The impact of red mud on growth of wetland vegetation and substrate fertility

Abstract

Greenhouse experiments were conducted to evaluate the impact of "'red mud", the residue of the Bayer process for extracting alumina from bauxite, on wetland to investigate whether red mud can be used for wetland restoration. Two wetland species, Spartina alterni/lora Loisel. and Sagittaria lanci/'olia L., were used to test their response to the following substrate treatments: 100 % marsh sediment, 100 % red mud, a mixture of 50 % marsh sediment and 50 % red mud, a mixture of 50 % red mud and 50 % compost, and neutralized red mud. Each substrate treatment received two fertilization levels, fertilized (N-P-K) and unfertilized. Red mud could support the growth of the salt marsh species, Spartina aherni/lora, but not the fresh marsh species, Sagittaria lancifolia. The high Na content and salinity of red mud, even when mixed with marsh sediment or compost, appeared to be the primary cause for the high mortality of Sagittaria in these substrates. Fertilization did not reduce the stress response of Sagittaria to red mud, but significantly increased the growth of Spartina. Red mud is low in available N and P and required fertilizer or organic matter (e.g., compost) addition to increase fertility. In experiments with both fresh and salt marsh sediments, the concentrations of soluble heavy metals, with the exception of Mn, were not significantly greater for red mud than for marsh sediment. Thus, the release of heavy metals from red mud over the short-term may not pose an environmental concern. However, the mobilization of heavy metals over the long-term and the influence of plants in accumulating metals requires further investigation.

The Influence of Salinity on the Uptake, Distribution, and Excretion of Metals by the Smooth Cordgrass, Spartina alterniflora (Loisel.), Grown in Sediment Contaminated by Multiple Metals

“…Sediment redox measurements were taken from multiple pots midway through the experiment using Pt wire electrodes and a calomel reference electrode with a generic voltmeter. All redox values were calculated by adding +244 to recorded values (Kong and Mendelssohn 1996).…”

Effects of red mud addition on cadmium accumulation in cole (Brassica campestris L.) under high fertilization conditions

“…Comprehensive uses of RMD including food crop and horticultural plant growth promotion and infertile soil improvement have received considerable attention (Kong and Mendelssohn 1996;Cai et al 1997;Jiang and Ning 2003;Giovanni et al 2014). Studies of the effects of RMD addition to soil on heavy metal bioavailability in plants have been conducted (Giovanni et al 2014;Sun et al 2015), but the influences of RMD addition on vegetable growth and heavy metal accumulation under high fertilization conditions were rarely addressed.…”