ISO 21479:2019

Overview - ISO 21479:2019 (Soil quality, leaf fatty acid composition)

ISO 21479:2019 specifies a laboratory and field‑sampling method to compare soil quality by measuring the leaf fatty acid composition of angiosperm plants grown in soils of interest. The method focuses on the Omega‑3 index (% C18:3 / (% C18:0 + % C18:1 + % C18:2)) calculated from fatty acid methyl esters (FAMEs) and is intended as an early bio‑indicator of pollutant effects on soil flora. It is applicable to contaminated, amended or remediated soils and soils receiving organic wastes (slurry, manure, sludge, composts). The standard is comparative - it does not define an absolute or “optimal” Omega‑3 index for a single homogeneous area.

Key technical topics and requirements

• Principle: transesterification of foliar lipids → formation of FAMEs → analysis by gas chromatography (GC) to obtain fatty acid profiles and calculate the Omega‑3 index.
• Target analytes: primary FAMEs used to compute the index (C18:3, C18:2, C18:1, C18:0) and other common leaf fatty acids.
• Sampling strategy: sample representative angiosperm species across comparable climatic areas; 4–8 individuals per species per area; small foliar sample mass (20–50 mg fresh tissue).
• Apparatus & reagents: standard lab equipment plus GC with FID, heating block (80 °C), centrifuge (200–300 g), methanol, sulfuric acid (transesterification), hexane (extraction), distilled water.
• Quality control: contamination control, sample storage (e.g., methanol preservation), ring‑test reproducibility (results reported in Annex A).
• Limitations & complementary methods: not suited to define intrinsic soil quality alone; Annex B offers an alternative ex situ method using Lactuca sativa seedlings grown in controlled conditions for comparative Omega‑3 indexing.
• Reporting: include site description, sampling details, fatty acid composition data and comparative conclusions.

Practical applications and who uses it

ISO 21479 is used to detect early phytotoxic effects of metallic and organic soil contaminants and to:

• Compare soil quality between sites (contaminated vs control)
• Monitor remediation effectiveness and amended soil impacts
• Assess effects of waste additions (manure, compost, sludge) Primary users:
• Environmental testing laboratories and analytical chemists
• Soil scientists and ecotoxicologists
• Contaminated‑land consultants and remediation contractors
• Regulatory agencies and environmental monitoring programs

Related standards and context

• Developed by ISO/TC 190 (Soil quality), Subcommittee SC 4 (Biological characterization).
• Complements other ISO soil quality standards on plant bioassays, emergence/growth inhibition and genotoxicity; useful as an early, sensitive bioindicator within integrated soil quality assessment programs.

Keywords: ISO 21479:2019, soil quality, Omega‑3 index, leaf fatty acid composition, FAMEs, gas chromatography, plant bioindicator, contaminated sites, remediation.