Use of ornamental plants in floating treatment wetlands for greywater treatment in urban areas.

Floating treatment wetlands are considered a promising and low-cost technology for the treatment of polluted water and wastewater. However, their functionality and efficiency in different types of wastewater are not fully understood. In this study, several ornamental plant species (monocultures: Canna sp., Iris sp., polyculture: Iris orientalis, Cyperus sp., Acorus gramineus) were tested in two different types of floating mats, including a media supported floating mat (MSFM) or a simple plastic grid, and evaluated for optimal removal of the studied pollutants. The results regarding pollutant removal revealed that planted systems grown in MSFM achieved significantly higher removal rates (up to 90 %) compared to the plastic grid (up to 80 %). Statistically significant higher removal rates were obtained for the planted systems compared to the unplanted systems either grown in MSFM (for turbidity (planted: 82-90 %; unplanted: 44 %), COD (planted: 74-84 %; unplanted: 32 %) and BOD5 (planted: 76-85 %; unplanted: 51 %), respectively) or grown in the plastic grid (for turbidity (planted: 64-78 %; unplanted: 44 %) and COD (planted: 43-75 %; unplanted: 32 %), respectively). During the experimental period (7 months), all plants managed to survive and withstand the weather variations. The plants in polyculture followed by Iris sp. plants in plastic grid floating mats were better adapted, as indicated by maximum quantum efficiency of PSII values and chlorophyll content index, while all the plants were considered well adapted in the MSFM. Overall, the implementation of floating treatment wetlands with ornamental vegetation for greywater treatment in urban areas seems to be a sustainable and efficient approach.

From bioaccumulation to biodecumulation: Nickel movement from Odontarrhena lesbiaca (Brassicaceae) individuals into consumers.

Hyperaccumulation describes plants' ability to take up high amounts of soil metals such as Ni and allocate them to aboveground tissues. Little is known, however, about the rate at which Ni is allocated to different plant parts, or about the consumers related to these parts, including their pollinator mutualists. In this study, we examine the interface between the serpentine endemic Ni-hyperaccumulator Odontarrhena lesbiaca and its consumers of different plant parts: leaves (consumers), floral parts (consumers and primitive pollinators), and floral rewards (true pollinators). The study was conducted at two serpentine areas on Lesvos, Greece. Over 13 rounds of sampling during the flowering period of O. lesbiaca in both areas we collected plant stems with flowers, consumers of different plant parts, and flower visitors. Collected animals were mainly insects and some spiders. Chemical analyses showed negligible Ni-concentration differences between the two areas. Among all plant parts, the lowest Ni concentration was found in pollen and the highest in leaves. Regarding animal dietary habits, folivores accumulated the highest Ni concentrations, therefore characterized as "high-Ni insects", while floral-reward consumers, both primary (bees) and secondary (Eristalis tenax, Pygopleurus spp., and wasps), bore low Ni loads. Ni-body load of predators that fed on animals that were passing by was also low. Among floral-reward consumers, short-range fliers (bees of the genera Andrena and Lasioglossum) accumulated higher Ni loads than long-range fliers (Apis mellifera, Bombus terrestris, Eristalis tenax). Solitary Andrena bees accumulated higher Ni concentration than eusocial honeybees (Apis mellifera) and bumblebees (Bombus terrestris); a group of Lasioglossum specimens encompassing both solitary and eusocial bees lay in between. Our results show that diet, foraging distance, and sociality are important factors for Ni transferred into consumers and mutualists, mostly insects that are directly associated with different plant parts of O. lesbiaca.

Removal mechanisms of benzotriazoles in duckweed Lemna minor wastewater treatment systems.

The fate of five benzotriazoles (1H-benzotriazole, BTR; 4-methyl-1H-benzotriazole, 4TTR; 5-methyl-1H-benzotriazole, 5TTR; xylytriazole, XTR and 5-chlorobenzotriazole, CBTR) was studied in batch and continuous-flow Lemna minor systems and the role of different mechanisms on their removal was evaluated. Single and joint toxicity experiments were initially conducted using the Organization for Economic Co-operation and Development (OECD) protocol 221 and no inhibition on specific growth rate of Lemna minor was observed for concentrations up to 200µgL-1. All tested substances were significantly removed in batch experiments with Lemna minor. Excepting 4TTR, full elimination of CBTR, XTR, 5TTR and BTR was observed up to the end of these experiments (36d), while the half-life values ranged between 1.6±0.3d (CBTR) and 25±3.6d (4-TTR). Calculation of kinetic constants for hydrolysis, photodegradation, and plant uptake revealed that for all BTRs the kinetic constants of plant uptake were by far higher comparing to those of the other mechanisms, reaching 0.394±0.161d-1 for CBTR. The operation of a continuous-flow Lemna minor system consisted of three mini ponds and a total hydraulic residence time of 8.3d showed sufficient removal for most target substances, ranging between 26% (4TTR) and 72% (CBTR). Application of a model for describing micropollutants removal in the examined system showed that plant uptake was the major mechanism governing BTRs removal in Lemna minor systems.