Assessment Tools for Urban Catchments: Developing Biological Indicators Based on Benthic Macroinvertebrates1

Abstract: Biological indicators, particularly benthic macroinvertebrates, are widely used and effective measures of the impact of urbanization on stream ecosystems. A multimetric biological index of urbanization was developed using a large benthic macroinvertebrate dataset (n = 1,835) from the Baltimore, Maryland, metropolitan area and then validated with datasets from Cleveland, Ohio (n = 79); San Jose, California (n = 85); and a different subset of the Baltimore data (n = 85). The biological metrics used to develop the multimetric index were selected using several criteria and were required to represent ecological attributes of macroinvertebrate assemblages including taxonomic composition and richness (number of taxa in the insect orders of Ephemeroptera, Plecoptera, and Trichoptera), functional feeding group (number of taxa designated as filterers), and habit (percent of individuals which cling to the substrate). Quantile regression was used to select metrics and characterize the relationship between the final biological index and an urban gradient (composed of population density, road density, and urban land use). Although more complex biological indices exist, this simplified multimetric index showed a consistent relationship between biological indicators and urban conditions (as measured by quantile regression) in three climatic regions of the United States and can serve as an assessment tool for environmental managers to prioritize urban stream sites for restoration and protection.     

Structural characterization and thermal stabilities of the isomers of the brominated flame retardant 1,2,5,6-tetrabromocyclooctane (TBCO)

1,2,5,6-Tetrabromocyclooctane (TBCO) is a commercial brominated flame retardant that is employed mainly as an additive in textiles, paints and plastics. Very little is known about its presence or behavior in the environment or its analysis. TBCO can exist as two diastereomers, the stereochemistries of which have not been previously reported. We have named the first eluting isomer, under HPLC conditions, as alpha-TBCO (α-TBCO) and the later eluting isomer as beta-TBCO (β-TBCO) when using an Acquity UPLC BEH C₁₈ column with methanol/acetonitrile/water as the mobile phase. The structural elucidation of these two isomers was accomplished by ¹H NMR spectroscopy, GC/MS, LC/MS and X-ray structure determinations. α-TBCO is (1R,2R,5S,6S)-1,2,5,6-tetrabromocyclooctane and β-TBCO is rac-(1R,2R,5R,6R)-1,2,5,6-tetrabromocyclooctane. As with some other brominated cycloaliphatic compounds, TBCO is thermally labile and the isomers easily interconvert. A thermal equilibrium mixture of α- and β-TBCO consists of approximately 15% and 85% of these isomers, respectively. Separation of the two diastereomers, with minimal thermal interconversion between them, is achievable by careful selection of GC-capillary column length and injector temperature. LC/MS analyses of TBCO also presents an analytical challenge due to poor resolution of the isomers on chromatographic stationary phases, and weak intensity of molecular ions (or major fragment ions) when using LC-ESI/MS. Only bromide ions were seen in the mass spectra. APCI and APPI also failed to produce the molecular ion with sufficient intensity for identification.     

Nitrate Dynamics in Two Streams Impacted by Wastewater Treatment Plant Discharge: Point Sources or Sinks?

We examined nitrate processing in headwater stream reaches downstream of two wastewater treatment plant outfalls during low streamflow. Our objectives were to quantify nitrate mass flux before and after effluent discharge and to use field and laboratory techniques to assess the mechanism of nitrate uptake. Microcosm experiments were utilized to determine the location of nitrate processing, and molecular biomarkers were used to detect and quantify microbial denitrification. At one site, downstream nitrate mass flux was significantly (p = 0.01) lower than sum of upstream and wastewater effluent fluxes, indicating rapid stream assimilation of incoming nitrate in the vicinity of the point source. Microcosm experiments supported the theory that nitrate processing occurs in sediments. Molecular assays for denitrifcation‐associated functional genes nosZ, nirS, and nirK, provided evidence that effluent contained enriched denitrifying communities relative to ambient stream water. Nitrate loss at the site with greater uptake was correlated with sulfate loss (p < 0.01; r² = 0.86), suggesting a possible link between sulfate reducing bacteria and denitrifying bacterial communities. Results suggest there is an opportunity to better understand nitrate dynamics in cases where point sources may act as point sinks under specific sets of conditions.     

Stability considerations of aspartame in the direct analysis of artificial sweeteners in water samples using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS)

A HPLC-MS/MS method is presented for the simultaneous determination of frequently used artificial sweeteners (ASs) and the main metabolite of aspartame (ASP), diketopiperazine (DKP), in environmental water samples using the direct-injection (DI) technique, thereby achieving limits of quantification (LOQ) of 10 ng L⁻¹. For a reliable quantification of ASP pH should be adjusted to 4.3 to prevent formation of the metabolite. Acesulfame (ACE), saccharin (SAC), cyclamate (CYC) and sucralose (SUC) were ubiquitously found in water samples. Highest concentrations up to 61 μg L⁻¹ of ACE were found in wastewater effluents, followed by surface water with concentrations up to 7 μg L⁻¹, lakes up to 600 ng L⁻¹ and groundwater and tap water up to 70 ng L⁻¹. The metabolite DKP was only detected in wastewater up to 200 ng L⁻¹ and at low detection frequencies.     

Effect of pH on surface characteristics of switchgrass-derived biochars produced by fast pyrolysis

Surface properties of switchgrass-derived biochars produced at fast pyrolysis temperatures of 450, 600 and 800 °C were characterized at different solution pHs in order to determine the structural and chemical changes of artificially-weathered biochars when incorporated into soil. As biochars were acidified from pH 7 to 3, crystalline minerals dissolved slowly releasing nutrients; however, residual minerals were still detected in biochars produced at higher pyrolysis temperatures after pH treatment. Moreover, the amount of exchangeable bases and other inorganic compounds released from the biochars increased when pH decreased. As minerals dissolved from the biochars, total surface area and pore volume were found to increase. Surface functional groups and water vapor adsorption capacity at 0.8 P/P_o also increased, whereas the potential CEC of biochars decreased due to the replacement of exchangeable sites by hydrogen ion. Therefore, during the aging process, it is predicted that soil-incorporated biochars will slowly release nutrients with changes in surface functionality and porosity, which are expected to enhance water holding capacity of soil and provide a beneficial habitat for microbial colonization.     

Internalization of SiO2 nanoparticles by alveolar macrophages and lung epithelial cells and its modulation by the lung surfactant substitute Curosurf®

Because of an increasing exposure to environmental and occupational nanoparticles (NPs), the potential risk of these materials for human health should be better assessed. Since one of the main routes of entry of NPs is via the lungs, it is of paramount importance to further characterize their impact on the respiratory system. Here, we have studied the uptake of fluorescently labeled SiO₂ NPs (50 and 100 nm) by epithelial cells (NCI-H292) and alveolar macrophages (MHS) in the presence or absence of pulmonary surfactant. The quantification of NP uptake was performed by measuring cell-associated fluorescence using flow cytometry and spectrometric techniques in order to identify the most suitable methodology. Internalization was shown to be time and dose dependent, and differences in terms of uptake were noted between epithelial cells and macrophages. In the light of our observations, we conclude that flow cytometry is a more reliable technique for the study of NP internalization, and importantly, that the hydrophobic fraction of lung surfactant is critical for downregulating NP uptake in both cell types.     

Differences in response of two model estuarine crustaceans after lethal and sublethal exposures to chlorpyrifos

This study assessed the in vitro and in vivo effects of an acetylcholinesterase enzyme inhibitor (chlorpyrifos) in two estuarine crustaceans: grass shrimp (Palaemonetes pugio) and mysid (Americamysis bahia). The differences in response were quantified after lethal and sublethal exposures to chlorpyrifos and in vitro assays with chlorpyrifos-oxon. Results from the in vitro experiments indicated that the target enzyme, acetylcholinesterase (AChE), in the two species was similar in sensitivity to chlorpyrifos inhibition with IC50s of 0.98 nM and 0.89 nM for grass shrimp and mysids, respectively. In vivo experiments showed that mysids were significantly more sensitive to chlorpyrifos-induced AChE inhibition after 24 h of exposure. The in vivo EC50s for AChE inhibition were 1.23 μg L^?1 for grass shrimp and 0.027 μg L^?1 for mysids.

Median lethal concentrations (24h LC50 values) were 1.06 μg L^?1 for grass shrimp and 0.068 μg L^?1 for mysids. The results suggest that differences in the response of these two crustaceans are likely related to differences in uptake and metabolism rather than target site sensitivity.     

Remote estimation of phycocyanin (PC) for inland waters coupled with YSI PC fluorescence probe

Nuisance cyanobacterial blooms degrade water resources through accelerated eutrophication, odor generation, and production of toxins that cause adverse effects on human health. Quick and effective methods for detecting cyanobacterial abundance in drinking water supplies are urgently needed to compliment conventional laboratory methods, which are costly and time consuming. Hyperspectral remote sensing can be an effective approach for rapid assessment of cyanobacterial blooms. Samples (n?=?250) were collected from five drinking water sources in central Indiana (CIN), USA, and South Australia (SA), which experience nuisance cyanobacterial blooms. In situ hyperspectral data were used to develop models by relating spectral signal with handheld fluorescence probe (YSI 6600 XLM-SV) measured phycocyanin (PC in cell/ml), a proxy pigment unique for indicating the presence of cyanobacteria. Three-band model (TBM), which is effective for chlorophyll-a estimates, was tuned to quantify cyanobacteria coupled with the PC probe measured cyanobacteria. As a comparison, two band model proposed by Simis et al. (Limnol Oceanogr, 50(11): 237–245, 2005; denoted as SM05) was paralleled to evaluate TBM model performance. Our observation revealed a high correlation between measured and estimated PC for SA dataset (R ²?=?0.96; range: 534–20,200 cell/ml) and CIN dataset (R ²?=?0.88; range: 1,300–44,500 cell/ml). The potential of this modeling approach for imagery data were assessed by simulated ESA/Centinel3/OLCI spectra, which also resulted in satisfactory performance with the TBM for both SA dataset (RMSE %?=?26.12) and CIN dataset (RMSE %?=?34.49). Close relationship between probe-measured PC and laboratory measured cyanobacteria biovolume was observed (R ²?=?0.93, p?<?0.0001) for the CIN dataset, indicating a stable performance for PC probe. Based on our observation, field spectroscopic measurement coupled with PC probe measurements can provide quantitative cyanobacterial bloom information from both relatively static and flowing inland waters. Hence, it has promising implications for water resource managers to obtain information for early warning detection of cyanobacterial blooms through the close association between probe measured PC values and cyanobacterial biovolume via remote sensing modeling.     

Characterization of Degradation of Cotton Cellulosic Fibers Through Near Infrared Spectroscopy

Near infrared (NIR) spectroscopy has been found to be one of the most important characterization tools for polymeric materials based on comparatively simple NIR-favorable chemical groups (i.e., C–H, O–H, and N–H). This paper focuses on characterizing degradation of cotton cellulosic fibers in a historical textile—‘Curtain Dress’ in the famous movie Gone With the Wind through NIR spectroscopy, and investigating morphological and molecular changes associated with appearance change such as discolorations in the same cotton textiles. In this study, we did on-site testing on the ‘Curtain Dress’ with the Brimrose Luminar 5030 NIR-analyzer and analyzed the NIR spectroscopy results at eight locations where different degrees of discoloration occurred on the dress. The study identified the wavelength bands according to NIR spectral absorbancies of the typical functional groups in cellulosic fibers such as C–H, C–O and O–H stretches, compared the absorbance intensities at three main wavelengths, and investigated discoloration in different areas via principal component analysis. The combination factor scores of the 1st and 2nd principal components, which accounted for 99.09 % variance of vibrations within various groups in a molecule measured through NIR, reflected effectively morphological changes in the fiber’s molecular structure and degrees of discolorations.     

Synthesis of the two minor isomers, delta- and epsilon-1,2,5,6,9,10-hexabromocyclododecane, present in commercial hexabromocyclododecane

Hexabromocyclododecane (HBCD) is prepared commercially by bromination of cis,trans,trans-cyclododecatriene (ctt-CDT) and widely used as a flame retardant, particularly in polystyrene foams. Commercial HBCD consists largely of three diastereomers, alpha-, beta-, and gamma-HBCD, the structures of which have been known for many years. Recently, the presence in the mixture of small amounts of two minor diastereomers, delta- and epsilon-HBCD, has been reported. Bearing in mind the manner in which commercial HBCD is generated, it was anticipated that these components are probably formed by bromination of trans,trans,trans-cyclododecatriene (ttt-CDT), a common contaminant in commercial ctt-CDT. Indeed, when a sample of ttt-CDT was brominated it gave two products, the NMR spectra and LC/MS and GC/MS behaviour of which confirmed that they are identical to the minor components, delta- and epsilon-HBCD, present in commercial HBCD.