Response of Nutrient Release of Periploca sepium Litter to Soil Petroleum Contamination

Abstract

The alteration of soil biological and chemical properties caused by petroleum contamination might result in limitations in the nutrient release from plant litter and thus threaten the stability of plant communities. In this study, the foliar litter of Periploca sepium was buried into lightly (petroleum concentration was 15 g kg−1), moderately (30 g kg−1), and seriously (45 g kg−1) contaminated soil for a 1 year decomposition experiment. The dynamics of nutrient release and the final nutrient release rates were determined, and the impacts of petroleum contamination on the release of C, N, P, K, Cu, Zn, Fe, Mn, Ca, and Mg from the litter were assessed. The results indicated that the release of all nutrients was significantly accelerated in the slightly and moderately contaminated soil. In contrast, the release of C, N, P, and K was significantly inhibited in the seriously contaminated soil, while only the Cu release from litter was significantly and simultaneously accelerated. Generally, serious soil petroleum contamination would significantly hinder the overall nutrient release from P. sepium litter; thus, P. sepium could only be utilized in the ecological restoration of contaminated soils with a petroleum concentration lower than 45 g kg−1.

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“…To determine the initial C concentration, crushed litter was digested using concentrated sulfuric acid and potassium dichromate solutions. Subsequently, the solution was titrated with a ferrous sulfate solution, and the litter C concentration was calculated based on the ferrous sulfate solution consumption, according to the method of Zhang et al [25]. For the determination of N and P, crushed litter was digested using concentrated sulfuric acid and hydrogen peroxide, and then the solution was diluted and determined using a continuous flow analytical system (AA3, Bran Luebbe, Germany) to obtain its N concentration [25].…”

“…Subsequently, the solution was titrated with a ferrous sulfate solution, and the litter C concentration was calculated based on the ferrous sulfate solution consumption, according to the method of Zhang et al [25]. For the determination of N and P, crushed litter was digested using concentrated sulfuric acid and hydrogen peroxide, and then the solution was diluted and determined using a continuous flow analytical system (AA3, Bran Luebbe, Germany) to obtain its N concentration [25]. Simultaneously, a NaOH solution was gradually added to the untreated diluted solution containing a dinitrophenol indicator until its color turned yellow.…”

“…Simultaneously, a NaOH solution was gradually added to the untreated diluted solution containing a dinitrophenol indicator until its color turned yellow. Subsequently, the color-changed solution was mixed with a vanadium ammonium molybdate solution and determined using an ultraviolet-visible spectrophotometer (UV-2450, Shimadzu Corporation, Kyoto, Japan) at 440 nm [25]. For the determination of lignin, crushed litter was first soaked with acetic acid and acetone, and centrifuged, and then the sediments were digested with sulfuric acid and potassium dichromate solutions, and titrated with a ferrous sulfate solution.…”

“…For the determination of lignin, crushed litter was first soaked with acetic acid and acetone, and centrifuged, and then the sediments were digested with sulfuric acid and potassium dichromate solutions, and titrated with a ferrous sulfate solution. Finally, the litter lignin concentration was calculated based on the ferrous sulfate solution consumption according to the method of Zhang et al [25]. Based on these methods, the initial substrate quality of each type of litter was calculated and is listed in Table 1.…”

“…The litters were transferred into a 0.15 mm sieve, rinsed quickly and then oven-dried at 60 • C to a constant weight. Subsequently, the N and P contents of the litters were determined according to the abovementioned methods of Zhang et al [25] using an AA3 continuous flow analyzer and an ultraviolet spectrophotometer, respectively. In addition, the soil in each pot was sampled three times after 1, 3, and 6 months of decomposition to determine the enzymatic activities, and the three soil samples sharing the same treatments were used as replicates.…”