Approved Abstracts

Application of simulated lung fluid analysis to evaluate the influence of mining and metallurgical processes on the respiratory bioaccessibility of Manganese-bearing soils and wastes.



Author(s): Gutiérrez-Ruiz M.; García T.; Alvarado J.; Amaro-Ramírez D.; Tavares T.; Ceniceros A.; Romero F.; Martínez-Jardines G.; Meza D.;
Presenter: Margarita E. Gutiérrez-Ruiz

Introduction. Manganese (Mn) is an essential element for life and very important to the industry. It plays a vital role in human processes. The absorption, transport, and toxicity of Mn in the human body are determined by the chemical species and its concentration. In excess, the respiration of Mn (PM2.5) is related to neurological damages and neurobehavioral deficits. One of the largest Mn ore reserves in America is in Molango, Mexico. Eolic erosion transports particles from a deposit of minerals and wastes to small towns, increasing the risk to population‘s health. Methodology. The geoavailability and pulmonary bioaccessibility of Mn were measured on particles (PM20) from mining-metallurgic materials and wastes of Molango (metallurgic furnace wastes, concentrates, products, and gangue from gravimetric flotation), using simulated lung fluid (artificial lysosomal fluid). The ALF‘s solution mimics fluid after phagocytosis by alveolar and interstitial macrophages (pH: 4.5) and simulates inflammatory conditions. Additionally, polluted soils and dust from unpaved highways were analyzed because the traffic re-suspension and wind soil erosion seem to be the most critical routes from the Mn exposition. Mn background level in soils of the area was determined, and the main minerals of Mn were identified by XRD and SEM-EDS. Metals were quantified by FXR and ICP-OES. The data from Molango were compared with those obtained in Matehuala, Mexico. In this place, historical and recent mining processes of polymetallic sulfides have impacted the surroundings, and Mn is a less critical pollutant. Results and discussion. The Mn minerals in Molango are: Rhodochrosite (MnCO3), Hausmannite (Mn2+Mn3+2O4), Mn (III) oxide (Mn2O3) and Ramsdellite (Mn4+O2), while in soils from Matehuala seem to be Birnessite (Na0.3Ca0.1K0.1)(Mn4+,Mn3+)2O4 1.5 H2O. The pH values of soils in Molango (5.2-7.6, mean 6) are slightly lower than in Matehuala (7.5-8.4) and like the background level (6.5). The soil E.C. in both places (Molango = 204-2,065 µScm-1, mean 650; and Matehuala =166-1,190 µScm-1, mean=507) are higher than background levels (Molango =98 µScm-1, Matehuala =84 µScm-1) showing the impact of industrial activities. The pH from the dry gravimetric concentration wastes (gangue) from Molango varied from 7.6 to 7.8 and the C.E. from 2,205-2, 505 µScm-1. In the concentrates, the pH‘s are similar, but the C.E. varied from 119 to 2,095 µScm-1. In tailings from Matehuala the pH is higher (7.8-8.7), and slags are alkaline (9.2-9.7). The mean of total Mn of impacted soils from Molango is 2.14 %, the median 1.3 %, and the range 0.14-7.2 %. In Matehuala, the total Mn range is 0.009-0.067%. In concentrates from Molango the total Mn mean is 18.9%, in gangue 3.05%, in products 25.3%, and in wastes 21.17%. Total Mn in Matehuala tailings is 0.10%, and in slag 0.37%. There is a good correlation between total Mn in industrial materials and polluted soils (r >0.98). The geoavailability values of Molango and Matehuala soils (meteoric water and rainwater) were lower than 0.3 mg/kg (LOD) or slightly higher. The pulmonary bioaccessibility percent in Molango varied from 35 to 100%, and in Matehuala from 27 to 84%. Conclusions. The results show that organic ligands of the ALF solution with high ionic strength can dissolve the Mn from slightly soluble minerals. The pulmonary bioaccessibility percents of all materials from Molango calculated from the total concentration were found to be high. Also, the values from Matehuala are relatively high, despite the low total Mn concentrations and their different mineral composition. In Molango, the particles (PM20) from less polluted soils and gangue present the lowest Mn bioaccessibility (35, 38%). The study results indicate the importance of including the pulmonary bioaccessibility of Mn data on the human health risk assessment.

Keywords: Pulmonary Bioaccessibility; Manganese Bioaccessibility; ALF metal application

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