This survey assessed eight metals, including tungsten, in agricultural soils at six sites around the Dayu tungsten mining area and seven metals in paired rice grain. Tungsten and molybdenum showed the largest exceedances of provincial soil background values, and sites closest to historical and active mines were most polluted. Tungsten was not reported in rice, and the human health risk assessment covered other metals.
Key numbers
- Jiangxi soil background value used for tungsten: 4.93 mg/kg (Abstract; Methods).
- Mean soil tungsten exceeded the background value by 19.3 times; 97.2% of soil samples were above background (Results, p. 8).
- Screening value used for tungsten: 3 mg/kg, taken from the Dutch standard because the Chinese agricultural soil screening list cited by the authors has no tungsten value (Results, p. 8).
- Mean contamination factor for tungsten 16.55, indicating very high contamination (Results, p. 12).
- Tungsten ecological risk factor means of 35.04, 63.98, 34.99 and 36.72 at sites FJ-N, FJ-S, HL and QL (Results, p. 14).
- Tungsten showed high spatial variability (coefficient of variation between 50% and 100%) (Results, p. 8).
- Rice table reports arsenic, cadmium, chromium, copper, molybdenum, lead and zinc, but not tungsten (Table 6, p. 14).
Methods (brief)
Composite topsoils (four to six subsamples per grid) were air-dried and sieved; soils and sun-dried rice grain were digested with H2SO4, HNO3 and HF by microwave and measured by ICP-MS (iCAP Q). Quality control used blanks, duplicates and the GSS-5 lateritic soil reference (n = 12; tungsten SD 0.25%, relative error -0.55%). Pollution indices (geo-accumulation, contamination factor, pollution load) and ecological and health risk indices were calculated.
Evidence fitness
Supports statements that agricultural soils near the Dayu tungsten mines carry tungsten well above regional background, and gives index-based comparisons. Absolute tungsten concentrations are in a supplementary table not included here. The paper does not support statements about tungsten in rice or about dietary tungsten risk.
Limitations
Absolute soil tungsten values sit in supplementary Table S1. Tungsten in rice was not reported. The soil screening value for tungsten is borrowed from a Dutch standard rather than a food-safety limit. The rice intake figure in the risk model applies to the other metals assessed.
Related evidence
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