Inorganic Nutrients

Information associated with inorganic nutrient research

PIE LTER nutrient samples collected by Sigma Autosampler between 2001 and 2019 in three headwater sites of contrasting land use, and at the Parker and Ipswich River Dams as they enter into the Plum Island Sound estuary, Massachusetts.


Total organic nitrogen, total organic phosphorus, and nitrate concentrations collected frequently by Sigma autosampler (or volunteers in winter) from 5 sites. Sites include three headwater sites of contrasting land use (CC= Forest, SB = suburban, CS = wetland) and at the mouth of the Ipswich and Parker Rivers where they flow into the estuary.

Core Areas: 

Data set ID: 



Short name: 




Data sources: 



Samples were collected with a Sigma auto-sampler on a daily, bi-daily, flow-weighted, or time weighted frequency from each site.Samples were preserved with sulfuric acid, except for those collected by volunteer in winter which were not acidified but frozen within 24 hours. Analysed for nitrate, TP, TN, and TOC.

Sigma installation:  Sigma autosampler is placed at a convenient location on the bank of each site.  Sigma is visited every three weeks to replace/check bottles and batteries.  Intake is fastened to reebar suspended above the sediments to prevent intake of particulates from the stream bottom.  The bottles contain sulfuric acid to preserve nutrients in their ambient form. Bottles sit out for up to 6 weeks (but most often < 3 weeks) within the sampler before being filled and collected.   Occasionally spiders or other bugs are found in the samples. See notes.

Daily samples:  Sigma pulls a 1L sample the same time each day (usually between 9am to 5pm).

TwoDayComposite samples: Sigma pulls a 500ml sample and places it in the same bottle over two consecutive days. (usually grabbed between 9am and 5pm)

Volunteer:  A grab sample collected by a volunteer during winter period when sigma is not funcitonal.

Composite-timeweighted_*hrs - The Sigma pulls a sample every * hours and places it into a single carboy.  Usually the volume of the pull is 250ml.  The number of hours varied when we first switched to this technique, but is now every 6hrs (4 time per day).

Composite-flowweighted_*cms - The Sigma pulls a sample every * cubic meters per second pumped into a single carboy.  The amount of cubic meters varies depending on the time of year.  This technique relies on a depth sonde attached to the Sigma with associated rating curve.  No longer used due to unreliablity of the depth sonde.

Samples were processed at the Ecosystems Center in Woods Hole, MA. The processing procedure includes neutralization with sodium hydroxide and sodium bicarbonate, persulfate digestion, and nitrate and phosphate analysis using a Lachat auto-analyzer or spectrophotometer. 

As of 2004 TN and TOC are run together on a Shimadzu TN/TOC analyzer.  Prior to 2004, TN was first digested and then run on a Lachat.  TP is still digested and run on a spec.  Where samples exist in archive TOC will be run to complement TNs.

NOTES AND COMMENTS: Some of the samples from this data set have yet to be run and/or need to be re-run. This file will be updated as samples are analyzed.  Specifically, TN and TOC data back to 2004 is still being run to fill in holes.


Permanent_ID           Site X                             Site Y                          Description                                 Site ID in SigmaNutrients

YSI-SB                    225840                          919310               Suburban Headwater Stream                                   SB

YSI-CC                    247680                          946790                Forested Headwater Stream                                   CC

YSI-CS                                                                                   Wetland Headwater Stream                                    CS

IP24                        254280                          936350                Mouth of the Ipswich (Sylvania Dam)                        ID

10                           246600                          944510                 Mouth of the Parker (Central St.)                            PD


For 2014, no samples were collected at SB prior to 10/13 due to the sampler requiring service


Updated regularly to add dates or to enter data as analysis occurs.

Version 01, Sept, 2007. Updated to incorporate most recent data.
Version 02, 20 January 2010. Updated to include most recent data.
Version 03, February 20, 2011 updated data and metadata, variable names match
Version 04, 06Apr2012, data and metadata update. Used MarcrosExportEML_HTML (working)pie_excel2007.xlsm 3/23/2012 12:08 PM for QA/QC to EML 2.1.0
Version 05, 14May2013, metadata and data updated to comply with importation to Drupal and LTER PASTA. Used MarcrosExportEML_HTML (working)pie_excel2007.xlsm 3/14/13 12:02 PM for QA/QC to EML 2.1.0
Version 06: February 19, 2016, data and metadata updates to comply with importation to Drupal and LTER PASTA. Used MarcrosExportEML_HTML (working)pie_excel2007_Jan2015.xlsm 1/15/15 4:26 PM for QA/QC to EML 2.1.0
Version 07: September 6, 2019, data and metadata updates to comply with importation to DEIMS7 and LTER Data Portal. Used MarcrosExportEML_HTML (working)pie_excel2007_Sep2019.xlsm 9/3/19 5:19 PM for QA/QC to EML 2.1.0
Version 08: July 27, 2021, data and metadata updates to resolve errors in previous version as well as include most recent data and to comply with importation to DEIMS7 and LTER Data Portal. Used MarcrosExportEML_HTML (working)pie_excel2007_Jul2021.xlsm 7/26/2021 9:04 AM for QA/QC to EML 2.1.0.


Quality Assurance: 

All of our analyses go through an initial QA/QC at the time of analysis.  This includes replicates, standard curves and percent digestion (TP) and nitrate-nitrite conversion (NO3), as well as regular standard checks.  Despite this QA/QC there are several cases in which other questions might arise, including a small number of samples for which reported NO3 values exceed TN values. See notes for additional issues regarding data quality.


Subscribe to RSS - Inorganic Nutrients