The Source, Spatial Distribution and Risk Assessment of Heavy Metals in Soil from the Pearl River Delta Based on the National Multi-Purpose Regional Geochemical Survey

Abstract

The data on the heavy metal content at different soil depths derived from a multi-purpose regional geochemical survey in the Pearl River Delta (PRD) were analyzed using ArcGIS 10.0. By comparing their spatial distributions and areas, the sources of heavy metals (Cd, Hg, As and Pb) were quantitatively identified and explored. Netted measuring points at 25 ×25 km were set over the entire PRD according to the geochemical maps. Based on the calculation data obtained from different soil depths, the concentrations of As and Cd in a large area of the PRD exceeded the National Second-class Standard. The spatial disparity of the geometric centers in the surface soil and deep soil showed that As in the surface soil mainly came from parent materials, while Cd had high consistency in different soil profiles because of deposition in the soil forming process. The migration of Cd also resulted in a considerable ecological risk to the Beijiang and Xijiang River watershed. The potential ecological risk index followed the order Cd ≥ Hg > Pb > As. According to the sources, the distribution trends and the characteristics of heavy metals in the soil from the perspective of the whole area, the Cd pollution should be repaired, especially in the upper reaches of the Xijiang and Beijiang watershed to prevent risk explosion while the pollution of Hg and Pb should be controlled in areas with intense human activity, and supervision during production should be strengthened to maintain the ecological balance of As.

Bedrock geochemistry influences vegetation growth by regulating the regolith water holding capacity

“…Bedrock is the source of most mineral nutrients (e.g., Fe, P), which subsequently shapes plant growth and community composition 8,9 . Conversely, bedrock also supplies heavy metals (e.g., Hg, Pb and Cd), which can inhibit plant growth 10 . In addition, bedrock can influence the regolith texture and consequently control the water and nutrient retention capacity of the regolith 11 .…”

Distributions and risks of Cu, Cd, Pb and Zn in soils and rice in the North River Basin, South China

“…Therefore, more attention should be paid to potential food safety issues associated with paddy ecosystems (Neumann et al 2011;Li et al 2012). The complicated natural conditions (parent material and water regime) combined with intensive anthropogenic activities (mining and smelting, industrial processes) make the NRB region a perfect fit for research on heavy metals (Zhang et al 2015). Few studies have been conducted on heavy metal uptake by rice plants in this critical region, and even less on the potential health risks posed by the rice from the paddy soils in the NRB.…”

Environmental Pollution in Pearl River Delta, China: Status and Potential Effects

“…The soil was contaminated by Pb and Ni in great universality, and the other heavy metals Cd, Cr, Cu, and Zn exceeded the back-ground value in a typical area of PRD under intensive economic development (Ma et al, 2004). The degree of pollution decreased in the order Cd > Cu > Ni > centrations of As and Cd in a large area of the PRD exceeded the National Second-class Standard (Zhang et al, 2015) Zn > As > Cr > Hg > Pb in surface soils from the PRD (Bai and Liu, 2014). The degree of heavy metal pollution by land use decreased in the order waste treatment plants (WP) > urban land (UL) > manufacturing industries (MI) > agricultural land (AL) > woodland (WL) > water sources (WS) (Bai and Liu, 2014).…”

“…Pollution with some of the metals, including Cd, Cu, Ni, and Zn, was attributed to the recent rapid development of the electronics and electroplating industries (Bai and Liu, 2014).The control of Cd, Hg, and Pb should be prioritized in the PRD, and emissions in waste water, residue, and gas discharges from the electronics and electroplating industry should be decreased urgently (Bai and Liu, 2014). Cd, Hg, and Pb pose high potential ecological risks in all of the zones studied and the potential ecological risk index followed the order Cd >Hg > Pb > As (Zhang et al, 2015). Excessive accumulation of heavy metals in agricultural soils may not only result in environmental contamination, but elevated heavy metal uptake by crops may also affect food quality and safety (Wong et al, 2002).…”

“…Excessive accumulation of heavy metals in agricultural soils may not only result in environmental contamination, but elevated heavy metal uptake by crops may also affect food quality and safety (Wong et al, 2002). The migration of Cd also resulted in considerable ecological risk to the Beijiang and Xijiang River watershed (Zhang et al, 2015).…”