Migration and Transformation of Heavy Metals in the Soil of the Water-Level Fluctuation Zone in the Three Gorges Reservoir under Simulated Nitrogen Deposition

Table 3

Fitting functions of cumulative release amounts and the release rates of HMs.

N deposition	Release process	Fitting equation	Correlation coefficient (r^2)	Release rate (g/d)
Cr
N0	First stage	y = 1.14x + 1.38	0.992	1.14
	Second stage	y = 0.65x + 7.03	0.996	0.65
N20	First stage	y = 1.14x + 0.84	0.995	1.14
	Second stage	y = 0.72x + 5.49	0.999	0.72
N40	First stage	y = 1.27x + 0.92	0.995	1.27
	Second stage	y = 0.71x + 7.50	0.996	0.71
N60	First stage	y = 1.48x + 1.34	0.991	1.48
	Second stage	y = 0.76x + 9.63	0.995	0.76
Cu
N0	First stage	y = 1.09x + 1.28	0.982	1.09
	Second stage	y = 0.78x + 2.86	0.997	0.78
	Third stage	y = 0.46x + 11.63	0.989	0.46
N20	First stage	y = 1.43x + 1.04	0.989	1.43
	Second stage	y = 0.78x + 5.70	0.998	0.78
	Third stage	y = 0.38x + 15.66	0.998	0.38
N40	First stage	y = 1.34x + 1.33	0.997	1.34
	Second stage	y = 0.70x + 6.39	0.997	0.70
	Third stage	y = 0.54x + 10.62	0.997	0.54
N60	First stage	y = 1.70x + 1.13	0.991	1.70
	Second stage	y = 0.82x + 6.57	0.995	0.82
	Third stage	y = 0.60x + 12.23	0.996	0.60
Cd
N0	First stage	y = 0.06x + 0.03	0.995	0.06
	Second stage	y = 0.03x + 0.51	0.927	0.03
	Third stage	y = 0.03x + 0.28	0.982	0.03
N20	First stage	y = 0.06x-0.005	0.991	0.06
	Second stage	y = 0.04x + 0.31	0.980	0.04
	Third stage	y = 0.02x + 0.88	0.933	0.02
N40	First stage	y = 0.07x + 0.02	0.991	0.07
	Second stage	y = 0.03x + 0.64	0.968	0.03
	Third stage	y = 0.02x + 0.76	0.961	0.02
N60	First stage	y = 0.07x + 0.005	0.998	0.07
	Second stage	y = 0.04x + 0.49	0.989	0.04
	Third stage	y = 0.03x + 0.81	0.973	0.03
Ni
N0	First stage	y = 0.33x + 0.12	0.997	0.33
	Second stage	y = 0.08x + 3.72	0.997	0.08
	Third stage	y = 0.09x + 3.55	0.975	0.09
N20	First stage	y = 0.36x + 0.22	0.993	0.36
	Second stage	y = 0.09x + 3.63	0.990	0.09
	Third stage	y = 0.15x + 1.94	0.986	0.15
N40	First stage	y = 0.33x + 0.47	0.995	0.33
	Second stage	y = 0.09x + 3.84	0.985	0.09
	Third stage	y = 0.19x + 0.70	0.982	0.19
N60	First stage	y = 0.36x + 0.33	0.998	0.36
	Second stage	y = 0.08x + 4.14	0.999	0.08
	Third stage	y = 0.12x + 2.94	0.965	0.12
Pb
N0	First stage	y = 0.06x + 0.01	0.850	0.06
	Second stage	y = 0.36x-4.53	0.984	0.36
	Third stage	y = 0.11x + 2.54	0.932	0.11
N20	First stage	y = 0.19x − 0.19	0.937	0.19
	Second stage	y = 0.62x − 6.97	0.985	0.62
	Third stage	y = 0.34x + 0.84	0.979	0.34
N40	First stage	y = 0.51x − 0.59	0.993	0.51
	Second stage	y = 0.92x − 6.62	0.979	0.92
	Third stage	y = 0.40x + 6.29	0.900	0.40
N60	First stage	y = 0.44x − 1.41	0.895	0.44
	Second stage	y = 1.07x − 10.21	0.996	1.07
	Third stage	y = 1.00x − 9.26	0.977	1.00