Seasonal variability of chlorophyll-a and oceanographic conditions in Sabah waters in relation to Asian monsoon—a remote sensing study

A study was conducted to investigate the influence of Asian monsoon on chlorophyll-a (Chl-a) content in Sabah waters and to identify the related oceanographic conditions that caused phytoplankton blooms at the eastern and western coasts of Sabah, Malaysia. A series of remote sensing measurements including surface Chl-a, sea surface temperature, sea surface height anomaly, wind speed, wind stress curl, and Ekman pumping were analyzed to study the oceanographic conditions that lead to large-scale nutrients enrichment in the surface layer. The results showed that the Chl-a content increased at the northwest coast from December to April due to strong northeasterly wind and coastal upwelling in Kota Kinabalu water. The southwest coast (Labuan water) maintained high concentrations throughout the year due to the effect of Padas River discharge during the rainy season and the changing direction of Baram River plume during the northeast monsoon (NEM). However, with the continuous supply of nutrients from the upwelling area, the high Chl-a batches were maintained at the offshore water off Labuan for a longer time during NEM. On the other side, the northeast coast illustrated a high Chl-a in Sandakan water during NEM, whereas the northern tip off Kudat did not show a pronounced change throughout the year. The southeast coast (Tawau water) was highly influenced by the direction of the surface water transport between the Sulu and Sulawesi Seas and the prevailing surface currents. The study demonstrates the presence of seasonal phytoplankton blooms in Sabah waters which will aid in forecasting the possible biological response and could further assist in marine resource managements.     

Biological response to physical processes in the Indian Ocean sector of the Southern Ocean: a case study in the coastal and oceanic waters

The spatial variation of chlorophyll a (Chl a) and factors influencing the high Chl a were studied during austral summer based on the physical and biogeochemical parameters collected near the coastal waters of Antarctica in 2010 and a zonal section along 60°S in 2011. In the coastal waters, high Chl a (>3 mg m^?3) was observed near the upper layers (～15 m) between 53°30′E and 54°30′E. A comparatively higher mesozooplankton biomass (53.33 ml 100 m^?3) was also observed concordant with the elevated Chl a. Low saline water formed by melting of glacial ice and snow, as well as deep mixed-layer depth (60 m) due to strong wind (>11 ms^?1) could be the dominant factors for this biological response. In the open ocean, moderately high surface Chl a was observed (>0.6 mg m^?3) between 47°E and 50°E along with a Deep Chlorophyll Maximum of ～1 mg m^?3 present at 30–40 m depth. Melt water advected from the Antarctic continent could be the prime reason for this high Chl a. The mesozooplankton biomass (22.76 ml 100 m^?3) observed in the open ocean was comparatively lower than that in the coastal waters. Physical factors such as melting, advection of melt water from Antarctic continent, water masses and wind-induced vertical mixing may be the possible reasons that led to the increase in phytoplankton biomass (Chl a).     

Assessing the ecological effects of human impacts on coral reefs in Bocas del Toro,Panama

Environmental and biological reef monitoring was conducted in Almirante Bay (Bahía Almirante) in Bocas del Toro, Panama, to assess impacts from anthropogenic developments. An integrated monitoring investigated how seasonal temperature stress, turbidity, eutrophication and physical impacts threatened reef health and biodiversity throughout the region. Environmental parameters such as total suspended solids [TSS], carbon isotopes (δ¹³C), C/N ratios, chlorophyll a, irradiance, secchi depth, size fractions of the sediments and isotope composition of dissolved inorganic carbon [DIC] of the water were measured throughout the years 2010 and 2011 and were analysed in order to identify different impact sources. Compared to data from Collin et al. (Smithsonian Contributions to the Marine Sciences 38:324–334, 2009) chlorophyll a has doubled at sites close to the city and the port Almirante (from 0.46–0.49 to 0.78–0.97 μg l^?1) and suspension load increased, visible by a decrease in secchi depth values. Visibility decreased from 9-13 m down to 4 m at the bay inlet Boca del Drago, which is strongly exposed to river run off and dredging for the shipping traffic. Eutrophication and turbidity levels seemed to be the determining factor for the loss of hard coral diversity, most significant at chlorophyll a levels higher than 0.5 μg l^?1 and TSS levels higher than 4.7 mg l^?1. Hard coral cover within the bay has also declined, at some sites down to <10 % with extremely low diversities (7 hard coral species). The hard coral species Porites furcata dominated the reefs in highly impacted areas and showed a strong recovery after bleaching and a higher tolerance to turbidity and eutrophication compared to other hard coral species in the bay. Serious overfishing was detected in the region by a lack of adult and carnivorous fish species, such as grunts, snappers and groupers. Study sites less impacted by anthropogenic activities and/or those with local protection showed a higher hard coral cover and fish abundance; however, an overall loss of hard coral diversity was observed.     

Study on phosphorus loadings in ten natural and agricultural watersheds in subtropical region of China

Water eutrophication in subtropical regions of southern China threatens watershed health and is of major concern. However, annual phosphorus (P) loading and its dominant causes are still unclear, especially at the watershed scale. In this study, we investigated dynamic P loadings and associated factors (e.g., land use, livestock production, and runoff depth) in ten watersheds that varied in area from 9 to 5,212 ha in a hilly area of Hunan Province, China. A flowmeter was installed at the outlet of each watershed, and total P (TP) and soluble P (SP) concentrations were monitored periodically from June 2010 to October 2012. The results showed that annual P loadings (APLs) in the ten watersheds ranged from 22.8 to 247.8 kg P/km² and that P loss primarily occurred from April to June of each year during the main rainfall season in the study area. In addition, the average eutrophication (>0.05 mg P/L) ratio for stream waters was 86.7 % during the study period, which was indicative of a potentially serious condition for the local water environments. Annual P loadings were linearly related to livestock density (LD; R?=?0.92, p?<?0.01), whereas the eutrophication ratio of stream water was significantly (p?<?0.05) correlated with LD (R?=?0.61), percentage cropland (R?=?0.71), and percentage forest cover (R?=??0.68). Thus, it is concluded that the control of livestock production has the greatest potential for reducing P loadings in watersheds in this subtropical area. This will be beneficial to the amelioration and protection of local environment.     

Seasonal variations in species composition,abundance, biomass and production rate of tintinnids (Ciliata: Protozoa) along the Hooghly (Ganges) River Estuary,India: a multivariate approach

The study is the first documentation of seasonal variations in species composition, abundance and diversity of tintinnid (Ciliata: Protozoa), in relation to water quality parameters along the stretch of the Hooghly (Ganges) River Estuary (HRE), eastern coastal part of India. A total of 26 species (22 agglomerated and 4 non-agglomerated) belonging to 8 genera has been identified from 8 study sites where Tintinnopsis (17 species) represented the most dominant genera, contributing up to 65 % of total tintinnid community followed by Tintinnidium (2 species), Leprotintinnus (2 species) and Dadayiella, Favella, Metacylis, Eutintinnus and Helicostomella (each with solitary species). The maximum (1,666 ind.?l^?1) and minimum (62 ind.?l^?1) abundance of tintinnids was recorded during post-monsoon and monsoon, respectively. A distinct seasonal dynamics in terms of biomass (0.005–2.465 μg C l^?1) and daily production rate (0.04–3.13 μg C l^?1 day^?1) was also noticed, accounting highest value during pre-monsoon. Chlorophyll a and nitrate were found to be potential causative factors for the seasonal variations of tintinnids as revealed by a stepwise multiple regression model. The result of ANOVA showed a significant variation between species abundance and months (F?=?2.36, P?≤?0.05). k-dominance curves were plotted to determine the comparison of tintinnid dominance between the investigated stations. Based on a principal component analysis (PCA), three main groups were delineated with tintinnid ciliates and environmental parameters. The changes in lorica morphology in terms of temperature and salinity, recorded for three dominant species, provided information on the ecological characteristics of the species assemblage in this estuarine system.     

Distribution and sources of polycyclic aromatic hydrocarbons in the surface water of Taizi River, Northeast of China

Spatial and seasonal distribution and sources of 16 polycyclic aromatic hydrocarbons (PAHs), identified as priority pollutants by the US Environmental Protection Agency, were investigated in the surface water of the Taizi River in Liaoning Province, northeast of China. Samples were collected from the mainstream, and tributaries of the Taizi River in dry, wet, and normal seasons. Five important industrial point sources were also monitored. The total PAH concentrations ranged from 454.5 to 1,379.7 ng l^?1 in the dry season, 1,801.6 to 5,868.9 ng l^?1 in the wet season, and 367.0 to 5,794.5 ng l^?1 in the normal season. The total PAH concentrations were significantly increased in the order of wet season > normal season > dry season. The profile of PAHs in the surface water samples was dominated by low molecular weight PAHs particularly with two- and three-ring components in the three seasons, suggesting that the PAHs were from a relatively recent local source. Source identification inferred that the PAHs in the surface water of the Taizi River came from both petrogenic inputs and pyrogenic sources.     

Temporal variability in water quality parameters—a case study of drinking water reservoir in Florida, USA

Our objective was to evaluate changes in water quality parameters during 1983–2007 in a subtropical drinking water reservoir (area: 7 km²) located in Lake Manatee Watershed (area: 338 km²) in Florida, USA. Most water quality parameters (color, turbidity, Secchi depth, pH, EC, dissolved oxygen, total alkalinity, cations, anions, and lead) were below the Florida potable water standards. Concentrations of copper exceeded the potable water standard of <30 μg?l^?1 in about half of the samples. About 75 % of total N in lake was organic N (0.93 mg?l^?1) with the remainder (25 %) as inorganic N (NH₃-N: 0.19, NO₃-N: 0.17 mg?l^?1), while 86 % of total P was orthophosphate. Mean total N/P was <6:1 indicating N limitation in the lake. Mean monthly concentration of chlorophyll-a was much lower than the EPA water quality threshold of 20 μg?l^?1. Concentrations of total N showed significant increase from 1983 to 1994 and a decrease from 1997 to 2007. Total P showed significant increase during 1983–2007. Mean concentrations of total N (n?=?215; 1.24 mg?l^?1) were lower, and total P (n?=?286; 0.26 mg?l^?1) was much higher than the EPA numeric criteria of 1.27 mg total N l^?1 and 0.05 mg total P l^?1 for Florida’s colored lakes, respectively. Seasonal trends were observed for many water quality parameters where concentrations were typically elevated during wet months (June–September). Results suggest that reducing transport of organic N may be one potential option to protect water quality in this drinking water reservoir.     

Preliminary occurrence studies of antibiotic residues in Hong Kong and Pearl River Delta

An improved liquid chromatography–tandem mass spectrometry (LC-MS/MS) method was developed and validated to investigate the occurrence of selected antibiotic residues in Hong Kong and Pearl River Delta. LC and MS parameters were optimized to produce the maximum analytical responses for each compound. The established method targeted five groups of antibiotics, namely, macrolides, sulfonamides, tetracyclines, quinolones, and amphenicols. The method was validated for three types of environmental water matrices, namely, reservoir, river, and estuarine waters. Low detection limits of 0.17–0.18 ng/L for macrolides, 0.22–0.34 ng/L for quinolones, 0.67–1.65 ng/L for tetracyclines, and 0.27–0.56 ng/L for sulfonamides were obtained. No apparent interferences were observed in the chromatograms of all antibiotics groups. The developed method was preliminarily used to analyze water samples collected from Yuen Long River in New Territories, Hong Kong and four sites along the Pearl River Delta. Results showed that high level of tetracycline was found among the groups tested in the local river samples. In Pearl River Delta, we identified significant levels of erythromycin, roxithromycin, and sulfadiazine in Shenzhen Reservoir.     

Monsoon-induced changes in the size-fractionated phytoplankton biomass and production rate in the estuarine and coastal waters of southwest coast of India

Changes in the autotrophic pico- (0.2–2 μm), nano- (2–20 μm), and microplankton (>20 μm) biomass (chlorophyll a) and primary production were measured in the estuarine and coastal waters off Cochin, southwest coast of India during the onset and establishment of a monsoon. During this period, the estuary was dominated by nutrient-rich freshwater, whereas the coastal waters were characterized with higher salinity values (>30 psu) and less nutrients. The average surface chlorophyll a concentrations and primary production rates were higher in the estuary (average 13.7 mg m^???3 and 432 mgC m^???3 day^???1) as compared to the coastal waters (5.3 mg m^???3 and 224 mgC m^???3 day^???1). The nanoplankton community formed the major fraction of chlorophyll a and primary production, both in the estuary (average 85 ± SD 8.3% and 81.2 ± SD 3.2%) and the coastal waters (average 73.2 ± SD 17.2% and 81.9 ± 15.7%). Nanoplankton had the maximum photosynthetic efficiency in the coastal waters (average 4.8 ± SD 3.9 mgC mgChl a m^???3 h^???1), whereas in the estuary, the microplankton had higher photosynthetic efficiency (average 7.4 ± 7 mgC mgChl a m^???3 h^???1). The heavy cloud cover and increased water column turbidity not only limit the growth of large-sized phytoplankton in the Cochin estuary and coastal waters but also support the proliferation of nanoplankton community during the monsoon season, even though large variation in nanoplankton chlorophyll a and production exists between these two areas.     

Dissolved inorganic nutrients and chlorophyll a in an estuary receiving sewage treatment plant effluents: Cachoeira River estuary (NE Brazil)

Sampling was conducted monthly during a transition period between the dry and rainy seasons in order to evaluate the effectiveness of a municipal sewage treatment plant (STP) in eutrophication control. STP effluent and fluvial input data were also estimated. In the dry period, high concentrations of nutrients, chlorophyll a (up to 360 μg?L^?1), and anoxia in bottom waters were observed in the upper portion of the estuary. Nitrate was scarce during the dry months, although high concentrations were observed at the river sources and the upper estuary. The N:P and Si:P molar ratios were usually below 16:1, and the Si:N ratio was higher than 1:1. The fluvial inputs were a greater source of nutrients to the estuary than the STP, but nutrient loading by these effluents were also important in contributing to the eutrophication of the upper estuarine zone, especially in the dry season when symptoms were more intense.     

Heavy metal in water and aquatic organisms from different intertidal ecosystems,Persian Gulf

Intertidal ecosystems are being damaged by anthropogenic activities, particularly in the developing countries. In this study, the load of heavy metals was determined in water, fish, shrimp, and crab collected from four intertidal ecosystems, including coral reef, rocky shore, mangrove forest, and muddy habitat along the Persian Gulf coasts. Generally, the sequence of metal accumulation in the water of coral reef and mangrove forest was Ni > Pb > V > Cd > As > Hg, whereas in muddy habitats and rocky shores, the sequence was Ni > Pb > V > Cd > Hg > As and Ni > V > Pb > As > Hg > Cd, respectively. Water of the coral reef had the highest level of Ni (97.44 μg l^?1), Pb (3.92 μg l^?1), V (10.42 μg l^?1), Cd (3.92 μg l^?1), As (1.87 μg l^?1), and Hg (0.74 μg l^?1). For the most part, the highest concentrations of the studied metals were found in the liver and the gills of Johnius belangerii and the hepatopancreas of Portunus pelagicus and Metapenaus affinis collected from the coral reef ecosystem.     

Native plant restoration combats environmental change: development of carbon and nitrogen sequestration capacity using small cordgrass in European salt marshes

Restoration of salt marshes is critical in the context of climate change and eutrophication of coastal waters because their vegetation and sediments may act as carbon and nitrogen sinks. Our primary objectives were to quantify carbon (C) and nitrogen (N) stocks and sequestration rates in restored marshes dominated by Spartina maritima to provide support for restoration and management strategies that may offset negative aspects of eutrophication and climate change in estuarine ecosystems. Sediment C content was between ca. 13 mg C g^?1and sediment N content was ca. 1.8 mg N g^?1. The highest C content for S. maritima was recorded in leaves and stems (ca. 420 mg C g^?1) and the lowest in roots (361?±?4 mg C g^?1). S. maritima also concentrated more N in its leaves (31?±?1 mg N g^?1) than in other organs. C stock in the restored marshes was 29.6 t C ha^?1; ca. 16 % was stored in S. maritima tissues. N stock was 3.6 t N ha^?1, with 8.3 % stored in S. maritima. Our results showed that the S. maritima restored marshes, 2.5 years after planting, were sequestering atmospheric C and, therefore, provide some mitigation for global warming. Stands are also capturing nitrogen and reducing eutrophication. The concentrations of C and N contents in sediments, and cordgrass relative cover of 62 %, and low below-ground biomass (BGB) suggest restored marshes can sequester more C and N. S. maritima plantations in low marshes replace bare sediments and invasive populations of exotic Spartina densiflora and increase the C and N sequestration capacity of the marsh by increasing biomass production and accumulation.     

Biogeochemical responses to nutrient inputs in a Cuban coastal lagoon: runoff, anthropogenic, and groundwater sources

Laguna Larga, a coastal lagoon in central Cuba, has been heavily altered by tourism infrastructure construction and sewage disposal. We hypothesize that this has decreased the circulation and caused eutrophication of the lagoon. To assess this, 12 bimonthly samplings were carried out in 2007–2008. Temperature, salinity, oxygen, nutrients and nitrogen, and phosphorous fractions (inorganic, organic, and total) were determined. Water and salt budgets, as well as biogeochemical fluxes of nitrogen and phosphorus were calculated using the LOICZ budget model for the three sections of the lagoon identified by morphological constrains and salinity patterns. Laguna Larga is a choked lagoon with restricted water circulation, low exchange, and high residence times that vary significantly along its sections. Residence time was estimated to be 0.1–0.7 years for the inner section and 1–9 days for the outer one. High levels of total nitrogen (annual means 126–137 μM, peaks up to 475 μM) and phosphorus (2.5–4.4 μM, peaks up to 14.5 μM) are evidence of eutrophication of Laguna Larga. During 2007, an average precipitation year, Laguna Larga exported water (703 m³ d^?1) and was a source of nitrogen (9.026 mmol m^?2 d^?1) and phosphorus (0.112 mmol m^?2 d^?1) to the adjacent sea. δ¹⁵N determinations in the seagrass Thalassia testudinum (?1.83 to +3.02?‰) differed significantly between sites in the lagoon and offshore reference sites located W of the inlet, but were similar to those located E of the inlet. δ¹⁵N determinations in the seaweed Penicillus dumetosus (+1.02 to +4.2) did not show significant differences.     

Seasonal variation in physicochemical properties of coastal waters of Kalpakkam, east coast of India with special emphasis on nutrients

A study pertaining to the seasonal variation in physicochemical properties of the coastal waters was carried out at Kalpakkam coast for a period of 1 year (February 2006 to January 2007). It revealed that the coastal water was significantly influenced by freshwater input during North East (NE) monsoon and post-monsoon periods. Concentration of all the nutrients and dissolved oxygen (DO) was relatively high during the NE monsoon, whereas, salinity and chlorophyll-a (chl-a) were at their minimum level during this period. Phytoplankton production peak was observed in summer during which a typical marine condition prevailed. The present observed values of nitrate, phosphate, silicate, and turbidity are significantly high (five to ten times) compared to that of the pre-Tsunami period from this coast. Relatively low DO and chl-a concentration was noticed during the post-Tsunami period. A notable feature of this study is that though nutrient concentration in the coastal waters during post-Tsunami period has increased significantly, turbidity, the most single dominating factor, was found to adversely affect the phytoplankton production during post-Tsunami period as reflected by relatively low chl-a concentration. Thus, the post-Tsunami period may result in a change in coastal biodiversity pattern concomitant with change in coastal water quality.     

Spatial distribution and seasonal variation of polycyclic aromatic hydrocarbons (PAHs) contaminations in surface water from the Hun River, Northeast China

The objectives of this study were to investigate the levels, dispersion patterns, seasonal variation, and sources of 16 priority polycyclic aromatic hydrocarbons (16 EPA-PAHs) in the Hun River of Liaoning Province, China. Samples of surface water were collected from upstream to downstream locations, and also from the main tributaries of the Hun River in dry period, flood period, and level period, respectively. After appropriate preparation, all samples were analyzed for 16 EPA-PAHs. Total PAHs concentrations varied from 124.55 to 439.27 ng l^?1 in surface water in dry period, 1,615.75 to 5,270.04 ng l^?1 in flood period, and 2,247.42 to 7,767.9 ng l^?1 in level period. The 16 EPA-PAHs concentrations were significantly increased in the order of level period > flood period > dry period. The composition pattern of PAHs in surface water was dominated by low molecular weight PAHs, in particular two- to three-ring PAHs. In addition, two-ring PAH accounted for 39.33 to 88.27 % of the total PAHs in level period. Low molecular weight PAHs predomination together with higher levels of PAHs in flood and level period suggested a relatively recent local source of PAHs. Special PAHs ratios such as phenanthrene/anthracene and fluoranthene/pyrene indicated that under dry weather season conditions, the PAHs found in surface water were primarily from petrogenic source, while under wet weather season conditions they were from mixed source of both petrogenic inputs and combustion sources. The comparison of PAHs contamination among different types of areas in China suggested that atmospheric depositions might be the most important approaches of PAHs into water system. Although the Hun River exists low PAHs ecological risk now, potential toxic effects will be existed in the future especially in flood and level period.     

Impacts of climate-induced changes on the distribution of pesticides residues in water and sediment of Lake Naivasha, Kenya

This study reports evidence of increased chlorpyrifos contamination in sediment and water in Lake Naivasha following its intensive application in the horticultural farms in the catchment area. Analytical results show that levels of chlorpyrifos residues were influenced by climate-induced rainfall pattern with higher levels reported during period of heavy precipitation with significant decrease during low rainfall. On average, the levels ranged between 14.8 and 32.8 ng g^?1 in sediment during rainy season compared to a range of 8.5–16.6 ng g^?1 in the dry season. Additionally, the mean concentration of chlorpyrifos in water ranged between 8.61 and 22.4 μg L^?1 during rainy season and below detection limit (bdl) ?13.6 μg L^?1 in dry season as quantified by enzyme-linked immunosorbent assay. Meanwhile, independent t test analysis indicated that there was significant difference in concentration at p?≤?0.05 between the seasons with respect to sediment and water samples. This demonstrated that climate-induced variations had considerable influence on contamination. While diazinon and carbofuran were equally applied intensively, their levels were below the detection limit in the all the samples analyzed. ELISA results were validated by the capillary-HPLC photodiode-array detector instrument analysis, and statistical comparison showed no significant difference between them. It was evident that chlorpyrifos residues determination in water and sediment by ELISA can be a useful strategy in environmental management and monitoring program, and a complimentary analytical tool to high performance liquid chromatography. Levels of chlorpyrifos detected in sediment and water were found to exceed recommended criteria for protection of aquatic life and preservation of water quality and may be hazardous if not regularly monitored.     

Fate of selenium in a small urban watershed

A field study was conducted on a small urban watershed (residential and golf course dominated) in southern Nevada to assess the concentration and speciation of selenium (Se) in a series of drain lines and monitoring wells and to quantify the mass discharge of Se from the drain system. Water samples were collected on a monthly basis and analyzed for total Se, selenate (SeO₄ ⁼) and selenite (SeO₃ ⁼). In addition, where possible, flow was assessed as was, temperature, redox potential, pH, dissolved oxygen (DO) along with all major cations and anions. The data were then modeled with PhreeqC to identify selenium speciation. Results revealed a SeO₄ ⁼ dominated system with SeO₄ ⁼ concentrations ranging from 13 to 62 ppb. In the monitoring wells, 66 % of the variation in the total Se concentration could be described based on depth to groundwater, temperature and sulfate concentrations (P?<?0.001). In particular, higher total Se concentrations were predicted for shallower depth to groundwater, suggesting the solubilization of Se evapo-concentrates near the surface could be reduced by lowering water tables. The highest of all correlations was found between SeO₄ ⁼ concentrations (↑) and the sodium (↑) and DO (↑) concentrations in the monitoring wells (R ²?=?0.77, P?<?0.001). An excellent curvilinear relationship was found between total Se and the electrical conductivity in the water (R ²?=?0.73, P?<?0.001). Based on the Se data and time line identified in this study, high concentrations of Se could be expected to drain from this area for many years to come, with salinity acting as a good proxy for Se concentration. In the drain lines, Se concentrations were found to be invariant to flow (P?>?0.05). Flow discharge from the main drain system to the Las Vegas Wash was estimated at 559 acre feet during the 1 year study period. This flow was estimated to carry 4,203 Mg of salts 6.71 Mg of nitrate-N and 27.1 kg of total Se.     

Influences of urban wastewaters on the stream water quality: a case study from Gumushane Province, Turkey

Urban wastewater in Turkey is primarily discharged without treatment to marine environments, streams and rivers, and natural and artificial lakes. Since it has been well established that untreated effluent in multi-use waters can have acute and chronic impacts to both the environment and human health, it is important to evaluate the consequences of organic enrichment relative to the structure and function of aquatic environment. We investigated the impacts of untreated municipal wastewater discharge from the city of Gumushane in the Eastern Black Sea Region of Turkey on the surface water quality of the stream Harsit. Several key water-quality indicators were measured: chemical oxygen demand (COD), ammonium nitrogen (NH ₄ ⁺ –N), nitrite nitrogen (NO ₂ ^? –N), nitrate nitrogen (NO ₃ ^? –N), total Kjeldahl nitrogen (TKN), total nitrogen (TN), orthophosphate phosphorus (PO ₄ ^3? –P), methylene blue active substances (MBAS), water temperature (t), pH, dissolved oxygen (DO), and electrical conductivity (EC). The monitoring and sampling studies were conducted every 15 days from March 2009 to February 2010 at three longitudinally distributed stations. While t, pH, DO, and EC demonstrated relatively little variability over the course of the study, other parameters showed substantial temporal and spatial variations. The most dramatic differences were noted in COD, NH ₄ ⁺ –N, NO ₂ ^? –N, TKN, TN, PO ₄ ^3— P, and MBAS immediately downstream of the wastewater discharge. Concentration increases of 309 and 418 % for COD, 5,635 and 2,162 % for NH ₄ ⁺ –N, 2,225 and 674 % for NO ₂ ^? –N, 283 and 478 % for TKN, 208 and 213 % for PO ₄ ^3? –P, and 535 and 1,260 % for MBAS were observed in the summer and autumn, respectively. These changes were associated with greatly diminished seasonal stream flows. Based on NO ₂ ^? –N, TKN, PO ₄ ^3— P, and MBAS concentrations, it was concluded that Harsit stream water was correctly classified as polluted. The most telling parameter, however, was NH ₄ ⁺ –N, which indicated highly polluted waters in both the summer and autumn. The elevated concentrations of both P and N in the downstream segment of the stream triggered aggressive growth of submerged algae. This eutrophication of river systems is highly representative of many urban corridors and is symptomatic of ongoing organic enrichment that must be addressed through improved water treatment facilities.     

Calibration and verification of a dissolved oxygen management model for a highly polluted river with extreme flow variations in Pakistan

A dissolved oxygen (DO) model is calibrated and verified for a highly polluted River Ravi with large flow variations. The model calibration is done under medium flow conditions (431.5 m³/s), whereas the model verification is done using the data collected during low flow conditions (52.6 m³/s). Biokinetic rate coefficients for carbonaceous biochemical oxygen demand (CBOD) and nitrogenous biochemical oxygen demand (NBOD) (i.e, K _cr and K _n ) are determined through the measured CBOD and ammonia river profiles. The calculated values of K _cr and K _n are 0.36 day^?1 and 0.34 day^?1, respectively. The close agreement between the DO model results and the field values shows that the verified model can be used to develop DO management strategies for the River Ravi. The biokinetic coefficients are known to vary with degree of treatment (DOT) and therefore need to be adjusted for a rational water quality management model. The effect of this variation on level of treatment has been evaluated by using the verified model to attain a DO standard of 4 mg/L in the river using the biokinetic rate coefficients as determined during the model calibration and verification process. The required DOT in this case is found to be 96 %, whereas the DOT is 86 % if adjusted biokinetic rate coefficients are used to reflect the effect of wastewater treatment. The cost of wastewater treatment is known to increase exponentially as the removal efficiency increases; therefore, the use of appropriate biokinetic coefficients to manage the water quality in rivers is important.     

Study on water quality and genotoxicity of surface microlayer and subsurface water in Guangzhou section of Pearl River

In order to understand the water quality and the genotoxicity of various surfaces in the Guangzhou section of the Pearl River during January to December of 2008, we investigated and studied the current water situation of the surface microlayer (SML) and the subsurface water (SSW) in Guanzhou section (Zhongda Dock and Yuzhu Dock) of the Pearl River by chemical analysis and biological monitoring method (Vicia faba micronucleus test). The results showed that during these months concentrations of the indexes of the two docks water such as total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (COD) exceeded the national III level of surface water quality, and the indexes of SML were much higher than the ones of SSW (P?< 0.05), and the exceeding rate of TN, TP of SML was 100%. According to the eutrophic evaluation standard, the water bodies of SML and SSW in the two docks were in a eutrophication during these months. The eutrophication and pollution of SML was more serious, and the highest index of eutrophication (E value) was up to 81.9, which also had obvious difference with COD and TP (P?< 0.05). The water of SML in the two docks enriched to N, P, and chlorophyll a (Chl. a) seriously, and the enrichment factor of SML in Zhongda Dock to N, P, and Chl. a was 0.71 ?? 2.78, 0.98 ?? 1.18, and 0.49 ?? 13.99, respectively, and the one in the Yuzhu Dock was 1.09 ?? 1.52, 1 ?? 1.14, and 0.72 ?? 4.07, respectively. Through inspecting the water genotoxicity of various layers by V. faba micronucleus test, we could know that the average annual MCN?? of SML and SSW in the two docks was 6.09??, 5.53??, 5.57??, and 5.249??, respectively. In general, the above value of SML was a little higher than the one of SSW, but there was not a remarkable difference (P?> 0.05). This research shows that the water quality in a medium to heavy eutrophication in the Guangzhou section of Pearl River belongs to national III ?? IV level, and SML has the capability of enrichment to the pollutants such as N and P and induces the increase of micronucleus rate of V. faba tip cell. The study also indicates that there may be genotoxicity matters such as N, P in water body.