ABSTRACT
Increased use of technology-critical elements (TCEs) like lithium (Li), and their socio-environmental impacts, make it an issue of national and global importance. In Portugal, new Li exploration/exploitation projects are a very likely scenario. Thus, it is essential to establish geochemical backgrounds/thresholds for Li in soil, which can have several applications. Here, Li contents were determined and mapped from a previous low-density geochemical survey that covered the entire continental area of Portugal, following UNESCO's IGCP 259 project recommendations. The sampling sites were chosen in undisturbed/uncultivated land to ensure a reliable representation of "natural" soils. A total of 152 samples (0-20 cm; <2 mm) were taken for this study. Soil Li analysis was carried out by Flame Atomic Absorption Spectrometry (FAAS) after aqua regia (AR) extraction (geoavailable Li), while a subset of 55 samples underwent further digestion with a strong acid mixture to measure total Li (FAAS). This was done to ascertain the relationship between the two Li fractions and its environmental significance. Soil Li spatial distribution was produced with GIS software. Median values of 14 mg/kg for geoavailable Li and 60 mg/kg for total Li were estimated from these datasets. The first value is comparable to the median Li (11 mg/kg) from an AR-extraction for agricultural/grazing soils in Europe (GEMAS project). Based on spatial analysis, Cambisols overlying granitoids in northern/central Portugal contain the highest AR-extractable Li (40 mg/kg). Such areas are recognized for hard-rock Li mineralizations, mainly associated with aplite-pegmatites. Principal Component Analysis identified an important Li-Al relationship, linked to Cambisols and Leptosols overlying granitoids/metamorphic rocks. The geoavailable/total Li ratios revealed that >60 % of the samples have a relatively high proportion (>45 %) of Li that can be mobilized/dispersed in the surface environment. These findings are intended to support the management of potential concerns regarding Li mining in mainland Portugal.
ABSTRACT
In the present study, trace elements (TE) levels were evaluated in scalp hair along the continuum from healthy subjects (HS) to patients suffering from subjective memory concerns (SMC), and/or mild cognitive impairment (MCI), and those with already installed dementia (DEM) in order to: (i) assess the effects of environmental and lifestyle factors on TE concentrations and (ii) evaluate the analyzed elements as possible diagnostic biomarkers for the disease. The study involved 79 mainly permanent residents, >55 years old, from the city of Estarreja (northern Portugal), a former industrial area. The health status of the participants was assessed by means of a complete socio-demographic questionnaire and through cognitive screening tests, namely the Mini-Mental State Examination (MMSE). The test scores were categorized and used in the statistical analysis. Hair samples were collected and analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) ICP-MS for selected TE. Dementia appears to be associated with higher age, the female gender, lower education level, and longer residence time in the study area. In addition, most of the participants diagnosed with dementia frequently consume home-grown foodstuffs, some irrigated with contaminated well water. The calculation of the TE enrichment factors of soil samples collected in kitchen gardens/small farms in the vicinity of the Estarreja Chemical Complex (ECC) reinforces the degree of Hg soil contamination in the area, due to anthropogenic sources that can be a source for the population Hg exposure route among others. Mercury levels in hair differed significantly between the four individual groups (HS, SMC, MCI, and DEM), increasing from healthy to dementia participants. Improved diagnostic results can be obtained using hair TE signatures coupled with MMSE scores. This strategy may prove useful for predictive diagnosis in population screening for cognitive impairment.
