Overview
ISO 20130:2018 - "Soil quality - Measurement of enzyme activity patterns in soil samples using colorimetric substrates in micro‑well plates" - specifies a laboratory method to measure multiple soil hydrolase activities using colorimetric substrates and 96‑well microplates. The standard describes simultaneous (or individual) assays for key extracellular enzymes that mediate carbon, nitrogen, phosphorus and sulfur cycling in soils, providing a reproducible approach for comparing enzyme activity patterns across samples, seasons and treatments.
Key topics and requirements
- Enzymes covered: arylamidase (ARN), arylsulfatase (ARS), β‑galactosidase (β‑GAL), α‑glucosidase (α‑GLU), β‑glucosidase (β‑GLU), N‑acetyl‑glucosaminidase (NAG), acid/alkaline/global phosphatases (PAC/PAK/PHOS), and urease (URE).
- Method principle: incubate soil suspensions with colorimetric substrates in micro‑well plates, stop reactions, centrifuge, transfer supernatants and read absorbance on a microplate UV/Vis spectrophotometer.
- Laboratory conditions: incubation at 25 °C ± 2 °C or 37 °C ± 2 °C; use of deionized water as medium to evaluate native soil enzyme activity at in‑situ pH.
- Reagents and buffers: Tris buffers at defined pH values (e.g., pH 5.5, 7.5, 11, 12) for specific enzymes, calcium chloride, stop/revealing reagents (e.g., salicylate, cyanurate), ethanol/acidified ethanol and colorimetric standards.
- Sample preparation and calibration: standardized soil:water suspension ratio (4 g soil : 25 ml water), establishment of calibration curves (p‑nitrophenol, β‑naphthylamine, ammonia standards), absorbance measurements and result calculations.
- Quality and validation: validity criteria, interlaboratory validation (ring test) and annexes providing validation data and intralaboratory tests.
Applications and who uses it
ISO 20130:2018 is designed for:
- Environmental and soil testing laboratories conducting soil enzyme assays and biological soil quality assessments.
- Ecotoxicologists and regulators assessing soil contamination effects or testing chemicals for adverse impacts on soil biochemical functioning.
- Researchers and agronomists monitoring soil health, nutrient cycling activity, seasonal dynamics of microbial function, and remediation progress.
Practical uses include screening contaminated soils versus controls, monitoring remediation or land‑use changes, and generating comparable enzyme activity datasets across studies.
Related standards
- ISO 18400‑206: Soil quality - Sampling - Part 206: Collection, handling and storage of soil under aerobic conditions for assessment of microbiological processes (normative reference cited in ISO 20130).
- ISO/TC 190: Technical Committee for Soil quality (developmental context).
Keywords: ISO 20130:2018, soil quality, soil enzyme activity, colorimetric substrates, micro‑well plates, hydrolase activities, soil testing, ecotoxicology, soil health.