2.2 Soil physicochemical properties analysis
Total petroleum hydrocarbon (TPH) concentrations in soil were detected
using the Ultrasonic-Soxhlet gravimetric extraction method (Huesemann,
1995). Use a pH meter (PHS-3E; Shanghai) to measure soil pH at a
soil-water ratio of 2:5. Soil total carbon (TC), total nitrogen (TN),
and total sulfur (TS) were determined using an elemental analyzer
(Elementar Vario EL III, Germany). Soil total phosphorus (TP) was
digested with an
H2SO4-HClO4 solution at
250 ℃ and evaluated by the molybdenum-blue colorimetric method (Walker
and Adams, 1958). An electrical conductivity meter (DDSJ-318, Shanghai)
was used to explore soil electrical conductivity (EC).