Sensitivity of the dark lemna to the presence of phenols and light hydrocarbons

Abstract

The objective of this study was to relate the oil spills with the overflow of Lemna obscura in the Lake. Six trials were conducted, for ten days; each, using glass containers of 25cm x 15cm x 15cm, with water from Lake Maracaibo with 50 Lemna plants of two fronds each and photoperiod 12:12 hours, to grow Lemna obscura in 5 concentrations of phenol (0.25) to 2.5mg / l) and 5 of light hydrocarbon (30 to 45mg / l). During each test the parameters were measured daily: pH, conductivity, dissolved oxygen, COD, turbidity. On days 1,5 and 10, phosphorus, total nitrogen, hydrocarbons and phenols were measured. The growth pattern was exponential. The highest growth rate (0.2041 fronds / d-1) and the lowest doubling time (3.4 days) were obtained in the phenol trials, the lowest rate (0.1151 fronds / d-1) and the longest time (6 days) in the trials with light hydrocarbon. The highest consumption of phosphorus (72%) and NTK (85%) and removal of organic matter COD (20%) was obtained with phenol.The plant absorbed more light hydrocarbons and as its concentration increased, the inhibition of plant growth was greater than with phenol. With this study it can be inferred that the oil spills that occurred in Lake Maracaibo are not activating factor to stimulate the growth of Lema obscura.