Effects of arsenic on nutrient dynamics of grassland microcosms and field plots

Abstract

Grassland field plots were compared to two sizes of excised microcosms (15 and 30 cm diameter) and 30-cm diameter homogenized microcosms to assess the effects of As on soil-plant nutrient dynamics. The goal of this experiment was to determine the feasibility of using microcosms for screening chemicals which are potentially toxic to terrestrial ecosystems. All experimental units were treated with As, at rates of 0, 0.5, and 5.0 mg cm -2, by superficial application of dissolved Na2AsO 4. Calcium, PO4-P , NO3-N , dissolved organic carbon (DOC), and NH4-N were determined in soil leachate and soil extracts. Greater loss of PO4-P, NO3-N, NH4-N , and DOC occurred via soil leachate from microcosms treated with the greatest level of As relative to untreated microcosms. Field plots were unaffected by As treatment. Excised microcosms were found to be more representative of field plots in reflecting microbial dynamics than were homogenized microcosms. Thus excised microcosms were recommended for testing potentially hazardous chemicals.

Advances in Microbial Ecology

“…5. The characteristics of these microcosms agree well with the tenets suggested for microcosms; in fact, intact soil cores gave a more sensitive toxic response than homogenized soil (Draggan, 1977;Jackson et al, 1979). Toxicant distribution and extractable nutrient concentrations during treatment of the soil cores were comparable to similar results from dosed field plots (Jackson et al .. 1979).…”

“…A soil-core microcosm has also been developed for screening chemicals in terrestrial systems (O'Neill et al, 1977;Jackson, et al, 1977Jackson, et al, , 1979Draggan, 1977). Again, microbial geochemical processes form the backbone of their toxic-effect responses.…”

Comparison of pots versus microcosms for predicting agroecosystem effects due to waste amendment

“…Jackson et al [8] found that the variability of fungal lengths was greater in homogenized soil microcosms than in intact soil-core microcosms. However, the same project reported similar variability in arsenic transport data for intact and homogenized cores [ 121.…”

“…These systems have ranged from small (5 x 5 cm) unplanted soil cores [4] to large (45 x 45 x 25 cm) forest microcosms containing saplings [5]. Some systems have been artificially constructed from laboratory components [6], and others have used sieved soil [7] or excised, undisturbed columns [8,9].…”

Arsenic Status and Distribution in Soils at Disused Cattle Dip in South Africa

“…This may have resulted in soil contamination. The toxic nature of arsenic has prompted various studies on its environmental behaviour in grassland ecosystem (Jackson et al 1979), the areas surrounding metal smelters (Crecelius et al 1974;Temple et al 1977;Pilgrim et al 1994), within soil/plant relationships (Shephard 1992), potable water (Valentine et al 1979) and soils at cattle dips (Kimber et al 2002) Upon the cessation of cattle dipping programme, disused vats are usually dismantled or they are allowed to decay naturally with local plants so that they eventually blend into the surrounding landscape. In other cases, the developed ecosystem, particularly, water resource is exposed to the toxic residue of the cattle dip substrate.…”