Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 15, 1998
Publication Date: N/A
Interpretive Summary: Drainage water reuse is being proposed for reducing the volume of saline drainage water in the west side of central California. However, saline effluent collected in some regions of central California contains potentially a new hazard to long-term drainage water reuse, namely the presence of boron (B) and selenium (Se). Over the past decade, a variety of plant and tree species have been tested for the purpose of receiving drainage water. Tree species used as recipients of drainage water offer advantages over plant species because they: 1) transpire large quantities of water; 2) produce large amount of plant biomass; 3) concentrate the total dissolved salts within their tissue; and 4) have long life spans. One such tree species which has been used successfully elsewhere for managing some inorganic and organic compounds is the Populus species. Thus, the purpose of this study was to evaluate B and Se accumulation by hybrid Poplar clones irrigated with effluent containing increasing levels of chloride salt, B, and Se. Our results demonstrated that the Poplar clones are moderately successful for removing B and Se from a poor quality effluent. Their ability, however, decreases with increasing salinity levels. Additional breeding and selecting for salt tolerance will be necessary to successfully use Poplar trees for extracting B and Se from a saline effluent.
There has been much interest recently in central California for reusing water on tree species. A sand culture study was conducted to investigate the accumulation of boron (B) and selenium (Se) in eight hybrid Poplar (Populus) clones irrigated with synthetic agricultural effluent containing varying levels of chloride salt, B and Se. Electrical conductivity (EC) ranged from 1.5-15 dS/m, B levels from 1-5 mg/L, and Se levels from 100-500 micro gram/L. Compared to the other tree organs, the leaves accumulated the greatest concentrations of B and Se by 4 months of growth. The results show that leaf B concentrations were positively correlated with EC levels (r=0.78, P<0.001) and negatively correlated (r=-0.53, P<0.001) with leaf dry matter for all clones at all tested B levels. Both leaf and stem Se data show a significant decrease (P<0.05 level) in tissue accumulation of Se with increased salinity. Toxicity symptoms (e.g., burning leaf margins, shoot die back) occurred in most clones grown at 12 and 15 dS/m treatments. Based on the data the clone 49177 (Populus tricarpa x P. deltoidus) best tolerated the tested parameters among the clones and accumulated the greatest amount of B and Se. The moderate ability of the Populus species to remove and accumulate B and Se from saline effluent is most effective at salt levels below 7 dS/m. More research is necessary under field conditions.