Phytoremediation Efficacy of Salix discolor and S. eriocephela on Adjacent Acidic Clay and Shale Overburden on a Former Mine Site: Growth, Soil, and Foliage Traits

Abstract

Plants regularly experience suboptimal environments, but this can be particularly acute on highly-disturbed mine sites. Two North American willows-Salix discolor Muhl. (DIS) and S. eriocephala Michx. (ERI)-were established in common-garden field tests on two adjacent coal mine spoil sites: one with high clay content, the other with shale overburden. The high clay content site had 44% less productivity, a pH of 3.6, 42% clay content, high water holding capacity at saturation (64%), and high soil electrical conductivity (EC) of 3.9 mS cm −1 . The adjacent shale overburden site had a pH of 6.8, and after removing 56.5% stone content, a high sand content (67.2%), low water holding capacity at saturation (23%), and an EC of 0.9 mS cm −1 . The acidic clay soil had significantly greater Na (20×), Ca (2×), Mg (4.4×), S (10×), C (12×) and N (2×) than the shale overburden. Foliar concentrations from the acidic clay site had significantly greater Mg (1.5×), Mn (3.3×), Fe (5.6×), Al (4.6×), and S (2×) than the shale overburden, indicating that these elements are more soluble under acidic conditions. There was no overall species difference in growth; however, survival was greater for ERI than DIS on both sites, thus overall biomass yield was greater for ERI than DIS. Foliar concentrations of ERI were significantly greater than those of DIS for N (1.3×), Ca (1.5×), Mg (1.2×), Fe (2×), Al (1.5×), and S (1.5×). There were no significant negative relationships between metal concentrations and growth or biomass yield. Both willows showed large variation among genotypes within each species in foliar concentrations, and some clones of DIS and ERI had up to 16× the Fe and Al uptake on the acidic site versus the adjacent overburden. Genetic selection among species and genotypes may be useful for reclamation activities aimed at reducing specific metal concentrations on abandoned mine sites. Results show that, despite having a greater water holding capacity, the greater acidity of the clay site resulted in greater metal mobility-in particular Na-and thus a greater EC. It appears that the decline in productivity was not due to toxicity effects from the increased mobility of metals, but rather to low pH and moisture stress from very high soil Na/EC.

Unweaving the population structure and genetic diversity of Canadian shrub willow

“…On Prince Edward Island, the willow cultivars S. viminalis (5027) and S. dasyclados (SV1) can yield up to 18–20 odt ha −1 y −1 when planted as riparian buffer strips along watercourses 18 . Consequently, shrub willow are increasingly garnering attention in SRC systems for their uses in managing wetlands 19 , intercepting excess nutrient runoff 20 , remediating industrial soils and wastewater 21 , 22 , and improving the biodiversity of birds and insects 23 .…”

Mercury sulfur initiative

“…The performance of systems designed for phytoremediation of sulfur are also largely influenced by site conditions such as climatic and soil variables. Therefore, selecting the proper plants that are matched to the contaminants and specific site conditions is of utmost importance for reclamation (Mosseler and Major 2017;,Pilipović et al 2021, Xu et al 2019a. Use of plant materials following maturity will likely be in wood products or converted to biochar for longer-term storage.…”

“…, Guittonny-Larchevêque and Lortie 2017,Mosseler and Major 2017, Suo et al 2021), though results specifically related to remediation of sulfur species at the field scale are limited and not well-tested for effectiveness.Building upon this research, phyto-recurrent selection can be utilized in the context of sulfur mitigation to select and outplant SRWCs on contaminate sites. Specifically, this effort will (1) select tree varieties to maximize sulfur remediation; (2) establish demonstration plantings and conduct monitoring to evaluate the efficacy of SRWC-based phytoremediation of sulfur; (3) develop specialized laboratory methods to quantify sulfur species throughout the system; and (4) conduct education, outreach, and technology transfer activities that involve engaging directly with community members, Tribal citizens, and other stakeholders.…”

Populus nigra as a phytoremediator for Cd, Cu, and Pb in contaminated soil

“…This is because carbohydrates formed during photosynthesis are the source of carbon and energy necessary for growth, lignification, and biomass formation. Overall, foliage elements differ according to their concentrations in soil or soil chemistry and due to the plant species or clones of Salix (Mosseler and Major 2017). According to El-Mahrouk et al (2019), the decrement in N, P, and K % in leaves of Salix mucronata was increased with raising the concentrations of Cd Cl2 (20 to 80 mg/kg soil ), CuCl2 (50 to 200 mg/kg soil), and Pb acetate (250 to 850 mg/kg soil) in the soil.…”