Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Trace elements analysis of aerosol samples from some Romanian urban
  zones   Aerosols deposits on filters from ten Romanian towns with different kinds and
levels of industrial development have been studied. The concentration of
elements with Z~16 have been measured by particle - induced X-ray emission
(PIXE) analysis. It has been determined 15 elements: S, K, Ca, Ti, V, Cr, Mn,
Fe, Co, Ni, Cu, Zn, As, Hg and Pb.

16
The categories of this paper are: stat
37
The categories of this paper are: supr-con
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
35
The categories of this paper are: mtrl-th
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs
24
The categories of this paper are: dg-ga
21
The categories of this paper are: adap-org
23
The categories of this paper are: solv-int
28
The categories of this paper are: alg-geom
18
The categories of this paper are: econ