Influence of inter-annual variations in climatic factors on fecal coliform levels in Mississippi Sound

Information on the effects of inter-annual variations in climatic factors on fecal coliform levels in coastal waters is scarce. We used 11 years (1990–2001) of rainfall, water temperature, Pearl River stage and salinity data to assess the effects of the 1991–1992 and 1997–1998 El Niño events on fecal coliform levels in Mississippi Sound. El Niño-Southern Oscillation had major effects on Pearl River stage and water quality in the Sound. The geometric mean fecal coliform number differed among years (P=0.0001), being highest during 1991–1992 El Niño years (14.22 MPN per 100 ml) and lowest during 1999–2000 La Niña years (<1.8 MPN per 100 ml). Mean salinity varied among years (P=0.0001) from 9 ppt (1991–1992) to 21 ppt (1999–2000). Mean water temperature was lowest in 1997–1998 (14.5 °C) and highest in 1998–2000 (19.4 °C). Pearl River stage differed among years (P=0.0001), ranging from 1.96 m (1999–2000) to 3.57 m (1997–1998). Inverse relationships were observed between fecal coliform levels and salinity (r²=0.74; P=0.001) and water temperature (r²=0.69; P=0.001), whereas positive relationships were obtained with total rainfall (r²=0.52; P=0.013) and Pearl River stage (r²=0.90; P=0.0001). These relationships are useful for evaluating the potential effects of climate change on water quality and classification of shellfish growing waters in order to protect humans from consuming contaminated shellfish in shallow river-influenced estuaries.     

Toxicity of chlorine to juvenile spot, Leiostomus Xanthurus

The sensitivity of juvenile spot, Leiostomus xanthurus, to total residual chlorine (TRC) in flowing sea-water was investigated. Incipient LC₅₀ bioassays, histopathology, avoidance tests and the combined effect of thermal stress and TRC were used to assess sensitivity.

Estimated incipient LC₅₀ values were 0.12 mg 1⁻¹ TRC at 10°C and 0.06 mg 1⁻¹ TRC at 15°C. Histological examination of spot used in the incipient LC₅₀ bioassay at 15°C and sacrificed while alive indicated pseudobranch and gill damage occurred in individuals exposed to a measured TRC concentration of 1.57 mg 1⁻¹. Spot exposed to lower concentrations of TRC, 0.02 0.06 mg 1⁻¹ at 15°C and sacrificed alive showed no consistent tissue damage.

Spot demonstrated temperature dependent avoidance responses to TRC. At 10°C, a concentration of 0.18 mg 1⁻¹ was required for significant (X²; P < 0.05) avoidance; at 15 and 20°C, spot showed significant avoidance of TRC concentrations as low as 0.05 mg 1⁻¹.

Simultaneous exposure of spot to thermal stress (5, 10 or 13°C above the acclimation temperature of 15°C) at measured TRC concentrations of 0.05 0.07 and 0.34–0.52 mg 1⁻¹ demonstrated a significant, (Z²) with Yates correction, P < 0.05) increase in sensitivity to TRC with increased temperature and exposure times for some of the groups tested.     

Fine-spray (water mist) protection of shipboard engine rooms

Twenty-three fire tests were conducted to determine the ability of current fine-spray (water mist) technologies to extinguish fires specified in the International Maritime Organization (IMO) fire test procedure for engine rooms greater than 3000 m³. The tests were conducted using nozzle installed at a 5 m height and 1·5 m spacing in a large test facility (2800 m² area and 18 m height). Two types of nozzles were tested: a low pressure nozzle operating between 1·2 and 1·5 MPa with flow per nozzle between 12·0 and 13·41/m and a multi-nozzle high-pressure prototype consisting of seven nozzles operating at 6·9 MPa flowing at 5·3 1/m per prototype. These nozzles were selected because they had been shown to extinguish IMO fire tests in enclosures with a protected area of 83 m² and a ceiling height of 4·5 m. The fire tests selected from the IMO procedure included 6 MW diesel spray fires on top of the IMO engine mock-up, a shielded 6 MW diesel spray fire adjacent to the mock-up, a 1 MW shielded diesel spray fire adjacent to the mock-up, and a wood crib within a 2 m² pan filled with heptane. In tests in which no additional enclosure surrounded the nozzles other than the test facility, fires were not significantly affected by the water mist using either nozzle. To further investigate mist-system capabilities, a ceiling was then placed directly over the nozzles at a 5 m height covering an area of 188 m². Using 90 high-pressure prototype nozzles, the test fires were not extinguished. A 940 m³ enclosure was then formed by dropping tarpaulins to the floor from the ceiling. A 4 m² vent was placed in the wall. With the 90 high-pressure prototype nozzles, the 6 MW spray fire on top of the mock-up was extinguished. When the 6 MW fire was shielded beside the mock-up, the fire was not extinguished. With the vent closed, the 6 MW shielded spray fire was extinguished. Under the same test conditions, a 1 MW shielded diesel spray fire and a 0·1 m² heptane pool fire were not extinguished. The fire test results indicated that protection of engine rooms with volumes of about 1000 m³ is possible by optimizing current fine-spray technology while significantly larger volumes will require improved discharge characteristics.     

Variation of ATP content in Scenedesmus dimorphus cells grown in a chemostat culture and its comparison with chlorophyll-A content

The variations of ATP and chl-a contents in Scenedesmus dimorphus cells grown in a chemostat culture under nutrient limitation were investigated. ATP and chl-a contents per algal dry weight varied in the ranges of 0.15–1.64 μg mg⁻¹ (0.33–3.82 μg mg⁻¹ as ATP/C ratio) and 0.32–1.32% (7.8–30.8 μg mg⁻¹ as chl-a/C ratio), respectively, under the conditions of T-N/T-P ratio of 2–50 by weight and dilution rate of 1–4 per day. At every T-N/T-P ratio, both ATP and chl-a contents increased as dilution rate increased. At a given dilution rate, ATP content decreased systematically as T-N/T-P ratio increased, with the only exception at dilution rate of 4 per day. It was considered based on the result that ATP or chl-a can hardly be used successfully as an indicator of algal biomass.     

The energy balance of an exterior window surface, Inuvik, N.W.T., Canada

This paper examines the energy loss of an exterior window surface during the month of January, 1975, in Inuvik, N.W.T., Canada. Radiative exchanges (L^*) were measured and the energy loss through the window was calculated (Q_F). Since an energy balance exist at the exterior window surface, a heat transfer coefficient (h) was determined by residual: h=(Q_F−L^*)/(T_s−T_a). Calculated values for the heat transfer coefficient compare favourably with those of other studies. The atmospheric controls (i.e. wind speed and cloud cover) on radiative and convective heat losses and their influence on urban climate are discussed with respect to the observational data.     

Size selective continuous flow filtration method for detection of Cryptosporidium and Giardia

We describe a size selective continuous flow filtration method for detecting Cryptosporidium oocyst and Giardia cyst in finished water. Twenty liters of finished water spiked with Cryptosporidium oocysts (110) and Giardia cysts (60) were filtered through macro (5.0–10.0 μm) and micro (3.0 μm) pore-sized polycarbonate-track-etch (PCTE) membrane filters housed into two separate 47 mm diameter filter holders joined with a stainless steel nipple. The macro-pore-sized filters removed larger unwanted particles while allowing the Cryptosporidium oocysts and Giardia cysts to pass through, these being subsequently captured on the micro-pore-sized filter. The eluted oocysts and cysts were transferred onto the well-slide, stained by IFA and examined microscopically. The mean recovery efficiencies obtained for Cryptosporidium oocysts using the filter pairs of macro 5 μm and micro 3 μm, macro 8 μm and micro 3 μm, and macro 10 μm and micro 3 μm were 67.3%, 77.2–85.0% and 76.9–82.2%, respectively. Whereas the recovery rates for Giardia cysts using the same filter pairs were 0, 55 and 77.1%. The filter pair having the pore size of macro 10 μm and micro 3 μm was found to be most efficient in the simultaneous detection of Cryptosporidium and Giardia in the finished water. This method is simple, easy, rapid and economical.     

Productivity and nitrogen balance in large scale phytoplankton cultures

Biomass production and nitrogen balance was studied in 35,000 gal (133,000 1) phytoplankton cultures comprising the first stage in a tertiary sewage treatment-mariculture system. The diatom Phaeodactylum tricornutum persisted for most of the study. At secondary sewage effluent loadings sufficient to produce residual dissolved inorganic nitrogen concentrations above approximately 5 μg atoms l⁻¹, an N:C ratio (molar) of 0.17 was obtained and algal growth was not nutrient-limited. Biomass levels, and hence pond particulate carbon and nitrogen output, varied in response to solar irradiance and dilution rate, but not temperature. Mean winter and summer yields were approximately 1 and 5 g (83 and 417 mg atoms) C m⁻² d⁻¹ respectively. An inverse relationship existed between algal biomass concentration and dilution rate, such that in the late spring optimal pond yields occurred between 0.55 and 0.65 dilutions d⁻¹. Better than 95% dissolved total nitrogen removal was obtained. Net dissolved organic nitrogen production, that would offset dissolved inorganic nitrogen removal, did not occur. Pond particulate nitrogen output was usually less than dissolved total nitrogen removal. Probable explanations for this include (1) ammonia evolution to the atmosphere at high pond pH, (2) particulate nitrogen sedimentation, and (3) denitrification. Of these, the first is believed to be quantitatively the most significant.     

Utilisation de l''algue oocystis sp. pour le traitement tertiaire des eaux usées—I. Culture en vrac de cellules préalablement conditionnées en cyclostat

With the aim of developing an efficient and economic method for the tertiary treatment of wastewater, a two-phased culture system of Oocystis alga is presented. During the first phase, a unialgal strain grows in a cyclostat supplied with secondary effluents diluted to a low concentration (50 μM NH₄⁺, i.e. 0.7 mg N 1⁻¹) of inorganic ions. Once the equilibrium is reached (i.e. the cell population is conditioned and the nutrient concentration is zero), in a second phase, the starved cells are mixed with a secondary effluent which has a higher nutrient content (200–400 μM NH₄⁺, i.e., 2.8–5.6 mg N 1⁻¹). Ion depletion (NH₄⁺, NO₃^-, NO₂^- and PO₄^3-) follows specific kinetics; successive identifiable stages related to photoperiod lead to a complete stripping of nutrients. In addition to ion concentrations, pH and cell population were determined every 2 h during the experiment. Results and conclusions are presented.     

Development of an immunoassay for a quaternary ammonium compound, benzyldimethyldodecylammonium chloride

A competitive enzyme-linked immunosorbent assay (CELISA), based on polyclonal antibodies, was developed to measure benzyldimethyldodecylammonium chloride (BDD₁₂AC), a component of benzalkonium chloride (BAK). The polyclonal antibodies recognized free benzyldimethyldodecylammonium bromide (BDD₁₂AB) in an indirect competitive ELISA with a 50% inhibition (IC₅₀) of 0.66±0.20 μg/ml and a detection limit of 0.043±0.033 μg/ml. The two other components of BAK, benzyldimethyltetradecylammonium chloride (BDT₁₄AC) and benzyldimethylhexadecylammonium chloride (BDH₁₆AC), were recognized to varying degrees by the antibodies. The antibodies did not cross-react with other compounds such as fatty acids and alcohols, amino acids, amines, and short-chain quaternary ammonium compounds. Cross-reactivity was observed with other alkyldimethylbenzylammonium compounds (ADBACs). The CELISA and HPLC were used to measure the amount of pure BDD₁₂AB spikes in milk and BDD₁₂AC in five commercial products. HPLC analysis correlated well with CELISA analysis for spiked samples.     

The maturity method: Modifications to improve estimation of concrete strength at later ages

Two modifications have been proposed for the Nurse–Saul maturity function to get better estimates of compressive strength of concrete cured at different temperatures. The modifications account for the effect of w/c ratio on the temperature dependence of strength development and the effect of curing temperature on the long-term strength. The effect of the proposed modifications on the estimation of concrete strength using the Nurse–Saul maturity function have been compared with the estimation using unmodified Nurse–Saul equation with two different datum temperatures (i.e., T₀ = −10 °C and T₀ = 0 °C). The results show that applying the proposed modifications improves the accuracy of estimated concrete strength at different curing temperatures, especially at later ages.     

Simultaneous determination of trace amounts of free cyanide and thiocyanate by a stopped-flow spectrophotometric method

Simultaneous determination of free cyanide and thiocyanate was investigated using a stopped-flow spectrophotometric method. 1,3-dimethylbarbituric acid/isonicotinic acid at pH 5.2 was used as the colour reagent for both cyanide and thiocyanate determinations. The absorption spectrum of the complex formed by cyanide and thiocyanate with the colour reagent has a maximum wavelength at 600 nm, giving a low detection limit of 0.5 μg l⁻¹ for cyanide and 1.5 μg l⁻¹ for thiocyanate. Two proposed processes — 1,3-dimethylbarbituric acid combined with formaldehyde masking cyanide and the ferric-thiocyanate methods — can simultaneously determine free and other simple forms of cyanide and thiocyanate existing at pH 5.2; comparison of results demonstrates that both approaches are in agreement. By taking into account the effect of temperature on colour development and by using the ratio of the regression slopes, one kind of standard solution (thiocyanate) can be used for both cyanide and thiocyanate calibration, thereby avoiding the need to use toxic cyanide standard solutions.     

Survie in vitro de Yersinia dans les eaux d'alimentation et recuperation par filtration sur membraneIn vitro survival of Yersinia strains in drinking water and recovery by membrane filtration

This study was undertaken to determine the survival characters and optimal parameters for the recovery of Yersinia from drinking water samples. Experiments were done by artificial contamination of 4 different water samples with 4 Yersinia strains.

The strains tested along this study are: Y. enterocolitica 4052, 0:3 and 4360, 0:9, Y. enterocolitica intermedia 3953, 0:17 and Y. pseudotuberculosis 0:1. The water samples are characterized by an increasing mineralization: Distillated water, Gerardmer water (-30,300 ω cm⁻¹—Hardness = 1° Français), Nancy water (-4500 ω cm⁻¹—H = 10°) and Vittel water (-730 ω cm⁻¹, H = 71°).

Total mineralization does not significantly affect the survival of Yersinia at 20°C, but causes a dramatic decrease of the Yersinia strains at 4°C for the most mineralized water. There is no pH effect from alkaline, neutral and acidic values until pH 4.4 but Yersinia is greatly affected by more acidic pH.

The previous stay of Yersinia strains in artificially contaminated water causes a reduction of kinetic growth during cultivation on peptone-water but does not change the recovery rate by filtration method.

The recovery rate of the filtration method using cellulose acetate membranes (mean porosity = 0.45 μm) is very poor, ranging from 0 to 8%. The efficiency is significantly higher with the aid of polyester membranes treated by laser (Nucleopore−0.40 μm) ranging from 12 to 53% according to the mineralization of the water. The best recovery rate is obtained with the moderately mineralized water.

These results can explain the poor results obtained with the use of water bacteriology classical methods for the search of Yersinia.

Thus the best results can be predicted from the concentration of fairly mineralized water by filtration on polyester membrane at neutral, alkaline or weakly acidic pH.     

Limiting nutrients of phytoplankton community in Hiroshima Bay,Japan

Ratios of DIN:DIP, indigenous algal assay and nitrogen fixation by phytoplankton were determined to estimate the limiting nutrient for phytoplankton growth in Hiroshima Bay, Seto Inland Sea, Japan. The algal assay was performed using indigenous pico-, nano- and microphytoplankton assemblages fractionated by filtration. Nitrogen fixation was determined using an acetylene reduction method. The DIN:DIP ratio in the study area was above 16:1 (Redfield ratio) in August 1993 and May 1994. However, in other months, the ratio was below 16:1. These values suggest that the growth of phytoplankton community is limited by nitrogen, with an exceptional phosphorus limitation in August 1993 and May 1994. Nutrient enrichment algal assay of size-fractionated phytoplankton community also supported these findings. The growth of picophytoplankton fraction was stimulated by phosphorus addition in August 1993 and May 1994, while nano- and microphytoplankton fractions were stimulated by nitrogen addition in almost all months during the study period. No nitrogen fixation by phytoplankton was detected during the study period. The results suggest that nitrogen rather than phosphorus is the limiting nutrient for the growth of the whole phytoplankton community, but picophytoplankton by itself, tends to be limited by phosphorus compared to other large-size phytoplankton when high DIN:DIP ratio was observed.     

Phosphorous limitation in an arctic river biofilm—A whole ecosystem experiment

A fourth-order arctic river was experimentally enriched with phosphate (7.7 ± 7.0 μ g 1⁻¹) to determine the effect of such a loading (equivalent to a community of 10,000 people) upon the trophically important biofilm. The effect upon a light-grown biofilm (an autotrophic/heterotrophic assemblage) and a dark-grown biofilm (predominantly heterotrophic assemblage) was determined after 28 days of colonization. Seven attributes of the biofilms were monitored, 2 autotrophic indices, chlorophyll , [¹⁴C]HCO₃ incorporation into lipids and 5 heterotrophic indices; [¹⁴C]acetate incorporation into lipids, metabolic heat output, turn-over times of microbially labile glucose and glutamate and mineralization of microbially recalcitrant ring-labelled [¹⁴C]hydroxybenzoic acid. The findings showed that the addition of phosphorus resulted in a substantial stimulation of both autotrophic and heterotrophic processes suggesting that arctic rivers of this type would be liable to cultural eutrophication.     

The effect of wastewater phosphorus removal on shagawa lake, Minnesota: phosphorus supplies, lake phosphorus and chlorophyll a

In early 1973, the phosphorus supply to Shagawa Lake, Minnesota, was reduced by about 80% when a tertiary wastewater treatment plant began operating. Significant reductions in total and soluble reactive phosphorus concentrations have occurred in the lake since that time. By 1976 the average (volume weighted over the entire lake) total and soluble reactive phosphorus concentrations had declined from about 51 and 21 μg l⁻¹ to about 30 and 4.5 μg l⁻¹, respectively, corresponding to 40 and 80% reductions. During 1975 and 1976, chlorophyll a (averaged over the top 5 m) had decreased to less than 50% of the pretreatment level during May-June but during July-August little change had occurred.

A phosphorus residence time model projected equilibrium total phosphorus concentrations of about 12 μg l⁻¹ within 1.5 years. The fact that this level was not reached is attributed to a feedback of phosphorus from the sediments, primarily during summer. This phenomenon has been incorporated into a modified total phosphorus mass balance model which projects the phosphorus pattern through 1976 quite accurately. The close fit of the modified mass balance model implies that the phosphorus supply from the sediments has not diminished since treatment since treatment began, and that further recovery of the lake will depend upon how long this feedback of phosphorus from the sediments continues.     

Environmental modification of the photosynthetic response of lake plankton to surfactants and significance to a laboratory-field comparison

The toxic effects of nine surfactants on the short-term photosynthetic activity of lake plankton and factors affecting the response were investigated in multiple monthly studies conducted during May–October. The impact of the detergent chemicals on photosynthesis differed with the mean 3 h EC₅₀ values ranging from 0.6 to 28.7 mg l⁻¹. The photosynthetic response to the same surfactant varied as much as 80 ×, attributed in part to monthly changes in water temperature (range = 17–28°C) and to seasonal differences in phytoplankton composition. Overall, the test chemicals were less toxic during periods of lower water temperature, diatom dominance and low algal density. The in situ photosynthesis results were compared to those from standard algal laboratory toxicity tests to assess the environmental relevance of a laboratory data base. These 96 h tests were conducted with the same surfactants but monitored growth effects on three cultured algae. Based on this comparison, the laboratory effect concentrations were typically either similar to or lower than those in the field. Key considerations in this laboratory-field comparison were the environmental modification of the photosynthetic response, the surfactant type, and the differential sensitivities of the cultured laboratory algae.     

Studies on the persistence of some carbamate insecticides in the aquatic environment—I. Hydrolysis of sevin, baygon, pyrolan and dimetilan in waters

This paper describes the analysis and rates of hydrolysis of the monoalkyl carbamate insecticides Sevin and Baygon, and the dialkyl carbamates Pyrolan and Dimetilan in aqueous media. The rates of hydrolysis with different hydroxylion concentrations were measured. Second order rate constants for Sevin, Baygon, Pyrolan and Dimetilan at 20°C were found to be 2.04 x 10², 3.04 x 10, 7.0 x 10⁻¹ and 3.4 x 10⁻³ 1. mol⁻¹ min⁻¹, respectively, indicating that the dialkyl carbamates were more stable to alkaline hydrolysis than the monoalkyl carbamates. The rates of hydrolysis at different pH values, ranging from 4.0 to 10.0, were also studied. All the compounds were stable to hydrolysis within the acidic pH range. However, measurable hydrolysis was observed at pH 7.0 and 8.0 for sevin and baygon, respectively, and the rates of hydrolysis increased with the rise of the pH value. At pH 8.0 about 99 per cent of sevin was hydrolyzed in 9 days while baygon reached the same level of hydrolysis after 107 days. Pyrolan and Dimetilan, on the other hand, were stable towards hydrolysis within the investigated pH range. The effect of temperature on the rates of hydrolysis was also investigated. This study shows that the persistence of the carbamate pesticides in natural waters is greatly influenced by the pH value and temperature of the aquatic environment.     

Growth of Selenastrum capricornutum in natural waters augmented with detergent products in wastewaters

A determination of whether the removal of phosphate builders from detergents would modify the ability of domestic secondary treated sewage effluent to stimulate the growth of a test alga (Selenastrum capricornutum-Printz) in receiving waters alone and augmented with detergent products was made. The lakes used as sources of test waters were located in northeastern New York State and possessed total phosphorus concentrations ranging from ca. 0.01 to 0.04 mg P1⁻¹.

The alga experienced stimulation in all three test lake waters from secondary sewage containing detergent with phosphate or detergent without phosphate. A concentration of 60 μg P 1⁻¹ was sufficient to effect significant algal growth in two of the test waters; however, concentrations ranging up to 110 μg P 1⁻¹ did not generate such a response in the third test water. This latter result and others suggested that neither phosphorus nor other nutrients from these wastewater additions were the factors fully accountable for the observed response(s).     

Denitrification rates in relation to stream sediment characteristics

Potential rates of nitrate removal were studied in sediments from three Ontario rivers that differed in texture, organic carbon contents and other characteristics. Intact 0–5 cm depth sediment cores from 22 sites on each river were overlain with aerated 5 mg 1⁻¹ NO₃⁻-N solution and incubated in the laboratory at 21°C for 48 h. Rates of nitrate-N loss from the overlying solutions varied from 37 to 412 mg m⁻² day⁻¹ for a 24 h incubation period. The acetylene blockage technique was used with nitrate amended sediments to evaluate the relative importance of denitrification and nitrate reduction to ammonium. Denitrification accounted for 80–100% of the nitrate loss in the majority of sediment samples tested. Rates of nitrate loss for the 24 h period exhibited a highly significant positive correlation (r = 0.82–0.89) with the water-soluble carbon content of the sediments in each river. Significant relationships were also observed between nitrate loss and organic carbon, total nitrogen and sediment ammonium. A decline in nitrate loss via denitrification and increased nitrate reduction to ammonium was correlated with the organic carbon and water-soluble carbon content of the stream sediments.     

The effects of free chlorine and chloramine on growth and respiration rates of larval lobsters (Homarus Americanus)

The length, dry weight and standard respiration rate of larval lobsters (Homarus americanus) were monitored for 19 days following a 60 min exposure at 25°C to 1.0 mg I⁻¹ applied free chlorine and 1.0 mg I⁻¹ applied chloramine. Compared to control organisms, significantly lower increases in dry weight (P < 0.05) and significant reductions in standard respiration rates (P < 0.01) were measured among exposed organisms; greater differences were detected among chloramine exposed organisms. From these results it can be concluded that acute exposure to either free chlorine or chloramine results in subsequent reductions in growth and metabolic activity of larval lobsters.