Contribution of SO₃ to the acid neutralizing capacity of Andosols exposed to strong volcanogenic acid and SO₂ deposition

Abstract

Summary Soil response to acid and sulphur inputs is influenced largely by the soil's physico‐chemical properties. We studied the effects of such depositions in two types of Andosols exposed to volcanogenic emission (Masaya, Nicaragua), namely Eutric Andosols rich in allophanic constituents, and Vitric Andosols rich in volcanic glass. Small mineral reserves and large contents of secondary short‐range ordered minerals indicate a more advanced weathering of the Eutric than the Vitric Andosols. Strong correlations between soil specific surface and oxalate‐extractable Al, Si and Fe contents highlight the predominant contribution of short‐range ordered minerals to surface area. Both types of Andosols showed a decrease in pH upon acid input. Sulphur deposition increased the soil's S content to 5470 mg S kg−1. However, the acid neutralizing capacity of the soil solid phase (ANCs) was not significantly affected by the acid and S inputs. Non‐exchangeable (mineral reserve) and exchangeable cations and total contents of sulphur and phosphorus dictate most of the ANCs variation. In the Vitric Andosols, mineral reserves contributed up to 97% to these four additive pools, whereas the exchangeable cations accounted for 1–4%. In the Eutric Andosols, the contribution of mineral reserves was less (71–92%), but the exchangeable cation content was greater (1–20%), whereas the contribution of sulphur and phosphorus was significant at 1–15% and 2–7%, respectively. The main process involved in H+ consumption is mineral weathering in Vitric Andosols and ion exchange in Eutric Andosols.

Leaf silicon content in banana (Musa spp.) reveals the weathering stage of volcanic ash soils in Guadeloupe

“…Since weathering depletes primary minerals, elements are lost to leaching. Figure 3 shows that the loss of Si and TRB (Ca, Mg, K, Na) parallels a relative concentration of Al and Fe, confirming previous data obtained in various tropical volcanic environments (Delvaux et al 1989;Nieuwenhuyse et al 1994;Chadwick et al 2003;Delfosse et al 2005). In our soils developed on similar andesitic ash, the concomitant decrease of the total Si content and TRB (r = 0.74) reveals the advanced weathering stage of the Es soils relatively to Ws (Table 3, Fig.…”

Sulphate sorption at high equilibrium concentration in Andosols

“…This area is covered with Andosols developed from successive basaltic tephra layers, with remarkably uniform chemical composition (Walker et al, 1993). A previous study indicated that the Andosols differ by their weathering stage (Delfosse et al, 2005b). Young and comparatively less weathered profiles (Vitric series; VI) are located within 5 km from the volcano, whereas more weathered soils (Eutric series; EU) are found farther downwind (see Delfosse et al (2005b) for details on soil locations and major properties).…”

Major and trace element distributions around active volcanic vents determined by analyses of grasses: implications for element cycling and bio-monitoring

“…The soils downwind of Masaya are also impacted by volcanic emissions, with "soils" within the devegetated zone best described as thin gravels. The andosols that develop further downwind (> 4 km) show increased acidity (resulting in lower exchangeable base cations) and increased sulphate, chloride and fluoride concentrations due to deposition from Masaya's plume (Delmelle et al 2003;Delfosse et al 2005).…”

“…In contrast, the chemical impacts of volcanism on vegetation occur over wider areas and arise from all styles of activity. Direct gas and aerosol fumigation (Notcutt and Davies 1989a, b;Delmelle et al 2001Delmelle et al , 2002Allen et al 2006;Bellomo et al 2007;Martin et al 2009a), acid rain (e.g., Cape 1993) and leaching of elements adsorbed on tephra (Cronin et al 1998;Martin et al 2009b) may provoke a variety of responses from vegetation (potentially mediated by soil chemistry, e.g., if acid deposition leads to loss of elements from the soil to groundwater; Delmelle et al 2003;Delfosse et al 2005). The most severe impact is the death of vegetation following volcanic eruptions and a significant reduction in biodiversity; in the case of persistent quiescent activity, wide areas of land may be permanently uninhabitable to all but the most tolerant of vegetation species (Delmelle et al 2002).…”