Distribution and Contamination Assessment of Soil Heavy Metals in the Jiulongjiang River Catchment, Southeast China

Abstract

A total of 63 soil samples were collected from three soil profiles (yellow soil, red loam, red soil) from Jiulongjiang river catchment to investigate the distribution, controlling factors, and toxic risks of heavy metals, including Cr, Mn, Fe, Cu, Zn, Cd, Pb, and Ni. The results showed that Cr and Cd in soils were enriched. The relationships between heavy metals and soil properties were assessed by principal component analysis. The results indicated that soil organic matter (SOM) played a fundamental role in controlling Cd and Pb in yellow soil and red loam sites. The Cd was significantly correlated with Pb and Cu, and Cr, Zn, Ni, Fe displayed strong correlations with each other, however, no statistical correlation was found between Cd and Cr. The enrichment factor and geoaccumulation index analyses showed that the soils in the study area were contaminated by Cd. Potential ecological risk analyses indicated that Cd posed a considerable ecological risk in yellow soils, and posed a moderate ecological risk in red loams and red soils.

Effects of Soil Properties on K Factor in the Granite and Limestone Regions of China

“…The SOC contents in the soils of the JRC were significantly lower than those in the soils of the CC (1-4 g kg −1 vs. 6-44 g kg −1 , Figure 2e), as well as the SON contents (0.1-0.5 g kg −1 vs. 1-4 g kg −1 , Figure 2f). The SOC and SON contents in the JRC and CC decreased with increasing depth at the 0-50 cm depth, and almost remained constant in the soil below 50 cm [30,37]. The limestone soils contained more SOM compared with the soils in the JRC.…”

“…Soil pH in the soils of the JRC ranged from 4.0 to 4.9, while it was 6.5-7.7 in the soils of the CC (Figure 2d). Soil pH in the JRC slightly decreased with increasing depth while slightly increased in the CC [30,37]. The lateritic red soils, red soils, and yellow soils were highly acid, while the limestone soils were neutral or weakly alkaline.…”

“…Clay-size particles in the soils of the JRC accounted for 9-17%, 56-71% for silt, and 15-33% for sand; while in the soils of the CC, clay accounted for 16-23%, 78-83% for silt, and nearly no sand (Figure 2a-c). Soil particle distribution in the JRC and CC fluctuated within a narrow range without obviously increasing or decreasing trend with increasing depth [30,37]. Although the soils in both the JRC and CC were classified into silt loam based on soil texture classes defined by the USDA [36], the soils in the JRC were coarser textured than those in the CC.…”

“…Standard material of low-organic-content soil (Organic analysis standard OAS: B2152, C: 1.55 ± 0.04%; N: 0.13% ± 0.01%) was repeatedly measured to monitor the reproducibility, and the precision was better than ±0.1% for C and ±0.02% for N. The actual contents of SOC and SON should be calibrated due to the loss of carbonate and inorganic N in their removing processes [37]. The data of soil properties in the JRC and CC have been reported in [30] and [37], respectively.…”

“…Secondary forest land and shrub land: 45%; agricultural land: 50% Note: MAT, mean annual temperature; MAP, mean annual precipitation. Data were cited from [30][31][32][33][34].…”