Load WQX dictionary lookup table

Returns a combined tibble of canonical WQX Characteristic Names and alias mappings (synonym, standardize, retired). Uses the generic cache-or-fetch infrastructure - builds the dictionary from EPA data on first call if no cached RDS exists.

Usage

load_wqx_dictionary(cache_dir)

Arguments

cache_dir

Directory containing reference cache RDS files

Value

Tibble with columns: name, canonical_name, type, cas_number, group_name, description