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In a previous work (Storchi-Bergmann and Pastoriza 1989) we have studied in detail the spectra of one LINER and five "dwarf" Seyfert 2 galaxies showing nitrogen emission lines [N II] lambdalambda6548, 6584 very strong when compared with Halpha. The most accepted explanation for high [N II] / Halpha ratios was that they were due to the high excitation of the gas (Pagel 1983). Our work has shown that the gas abundance also plays a role in the enhancement of the [N II] / Halpha ratio; We could reproduce the highest ratios only with an overabundance of nitrogen in the nuclear gas relative to the other heavy elements when compared to the solar value. The abundance of nitrogen in LINERs (although not in Seyfert 2's) was previously discussed by Binette (1985), who has also found nitrogen over oxygen ratios higher than solar. In our work there is also an indication that the same is happening with sulfur.

In this work we search for the above effects in a larger sample, using emission-line data from the literature which were compared with shock and photoionization model values.