Precipitation and topsoil attributes determine the species diversity and distribution patterns of crustal communities in desert ecosystems

Aims

The objectives of this research were to determine the optimal pH for maximizing boron (B) accumulation in cattail (Typha latifolia) shoots, and to develop treatment systems for the removal of B from wastewater.

Methods

We performed a hydroponic experiment to examine the effects of pH on shoot B accumulation in cattail plants. Cattails were grown in nutrient solutions containing B at three concentrations (25, 75, and 125 mg B L^?1, in the form of H₃BO₃), supplied at seven pH levels ranging from 4.0 to 10.0. In addition, we compared the effectiveness of B removal by cattails cultured in floating islands and in upward-flow mesocosms.

Results

The effects of pH on growth and B accumulation, although significant, were relatively small compared to the effect of B on the relationship between shoot growth and shoot B accumulation. Cattail floating islands and cattail upward-flow mesocosms reduced concentrations of B in the solutions by 12.5–21.4 % and 12.2–21.3 %, respectively, in the first cycle, and by 11.0–14.2 % and 4.0–13.4 %, respectively, in the second cycle. The higher B removal efficiencies of the floating islands occurred at lower B concentrations, whereas the opposite was observed for the upward-flow mesocosms. Cattails can regenerate rapidly after harvesting of the upper shoots; however, B concentrations in the regenerative upper shoots were found to be lower than that in the first-growth upper shoots.

Conclusions

Optimal pH for shoot B accumulation by cattails is 6.0. Although direct comparisons between the effectiveness of B removal by floating islands and upward-flow mesocosms are difficult, we concluded that upward-flow mesocosms are more suitable for the treatment of B-contaminated wastewater.