6 research outputs found
Development of a Constructed Wetland Water Treatment System for Selenium Removal: Incorporation of an Algal Treatment Component
On
the basis of the fact that algae have the ability to volatilize
substantial quantities of selenium (Se), we investigated the concept
of including an algal pretreatment unit into a constructed wetland
system for the removal of Se from river water entering the Salton
Sea. Of six different algal strains tested, the most effective in
terms of Se volatilization and Se removal from the water column was
a Chlorella vulgaris strain (designated
Cv). Cv removed 96% of Se (supplied as selenate) from the microcosm
water column within 72 h, with up to 61% being removed by volatilization
to the atmosphere. X-ray absorption spectroscopy revealed that the
major forms of Se likely to be accumulated in an algal–wetland
system are selenomethionine, a precursor of volatile Se formation,
and elemental Se. Our results suggest that the inclusion of an algal
pretreatment unit within a constructed wetland water treatment system
should not only enhance the efficiency of Se removal but also significantly
reduce the risk of the buildup of ecotoxic forms of Se by promoting
the biological volatilization of Se
Multispecies Biofilms Transform Selenium Oxyanions into Elemental Selenium Particles: Studies Using Combined Synchrotron X‑ray Fluorescence Imaging and Scanning Transmission X‑ray Microscopy
Selenium (Se) is an element of growing
environmental concern, because
low aqueous concentrations can lead to biomagnification through the
aquatic food web. Biofilms, naturally occurring microbial consortia,
play numerous important roles in the environment, especially in biogeochemical
cycling of toxic elements in aquatic systems. The complexity of naturally
forming multispecies biofilms presents challenges for characterization
because conventional microscopic techniques require chemical and physical
modifications of the sample. Here, multispecies biofilms biotransforming
selenium oxyanions were characterized using X-ray fluorescence imaging
(XFI) and scanning transmission X-ray microscopy (STXM). These complementary
synchrotron techniques required minimal sample preparation and were
applied correlatively to the same biofilm areas. Sub-micrometer XFI
showed distributions of Se and endogenous metals, while Se K-edge
X-ray absorption spectroscopy indicated the presence of elemental
Se (Se<sup>0</sup>). Nanoscale carbon K-edge STXM revealed the distributions
of microbial cells, extracellular polymeric substances (EPS), and
lipids using the protein, saccharide, and lipid signatures, respectively,
together with highly localized Se<sup>0</sup> using the Se L<sub>III</sub> edge. Transmission electron microscopy showed the electron-dense
particle diameter to be 50–700 nm, suggesting Se<sup>0</sup> nanoparticles. The intimate association of Se<sup>0</sup> particles
with protein and polysaccharide biofilm components has implications
for the bioavailability of selenium in the environment
Quantification, Localization, and Speciation of Selenium in Seeds of Canola and Two Mustard Species Compared to Seed-Meals Produced by Hydraulic Press
<i>Brassica</i> plants accumulate selenium
(Se) especially
in seeds when grown in soils laden with Se. We report a chemical analysis
of Se in <i>Brassica</i> seeds (canola, Indian mustard,
and white mustard) and in their hydraulically pressed seed meals,
which are used as a Se supplement in livestock animal feeds. Complementary
techniques were used to measure total Se concentrations, to map the
localization of Se, and to quantify different Se forms. Seeds and
hydraulically pressed seed meals contained an average of 1.8 and 2.0
μg Se g<sup>–1</sup> DW, respectively. Selenium was primarily
located in cotyledons and roots of seed embryos. Microfocused Se K-edge
XANES and bulk XANES showed that seeds contained 90% of Se as C–Se–C
forms. Hydraulically pressing seeds for oil caused changes in the
forms of Se as follows: 40–55% C–Se–C forms,
33–42% selenocystine, 5–12% selenocysteine, and 11–14%
trimethylselenonium ion. Aqueous extracts of seed and seed meals were
also analyzed by SAX-HPLC/ICPMS and found to contain mainly the C–Se–C
form SeMet, but also another C–Se–C form MeSeCys, which
is of dietary pharmacological interest for cancer inhibition. In addition,
SAX-HPLC/ICPMS also detected selenocystine and selenocysteine, further
confirming the results obtained by XANES analyses
Selenium Biotransformations in an Engineered Aquatic Ecosystem for Bioremediation of Agricultural Wastewater via Brine Shrimp Production
An
engineered aquatic ecosystem was specifically designed to bioremediate
selenium (Se), occurring as oxidized inorganic selenate from hypersalinized
agricultural drainage water while producing brine shrimp enriched
in organic Se and omega-3 and omega-6 fatty acids for use in value
added nutraceutical food supplements. Selenate was successfully bioremediated
by microalgal metabolism into organic Se (seleno-amino acids) and
partially removed via gaseous volatile Se formation. Furthermore,
filter-feeding brine shrimp that accumulated this organic Se were
removed by net harvest. Thriving in this engineered pond system, brine
shrimp (Artemia franciscana Kellogg)
and brine fly (Ephydridae sp.) have
major ecological relevance as important food sources for large populations
of waterfowl, breeding, and migratory shore birds. This aquatic ecosystem
was an ideal model for study because it mimics trophic interactions
in a Se polluted wetland. Inorganic selenate in drainage water was
metabolized differently in microalgae, bacteria, and diatoms where
it was accumulated and reduced into various inorganic forms (selenite,
selenide, or elemental Se) or partially incorporated into organic
Se mainly as selenomethionine. Brine shrimp and brine fly larva then
bioaccumulated Se from ingesting aquatic microorganisms and further
metabolized Se predominately into organic Se forms. Importantly, adult
brine flies, which hatched from aquatic larva, bioaccumulated the
highest Se concentrations of all organisms tested
Selenium Biotransformations in an Engineered Aquatic Ecosystem for Bioremediation of Agricultural Wastewater via Brine Shrimp Production
An
engineered aquatic ecosystem was specifically designed to bioremediate
selenium (Se), occurring as oxidized inorganic selenate from hypersalinized
agricultural drainage water while producing brine shrimp enriched
in organic Se and omega-3 and omega-6 fatty acids for use in value
added nutraceutical food supplements. Selenate was successfully bioremediated
by microalgal metabolism into organic Se (seleno-amino acids) and
partially removed via gaseous volatile Se formation. Furthermore,
filter-feeding brine shrimp that accumulated this organic Se were
removed by net harvest. Thriving in this engineered pond system, brine
shrimp (Artemia franciscana Kellogg)
and brine fly (Ephydridae sp.) have
major ecological relevance as important food sources for large populations
of waterfowl, breeding, and migratory shore birds. This aquatic ecosystem
was an ideal model for study because it mimics trophic interactions
in a Se polluted wetland. Inorganic selenate in drainage water was
metabolized differently in microalgae, bacteria, and diatoms where
it was accumulated and reduced into various inorganic forms (selenite,
selenide, or elemental Se) or partially incorporated into organic
Se mainly as selenomethionine. Brine shrimp and brine fly larva then
bioaccumulated Se from ingesting aquatic microorganisms and further
metabolized Se predominately into organic Se forms. Importantly, adult
brine flies, which hatched from aquatic larva, bioaccumulated the
highest Se concentrations of all organisms tested
Selenium Biotransformations in an Engineered Aquatic Ecosystem for Bioremediation of Agricultural Wastewater via Brine Shrimp Production
An
engineered aquatic ecosystem was specifically designed to bioremediate
selenium (Se), occurring as oxidized inorganic selenate from hypersalinized
agricultural drainage water while producing brine shrimp enriched
in organic Se and omega-3 and omega-6 fatty acids for use in value
added nutraceutical food supplements. Selenate was successfully bioremediated
by microalgal metabolism into organic Se (seleno-amino acids) and
partially removed via gaseous volatile Se formation. Furthermore,
filter-feeding brine shrimp that accumulated this organic Se were
removed by net harvest. Thriving in this engineered pond system, brine
shrimp (Artemia franciscana Kellogg)
and brine fly (Ephydridae sp.) have
major ecological relevance as important food sources for large populations
of waterfowl, breeding, and migratory shore birds. This aquatic ecosystem
was an ideal model for study because it mimics trophic interactions
in a Se polluted wetland. Inorganic selenate in drainage water was
metabolized differently in microalgae, bacteria, and diatoms where
it was accumulated and reduced into various inorganic forms (selenite,
selenide, or elemental Se) or partially incorporated into organic
Se mainly as selenomethionine. Brine shrimp and brine fly larva then
bioaccumulated Se from ingesting aquatic microorganisms and further
metabolized Se predominately into organic Se forms. Importantly, adult
brine flies, which hatched from aquatic larva, bioaccumulated the
highest Se concentrations of all organisms tested