MARIS Data Guide

A reference for data providers and data users

About MARIS

The IAEA Marine Radioactivity Information System (MARIS) provides open access to radioactivity measurements in marine environments worldwide. Developed and maintained by the IAEA Marine Environmental Laboratories in Monaco, MARIS integrates measurements from regional monitoring programmes, event-driven datasets, and historical scientific literature into a single, freely accessible database.

Sample types

All measurements are organized into four sample type groups:

Sample type What it covers Primary unit
SEAWATER Dissolved and filtered water samples (seawater and brackish water) Bq m⁻³
BIOTA Marine organisms — fish, shellfish, seaweed, and other biota Bq kg⁻¹ (wet or dry weight)
SEDIMENT Bottom sediments, including core profiles Bq kg⁻¹ or Bq m⁻²
SUSPENDED Suspended particulate matter in the water column Bq kg⁻¹

Measurement fields

Each record contains:

  • Location — latitude, longitude, station name, named area
  • Time — sampling date (encoded as seconds since 1970-01-01 UTC in NetCDF4)
  • Depth — sampling depth and total water column depth
  • Nuclide — identity via a MARIS standard ID linked to a lookup table
  • Activity — measured value or minimum detectable activity (MDA)
  • Uncertainty — 1σ absolute uncertainty in the same unit as the activity
  • Detection limit flag — = (measured), < (below detection limit), ND (not detected), or DE (derived/aggregated)
  • Unit — MARIS standard unit ID from a lookup table
  • Sample-type-specific fields: species and body part (BIOTA); sediment type and core interval (SEDIMENT); filter status (SEAWATER)
  • Method fields: sampling method, preparation method, counting method

→ See Field Definitions for the complete field reference.
→ See Sample ID Coverage for the status of SMP_ID / SMP_ID_PROVIDER capture across all handlers.

Nomenclature and lookup tables

Enumerated fields (nuclide identity, species, units, sediment type, body part, etc.) are stored as integer IDs referencing standardised lookup tables maintained by MARIS. This design ensures consistency across datasets from different providers.

Field Lookup table
Nuclide identity dbo_nuclide.xlsx
Unit dbo_unit.xlsx
Species dbo_species.xlsx
Biological group derived from dbo_species.xlsx
Body part dbo_bodypar.xlsx
Sediment type dbo_sedtype.xlsx
Detection limit dbo_detectlimit.xlsx
Laboratory dbo_lab.xlsx
Sampling method dbo_sampmet.xlsx
Preparation method dbo_prepmet.xlsx
Counting method dbo_counmet.xlsx
Named area dbo_area.xlsx

Data formats

MARIS data is available in two formats:

NetCDF4 (primary format)
Each file is self-contained: measurements, variable metadata, lookup tables for all used nomenclatures, and bibliographic information are bundled together. Data is organized into groups by sample type. The publisher_postprocess_logs global attribute records every curation step applied to the dataset, providing a permanent audit trail.

CSV (legacy format for database import)
Flat files with one file per sample type, compatible with the MARIS master database ingestion pipeline.

How data is curated

Data from providers arrives in many formats and uses provider-specific nomenclature. Before entering MARIS, each dataset is processed through the marisco curation pipeline:

  1. Nomenclature mapping — nuclide names, species names, body parts, and sediment types are mapped to MARIS standard IDs using fuzzy-matched lookup tables, with manual review of uncertain matches.
  2. Unit standardisation — seawater activities are converted to Bq m⁻³; biota activities carry a wet-weight or dry-weight flag; uncertainties are expressed as 1σ absolute values.
  3. Coordinate and date validation — coordinates are converted to decimal degrees; dates are parsed to a common datetime; invalid or missing values are dropped.
  4. Detection limit encoding — provider-specific flags are mapped to the four MARIS standard codes (=, <, ND, DE).
  5. Audit trail — every curation step is logged and stored in the NetCDF4 file’s publisher_postprocess_logs global attribute.

Available datasets

Dataset Provider Sample types Coverage
MARIS Legacy MARIS Master Database All types Global, historical
HELCOM HELCOM MORS SEAWATER, BIOTA, SEDIMENT Baltic Sea
OSPAR ODIMS OSPAR BIOTA NE Atlantic
TEPCO Fukushima monitoring (TEPCO / NRA) SEAWATER, BIOTA, SEDIMENT NW Pacific
GEOTRACES BODC GEOTRACES IDP2021 SEAWATER Global

Accessing MARIS data

  • Web interface — maris.iaea.org: browse, search, filter, and download datasets
  • marisco — this Python package generates MARIS-standard NetCDF4 files locally from the source datasets listed above; see the getting started guide for installation and usage