Factors influencing mercury uptake by leaves of stone pine (Pinus pinea L.) in Almadén (Central Spain)

Abstract

The use of trees for biomonitoring of mercury (Hg) and other atmospheric pollutants is of increasing importance today. Leaves from different species have been the most widely used plant organ for this purpose, but only pine bark, and not leaves, was used to monitor Hg pollution. In Almadén (South Central Spain), the largest cinnabar (HgS) deposits in the world have been mined for over 2000 years to obtain metallic Hg and this activity has caused the widespread dispersion of this toxic element in the local environment. A strip of pine trees, 2750 m in length, adjacent and to the South of the mining town has been studied in order to evaluate pine tree needles as monitors for Hg contamination in this heavily polluted area. The study involved the collection of pine tree leaves from several discrete sites along the strip, as well as samples from other nearby locations, together with soil samples and monitoring of atmospheric Hg in the area during both the day and night. Leaves and soils were analyzed for total Hg concentration by means of atomic absorption spectrometry; the leachable fraction of soil Hg was also analyzed by the CV-AFS technique. The results indicate that soils from the investigated area were not directly affected by mining related pollution, with low total Hg levels (3-280 mg kg) found in comparison with the nearby Almadén metallurgical precinct and very low leachable Hg contents (0.27-59.65 mg kg) were found. Moreover, pine tree needles have a low uptake capacity, with lower THg levels (0.03-6.68 mg kg) when compared to those of olive trees in Almadén. However, pine needles do show significant variability with regard to the distance from the source. Gaseous Hg exhibits a similar pattern, with higher levels close to the source, especially during night time (225 ng m). A multiple linear regression analysis (MLRA) revealed that gaseous Hg in the nocturnal period is the prime factor that influences the amount of Hg uptake by pine tree needles. This finding makes pine needles a promising candidate to biomonitor gaseous Hg on a local or regional scale worldwide. Almadén pine tree needles have been exposed to a number of different Hg sources, including the primary one, namely the old mine dump, and secondary sources such as polluted roads or illegal urban residual waste. The secondary sources cause some minor discrepancies in the model established by the MRLA. The biomonitoring capacity of pine needles needs to be evaluated in areas far from the source. The process involved in gaseous Hg uptake by pine needles appears more likely to involve sorption in the external part of the needle than uptake through stomas, thus making this process strongly dependent on high atmospheric Hg concentrations.

The influence of compost and nitrilotriacetic acid on mercury phytoextraction by Lepidium sativum L.

“…The potential leachable fraction of Hg (LHg) was tested on the soil and growing medium samples collected before/after plant cultivation in accordance with procedure described by Barquero et al LHg was extracted by the EPA 1312 method that is designed to determine mobility of both organic and inorganic forms of Hg . Thus, 5 g of solid sample was extracted in 100 mL of H 2 SO 4 /HNO 3 (60/40 m/m) mixture.…”

Contaminated sites, waste management, and green chemistry: new challenges from monitoring to remediation

“…Their detailed analysis of data registered in these sediments, including their precise dating, makes evident that the human activities developed in the area since the beginning of twentieth century have supposed an important increment of the presence of those pollutants in the regional environment; besides, and being the studied accumulations susceptible of erosive processes, they still represent a risk for the future of the area. The presence of mercury in Almadén (Castilla-La Mancha region of Spain) is well known, and the environmental consequences of this fact have been described in a large number of publications; however, Barquero et al (2018) present a novel methodology to quantify the atmospheric contamination related with the fact that this element has a high volatilization potential, being present in the atmosphere of areas in which there is no active sources of direct release of the element to the atmosphere, which is the case for this area after the cessation of mining and metallurgy and the reclamation of the mine's main dump (Tejero et al 2015). In particular, these authors use the bioaccumulation capacity of needles of stone pine to biomonitor the mercury presence in the atmosphere.…”

Experimental assessment of the daily exchange of atmospheric mercury in Epipremnum aureum

“…In the terrestrial environment, these Hg compounds are preferentially found in soils, bound to organic matter, as a product of atmospheric deposition (Si and Ariya 2018). Vegetation plays an important role in the Hg exchange process between the soil and the atmosphere, with Hg acquired from the soil via the roots (Liu et al 2017;Ahammad et al 2018) and from the atmosphere via the leaves (Kowalski and Frankowski 2016;Zheng et al 2017; Barquero et al 2019).…”

“…Plants act as a temporary sink for Hg, and they provide a transfer pathway from the soil to the atmosphere or from the atmosphere to the soil via litterfall. It has been established in numerous studies that direct Hg uptake by plants from the soil is minor compared to the Hg emission/deposition direct from the atmosphere (Assad et al 2016; Kowalski and Frankowski 2016;Zheng et al 2017;Higueras et al 2016; Barquero et al 2019;Esbrí et al 2018). A great deal of effort has been devoted to clarifying gaseous elemental Hg (GEM) fluxes from the soil to the atmosphere, with a global cycle of net emissions reported in warm seasons and negligible flux in colder periods (Sommar et al 2012;Demers et al 2013).…”