Research and control of well water pollution in high esophageal cancer areas

Table 1 Three nitrogenous compounds pollution (mg/L) of the well water in Cixian County and Chichen County from 1993 to 1996

	Numbers of well	1993	1994	1995	1996
Nitrate nitrogen
Cixian	33	8.770b	13.381b	14.473b	19.554b
Chichen	31	3.829	4.452	4.351	8.022
Ratio		2.29	3.00	3.33	2.44
(Cixian/Chichen)
Nitrite nitrogen
Cixian	33	0.0144b	0.0629b	0.0407b	0.0101b
Chichen	31	0.0039	0.0094	0.0085	0.0020
Ratio		3.69	6.69	4.79	5.05
(Cixian/Chichen)
Ammonia nitrogen
Cixian	33	0.0094 b	0.0256b	0.0237	0.0117b
Chichen	31	0.0039	0.0029	0.0230	0.0028
Ratio		2.41	8.82	1.03	4.18
(Cixian/Chichen)

^bP < 0.01, There was a significant difference between two counties.

Table 2 Farming use of nitrogen fertilizer (kg/hectare) in Cixian County and Chichen County from 1991 to 1996

	1991	1992	1993	1994	1995	1996
Cixian	787.6	825.1	1293.1	1213.6	1251.1	1053.1
Chichen	186.0b	202.5b	196.5b	201.0b	220.5b	219.0b
Ratio (Cixian/Chichen)	4.20	4.07	6.58	6.04	5.67	4.81

^bP < 0.01, There was a significant difference between two counties.

Table 3 Three nitrogenous compounds (mg/L) in well water before and after well reconstruction

No. of well	Nitrate nitrogen		Nitrite nitrogen		Ammonia nitrogen
	Before	After	Before	After	Before	After
12#	14.9621	8.0097	0.0077	0.0033	0.0131	0.0048
14#	8.9890	1.9099	0.0208	0.0067	0.0127	0.0053
29#	18.4929	0.0000	0.2929	0.0100	0.0459	0.0087

12#, 14#, 29# are the number of the sampled well.