Xu et al. 2016 - Metal accumulation in Beijing agricultural soils

Xu and colleagues measured metals in 134 composite surface-soil samples from agricultural sites in Beijing and evaluated how land use, soil type, road density, and distance from the urban center affected accumulation. This is primary environmental evidence for agricultural soil. It is useful for soil-to-crop and exposure-context pages, but it is not a crop, food, ingredient, or product occurrence source.

Key numbers

All concentrations below are from Table 1 and are reported as mg/kg dry weight in agricultural soil.

The paper reports the mean concentration order as Zn > Cu > Ni > Pb > As > Cd > Hg. Compared with Chinese Environmental Quality Standard for Soils guideline values cited by the paper, only one sample exceeded the Cd guideline value; the other sampled metal concentrations were below the cited guideline values.

Table 4 split the 134 samples by the two dominant soil types:

The authors found significant land-use differences for Zn, Cu, and Cd. Greenhouse land had the highest reported average values for Cd (0.27 mg/kg dw), Cu (28.2 mg/kg dw), Hg (0.09 mg/kg dw), Ni (25.4 mg/kg dw), and Zn (95.1 mg/kg dw). Orchard land had the largest reported average values for Pb (24.7 mg/kg dw) and As (9.20 mg/kg dw). Distance from the urban center was significantly negatively correlated with Hg and Zn, while road density was positively correlated with Cd.

Methods (brief)

Soil sampling was conducted in 2011 at agricultural sites in Beijing. Each of the 134 samples was a composite of five subsamples collected with a stainless-steel auger. Samples were air-dried, sieved, and split for pH and metal analysis.

Pb, Ni, Cu, Zn, and Cd were digested using HCl, HNO3, HF, and HClO4 and measured by atomic absorption spectrophotometry. As and Hg were digested using aqua regia and measured by atomic fluorescence spectrophotometry. The study used Chinese soil standard reference materials GSS-1 and GSS-2 for QA/QC. Reported recovery ranges were 95%-105% for Cu, 96%-108% for Zn, 92%-102% for Ni, 92%-98% for Pb, 101%-103% for As, 98%-103% for Cd, and 95%-98% for Hg. Detection limits were 0.04 mg/kg for Cu, 0.01 mg/kg for Cd and As, 0.05 mg/kg for Ni, Pb, and Zn, and 0.002 mg/kg for Hg.

Implications

Certification: Do not admit this source into product or ingredient benchmark pools. The matrix is agricultural soil, not a food or consumer product, and the paper does not report crop concentrations or soil-to-crop transfer factors.

App: Use as context for agricultural-soil contamination, urbanization effects, and possible source attribution around Cd, Hg, Zn, Cu, Pb, Ni, and total As in Beijing. It can support soil and exposure-context pages, not HMTc product rows.

Courses: Useful for teaching matrix fit, dry-weight soil basis, total-metal digestion, and how land use, road density, and soil type can shape contaminant baselines before food-chain transfer is evaluated.

Wiki pages this source may touch

• index
• index
• arsenic
• cadmium
• copper
• mercury
• nickel
• lead
• zinc

Verification notes

This page was built from the full PDF, including the sampling and metals-analysis methods, Table 1, Table 4, land-use results, MANOVA discussion, and conclusion. The objective statement mentions chromium, but the reported descriptive tables, result narrative, and conclusion summarize As, Cd, Cu, Hg, Ni, Pb, and Zn only; this page therefore does not invent chromium values. Arsenic and mercury are total digestion/element measures, not species-specific iAs or methylmercury. No crop, food, ingredient, product, or brand concentration data are reported.

Page history

The five most recent substantive edits to this page. The full version history lives in git; when DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.