Nitrate and Phosphorus Transport in a Galician River (NW Iberian Peninsula): Insights From Fourteen Years of Monitoring

This article is part of the special issue Current Research on Soil Science and Related Aspects of Environmental Sciences in Galicia[Abstract] The long-term development of water quality metrics is critical to estimate the status of water resources and successful catchment management. This study looks at the temporal evolution of nitrate and phosphorus loads and concentrations in a stream draining rural catchment in Galicia (NW Iberian Peninsula) during 14 hydrological years. The concentrations of both nutrients are relatively low because of the rural nature of the research catchment and low-intensity agriculture. However, catchment nutrient reference levels were widely exceeded. The hydrology controls nutrient fluxes as flow is the main driver of nutrient transfer. For both nutrients there were no consistent trends in nutrient fluxes. The analysed nutrients, however, have been seen to behave differently. As a result, N seems to be decreasing, mainly due to decreased transit in the autumn and spring. Phosphorus, which is primarily transported as particulate matter, exhibits an increase in winter linked to a greater flow and sediment transfer.This research was carried out within the projects REN2003-08143, funded by the Spanish Ministry of Education and Science, and PGIDIT05RAG10303PR and 10MDS103031PR, financed by the Xunta of GaliciaXunta de Galicia; PGIDIT05RAG10303PRXunta de Galicia; 10MDS103031P

Aluminum Geochemical Characterization in Agricultural Soils: Sequential Chemical Extraction Combined With Mineralogical Analysis of the Fine Fraction

Paper of 6th World Multidisciplinary Earth Sciences Symposium 7-11 September 2020, Prague, Czech Republic[Abstract] Understanding both the concentration and distribution of aluminum (Al) in agricultural soils is essential to provide a benchmark on the productivity of such soils. In this study, a combination of sequential chemical extraction and mineralogical investigation of the fine fraction was used in order to evaluate Al pools in agricultural soils in Galicia (NW Spain), an Atlantic European region where the wet climate favors leaching of soil basic cations. Determination of Al (soluble/exchangeable/specifically adsorbed, bound to manganese oxides, associated with amorphous compounds, bound to oxidizable organic matter, associated with crystalline iron oxides, and residual fraction) in the topsoil samples was performed to evaluate its potential environmental availability in the study area. Aluminum contents were determined by flame atomic absorption spectrophotometry and the mineralogy of the fine fraction of these soils was studied by X-ray diffraction (XRD). The results showed that Al is mainly in the residual phase, which represents Al incorporated in the lattice minerals, and consequently the threat of toxicity to plants and the environment is reduced. The XRD results showed the presence of hydroxy-Al interlayered vermiculites and kaolinite, accompanied by small amounts of goethite, mica, and quartz.This paper is a contribution to the Project CGL2014-56907-R of the National Program of Research, Development and Innovation Oriented to the Challenges of Society, which was funded by the Spanish Ministry of Economy and Competitiveness. M. L. Rodríguez-Blanco has been awarded a postdoctoral research contract (Juan de la Cierva Programme), which was funded by the Spanish Ministry of Economy and Competitiveness

An Assessment of the Recent Evolution of the Streamflow in a Near-Natural System: A Case Study in the Headwaters of the Mero Basin (Galicia, Spain)

[Abstract] Observational trend analysis is fundamental for documenting changes in river flows and placing extreme events in their longer-term historical context. Observations from near-natural catchments, i.e., with little or no alteration by humans, are of great importance in detecting and attributing streamflow trends. The purpose of this study is to analyze the annual and seasonal trends of stream discharge (mean, low and high flows) in a headwater catchment in NW Spain, i.e., in the wettest corner of the Iberian Peninsula. The results showed no significant decrease in the mean annual stream discharge. However, significantly lower summer and autumn mean stream discharge and an increase in low flow period were detected, in addition to lesser autumn high flow. The rainfall pattern followed an upward trend, but was not significant. This different pattern shown by rainfall and discharge indicates that is not sufficient to explain the observed trend in stream discharge. Air temperature, most notably by enhancing evapotranspiration, may explain the altered patterns of stream discharge.Xunta de Galicia; 10MDS103031Ministerio de Economía y Competitividad; CGL2014-56907-

Evaluation of Cu and Zn Content in Soils and their Interaction with Some Physicochemical Soil Properties

[Abstract] The content of metals in soils depends on the combined effect of several factors, which include the properties of the metals themselves and their concentrations in the soil, environmental conditions and soil components. Topsoil samples from different plots of a rural area, which combines reforestation (forests soils) with agriculture (pasture and cultivation soils) and livestock in the Galicia region, NW Spain, were analyzed for total Cu and Zn, pH, organic matter content, and particle size distribution. The geological substrate of the study area is mainly biotitic schist. The aims of this study were to investigate the total Cu and Zn concentrations in the topsoil samples, and to examine the relationship of these metals with the mentioned physicochemical properties using a correlation analysis. Soils were characterized by conventional analytical methods. Total Cu and Zn contents were determined by atomic absorption spectrophotometry after wet digestion with a hot mixture of nitro-perchloric-hydrofluoric acids. The results showed that the soils have on average moderately acid pH, considerable organic fraction and clay loam texture. The total Cu and Zn concentrations were low (mean about 25 mg kg-1 and 78 mg kg-1 respectively), which reveals that these topsoils are not contaminated. The statistical analysis showed positive correlations between the sum of the clay and silt contents, and the total Cu and Zn concentrations. There are no significant correlations between total Cu and Zn, and organic matter content.Xunta de Galicia; 10MDS103031Ministerio de Economía y Competitividad; CGL2014-56907-

Medida del microrrelieve del suelo y estimación de la retención hídrica en depresiones de la superficie

[Resumen] Los objetivos de este trabajo son analizar el efecto de la precipitación sobre el microrrelieve de la superficie del suelo y calcular la retención en microdepresiones a partir de una red de datos de altura. Mediante un rugosímetro láser se midieron perfiles en un recipiente con suelo procedente del horizonte de laboreo de un Cambisol crómico, antes y después de lluvia artificial. La superficie inicial intenta reproducir un lecho de siembra. Las superficies sucesivas se describieron mediante modelos de elevación digital con celdillas de 2 mm y resolución en altura de 0,25 mm. Índices de rugosidad como la desviación estándard de la altura o los propuestos por Linden y Van Doren (1986) permiten seguir la evolución del microrrelieve. La retención máxima en microdepresiones para el estado inicial es de 1mm, cifra que se reduce substancialmente por acción de la precipitación.[Abstract] The main objectives of this study were to investigate how rainfall energy affects soil surface microrelief and to calculate depressional surface storage from grid elevation data. A non-contact laser profile meter was used to measure hight profiles of boxes filled with soil from the plough layer of a Chromic cambisol before and after simulated rain. The studied surface was thought to simulate a seedbed. Digital elevation models of the soil surfaces were developed with a resolution in hight of 0.25 mm and a grid spacing of 2 mm. Roughness indices, such as the standard deviation of hights, and the limiting slope and limiting difference, according to Linden and Van Doren (1986) were found to be sensitive to surface microrelief variations. Maximum microdepression storage was 1 mm for a horizontal initial surface, but was substantially reduced by subsequent rainfall

Relationship of Weather Types on the Seasonal and Spatial Variability of Rainfall, Runoff, and Sediment Yield in the Western Mediterranean Basin

[Abstract] Rainfall is the key factor to understand soil erosion processes, mechanisms, and rates. Most research was conducted to determine rainfall characteristics and their relationship with soil erosion (erosivity) but there is little information about how atmospheric patterns control soil losses, and this is important to enable sustainable environmental planning and risk prevention. We investigated the temporal and spatial variability of the relationships of rainfall, runo , and sediment yield with atmospheric patterns (weather types, WTs) in the western Mediterranean basin. For this purpose, we analyzed a large database of rainfall events collected between 1985 and 2015 in 46 experimental plots and catchments with the aim to: (i) evaluate seasonal di erences in the contribution of rainfall, runo , and sediment yield produced by the WTs; and (ii) to analyze the seasonal e ciency of the di erent WTs (relation frequency and magnitude) related to rainfall, runo , and sediment yield. The results indicate two di erent temporal patterns: the first weather type exhibits (during the cold period: autumn and winter) westerly flows that produce the highest rainfall, runo , and sediment yield values throughout the territory; the second weather type exhibits easterly flows that predominate during the warm period (spring and summer) and it is located on the Mediterranean coast of the Iberian Peninsula. However, the cyclonic situations present high frequency throughout the whole year with a large influence extended around the western Mediterranean basin. Contrary, the anticyclonic situations, despite of its high frequency, do not contribute significantly to the total rainfall, runo , and sediment (showing the lowest e ciency) because of atmospheric stability that currently characterize this atmospheric pattern. Our approach helps to better understand the relationship of WTs on the seasonal and spatial variability of rainfall, runo and sediment yield with a regional scale based on the large dataset and number of soil erosion experimental stations.Ministerio de Economía y Competitividad; CGL2014 52135-C3-3-RMinisterio de Economía y Competitividad; ESP2017-89463-C3-3-RMinisterio de Economía y Competitividad; CGL2014-59946-RMinisterio de Economía y Competitividad; CGL2015-65569-RMinisterio de Economía y Competitividad; CGL2015-64284-C2-2-RMinisterio de Economía y Competitividad; CGL2015-64284-C2-1-RMinisterio de Economía y Competitividad; CGL2016-78075-PMinisterio de Economía y Competitividad; GL2008-02879/BTEMinisterio de Economía y Competitividad; LEDDRA 243857Ministerio de Economía y Competitividad; CGL2017-83866-C3-1-RMinisterio de Economía y Competitividad; PCIN-2017-061/AEIGobierno de Aragón; E02_17ROrganización para la Cooperación y el Desarrollo Económicos; TAD/CRP JA00088807Junta de Castilla y León; CLU-2018-04Ministerio de Economía y Competitividad; FJCI-2017-3365