Use of Piptatherum miliaceum to enable the establishment success of Salvia rosmarinus in Technosols developed from pyritic tailings.

With this study we aimed to assess the effect of the prior development of Piptatherum miliaceum (Pm) in a Technosol on the establishment of Salvia rosmarinus (Sr) as a cash crop. An experimental pot was performed with two biochar (BCh) doses (BCh1 and BCh2) mixed with marble waste and pyritic tailings, with and without Pm. After 12 months of Pm growth, the pots with this species were divided into two sets: Sr alone and Sr + Pm. An agricultural soil (AGR) was used as an external control. The results showed that the growth of Sr led to similar shoot biomass to AGR. Sr + Pm reduced shoot biomass by 50%. Total soil organic and recalcitrant C, and total and recalcitrant N showed the highest values in vegetated pots, with no effect of the BCh rate. The decrease in the soil metals availability was related with increases in soil pH. BCh1Sr + Pm treatment showed a microbial community structure more similar to AGR, related to higher fungal and bacterial abundance, enzyme activities and soluble carbon. Thus, growing Sr + Pm seems a suitable strategy to improve soil properties, including microbial abundance, with low translocation of metals. Although the BCh rate did not affect plant growth or soil physicochemical properties, the lowest rate contributed to the growth of soil microorganisms better. The simultaneous growth of Sr + Pm reduced biomass production, and a source of available nutrients is also recommended. Further studies are needed to test this strategy in the field, and to ensure its suitability and a constant biomass production.

Atmospheric dust characterisation in the mining district of Cartagena-La Unión, Spain: Air quality and health risks assessment.

Nowadays, air pollution has a major impact on the environment and human health. Owen gauges allow the sampling of atmospheric depositions in polluted sites for further characterisation. This paper shows the study of the air particles of an old mining zone in Cartagena-La Unión (South-east of Spain) in order to quantify their potential risk on human health. There were 4 strategic sites monitored: the main mining tailing (Avenque), the urban area (La Unión), an agricultural zone (formerly mining) and a site in the Mediterranean coast. Physico-chemical and mineralogical characterisation was applied to atmospheric fallouts. The granulometry revealed a dust particle size around 15 µm, with the coarsest particles in the urban area and the thinnest at the tailing site. XRD analyses showed the presence of quartz, carbonates, sulphides and sulphates. Observations with SEM-EDX confirmed chemical spectra and allowed us to classify the particles into well-crystallised minerals and heterogeneous dusts. Total metal content determination was carried out by ICP-MS analyses and results showed Zn, Pb, As and Cd fluxes (respectively 2549, 1275, 68 and 7 µg·m-2·d-1) exceeding the limit values set by European legislations in the mining area. The fluxes of Zn, Pb and As also exceed these standards in the urban area whereas the coastal zone only exceeds the thresholds in the case of As. Inhalation health risk (defined by US EPA, 2009) was quantified in the sites using total and bioaccessible metal contents of the dusts. Risk calculations using total metal content considering a residential scenario showed acceptable risk for all sites except for the mining tailing which presented non-acceptable cancer and hazard risk mainly due to the total As and Pb contents. When considering the bioaccessible fraction of As and Pb, the risk diminished to acceptable values, demonstrating the overestimation produced when using total metal contents.