Metal contamination from mining, heavy traffic, and illegal mining pose a serious environmental threat, especially in urban and peri-urban areas where soils near roadsides and mine-adjacent zones are exposed to pollutants. Unregulated mining worsens contamination, affecting ecosystems and agricultural lands. Although grasses are often considered ineffective in multi-metal contaminated soils, Eragrostis curvula shows promise as a hardy native species for phytoremediation in such environments. This study examined whether the E. curvula cultivars, Ermelo and Agpal, showed potential to reduce metal concentrations in contaminated soils. Metal concentrations in pre-planting soils, post-harvest soils, and plant tissues were determined, and bioconcentration factors were calculated for samples from all soil collection sites. Pre-planting soils collected from Jameson Park, Kaydale, and Rensburg had high concentrations of iron (36 000–50 000), manganese (800–900), nickel (48–75), strontium (10–20), zinc (71–79), chromium (117–224), and barium (114–117) mg/kg, with a pH of 4.6–5.0 and total cation concentration of 4.7–10.9 cmol/L. The Ermelo cultivar accumulated iron (3 289–6 149), manganese (185–522), nickel (13–26), strontium (9–10), zinc (46–64), chromium (55–85), and barium (36–71) mg/kg, while the Agpal cultivar accumulated corresponding concentrations of 3 092–5 216, 136–488, 4–32, 8–26, 48–57, 21–122, and 37–77 mg/kg. The iron (9 000–32 000), manganese (200–809), nickel (31–63), strontium (8–16), zinc (33–73), chromium (83–137), and barium (73–113) mg/kg of post-harvest soils decreased significantly, while the pH increased to 5.2–5.6 and the total cation concentration was 4.3–7.2 cmol/L. The cultivars had varied bioconcentration factors for iron (0.06–0.15), manganese (0.12–0.57), nickel (0.08–0.53), strontium (0.37–1.10), zinc (0.51–0.93), chromium (0.10–0.89), and barium (0.33–0.68) indicating more efficient accumulation of zinc and strontium, while iron and chromium were taken up to a lesser extent. The presence of E. curvula cultivars in the soils promoted the proliferation of plant growth-promoting bacterial genera, including Bacillus, Pedobacter, Pseudomonas, and Flavobacterium, in the post-harvest soils. The activity of these bacteria and their associated soil enzymes may have contributed to the ability of E. curvula to maintain growth and persist under metal-contaminated conditions. These results highlight E. curvula’s potential as a phytoremediation agent in multi-source metal-polluted soils.

Soil Beneath the Grass: Eragrostis Curvula Cultivars Reduce Metal Contamination and Improve Soil Health

期刊论文
发表日期：

2025年12月17日

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Nqobile Motsomane,
Anathi Magadlela

摘要

Metal contamination from mining, heavy traffic, and illegal mining pose a serious environmental threat, especially in urban and peri-urban areas where soils near roadsides and mine-adjacent zones are exposed to pollutants. Unregulated mining worsens contamination, affecting ecosystems and agricultural lands. Although grasses are often considered ineffective in multi-metal contaminated soils, Eragrostis curvula shows promise as a hardy native species for phytoremediation in such environments. This study examined whether the E. curvula cultivars, Ermelo and Agpal, showed potential to reduce metal concentrations in contaminated soils. Metal concentrations in pre-planting soils, post-harvest soils, and plant tissues were determined, and bioconcentration factors were calculated for samples from all soil collection sites. Pre-planting soils collected from Jameson Park, Kaydale, and Rensburg had high concentrations of iron (36 000–50 000), manganese (800–900), nickel (48–75), strontium (10–20), zinc (71–79), chromium (117–224), and barium (114–117) mg/kg, with a pH of 4.6–5.0 and total cation concentration of 4.7–10.9 cmol/L. The Ermelo cultivar accumulated iron (3 289–6 149), manganese (185–522), nickel (13–26), strontium (9–10), zinc (46–64), chromium (55–85), and barium (36–71) mg/kg, while the Agpal cultivar accumulated corresponding concentrations of 3 092–5 216, 136–488, 4–32, 8–26, 48–57, 21–122, and 37–77 mg/kg. The iron (9 000–32 000), manganese (200–809), nickel (31–63), strontium (8–16), zinc (33–73), chromium (83–137), and barium (73–113) mg/kg of post-harvest soils decreased significantly, while the pH increased to 5.2–5.6 and the total cation concentration was 4.3–7.2 cmol/L. The cultivars had varied bioconcentration factors for iron (0.06–0.15), manganese (0.12–0.57), nickel (0.08–0.53), strontium (0.37–1.10), zinc (0.51–0.93), chromium (0.10–0.89), and barium (0.33–0.68) indicating more efficient accumulation of zinc and strontium, while iron and chromium were taken up to a lesser extent. The presence of E. curvula cultivars in the soils promoted the proliferation of plant growth-promoting bacterial genera, including Bacillus, Pedobacter, Pseudomonas, and Flavobacterium, in the post-harvest soils. The activity of these bacteria and their associated soil enzymes may have contributed to the ability of E. curvula to maintain growth and persist under metal-contaminated conditions. These results highlight E. curvula’s potential as a phytoremediation agent in multi-source metal-polluted soils.