Table 4. Summary of chromium emission to atmosphere and water in different periods (t).

Category	Sources	1990–1994	1995–1999	2000–2004	2005–2009	sum
To air	Coal combustion	1.50×104	1.71×104	1.83×104	3.90×104	8.93×104
	Waste incineration	0.00	0.00	9.01	7.65×101	8.55×101
	Cement production	1.56×103	2.59×103	3.78×103	6.70×103	1.46×104
	Ferrochromium production	1.40×102	1.40×102	4.18×102	1.11×103	1.81×103
	Oil combustion	7.24×103	9.45×103	1.42×104	2.76×104	5.85×104
	Iron and steel production	2.50×103	3.50×103	6.25×103	1.52×104	2.75×104
	Total per year	5.28×103	6.55×103	8.59×103	1.80×104	3.84×104
To water	Nonferrous smelting and Pressing	0.52	0.68	1.20	5.25	7.65
	Fabricated metal industry	8.79×102	1.22×103	1.74×103	5.25×103	9.10×103
	Leather industry	2.68×102	5.54×102	7.90×102	1.07×103	2.68×103
	Chemical manufacturing industry	9.00	1.30×101	2.02×101	5.70×101	9.92×101
	Nonferrous Mining and Dressing	1.04×102	1.48×102	2.03×102	5.65×102	1.02×103
	Other industries	4.83×101	5.99×101	1.01×102	2.73×102	4.82×102
	Total per year	2.62×102	4.00×102	5.72×102	1.44×103	2.68×103