ABSTRACT

The Lower Mystic Lake in Arlington-Medford, Mass, is a meromictic lake. The lake was determined to be a chemically stratified lake. The Metropolitan District Commission is presently considering whether mechanical destratification to remove the hydrogen sulfide from the noxious bottom layer of water is warranted. Specific gravity was measured to determine the density characteristics of the brackish water trapped in the monimolimnion. No dissolved oxygen occurred in the lower mixolimnia of the Lower Mystic Lake and none in the monimolimnion of each hole. The distribution of total sulfide in the monimolimnion is partially due to the internal circulation of this lower zone. According to G. C. Anderson little vertical variation of the pH concentration is indicative of the highly buffering nature of the monimolimnion. Biological oxygen demand, chemical oxygen demand, organic nitrogen, orthophosphate, and total phosphorus concentrations indicate the poor quality of the lake, especially the monimolimnion.