meth_2.20 Analytical Services Tasmania Laboratory Procedures Derwent Estuary Program, Ambient Water Quality Program

Contributor(s): Derwent Estuary Program

Citation: DEP (2020). State of the Derwent estuary — 2020 update. An update and review of environmental data and activities, U. Taylor, S. Whitehead, I. Visby, A. Weller-Wong and B. Proemse, Derwent Estuary Program (Hobart, Australia)

AM Project ID: AM0016

Water samples are collected from the surface (~0.5 m below the water surface) and bottom (~ 0.5 m above the benthos) for nutrient analysis. Nutrients are analysed at Analytical Services Tasmania (AST; https://analyticalservices.tas.gov.au/) by flow injection analysis. Depth integrated samples are collected using a Lund tube (Talling and Lund, 1957) for analysis of chlorophyll-a. AST operates under a Quality Management System in compliance with the requirements of international standard ISO/IEC 17025, accredited in Australia by NATA.

For consistency with the AM database, unit conversions are conducted for some parameters using the International Council for the Exploration of the Sea (ICES) conventions (https://www.ices.dk/data/tools/Pages/Unit-conversions.aspx; detailed in Table 2.20_1).

Table 2.20_1

Parameter

DEP AWQ units

AM units

Conversion formula

Dissolved Oxygen

mg/L

µmol/L

DEP AWQ value x 1000 /MW O2 31.998

Dissolved reactive Phosphorus as P

µg/L

µmol/L

DEP AWQ value / MW P 30.973762

Total Nitrogen

µg/L

µmol/L

DEP AWQ value / MW N 14.006720

Nitrate & nitrite as N

µg/L

µmol/L

DEP AWQ value / MW N 14.006720

Ammonia and ammonium as N

µg/L

µmol/L

DEP AWQ value / MW N 14.006720

* Molecular Weight of Nitrogen = 14.006720, Molecular Weight of Phosphorous = 30.973762, Molecular Weight of O2 = 31.998

Detailed methodologies, including QA/QC procedures are documented in the State of the Derwent Update 2020 Appendices A-C (DEP 2020; https://www.derwentestuary.org.au/state-of-the-derwent/). All original biochemical and physical water column data, included variables not recorded in the AM database (e.g. Hazen True Colour, metals) was sourced from the DEP (https://www.derwentestuary.org.au/contact/). Data can be requested directly through the same process.