No abstract

Purpose Although the influences of urban land use on water quality have been widely investigated, the impacts of different urbanization patterns, particularly in Mediterranean environments, are not well understood. Focussing on a Portuguese peri-urban catchment with 40 % urban cover, this paper explores (1) the impact of areas with differing urban extent and storm drainage system on streamwater quality and (2) temporal variations driven by season and storm events of differing magnitude, intensity and antecedent weather. Materials and methods Water quality was assessed at the catchment outlet (E) and for three upstream tributaries: (1) Porto Bordalo (PB), 39 % urban with a new major road and piping of some overland flow from impervious surfaces directly into the stream; (2) Espírito Santo (ES), 49 % urban, mostly comprising detached houses surrounded by gardens, and with overland flow infiltrating into downslope pervious soils; and (3) Quinta (Q), 22 % urban with partial piping of overland flow from a recent enterprise park area. Water samples were collected at different stages in storm hydrograph responses to ten rainfall events from October 2011 to March 2013. The water quality variables analysed included chemical oxygen demand (COD), nutrients (Kjeldahl nitrogen [Nk-N], ammonium , nitrate [NO 3 -N] and total dissolved phosphorus (TDP) and heavy metals (Zn and Cu). Results and discussion Urban areas had great impact on COD, with the highest median concentrations in ES and the lowest in Q. In ES, fertilizing lawns and gardens may have been responsible for its higher median NO 3 -N concentrations. High concentrations of heavy metals were recorded in PB and Q, probably due to the piping of road runoff directly into the stream. Generally, higher pollutant concentrations were recorded in the first storm events after the summer drought due to the flushing of accumulated solutes and a lower dilution effect, with Nk-N and NH 4 -N exceeding water quality standards. Over the wet season, increasing soil moisture favoured greater flow connectivity between runoff processes from pollutant sources and the stream network, leading to a higher proportion of samples exceeding pollution thresholds. Conclusions No direct relationship was identified between urban extent and water quality, possibly due to the overriding impact of different storm drainage systems and flow connectivities of different urban patterns. Hydrological regime, linked to seasonal changes, also exerted a major influence on the water quality dynamics. Information on the spatiotemporal dynamics of pollutants, linked to different urban patterns and storm drainage systems, should help enable urban planners to minimize the adverse impacts of urbanization on aquatic ecosystems.

The interaction of three lectins (wheat germ, Ulex europaeus I, and Lotus tetragonolobus agglutinins: WGA, UEA-I and LTA) with either N-acetyl-D-glucosamine or L-fucose neoglycolipids incorporated into phospholipid monolayers and liposome bilayers was studied at the air/water interface and in bulk solution. The results show that for both systems studied, synthesized neoglycolipids were capable of binding their specific lectin and that, in general, the binding of lectins increased with the increase in the molar fraction of the saccharide derivative incorporated in either the monolayers or bilayers. However, whereas for UEA-I, molecular recognition was enhanced by a strong hydrophobic interaction, for WGA and LTA successful recognition was predominantly related to the distance between neighboring sugar groups. The observed lengthy adsorption times of these lectins onto their specific ligands were attributed to interfacial conformational changes occurring in the proteins upon their adsorption at the interfaces.

Activated sludge systems are prone to be affected by foaming occurrences causing the sludge to rise in the reactor and affecting the wastewater treatment plant (WWTP) performance. Nonetheless, there is currently a knowledge gap hindering the development of foaming events prediction tools that may be fulfilled by the quantitative monitoring of AS systems biota and sludge characteristics. As such, the present study focuses on the assessment of foaming events in full-scale WWTPs, by quantitative protozoa, metazoa, filamentous bacteria, and sludge characteristics analysis, further used to enlighten the inner relationships between these parameters. In the current study, a conventional activated sludge system (CAS) and an oxidation ditch (OD) were surveyed throughout a period of 2 and 3 months, respectively, regarding their biota and sludge characteristics. The biota community was monitored by microscopic observation, and a new filamentous bacteria index was developed to quantify their occurrence. Sludge characteristics (aggregated and filamentous biomass contents and aggregate size) were determined by quantitative image analysis (QIA). The obtained data was then processed by principal components analysis (PCA), cross-correlation analysis, and decision trees to assess the foaming occurrences, and enlighten the inner relationships. It was found that such events were best assessed by the combined use of the relative abundance of testate amoeba and nocardioform filamentous index, presenting a 92.9 % success rate for overall foaming events, and 87.5 and 100 %, respectively, for persistent and mild events.