Rice fields represent important production rates in Portugal. However, the intensive soil management and the exploitation of agrochemicals may pose a threat to nontarget organisms. Hence, the present work regards the toxicity screening of surface waters and sediment elutriates collected during the drainage of fields in the vicinity of a rice paddy (Quinta do Seminário, Soure, Portugal): 1. in River Pranto (RP), the river from which the field irrigation water is canalized; 2. inside the rice paddy, from the main drainage channel - Vala de Enxugo (VE). For that purpose, it was used a combination of physico-chemical analyses and bioassays with two green algae species - Pseudokirchneriella subcapitata and Chlorella vulgaris. The chemical screening showed an apparent absence of xenobiotics in sediment samples, while no pesticides were found within the chemical contaminants detected in water samples. The nutrient load reflected low levels of inorganic contamination. Bioassays revealed that P. subcapitata was more sensitive to the overall physico-chemical conditions in natural samples than C. vulgaris, being its growth inhibited under water samples from both sites. On a whole, water samples, mainly those from the main irrigation/drainage channel of the rice fields (VE), were more deleterious to microalgae than those from RP or any of the elutriates.

A plot scale study was conducted to determine bacterial transport in runoff from cropland treated with poultry litter and dairy manure applied at phosphorus (P) agronomic rates. Treatments included surface application of dairy manure, surface application of poultry litter, incorporation of dairy manure and control. A rainfall simulator was used to induce runoff 1 and 2 days after manure application. Runoff was analyzed to determine the concentration of indicator bacteria-fecal coliform, Escherichia coli, and Enterococcus. Observed edge-of-field bacterial concentrations were 10² to 10⁵ times higher than Virginia's in-stream bacteria criteria for primary contact recreation waters. No significant treatment effects were observed on edge-of-field bacteria concentration or yield. Results suggest that the manure application based on agronomic P rates may yield significant bacterial loading to downstream waterbodies if rainfall occurs soon after manure application. This research underscores the need for BMPs that reduce runoff volumes and filter pollutants associated with animal manures.

Phosphorous dynamics within Lake Sirio (NW Italy) were investigated, considering both water and sediments. The total phosphorus (TP) concentration in the water is about 79 μg l-¹ after the winter mixing, that is in homogeneous conditions; then TP content increases up to an average of 360 μg l-¹ in late autumn in the deep hypolimnium (30-45 m). This deep lake portion accounts for only 1/12 of the water volume. Close to the water-sediment interface, TP concentrations up to 530 μg l-¹ are observed. Sediment sampled at depths of 20 and 33 m contains less than 2,000 mg kg-¹ of TP, whereas cores from the deepest sediments (46 m) display TP values of 2,000-4,000 mg kg-¹ at the water-sediment interface, increasing with depth to 16,000 mg kg-¹ at about 60-100 cm. In these deep sediments the main chemical form is the Al-Fe-Mn bound P (about 90% in the high TP cores) and Fe and Mn are also highly enriched (3 and 9 times more than in the shallow sediments respectively). The P-Fe association is confirmed by SEM-EDS and XRD analyses. The vertical distribution of the P content in the water column is consistent with its release from sediments, but in this hypothesis an unrealistic P release rate from 8.1 to 3.0 g m-²y-¹ was estimated. A more complex model is therefore proposed, involving a process of P concentration in the sediments of the central (deepest) part of the lake, and a short term sediment-water exchange. The TP vertical variability and speciation in the cores suggests a change in the sediment retention capacity, connected to the lake shift to more eutrophic conditions.

Polycyclic aromatic hydrocarbons (PAHs) were measured in two wetland plant species grown outdoors in pots of sediment contaminated with up to 730,000 μg/kg total PAHs. After approximately 3 months, the plants were harvested, cleaned, and analyzed for an expanded suite of PAHs which included both the 16 priority PAHs and 22 alkyl PAH homologs. Sediment and air samples were also collected and analyzed. PAH compounds were detected in all of the samples, with the highest concentrations in the contaminated sediment. The root sample concentrations were generally about one order of magnitude lower than that of the sediment, and were strongly correlated with the concentration in the sediment in which they were grown. The concentrations in foliage were much lower and did not correlate with sediment concentration. Concentrations of low molecular weight PAH compounds detected in the foliage were not significantly lower in plants grown in control sediments, suggesting that the sediment is not the primary source of these PAHs. Several high molecular weight PAHs were detected only in plants grown in contaminated sediment. Plants of both species grown in control sediment were larger than plants grown in contaminated sediment.

To assess the effect of changes in traffic density and fuels used for heating at the beginning of the 1990s, 1992-2005 monthly averages of PM₁₀, SO₂, NO₂, NO, CO and O₃ from Prague, the Czech capital, were analyzed together with long term trends in emissions of major pollutants, fuel consumption and number of vehicles registered in Prague. The data from all monitoring stations were retrieved from the database of the state automated monitoring system. Correlation coefficients between ambient monthly averaged temperature and all pollutants of concern showed distinct seasonal trends. The results showed that while SO₂ and to some extent also CO concentrations dropped namely in the first half of the analyzed period (1992-1997) as a result decreased fossil fuel consumption for local heating, the behaviour of other pollutant concentrations followed a different pattern. PM₁₀ concentrations decreased during the beginning of the 1990s but showed a sign of increase after 2000. Concentrations of ozone and NO₂ did not reveal any significant change throughout the whole studied period. It can be concluded that during the studied period traditional urban sources of pollution, such as coal and oil combustion, lost their importance but were simultaneously substituted by pollutants from automotive transport (namely PM and NO₂) making the problem of air quality even worse.

A critical load data base was developed for Europe and Northern Asia using the latest data bases on soils, vegetation, climate and forest growth. Critical loads for acidity and nutrient nitrogen for terrestrial ecosystems were computed with the Simple Mass Balance model. The resulting critical loads are in accordance with critical loads from previous global empirical studies, but have a much higher spatial resolution. Critical loads of acidity are sensitive to both the chemical criterion and the critical limit chosen. Therefore a sensitivity analysis of critical loads was performed by employing different chemical criteria. A critical limit based on an acid neutralizing capacity (ANC) of zero resulted in critical loads that protect ecosystems against toxic concentrations of aluminium and unfavourable Al/Bc ratios, suggesting that ANC could be an alternative to the commonly used Al/Bc ratio. Critical loads of nutrient nitrogen are sensitive to the specified critical nitrate concentration, especially in areas with a high precipitation surplus. If limits of 3¿6 mg N l¿1 are used for Western Europe instead of the widely used 0.2 mg N l¿1, critical loads double on average. In low precipitation areas, the increase is less than 50%. The strong dependence on precipitation surplus is a consequence of the simple modelling approach. Future models should explore other nitrogen parameters (such as nitrogen availability) instead of leaching as the factor influencing vegetation changes in terrestrial ecosystems.

A detailed analysis of different types of gravity distribution devices, designed to split on-site wastewater effluent equally between percolation trenches, has been carried out both in the laboratory and also in the field under realistic loading conditions. Four different types of distribution device have been compared: a V-notch distribution box, stilling chamber box and tee-splitters with and without baffles. The trials carried out in the laboratory with clean water showed that flow distribution for all devices was sensitive to both the off-level installation angles and variable flow rates, with the most stable performance achieved using the flow splitter with upstream baffle plates. In parallel to this, the on-site flow regime experienced at two sites was continuously monitored using a tipping bucket and data-logger over twelve month periods, finding that the most common flow rates at the distribution unit were in the range of 0.1–2.5 l min⁻¹. The on-site performance of these devices receiving both septic tank and secondary treated effluent showed that significant solid deposition and biofilm development had severely affected the equal distribution between the trenches, hence highlighting the need for regular maintenance to ensure efficient performance over time after installation.

Concentrations of Cr, Cu, Hg, Pb and Zn have been measured, by atomic absorption spectrophotometry, in the fine fraction (<63 μm) of surface sediments collected in 30 sites in the Palermo Gulf (Sicily, Italy) in order to assess the levels and the spatial distribution of these elements. Enrichment factors calculated with respect to clean areas have been considered to discriminate between levels due to background or to pollution contributions. The sampling stations, which form a grid inside these areas, are characterized by geographic proximity and by the presence of pollution sources. Ratio matching technique along with hierarchical clustering, minimum spanning tree and principal component analysis have been used for the statistical analysis of data, allowing to better describe the spatial distribution of metal levels. Our work allowed to assess the anthropogenic contribution to the pollution of the area under investigation through industrial and domestic wastes, presence of an harbour area and river inflow.

Nitrates in concentrated brines can be electrochemically reduced in the cathodic chamber of a split-cell electrochemical reactor with formation of ammonium (and small amounts of nitrite). Fortunately, ammonium may be electrochemically oxidized to nitrogen gas in the anodic reaction chamber if a coupled sequential process is used. The presence of chloride in the brine waste is an important consideration in oxidative electrochemical processes, however, because it cycles through oxidized and reduced states at the electrode surfaces and in the bulk solution. Electrochemical oxidation converts chloride ions to “active chlorine” species with additional oxidizing capability (chlorine, hypochlorous acid and hypochlorite - essentially bleach), as well as to chlorates, depending on the reaction conditions. The production of these active species improves treatment performance in the ammonium oxidation phase since oxidation is no longer limited to the electrode surface. However, the process must be engineered to minimize loss of process efficiency due to parasitic side reactions (chloramines and chlorate). In this study, two-stage batch electrolysis was conducted using a three-electrode (copper anode, platinum-coated titanium cathode, silver/silver chloride reference) electrochemical cell, with the anodic and cathodic chambers separated by a Nafion 117 membrane. Treatment of nitrate and ammonium was tested with and without the presence of chloride in the waste. No significant difference was observed in cathodic nitrate reduction with chloride present or absent. However, the presence of chloride in the solution favored overall soluble nitrogen elimination upon oxidation. Increasing applied current increased production of undesirable byproducts (especially chlorate).