Interactive Data Explorer Gulf of Maine Nutrient Information System Welcome Page

Kennebec/Androscoggin Project Summary and Rationale

Rivers serve as the main link between land-based nutrients and those delivered to the ocean. The concentrations and proportions of nutrients borne by rivers not only affect freshwater lakes and waterways, but have a significant impact upon the coastal ocean as well. Human activities affect the chemical composition of rivers, and have been connected to eutrophication and other deleterious effects.

This project is focused on nutrient concentrations, fluxes, and ratios, and how these values change spatially along the course of a large watershed, as well as over time. Ultimately, we want to know how nutrients are delivered along a river system to the coastal zone. Most of this analysis can be done using nutrient ratios and mass flux calculations, that is to say, by understanding how the concentrations of the nutrients relative to each other change as they make their way down the watershed. In this data one can look for areas of removal or uptake, both in term of overall nutrient loss or addition, or loss or addition of selective nutrients.

The study area was the Androscoggin and Kennebec rivers in Maine (approximate combined watershed size: 8750 miles2). River samples are taken by bucket sampling off bridges. The plastic bucket, which is lowered by a rope from the bridge, is thoroughly rinsed with river water and emptied several times before the actual sample is collected and decanted into an acid-washed HDPE (high density polyethylene) 250 mL sample bottle. The samples are then preserved with approximately 2 mL of a sodium azide solution (0.077 M). The preservative is added to eliminate biological activity within the sample that could alter nutrient values. The samples are also filtered through 0.45 µm Millipore filters in order to remove suspended and particulate matter prior to laboratory analysis. A filtered volume of 50 mL of sample is then frozen until analysis.

Monthly sampling trips are conducted throughout the entire watersheds of the Androscoggin and Kennebec, sampling both the main stems and tributaries of each river. In all, approximately sixty-five water samples are collected on the monthly trips.

Nutrient analysis is carried out with a three-channel Lachat Quikchem 8000 Flow-Injection Analyzer using the methods designed by Lachat Instruments for water samples. The instrument analyzes for nitrate + nitrite (NO3 + NO2), nitrite (NO2), ammonium (NH4), phosphate (PO4) and silicate (SiO4). The term ‘three-channel’ simply means that the instrument can carry out three analyses at once; the Lachat that is used in this study generally performs the analysis of nitrate + nitrite, ammonia, and phosphate simultaneously, and the analysis of silicate and nitrite simultaneously. Flow-Injection Analysis (FIA) is the analytical technique performed by the instrument, essentially injecting the samples into a continually flowing carrier, which subsequently mixes with reagents and buffers before entering the detector (Ruzicka 1983). Sample analysis time is quite short for FIA methods, generally on the order of 60 seconds per sample, so this instrument allows for a high sample throughput in a single run. Additionally, FIA automates almost all mixing of reagents and buffers so little human error is introduced.