To be of concern or To be a concern?

English as a Second Language English Vocabulary, Grammar and Idioms
1

Hi everyone,

I have a little confussing on the use of to be of concern and to be a concern. Which one is correct? if both are correct, what differences are they?

First, I have 2 sentenses that need to be corrected.

  1. The heavy use of antibiotics in aquaculture has been of a great concern.
  2. The heavy use of antibiotics in aquaculture has been a great concern.

I also have another sentence that my friend, non-native English speaker, said it is strange. I wonder if you could understand the below sentence, what doea it mean when you read it?

Antibiotic concentrations detected did not vary significantly at the two time point. This suggested that chronic consumption of these antibiotics stabilized their contamination in aquatic environments of the studied area.
In this sentence, he said the word: CHRONIC should not be used, and stablized should not be used. If so, if the sentence need to be rewriten, which words, and verbs should be used in this case, that keep the same meaning of its origin?

I would be happy if you correct these sentences for me as soon as helpful for me.

Thanks very much!
HoaLan

2

Hi,
I am waiting for the answer almost 1 week. I see 40 people viewed my question.
Is there anyone can help?
If the thing I want to learn, I can not. I wonder if I should come back the forum or not. :frowning: