José Virgílio Cruz

Linking trace metals and agricultural land use in volcanic soils — A multivariate approach

The concern about the environmental impacts caused by agriculture intensification is growing as large amounts of nutrients and contaminants are introduced into soil ecosystems. Volcanic soils are unique naturally fertile resources extensively used for agricultural purposes, with particular physical and chemical properties that may result in possible accumulation of toxic substances, such as metals. Within this particular geological context, the present study aims to evaluate the impact of different agricultural systems (conventional, traditional and organic) in trace metal (TM) soil pollution and define the tracers for each one. Physicochemical properties and TM contents in agricultural topsoils were determined. Enrichment Factors (EF) were calculated to distinguish geogenic and anthropogenic contribution to TM contents in agricultural soils. An ensemble of multivariate statistical analyses (PCA and FDA) was performed to reduce the multidimensional space of variables and samples, thus defining a set of TM as tracers of distinct agricultural farming systems. Results show that agricultural soils have low organic matter content (<5%) compared to reference soil (>30%); in addition, electric conductivity in conventional farming soils is higher (262.3 ± 162.6 μS cm(-1)) while pH is lower (5.8 ± 0.3). Regarding metal inputs, V, Ba and Hg soil contents are mainly of geogenic origin, while Li, P, K, Cr, Mn, Ni, Cu, Zn, As, Mo, Cd and Pb result primarily from anthropogenic inputs. Li revealed to be a tracer of agricultural pollution in conventional farming soils, whereas V allowed the discrimination of traditional farming soils. This study points to agriculture as a diffuse source of anthropogenic TM soil pollution and is the first step to identify priority chemicals affecting agricultural Andosols.

Periodic behavior of soil CO2 emissions in diffuse degassing areas of the Azores archipelago: Application to seismovolcanic monitoring

Time series of soil CO2 efflux recorded in the Azores archipelago volcanic-hydrothermal areas feature daily and seasonal variations. The recorded CO2 efflux values were lower during summer than in the winter season. The diurnal CO2 efflux values were higher at dawn and lower in the early afternoon, contrary to that observed in biogenic environments. CO2 efflux cycles correlated well with the environmental variables, such as air temperature, wind speed, and barometric pressure, which also showed low- and high-frequency periodicities. Several simulations were performed here using the Transport of Unsaturated Groundwater and Heat 2 (TOUGH2) geothermal simulator to complement the study of Rinaldi et al. (2012). The effects of the water table depth, air temperature perturbation amplitude, and soil thermal gradient contributed to an explanation of the contrasts observed in the diurnal (S1) and semidiurnal (S2) soil CO2 efflux peaks for the different monitoring sites and seasons. Filtering techniques (multivariate regression analysis and fast Fourier transform filters) were also applied to the recorded time series to remove effects of external variables on the soil CO2 efflux. The resulting time series (the residuals) correspond to the best approach to the deep-seated (volcanic/hydrothermal) CO2 emissions and thus should be used in seismovolcanic monitoring programs. Even if no evident correlation can be established yet between the soil CO2 residuals and seismicity over the monitored time, a seismic swarm that occurred around the end of 2008 might have triggered some deviations from the observed daily cycles.

Baseline Levels of Metals in Volcanic Soils of the Azores (Portugal)

Data on metal concentrations present in the soils of the Azores (Portugal) are scarce. The goal of this study was to measure the current levels of several metals in the top horizon of soils of two areas, distinguishable by their volcanic activity and physical characteristics, in order to establish some baseline concentrations of these elements. Soil samples were taken in similar ways from five sites in a volcanically active area and another five sites in an area without volcanic activity. Particle-size fractions, % organic matter, moisture content, pH, and major and trace elements compositions were measured. In general, the concentrations of trace metals in the soils from Santa Maria (inactive volcanism) were higher than those from Furnas (active volcanism), with the exception of Zn. The soils from Furnas, which have slightly lower pH and less % clay-silt than Santa Maria, will probably make such trace metals as Zn become more readily bioaccessible, and therefore pose a larger threat to living organisms inhabiting these soils.

Iodine environmental availability and human intake in oceanic islands: Azores as a case-study

Iodine deficiency is the most common cause of preventable mental impairment. Although several studies have established an association between ocean proximity and iodine environmental availability, recent studies revealed an inadequate iodine intake in the Azorean islands. In this study, we aim to understand the underlying causes of iodine environmental availability in oceanic islands and its association with iodine intake in schoolchildren, using the Azores as case-study. Iodine concentration in soil and grass pasture was measured by INAA and in drinking water by spectrophotometry. Urinary iodine concentration (UIC) in schoolchildren was assessed by ICP-MS in a randomized cross-sectional survey with 315 participants from S. Miguel (study group) and Sta. Maria islands (reference group). A validated diet questionnaire assessing sources of iodine was recorded. The iodine concentration in soils of the reference group was significantly higher than in the study group (58.1ppm vs. 14.5ppm, respectively; p=0.001). The prevalence of schoolchildren with inadequate UIC was significantly higher in the study group than in the reference one (63.0% vs. 37.8%, respectively; p<0.001). Chronic exposure to low iodine environmental availability was significantly associated with the exacerbation in iodine deficiency, with a risk 4.94 times higher in the study group. The differences observed in the studied islands are related with each island geomorphology (soil properties and orography) and climate, which can promote or inhibit iodine environmental availability, contributing distinctively to iodine bioavailability and human intake. These findings draw attention to an urgent need for a full investigation of Azores iodine status to apply evidence-based recommendations for iodine supplementation.