2.3 Analysis Method
The current through soil was read by the connected ammeter (Pro’sKit,
Shanghai, China) each day.
Soil moisture was determined by weighing the wet soil and dry soil. When
the test stopped, about 50 g of soil were collected from the soil column
at different locations, weight the mass recorded as m1.
Afterwards, drying them in the oven (105 ℃, 101-2AB, Tianjin Tester
Instrument Co. Ltd, China), continuously weight the dry soil weight and
records it as m2 when the weight values stabilized. And
the soil moisture calculated by:
θ=(m1-m2)/m2 ×100%
where θ is the soil moisture (%), m1 is the mass of wet
soil (g), m2 is the mass of dry soil (g).
Sampled dry soil 5.00 g in 50 ml bottles with 25 ml deionized water
before shaken 30 min at 20±1℃ (200 r/min, QE-1, Tianjin Aunuo Instrument
& Meter Co. Ltd, China). Supernatant solution was collected after
centrifuged for 30 min (3000 r/min, TGL-16M, HuNan XiangYi Centrifuge
Instrument Co. Ltd, China). EC were detected using supernatant solution
by Conductivity meter (LAQUA EC-33, Horiba Corporation of Japan).
Remaining supernatant solution filtered through 0.45 μm membrane before
cations (Na+, K+,
Ca2+, Mg2+) and anions
(Cl-, NO3-,
SO42-) detections using ion
chromatography (YC3000, Qingdao Ailun General Technology Co., Ltd,
China). The volume of injection was 10μl, and the method detection limit
were as follows: Na+: 0.011 mg/L,
K+: 0.011 mg/L, Ca2+: 0.022 mg/L,
Mg2+: 0.011 mg/L; Cl-: 0.007 mg/L,
NO3-: 0.0167 mg/L,
SO42-:0.0187 mg/L. Similar as the
above preparation of supernatant except the ratio of soil and water was
1:2.5. Then the value of pH was detected by pH meter (LAQUA pH-22,
Horiba Corporation of Japan).
Results and discussions