Hydrodynamic control of nitrogen and phosphorus turnover in an eutrophicated estuary in the Baltic

The turnover of phosphorus and nitrogen have been studied in a low salinity estuary in the Bothnian Sea. The estuary, G?rdsfj?rden, has a high loading of nutrients from a pulp and paper mill which supplies the estuary with three times the annual natural input of phosphorus and nitrogen, respectively. The turnover of nutrients was to a great extent determined by hydrodynamic variations. During periods of intense resuspension there was a net export of particulate bound nutrients from the estuary to the sea but since these periods were short there was an overall net retention of particulate nutrients. The estuary was a source for dissolved phosphorus to the sea. The major source of phosphorus export was release of dissolved P from anoxic sediments. G?rdsfj?rden was a sink for dissolved nitrogen which most likely escaped the estuary by denitrification. Nitrate was supplied by degradation of particulate organic nitroge'n but the main source was import from the sea.     

Relative survival of Escherichia coli and Salmonella typhimurium in a tropical estuary

Microcosm studies have been carried out to find out the relative survival of Escherichia coli and Salmonella typhimurium in a tropical estuary. Survival has been assessed in relation to the important self-purifying parameters such as biotic factors contained in the estuarine water, toxicity due to the dissolved organic and antibiotic substances in the water and the sunlight. The results revealed that sunlight is the most important inactivating factor on the survival of E. coli and S. typhimurium in the estuarine water. While the biological factors contained in the estuarine water such as protozoans and bacteriophages also exerted considerable inactivation of these organisms, the composition of the water with all its dissolved organic and inorganic substances was not damaging to the test organisms. Results also indicated better survival capacity of E. coli cells under all test conditions when compared to S. typhimurium.     

Distribution of organic carbon in tropical mangrove sediments (Cochin,India)

Surficial sediments were sampled every month from three mangrove regions around the metropolis of Cochin (India). Sedimentary organic carbon content exhibited wide seasonal fluctuations. The hydrology of the mangrove system is regulated mainly by high rainfall during the monsoon and by tidal inundation. The results indicated the role of tidal activity and sediment texture in the preservation and retention of organic matter.     

Inorganic nitrogen removal in a combined tertiary treatment-marine aquaculture system—II. Algal bioassays

Algal bioassays were conducted on samples from various components of the combined tertiary treatment-marine aquaculture process, described in Part I of this study. These assays demonstrated that nitrogen removal is necessary to prevent increasing the algal growth potential of coastal marine waters receiving wastewater discharges. When nitrogen was removed from secondarily treated domestic wastewater, the wastewater in varying dilutions with seawater could not support more algal growth than the seawater alone. By adding nitrogen back to the treated wastewater the algal growth potential was increased to that of the untreated wastewater. This was demonstrated by assaying samples containing both artificially added nitrogen, and nitrogen regenerated by oysters. Assays of the effluent from the seaweed system showed that the removal of regenerated nitrogen reduced the algal growth potential to that of natural seawater.     

Inorganic nitrogen removal in a combined tertiary treatment—marine aquaculture system—I. Removal efficiences

The increasing awareness that nitrogen is often a key nutrient controlling algal growth in coastal marine waters has led to a concerted effort to find ways to remove ammonia and nitrate from wastewaters. A novel approach to this problem involves the combining of algal and seaweed nutrient stripping processes with a marine aquaculture. Not only is nitrogen removed from wastewater, but important commercial shellfish and seaweeds are produced.A prototype process consisting of growth systems for marine algae, oysters and seaweed, joined in series, was fed secondarily treated wastewater, diluted 1:4 with seawater, for 11 weeks during the Summer of 1972. During this time 95 per cent of the influent inorganic nitrogen was removed by algal assimilation. The oysters in turn removed 85 per cent of the algae, but regenerated as soluble ammonia 16–18 per cent of the nitrogen originally bound in the algal cells. All of the regenerated nitrogen was removed in the seaweed system so that the total inorganic nitrogen removal efficiency of the system was 95 per cent. Phosphorus removal on the other hand was not nearly as complete as only 45–60 per cent was removed.The process has the capability of being expanded to include additional trophic levels in an integrated and highly controlled food chain system to serve the dual function of tertiary wastewater treatment and waste recycling through the production of shellfish and seaweeds.     

Inorganic nitrogen release kinetics and exchangeable inorganic nitrogen of the sediments from shallow lakes in the middle and lower reaches of the Yangtze River region

Inorganic nitrogen (IN) release kinetics and exchangeable inorganic nitrogen (EIN) of the sediments from shallow lakes in the middle and lower reaches of the Yangtze River region were investigated. The results showed that the EIN contents of the studied sediments ranged from 131 to 274 mg/kg. With the increase of the total nitrogen (TN) contents, their EIN also significantly increased. Their ratios of EIN to TN ranged from 5 to 17%, and with the increase of their TN contents, their ratios decreased. The relative contribution of NH₄⁺‐N and NO₃^‐N to EIN ranged from 83 and 11% to 89 and 17%, respectively. The curves of the NO₃^‐N release kinetics of the studied sediments were not completely consistent with those of IN and NH₄⁺‐N. The amounts of the IN released from sediments not only relate to their EIN contents, but also to other N fractions.     

Copper as an algicide in a tropical reservoir

Copper sulphate, added at the surface, was retained in the epilimnion of a stratified tropical reservoir. For 12 days after the addition, most of the copper was associated with the soluble fraction (MW > 50,000). Later the low molecular weight fraction (MW < 50,000) dominated and persisted for more than 19 days. There was an immediate decline in algal density after copper addition, followed by an increase in numbers of the more copper-tolerant chlorophyte species. Zooplankton (and other aquatic fauna) were also affected by the copper treatment. Two forms of the rotifer Brachionus calyciflorous recovered first, followed by Hexarthra mira, Copepoda and Cladocera. Growth of cyanobacteria was suppressed in the short term, but any possible long term effects of copper were masked by flow induced rapid destratification which interrupted and re-set algal succession. It is concluded that copper treatment is not an effective control of cyanobacterial growth under the seasonal flow regime to which the Solomon Dam is subjected.     

Application of a rapid method for identifying fecal pollution sources in a multi-use estuary

We demonstrate the application of a new PCR assay to detect and differentiate human and ruminant sources of fecal pollution in natural water samples. We tested samples collected from Tillamook Bay, Oregon, which has a long history of fecal pollution levels that exceed acceptable standards. The most likely sources are from dairy operations and ineffective sewage treatment. Using a suite of three PCR primer pairs specific for human or ruminant bacterial 16S ribosomal DNA markers, we detected at least one marker in 17 of 22 samples. In general, host-specific fecal markers were detected in areas that are heavily impacted by anthropogenic activities. Nine out of 11 sites classified as either urban or near a sewage point source were positive for the human marker while only five of these same sites were positive for ruminant markers. Conversely, 12 out of 21 sites classified as rural or agricultural use were positive for ruminant markers, while only six of these sites were positive for human pollution. This suite of host-specific genetic markers holds promise for identifying non-point source fecal pollution in coastal waters.     

Changes in a temperate estuary during the filling of the biggest European dam

This study aimed to determine whether and how the disruption of river flow, during the filling of the Alqueva dam, influenced the variability of abiotic and biotic factors in the Guadiana estuary, particularly the abundance and distribution of anchovy eggs. River inflow was found to be the most important factor in determining abiotic and biotic variability in the Guadiana estuary. Seasonal patterns were obscured by long periods of low inflow (mid April to early December 2002), which caused marked changes in the estuary. The estuarine turbidity maximum zone was displaced towards the upper estuary, to at least 38 km from the river mouth, 8 to 16 km upstream from previous records. The dynamics of nutrient stoichiometry was also affected. In the upper and middle estuary, P was more potential limiting than N and potential Si limitation was only frequent on the coast, with direct and/or indirect influence in changing phytoplankton dynamics and composition. Previously, the upper estuary alternated between potential P limitation during winter, Si limitation during spring and mid summer and N limitation during mid summer and autumn. The flooding of vast areas in the catchment of the dam probably caused the increase of DSi concentrations, as well as maximal N and P loadings. The abundance of larval stages of anchovy decreased, putatively because estuarine productivity has also decreased. In April 2002 there was an uncontrolled discharge from the Alqueva dam, which reduced the abundance of anchovy eggs by 99.99%. It is suggested that dam managers should mimic, as much as possible, the natural river flow, in order to minimize the impact on downstream ecosystems. Management efforts should not be restricted to the areas upstream of the dam, but should also encompass the estuary and adjacent coastal area.     

Accumulation of tin by mangrove species in West Malaysia

Information is provided concerning the concentration of tin and also of iron, copper and zinc in the leaves of mangrove species from several sites in West Malaysia. Samples collected from mangroves growing in tin-enriched waters and muds in the Kinta Valley contained elevated levels of tin compared with background sites. Freshwater streams in the Valley contained higher concentrations of tin than estuarine or marine water. Tin was also enriched in the detritus on the surface of mud beneath the mangroves. The possible use of mangroves for biogeochemical prospecting for tin is discussed.     

Copper addition by organic matter degradation in the freshwater reaches of a turbid estuary

This study reports on the relationship between copper (Cu) behavior and organic matter (OM) transformation along the turbidity gradient in the freshwater reaches of the Gironde Estuary. During a one-year survey, surface water and suspended particulate matter (SPM) were sampled at least monthly at three sites along the Garonne Branch, representing the main fluvial branch of the Gironde Estuary. Additionally, a longitudinal high resolution profile was sampled along the Garonne Branch, covering the turbidity gradient from the river water endmember to the maximum turbidity zone (MTZ). Seasonal variability and spatial distribution of Cu in both the dissolved phases (< 0.2 μm, Cu_0.2 and < 0.02 μm, Cu_0.02) and particulate Cu (Cu_P) clearly suggested Cu_0.2 addition during summer, that increased the Cu_0.2 concentrations by a factor ~ 2, mainly manifested by an increase in the Cu_0.02 fraction. At the annual timescale (2004), this internal Cu reactivity increased Cu_0.02 fluxes in the Garonne Branch by ~ 20% (3.6 t year⁻¹), with the equivalent of ~ 2.9 t year⁻¹ derived from the Cu_P fraction and ~ 0.7 t year⁻¹ from the colloidal (0.02-0.2 μm) fraction, without involving and/or affecting the Cu_C18 (hydrophobic metal-organic complexes) fraction.Combining data on Cu speciation with the results obtained by several independent techniques (DOC and POC measurements, 3D-fluorescence, and TEM) suggested close relationships between Cu behavior and OM transformation/restructuration along the turbidity gradient in the Garonne Branch. The observed Cu_0.02 addition was related to increasing humification (humification index HIX increased from 9 to 12, network formation) and labile OM degradation (Iγ/Iα ratio decreased from 0.70 to 0.44), going along with decreasing DOC and POC concentrations. Mass-balances suggest that in the studied system, degradation of OM may account for the release of ~ 25 μmol potentially bioaccessible Cu_0.02 per mole of particulate organic carbon mineralized.     

The effect of dredging in a polluted estuary on the physiology of larval zooplankton

The effect of water samples from three dredging locations in Charleston Harbor and its tributaries upon the physiology of larval or juvenile zooplankton was determined, Daphnia were used for Location 1 with a salinity of 0‰, Paleomonetes for Location II with intermediate salinities and Polydora for Location III with highest salinities. Water from the disposal area of each location was most toxic. Samples from 200 yd downstream were intermediate in effect, and the dredge site sample was least toxic.     

Effect of salinity and inorganic nitrogen concentrations on nitrification and denitrification rates in intertidal sediments and rocky biofilms of the Douro River estuary, Portugal

The regulatory effects of salinity and inorganic nitrogen compounds on nitrification and denitrification were studied in intertidal sandy sediments and rocky biofilms in the Douro River estuary, Portugal, over a 12-month period. Nitrification and denitrification rates were measured in slurries of field samples and enrichment experiments using the difluoromethane and the acetylene inhibition techniques, respectively. Salinity did not regulate denitrification in either environment, suggesting that halotolerant bacteria dominated the denitrifier communities. However, nitrification rates were stimulated when salinity increased from 0 to 15 practical salinity units. NO3- addition experiments revealed that NO3- availability stimulates denitrification rates in sandy sediments, but not in rocky biofilms; however, in rocky biofilms a positive and linear relationship was observed between denitrification rates and water column NO3- concentrations (r=0.92) during the monthly surveys. The N2O:N2 ratios increased rapidly when NO3- increased from 63 to 363 microM; however, results from monthly surveys showed that environmental parameters other than NO3- availability may be important in controlling the variation in N2O production via denitrification. Ammonium additions to sandy sediments stimulated nitrification rates by 35% for the 20 microM NH4+ addition, but NH4+ appeared to inhibit nitrification at high concentration addition (200 microM NH4+). In contrast, rocky biofilm nitrification was stimulated by 65% when 200 microM NH4+ was added.     

柔性无机矿物绝缘电缆在某公建项目的应用

以某公建项目为例,介绍柔性无杌矿物绝缘电缆与氧化镁矿物绝缘电缆的区别,柔性无机矿物绝缘电缆的选型、订货和安装注意事项.     

Antibiotic resistance in bacteria from shrimp farming in mangrove areas

Shrimp farming is a sufficiently large and mature industry to have an effective range of antimicrobial agents for most bacterial diseases in shrimp culture. However, at present, there exists great concern over the widespread use of antibiotics in aquaculture, which may result in residue of antibiotics in water and mud, and subsequently, the development of antibiotic resistance in bacteria in the environment. There is limited understanding about the effect of antibiotic residues on bacteria resistance in shrimp farming environment. Therefore, a study was conducted to investigate bacterial resistance to Norfloxacin (NFXC), Oxolinic Acid (OXLA), Trimethoprim (TMP) and Sulfamethoxazole (SMX), which were found in four shrimp farming locations in mangrove areas in Vietnam. Findings indicate that there is a relatively high incidence of bacteria resistance to these antibiotics observed in most of the studied sites, particularly to antibiotics with concentration of 0.1 microg/ml. Yet the relation between concentration of antibiotic residues and incidence of antibiotic resistance is not clearly defined. Among individual antibiotics, the incidence of resistance to TMP and SMX was higher than the others. Identification of bacteria isolated from mud samples by DNA analyzer shows that Bacillus and Vibrio are predominant among bacteria resistant to the antibiotics. The result of the study also indicates that these antibiotics in media degraded more rapidly due to the presence of resistant bacteria.     

Metals in an acid mine stream and estuary

Data on the concentrations of selected metals in the waters and sediments of an acid mine stream and its estuary are reported. The river water at the mouth is enriched in zinc, copper and manganese by at least two orders of magnitude above normal river water concentrations after having been significantly diluted by non-metalliferous tributaries. Iron is precipitated along the length of the stream while losses of copper and zinc from solution occur by adsorption onto hydrated ferric oxide above pH values of 4.5 and 6, respectively. Manganese concentrations are affected solely by dilution. The dissipation of the metalliferous river water in the marine regime is restricted, giving rise to estuarine waters containing high concentrations of copper and zinc both in solution and hydrogenous suspension. Deposition of hydrogenous material within the estuary is small, but approximately 50 % of the zinc and 90 % of the copper in the sediment is in a potentially mobile form. The environment is an unsuitable habitat for all but a few organisms.     

Reducing particle exposures in a tropical office building using electrostatic precipitators

Epidemiological surveys have shown that indoor fine particle exposures are associated with various health outcomes. Concomitantly, empirical data on the impact of electrostatic precipitation filter use on indoor particles in an office building has not been published. This research reports an intervention study on the impact of various filters within the air-handling unit (AHU) of a tropical office building. The following filtration methods were tested: (1) media filters (MED); (2) electrostatic precipitation filters (EAC); and (3) electrostatic precipitation filters enhanced with a media pre-filter (EAC-PF). The efficiencies of EAC filters were significantly superior to media filters for the removal of fine particles. Enhancement of EAC with media pre-filters (PF) augments the fine particle removal resulting in overall efficiencies comparable to that of HEPA filters. However, there was no difference in the removal efficiencies of coarse particles between MED, EAC and EAC-PF filters. When indoor particle removal effectiveness was evaluated, EAC and EAC-PF filters were more effective than MED filters for submicron particles. Further, effectiveness of EAC-PF was significantly superior to EAC due to effects of PF filtration of large particles, backpressure and lesser re-entrainment of large particles into the supply air stream. Effectiveness of EAC and EAC-PF were lower in occupied compared to non-occupied periods due to the higher particle loadings on collection plates. Using mass balance models, the results showed that effectiveness of electrostatic precipitation filters will improve as recirculation rates increase. These findings suggest that employing electrostatic precipitator filters under high recirculation rates can be an energy efficient strategy to reduce harmful indoor fine particle exposures.     

Shrimps and whitebait in the polluted Thames estuary

This paper records the seasonal incidence of shrimps, sprats and herrings, the most abundant nektonic species, off West Thurrock in the Thames estuary during 1967–70. It also deals with their age classes and their diet. The object of monitoring the shrimp fish fauna is to establish a quantitative base line against which the effects of future developments for the river, such as the erection of a barrier, can ultimately be measured. It can also serve as an index to the effects of the strike of public employees of sewage plants on the state of the river, and monitoring for this purpose continues and will be reported later.