پديد آورندگان :
نسرين ياورعشايري, نسرين ياورعشايري* دانشگاه شيراز - دانشكده علوم زمين - گروه زمين شناسي , مر, فريد دانشگاه شيراز - دانشكده علوم زمين - گروه زمين شناسي , كشاورزي, بهنام دانشگاه شيراز - دانشكده علوم زمين - گروه زمين شناسي
چكيده لاتين :
Aquatic macrophytes are widespread plant species that play an essential role in wetland biogeochemistry because they are the principal living accumulators of heavy metals through the active and passive circulation of elements (Bonanno et al., 2017). Due to the hyper absorption potential of heavy metals from the environment and accumulating in plant organs and their defense mechanism against metal pollution, some of the macrophytes can be used for the biomonitoring of aquatic pollution (Esmaeilzadeh et al., 2017; Zhou et al., 2008). Heavy metals may adversely affect the precarious stability of wetlands whose ecological importance for nutrient cycling and pollution control is widely recognized (Mitsch and Gosselink, 2007). In wetlands all over the world, many researchers have measured the metal accumulation in tissues of different plant species (Phillips et al., 2015; Ramachandra et al., 2018; Weis and Weis, 2004). The objectives of this study were to (i) determine the concentration of heavy metals in plants collected from Shadegan Wetland; and (ii) assess the phase partitioning behavior of selected metals and the ability of macrophytes to accumulate metals from sediments. Metal concentrations in plant tissues were then compared between species and against sediment concentrations to assess the ability of these plants to act as bio-indicators. As also expected, the levels of heavy metals would vary between the different plant parts, with higher concentrations in the root than above-ground organs.
2-Materials and methods
Shadegan Wetland is the largest wetland in southwestern Iran with an area of 537,700 ha and lies at the downstream of the Jarrahi river basin in Khuzestan Province, south-west Iran (Davodi et al., 2011). Kaffashi et al. (2011) reported 17 major plant communities comprised of 110 plant species within the wetland boundary.
In November 2016, twenty plant samples were collected from abundant macrophyte species (Typha latifolia, Halocnemum strobilaceum, Aeluropus lagopoides, Phragmites australis, and Scripus maritimus). Sediment samples were collected at the same time as the plants. In the laboratory, all samples were dried and ground into a fine powder using an agate mortar (El Azhari et al., 2017).
Total concentrations of metals in the plant samples including (Mo, Cu, Pb, Zn, As, Se, Hg, Ni, Co, Cd, Cr, V, Mn, Al, and Fe) were measured using inductively coupled plasma mass spectrometry (ICP-MS) at Acme Analytical Laboratory, Canada. The modified BCR sequential extraction scheme was used for metal fractionation analysis. Trace element concentration in each fraction was determined by inductively coupled plasma-optical emission spectrometry (ICP-OES) at Zarazma Mineral Studies Company (Iran).
Following analyses, values were determined for bioaccumulation factor (BAF) and translocation factor (TF) to assess element mobility in the study species (Chandra et al., 2017). Plants with both factors > 1 are suitable for phytoextraction while, plants with both factors < 1 are ideal for phytostabilization (Buscaroli, 2017). A modified BCR sequential chemical extraction was carried out to identify the distribution of elements (Pb, Zn, Ni, As, Co, Cr, Cu, V, Al, Mo, Mn, and Fe) in different geochemical sediment fractions for four samples. Mobility factor (MF) is commonly used to determine element mobility, which is calculated using the sum of the proportions of acid-extractable, reducible, and oxidizable fractions equation (Li et al., 2013
