Concentration and Spatial Distribution of Potentially Toxic Elements in Surface Soil of a Peak-Cluster Depression, Babao Town, Yunnan Province, China

Abstract

Potentially toxic elements (PTEs) in Chinese agricultural soils, including those in some heritage protection zones, are serious and threaten food safety. Many scientists think that these PTEs may come from parent rock. Hence, at a karst rice-growing agricultural heritage area, Babao town, Guangnan County, Yunnan Province, China, the concentrations of eight PTEs (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) were determined in 148 surface soil, 25 rock, and 52 rice grain samples. A principal component analysis (PCA) and hierarchical cluster analysis were used to divide the surface soil into groups, and inverse distance weighting (IDW) was used to analyze the spatial distribution of PTEs. Soil pollution was assessed with the geoaccumulation index (Igeo). The results show that Cd, Hg, Zn, and Cr were polluting the soil (average Igeo > 0). The highest concentration of PTEs was distributed in the southwest of Babao town in the carbon rock area, which had the highest pH and soil total organic carbon (Corg), Mn, and TFe2O3 contents. PCA biplots of soil samples showed that the carbon rock area was associated with the most species of PTEs in the study area including Pb, Cd, Hg, As, and Zn. The clastic rock area was associated with Cu and Ni, and the lime and cement plants were associated with CaO, pH, Corg, TC, and aggravated PTE pollution around factories. In high-level PTE areas, rice was planted. Two out of 52 rice grain samples contained Cd and 4 out of 52 rice grain samples had Cr concentrations above the Chinese food safety standard pollutant limit (Cd 0.2 mg/kg; Cr 1 mg/kg). Therefore, the PTEs from parent rocks are already threatening rice safety. The government should therefore plan rice cultivation areas accordingly.

Assessment of the Heavy Metal Contamination of Roadside Soils Alongside Buddha Nullah, Ludhiana, (Punjab) India

“…Thus, the study of heavy metal pollution in soils is the need of the hour. Many studies have been conducted to explore the spatial distribution of heavy metal pollution in roadside soils [17][18][19][20][21][22][23][24].…”

“…However, a number of parameters, the huge data and the variability of data, can designate the level of pollution, but make it difficult to compare the pollution levels of various sites. To overcome this problem, a broad ranging approach has been applied by various researchers to assess the soil pollution, which includes the usage of various indices, such as the heavy metal pollution index (HPI), geoaccumulation index (Igeo), enrichment factor (EF), contamination factor (CF) and ecological risk index (RI) [21,24,[34][35][36][37][38][39][40][41].…”

Lithology and Human Activities Determine the Distribution and Pollution Level of Potentially Toxic Elements in the Topsoil of the Karst Region, Southwestern China

“…The concentration of PTE in lime soil is high, but in a relatively stable state under the background of calcium-rich geochemistry [35]. Cd in the karst areas of southwest China exceeded the standard rate of 95.83% in the previous study, but the water-soluble and exchangeable Cd concentration only accounted for 0.14% and 1.68%, respectively [36], and the Cd concentration in food crops does not exceed the edible safety standards [37]. However, 95% of rice grains harvested from limestone soil in Guangxi had a Cd concentration over the maximum permissible concentration [38].…”

Modeling and Assessing the Spatial and Vertical Distributions of Potentially Toxic Elements in Soil and How the Concentrations Differ

“…Natural phenomena and anthropogenic activities are the two major sources that determine the concentrations of PTEs in soils [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ]. Natural phenomena are described as the components generated from parent material, whereas anthropogenic sources primarily originate from acute human activities [ 17 , 18 , 25 , 26 ].…”

“…Natural phenomena and anthropogenic activities are the two major sources that determine the concentrations of PTEs in soils [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ]. Natural phenomena are described as the components generated from parent material, whereas anthropogenic sources primarily originate from acute human activities [ 17 , 18 , 25 , 26 ]. Many authors have revealed that natural sources of some PTEs (such as Pb, Cd, and Hg) have been surpassed by anthropogenic deposits into soils due to pedogenesis [ 17 ].…”