Integrated wildfire danger models and factors: A review.

Wildfires have been systematically studied from the early 1950s, with significant progress in the applied computational methodologies during the 21st century. However, modern methods are barely adopted by administrative authorities, globally, especially those considering probabilistic models concerning human-caused fires. An exhaustive review on wildfire danger studies has not yet been performed. Therefore, the present review aims at collecting and analyzing integrated modeling approaches in estimating forest fire danger, examining the driving factors, and evaluating their influence on fire occurrence. The main objective is to propose the top performing methods and the most important risk factors for the development of an Integrated Wildfire Danger Risk System (IWDRS). Studies were classified based on the applied technique, i.e., geographic information systems, remote sensing, statistics, machine learning, simulation modeling and miscellaneous techniques. The conclusions of each study concerning the relative importance of model input variables are also reported. Online search engines such as 'Scopus', 'Google Scholar', 'WorldWideScience', 'ScienceDirect' and 'ResearchGate' were used in relevant literature searches published in scientific journals, manuals and technical documentation. A total of 230 studies were gathered with a selected subset being evaluated in a meta-analysis process. Machine learning techniques outperform average classic statistics, although their predictability relies heavily on the quantity and the quality of the input data. Geographic information systems and remote sensing are considered valuable yet supplementary tools. Modeling techniques apply best to fire behavior prediction, while other techniques referenced in the current review are potentially useful but further investigation is needed. In conclusion, wildfire danger is a function of seven thematic groups of variables: meteorology, vegetation, topography, hydrology, socio-economy, land use and climate. Ninety-five explanatory drivers are proposed.

Experiments on Pilot-Scale Constructed Floating Wetlands Efficiency in Removing Agrochemicals.

The efficiency of constructed floating wetlands (CFWs) in their ability to remove agrochemicals (nutrients and pesticides) is here investigated in a series of pilot-scale systems. Four experimental CFWs were designed and constructed; three of them were planted with the aquatic plant species Lemna minor, Azolla pinnata and Eichhornia crassipes. The fourth did not contain any plants and was used as the control. The aim of the study was to evaluate the efficiency of CFW containing aquatic macrophytes in the reduction of pesticides and nutrients, under field conditions. The CFWs operated continuously from May 2021 to September 2021, and their removal efficiencies of nitrogen and phosphorus ions, and five commonly used pesticides were examined. The CFW systems were fed daily with agricultural wastewater which was prepared by mixing a fertilizer and predetermined doses of pesticides. The hydraulic residence time was kept at 14 days. Samples were collected on a weekly basis from both the influent and the effluent of each experimental tank, and were subsequently analyzed in the laboratory. HPLC-DAD and Ion Chromatography were implemented for sample analysis following a very simple sample preparation. Reductions for nutrient ranged from no reduction to 100% removal, whereas for pesticides these varied from no reduction to 98.8% removal, indicating that these systems can be used as efficient and low-cost pollution control technologies for agrochemical wastewater treatment. Significant reduction for certain pesticides was also observed in the algae control tank, thus, proving the efficiency of algae in organic pollution reduction, and recognizing the limitations of aquatic plant use in decontamination.

Adaptation of urban drainage networks to climate change: A review.

The present work reviews the main challenges regarding adaptation of urban drainage networks to climate change by comparing 32 case studies from 29 articles, published between 2003 and 2020. The aim is to: (i) identify the state-of-the-art scientific approaches of adaptation of urban drainage networks to climate change; (ii) assess whether or not these approaches incorporated monetization of the adaptation practices and the associated costs/benefits; and (iii) define a novel approach (Blueprint) for the future development and assessment of urban drainage network adaptation to climate change and other drivers. First, the motivation is provided that makes urban drainage adaptation a globally relevant issue. Second, the main impacts of climate change on precipitation, flooding and urban drainage systems are discussed. Then, current practices are described. Finally, a blueprint for an integrated urban adaptation framework to climate change and other drivers is proposed. Our research indicated that future quantity and quality of urban runoff is not widely addressed in the scientific literature. The Storm Water Management Model is the most widely used software in modeling adaptation options. Solutions such as plans of maintenance and rehabilitation, public awareness, flood forecasting and warning, mobility measures and insurance measures are not widely reflected in the literature. Uncertainties of climate projections and bias correction methods are still significant, and uncertainties of socio-economic scenarios, hydrologic and hydrodynamic models, and adaptation options are not fully addressed. Finally, environmental cost and benefits associated with the ecosystem services provided by the adaptation options are not fully addressed.

A robust approach for comparing conventional and sustainable flood mitigation measures in urban basins.

An integrated methodological framework for assessing different flood mitigation measures in urban catchments is presented. The framework comprises hydrologic, hydraulic and economic indices aiming at quantifying the effect of different alternatives regarding flood hazard mitigation. The alternatives evaluated include both conventional drainage solutions and low impact development measures. The conventional drainage solutions were: (i) off-line detention tanks; and (ii) sewer enlargement. The low impact development measures included: (i) green roofs (GR); and (ii) permeable surfaces (PS). Each solution was modeled using SWMM5 with respect to flood reduction effectiveness, and the results were compared to those of the existing condition (i.e., no flood mitigation measures). All the examined solutions were also compared based on their construction and operation and maintenance costs for a typical lifespan (i.e., 30 years). The results of the simulation revealed that both low impact development measures and conventional drainage solutions were highly effective even for storm events with low probability of occurrence. However, sewer enlargement was found to be the best alternative from an economic perspective. Nevertheless, peak at the sewer exit increased and time to peak remained unchanged; as a result, local flooding problems are resolved but downstream flooding problems may be introduced. If other criteria are considered, i.e., traffic obstruction, noise, construction easiness, co-benefits and downstream impacts, low impact development measures become more attractive compared to conventional drainage solutions.

Water quality evaluation of a lacustrine water body in the Mediterranean based on different water quality index (WQI) methodologies.

The relative response of seven different Water Quality Indices (WQIs) was comparatively tested in an artificial Mediterranean lake, with the ultimate goal of the study to function as a first step in investigating the applicability of the examined WQIs in Mediterranean lacustrine water bodies. The following WQIs were examined: Prati's Index of Pollution, Bhargava's Index, Oregon WQI, Dinius' Second Index, Weighted Arithmetic Index, Canadian Council of Ministers of the Environment (CCME) WQI and National Sanitation Foundation (NSF) WQI, using physicochemical parameters measured in an artificial lake on a monthly basis from June 2004 to May 2005. The results showed that, on the basis of their comparative response, the examined indices are grouped in three categories. Specifically, NSF and Bhargava indices classified the examined water body in higher quality classes, Prati's and Dinius in medium, whereas CCME and Oregon categorized it in lower quality classes. WQIs were proved to be extremely useful in water quality evaluation. Most of them were found to be adequate to represent water quality conditions and trends in a lacustrine water body in the Mediterranean and, therefore, they present high potential to be adopted at European Union level and assist in Water Framework Directive (WFD) implementation.

Performance of Seven Water Quality Indices (WQIs) in a Mediterranean River.

The comparative performance of seven widely used Water Quality Indices (WQIs) is evaluated in a fluvial water body. The computation of the individual WQIs was based on bi-weekly measurements of eleven water quality parameters in Vosvozis River situated in Rhodope Prefecture, North Greece. The sampling campaign lasted 16 months (from August 2005 to November 2006), and over this period, the individual parameters were measured at three gauging stations along the river. The indices which were applied were the Prati's Index of Pollution, Bhargava's Index, Oregon WQI, National Sanitation Foundation (NSF) WQI, Canadian Council of Ministers of Environment (CCME) WQI, Dinius' Second Index, and the Weighted Arithmetic WQI. Apart from the computation of the above WQIs and the subsequent qualitative classification of the water body, the most important quality parameters per methodology were determined through the calculation of the correlation coefficient between each water quality parameter and the final WQI value. The results showed that Bhargava's Index along with NSF WQI tend to classify water bodies into superior quality classes, Prati's Index into slightly lower categories, whereas Oregon and CCME WQIs were found to be relatively "stricter," giving results ranging between the lowest classes of the qualitative ranking. These findings confirm those emerged by our previous studies while they are also partially in line with similar studies comparing a smaller number of indices. CCME WQI is suggested as the most appropriate, among the examined indices, since it is both "conservative" and adequately "sensitive" to reflect changes in water quality.

Evaluation of the water quality status of two surface water reservoirs in a Mediterranean island.

A 1-year monitoring study is presented on the chemical status of two surface water reservoirs in a decentralized Mediterranean island. Water samples were collected at varying depths in the two surface water reservoirs and different seasons between November 2015 and September 2016, covering both wet and dry periods of the year. Samples were analyzed in order to determine major chemical parameters and priority substances based on the EU Water Framework Directive (2000/60/EC) and the latest revision of the Priority Substances Policy Directive (2013/39/EU). Tested parameters in both reservoirs did not exceed the set limits. Increased pollutant concentrations were observed in the bottom samples. More than 200 pesticide active substances were determined but none of them was above the parametric trigger value (0.1 µg L-1). Toxic metals were not detected in the examined water samples, whereas the relatively high concentrations of Mn and Cu in the bottom samples are mainly attributed to geogenic background concentrations. Based on the results of the present study, it can be concluded that the chemical situation of both water reservoirs is considered acceptable; however, continuous monitoring should be implemented in the area.

Tree uptake of excess nutrients and herbicides in a maize-olive tree cultivation system.

Due to the extent of non-point source agricultural pollution, protective measures to control agrochemicals from entering aquatic systems are necessary. Measures may include, among others, vegetated buffer strips (VFS), no spray buffer zones, alley crops and agroforestry systems (AFS). The scope of the present work is to examine the pollution abatement potential of a maize-olive (MO) AFS. The efficiency of a combined MO trees system in reducing nutrients and herbicides is tested through soil monitoring in an experimental plot, located in Koropi, Eastern Attica, Greece, in the period May 2015 to November 2015. The monitored pollutants were nitrogen and phosphorus, as well as two herbicides: pendimethalin and nicosulfuron. Soil samples were collected every 3-5 weeks at various soil horizons and distances from the tree row. Pollutant concentrations were determined using liquid chromatography tandem mass spectrometry (LC-MS/MS), ion chromatography (IC) and spectrophotometry techniques. The studied MO tree system exhibited the potential to reduce pollutant migration, with removals ranging 36.8-78.9% for [Formula: see text], 79.3-100% for [Formula: see text], 76.7-100% for [Formula: see text], 79.4-100% for [Formula: see text] and 70-100% for the examined herbicides. The higher removal percentages were observed in the upper soil layers (5-35 cm, below the crops), and where the finer tree roots extend. Thus, the results indicate that planting of trees in cultivated fields can contribute to the reduction of agrochemical pollution of the subsurface soil and in extension of groundwater.

Effect of first-flush device, roofing material, and antecedent dry days on water quality of harvested rainwater.

Two rainwater harvesting systems, which included first-flush diversion devices, connected to the roofs of two adjacent buildings, were monitored for water quality. The roofs were constructed from different materials, i.e., one roof was covered with ceramic tiles and the other was made of concrete. Water quality samples from the two storage tanks and the first-flush devices were collected and analyzed, showing satisfactory water quality in the tanks for residential non-potable use, while the water in the first-flush device was of poorer quality. Between the two collection surfaces, statistically significant differences were found only in the concentrations of NH4-N, orthophosphate, and Ca2+. Total coliforms were detected in both the storage tanks and the first-flush devices, indicating that disinfection of harvested rainwater may be necessary if it is collected for potable uses. Finally, first-flush water quality was related to antecedent dry days, showing that when the number of dry days increased, the accumulation of materials on the concrete roof was reduced while it was increased on the ceramic tile roof. This is attributed to the fact that the concrete roof is nearly horizontal (very slightly sloped), and the wind action easily removes various materials which accumulate on it.

Chromium removal from wastewater using HSF and VF pilot-scale constructed wetlands: Overall performance, and fate and distribution of this element within the wetland environment.

The current experimental work aimed at the investigation of the overall chromium removal capacity of constructed wetlands (CWs) and the chromium fate-distribution within a wetland environment. For this purpose, the experimental setup included the parallel operation and monitoring of two horizontal subsurface flow (HSF) pilot-scale CWs and two vertical flow (VF) pilot-scale CWs treating Cr-bearing wastewater. Samples were collected from the influent, the effluent, the substrate and the plants. Apart from the continuous experiment, batch experiments (kinetics and isotherm) were conducted in order to investigate the chromium adsorption capacity of the substrate material. According to the findings, HSF-CWs demonstrated higher removal capacities in comparison to VF-CWs, while in both types the planted units indicated better performance compared to the unplanted ones. Analysis in various wetland compartments and annual mass balance calculation highlighted the exceptional contribution of substrate to chromium retention, while Cr accumulation in plant was not so high. Finally, experimental data fitted better to the pseudo-second-order and Langmuir models regarding kinetics and isotherm simulation.

Effect of operational and design parameters on performance of pilot-scale horizontal subsurface flow constructed wetlands treating university campus wastewater.

Three horizontal subsurface flow (HSF) pilot-scale constructed wetland (CW) units operated for 3 years treating municipal wastewater originating from a university campus. The main objective of the study was the evaluation of the performance of these systems under several operational, design, and climatic conditions. Several parameters and factors were investigated, including the influence of temperature, vegetation, and hydraulic residence time. The results were compared to those of a previous study conducted in the same pilot-scale units and under the same operational conditions where synthetic municipal wastewater was used. Results show the satisfying overall performance of the CW units. Performance seems to be influenced by vegetation, temperature, and hydraulic residence time (HRT). The planted units produced better results than the unplanted one while, generally, all units operated better under warmer conditions. In addition, longer HRTs contributed to higher removal efficiencies. Finally, the systems showed higher removal efficiencies in the previous study (synthetic wastewater) regarding organic matter removal, while for the other pollutants, the present study (real wastewater) showed higher or comparable performance in most cases and especially in the planted units. The study also shows the overall good, continuous, and long-term operation of CW systems, since these systems operate for about 13 years.

Effect of trees on the reduction of nutrient concentrations in the soils of cultivated areas.

The function of trees in reducing nutrient migration to groundwaters in cultivated areas, under Mediterranean climate conditions, is tested. Three cultivated fields were monitored for two cultivation periods. The common characteristic of the three fields was that on one side, they bordered with a poplar tree field. Four different crops were cultivated, and two cultivation periods were monitored. Based on the number of fields (i.e., three) and the cultivation periods (i.e., two), six different conditions (systems) were studied with four crops (i.e., sunflower, cotton, rapeseed, and corn). Soil samples were collected in all systems at the beginning, the middle, and the end of the cultivation period at various sampling sites (i.e., various distances from the tree row) and at various depths, and were analyzed in the laboratory for the determination of ΝΟ3-Ν and P-Olsen. In all systems, the greatest concentration of P-Olsen was measured in the surface layers (0-5, 10-15, and 30-35 cm) and was gradually decreased in the deeper layers (55-60 and 75-80 cm) indicating that P mobility is low. The ΝΟ3-Ν concentration in the deeper layers (55-60 and 75-80 cm) at all sampling sites was equal to or greater than that of the surface layers, indicating that ΝΟ3-Ν has high mobility in soils. At the sampling sites in the soil zone near the tree row, the ΝΟ3-Ν concentration in the deeper layers was lower than that of the surface, indicating that the tree root system takes up nutrients which otherwise would move toward the water table. There was also a reduction observed of the depth-averaged P-Olsen and ΝΟ3-Ν concentrations at the soil zone at a distance of 2.0-3.5 m from the tree row compared to locations more distant from the trees; this reduction ranged between 15 and 50 % and 36 and 54 %, respectively. The results indicate that planting of trees in cultivated fields can contribute to the reduction of nitrate pollution of groundwaters.

Suspended particulate matter estimates using optical and acoustic sensors: application in Nestos River plume (Thracian Sea, North Aegean Sea).

The present study investigates the use of combined methods of optical and acoustic sensors, in collaboration with direct in situ measurements, for the calibration and validation of a model transforming acoustic backscatter intensity series into suspended particulate matter (SPM) concentration datasets. The model follows previously elaborated techniques, placing particular attention to the parameterization of the acoustic absorption index as a function of water physical properties. Results were obtained from the annual deployment (during 2007-2008) of an upward-facing acoustic Doppler current profiler (ADCP) (307 kHz), equipped with a Wave Array, and an optical backscatter sensor (OBS), at the bottom of Thassos Passage near Nestos River plume (Thracian Sea, Northern Greece). The OBS was calibrated through linear regression, using 2007 and 2012 field sampling data, exhibiting an error of 13-14 % due to chlorophyll presence. The ADCP signal was calibrated through simultaneous measurements of backscatter intensity and turbidity profiles. Harmonic analysis on the model-produced SPM concentrations explained the tidal influence on their variability, especially during the summer. Empirical orthogonal functions analysis revealed the impact of waves and wave-induced currents on SPM variability. Finally, Nestos River sediment load was found uncorrelated to the SPM change in Thassos Passage, due to the dispersal and sediment deposition near the river mouth.

Environmental footprint of constructed wetlands treating wastewater.

The aim of the study is to determine environmentally friendlier construction materials for constructed wetland facilities treating wastewater. This is done by computing the environmental footprint of the facility based on the methodology of life cycle assessment (LCA). This methodology reveals the dominant aggravating processes during the construction of a constructed wetland (CW) and can help to create alternative environmentally friendlier solutions. This methodology was applied for the determination of the overall environmental profile of a hybrid CW facility. The LCA was applied first to the facility as originally designed, where reinforced concrete was used in some components. Then, alternative construction materials to reinforced concrete were used, such as earth covered with high density polyethylene (HDPE) or clay, and LCA was applied again. Earth structures were found to have reduced environmental impact compared to concrete ones, and clay was found environmentally friendlier compared to HDPE. Furthermore, estimation of the construction costs of the three scenarios indicate that the last scenario is also the least expensive.

Construction and operation costs of constructed wetlands treating wastewater.

Design data from nine constructed wetlands (CW) facilities of various capacities (population equivalent (PE)) are used to estimate construction and operation costs, and then to derive empirical equations relating the required facility land area and the construction cost to PE. In addition, comparisons between the costs of CW facilities based on various alternative construction materials, i.e., reinforced concrete and earth structures (covered with either high density polyethylene or clay), are presented in relation to the required area. The results show that earth structures are economically advantageous. The derived equations can be used for providing a preliminary cost estimate of CW facilities for domestic wastewater treatment.

Monitoring and modeling of two alluvial aquifers in lower Nestos river basin, Northern Greece.

A groundwater monitoring and modeling program in two aquifers within the lower Nestos river basin in Northern Greece is presented. A monitoring network of 54 wells was developed in the two study areas, and groundwater level measurements and water quality sample analyses were conducted for a period of 2.5 years, from March 2007 to October 2009. The field data were used for the calibration and verification of the mathematical model MODFLOW in the two aquifers. The validated model was used to examine ten alternative management scenarios regarding groundwater abstraction in the two aquifers. The study showed that MODFLOW, if properly validated, is a useful and flexible tool in groundwater resources management.

Heavy metal fate in pilot-scale sludge drying reed beds under various design and operation conditions.

Thirteen pilot-scale sludge drying reed bed (SDRB) units have been constructed and operated under various settings. The beds included a cobbles lower layer, where perforated PVC aeration tubes were placed, and two gravel layers on top. The setup included planted beds with common reeds and control units. Three sludge loading rates (SLR) were examined: 30, 60 and 75 kg dm/m(2)/yr. Heavy metal (HM) accumulation in the residual sludge layer was negligible or low, and was found to increase with sludge layer depth. Plant uptake was low; the belowground biomass accumulated significantly more HMs compared to the aboveground biomass. Less than 16% of the influent HM left the bed through drainage. HM accumulation in the gravel layer was the major metal sink in the mass balance. On the whole, the HM content of the residual sludge was below the legal limits proposed by the EU for land application.

Evaluation of evapotranspiration in small on-site HSF constructed wetlands.

Experimental results on evapotranspiration (ET), relevant to small on-site facilities are presented, derived from one-year controlled experiments in five pilot-scale horizontal subsurface flow (HSF) constructed wetlands (CW) used as lysimeters. The CW units operated in Northern Greece. They were rectangular tanks made of steel, with dimensions 3m long, 0.75m wide and 1m deep. Three different porous media were used, i.e., medium gravel, fine gravel and cobbles. Two plants were used, namely common reed (R, Phragmites australis) and cattails (C, Typha latifolia). One unit was unplanted. ET was estimated based on the water budget method. Conclusions were drawn on its relation to season and vegetation density. Furthermore, Pearson correlation coefficient analysis identified the main factors affecting wetland plant ET. Seven well-known ET empirical methods were applied to estimate ET using the measured meteorological and wetland data. ET estimated by the empirical methods were multiplied with appropriate correction coefficients to match measured ET, providing this way appropriate plant coefficient (K(c)) values, and equations for predicting HSF CW evapotranspiration. The suitability of these methods for the particular constructed wetland type is discussed through comparison with the measured data. The Blaney-Criddle method was found as best. Furthermore, stepwise multiple linear regression analysis was used with the measured ET and meteorological data to produce simple empirical equations to predict ET rates according to meteorological factors, plant and substrate material.

Stability and maturity of thickened wastewater sludge treated in pilot-scale sludge treatment wetlands.

Thickened wastewater activated sludge was treated in 13 pilot-scale sludge treatment wetlands of various configurations that operated continuously for three years in North Greece. Sludge was loaded for approximately 2.5 years, and the beds were left to rest for the remaining period. Three different sludge loading rates were used that represented three different population equivalents. Residual sludge stability and maturity were monitored for the last year. Sludge was regularly sampled and microbial respiration activity indices were measured via a static respiration assay. The phytotoxicity of sludge was quantified via a seed germination bioassay. Measurements of total solids, organic matter, total coliforms, pH and electrical conductivity were also made. According to microbial respiration activity measurements, the sludge end-product was classified as stable. The germination index of the final product exceeded 100% in most wetland units, while final pH values were approximately 6.5. The presence of plants positively affected the stability and maturity of the residual sludge end-product. Passive aeration did not significantly affect the quality of the residual sludge, while the addition of chromium at high concentrations hindered the sludge decomposition process. Conclusively, sludge treatment wetlands can be successfully used, not only to dewater, but also to stabilize and mature wastewater sludge after approximately a four-month resting phase.

Removal of faecal bacteria from septage by treating it in a full-scale duckweed-covered pond system.

Performance of a full-scale duckweed-covered treatment system in removing faecal bacteria is presented. The system consisted of three ponds in series and received septage from holding tanks. Inflow averaged between 36 m(3) d(-1) in the cold season and 60 m(3) d(-1) in the warm season, resulting in a total hydraulic retention time of 88 and 58 days, respectively. Duckweed (Lemna minor) colonized the ponds in the summer and continued to grow in the cold season. Due to the difficult harvesting process of the duckweed biomass, the investigation of the treatment efficiency was carried out without plant harvesting. The system was monitored for temperature, pH, oxygen, chlorophyll-a, Escherichia coli and Enterococci. Duckweed growth resulted in chlorophyll-a concentration reduction from 924 to 13 µg L(-1), causing neutral and anoxic conditions in the pond water. A temperature effect was noticed on the E. coli decay coefficient with a decreasing trend along the treatment system. Enterococci always decayed less than E. coli. Differences on decay coefficients and removal efficiencies were not observed between the three ponds for both bacterial types. Effluent quality in terms of E. coli was 489 and 1377 cfu/100 mL, in the warm and the cold seasons, respectively, with average removals of 99.65 ± 1.46% and 99.33 ± 3.03%. Total Enterococci removal was 88.91 ± 23.1% in the warm season and 94.43 ± 24.45% in the cold season, resulting in mean effluent values of 1058 and 1404 cfu/100 mL, respectively. The seasonal differences in total removal efficiencies were insignificant for both bacterial types.