Table 1. The contents of some common elements (mg g⁻¹), and the pH and pH_PZC of biochars.

Biochar	K	Ca	Mg	Al	Fe	Zn	P	pH and pHPZC*
PN350	9.8 ± 0.6	15.7 ± 0.3	3.0 ± 0.2	1.4 ± 0.0	0.9 ± 0.0	0.076 ± 0.001	1.8 ± 0.0	7.9 ± 0.1
PN550	13.6 ± 0.0	23.7 ± 0.7	4.6 ± 0.2	2.1 ± 0.0	1.3 ± 0.0	0.106 ± 0.003	2.7 ± 0.0	9.6 ± 0.0
WS350	31.8 ± 0.4	9.7 ± 0.2	2.6 ± 0.0	1.8 ± 0.0	1.7 ± 0.0	0.061 ± 0.009	1.3 ± 0.0	8.2 ± 0.0
WS550	38.8 ± 0.6	12.3 ± 0.7	3.8 ± 0.1	2.3 ± 0.1	2.2 ± 0.0	0.060 ± 0.001	1.7 ± 0.0	9.7 ± 0.0
PN350D	0.29 ± 0.02	5.0 ± 0.5	1.8 ± 0.0	0.46 ± 0.00	0.25 ± 0.01	0.056 ± 0.002	0.12 ± 0.00	4.3 ± 0.1
PN550D	0.24 ± 0.01	4.7 ± 0.1	4.0 ± 0.1	0.91 ± 0.02	0.28 ± 0.00	0.083 ± 0.003	1.20 ± 0.02	5.4 ± 0.1
WS350D	0.02 ± 0.00	1.0 ± 0.1	0.7 ± 0.0	0.13 ± 0.05	0.21 ± 0.01	0.016 ± 0.003	0.05 ± 0.00	4.4 ± 0.0
WS550D	0.06 ± 0.00	3.3 ± 0.1	2.2 ± 0.0	0.12 ± 0.01	0.31 ± 0.01	0.029 ± 0.002	0.22 ± 0.00	5.5 ± 0.1

^*The dissolution of the ash in raw biochar could consume a large amount of H⁺, which makes the pH_PZC data of raw biochars unreliable, thus only the pH_PZC of de-ashed biochars has been tested.