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The Las Vegas Wash and Nature Preserve in relation to major tributaries and Lake Mead

The Las Vegas Wash and Nature Preserve in relation to major tributaries and Lake Mead

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There is concern that elevated levels of selenium found in the source water of a newly formed wetland park in Las Vegas, Nevada, may have detrimental effects on local wildlife. In this study, we collected and analyzed water samples monthly for a three year period from the inflow and outflow of the system. We also gathered dominant aquatic plants an...

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... most of them were contaminated with elevated levels of Se ( Presser et al. 1994;Wu 2004). This study concerns a newly constructed 130-acre wetland in the Las Vegas, Nevada metropolitan area. The constructed wetland, called the Clark County Wetlands Park Nature Preserve (NP), is adjacent to the main channel of the Las Vegas Wash in Southern Nevada (Fig. 1). Construction of the Nature Preserve wetland system was completed in April ...
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... Nature Preserve is part of the 2,500 acre Clark County Wetlands Park and is located within the vicinity of the Las Vegas Wash (Fig. 1). The ponds and streams of the NP were designed to be supplied with water primarily from the nearby Monson Drain, a tributary to the Wash. It was known prior to construction that the Monson Drain had Se concentrations of >20 μg/l during some seasons and flow conditions. During the process of performing a National Environmental ...
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... was fairly consistent seasonally, although there was considerable spatial and plant portion variation as has been noted above. Concentrations of Se in the plants varied by tissue, species and season (Tables 1 and 2). For those species and plant tissues that we were able to collect samples in both seasons we were able to make a direct comparison of tissue Se content. ...
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... those species and plant tissues that we were able to collect samples in both seasons we were able to make a direct comparison of tissue Se content. The fall samples generally had concentrations highest in the vegetative portions, followed by the roots and flower segments (Table 1, Fig. 4). The distribution was somewhat different for the spring/summer samples, which typically had the highest concentrations in the roots, followed by vegetative segments and flowers (Table 2, Fig. 5), although this pattern was not entirely consistent (see Bulrush in Fig. 5). ...

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... The content of Se in water at all sampling sites did not exceed the acceptable value of 2 lg Se L À1 at the time of sampling (Lemly, 1993). In the study of Pollard et al. (2007) the content of Se in water from wetland, which indirectly receives discharge of wastewaters, ranged from 9.9 to 24.7 lg Se L À1 . The values in polluted waters in the Arkansas River basin ranged from 1 to 240 lg Se L À1 (Canton and Van Derveer, 1997). ...
... The reason for that may be in its growth form, since this plant can take up elements through roots as well as through leaves, while the root uptake can be less effective in submerged plants. In the study of Pollard et al. (2007) the content of Se in the Scirpus californicus was 1.17, in Typha spp. 2.81 and in Scirpus maritimus 1.51 lg Se g À1 . ...
... We also observed some seasonal variations in the content of Se that are different between species as well as streams. In contrast, Pollard et al. (2007) did not find any seasonal variations. We can observe the trend of higher Se content in macrophytes in October and April (Fig. 4). ...
... Although Se uptake in A. repens was high, the bioconcentration factor was below 1 (data not shown). In a study by Pollard et al. (2007), the tissues of aquatic plants growing in a swamp with the concentration of 20 g Se L −1 at the inflow, contained lower amounts of Se, with values reaching 1.16 g Se g −1 in Scirpus californicus and 4.70 g Se g −1 in Najas marina. In Ruppia maritima exposed to concentrations of 1 mg Se(IV) L −1 Se, the final content after 21 days was 100 g Se g −1 (Bailey et al., 1995). ...
Article
Studies are scarce regarding the physiological effects of selenium treatment on antioxidant capacity of plants. In the presented in vitro experiment, Apium repens was used to investigate its ability to absorb Se(IV) at different concentrations (0.01, 0.1, 1, 10 and 50 mg L⁻¹) and its physiological response to treatment. These plants possessed a high affinity to take up Se(IV), since Se concentration measured in plants reached 730 μg g⁻¹ DM in 50 mg L⁻¹ treated plants. Lower Se(IV) concentrations (0.01–1 mg L⁻¹) promoted growth, while higher Se(IV) concentrations (10 and 50 mg L⁻¹) affected it negatively. The photochemical efficiency decreased significantly in plants treated with higher Se(IV) concentrations compared to control plants. In the roots, total cysteine and glutathione content increased gradually from 0.01 to 10 mg L⁻¹ Se treatment, when compared to the control. Enhanced total glutathione levels were also determined in the above ground parts when the plants were treated with lower Se(IV) concentrations (0.01–1 mg L⁻¹). In both roots and above-ground parts, 50 mg L⁻¹ Se(IV) treatment caused a significant degradation of total cysteine and glutathione, which was accompanied by a significantly larger oxidized glutathione pool. By applying five different concentrations of Se(IV), it was possible to identify a threshold Se content for A. repens, above which the nature of the effects induced changes from antioxidant to pro-oxidant.
... The amount of Se in the tissues of water plants growing in a swamp containing 20 μg Se L −1 , contained 1.16 μg Se g −1 in Scirpus californicus and 4.70 μg Se g −1 in Najas marina (Pollard et al. 2007). In Ruppia maritima exposed to concentrations around 6 mg Se L −1 , the content of Se was 200 μg Se g −1 (Bailey et al. 1995). ...
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In the presented in vitro experiment, the effect of selenite treatment (0.01, 0.1, 1, 10 and 50 mg L−1 Se(IV)) on Berula erecta was investigated with respect to growth, photochemical efficiency, photosynthetic pigments, anthocyanins and low molecular weight thiols. Lower Se(IV) concentrations (0.01, 0.1 and 1 mg L−1) promoted growth, while higher Se(IV) concentrations (10 and 50 mg L−1) negatively affected it. The photochemical efficiency of photosystem II decreased significantly in plants treated with higher Se(IV) concentrations, compared to that in the control plants. The content of pigments decreased in all the Se(IV) treatments. Both cysteine and glutathione showed alterations in their content and redox state depending on the Se concentration. By evaluating the glutathione/cysteine system and their redox, it was possible to identify a threshold Se content (1-mg Se(IV) L−1 treatment), above which the nature of the effects induced changes from antioxidant to pro-oxidant.
... Se concentrations in the Žerovniščica stream from 0.07 to 0.23 ng mL −1 , and in the Pšata stream from 0.03 to 0.15 ng mL −1 confirmed the range from 0.01 to 0.5 µg L −1 for typical concentrations of Se in freshwaters [51]. Nevertheless, these values of Se were lower than those in a study from a wetland which indirectly receives discharge of wastewaters, having Se concentrations from 9.9 to 24.7 µg L −1 [52]. Cd concentrations in water ranged from < 0.0 to 0.75 ng mL −1 with the highest concentration in the Ižica stream during the year 2010 and at the reference site in the year 2011. ...
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... In other studies, macrophytes accumulated lower amount of Se from water containing 20 g Se L −1 – Chara spp. (Lin et al., 2002) and Scirpus californicus accumulated 1 g Se g −1 and Najas marina 5 g Se g −1 (Pollard et al., 2007). Mechora et al. (2011 found out that the content of Se in M. spicatum and C. demersum, exposed to 20 g Se(VI) L −1 , contained only around 0.7 g Se g −1 . ...
... In other studies, macrophytes accumulated lower amount of Se from water containing 20 g Se L −1 – Chara spp. (Lin et al., 2002) and Scirpus californicus accumulated 1 g Se g −1 and Najas marina 5 g Se g −1 (Pollard et al., 2007). Mechora et al. (2011 found out that the content of Se in M. spicatum and C. demersum, exposed to 20 g Se(VI) L −1 , contained only around 0.7 g Se g −1 . ...
... In other studies, macrophytes accumulated lower amount of Se from water containing 20 g Se L −1 – Chara spp. (Lin et al., 2002) and Scirpus californicus accumulated 1 g Se g −1 and Najas marina 5 g Se g −1 (Pollard et al., 2007). Mechora et al. (2011 found out that the content of Se in M. spicatum and C. demersum, exposed to 20 g Se(VI) L −1 , contained only around 0.7 g Se g −1 . ...
... In other studies, macrophytes accumulated lower amount of Se from water containing 20 g Se L −1 – Chara spp. (Lin et al., 2002) and Scirpus californicus accumulated 1 g Se g −1 and Najas marina 5 g Se g −1 (Pollard et al., 2007). Mechora et al. (2011 found out that the content of Se in M. spicatum and C. demersum, exposed to 20 g Se(VI) L −1 , contained only around 0.7 g Se g −1 . ...
... In other studies, macrophytes accumulated lower amount of Se from water containing 20 g Se L −1 – Chara spp. (Lin et al., 2002) and Scirpus californicus accumulated 1 g Se g −1 and Najas marina 5 g Se g −1 (Pollard et al., 2007). Mechora et al. (2011 found out that the content of Se in M. spicatum and C. demersum, exposed to 20 g Se(VI) L −1 , contained only around 0.7 g Se g −1 . ...
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... The content of Se in water at all sampling sites did not exceed the acceptable value of 2 lg Se L À1 at the time of sampling (Lemly, 1993). In the study of Pollard et al. (2007) the content of Se in water from wetland, which indirectly receives discharge of wastewaters, ranged from 9.9 to 24.7 lg Se L À1 . The values in polluted waters in the Arkansas River basin ranged from 1 to 240 lg Se L À1 (Canton and Van Derveer, 1997). ...
... The reason for that may be in its growth form, since this plant can take up elements through roots as well as through leaves, while the root uptake can be less effective in submerged plants. In the study of Pollard et al. (2007) the content of Se in the Scirpus californicus was 1.17, in Typha spp. 2.81 and in Scirpus maritimus 1.51 lg Se g À1 . ...
... We also observed some seasonal variations in the content of Se that are different between species as well as streams. In contrast, Pollard et al. (2007) did not find any seasonal variations. We can observe the trend of higher Se content in macrophytes in October and April (Fig. 4). ...
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