Overview
ISO 5667-8:1993, "Water quality - Sampling - Part 8: Guidance on the sampling of wet deposition," provides practical guidance for designing sampling programmes and selecting instrumentation and techniques for wet deposition sampling (rain and snow). The standard focuses on the quality of wet precipitation for chemical analysis and interpretation, and explicitly does not cover measurement of rainfall quantity, dry deposition, or other wet forms such as mist, fog and cloudwaters. Primary objectives include the control of local emissions and the assessment of long-range transport of airborne pollutants.
Key topics and technical requirements
- Sampling programme design: Guidance on choosing representative sites and sampling strategies to detect temporal and spatial variations in precipitation chemistry.
- Sampling equipment, materials and siting: Recommendations on collectors and construction materials:
- Organic analyses: use stainless steel, glass or PTFE; avoid most plastics.
- Inorganic analyses: high-quality polyethylene, glass, PTFE or polypropylene containers are acceptable; borosilicate/quartz glass with PTFE‑lined caps recommended for some parameters.
- Contamination control and preservation:
- Procedures for cleaning funnels/bottles and use of bottle blanks.
- Acidification (e.g., nitric acid) to preserve trace metal samples and reduce adsorption.
- Avoid sample transfer where possible; use sealable liners and dust-free handling.
- Sampling techniques:
- Event sampling (collect each precipitation event) and wet‑only collectors for representative chemistry.
- Automatic wet‑only samplers with moisture sensors and heated grids to operate covers.
- Composite sampling options (automatic or manual compositing; daily emptying as an approximation).
- Special considerations for snow/snowfall sampling due to aerodynamic displacement.
- Field measurements and sub-sampling: Make field measurements on separate discardable sub-samples and label bottles with filtration/preservative status.
- Sample transport, storage and quality control: Rapid shipment, cool/dark storage, and laboratory coordination; guidance on sampling QA/QC and safety.
Practical applications
ISO 5667-8 is applied in:
- Environmental monitoring networks tracking acid deposition, nutrients, trace metals or organic contaminants in precipitation.
- Research studies on atmospheric transport and deposition of pollutants.
- Regulatory and compliance programmes assessing emissions impact on ecosystems.
- Laboratory managers developing sampling SOPs and chain-of-custody for precipitation chemistry.
Who should use it
- Environmental agencies, monitoring network operators and field technicians
- Atmospheric and water-quality researchers
- Analytical laboratories and QA/QC personnel
- Policy makers and consultants involved in emission control and ecosystem assessment
Related standards
- ISO 5667-1, -2, -3 (general sampling guidance, techniques, preservation and handling)
- Other parts of ISO 5667 (Parts 4–12) for different water media
- ISO 6107 (water sampling vocabulary)
