Soil aggregate structure, stability, and stoichiometric characteristics in a smelter-impacted soil under phytoremediation

Abstract

Smelter-impacted soils often result in soil degradation and the destruction of the soil structure. Although soil aggregate typically plays a crucial role in soil structure, the influence of phytoremediation on soil aggregate structure stability and stoichiometric characteristics remains unclear. To study the influence of phytoremediation on soil aggregate structure, stability and stoichiometric characteristics, a 3-year in situ experiment was conducted. After hydroxyapatite was applied, Elsholtzia splendens, Sedum plumbizincicola, and Pennisetum sp. were planted in a smelter-impacted soil. After 3 years, the soil aggregate structure, stability, and stoichiometric of chemical elements were analyzed. The results showed that the three phytoremediation treatments increased the content of >0.25 mm mechanically-stable (DR0.25) and water-stable (WR0.25) aggregates by 6.6%–10.4% and 13.3%–17.5%, respectively. Aggregate mean weight diameter (MWD), geometric mean diameter, and aggregate stability rate (AR, %) were significantly increased, and the soil mechanically stable aggregate fractal dimension (D) was significantly reduced after the 3-year remediation. Soil total nitrogen and phosphorus in aggregates with different particle sizes were significantly increased by 11.4%–46.4% and 107%–236% after different plant treatments. For the stoichiometric characteristics of the aggregates, the combined remediation only significantly reduced the value of N:P and C:P in different particle size aggregates and had no significant effect on the C:N in all particle size aggregates. Meanwhile, the combined remediation of hydroxyapatite and Elsholtzia splendens, Sedum plumbizincicola, and Pennisetum sp. in heavy metal heavily contaminated soil could reduce the availability of Cu and Cd by 54.1%–72.3% and 20.3%–47.2% during the 3 years, respectively. In summary, this combined remediation method can be used for the remediation of farmland that is contaminated by heavy metals.

Stoichiometric characteristics drive the soil aggregate stability rather than microbial community characteristics and soil nutrients after 5 years of vegetation restoration in China

“…2). The higher the content of soil water-stable macroaggregates, the more stable soil aggregates, and the better the structural stability of soil (Xu et al 2022c, Celik 2005. This indicates that AF planting in degraded land can improve soil aggregate structure and enhance aggregate stability within 0-30 cm.…”

“…For example, the increases in soil C:N, C:P, and N:P ratios were accompanied by the decreasing aggregate size in Chinese r plantations (Tang & Wang 2022). The vegetation restoration only signi cantly reduced the value of N:P and C:P in different particle size aggregates and had no signi cant effect on the C:N in all particle size aggregates (Xu et al 2022c). However, it is not known how the stability of soil aggregates is related to oil stoichiometric characteristics under different vegetation restorations.…”

“…This indicates that different restoration methods have different degrees of in uence on TC and TN content in different particle sizes and soil layers, which will signi cantly affect the C/N of different aggregates. Previous research has shown that the C/N ratio of soil aggregates was relatively stable in both Chinese r forest restoration (Tang & Wang 2022) and herbaceous plant restoration (Xu et al 2022c). Unlike our results, only in the size of 0.053-0.125mm, vegetation restoration signi cantly increased soil TC content, but there was no signi cant difference in TN content among different treatments, which resulted in a signi cant increase in C/N by vegetation restoration in 20-30cm soil layer (Fig.…”

“…Soil pH was detected through the glass electrode. Soil P content was measured by the approach of molybdenum blue colorimetric (Xu et al 2022c). Microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) were quanti ed by comparing sets of chloroformfumigated and non-fumigated soil samples (Xu et al 2022b).…”

“…4). However, vegetation restoration signi cantly reduced the value of N:P in different particle size aggregates in a typical acid rain area in south China (Xu et al 2022c). This is because the average P content in this area is about 0.19g/kg (the P content in our study site was about 0.6g/kg), and the soil aggregates were obviously limited by the P element.…”