Rare Elements in the Shadow of Mining
The Environmental Story Around Miduk Copper Mine
How nature interacts with rare elements released by mining activities in Kerman province, Iran
In the heart of Kerman province, the Miduk Copper Mine not only holds a treasure of mineral resources but also serves as a unique natural laboratory for understanding how nature interacts with rare elements. While mining activities are vital for the economy, they can impact surrounding ecosystems by releasing elements such as copper, lead, and arsenic. Research conducted around this mine, including a study published in 2014, has opened a window into this complex dynamic. This article takes you on a scientific journey to see how the soil and plants in this region respond to rare elements and what consequences this interaction has for the environment.
Understanding the Puzzle: Rare Elements and Bioavailability
What Are Rare Elements?
Rare elements are substances that naturally occur in the Earth's crust but in very low concentrations. However, these minute quantities are absolutely essential for the survival of many living organisms, including plants. Copper, zinc, molybdenum, and manganese are among these elements. But these elements have another side: when their concentration exceeds a certain threshold, they become toxic agents that can be dangerous both for plants and for animals that feed on these plants.
The Key Concept: Bioavailability
The mere presence of an element in the soil does not mean it is available to living organisms. This is where the concept of "bioavailability" comes into play. Bioavailability refers to the extent to which an element can be absorbed and used by plants and other organisms. Factors such as soil acidity, organic matter content, and mineral composition all determine how readily a particular element is available to plant roots and can enter the food chain.
Key Insight
The toxicity of an element depends not just on its total concentration in soil, but on its bioavailability - the fraction that can actually be absorbed by living organisms.
Scientific Exploration: Field Testing Around Miduk Mine
Methodology: From Sampling to Analysis
A research team designed and conducted an extensive field study in the area of the Miduk copper mine to investigate this phenomenon in detail 1 3 .
Soil Sampling
64 soil samples from two depths (0-5cm as surface soil and 15-20cm as deep soil)
Plant Sampling
90 samples of roots and aerial parts from three native plant species
Laboratory Analysis
Analysis of 45 different elements and calculation of "transfer factor"
Key Findings: From Soil to Plant
The results of this research provided valuable insights:
Soil Contamination
Concentrations of elements such as arsenic, copper and lead in soil and plants, especially near the old mining sites of "Latela" and "Chah Masi", were well above the standard limit, indicating significant environmental hazards in the area 1 .
Surface Concentration
Concentrations of elements Ag, Cr, Cu, Fe, Mo, Se and Pb in surface soil samples were significantly higher than in deep soils. This pattern indicates that mining activities and wind erosion of minerals containing these elements play a major role in surface pollution 1 .
Transfer to Plants
Different plants showed different behaviors toward elements. However, in general:
This means plants easily absorb these elements from soil and transfer them to their aerial parts.
This indicates these elements have less mobility in the soil-plant system 1 .
What the Data Says
Table 1: Summary of Element Behavior in Environments Around Miduk Mine
| Element | Status in Surrounding Waters (μg/L) | Status in Soil-Plant System (Transfer Factor) 1 | Interpretation and Environmental Impact |
|---|---|---|---|
| Copper (Cu) | 17.22 (below standard limit) | High | Although concentration in water is low, high transferability to plants increases the risk of entry into the food chain. |
| Lead (Pb) | 15.06 (above standard limit) | Low | Severe lead contamination in water is a serious concern. Although transfer to plants is low, its presence in soil and water is dangerous. |
| Cadmium (Cd) | 0.64 (below standard limit) | High | Despite low concentration in water, the very high transfer factor makes this element biologically very dangerous. |
| Molybdenum (Mo) | - | High | High absorption and transfer capacity by plants makes continuous monitoring of this element essential. |
Table 2: Comparison of Element Concentrations at Different Soil Depths 1
| Element | Surface Soil (0-5 cm) | Deep Soil (15-20 cm) | Conclusion |
|---|---|---|---|
| Copper (Cu) | Higher | Lower | Surface mining activities are the main cause of increased concentration in surface layers. |
| Lead (Pb) | Higher | Lower | Has anthropogenic origin (mining and erosion) and accumulates in surface layers. |
| Iron (Fe) | Higher | Lower | Although an essential element, its abnormal accumulation can be toxic to plants. |
| Molybdenum (Mo) | Higher | Lower | Accumulation in surface soil makes it more available to plants cultivated on the surface. |
Table 3: Health Risk Assessment for Local Population (Water Sources)
| Parameter | Estimated Value | Acceptable Level | Interpretation |
|---|---|---|---|
| Carcinogenic Disease Risk | 1.59 × 10-5 | - | This number indicates that in the studied population, the probability of cancer occurrence due to these pollutants is within a significant range. |
| Non-carcinogenic Disease Risk | 6.43 × 10-8 | Usually less than 1 | Although this number seems small, the existence of any additional risk requires attention and management. |
Element Transfer Factors Visualization
About Transfer Factors
The transfer factor indicates how easily an element moves from soil to plant aerial parts. Higher values mean greater mobility and potential entry into the food chain.
Researcher's Toolbox
To conduct such complex studies, scientists use standard tools and methods:
Atomic Absorption Spectrophotometer (AAS)
This device is used for accurate measurement of metal concentrations in water samples and soil extracts . Its working principle is based on measuring the amount of light absorbed by vaporized atoms of a specific element.
Sequential Extraction Method
A powerful analytical method that determines not only total concentration but also different chemical forms of an element in soil. This is crucial for more accurate estimation of "bioavailability" since some chemical forms are more accessible to living organisms 1 .
Indicator Plants (Bioindicators)
Using native plants such as "Astragalus" and "Artemisia" as biological tools for pollution monitoring. These plants grow naturally in the region and by accumulating elements in their tissues, provide information about the level of available and absorbable pollution over time 1 .
Statistical Software & Environmental Quality Indices
Statistical software is used to analyze complex data and identify patterns. Also, indices such as "transfer factor" and "health risk assessment" are calculated to quantify hazards and translate scientific results into language understandable to decision-makers 1 .
Indicator Plants Used in the Study
Astragalus
A genus of flowering plants in the legume family, used as bioindicators for various elements.
Artemisia
A large genus of plants with between 200-400 species, known for accumulating various minerals.
Acanthophyllum
A genus of flowering plants in the carnation family, studied for their metal accumulation capabilities.
Conclusion: Nature's Warning and the Way Forward
The study around the Miduk copper mine clearly shows how industrial activities can disrupt the natural balance of elements in the environment. Although nature tries to moderate these effects with its own mechanisms, such as fixing elements in deep soil or using specific plants for selective absorption, the very high concentrations of elements such as lead and arsenic in some areas are a serious warning for the ecosystem and the health of local residents.
The findings of this research can provide a roadmap for future actions: from continuous monitoring of the environment and using phytoremediating plants to reduce soil pollution, to implementing sustainable management of mining waste. This research is not just a scientific report, but a story of the complex interaction between humans, industry, and nature that is narrated in the soil and plants of the Miduk region.
Key Environmental Concerns
- Elevated levels of arsenic, copper, and lead in soil near historical mining sites
- High transfer factors for cadmium, molybdenum, and copper increasing food chain risks
- Surface accumulation of elements indicating ongoing contamination from mining activities
- Measurable health risks to local population from water contamination