Addressing the C/N imbalance in the treatment of irrigated agricultural water by using a hybrid constructed wetland at field-scale.

To mitigate excess of nitrate-N (NO3--N) derived from agricultural activity, constructed wetlands (CWs) are created to simulate natural removal mechanisms. Irrigated agricultural drainage water is commonly characterized by an organic carbon/nitrogen (C/N) imbalance, thus, C limitation constrains heterotrophic denitrification, the main biotic process implicated in NO3--N removal in wetlands. We studied a pilot plant with three series (169 m2) of hybrid CWs over the first two years of functioning to examine: i) the effect of adding different C-rich substrates (natural soil vs. biochar) to gravel on NO3--N removal in a subsurface flow (Phase I), ii) the role of a second phase with a horizontal surface flow (Phase II) as a source of dissolved organic C (DOC), and its effect in a consecutive horizontal subsurface flow (Phase III) on NO3--N removal, and iii) the contribution of each phase to global NO3--N removal. Our results showed that the addition of a C-rich substrate to gravel had a positive effect on NO3--N removal in Phase I, with mean efficiencies of 40% and 17% for soil and biochar addition, respectively, compared to only gravel (0.75%). In Phase II, the algae growth turned into a DOC concentration increase, but it did not enhance NO3--N removal in Phase III. In series with C-rich substrate addition, the largest contribution to NO3--N removal was found in Phase I. However, in series with only gravel, Phase II was the most effective on NO3--N removal. Contribution of Phase III to NO3--N removal was almost negligible.

Role of dry watercourses of an arid watershed in carbon and nitrogen processing along an agricultural impact gradient.

In the Mediterranean arid region such as Southeast (SE) Spain, a considerable part of the fluvial network runs permanently dry. Here, many dry watercourses are embedded in catchments where agriculture has brought changes in carbon (C) and nitrogen (N) availability due to native riparian vegetation removal and the establishment of intensive agriculture. Despite their increasing scientific recognition and vulnerability, our knowledge about dry riverbeds biogeochemistry and environmental drivers is still limited, moreover for developing proper management plans at the whole catchment scale. We examined CO2 and N2O emissions in five riverbeds in SE Spain of variable agricultural impact under dry and simulated rewetted conditions. Sediment denitrifying capacity upon rewetting was also assessed. We found that, regardless of agricultural impact, all riverbeds can emit CO2 under dry and wet conditions. Emissions of N2O were only observed in our study when a long-term rewetting driving saturated sediments was conducted. Besides, most biogeochemical capabilities were enhanced in summer, reflecting the sensitiveness of microbial activity to temperature. Biogeochemical processing variation across rivers appeared to be more controlled by availability of sediment organic C, rather than by agriculturally derived nitrate. We found that the studied dry riverbeds, agriculturally affected or not, may be active sources of CO2 and contribute to transitory N2O emissions during rewetting phenomena, potentially through denitrification. We propose that management plans aiming to support ecosystem biogeochemistry through organic C from native vegetation rather than agricultural exudates would help to reduce anthropogenic greenhouse gases emissions and excess of nutrients in the watershed and to control the nitrate inputs to coastal ecosystems.

[Non-randomized trial to evaluate a continuous physiotherapy program versus interval in overweight patients suffering from acute coronary syndrome]. / Ensayo no aleatorizado de un programa de fisioterapia continuo frente a interválico para pacientes con sobrepeso y síndrome coronario agudo.

We present a non-randomised trial to evaluate a continuous physiotherapy program versus a periodic one in overweight patients suffering from acute coronary syndrome. AIM: To detect differences between a continuous (CONT) physiotherapy program (PF) and a periodic (INT) physiotherapy program in overweight patients with acute coronary syndrome on anthropometric parameters, analytical parameters, heart rate, adherence, drop-outs, safety and tolerance. DESIGN: A multicentre, non-randomised two-armed quasi-experimental study with pre-post design. LOCATION: Community cardiac prevention centres (Manises, Valencia-LaFe, Játiva-Onteniente Health Department). PARTICIPANTS: The study included a total of 339 overweight participants with acute coronary syndrome; living in the community; aged more than 18; no contraindication for physical exercise; no previous participation in a PF. INTERVENTIONS: Participants were assigned to a CONT training or an INT training (2 months). Each session was divided in warm-up, endurance, and cool-down. Endurance was performed at 12-13 Borg intensity and with heat rate calculated, with maximum heat rate obtained in the baseline ergometry. MAIN MEASUREMENTS: Body mass index, waist circumference, lipid profile, blood glucose, glycosylated haemoglobin, resting heat rate, adherence, drop-outs, safety, and tolerance were assessed. RESULTS: The CONT group showed significantly better differences in body mass index, waist circumference, total cholesterol, triglycerides, blood glucose, glycosylated haemoglobin and resting heat rate. No differences were observed in adherence, drop-outs, safety, and tolerance. CONCLUSIONS: The CONT group obtained better results in all variables except for HDL cholesterol. Both programs offered a high adherence, safety, and tolerance.

Simulating rewetting events in intermittent rivers and ephemeral streams: A global analysis of leached nutrients and organic matter.

Climate change and human pressures are changing the global distribution and the extent of intermittent rivers and ephemeral streams (IRES), which comprise half of the global river network area. IRES are characterized by periods of flow cessation, during which channel substrates accumulate and undergo physico-chemical changes (preconditioning), and periods of flow resumption, when these substrates are rewetted and release pulses of dissolved nutrients and organic matter (OM). However, there are no estimates of the amounts and quality of leached substances, nor is there information on the underlying environmental constraints operating at the global scale. We experimentally simulated, under standard laboratory conditions, rewetting of leaves, riverbed sediments, and epilithic biofilms collected during the dry phase across 205 IRES from five major climate zones. We determined the amounts and qualitative characteristics of the leached nutrients and OM, and estimated their areal fluxes from riverbeds. In addition, we evaluated the variance in leachate characteristics in relation to selected environmental variables and substrate characteristics. We found that sediments, due to their large quantities within riverbeds, contribute most to the overall flux of dissolved substances during rewetting events (56%-98%), and that flux rates distinctly differ among climate zones. Dissolved organic carbon, phenolics, and nitrate contributed most to the areal fluxes. The largest amounts of leached substances were found in the continental climate zone, coinciding with the lowest potential bioavailability of the leached OM. The opposite pattern was found in the arid zone. Environmental variables expected to be modified under climate change (i.e. potential evapotranspiration, aridity, dry period duration, land use) were correlated with the amount of leached substances, with the strongest relationship found for sediments. These results show that the role of IRES should be accounted for in global biogeochemical cycles, especially because prevalence of IRES will increase due to increasing severity of drying events.

[Descriptive and comparative study of cardiovascular risk factors and physical activity in patients with acute coronary syndrome]. / Estudio descriptivo y comparativo de factores de riesgo cardiovascular y actividad física en pacientes con síndrome coronario agudo.

AIM: To analyse several cardiovascular risk factors by means of the physical activity performed by patients with acute coronary syndrome (ACS). DESIGN: Cross-sectional study. LOCATION: Cardiovascular prevention service (Health Department, Valencia, Spain). PARTICIPANTS: The study included 401 individuals with acute coronary syndrome and discharged from hospital 2-3months before the assessment. The inclusion criteria included age between 30 and 80years-old, no contraindication for physical activity, and no previous participation in cardiac rehabilitation programmes. MAIN MEASUREMENTS: Metabolic equivalent MET (Kcal/Kg) was calculated, based on the type of activity, frequency, duration and intensity. Participants were divided into two groups: sedentary group (<10METs/week) and physically active group (≥10METs/week). Several variables associated with cardiovascular risk factors were assessed: body mass index (BMI), waist circumference, lipid profile, blood glucose, and arterial pressure. RESULTS: The mean consumption was 8.24±12.5METs/week. Prevalent factors were overweight (77.05%), and dyslipidaemia (64.3%), whilst 64.8% were sedentary. The physically active group showed differences when compared to sedentary group in triglycerides (146.53±72.8 vs. 166.94±104.8mg/dL; 95%CI; P=.031), and BMI (27.65±3.86 vs. 28.50±4.38kg/m2; 95%CI; P=.045). CONCLUSION: Physical activity was performed by a limited number of patients with ACS, with a prevalence of overweight and dyslipidaemia. Being physically active improved triglycerides levels and BMI. Therefore, health promotion from Primary Care and encouraging physical activity amongst patients with ACS is crucial.

Association between Post-Hospitalization Psychological Distress, Exercise Capacity, Physical Function and Health Status in COVID-19 Survivors.

This study aims to determine whether post-hospitalization psychological distress is associated with exercise capacity, physical function and health status in COVID-19 survivors. In this observational study, hospitalized COVID patients were included and divided into two groups according to the mental component summary subscale of the 12-item Short-Form Health Survey. Patients with a score ≤ 45 were included in the psychological distress group, and patients with a score > 45 were included in the non-psychological distress group. The main variables were exercise capacity, physical function, and health status. Patients were evaluated at discharge, 3 months, and at 6 months follow-up. Finally, a total of 60 patients were included in the study. Significant differences were found in exercise capacity, physical function, and health status (p < 0.05), with worse results in the group with psychological distress at discharge and 3 months follow-up. At 6 months after discharge, COVID patients with psychological distress exhibited worse results in exercise capacity, physical function, and health status, being significant exercise capacity and physical function (p < 0.05). It can be concluded that COVID patients with psychological distress at hospital discharge reported worse exercise capacity, physical function and health status at hospital discharge, 3 months and 6 months follow-up.

Unravelling large-scale patterns and drivers of biodiversity in dry rivers.

More than half of the world's rivers dry up periodically, but our understanding of the biological communities in dry riverbeds remains limited. Specifically, the roles of dispersal, environmental filtering and biotic interactions in driving biodiversity in dry rivers are poorly understood. Here, we conduct a large-scale coordinated survey of patterns and drivers of biodiversity in dry riverbeds. We focus on eight major taxa, including microorganisms, invertebrates and plants: Algae, Archaea, Bacteria, Fungi, Protozoa, Arthropods, Nematodes and Streptophyta. We use environmental DNA metabarcoding to assess biodiversity in dry sediments collected over a 1-year period from 84 non-perennial rivers across 19 countries on four continents. Both direct factors, such as nutrient and carbon availability, and indirect factors such as climate influence the local biodiversity of most taxa. Limited resource availability and prolonged dry phases favor oligotrophic microbial taxa. Co-variation among taxa, particularly Bacteria, Fungi, Algae and Protozoa, explain more spatial variation in community composition than dispersal or environmental gradients. This finding suggests that biotic interactions or unmeasured ecological and evolutionary factors may strongly influence communities during dry phases, altering biodiversity responses to global changes.

Effects of Cardiopulmonary Rehabilitation on the Muscle Function of Children with Congenital Heart Disease: A Prospective Cohort Study.

Critical medical and surgical advances have led to a shift in the care and management of children with congenital heart disease (CHD). These patients present with muscle deconditioning, which negatively influences their response to exercise, functional capacities, and quality of life. This study evaluates the influence of a cardiopulmonary rehabilitation program (CPRP) on the function of peripheral musculature of children with CHD. A single-center prospective cohort study was designed. Fifteen CHD subjects, between 12 and 16 years of age, with reduced aerobic capacity on a cardiopulmonary exercise test, were included in a three-month, 24-session CPRP. Measurements of the subjects' handgrip strength, biceps brachii and quadriceps femoris strength, and triceps surae fatigue process were collected at the beginning of the program, after completion, and six months after the end of the intervention. A substantial and statistically significant improvement was observed in the subjects' handgrip strength (kg) (p < 0.001), biceps brachii and quadriceps femoris strength (N) (p < 0.001), as well as triceps surae fatigue process (repetitions) (p = 0.018), with a maintenance of the results six months after the intervention. These results suggest that a CPRP could potentially improve the peripheral muscle function of children with CHD. Additional research is needed to confirm and expand on this hypothesis.

Cardiopulmonary Rehabilitation Improves Respiratory Muscle Function and Functional Capacity in Children with Congenital Heart Disease. A Prospective Cohort Study.

Critical surgical and medical advances have shifted the focus of congenital heart disease (CHD) patients from survival to achievement of a greater health-related quality of life (HRQoL). HRQoL is influenced, amongst other factors, by aerobic capacity and respiratory muscle strength, both of which are reduced in CHD patients. This study evaluates the influence of a cardiopulmonary rehabilitation program (CPRP) on respiratory muscle strength and functional capacity. Fifteen CHD patients, ages 12 to 16, with reduced aerobic capacity in cardiopulmonary exercise testing (CPET) were enrolled in a CPRP involving strength and aerobic training for three months. Measurements for comparison were obtained at the start, end, and six months after the CPRP. A significant improvement of inspiratory muscle strength was evidenced (maximum inspiratory pressure 21 cm H2O, 23%, p < 0.01). The six-minute walking test showed a statistically and clinically significant rise in walked distance (48 m, p < 0.01) and a reduction in muscle fatigue (1.7 out of 10 points, p = 0.017). These results suggest CPRP could potentially improve respiratory muscle function and functional capacity, with lasting results, in children with congenital heart disease, but additional clinical trials must be conducted to confirm this finding.

Drying and Rainfall Shape the Structure and Functioning of Nitrifying Microbial Communities in Riverbed Sediments.

Non-flow periods in fluvial ecosystems are a global phenomenon. Streambed drying and rewetting by sporadic rainfalls could drive considerable changes in the microbial communities that govern stream nitrogen (N) availability at different temporal and spatial scales. We performed a microcosm-based experiment to investigate how dry period duration (DPD) (0, 3, 6, and 9 weeks) and magnitude of sporadic rewetting by rainfall (0, 4, and 21 mm applied at end of dry period) affected stocks of N in riverbed sediments, ammonia-oxidizing bacteria (AOB) and archaea (AOA) and rates of ammonia oxidation (AO), and emissions of nitrous oxide (N2O) to the atmosphere. While ammonium (NH4 +) pool size decreased, nitrate (NO3 -) pool size increased in sediments with progressive drying. Concomitantly, the relative and absolute abundance of AOB and, especially, AOA (assessed by 16S rRNA gene sequencing and quantitative PCR of ammonia monooxygenase genes) increased, despite an apparent decrease of AO rates with drying. An increase of N2O emissions occurred at early drying before substantially dropping until the end of the experiment. Strong rainfall of 21 mm increased AO rates and NH4 + in sediments, whereas modest rainfall of 4 mm triggered a notable increase of N2O fluxes. Interestingly, such responses were detected only after 6 and 9 weeks of drying. Our results demonstrate that progressive drying drives considerable changes in in-stream N cycling and the associated nitrifying microbial communities, and that sporadic rainfall can modulate these effects. Our findings are particularly relevant for N processing and transport in rivers with alternating dry and wet phases - a hydrological scenario expected to become more important in the future.

Understanding the effects of predictability, duration, and spatial pattern of drying on benthic invertebrate assemblages in two contrasting intermittent streams.

In the present study, we examined the effects of different drying conditions on the composition, structure and function of benthic invertebrate assemblages. We approached this objective by comparing invertebrate assemblages in perennial and intermittent sites along two intermittent Mediterranean streams with contrasting predictability, duration, and spatial patterns of drying: Fuirosos (high predictability, short duration, downstream drying pattern) and Rogativa (low predictability, long duration, patchy drying pattern). Specifically, we quantified the contribution of individual taxa to those differences, the degree of nestedness, and shifts in the composition, structure and function of benthic invertebrate assemblages along flow intermittence gradients. We observed greater effects of drying on the benthic invertebrate composition in Fuirosos than in Rogativa, resulting in a higher dissimilarity of assemblages between perennial and intermittent sites, as well as a lower degree of nestedness. Furthermore, a higher number of biotic metrics related to richness, abundance and biological traits were significantly different between perennial and intermittent sites in Fuirosos, despite a shorter dry period compared to Rogativa. At the same time, slightly different responses were detected during post-drying (autumn) than pre-drying (spring) conditions in this stream. In Rogativa, shifts in benthic invertebrate assemblages along increasing gradients of flow intermittence were found for three metrics (Ephemeroptera, Plecoptera and Trichoptera (EPT) and Odonata, Coleoptera and Heteroptera (OCH) abundances and aerial active dispersal. Furthermore, we demonstrated that combined gradients of dry period duration and distance to nearest perennial reach can generate complex, and different, responses of benthic invertebrate assemblages, depending on the flow intermittence metric. Our study advances the notion that special attention should be paid to the predictability, duration and spatial patterns of drying in intermittent streams in order to disentangle the effects of drying on benthic invertebrate assemblages, in particular in areas subject to high spatial heterogeneity and temporal variability in drying conditions.

Characterizing the malaria rural-to-urban transmission interface: The importance of reactive case detection.

BACKGROUND: Reported urban malaria cases are increasing in Latin America, however, evidence of such trend remains insufficient. Here, we propose an integrated approach that allows characterizing malaria transmission at the rural-to-urban interface by combining epidemiological, entomological, and parasite genotyping methods. METHODS/PRINCIPAL FINDINGS: A descriptive study that combines active (ACD), passive (PCD), and reactive (RCD) case detection was performed in urban and peri-urban neighborhoods of Quibdó, Colombia. Heads of households were interviewed and epidemiological surveys were conducted to assess malaria prevalence and identify potential risk factors. Sixteen primary cases, eight by ACD and eight by PCD were recruited for RCD. Using the RCD strategy, prevalence of 1% by microscopy (6/604) and 9% by quantitative polymerase chain reaction (qPCR) (52/604) were found. A total of 73 houses and 289 volunteers were screened leading to 41 secondary cases, all of them in peri-urban settings (14% prevalence). Most secondary cases were genetically distinct from primary cases indicating that there were independent occurrences. Plasmodium vivax was the predominant species (76.3%, 71/93), most of them being asymptomatic (46/71). Urban and peri-urban neighborhoods had significant sociodemographic differences. Twenty-four potential breeding sites were identified, all in peri-urban areas. The predominant vectors for 1,305 adults were Anopheles nuneztovari (56,2%) and An. Darlingi (42,5%). One An. nuneztovari specimen was confirmed naturally infected with P. falciparum by ELISA. CONCLUSIONS: This study found no evidence supporting the existence of urban malaria transmission in Quibdó. RCD strategy was more efficient for identifying malaria cases than ACD alone in areas where malaria transmission is variable and unstable. Incorporating parasite genotyping allows discovering hidden patterns of malaria transmission that cannot be detected otherwise. We propose to use the term "focal case" for those primary cases that lead to discovery of secondary but genetically unrelated malaria cases indicating undetected malaria transmission.

The effect of water salinity on wood breakdown in semiarid Mediterranean streams.

Saline streams occur naturally and they are distributed worldwide, particularly in arid and semiarid regions, but human activities have also increased their number in many parts of the world. Little attention has been paid to assess increasing salt effects on organic matter decomposition. The objectives of this study were to analyse wood breakdown rates and how salinity affects them in 14 streams that exemplify a natural salinity gradient. We also analysed the effect of this gradient on changes in wood chemical composition, fungal biomass and microbial activity. Our results showed low breakdown rates (0.0010-0.0032 d(-1)), but they fell within the same range as those reported in freshwater streams when a similar woody substrate was used. However, salinity had a negative effect on the breakdown rates and fungal biomass along the salinity gradient, and led to noticeable changes in wood composition. Water salinity did not affect microbial activity estimated using hydrolysis of fluorescein diacetate. Variation in breakdown rates and fungal biomass across streams was mediated mainly by salinity, and later by stream discharge. Despite the role of fungi in stick breakdown, the potential wood abrasion by salts must be analysed in detail to accurately understand the effect of increasing salinity on organic matter breakdown. Finally, our results indicate that increased salinity worldwide by human activities or by the global warming would imply organic matter breakdown and mineralisation slowing down, even in natural saline streams. However, because many variables are implicated, the final effect of climatic change on organic matter decomposition in streams is difficult to predict.

Ensayo no aleatorizado de un programa de fisioterapia continuo frente a interválico para pacientes con sobrepeso y síndrome coronario agudo / Non-randomized trial to evaluate a continuous physiotherapy program versus interval in overweight patients suffering from acute coronary síndrome

Presentamos un ensayo no aleatorizado de un programa de fisioterapia continuo frente a interválico para pacientes con sobrepeso y síndrome coronario agudo. OBJETIVO: Detectar diferencias entre un programa de fisioterapia (PF) continuo (CONT) y uno interválico (INT) en pacientes con sobrepeso y síndrome coronario agudo, respecto a parámetros antropométricos, analíticos, frecuencia cardiaca de reposo, adherencia a la intervención, desgaste, seguridad y tolerancia. DISEÑO: Estudio multicéntrico cuasiexperimental con diseño pre-post, no aleatorizado con muestreo por conveniencia con 2 brazos de tratamiento. Emplazamiento: Centros de prevención cardiaca comunitaria (Departamentos de Salud Manises, Valencia-La Fe, Játiva-Onteniente). PARTICIPANTES: Se consideró a 339 sujetos con sobrepeso y síndrome coronario agudo que vivían en la comunidad; mayores de 18 años; sin contraindicación para realizar ejercicio físico; sin participación previa en PF. INTERVENCIONES: Se realizó un PF con entrenamiento CONT o uno con entrenamiento INT (2 meses). Cada sesión se dividió en calentamiento, esfuerzo y enfriamiento. El esfuerzo se realizó a intensidad 12-13 Borg y con frecuencia cardiaca calculada según la máxima obtenida en ergometría basal. Mediciones principales: Se analizó el índice de masa corporal, perímetro abdominal, perfil lipídico, glucemia, hemoglobina glicosilada, frecuencia cardiaca de reposo, adherencia, desgaste, seguridad y tolerancia. RESULTADOS: El grupo CONT mostró diferencias significativamente mejores en las variables índice de masa corporal, perímetro abdominal, colesterol total, colesterol LDL, triglicéridos, HbA1C, glucemia y frecuencia cardiaca de reposo, respecto al PF INT. No hubo diferencias entre grupos respecto a adherencia, desgaste, seguridad y tolerancia. CONCLUSIONES: El grupo CONT produjo mejores resultados en todas las variables excepto en el colesterol HDL. Ambos programas registraron una elevada adherencia, seguridad y tolerancia

We present a non-randomised trial to evaluate a continuous physiotherapy program versus a periodic one in overweight patients suffering from acute coronary syndrome. AIM: To detect differences between a continuous (CONT) physiotherapy program (PF) and a periodic (INT) physiotherapy program in overweight patients with acute coronary syndrome on anthropometric parameters, analytical parameters, heart rate, adherence, drop-outs, safety and tolerance. DESIGN: A multicentre, non-randomised two-armed quasi-experimental study with pre-post design. LOCATION: Community cardiac prevention centres (Manises, Valencia-LaFe, Játiva-Onteniente Health Department). PARTICIPANTS: The study included a total of 339 overweight participants with acute coronary syndrome; living in the community; aged more than 18; no contraindication for physical exercise; no previous participation in a PF. INTERVENTIONS: Participants were assigned to a CONT training or an INT training (2 months). Each session was divided in warm-up, endurance, and cool-down. Endurance was performed at 12-13 Borg intensity and with heat rate calculated, with maximum heat rate obtained in the baseline ergometry. MAIN MEASUREMENTS: Body mass index, waist circumference, lipid profile, blood glucose, glycosylated haemoglobin, resting heat rate, adherence, drop-outs, safety, and tolerance were assessed. RESULTS: The CONT group showed significantly better differences in body mass index, waist circumference, total cholesterol, triglycerides, blood glucose, glycosylated haemoglobin and resting heat rate. No differences were observed in adherence, drop-outs, safety, and tolerance. CONCLUSIONS: The CONT group obtained better results in all variables except for HDL cholesterol. Both programs offered a high adherence, safety, and tolerance

Establishing physico-chemical reference conditions in Mediterranean streams according to the European Water Framework Directive.

Type-specific physico-chemical reference conditions are required for the assessment of ecological status in the Water Framework Directive context, similarly to the biological and hydro-morphological elements. This directive emphasises that natural variability of quality elements in high status (reference condition) needs to be quantified. Mediterranean streams often present a marked seasonal pattern in hydrological, biological and geochemical processes which could affect physico-chemical reference conditions. This study establishes general physico-chemical reference conditions (oxygenation, nutrient, salinity and acidification conditions) for different Mediterranean stream types. 116 potential reference sites located in 23 Mediterranean catchments in Spain were sampled in spring, summer and autumn in 2003. All sites were subjected to a screening method for the selection of reference sites in Mediterranean streams (Mediterranean Reference Criteria) and classified using a pre-established stream typology that establishes five different stream types (temporary streams, evaporite-calcareous at medium altitude, siliceous headwaters, calcareous headwaters and large watercourses). Reference conditions (reference value and reference threshold equivalents to high-good class boundary) were calculated using two different methods according to the availability of reference sites: the reference site 75th percentile approach of all reference sites and the 25th percentile of the population approach. The majority of the studied potential reference sites (76 out of 116) were selected as reference sites. Regarding type-specific reference conditions, only siliceous headwaters could be considered different from the rest of stream types because lower conductivity and pH. All reference stream types presented seasonal differences as regards some parameters, except for temporary streams due to the high natural variation of this stream type. For those parameters which presented seasonal differences in a specific stream type, the least restrictive values were proposed as reference conditions.

Los contratos de concesión administrativa de servicios públicos en el sector de telecomunicaciones

Plantea sobre la capacidad de la administración pública para contratar; es más resulta evidente que éste es uno de los medios más eficaces de participación de los particulares en la gestión del bien común, perseguido por el Estado