Water quality of streams associated with artisanal gold mining; Suárez, Department of Cauca, Colombia

Surface water quality of the Magdalena River in the Colombian Caribbean: future solutions for treatment wastewaters

The treatment of water quality has gained global importance due to the increasing pressure on freshwater ecosystems from anthropogenic activities. In this context, hydrological quality studies are essential to develop and implement new strategies for water resource management, particularly in port areas where industrial and urban pressures converge. This study presents a comprehensive multitemporal assessment of surface water quality in the Magdalena River near the Palermo Sociedad Portuaria (Colombia), integrating physical, chemical, and microbiological parameters from 2016 to 2023. Two monitoring points (P1 upstream and P2 downstream) were analyzed using a suite of pollution indices WQI, ICOMI, ICOMO, ICOSUS, ICOTRO, and ICOpH along with two-way ANOVA, Spearman correlation, and principal component analysis (PCA). The findings reveal significant temporal variations in water quality, with deterioration peaks linked to the rainy season, increased agricultural activity, and untreated wastewater discharges. The PCA identified three principal components explaining 46.56% of the total variance, highlighting the influence of biodegradable organic matter (BOD₅), oxidizable load (COD), oils and greases (FO), and coliforms as key pollution drivers. The WQI ranged from 0.46 to 0.65, reflecting moderate quality, while the ICOMO and ICOTRO indicated persistent eutrophic conditions and suspended solids contamination, particularly at P1. Although the ICOMI and ICOpH showed mostly low contamination levels, isolated peaks suggest the need for continuous surveillance. Despite its semiannual frequency and limited spatial coverage, the study provides a reliable long-term baseline for understanding water quality dynamics in port environments. It demonstrates the effectiveness of multivariate and index-based approaches in tropical regions, where integrated assessments remain scarce. The results underscore the importance of strengthening wastewater treatment, promoting sustainable agricultural practices, and expanding the environmental monitoring network. This research contributes to bridging knowledge gaps in the ecological management of fluvial-port ecosystems in Colombia. Future strategies should consider predictive modeling and community-based participation to ensure the conservation of the Magdalena River's ecological integrity and its critical role in biodiversity, livelihoods, and regional development.

Water pollution and environmental policy in artisanal gold mining frontiers: The case of La Toma, Colombia

Artisanal and small-scale gold mining (ASGM) is the largest anthropogenic source of mercury emissions globally. Concern over mercury pollution increases due to its long-term impacts on human health and aquatic and terrestrial ecosystems. Using a participatory research methodology, we gathered social and behavioral information regarding daily practices and water usage by an ASGM community in Suárez, Colombia. Based on this information, we identified 18 sampling sites of water sources commonly used by the community. The samples were analyzed for total mercury, total coliforms, pH, electrical conductivity, and total dissolved oxygen. Physicochemical and microbiological parameters from the water assessment were compared with the drinking water thresholds set by the Colombian regulatory agencies, the EPA, and the WHO. Our results showed that the majority of the samples do not meet one or more quality and safety standards. On average, the sampling sites showed total mercury levels below the regulatory limits; however, the data had considerable variability, and in many cases, individual observations fell above the maximum concentration limit for drinking water. We discuss these results within the larger framework of the regulatory gaps for human and environmental protection in ASGM contexts. The total lack of water, sanitation, and hygiene infrastructure, combined with the long-term consumption of sublethal doses of mercury and other water contaminants, constitutes a significant threat to the well-being of communities and territories that necessitates further research and intervention by institutional authorities.

Mercury Phytotoxicity and Tolerance in Three Wild Plants during Germination and Seedling Development

By examining plant responses to heavy metal stress during the early stages of the life cycle, we can predict their tolerance and survival in polluted areas as well as their potential for bioremediation. The objective of our study was to evaluate the effect of exposure to mercury (Hg) on the germination and in vitro development of three plant species: Bidens pilosa, Taraxacum officinale (Asteraceae), and Heliocarpus americanus (Malvaceae). These are wild ecotypes adapted to local edaphoclimatic conditions in southern Ecuador, an area which has been historically affected by artisanal and small-scale gold mining (SSGM). For comparison, we additionally used a known Hg-tolerant plant, Lactuca sativa (Asteraceae). We tested biorelevant concentrations of Hg, equivalent to those occurring in soils affected by SSGM, i.e., up to 4.0 mg/L of Hg. The relative inhibitory effects of the treatments (0.6, 2.0, and 4.0 mg/L of Hg) on the germination percentage were most evident in T. officinale, followed by B. pilosa, while L. sativa and H. americanus were not affected. In terms of the time needed to reach 50% germination (T50), B. pilosa exposed to higher concentrations of Hg showed an increase in T50, while H. americanus showed a significant reduction compared to the control treatment. The reduction in radicle length at 4.0 mg/L Hg compared to the control was more evident in L. sativa (86%) than in B. pilosa (55.3%) and H. americanus (31.5%). We concluded that, in a scenario of Hg contamination in the evaluated concentration range, the grass B. pilosa and the tree H. americanus could have a higher probability of establishment and survival.

Spatiotemporal Variability of Human Disturbance Impacts on Ecosystem Services in Mining Areas

Human activities pose significant impacts on ecosystem services (ESs) in mining areas, which will continually increase over time and space. However, the mechanism of ES change on spatiotemporal scales post-disturbance remains unclear, especially in the context of global climate change. Here, we conducted a global literature review on the impact of two of the most frequent disturbance factors (mining and restoration) on 27 different ESs, intending to synthesize the impacts of human disturbance on ESs in mining areas via a meta-analysis, and analyze the spatiotemporal variability of ESs after disturbance. We screened 3204 disturbance studies published on the Web of Science between 1950 and 2020 and reviewed 340 in detail. The results of independence test showed that human disturbance had a significant impact on ESs in the mining areas (p < 0.001). The impacts (positive and/or negative) caused by mining and restoration differed considerably among ESs (even on the same ESs). Additionally, spatiotemporal scales of human disturbance were significantly related to spatiotemporal scales of ES change (p < 0.001). We found that the positive and negative impacts of disturbances on ESs may be interconversion under specific spatiotemporal conditions. This seems to be associated with spatiotemporal variability, such as the temporal lag, spatial spillover, and cumulative spatiotemporal effects. Climate changes can lead to further spatiotemporal variability, which highlights the importance of understanding the changes in ESs post-disturbance on spatiotemporal scales. Our research presents recommendations for coping with the twofold pressure of climate change and spatiotemporal variability, to understand how ESs respond to human disturbance at spatiotemporal scales in the future, and manage disturbances to promote sustainable development in mining areas.

History, Current Situation and Challenges of Gold Mining in Ecuador’s Litoral Region

Gold mining in Ecuador has been present in the country since Inca times; over the years interest in the mineral has increased, leading to the creation of legislation to control the mining sector in a safe manner. The Litoral region consists of seven provinces, six of which have registered gold concessions; the most affected provinces are El Oro and Esmeraldas. The objective of this study was to analyze the historical and current situation of artisanal and industrial gold mining in the Litoral region of Ecuador. Different methodologies were used for the elaboration of this study, including bibliographic review, grey literature, field interviews and a validation of expert judgment. The main results indicate that El Oro and Esmeraldas are essentially the most conflictive areas in the region, as they have sometimes had to establish precautionary measures due to the risks caused by illegal mining. In addition, in both areas there is a great socioeconomic impact ranging from lack of opportunities, forgetfulness, migration, emigration, and violation of rights, among others. With respect to environmental impacts, the study highlights the contamination of water sources (which leads to a lack of drinking water for people), and damage to aquatic and terrestrial ecosystems. Finally, the study concludes that the authorities should control the mining sector more by implementing more laws and carrying out inspections to put an end to illegal gold mining, in order to improve the situation in the areas.

Water footprint in gold extraction: A case-study in Suárez, Cauca, Colombia

This research deepens the analysis of the mineral water footprint, especially that of gold, in regions that are understudied and where mining has been an intensified extractive activity since the colonial era, as is the case in the northern part of department of Cauca in Colombia. Thus, the purpose was to estimate the water footprint indicators in gold mining in Suárez (Cauca, Colombia), to quantify the impacts generated by the non-returned water in the production process and the levels of pollutants in the wastewater, aimed to strength public policies, control strategies and mitigation that generates reductions in the impacts from mining activities on the environment. The blue water footprint was estimated in 79.91 m³ per kg of gold extracted and the gray water footprint was found to be in the range of 272,125.39 to 404,825.11 m³ per kg of gold extracted. The water footprint values obtained were compared with other mines with similar operations. These results generate a baseline for decision making, providing elements for environmental strategic planning, regulations and showing the great environmental pressure that gold activity exerts on water resources and the territories.