leads to the superb antibacterial properties of this material. The complete inactivation time for E. coli at an initial cell concentration of 2.7?×?10⁴ CFU/mL was 420 min which is longer than the 360 min required for S. aureus inactivation. The rate of inactivation of S. aureus using the doped TiO₂ nanoparticles in the presence of visible light is greater than that of E. coli. The median lethal dose (LD50) values of S. aureus and E. coli by antibacterial activity under an 18-W visible light intensity were 80 and 350 mg/ml for N-doped TiO₂, respectively.     

Comparison of experimental ponds for the treatment of dye wastewater under controlled and semi-natural conditions

This study compares the performance of simulated shallow ponds vegetated with Lemna minor L. under controlled and semi-natural conditions for the treatment of simulated wastewater containing textile dyes. The objectives were to assess the water quality outflow parameters, the potential of L. minor concerning the removal of chemical oxygen demand (COD) and four azo dyes (Acid blue 113, reactive blue 198, Direct Orange 46 and Basic Red 46) and the plants’ growth rate. Findings show that all mean outflow values of COD, total dissolved solids (TDS) and electrical conductivity (EC) were significantly (p < 0.05) lower within the outdoor compared to the indoor experiment except the dissolved oxygen (DO). The COD removal was low for both experiments. The outflow TDS values were acceptable for all ponds. The pond systems were able to reduce only BR46 significantly (p < 0.05) for the tested boundary conditions. Removals under laboratory conditions were better than those for semi-natural environments, indicating the suitability of operating the pond system as a polishing step in warmer regions. The mean outflow values of zinc and copper were below the thresholds set for drinking and irrigation waters and acceptable for L. minor. The dyes inhibited the growth of the L. minor.     

Micro-electrolysis/retinervus luffae-based simultaneous autotrophic and heterotrophic denitrification for low C/N wastewater treatment

Nitrogen bioremediation in organic insufficient wastewater generally requires an extra carbon source. In this study, nitrate-contaminated wastewater was treated effectively through simultaneous autotrophic and heterotrophic denitrification based on micro-electrolysis carriers (MECs) and retinervus luffae fructus (RLF), respectively. The average nitrate and total nitrogen removal rates reached 96.3 and 94.0% in the MECs/RLF-based autotrophic and heterotrophic denitrification (MRAHD) system without ammonia and nitrite accumulation. The performance of MRAHD was better than that of MEC-based autotrophic denitrification for the wastewater treatment with low carbon nitrogen (COD/N) ratio. Real-time quantitative polymerase chain reaction (qPCR) revealed that the relative abundance of nirS-type denitrifiers attached to MECs (4.9%) and RLF (5.0%) was similar. Illumina sequencing suggested that the dominant genera were Thiobacillus (7.0%) and Denitratisoma (5.7%), which attached to MECs and RLF, respectively. Sulfuritalea was discovered as the dominant genus in the middle of the reactor. The synergistic interaction between autotrophic and heterotrophic denitrifiers played a vital role in the mixotrophic substrate environment.     

<Emphasis Type="Italic">Ailanthus Altissima</Emphasis> and <Emphasis Type="Italic">Phragmites Australis</Emphasis> for chromium removal from a contaminated soil

The comparative effectiveness for hexavalent chromium removal from irrigation water, using two selected plant species (Phragmites australis and Ailanthus altissima) planted in soil contaminated with hexavalent chromium, has been studied in the present work. Total chromium removal from water was ranging from 55 % (Phragmites) to 61 % (Ailanthus). After 360 days, the contaminated soil dropped from 70 (initial) to 36 and 41 mg Cr/kg (dry soil), for Phragmites and Ailanthus, respectively. Phragmites accumulated the highest amount of chromium in the roots (1910 mg Cr/kg_{(dry tissue)}), compared with 358 mg Cr/kg_{(dry tissue)} for Ailanthus roots. Most of chromium was found in trivalent form in all plant tissues. Ailanthus had the lowest affinity for Cr^VI reduction in the root tissues. Phragmites indicated the highest chromium translocation potential, from roots to stems. Both plant species showed good potentialities to be used in phytoremediation installations for chromium removal.     

Simple technology for recycling phosphate from wastewater to farmland in rural areas

A simple technology for phosphate (P _i ) recovery has been developed using a bifunctional adsorption–aggregation agent. The bifunctional agent was prepared by soaking calcium silicates in hydrochloric acid solution. Importantly, recyclable calcium silicates were available almost free of charge from the cement industry and also from the steel industry. The acid treatment was essential not only for enhancing the ability of calcium silicates to remove P _i from aqueous solution but also for enabling the high settleability of removed P _i . On-site experiments using a mobile plant showed that approximately 80% P _i could be recovered from anaerobic sludge digestion liquor at a wastewater treatment plant. This technology has the potential to offer a simple, compact service for recycling P _i from wastewater to farmland in rural areas.     

Evaluation of cationic polyacrylamide-based hybrid coagulation for the removal of dissolved organic nitrogen

Dissolved organic nitrogen (DON) is an important component of aquatic environment of which amount impacts water quality. Thus, removal of DON has attracted wide attention. At present, it is difficult for common coagulation to remove DON from the aquatic environment. The cationic polymers can help to improve the removal efficiency of DON to some extent, but the underlying mechanism of the ascension is not clear. In order to grasp its removal behavior and further improve the removal efficiency of DON in the future, we evaluated the effect of a hybridized coagulant of polyacrylamide with iron-based coagulant on removal of aquatic DON. A higher floc growth rate (119.82 μm/min) and recovery factors (26.96) were found in the hybrid coagulation. The parameters affecting the DON and the dissolved organic carbon (DOC) included the molar ratio of Zn to Fe (n_Zn/n_Fe), CPAM content, and molar ratio of OH to Fe (n_OH/n_Fe): n_Zn/n_Fe had a larger influence in DON removal than CPAM content; CPAM had a larger influence in the DOC removal; n_OH/n_Fe played a moderate effect between CPAM and n_Zn/n_Fe. Mutual effect of hybrid coagulants indicated the colloidal species to be helpful in enhancing DOC and DON removal. Other parameters affecting coagulation performance included the pH: the estimated maximum DON removal efficiency occurred at pH 6, DOC removal efficiency at pH 8. The above results found in this study showed that DON removal was affected by the ingredient and the species composition of the hybrid coagulant, and the water environmental parameter. The enhanced efficiency of DON removal in the presence of CPAM was mainly attributed to the increased adsorption-bridging and sweep-floc.     

Heavy metal and trace elements in riparian vegetation and macrophytes associated with lacustrine systems in Northern Patagonia Andean Range

Vegetation associated with lacustrine systems in Northern Patagonia was studied for heavy metal and trace element contents, regarding their elemental contribution to these aquatic ecosystems. The research focused on native species and exotic vascular plant Salix spp. potential for absorbing heavy metals and trace elements. The native species studied were riparian Amomyrtus luma, Austrocedrus chilensis, Chusquea culeou, Desfontainia fulgens, Escallonia rubra, Gaultheria mucronata, Lomatia hirsuta, Luma apiculata, Maytenus boaria, Myrceugenia exsucca, Nothofagus antarctica, Nothofagus dombeyi, Schinus patagonicus, and Weinmannia trichosperma, and macrophytes Hydrocotyle chamaemorus, Isöetes chubutiana, Galium sp., Myriophyllum quitense, Nitella sp. (algae), Potamogeton linguatus, Ranunculus sp., and Schoenoplectus californicus. Fresh leaves were analyzed as well as leaves decomposing within the aquatic bodies, collected from lakes Futalaufquen and Rivadavia (Los Alerces National Park), and lakes Moreno and Nahuel Huapi (Nahuel Huapi National Park). The elements studied were heavy metals Ag, As, Cd, Hg, and U, major elements Ca, K, and Fe, and trace elements Ba, Br, Co, Cr, Cs, Hf, Na, Rb, Se, Sr, and Zn. Geochemical tracers La and Sm were also determined to evaluate contamination of the biological tissues by geological particulate (sediment, soil, dust) and to implement concentration corrections.     

Fate of antimicrobial resistance genes in response to application of poultry and swine manure in simulated manure-soil microcosms and manure-pond microcosms

This study aimed to determine the occurrence, abundance, and fate of nine important antimicrobial resistance genes (ARGs) (sul1, sul2, tetB, tetM, ermB, ermF, fexA, cfr, and Intl1) in the simulated soil and pond microcosms following poultry and swine manure application. Absolute quantitative PCR method was used to determine the gene copies. The results were modeled as a logarithmic regression (N?=?mlnt?+?b) to explore the fate of target genes. Genes sul1, Intl1, sul2, and tetM had the highest abundance following the application of the two manure types. The logarithmic regression model fitted the results well (R ² values up to 0.99). The reduction rate of all genes (except for the genes fexA and cfr) in manure-pond microcosms was faster than those in manure-soil microcosms. Importantly, sul1, intl1, sul2, and tetM had the lowest reduction rates in all the samples and the low reduction rates of tetM was the first time to be reported. These results indicated that ARG management should focus on using technologies for the ARG elimination before the manure applications rather than waiting for subsequent attenuation in soil or water, particularly the ARGs (such as sul1, intl1, sul2, and tetM investigated in this study) that had high abundance and low reduction rate in the soil and water after application of manure.     

Biodegradation of toluene vapor in coir based upflow packed bed reactor by <Emphasis Type="Italic">Trichoderma asperellum</Emphasis> isolate

In the present study, a new biofiltration system involving a selective microbial strain isolated from aerated municipal sewage water attached with coir as packing material was developed for toluene degradation. The selected fungal isolate was identified as Trichoderma asperellum by 16S ribosomal RNA (16S rRNA) sequencing method, and pylogenetic tree was constructed using BLASTn search. Effect of various factors on growth and toluene degradation by newly isolated T. asperellum was studied in batch studies, and the optimum conditions were found to be pH 7.0, temperature 30 °C, and initial toluene concentration 1.5 (v/v)%. Continuous removal of gaseous toluene was monitored in upflow packed bed reactor (UFPBR) using T. asperellum. Effect of various parameters like column height, flow rate, and the inlet toluene concentration were studied to evaluate the performance of the biofilter. The maximum elimination capacity (257 g m^?3 h^?1) was obtained with the packing height of 100 cm with the empty bed residence time of 5 min. Under these optimum conditions, the T. asperellum showed better toluene removal efficiency. Kinetic models have been developed for toluene degradation by T. asperellum using macrokinetic approach of the plug flow model incorporated with Monod model.     

Rapid biological synthesis of silver nanoparticles using <Emphasis Type="Italic">Leucas martinicensis</Emphasis> leaf extract for catalytic and antibacterial activity

A novel green approach for the synthesis and stabilization of silver nanoparticles (AgNPs) using water extract of Leucas martinicensis leaf has been developed. As obtained, the nanoparticles are characterized by UV-visible (UV-Vis), transmission electron microscope (TEM), and X-ray diffraction (XRD). The crystalline nature of the AgNPs is confirmed by the prominent peaks in the XRD pattern. FTIR spectra suggest that the possible biomolecules are responsible for the efficient stabilization of the sample. The effects of leaf quantity on the biosynthesis of AgNPs are investigated by UV-Vis spectrophotometer. The synthesized AgNPs are observed to have a good catalytic activity on the reduction of methylene blue by L. martinicensis leaf. This is confirmed by the decrease in absorbance maximum values of methylene blue with respect to time through UV-Vis spectrophotometer. Moreover, the antibacterial activity of synthesized AgNPs against Staphylococcus aureus, Bacillus subtilis, Salmonella typhi, and Escherichia coli are screened.     

2,3,7,8-TCDD-mediated toxicity in peripheral blood mononuclear cells is alleviated by the antioxidants present in <Emphasis Type="Italic">Gelidiella acerosa</Emphasis>: an in vitro study

Seaweeds have been used as a source of traditional medicine worldwide for the treatment of various ailments, mainly due to their ability to quench the free radicals. The present study aims at evaluating the protective effect of methanolic extract of Gelidiella acerosa, an edible red seaweed against 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced toxicity in peripheral blood mononuclear cells (PBMC). For evaluating the protective effect of G. acerosa, PBMC were divided into four groups: vehicle control, TCDD (10 nM), TCDD?+?G. acerosa (300 μg/ml), and G. acerosa alone treated. Scavenging of intracellular reactive oxygen species (ROS) induced by TCDD was assessed by the dichloro-dihydro-fluorescein diacetate (DCFH-DA) method. Alterations at macromolecular level were quantified through lipid peroxidation (LPO) level, protein carbonyl content (PCC) level, and comet assay. The cellular morphology upon TCDD toxicity and G. acerosa treatment was obtained by light microscopy and histopathological studies. The chemical composition present in the methanolic extract of G. acerosa was determined by gas chromatography-mass spectrometry (GC-MS) analysis. The results reveal that 10 nM TCDD caused significant (P?<?0.05) reduction in cell viability (94.10?±?0.99), and treatment with 300 μg/ml extract increased the cell viability (99.24?±?0.69). TCDD treatment resulted in a significant increase in the production of ROS, LPO (114?±?0.09), and PCC (15.13?±?1.53) compared to the control, whereas co-treatment with G. acerosa significantly (P?<?0.05) mitigated the effects. Further, G. acerosa significantly (P?<?0.05) prevented TCDD-induced genotoxicity and cell damage. GC-MS analysis showed the presence of n-hexadecanoic acid (retention time (RT) 13.15), cholesterol (RT 28.80), α-d-glucopyranose, 4-O-α-d-galactopyranosyl (RT 20.01), and azulene (RT 4.20). The findings suggest that G. acerosa has a strong protective ability against TCDD-induced cytotoxicity, oxidative stress, and DNA damage.     

Molecular characterization of microbial communities and quantification of <Emphasis Type="Italic">Mycobacterium immunogenum</Emphasis> in metal removal fluids and their associated biofilms

A number of human health effects have been associated with exposure to metal removal fluids (MRFs). Multiple lines of research suggest that a newly identified organism, Mycobacterium immunogenum (MI), appears to have an etiologic role in hypersensitivity pneumonitis (HP) in case of MRFs exposed workers. However, our knowledge of this organism, other possible causative agents (e.g., Pseudomonads), and the microbial ecology of MRFs in general, is limited. In this study, culture-based methods and small subunit ribosomal RNA gene clone library approach were used to characterize microbial communities in MRF bulk fluid and associated biofilm samples collected from fluid systems in an automobile engine plant. PCR amplification data using universal primers indicate that all samples had bacterial and fungal contaminated. Five among 15 samples formed colonies on the Mycobacteria agar 7H9 suggesting the likely presence of Mycobacteria in these five samples. This observation was confirmed with PCR amplification of 16S rRNA gene fragment using Mycobacteria specific primers. Two additional samples, Biofilm-1 and Biofilm-3, were positive in PCR amplification for Mycobacteria, yet no colonies formed on the 7H9 cultivation agar plates. Real-time PCR was used to quantify the abundance of M. immunogenum in these samples, and the data showed that the copies of M. immunogenum 16S rRNA gene in the samples ranges from 4.33?×?10⁴ copy/ml to 4.61?×?10⁷ copy/ml. Clone library analysis revealed that Paecilomyces sp. and Acremonium sp. and Acremonium-like were dominant fungi in MRF samples. Various bacterial species from the major phylum of proteobacteria were found and Pseudomonas is the dominant bacterial genus in these samples. Mycobacteria (more specifically MI) were found in all biofilm samples, including biofilms collected from inside the MRF systems and from adjacent environmental surfaces, suggesting that biofilms may play an important role in microbial ecology in MRFs. Biofilms may provide a shield or sheltered microenvironment for the growth and/or colonization of Mycobacteria in MRFs.     

Enhanced UV-B and Elevated CO<Subscript>2</Subscript> Impacts Sub-Arctic Shrub Berry Abundance,Quality and Seed Germination

This study investigated the effects of long-term-enhanced UV-B, and combined UV-B with elevated CO₂ on dwarf shrub berry characteristics in a sub-arctic heath community. Germination of Vaccinium myrtillus was enhanced in seeds produced at elevated UV-B, but seed numbers and berry size were unaffected. Elevated UV-B and CO₂ stimulated the abundance of V. myrtillus berries, whilst UV-B alone stimulated the berry abundance of V. vitis-idaea and Empetrum hermaphroditum. Enhanced UV-B reduced concentrations of several polyphenolics in V. myrtillus berries, whilst elevated CO₂ increased quercetin glycosides in V. myrtillus, and syringetin glycosides and anthocyanins in E. hermaphroditum berries. UV-B × CO₂ interactions were found for total anthocyanins, delphinidin-3-hexoside and peonidin-3-pentosidein in V. myrtillus berries but not E. hermaphroditum. Results suggest positive impacts of UV-B on the germination of V. myrtillus and species-specific impacts of UV-B × elevated CO₂ on berry abundance and quality. The findings have relevance and implications for human and animal consumers plus seed dispersal and seedling establishment.     

Phenological development stages variation versus mercury tolerance,accumulation, and allocation in salt marsh macrophytes <Emphasis Type="Italic">Triglochin maritima</Emphasis> and <Emphasis Type="Italic">Scirpus maritimus</Emphasis> prevalent in Ria de Aveiro coastal lagoon (Portugal)

Efficient and sustainable management of rapidly mounting environmental issues has been the focus of current intensive research. The present study aimed to investigate the impact of plant phenological development stage variation on mercury (Hg) tolerance, accumulation, and allocation in two salt marsh macrophytes Triglochin maritima and Scirpus maritimus prevalent in historically Hg-contaminated Ria de Aveiro coastal lagoon (Portugal). Both plant samples and the sediments vegetated by monospecific stands of T. maritima and S. maritimus were collected from reference (R) and sites with moderate (M) and high (H) Hg contamination in Laranjo bay within Ria de Aveiro lagoon. Hg tolerance, uptake, and allocation in T. maritima and S. maritimus, physico-chemical traits (pH, redox potential, and organic matter content) and Hg concentrations in sediments vegetated by these species were impacted differentially by phenological development stages variation irrespective of the Hg contamination level. In T. maritima, Hg concentration increased with increase in Hg contamination gradient where root displayed significantly higher Hg followed by rhizome and leaf maximally at H. However, in S. maritimus, the highest Hg concentration was perceptible in rhizome followed by root maximally at M. Between the two studied plant species, S. maritimus displayed higher Hg tolerance index (depicted by higher plant dry mass allocated to reproductive stage) and higher available Hg at M (during all growth stages) and H (during senescent stage) when compared to T. maritimus. Both plant species proved to be Hg excluder (low root/rhizome–leaf Hg translocation). Additionally, T. maritima also acted as Hg stabilizer while, S. maritimus as Hg accumulator. It can be inferred from the study that (a) the plant phenological development stage variations significantly influenced plant Hg sensitivity by impacting sediment chemistry, plant growth (in terms of plant dry mass), Hg accumulation, and its subsequent allocation capacity, contingent to Hg contamination gradient; (b) S. maritimus accumulated higher Hg but restricted its translocation to above-ground part using exclusion process at both M and H due to its accelerated growth during Hg-tolerant reproductive/metabolically active phenological development stage greater than its counterpart T. maritima; and (c) the studied salt marsh plants although hailed from the same C3 and monocot group did not necessarily display similar phenotypic plasticity and behavior towards Hg-contaminated scenario during their life cycle.     

Removal ratio of gaseous toluene and xylene transported from air to root zone via the stem by indoor plants

This work was designed to investigate the removal efficiency as well as the ratios of toluene and xylene transported from air to root zone via the stem and by direct diffusion from the air into the medium. Indoor plants (Schefflera actinophylla and Ficus benghalensis) were placed in a sealed test chamber. Shoot or root zone were sealed with a Teflon bag, and gaseous toluene and xylene were exposed. Removal efficiency of toluene and total xylene (m, p, o) was 13.3 and 7.0 μg·m^?3·m^?2 leaf area over a 24-h period in S. actinophylla, and was 13.0 and 7.3 μg·m^?3·m^?2 leaf area in F. benghalensis. Gaseous toluene and xylene in a chamber were absorbed through leaf and transported via the stem, and finally reached to root zone, and also transported by direct diffusion from the air into the medium. Toluene and xylene transported via the stem was decreased with time after exposure. Xylene transported via the stem was higher than that by direct diffusion from the air into the medium over a 24-h period. The ratios of toluene transported via the stem versus direct diffusion from the air into the medium were 46.3 and 53.7 % in S. actinophylla, and 46.9 and 53.1 % in F. benghalensis, for an average of 47 and 53 % for both species. The ratios of m,p-xylene transported over 3 to 9 h via the stem versus direct diffusion from the air into the medium was 58.5 and 41.5 % in S. actinophylla, and 60.7 and 39.3 % in F. benghalensis, for an average of 60 and 40 % for both species, whereas the ratios of o-xylene transported via the stem versus direct diffusion from the air into the medium were 61 and 39 %. Both S. actinophylla and F. benghalensis removed toluene and xylene from the air. The ratios of toluene and xylene transported from air to root zone via the stem were 47 and 60 %, respectively. This result suggests that root zone is a significant contributor to gaseous toluene and xylene removal, and transported via the stem plays an important role in this process.     

Phytoextraction of rare earth elements in herbaceous plant species growing close to roads

The aim of study was to determine the phytoextraction of rare earth elements (REEs) to roots, stems and leaves of five herbaceous plant species (Achillea millefolium L., Artemisia vulgaris L., Papaver rhoeas L., Taraxacum officinale and Tripleurospermum inodorum), growing in four areas located in close proximity to a road with varied traffic intensity. Additionally, the relationship between road traffic intensity, REE concentration in soil and the content of these elements in plant organs was estimated. A. vulgaris and P. rhoeas were able to effectively transport REEs in their leaves, independently of area collection. The highest content of REEs was observed in P. rhoeas leaves and T. inodorum roots. Generally, HREEs were accumulated in P. rhoeas roots and leaves and also in the stems of T. inodorum and T. officinale, whereas LREEs were accumulated in T. inodorum roots and T. officinale stems. It is worth underlining that there was a clear relationship between road traffic intensity and REE, HREE and LREE concentration in soil. No positive correlation was found between the concentration of these elements in soil and their content in plants, with the exception of T. officinale. An effective transport of REEs from the root system to leaves was observed, what points to the possible ability of some of the tested plant species to remove REEs from soils near roads.