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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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 Runoff, nutrients, sediment and salt yields in an irrigated watershed in southern Navarre (Spain)(Elsevier, 2018) Merchán Elena, Daniel; Casalí Sarasíbar, Javier; Valle de Lersundi, Jokin del; Campo-Bescós, Miguel; Giménez Díaz, Rafael; Preciado, Beatriz; Lafarga, Alberto; Landa Ingeniaritza eta Proiektuak; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; Proyectos e Ingeniería RuralThe environmental impact of irrigated agriculture on water quality was assessed in Landazuria watershed (Navarre, northeast Spain), a 479.5 ha watershed with 53% of irrigated agricultural land. In the framework of a long-term monitoring program, precipitation and discharge were measured at 10-min intervals and compound daily water samples were collected during the agricultural years (September to August) 2007–2016, and analysed for nitrate (NO3−), phosphate (PO43−), sediment and total dissolved solids (TDS) concentrations. Typical agricultural management (including crop surfaces, irrigation and fertilization rates) was obtained from inquiries to farmers. Concentration and yield of the studied variables presented a high degree of variation, both intra- and inter-annual. Median concentration for the entire study period were 185, <0.05, 31 and 2284 mg L−1 for NO3−, PO43−, sediment and TDS, respectively. NO3−-N and PO43−-P yields averaged 74 and 0.04 kg ha−1 year−1, respectively. NO3 −-N yield was higher than in other agricultural land uses in Navarre and in the order of magnitude of other irrigated areas in the Middle Ebro Valley. PO43−-P yield was in the same order of magnitude than in rainfed watersheds in Navarre but lower than in intensively grazed watersheds. Sediment yield was extremely variable, averaging 360 kg ha−1 year−1, with 44% of the total measured load recorded in a few days. It was in the lower range of those measured in Navarre for rainfed agriculture and similar to those estimated in other irrigated areas of the Middle Ebro River. TDS concentration presented a significant decreasing trend since available salts were being washed out, while TDS yield averaged 1.8 Mg ha−1 year−1. Long-term monitoring of irrigated areas is required to understand pollution processes in these agroecosystems and to adequately characterize the environmental impact of current agricultural practices on water quality, in order to implement, and adequately assess, measures to reduce agricultural pollution.Publication Open Access Grey water footprint as an indicator for diffuse nitrogen pollution: the case of Navarra, Spain(Elsevier, 2019) Martínez Aldaya, Maite; Rodríguez, Corina Iris; Fernández Poulussen, Álex; Merchán Elena, Daniel; Beriain Apesteguía, María José; Llamas, Ramón; Ingeniaritza; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; IngenieríaNitrogen is an essential element for plant growth, while its application and associated pollution is a worldwide concern. Generally, diffuse source pollution and its impacts on ecosystem health are difficult to monitor and regulate. Here we used the grey water footprint (GWF) and water pollution level (WPL) indicators, based on a soil nitrogen balance approach to differentiate between surface and groundwater, in order to better understand and quantify the pressure that nitrogen fertilisation generates on freshwater. For the first time, we compared the results of these indicators with actual nitrogen concentration data in surface and groundwater bodies, showing in both cases a positive significant correlation according to Spearman correlation coefficient. This means that the theoretical WPL results might be valuable to anticipate and identify nitrate pollution in surface and groundwater bodies. However, several factors influence the N-related processes that should be considered, such as natural attenuation. We estimated the agricultural and livestock nitrogen loads delivered to freshwater and the associated GWFs and WPLs at the municipality level in Navarra. Large GWFs are observed in southern Navarra, particularly in intensive agricultural regions such as Ribera Alta-Aragón and Ribera Baja. We estimated that 64% of the GWF related to nitrogen loads came from artificial fertilisers, 16% from manure, 11% from atmospheric deposition and the remaining 9% from biological fixation, seeds and other organic fertilisers. Among the crops, cereals had the largest contribution to the nitrogen-related GWF (54%) followed by vegetables (17%) and fodder (11%).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 Dissolved solids and suspended sediment dynamics from five small agricultural watersheds in Navarre, Spain: a 10-year study(Elsevier, 2019) Merchán Elena, Daniel; Luquin Oroz, Eduardo Adrián; Hernández García, Iker; Campo-Bescós, Miguel; Giménez Díaz, Rafael; Casalí Sarasíbar, Javier; Valle de Lersundi, Jokin del; Ingeniaritza; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; Ingeniería; Universidad Pública de Navarra / Nafarroako Unibertsitate PublikoaDissolved solids (DS) and suspended sediment (SS) loads are considered relevant environmental problems. They are related to a wide range of on-site and off-site impacts, such as soil erosion or salinization of water bodies. In this study, the dynamics of DS and SS concentrations and loads were assessed in five small watersheds covering representative agricultural land uses in Navarre (Spain). To this end, discharge, DS and SS concentration data were collected during ten hydrological years at each watershed outlet, and loads were computed from discharge and concentration values. DS concentration followed a seasonal pattern imposed by the availability of water, with higher concentrations recorded in low-flow periods and lower concentration in the high-flow period. SS concentration was extremely variable, with a range of 2–4 orders of magnitude in concentration for any specific discharge. Temporal variations (both intra- and inter-annual) in DS loads were explained by differences in runoff, whereas those of SS were not, being the SS loads associated mainly with specific high flow events. These temporal patterns were observed for both agricultural (this study) and non-agricultural (literature) watersheds. From the data in the Navarrese watersheds and those available in the literature, we inferred that agricultural land use, in general, tends to increase the concentration of both DS and SS. Regarding DS and SS yields, the effects of agricultural land use on DS yields are controlled by the changes in runoff rather than the (small) changes in DS concentration. In this sense, land uses changes expected to increase runoff (i.e., a shift from forested to arable or from rainfed to irrigated agriculture) would increase DS yields. On the other hand, agricultural land use tends to increase SS yields, although the effect is highly variable depending on site-specific factors, both natural (e.g., watershed shape) and anthropogenic (e.g., degree of soil conservation practices). In the Navarrese watersheds, DS yields ranged from 1.1 to 2.2 Mg ha−1 year−1 whereas SS yields ranged from 0.3 to 4.3 Mg ha−1 year−1. DS yields seem to dominate under non-agricultural conditions and in most agricultural land uses at the small watershed scale. On the other hand, SS yields dominate in watersheds with increased soil erosion as a consequence of arable land use over erosion-prone watersheds.Publication Open Access Irrigation implementation promotes increases in salinity and nitrate concentration in the lower reaches of the Cidacos River (Navarre, Spain)(Elsevier, 2020) Merchán Elena, Daniel; Sanz, L.; Alfaro, A.; Pérez, I.; Goñi Garatea, Mikel; Solsona, F.; Hernández García, Iker; Pérez, C.; Casalí Sarasíbar, Javier; Ingeniería; IngeniaritzaThe shift from rainfed to irrigated agriculture is associated with a change in the fertilization rates due to increases in expected production and the fact of growing more N demanding crops. In addition, the circulation of irrigation return flows (IRF) mobilizes soluble salts stored in soils or geological materials. As a consequence, it implies severe modifications in the dynamics and total amount of soluble salts and nitrogen exported, especially in semi-arid watersheds. In this study, long-term data collected by the regional authorities was used to assess the effects of irrigation implementation on salinity (using electrical conductivity, EC, as a proxy) and nitrate concentration (NO3 −) after the transformation of ca. 77 km2 from rainfed to irrigated agriculture in the Cidacos River (CR) watershed. The results indicate that water quality in the lower reaches of the CR was significantly modified after the diffuse incorporation of IRF. In contrast, neither EC nor NO3 − were different in those monitoring stations whose contributing watersheds did not include transformed area. In addition, the temporal dynamics in the analysed variables shifted from a rainfed land signal typical in the region to an irrigated land signal, and the hydrochemical type of the CR shifted from mixed-to-Na+-mixed-to-HCO3 – to mostly Na+-mixed type, typical of waters affected by IRF in the region. Groundwater EC and NO3 − also increased in those wells located within the irrigated area. Although there are great uncertainties in the actual amount of salt and N reaching the CR via IRF, the expected contribution of waste water spilled into the CR is minor in comparison to other sources, mostly agricultural sources in the case of N. The observed changes have promoted the designation of the lower reaches of the CR as 'affected' by NO3 − pollution, and the whole CR watershed as a Nitrate Vulnerable Zone, with the emergent question about whether irrigation implementation as carried out currently in Spain is against the environmental objectives of the Water Framework Directive.Publication Open Access Assessment of the main factors affecting the dynamics of nutrients in two rainfed cereal watersheds(Elsevier, 2020) Hernández García, Iker; Merchán Elena, Daniel; Aranguren Erice, Itxaso; Casalí Sarasíbar, Javier; Giménez Díaz, Rafael; Campo-Bescós, Miguel; Valle de Lersundi, Jokin del; Ingeniaritza; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; IngenieríaNutrient dynamics and factors that control nutrient exports were observed in two watersheds, namely Latxaga and La Tejería, with similar climatic and management characteristics throughout 10 years (2007–2016). Similar patterns were observed in intra-annual and inter-annual dynamics with higher NO3 − concentration and NO3 −-N yield during the humid seasons (i.e., winters and hydrological year 2013). Regarding concentration, Latxaga showed a higher decrease of nitrate due to a higher development of vegetated areas. High discharge events produced nitrate dilution due to the presence of tile-drainage at La Tejeria. At Latxaga, where tile-drainage was not observed, an increase in concentration occurred as a response to high discharge events. Comparing both watersheds, La Tejería presented ca. 73 ± 25 mg NO3 − L−1 while at Latxaga, the concentration observed was almost three times lower, with ca. 21 ± 15 mg NO3 − L−1 throughout the study period. Similar patterns were observed for the NO3 −-N yield, with 32 kg NO3 −-N ha−1 year−1 and 17 kg NO3 −-N ha−1 year−1 at La Tejería and Latxaga, respectively. Regarding phosphorous, the observed concentrations were 0.20 ± 0.72 mg PO4 3− L−1 and 0.06 ± 0.38 mg PO4 3− L−1 at La Tejería and Latxaga, respectively, with PO4 3−-P yields being 71 kg PO4 3−-P ha−1 year−1 and 33 kg PO4 3−-P ha−1 year−1. Annual phosphate-P yield distribution in both watersheds followed similar patterns to those observed for the nitrate-N yield, with higher yields in the humid season. Regarding concentration, highly erosive rainfall that occurred in summer, mobilizing sediments and probably generating desorption of phosphorous in the stream channel, increased phosphate concentration. This research adds to the knowledge base regarding the dynamics of nutrients and the controlling factors in complex agricultural systems with Mediterranean characteristics.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.