Range Of Water Quality Conditions Research Articles

Parts per trillion detection of heavy metals in as-is tap water using carbon nanotube microelectrodes

Heavy metal contamination of drinking water is a major global issue. Research reports across the globe show contamination of heavy metals higher than the set standards of the World Health Organization (WHO) and US Environmental Protection Agency (EPA). To our knowledge, no electrochemical sensor for heavy metals with parts per trillion (PPT) limits of detection (LOD) in as-is tap water has been reported or developed. Here, we report a microelectrode that consists of six highly densified carbon nanotube fiber (HD-CNTf) cross sections called rods (diameter ∼69 μm and length ∼40 μm) in a single platform for the ultra-sensitive detection of heavy metals in tap water and simulated drinking water. The HD-CNTf rods microelectrode was evaluated for the individual and simultaneous determination of trace level of heavy metal ions i.e. Cu2+, Pb2+ and Cd2+ in Cincinnati tap water (without supporting electrolyte) and simulated drinking water using square wave stripping voltammetry (SWSV). The microsensor exhibited a broad linear detection range with an excellent limit of detection for individual Cu2+, Pb2+ and Cd2+ of 6.0 nM, (376 ppt), 0.45 nM (92 ppt) and 0.24 nM (27 ppt) in tap water and 0.32 nM (20 ppt), 0.26 nM (55 ppt) and 0.25 nM (28 ppt) in simulated drinking water, respectively. The microelectrode was shown to detect Pb2+ ions well below the WHO and EPA limits in a broad range of water quality conditions reported for temperature and conductivity in the range of 5 °C–45 °C and 55 to 600 μS/cm, respectively.

Interpretation of the formation of unstable halogen-containing disinfection by-products based on the differential absorbance spectroscopy approach

Concentrations of several toxic disinfection by-products (DBP), notably haloacetonitriles (e.g., trichloroacetonitrile, TCAN) and haloketones (e.g., di- and trichloropropanone, DCPN and TCPN, respectively) are affected by chlorination conditions and the inherent instability of these DBPs. In this study, effects of temperature, chlorine dose and reaction time on the formation of TCAN, DCPN and TCPN were interpreted using the approach of differential absorbance spectroscopy. Experimental data obtained for a wide range of water quality conditions demonstrate that in some cases the concentrations of some of the unstable DBPs increased rather than decreased at low temperatures and realistically long contact times. Despite the presence of pronounced changes of the kinetics of generation and degradation of these DBPs at varying temperatures and chlorine doses, their concentrations were strongly correlated with the concurrent changes of spectroscopic properties of DOM quantified via differential absorbance measurements at 272 nm (ΔA272). The maximum values of TCAN, DCPN and TCPN concentrations observed for the chlorination of eight different surface waters occur at the relative decreases of absorbance at 272 nm (defined as RΔA272) values of ca. 0.32 (±0.03), 0.24 (±0.05), and 0.42 (±0.03), respectively. The activation energies of degradation reactions of unstable DBPs were examined and the results indicate that TCAN and TCPN are caused by their hydrolysis with OH− while the degradation of DCPN is mainly caused by halogenation reaction with HOCl. These results in this study may be important for controlling the formation of unstable DBPs and further optimization of drinking water treatment.

External Standard Calibration Method To Measure the Hydroxyl Radical Scavenging Capacity of Water Samples

The hydroxyl radical (•OH) scavenging capacity is a useful parameter for the design and operation of an advanced oxidation process (AOP) in water treatment. The scavenging capacity may change with time, and it would be useful to continuously measure this change to be able to optimize AOP doses. In this study, we first reviewed current methods for scavenging capacity measurement to identify strengths and weaknesses of each method. This information helped guide the design of an external calibration method to allow straightforward laboratory and field measurement of •OH scavenging capacity. The method used low-pressure UV/H2O2 as the •OH generation system, methylene blue (MB) as the probe compound, and isopropyl alcohol (IPA) as the standard. By monitoring, offline, the color decay of MB in a series of IPA solutions with different scavenging capacity, a calibration curve was established between the color decay rate and the scavenging capacity. The measured color decay in real water samples can then be used with this external calibration to estimate their scavenging capacity. Work was undertaken to ensure that the process would be robust under a wide range of water quality conditions. Parallel tests using this method compared with the benchmark methods confirmed its robustness and accuracy.

Polarographic determination of benzotriazoles and their sorption behavior on granular activated carbon

Because of their persistence and unknown environmental risks, the widespread occurrence of benzotriazoles has been gaining increased attention. A highly selective, rapid, and economical method—differential pulse polarography—was developed and applied for the quantitation of commercially significant methylbenzotriazole isomers in environmental samples of relevance to wastewater treatment, non-point source pollution and acid mine drainage. Differential pulse polarography was able to accurately measure aqueous methylbenzotriazole, as well as the methylbenzotriazole fraction that sorbed to activated sludge biomass, subsurface sediments, and activated carbon. Granular activated carbons were characterized for their ability to sequester benzotriazoles from aqueous environments using differential pulse polarography and high-performance liquid chromatography. Langmuir, Freundlich, Toth and Redlich–Peterson isotherm models were compared for their ability to describe benzotriazole partitioning to granular activated carbons under a relatively wide range of water quality conditions. Sorption behavior of 5-methylbenzotriazole was best-described by a Redlich–Peterson isotherm model, where water quality parameters were varied in the following range pH (1 < pH < 5), temperature (5 °C < T < 25 °C), and in the following ranges of an ionic strength (0.005 < M < 0.02). 4- and 5-methylbenzotriazole concentrations determined by differential pulse polarography correlated well with those concentrations measured by high-performance liquid chromatography through an environmentally significant range (0.4–30 mg/L). Using a static mercury drop electrode, the method detection limit was 50 and 40 μg/L for 4- and 5-methylbenzotriazole, respectively. The developed DPP polarographic method was found to be simple, rapid, and it can be applied directly to environmental samples without filtration, extraction, and centrifugation.

Demonstration of Survival, Growth, and Reproduction of Gulf Killifish in Freshwater Ponds

AbstractThe Gulf Killifish Fundulus grandis, a popular baitfish species inhabiting estuaries in the northern Gulf of Mexico, has potential as an aquaculture species, particularly if it can be produced in low‐salinity or freshwater ponds. Because growth and survival in freshwater ponds are not known, two size‐classes were examined over a 16‐week period. Initial mean stocking weights and densities were 0.47 g/fish and 26,500 fish/ha for the smaller size‐group, which was stocked into three 0.04‐ha ponds, and 6.12 g/fish and 20,450 fish/ha for the larger size‐group, which was stocked into two 0.04‐ha ponds. Growth and survival were similar between size‐classes: mean final weight and mean survival were 7.88 g/fish and 54.3%, respectively, for the smaller size‐group, and 13.90 g/fish and 43.1% for the larger size‐group. Mean weight gain was very similar between size‐groups (small: 7.41 g; large: 7.78 g); steady growth was observed from June until mid‐September, whereas little growth and declines in condition factor were observed from mid‐September to mid‐October, corresponding with decreases in water temperature. Gulf Killifish were resilient to a wide range of water quality conditions in freshwater ponds and reached market sizes of 3 g at about 4 weeks and 5 g by 8 weeks.

Ultrafiltration with self-generated RO concentrate pulse backwash in a novel integrated seawater desalination UF-RO system

Ultrafiltration as a pretreatment for RO feedwater with enhanced UF backwash, which combines continuous with pulse backwash, was investigated in a novel UF-RO process integration. Direct supply of RO concentrate to the UF module served for UF backwash which was further enhanced with pulse backwash generated using bladder-type hydraulic accumulators. Model analysis of the hydraulic accumulator operation, which was validated via a series of field experiments, demonstrated a capability for accumulator charging directly from the RO concentrate stream within a period of 30–40s. Moreover, pulse backwash over a short period (~5s) which was added to the continuous UF backwash (directly from the RO brine stream), enabled peak UF backwash flux up to a factor of 4.2–4.6 higher than the normal filtration flux. The above mode of UF operation with multiple consecutive backwash pulses was more effective than with a single pulse, while inline coagulation further increased the UF performance. Relatively long-term field operation (over eight days where) of the UF-RO system with self-adaptive triggering of UF backwash, whereby the number of consecutive pulses increased when a higher membrane fouling resistance was encountered, was highly effective in enabling stable UF operation over a wider range of water quality conditions and without the need for chemical cleaning. These encouraging results suggest that direct UF-RO integration with enhanced pulse UF backwash is an effective approach for dead-end UF filtration without sacrificing water productivity.

10-Day survival of Hyalella azteca as a function of water quality parameters

Estuarine systems are among the most impacted ecosystems due to anthropogenic contaminants; however, they present unique challenges to toxicity testing with regard to varying water quality parameters. The euryhaline amphipod species, Hyalella azteca, is widely used in toxicity testing and well suited for testing estuarine water samples. Nevertheless, the influence of relevant water quality parameters on test endpoints must be quantified in order to efficiently use this species for routine monitoring. Here, we studied the influence of five water quality parameters: electrical conductivity, pH, un-ionized ammonia, dissolved oxygen and temperature, on H. azteca survival in a water column toxicity test. A model was developed to quantify and predict the independent and interacting effects of water quality variables on 10-day survival. The model allows simultaneous assessment of multiple potential predictors recorded during the tests. Data used for modeling came from 1089 tests performed on ambient water samples over a period of three years (2006–2008). The final model reflects significant effects of predictors and their two-way interactions. The effect of each level of all predictors on survival probability of H. azteca was examined by comparing levels of each predictor at a time, while holding all others at their lowest (reference) level. This study showed that predictors of survival in water column tests should not be evaluated in isolation in the interpretation of H. azteca water column tests. Our model provides a useful tool to predict expected control survival based on relevant water quality parameters, and thus enables the use of H. azteca tests for toxicity monitoring in estuaries with a wide range of water quality conditions.

Long-term trends and causal factors associated with Microcystis abundance and toxicity in San Francisco Estuary and implications for climate change impacts

The impacts of climate change on Micro- cystis blooms in San Francisco Estuary are uncertain because factors associated with the abundance and distribution of Microcystis blooms since their incep- tion in 1999 are poorly understood. Discrete and continuous data collected between 2004 and 2008 were used to assess what factors controlled bloom initiation and persistence, if there was an impact of the bloom on mesozooplankton abundance and toxicity or dissolved organic carbon concentration, and how these might vary with climate change. Microcystis abun- dance was greater in dry years than wet years and both total microcystins concentration and the microcystins content of mesozooplankton tissue increased with abundance. The bloom began in the upstream portions of the estuary and spread farther west during dry years. Bloom initiation required water temperature above 19C and surface irradiance in the visible range above 100 W m -2 . The bloom persisted during a wide range of water quality conditions but was closely correlated with low turbidity. The intensity of Microcystis blooms will likely increase with climate change due to increased water temperature and low streamflow during droughts. Elevated water temperature earlier in the spring could also extend the duration of Micro- cystis blooms by up to 3 months.

Remote Sensing of Channels and Riparian Zones with a Narrow-Beam Aquatic-Terrestrial LIDAR

The high-resolution Experimental Advanced Airborne Research LIDAR (EAARL) is a new technology for cross-environment surveys of channels and floodplains. EAARL measurements of basic channel geometry, such as wetted cross-sectional area, are within a few percent of those from control field surveys. The largest channel mapping errors are along stream banks. The LIDAR data adequately support 1D and 2D computational fluid dynamics models and frequency domain analyses by wavelet transforms. Further work is needed to establish the stream monitoring capability of the EAARL and the range of water quality conditions in which this sensor will accurately map river bathymetry.

Review of two decades of progress in the development of management options for reducing or eradicating phytoplankton, zooplankton and bacteria in ship's ballast water

* Corresponding author Abstract The worldwide transfer and introduction of non-indigenous invasive aquatic organisms via ships' ballast water has been amply demonstrated to cause significant ecological, economic and human health impacts. Possible solutions to the problem include: 1) treating ballast water to remove or destroy unwanted organisms; 2) re-designing new vessels to eliminate the need to discharge ballast water; and 3) retaining ballast water onboard. Ballast water exchange is currently the only widely acceptable and suggested (sometimes even required) procedure to minimise the risk of ballast water mediated invasions but the variable efficacy and operational limitations of this approach have led to significant financial investment in the last two decades in the research and development of more effective shipboard and shore based ballast water treatment technologies. Specific technologies under consideration include mechanical separation, heat treatment, UV irradiation, cavitation, de-oxygenation and active substances. To date, no single treatment option has proved to be universally effective and increasing attention has focused on multi- component treatment systems. The high flow rates and volumes of ballast water that must be treated pose significant technological challenges, and the presence of sediment in ballast tanks reduces the efficacy of many treatment options as this provides a habitat for resistant organisms such as resting stages of phytoplankton and zooplankton. Mechanical separation devices would best be used as a primary stage of a treatment system comprising multiple technologies because free-living organisms and sediment below a certain size are likely to be largely unaffected. UV treatment systems are unlikely to eliminate all ballast water organisms, as they are not able to deliver a stable lethal dose across a wide range of water quality conditions and many organisms are resistant to UV exposure or can recuperate after treatment. At the current stage of development, cavitation would not be considered appropriate for the shipboard treatment of ballast water due to high capital and operating costs and high power requirements. The heating of ballast water using waste heat from ships' engines has been claimed to be a practical and cost effective treatment options for eliminating ballast water zooplankton and phytoplankton (including resting stages) but concerns have been expressed that attainable temperatures may not eliminate all bacterial pathogens, that this approach does not apply to ships traversing colder seas and may impact on the integrity of vessel structures. Promising research has been conducted on several systems that are able to achieve temperatures capable of eliminating bacteria but these technologies are still under development. De-oxygenation by the addition of glucose or reducing agents are not effective treatment options, however de- oxygenation technologies based on the injection of an inert gas are more promising (notably against larval and adult zooplankton) as they could be cost effective and do not impact on the aquatic environment as ballast water is re-oxygenated prior to discharge. Biocide dosing systems have low capital costs and power requirements but the costs of active substances are significant. Chemical treatment costs and space requirements can be significantly reduced by using onboard chemical generators but the capital cost of these systems is significant and all have biological efficacy, safety, operational and environmental (poor biodegradation) concerns. Treatment systems that produce free hydroxyl radicals would be favourable over other chemical treatments as they are claimed to produce less or no toxic by-products at ballast discharge but these technologies have high power requirements. Each treatment option requires further research on their biological and operational efficacy and safety under full-scale shipboard conditions. As of July 2009, 16 promising systems using active substances had received basic approval and 8 systems final approval from IMO, with 4 systems receiving type approval certification and 2 systems receiving national approval certification. Effectively eliminating the risk of ballast water mediated invasions still remains a monumental technological and economical challenge.

Use of the biotic ligand model to predict pulse-exposure toxicity of copper to fathead minnows ( Pimephales promelas)

Concentrations of cationic metals (e.g., Ag, Cd, Cu, Ni, Pb, Zn) and other water quality parameters (e.g., pH, alkalinity, hardness, dissolved organic carbon (DOC) concentration) often cycle daily in surface waters, and the toxicity of the metals to aquatic organisms is altered by variations in those water quality parameters. Consequently, a method is needed to predict the LC50s (median lethal concentrations) of dissolved metals in temporally varying water quality. In this study, we combined the biotic ligand model (BLM), which predicts toxicity of cationic metals across a wide range of water quality conditions, with a one-compartment uptake-depuration (OCUD) model, which predicts toxicity of a chemical at any exposure time in either continuous or time-variable exposures, to test whether we could accurately predict pulse-exposure toxicity of Cu to fathead minnow (FHM; Pimephales promelas) larvae. First, we conducted continuous-exposure toxicity tests to calculate 1- to 96-h Cu LC50s for the FHM larvae. Then we re-parameterized the default Cu BLM for FHM until the corresponding predicted Cu LA50s (medial lethal accumulations at the biotic ligand) collapsed together into a narrow band and also fit the generalized pattern of an OCUD model [i.e., a steeply sloping plot of ln(LA50) versus ln(time) at short exposure times, followed by a gradual approach to an incipient lethal level at longer exposure times]. Next, in 72-h tests, we exposed FHM larvae to 2- or 8-h square-wave pulses of elevated Cu concentration followed by recovery in uncontaminated water for the remaining 22 or 16 h in each of three consecutive 24-h pulse-and-recovery cycles, at pH 6 or 7 in water containing either 0.5 or 2 mEq/L hardness and 0 or 20 mg DOC/L. Using the combined BLM-OCUD model developed from continuous-exposure data, we then predicted the Cu LA50s in the pulse-exposure tests and compared those LA50s to the observed pulse-exposure Cu LA50s. Although predicted pulse-exposure LA50s were within ∼4× of the observed pulse-exposure LA50s, delayed deaths during the recovery phases of the exposures precluded more accurate predictions of pulse-exposure Cu LA50s and, as a consequence, of pulse-exposure dissolved Cu LC50s. We conclude that one global OCUD equation linked to a re-parameterized Cu BLM for FHM can be used to predict the acute toxicity of continuous and pulse exposures of Cu to FHM larvae across a range of water quality conditions; but to improve the accuracy of those predictions, a mechanism must be developed to account for delayed deaths.

Community Structure and Environmental Conditions in Florida Shallow Lakes Dominated by Submerged Aquatic Vegetation

Florida inland waters are dominated by shallow lakes, many of which support the growth of submerged aquatic vegetation (SAV). We examined the species composition and selected environmental variables of SAV-dominated lakes using data from the Florida LAKEWATCH program. Our analysis revealed eight genera with approximately 15 species of SAV among these shallow lakes, which range in size from <2–2,300 ha. The SAV community within each lake primarily consisted of a single or a few species. Utricularia and Hydrilla were the most common SAV genera found in these lakes. Many SAV species grew well in a wide range of water quality conditions, although biodiversity and biomass tended to increase with increasing alkalinity and calcium concentration. More SAV species were also found in lakes with higher pH and Secchi depth. On average, Ceratophyllum, Najas and Vallisneria dominated lakes with high total phosphorus (TP) concentrations (0.034–0.053 mg/L) while Chara, Utricularia, Potamogeton and Myriophyllum corresponded with relatively low TP concentrations (0.008–0.013 mg/L). However, there was a large overlap in nutrient concentrations in lakes dominated by different species.

Hyperspectral reflectance of emergent macrophytes as an indicator of water column ammonia in an oligohaline, subtropical marsh

Narrow spectral band reflectance indices of two emergent macrophytes ( Typha latifolia and Borrichia frutescens) were found to correspond to changes in water column total ammonia (TA=NH 3+NH 4 +) of a constructed oligohaline (2–5 ppt) subtropical marsh (8 ha) designed as a shrimp farm treatment wetland in south Texas, USA, near the western Gulf of Mexico. A handheld hyperspectral radiometer measured plant leaf reflectance across the visible (VIS, 300–700 nm) and near-infrared (NIR, 700–1100 nm) spectrum during the mid-growing season (July–August). Reflectance of the two species and water quality (TA; total phosphorus (TP); salinity, S) were measured along a dynamic nutrient gradient from wetland inlet to outlet. Mean TA concentration was 1.22 mg N l −1 ranging between 0.92 and 1.71 mg N l −1. Salinity fluctuated between 2.5 and 4.5 ppt, while total phosphorus was between 0.01 and 0.86 mg P l −1. T. latifolia, the more dominant wetland cover: (a) reflected 1–5% less in the VIS compared to B. frutescens, (b) generally reflected 7–8% more in the NIR, (c) exhibited an average red-edge (RE) (718 nm) 15 nm greater than B. frutescens, and (d) had an average leaf normalized difference vegetation index [NDVI=( R 774− R 681)/( R 774+ R 681), where Rλ is reflectance at wavelength λ] of 0.82, versus 0.65 for B. frutescens. A multivariate linear regression equation containing photochemical reflectance index (PRI) and RE for T. latifolia explained 93% of TA variation ( P<0.001) when 0.10<TP<0.20 mg P l −1. For the entire range of water quality conditions, an equation containing PRI, RE and R 493/ R 678 for T. latifolia explained 72% of TA variation ( P<0.001). These results indicate that hyperspectral radiometry can quantify wetland ammonia concentrations in a treatment wetland, which could lead to development of remote techniques for continuously monitoring treatment effectiveness.

Impacts of Reduced Salinity on Seagrasses in Indian River Lagoon

AbstractFrom November 1993 to November 1995, a study was conducted in Indian River Lagoon (IRL) to determine relationships of light attenuation, water quality, and seagrass at sites representing a range of water quality conditions. There were considerable interannual differences at the sites. The most striking event occurred at a station in northern Banana River, an area of IRL considered the least anthropogenically impacted. This station had a well‐developed, multispecies seagrass bed (Halodule wrightii and Syringodium filiforme, with small quantities of Halophila englemannii). Throughout the first year, salinity was stable (90% of weekly values ranged from 26 to 32 ppt). Beginning in November 1994, the cover, shoot density, and biomass of all three species declined precipitously due to sharply reduced salinities associated with high rainfall and run‐off. Salinities during the following year varied little and remained low (90% of weekly values ranged from 13.5 to 19.8 ppt). The lack of recovery to earlier salinity levels was due to the long residence time (about 1 year) in that portion of IRL. Seagrass cover, shoot density, and biomass reached minima in May 1995. By August 1995, Halodule began to recover, but nearly 8 years later, Syringodium has not recovered to 1994 levels.

Controlling Giardia spp. and Cryptosporidium spp. in drinking water by microbial reduction processes

Drinking water microbial reduction has evolved from simple, effective chlorination to control waterborne diseases such as cholera and typhoid fever to advanced systems using ozone, chlorine dioxide, ultraviolet radiation, and combinations of disinfectants to control waterborne diseases such as poliomyelitis, hepatitis, giardiasis, and cryptosporidiosis. Giardia spp. and Cryptosporidium spp. have posed a major challenge to the water industry from a variety of perspectives. They occur in low concentrations in source waters, their infective doses in humans are low when compared with typical waterborne viruses and bacteria, they are difficult to inactivate with chlorine compounds, and they are difficult to determine if they are dead when detected in the environment or after microbial reduction in water treatment. However, Giardia spp. and Cryptosporidium spp. are readily controlled by ozone or ultraviolet radiation over a wide range of water-quality conditions. Chlorine dioxide provides a simple alternative to chlorine in some circumstances. Using modern microbial reduction process design techniques such as the integrated disinfection design framework (IDDF) ensures the provision of drinking water with a low risk of transmitting human pathogens to the consumer. Key words: ozone, chlorine dioxide, chlorine, ultraviolet, disinfection, microbial reduction, drinking water, Giardia, Cryptosporidium, parasite.

Ozonation of nom and algal toxins in four treated waters

The occurrence of cyanobacteria (blue–green algae) blooms and the possibility of production of cyanotoxins (algal toxins) have become major concerns for drinking water providers worldwide. Ozone has been shown to be effective for the destruction of some classes of toxins under specific conditions, although most researchers agree that the dose and contact time required will depend on water quality. The clarification of the relative effects of water quality parameters such as dissolved organic carbon concentration and character, and alkalinity, has not been previously attempted. In this study the cyanotoxins microcystin LR and LA and anatoxin-a were ozonated at a range of ozone doses in four treated waters with very different water quality. For both the toxins, 100% destruction was related to a residual ozone concentration present after 5 min. This was, in turn, related to the water quality and indicated that a direct reaction with molecular ozone could be responsible for the destruction. The results confirmed that both the toxins would be destroyed under conditions usually utilised for ozonation prior to granular activated carbon (GAC) filtration. This will apply under a range of water quality conditions but not necessarily a range of temperatures. The saxitoxin class of compounds was very resistant to oxidation by ozone and would require further treatment such as GAC filtration.

The decrease of UV absorbance as an indicator of TOX formation

The decrease in UV absorbance (ΔUV) caused by chlorination of NOM correlates linearly with the amount of TOX formed, for a remarkably wide range of water quality conditions and reaction times. THM formation also correlates with ΔUV, but the relationship is more sensitive to solution pH and is probably not linear over the entire range of conditions/times relevant for water treatment. It appears that all Cl-DOC reactions that destroy UV absorbance generate TOX, but substantial amounts of THMs are formed only after a significant amount of reaction has occurred.

Refining Habitat Requirements of Submersed Aquatic Vegetation: Role of Optical Models

A model of the spectral diffuse attenuation coefficient of downwelling irradiance was constructed for Chincoteague Bay, Maryland, and the Rhode River, Maryland. The model is written in terms of absorption spectra of dissolved yellow substance, the chlorophyll-specific absorption of phytoplankton, and absorption and scattering by particulate matter (expressed as turbidity). Based on published light requirements for submersed aquatic vegetation (SAV) in Chesapeake Bay, the model is used to calculate the range of water-quality conditions that permit survival of SAV at various depths. Because the model is spectrally based, it can be used to calculate the attenuation of either photosynthetically active radiation (PAR, equally weighted quanta from 400 nm to 700 nm) or photosyntheticallyusable radiation (PUR, the integral of the quantum spectrum weighted by the pigment absorption spectrum of SAV). PUR is a more accurate measurement of light that can be absorbed by SAV and it is more strongly affected by phytoplankton chlorophyll in the water column than is PAR. For estuaries in which light attenuation is dominated by turbidity and chlorophyll, the model delimits regions in which turbidity alone (chlorophyll 10 μg 1−1, turbidity >1 NTU) must be reduced to improve survival depths for SAV.

Remote sensing of Lake Chicot, Arkansas: Monitoring suspended sediments, turbidity, and Secchi depth with Landsat MSS data

This research used water quality data from Lake Chicot, Arkansas and a corresponding set of Landsat MSS data to compare the ability of satellite-based sensor systems to monitor suspended sediment concentration, Secchi disk depth, and nephelometric turbidity. Lake Chicot was selected, in part, because of the availability of a wide range of water quality conditions. Secchi disk depth and nephelometric turbidity are both optical measures of water quality and differ from suspended sediment concentration, which is a measure of the weight of inorganic particulates suspended in the water column. four different models for these relationships between the satellite data and the water quality data were tested: 1) simple linear regression analysis with the satellite data transformed to exo-atmospheric reflectance, 2) a simple linear regression involving a natural logarithm transformation of the satellite and water quality variables, 3) simple linear regression analysis of the digital chromaticity transformation of the satellite data and the natural logarithm of the water quality data, and 4) optimized curve fitting of a theoretically derived exponential model for the relationship between exoatmospheric reflectance and the water quality data. Two different solar spectral irradiance curves and an orbital eccentricity correction factor are tested using the exponential model. Results suggest: 1) Remote sensing from space-based platforms can provide meaningful information on water quality variability; 2) an exponential model best characterizes the relationship between the satellite data and the water quality measures investigated; 3) slight differences result from using the solar curve proposed by the World Radiation Center (as opposed to the NASA standard); and 4) predictions based on optical measures of water quality, rather than measures of the weight of particles in the water column, are slightly better when using Landsat MSS data.

A Review of Sodium Cyanide for Use in Sampling Stream Fishes

Abstract Sodium cyanide was used to sample several streams in Wyoming and Utah representing a range of water quality conditions: alkalinity, 12-1,540 ppm; pH, 7.3-8.4; water temperature, 45-70 F, and flows of 2-300 cfs. The material was used to collect fish (through anesthesia) for length-weight analysis, stock estimates, and to remove fish completely from study sections. Sodium cyanide (NaCN) was effective in sampling streams which had proven difficult to sample by more conventional electrofishing techniques. Laboratory tests using cutthroat trout (Salmo clarki) showed that all test fish recovered from exposure to 1 ppm CN for 10, 15, and 20 minutes. During 6 months of observation, they continued to eat and gain weight as would be expected for unexposed fish of the same species and age.