Potentially toxic metal(loid) distribution and migration in the bottom weathering profile of indigenous zinc smelting slag pile in clastic rock region

Abstract

Background There are contaminated by potentially toxic metal(loid)s (PTMs) that the surface soil and the weathering profiles around the indigenous zinc smelting slag piles or smelters in the smelting area. However, few systematic studies are currently focusing on the PTM distribution and migration among the slag and its bottom weathering profile. Methods This research determined the concentrations of PTMs and pH values. And we analyzed PTM distribution in the two weathering profiles (slag-covered and slag-absent) with a small horizontal distance in the clastic rock region in the smelting area. Results The soil As and Pb contents, respectively, within the 30 and 50 cm depth in the slag-covered section were higher than those in the slag-absent profile. All soil Cd and Zn contents of the slag-covered core were significantly higher than those in the slag-absent weathering section. Conclusions Compared with the slag-absent weathering section, some PTMs (i.e., As, Cd, Pb and Zn) in the bottom weathering profile were polluted by these elements in the covered slag in the clastic rock region, and their depths were influenced by the slag to varying degrees. Additionally, with time, some PTMs (especially Cd and Zn) of the slag might finally contaminate the groundwater by leaching and infiltration through its bottom weathering profile in the clastic rock region.

Source Identification and Superposition Effect of Heavy Metals (HMs) in Agricultural Soils at a High Geological Background Area of Karst: A Case Study in a Typical Watershed

“…Bi et al estimated that approximately 450 t of Cd was released into the local atmosphere from zinc smelters at Hezhang County from 1989 to 2001 [ 49 ]. Despite the fact that indigenous zinc smelting had been forbidden, the long smelting history has contaminated surrounding soils, which generated concentrations of HMs in this area that were higher than they were in others [ 9 , 50 ]. With the help of wind, soils also became an important source of atmospheric deposition [ 51 , 52 ].…”

“…In the 1980s, especially, many zinc smelters caused serious soil pollution with Cd and Pb. Furthermore, a lot of small dispersive zinc smelting slag, containing a high content of HMs [ 9 ], can be seen everywhere in this area. This slag polluted surrounding soils through surface runoff and dust fall and migrated to farmland [ 10 , 11 , 12 ].…”

“…Exogenous sources of HMs included mining, industrial sources (such as the metal smelting plants, thermal power plants and alkylation plants) [ 14 , 15 , 16 , 17 ], agricultural sources (fertilizers, pesticides and livestock manure) [ 18 , 19 ] and traffic sources (wear of metal parts and exhaust emission) [ 20 ]. In addition, the soil of the karst area, compared to that of non-karst area, is characterized by thin regoliths, uneven distribution, and high porosity [ 21 , 22 ], which contributed to the migration of HMs from the surface to the subsoil and even contaminated underground water [ 9 , 23 ]. The process by which HMs entered crops from soils consisted of three stages: the movement of HMs in soils, accumulation of HMs in crop roots and transportation of them to the shoots [ 24 ].…”

Distribution characteristics of potentially toxic metal(loid)s in the soil and in tea plant (Camellia sinensis)

“…Pollution index (PI) is a valuable tool to express the degree of hazard by calculating the ratio of the measured potentially toxic metal(loid) value of the soil to the evaluation standard value of the element 32 . The calculation formula is as follows: …”

“…Enrichment factor (EF) is a relative abundance of elements that helps distinguish the source of chemical elements from an anthropogenic source or natural source 32 , 34 – 36 . The enrichment factor formula is as follows: …”