A partial least squares-path model of environmental degradation in the Paraopeba River, for rainy seasons after the rupture of B1 tailings dam, Brumadinho, Brazil

Evaluating the surface water quality after the rupture of an iron mining tailings

The aim of this article is to assess whether the collapse of the Fundão tailings dam still impacts the surface water quality of the Doce River in the state of Minas Gerais (Brazil). The records of 15 water quality parameters were evaluated, comparing data from before and after the accident. Nine sampling points were selected, six of which corresponded to water intakes for the water supply systems. The records showed that after the collapse of the Fundão Dam, there was an increase in the percentage of non-conforming values for dissolved Fe, dissolved Al, true color, turbidity, and total suspended solids, but a reduction in total Mn and total Pb, based on the Normative Consideration COPAM/2008. The time series analysis showed no trends, with Levene's test indicating variance changes only for dissolved Fe, total dissolved solids, and dissolved Al. Mann-Whitney tests revealed no median changes in key parameters after the Fundão Dam collapse. For the seven trace metals evaluated (As, Cd, Cr, Pb, Hg, Ni and Zn), the Mann-Whitney and Pettitt tests allow us to infer that there was a change in the median concentrations and an abrupt change in the data series after the dam rupture. It is not possible to associate any plausible cause for the changes observed in some tests and monitoring stations in the records prior to the accident. For records after the accident, the prospect of the Doce River's recovery still lacks greater statistical robustness, emphasizing the relevance of maintenance of water quality monitoring stations in the Doce River channel.

Five years after the Brumadinho dam collapse: Evaluation of water quality based on combined analysis of land use and environmental data

The collapse of the dam in the Paraopeba River watershed in 2019 triggered significant concerns regarding water quality in the region. This study aimed to assess, five years after the disaster, the effects on water quality and understand the underlying factors of environmental pressure contributing to the observed changes. To perform the evaluation, the study utilized surface water quality data pre-disaster (2012-2018) and post-disaster (2019-2023), environmental data regarding the identification of high-polluting potential industries operating in the region of interest, and land use for the watershed as a combined evaluation. Nonparametric statistical tests Kruskal-Wallis, complemented by Dunn's, were employed to assess the significance of changes in water quality parameters post-collapse. The results indicate a relatively stable baseline scenario of land use dominated by agriculture and pasture, with minor changes observed in forest cover and urban development. However, post-collapse assessments showed significant variations in water quality parameters, with turbidity exceeding conformity levels by up to 68 % (over 100 NTU), dissolved iron (Fe) by up to 70 % (over 0.3 mg.L-1), manganese (Mn) by up to 91 % (over 0.1 mg.L-1), dissolved aluminum (Al) by up to 83 % (over 0.01 mg.L-1), and lead (Pb) by up to 26 % (over 0.01 mg.L-1). Statistical tests suggested possible effects of the dam collapse on turbidity, pH, dissolved Fe, Mn, and dissolved Al. Temporal analysis showed constant effects on water quality, with notable increases in dissolved Fe and Mn concentrations observed upstream post-disaster and persistent impacts downstream. New mining activities licensed after 2019 may have contributed to the deterioration of water quality, highlighting the relevant relationship of anthropogenic activities and the environmental disaster in the Paraopeba River watershed.

Modeling and predicting caffeine contamination in surface waters using artificial intelligence and standard statistical methods

Caffeine, considered an emerging contaminant, serves as an indicator of anthropic influence on water resources. This research employs various modeling techniques, including Artificial Neural Networks (ANN), Random Forest (RF), and more, along with hybrid and ensemble methods, to predict caffeine concentrations (in regression and classification scenarios) using readily available water quality parameters. The results indicate Ensemble-RF as the most effective method for estimating caffeine concentrations, while classification scenarios highlight Ensemble-RF, ANN, and Ensemble-ANN as promising methodologies for predicting contamination levels. This study offers a valuable tool for swiftly assessing caffeine contamination in water, leveraging easily obtainable data, with implications for safeguarding water resource systems.

Integrating reverse osmosis to a conventional river water treatment plant as a strategy to produce drinking water after mining dam rupture events: a case study

Incidents of mining dam failure have compromised the water quality, threatening the water supply. Different strategies are sought to restore the impacted area and to guarantee the water supply. One example is water treatment plants that treat high-polluted waters within the required limits for their multiple usages. The current study assesses the integration of reverse osmosis (RO) to a river water treatment plant (RWTP) installed in Brumadinho (Minas Gerais, Brazil) to treat the water from the Ferro-Carvão stream impacted by the B1 dam rupture in 2019. The RWTP started eleven months after the mining dam rupture and is equipped with eight coagulation-flocculation tanks followed by eight pressurised filters. A pilot RO plant was installed to polish the water treated by the RWTP. Water samples were collected at different points of the water treatment plant and were characterised by their physical, chemical, and biological parameters (160 in total). The results were compared with the historical data (1997-2022) to reveal the alterations in the water quality after the rupture event. The compliance with both parameters was only achieved after the RO treatment, which acted as an additional barrier to 30 contaminants. The water quality indexes (WQI) suggested that the raw surface water, even eleven months after the incident, was unfit for consumption (WQI: 133.9) whereas the reverse osmosis permeate was ranked as excellent in the rating grid (WQI: 23.7).

Carbon footprints of tailings dams' disasters: A study in the Brumadinho region (Brazil)

Tailings dams' breaks are environmental disasters with direct and intense degradation of soil. This study analyzed the impacts of B1 tailings dam rupture occurred in the Ribeirão Ferro-Carvão watershed (Brumadinho, Brazil) in January 25, 2019. Soil organic carbon (SOC) approached environmental degradation. The analysis encompassed wetlands (high-SOC pools) located in the so-called Zones of Decreasing Destructive Capacity (DCZ5 to DCZ1) defined along the Ferro-Carvão's stream bed and banks after the disaster. Remote sensed water indices were extracted from Landsat 8 and Sentinel-2 satellite images spanning the 2017-2021 period and used to distinguish the wetlands from other land covers. The annual SOC was extracted from the MapBiomas repository inside and outside the DCZs in the same period, and assessed in the field in 2023. Before the dam collapse, the DCZs maintained stable levels of SOC, while afterwards they decreased substantially reaching minimum values in 2023. The reductions were abrupt: for example, in the DCZ3 the decrease was from 51.28 ton/ha in 2017 to 4.19 ton/ha in 2023. Besides, the SOC increased from DCZs located near to DCZs located farther from the dam site, a result attributed to differences in the percentages of clay and silt in the tailings, which also increased in the same direction. The Ferro-Carvão stream watershed as whole also experienced a slight reduction in the average SOC levels after the dam collapse, from nearly 43 ton/ha in 2017 to 38 ton/ha in 2021. This result was attributed to land use changes related with the management of tailings, namely opening of accesses to remove them from the stream valley, creation of spaces for temporary deposits, among others. Overall, the study highlighted the footprints of tailings dams' accidents on SOC, which affect not only the areas impacted with the mudflow but systemically the surrounding watersheds. This is noteworthy.

A framework model to integrate sources and pathways in the assessment of river water pollution

Metal and nutrient pollution, soil erosion, and alterations in climate and hydrology are prevalent issues that impact the water quality of riverine systems. However, integrated approaches to assess and isolate causes and paths of river water pollution are scarce, especially in the case of watersheds impacted by multiple hazardous activities. Therefore, a framework model for investigating the multiple sources of river water pollution was developed. The chosen study area was the Paraopeba River basin located in the Minas Gerais, Brazil. Besides multiple agriculture, industrial, and urban pollution sources, this region was profoundly affected by the rupture of the B1 tailings dam (in January 2019) at the Córrego do Feijão mine, resulting in the release of metal-rich waste. Considering this situation, thirty-nine physicochemical and hydromorphological parameters were examined in the Paraopeba River basin, in the 2019-2023 period. The analysis involved various statistical techniques, including bivariate and multivariate methods such as correlation analysis, principal component analysis, and clustering. The Paraopeba River was mainly impacted by metal contamination resulting from the dam collapse, whereas nutrient contamination, mainly from urban and industrial discharges, predominantly affected its tributaries. Additionally, the elevated concentrations of aluminum, iron, nitrate, and sulfate in both main river and tributaries can be attributed to diffuse and point source pollution. In terms of hydromorphology and soil type, the interaction between woody vegetation and erosion-resistant soils, especially latosols, contributes to the stability of riverbanks in the main river. Meanwhile, in the tributaries, the presence of neosols and sparse vegetation in urbanized areas promoted riverbank erosion potentially amplifying pollution. While the study was conducted in a particular watershed, the findings are based on a methodology that can be applied universally. Hence, the insights on surface water quality from this research can be a valuable resource for researchers studying watersheds with diverse pollution sources.

Five years after the collapse of the Fundão Dam: lessons from temporal monitoring of chemistry and acute toxicity

In November 2015, the Fundão Dam break released millions of tons of metal-rich tailings into the Doce River Basin (DRB), causing catastrophic damage and potential ecological effects that reached the Atlantic Ocean. This study aimed to evaluate the geochemistry and toxicity of water and sediments collected in the DRB from 2015 to 2019 and to determine the spatial and temporal trends. Water and sediment samples were analyzed for metals and As by inductively coupled plasma optical emission spectrometry (ICP-OES), and acute toxicity for Daphnia similis or D. magna. Results were explored using geochemical indices and correlation analyzes. Overall, higher concentrations of metals and As in water and sediments were observed immediately after dam breakage, but the levels exhibited a decreasing trend over time, although the levels of some elements such as As and Mn remained high in the upper DRB. The geochemical indices indicated mostly low to moderate contamination, and the enrichment factor (EF) demonstrated a higher enrichment of Mn in the upper DRB. Acute toxicity to water fleas (D. similis and D. magna) was occasionally observed in waters and sediments, but the reference samples were toxic, and the short-term effects were not correlated with metals and As. Overall, the results showed limited bioavailability of metals and As and a decreasing trend in their concentrations, indicating an ongoing recovery process in DRB. These results are important to decision-making regarding the disaster and actions for environmental restoration.

Spatial-temporal variations of metals and arsenic in sediments from the Doce River after the Fundão Dam rupture and their bioaccumulation in Corbicula fluminea

The rupture of the Fundão dam in Brazil released tons of mining tailings into the Doce River Basin (DRB). This investigation aimed to determine the bioaccumulation of metals in soft tissues of the bivalve Corbicula fluminea exposed to sediments collected in the DRB in four periods (just after, 1, 3, and 3.5 years after the dam rupture). In the exposure bioassays, the concentrations of Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn in sediments and bivalve soft tissues were quantified. The concentration of some elements (As, Cd, Mn, and Al) in sediments exceeded the federal limits or regional backgrounds at some sampling sites, but their concentrations tended to decrease over time. However, higher concentrations of many elements were detected in the winter of 2019. Several elements were detected in C. fluminea soft tissues, but the bioaccumulation factors were generally low or not related to those elements associated with the ore tailings, evidencing that the bioavailability of metals to bivalves, in laboratory conditions, was limited. Integr Environ Assess Manag 2024;20:87-98. © 2023 SETAC.

Mortality patterns in municipalities of a mining region before the Brumadinho dam failure, state of Minas Gerais, Brazil

OBJECTIVE

To describe the patterns of overall mortality and mortality from external causes and the temporal evolution in the municipalities of the Paraopeba River Basin, before the socio-environmental disaster of the Brumadinho dam and, additionally, to investigate the correlation between mortality and socioeconomic deprivation in these municipalities.

METHODS

Global Burden of Disease Study mortality estimates for 26 municipalities in the state of Minas Gerais, Brazil, were analyzed. Rates of overall mortality and mortality from external causes were estimated in the triennia (T) T1 (2000 to 2002), T2 (2009 to 2011), and T3 (2016 to 2018). Pearson's correlation coefficient measured the association between mortality rates and socioeconomic deprivation, according to the Brazilian Deprivation Index (IBP).

RESULTS

There was a decrease in overall mortality in the Paraopeba River Basin from 717.7/100 thousand to 572.6/100 thousand inhabitants, and in most municipalities between T1-T3. Mortality from external causes increased from 73.3/100 thousand to 82.1/100 thousand, and it was higher in these municipalities compared with the mean for Brazil and Minas Gerais. Deaths from suicide and interpersonal violence increased from 29.6/100 thousand to 43.2/100 thousand in most of the 26 municipalities. Death rates due to unintentional injuries decreased during the period, and those due to transport injuries, increased. There was a positive correlation between socioeconomic deprivation and the percent change in mortality rates.

CONCLUSION

Despite the strong presence of mining activity in the region, such did not reflect in the improvement of the sanitary situation. Death rates due to external causes increased in the period, associated with inequalities, which must be considered in the planning for the recovery of the disaster areas.