Pollution: Effects on Fungi in Terrestrial Environments

Categorization of Environmental Pollutants

• Chemical Pollutants: Includes inorganic substances (heavy metals like $iron$, $arsenic$, $lead$, $zinc$, and $sulphides$; $aluminium$ and $antimony$ oxides), gases ($SO_2$, $NO_x$, $O_3$), and organic compounds ($POPs$, $PCBs$, $dioxin$, $DDT$, $PAHs$).

• Environmental Persistent Pharmaceutical Pollutants (EPPP): Emerging chemical contaminants.

• Physical Pollutants: Consists of Particulate Matter ($PM$), large debris (plastics, junk), and energy-based pollution (heat, light, noise, radioactivity).

• Polluted Environments: Pollutants enter air, soil, and water, frequently moving between these environments.

Mechanisms of Fungal Intake and Retention

• Absorption: Hyphae acquire nutrient and non-nutrient elements directly from the environment.

• Lichen Thalli: Particles are acquired through wet and dry deposition.

• Entrapment: High element concentrations result from trapping particles in intercellular spaces, ranging from microscopic aerosols ($< 1\,\mu m$) to dust ($> 1\,mm$).

Impacts of Gaseous Pollutants and Acid Rain

• Pollutant Types: Primary pollutants (e.g., $SO_2$, $NO_2$, fluoride) remain in their emitted form; secondary pollutants (e.g., $O_3$, $HNO_3$, $H_2SO_4$) form in the atmosphere.

• Lichen Sensitivity Scale: Based on work by Hawksworth & Rose (1970), lichen communities indicate $SO_2$ levels across zones $0$ through $10$:   - Zone 0: Lichens absent due to high pollution.   - Intermediate Zones: Presence of tolerant species like Lecanora conizaeoides.   - Zone 10: Presence of sensitive species such as Usnea articulate and Usnea filipendula.

Nitrogen Deposition and Mycorrhizal Dynamics

• Nitrophobes: Species that decline with nitrogen enrichment, such as Cortinarius, Piloderma, Suillus, and Tricholoma.

• Nitrophiles: Species favored by nitrogen deposition, such as Paxillus involutus, Laccaria, Lactarius, and Thelephora.

• Ecological Shifts: Nitrogen pollution favors fungi with short-distance foraging patterns over those with dense, medium-distance proliferation.

Metal and Radionuclide Accumulation

• Radionuclides: Pollutants like $^{131}I$ (half-life $8.04\,d$), $^{137}Cs$ ($30\,y$), $^{90}Sr$ ($29.12\,y$), and $^{241}Pu$ ($14.4\,y$) accumulate in the food chain via Cladonia lichens, eaten by caribou/reindeer, and subsequently by Inuit and Smi populations.

• Accumulation Capacity: Species vary significantly in their uptake:   - Arsenic ($As$): Up to $100-200\,mg\,kg^{-1}$ in fruit bodies.   - Aluminium ($Al$): Armillaria spp. rhizomorphs can reach $3440\,mg\,kg^{-1}$.   - Zinc ($Zn$): Armillaria spp. rhizomorphs can reach $1930\,mg\,kg^{-1}$.   - Lead ($Pb$): Lichen monitoring (1907–1992) showed a peak in 1970 followed by a decline linked to unleaded petrol.

Fungi as Bioindicators and Agents of Bioremediation

• Indicator Types: Reaction indicators (species that disappear or increase based on sensitivity) and accumulation indicators (species whose tissues are analyzed for pollutants).

• Proposed Bioindicators:   - Mercury and Cadmium: Agaricus and Mycena pura.   - Radionuclides: Heboloma cylindrosporum for $uranium$ and $thorium$; Lycoperdon perlatum for $^{239}Pu$ and $^{241}Am$.

• Bioremediation: Uses fungi to remove toxic metals from soil, breakdown organic pollutants, and manage radioactive waste like depleted $uranium$.