---
watermark: ORIRO
disable-model-invocation: true
name: sci-environmental-science
provider: ORIRO.ai
copyright: Copyright (c) 2026 ORIRO.ai
description: >
  Environmental science — ecosystems, pollution, environmental impact assessment,
  soil and water science, toxicology, and environmental monitoring. Activate for
  questions about environmental issues, pollution, ecosystem science, or environmental
  assessment. Sources: EPA, USGS, NOAA, environmental science fundamentals.
---

# Environmental Science

## Ecosystems

**Ecosystem:** Community of living organisms + their physical environment, interacting as a system.
**Biotic:** Living components — producers (plants), consumers (animals), decomposers (fungi, bacteria).
**Abiotic:** Non-living — sunlight, water, temperature, pH, soil.

**Energy flow:** Unidirectional through food webs. Only ~10% transferred between trophic levels.
Producers → Primary consumers → Secondary consumers → Tertiary consumers
Detritivores and decomposers recycle nutrients.

**Biogeochemical cycles:** Carbon, nitrogen, phosphorus, water cycle continuously between living and non-living. Human disruption: excess CO2 (carbon cycle), excess nitrogen (fertilizers → eutrophication).

## Eutrophication

Nutrient overload (nitrogen, phosphorus) in water bodies from agricultural runoff, sewage.
Algae bloom → algae die → decomposers consume oxygen → hypoxic "dead zone" → fish kills.
Gulf of Mexico dead zone: ~8,000 sq miles. Caused by Mississippi River agricultural runoff.

## Pollution types

### Air pollution

**Criteria pollutants (EPA):** PM2.5, PM10, ground-level ozone, NO2, SO2, CO, lead.
**Primary pollutants:** Emitted directly (SOx from coal, NOx from vehicles, CO from incomplete combustion).
**Secondary pollutants:** Formed in atmosphere (ozone forms from NOx + VOCs + sunlight).
**Indoor air:** Often more polluted than outdoor. Radon (lung cancer risk), VOCs, particulates, CO.

### Water pollution

**Point source:** Single identifiable location (factory discharge, sewage outfall). Regulated under Clean Water Act permits.
**Nonpoint source:** Diffuse runoff (agriculture, urban stormwater). Harder to regulate. Major contributor to impaired waters.

### Soil contamination

**Brownfields:** Previously developed land with potential contamination. Cleanup before reuse.
**Common contaminants:** Heavy metals (lead, arsenic, cadmium), petroleum hydrocarbons, chlorinated solvents, pesticides.
**Phytoremediation:** Plants extract contaminants (hyperaccumulators). Slow but low cost.

## Environmental impact assessment (EIA)

Required for major projects affecting the environment.
**NEPA (US):** Environmental Impact Statement (EIS) for major federal actions. Environmental Assessment (EA) for smaller actions.
**Components:** Purpose and need → Alternatives analysis → Environmental baseline → Predicted impacts → Mitigation measures → Monitoring.
**Public comment:** Required periods. Significant input from public and agencies.

## Environmental toxicology basics

**Dose-response:** "The dose makes the poison" (Paracelsus). All substances can be toxic at sufficient dose.
**LD50:** Lethal dose for 50% of test population. Relative toxicity comparison.
**Bioaccumulation:** Substances accumulate in organisms.
**Biomagnification:** Concentration increases up the food chain. Mercury, DDT, PCBs.
**Endocrine disruptors:** Chemicals interfering with hormone systems. Bisphenol A, phthalates, some pesticides.

Sources: EPA (epa.gov — free), USGS (usgs.gov — free), NOAA (noaa.gov — free), Understanding Environmental Science (OpenStax principles)