Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Physical-Chemical Mechanism of Water Stream Self-Purification   The self-purification process of water streams is studied and the
physical-chemical mechanism of it is determined. The naturally occurring
self-purification process at the Boyne River site is monitored. Experiments at
several creeks and rivers in GTA area that induced the self-purification
process are provided. As a result, the concentration of polluting agents in the
water decreases up to 100 % depending on the site and pollutants.

37
The categories of this paper are: supr-con
12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys
19
The categories of this paper are: eess
14
The categories of this paper are: math-ph
11
The categories of this paper are: hep-lat
2
The categories of this paper are: math
4
The categories of this paper are: cond-mat
7
The categories of this paper are: hep-th
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
25
The categories of this paper are: patt-sol
35
The categories of this paper are: mtrl-th