Geochemical differences and sources of mineral elements in soil and coffee beans from pu'er and Baoshan, China

Yunnan is a major coffee region in China. This study explores mineral sources and bioavailability to identify geochemical indicators for origin traceability.

We analyzed 85 soil, 52 coffee beans, and 4 bedrock samples from Pu'er and Baoshan, Yunnan. Eleven elements (Cr, Cu, Mn, Zn, Ca, K, Mg, Fe, Pb, Mo, As) were measured by coupled plasma mass spectrometry, along with soil pH and organic matter. Enrichment factors, bioconcentration factors, principal component analysis, and partial least squares regression were applied to assess elemental mobility, sources, and traceability.

K, Ca, Mg, Cu, and Mo showed high bioavailability with greater uptake in Pu'er. Lead, As, Mn, Zn, Fe, and Cu accumulated more in Pu'er beans, while Cr was enriched in Baoshan. Chromium, Mo, and As derived from human activities, whereas Mg, Ca, and K from weathering rock. Elemental sources in Pu'er involved weathering, industry, and agriculture; in Baoshan, coal combustion, mining, and agriculture dominated. Three latent variables were extracted, with higher explanatory power in Pu'er (Xp = 78.07%, Yp = 38.69%) than Baoshan (Xb = 46.26%, Yb = 29.49%). The LV1 axis clearly distinguished origins, identifying Cr, Cu, Ca, and Mg as key soil indicators for coffee traceability.

All toxic elements were below safety limits. Pu'er showed higher Pb and As accumulation, while Baoshan had more Zn and Mn. Natural weathering mainly contributed to Mg, Ca, and K; human activities influenced Cr, Mo, and As. Partial least squares regression effectively distinguished origins, highlighting Cr, Cu, Ca, and Mg as effective markers for distinguishing coffee origins.