Person: Merchán Elena, Daniel
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Merchán Elena
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Daniel
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Proyectos e Ingeniería Rural
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811294
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Publication Open Access Feasibility of using rural waste products to increase the denitrification efficiency in a surface flow constructed wetland(Elsevier, 2019) Margalef Marti, Rosanna; Carrey, Raúl; Merchán Elena, Daniel; Soler, Albert; Causapé, Jesús; Otero, Neus; Ingeniaritza; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; IngenieríaA surface flow constructed wetland (CW) was set in the Lerma gully to decrease nitrate (NO3-) pollution from agricultural runoff water. The water flow rate and NO3 - concentration were monitored at the inlet and the outlet, and sampling campaigns were performed which consisted of collecting six water samples along the CW flow line. After two years of operation, the NO3 -attenuation was limited at a flow rate of ~2.5 L/s and became negligible at ~5.5 L/s. The present work aimed to assess the feasibility of using rural waste products (wheat hay, corn stubble, and animal compost) to induce denitrification in the CW, to assess the effect of temperature on this process, and to trace the efficiency of the treatment by using isotopic tools. In the first stage, microcosm experiments were performed. Afterwards, the selected waste material was applied in the CW, and the treatment efficiency was evaluated by means of a chemical and isotopic characterization and using the isotopic fractionation (ε) values calculated from laboratory experiments to avoid field-scale interference. The microcosms results showed that the stubble was the most appropriate material for application in the CW, but the denitrification rate was found to decrease with temperature. In the CW, biostimulation in autumn-winter promoted NO3-attenuation between two weeks and one month (a reduction in NO3- between 1.2 and 1.5 mM was achieved). After the biostimulation in spring-summer, the attenuation was maintained for approximately three months (NO3 - reduction between 0.1 and 1.5 mM). The ε15NNO3/N2 and ε18ONO3/N2 values obtained from the laboratory experiments allowed to estimate the induced denitrification percentage. At an approximate average flow rate of 16 L/s, at least 60 % of NO3 -attenuation was achieved in the CW. The field samples exhibited a slope of 1.0 for δ18O-NO3 -versus δ15N-NO3 -, similar to those of the laboratory experiments (0.9-1.2). Plant uptake seemed to play a minor role in NO3 - attenuation in the CW. Hence, the application of stubble in the CW allowed the removal of large amounts of NO3 - from the Lerma gully, especially when applied during the warm months, but its efficacy was limited to a short time period (up to three months).Publication Open Access Shifts in crane migration phenology associated with climate change in Southwestern Europe(Resilience Alliance, 2020) Orellana Macías, J. M.; Bautista, Luis M.; Merchán Elena, Daniel; Causapé, Jesús; Alonso, Juan Carlos; Ingeniería; IngeniaritzaGallocanta lagoon, NE Spain, is one of the main stopover and wintering areas of Common Cranes (Grus grus) migrating through Western Europe. We investigated how the water level of the lagoon where cranes roost, precipitation, and air temperature might have influenced the species’ migration and wintering patterns in this area between 1973 and 2018. Over the study period, the mean annual air temperature increased at 0.3 °C per decade. Simultaneously, cranes advanced the spring peak migration date at a rate of 0.37 days/year. Water level and rainfall during spring were also positively correlated with the date of spring migration peak. Because cranes need shallow water to roost, and must drink water from streams because the lagoon is saline, these correlations suggest that low water levels at roosting sites and drinking water shortage may have further accelerated the onset of northward spring migration. The water level was also positively correlated with peak crane numbers in autumn, suggesting that the roosting capacity of the lagoon may limit numbers of cranes that can stopover in the area. We conclude that global warming, variations in the water level of the lagoon, and precipitation during spring have determined changes in the use of Gallocanta as a staging and wintering area by Common Cranes during the last decades. Because climatic models predict further decreases in rainfall and higher temperatures in the area, further advances in the migration phenology of cranes should be expected, which might also have implications for the conservation and management of the species and the study area.Publication Open Access Evolution and assessment of a nitrate vulnerable zone over 20 years: Gallocanta groundwater body (Spain)(Springer, 2020) Orellana Macías, J. M.; Merchán Elena, Daniel; Causapé, Jesús; Ingeniaritza; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; IngenieríaNitrate pollution from agricultural sources is one of the biggest issues facing groundwater management in the European Union (EU). During the last three decades, tens of nitrate vulnerable zones (NVZ) have been designated across the EU, aiming to make the problem more manageable. The Gallocanta Groundwater Body in NE Spain was declared as an NVZ in 1997, and after more than 20 years, significant improvements in water quality were expected to be observed. In the present study, the spatiotemporal trend of nitrate concentration within the Gallocanta NVZ in the last 38 years was assessed, and the effectiveness of the NVZ implementation was tested. Data from the official Ebro Basin Confederation monitoring network from 1980 to 2018 were used, and the results showed an increasing but fluctuating trend in nitrate concentration since 1980. Although a slight improvement was detected after the NVZ designation in 1997, the low rate of improvement would take decades to reach desirable levels in most of the area. The lack of update and control of action programmes, the inappropriate NVZ delimitation, and the influence of natural factors seem to be the reasons for the failure of the nitrate reduction measures. Currently, nitrate pollution and groundwater management are a matter of concern for the EU, so given the recurring problems in water supply in the area and the nonfulfillment of the goal of good quality status, more demanding measures are needed to be implemented in the short term.