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An area of Watershed 3 in Hubbard Brook Experimental Forest containing a seep, a spring and a swale was found to contain hot spots for soil manganese. The source of the Mn was thought to be groundwater discharge, and this area was studied intensively due to its implications for disproportionately affecting headwater stream chemistry. Soils were sampled along a grid pattern; O and B horizon samples were collected and analyzed for dithionite-extractable (total secondary) Mn & Fe, pH, total organic C and N, moisture content, and Cr oxidation potential (indicative of Mn oxide reactivity). The data were spatially interpolated to identify areas of Mn enrichment and other chemical variables related to topography and groundwater discharge. Two hot spots for soil Mn were found: one in a poorly drained, flowing spring and one in a moderately well-drained swale, which had similarly high Mn (6000-9000 mg kg-1 soil). However, the spring soils had high Cr oxidation potential while the nearby swale soils did not, indicating a difference in Mn reactivity. A third location in the study area was a poorly drained seep with water that was not visibly flowing, and these soils had lower quantities of Mn and low Cr oxidation potential. 

In headwater catchments, surface groundwater discharge areas have unique soil biogeochemistry and can be hot spots for solute contribution to streams. Across the northeastern United States, headwater hillslopes with surface groundwater discharge were enriched in soil Mn, including Watershed 3 of Hubbard Brook Experimental Forest, New Hampshire. Soils of this site were investigated along a grid to determine extent of Mn‐rich zone(s) and relationships to explanatory variables using ordinary kriging. The O and B horizons were analyzed for total secondary Mn and Fe, Cr oxidation potential, total organic C, moisture content, wetness ratio, and pH. Two Mn hot spots were found: a poorly drained, flowing spring (Location A); and a moderately well‐drained swale (Location B). Both had ∼6,000–9,000 mg Mn kg^–1soil. However, Location A had high Cr oxidation potential (a measure of Mn reactivity), whereas Location B did not. Location C, a poorly drained seep with slow‐moving water, had lower Mn content and Cr oxidation potential. Manganese‐rich soil particles were analyzed using X‐ray absorption near‐edge structure and micro‐X‐ray diffraction; the dominant oxidation state was Mn(IV), and the dominant Mn oxide species was a layer‐type Mn oxide (L‐MnO₂). We propose input of Mn(II) with groundwater, which is oxidized by soil microbes. Studies of catchment structure and response could benefit from identifying hot spots of trace metals, sourced mainly from parent material but which accumulate according to hydropedologic conditions. Small‐scale variation in Mn enrichment due to groundwater and microtopography appears to be more important than regional‐scale variation due to air pollution.