Variability of dissolved reactive phosphate and apparent oxygen utilization along the west coast of India

This work focuses on the spatial variability of dissolved reactive phosphate along the west coast of India. In this study, samples of surface and bottom water was collected from each of the 27 sites during a single pre-monsoon transect along the west coast of India to study the variation of dissolved reactive phosphate. Phosphate showed an enrichment pattern with increase in depth of the water column. In addition to this, an offshore increase in phosphate concentrations was noticed for both surface and bottom stations. Almost all the surface stations of this study area were found to be characterized by negative apparent oxygen utilization (AOU) values, and bottom stations of the deeper offshore zone (200 m depth) displayed large positive AOU values. The bottom stations of shallow near coastal waters and the deeper offshore zone are characterized by an inverse relationship between phosphate and dissolved oxygen, whereas at these depths, a direct relation was observed between phosphate and AOU. AOU is calculated as the difference between oxygen saturation value at the in situ temperature and salinity and the actual measured concentration. This oxidative re-mineralization mechanism decreases the observed dissolved oxygen well below the expected theoretical values, which is concordant with the higher concentration of phosphate and high positive AOU values.     

Urbanization and small household agricultural land use choices in the Brazilian Amazon and the role for the water chemistry of small streams

Many small watersheds and streams in the Brazilian Amazon have been impacted by agriculture and urban development, often due to household economic needs and migration processes. This study examined the relationships between land use, soil type, and household factors on stream water chemistry in and near the city of Altamira, Pará, Brazil, in 2008–2009. While soil weathering and stream discharge may have affected several stream water ion concentrations, agriculture and especially urban development were associated with high dissolved nitrogen concentrations, high water temperatures, and low dissolved oxygen concentrations in streams. Younger interviewed households were generally associated with these watersheds, and many urban residents reported disposing of household waste directly into streams. In contrast, older households were generally associated with forest and cocoa agriculture, along with lower water temperatures and higher dissolved oxygen concentrations in streams. These conditions persisted despite reported uses of herbicides and fertilizers by some residents.     

Applications of Venturi Principle to Water Aeration Systems

The concentration of dissolved oxygen is an important indicator of water quality because aquatic life lives on the dissolved oxygen in the water. Aeration can increase dissolved oxygen when levels become deficient. Hydraulic structures can significantly improve dissolved oxygen levels by creating turbulent conditions where small air bubbles are carried into the bulk of the flow. Recent researches have focused on developing measurement and predictive techniques for oxygen transfer at hydraulic structures to maintain and enhance water quality. However, reviewing existing studies on aeration performance of hydraulic structures, it seems that there are not too many studies on venturi aeration. The present paper shows applications of venturi principle to water aeration systems. The aeration characteristics of venturi nozzle, venturi conduit and venturi weir are analyzed. The results indicate that venturi aeration might contribute significantly to air entrainment and aeration efficiency. Therefore, venturi device can be used as highly effective aerator in aeration processes.     

海河冬季溶解氧升高原因分析

分析了近两年来海河三岔口断面的水质状况;介绍了地表水中溶解氧的一般变化规律,分析了海河三岔口段溶解氧一年中的变化趋势,特别是在冬季溶解氧偏高的原因。     

Study of physico-chemical characteristics of water bodies around Jaipur

The present study has been undertaken to evaluate physico-chemical parameters (pH, temperature, dissolved oxygen, free carbon dioxide, alkalinity and hardness) and zinc concentration in water bodies in and around Jaipur. Water samples from Jalmachal Lake, Nevta Lake, Amer Lake and Ramgarh Lake were analysed. Results reveal that the water of Jalmahal Lake is most polluted due to high pH, hardness, alkalinity, free carbon dioxide, zinc content, and a low level of dissolved oxygen. Contrarily Ramgarh Lake is least polluted, as it has high dissolved oxygen and low pH, alkalinity, free carbon dioxide, hardness and zinc content.     

Estimation of stream temperature in firtina creek (Rize-Turkiye) using artificial neural network model

Water temperature is one of the most important environmental variables in aquatic ecosystem. Temperature changes may have positive or negative effects on organisms. High water temperatures have caused mortalities in salmonid fishes. Therefore, monitoring and prediction of potential adverse changes in water temperature is very important. Here, we have developed and tested an artificial neural network (ANN) model to predict stream temperature of Firtina Creekin Black Sea region; using local water temperature, dissolved oxygen, pH and other available meteorological data (air temperature, rainfall). Thus, enabling define suitable habitat for native Sea Trout (Salmo trutta labrax, Pallas 1811) under past drought or other adverse envIronmental conditions.     

鄱阳湖沉积物中磷吸附释放特性及影响因素研究

沉积物是氮磷营养盐的主要蓄积库,它不仅是外来污染物的归宿地,同时其自身营养盐的释放也可对水环境产生重大影响。针对鄱阳湖存在的沉积物磷释放问题,关键环境因子对基质磷吸附的影响规律进行了探讨。通过控制在不同环境因素条件下,上覆水中磷的变化规律探讨,阐明磷在上覆水-底泥界面迁移转化的规律和环境因素对迁移转化过程的影响。研究结果表明,吸附初始阶段,两者含量相差较大,起始吸附速率很高;随着反应时间的推进,两者含量差随之减小;当吸附时间达到30 min时,此时上覆水的平衡质量浓度为8.648 mg·L^-1,两者含量达成平衡。由磷的吸附等温试验同样可看出,随着平衡质量浓度逐渐增加,土壤吸磷量刚开始增加较快,随后增加趋势逐渐减缓直至磷饱和。pH越小,上覆水质量浓度越低,沉积物对磷的吸附作用越强;pH越大,上覆水中TP质量浓度越大,强碱条件下,TP吸收量剧减。在好氧条件下,沉积物对磷的吸附远远高于厌氧条件下沉积物的吸附。好氧条件下,反应在4 h内,沉积物对磷的吸附速率最高,随后吸附量很小直至逐渐饱和。厌氧条件下,吸附作用不明显;当反应时间达到24 h后,上覆水磷质量浓度保持不变,此时沉积物磷吸附达到饱和。高溶解氧水平对于控制底泥向上覆水体释放磷,维持水体较低总磷是必要的。温度为30℃,20℃和5℃3种条件下,当反应24 h后,三者均达到吸附平衡。因此,当上覆水的磷质量浓度较低时,高温条件下基质的磷释放速度会高于低温条件下的磷释放速度。研究结果旨在为正确认识、合理评估环境因素对湖泊水体磷的影响提供更为充分恰当的试验依据和理论解释。     

Effects of oxygen and inorganic carbon concentrations on the photosynthetic quotients of marine algae

The photosynthetic quotients of the marine prymnesiophyte Pavlova lutheri and the marine dinoflagellate Glenodinum sp. were measured at different concentrations of dissolved oxygen and inorganic carbon. Dissolved oxygen concentration appeared to be the most important factor controlling the photosynthetic quotient. Photosynthetic quotients generally were between 1.0 and 1.8 at oxygen concentrations less than saturation, were approximately 1.0 at oxygen saturation, and generally were from 0.1 to 1.0 at oxygen concentrations greater than saturation. The photosynthetic quotients greater than 1.0 were not caused by lipid synthesis. They may have been partially caused by the presence of KNO₃ rather than an ammonium salt in the growth media. The lowered photosynthetic quotients at higher oxygen concentrations were probably caused by algal photorespiration.Contribution No. 202 from the Department of Biology, The Pennsylvania State University; 202 Buckhout Laboratory, University Park, Pennsylvania 16802, USA     

Analysis of spatial and temporal patterns in a large reservoir using water quality and hydrodynamic modeling

Effective management of reservoir water resources demands a good command of ecological processes in the waterbody. In this work the three-dimensional finite element hydrodynamic model RMA10 was coupled to an eutrophication model. The models were used together with a methodology for loads estimation to foster the understanding of such processes in the largest reservoir in Western Europe—the Alqueva. Nutrient enrichment and eutrophication are water quality concerns in this man-made impoundment. A total phosphorus and nitrogen loads quantification methodology was developed to estimate the inputs in the reservoir, using point and non-point source data.Field data (including water temperature, wind, water elevation, chlorophyll-a, nutrient concentration and dissolved oxygen) and estimated loads were used as forcing for simulations.The analysis of the modeling results shows that spatial and temporal distributions for water temperature, chlorophyll-a, dissolved oxygen and nutrients are consistent with measured in situ data.Modeling results allowed the identification of likely key impact factors on the water quality of the Alqueva reservoir. It is shown that the particular geomorphological and hydrological characteristics of the reservoir together with local climate features are responsible for the existence of distinct ecological regions within the reservoir.     

Water quality monitoring in a slightly-polluted inland water body through remote sensing — Case study of the Guanting Reservoir in Beijing, China

This study focused on the water quality of the Guanting Reservoir, a possible auxiliary drinking water source for Beijing. Through a remote sensing (RS) approach and using Landsat 5 Thematic Mapper (TM) data, water quality retrieval models were established and analyzed for eight common water quality variables, including algae content, turbidity, and concentrations of chemical oxygen demand, total nitrogen, ammonia nitrogen, nitrate nitrogen, total phosphorus, and dissolved phosphorus. The results show that there exists a statistically significant correlation between each water quality variable and remote sensing data in a slightly-polluted inland water body with fairly weak spectral radiation. With an appropriate method of sampling pixel digital numbers and multiple regression algorithms, retrieval of the algae content, turbidity, and nitrate nitrogen concentration was achieved within 10% mean relative error, concentrations of total nitrogen and dissolved phosphorus within 20%, and concentrations of ammonia nitrogen and total phosphorus within 30%. On the other hand, no effective retrieval method for chemical oxygen demand was found. These accuracies were acceptable for the practical application of routine monitoring and early warning on water quality safety with the support of precise traditional monitoring. The results show that performing the most traditional routine monitoring of water quality by RS in relatively clean inland water bodies is possible and effective.     

Oxygen supply in aquatic ectotherms: partial pressure and solubility together explain biodiversity and size patterns

Aquatic ectotherms face the continuous challenge of capturing sufficient oxygen from their environment as the diffusion rate of oxygen in water is 3 x 10(5) times lower than in air. Despite the recognized importance of oxygen in shaping aquatic communities, consensus on what drives environmental oxygen availability is lacking. Physiologists emphasize oxygen partial pressure, while ecologists emphasize oxygen solubility, traditionally expressing oxygen in terms of concentrations. To resolve the question of whether partial pressure or solubility limits oxygen supply in nature, we return to first principles and derive an index of oxygen supply from Fick's classic first law of diffusion. This oxygen supply index (OSI) incorporates both partial pressure and solubility. Our OSI successfully explains published patterns in body size and species across environmental clines linked to differences in oxygen partial pressure (altitude, organic pollution) or oxygen solubility (temperature and salinity). Moreover, the OSI was more accurately and consistently related to these ecological patterns than other measures of oxygen (oxygen saturation, dissolved oxygen concentration, biochemical oxygen demand concentrations) and similarly outperformed temperature and altitude, which covaried with these environmental clines. Intriguingly, by incorporating gas diffusion rates, it becomes clear that actually more oxygen is available to an organism in warmer habitats where lower oxygen concentrations would suggest the reverse. Under our model, the observed reductions in aerobic performance in warmer habitats do not arise from lower oxygen concentrations, but instead through organismal oxygen demand exceeding supply. This reappraisal of how organismal thermal physiology and oxygen demands together shape aerobic performance in aquatic ectotherms and the new insight of how these components change with temperature have broad implications for predicting the responses of aquatic communities to ongoing global climate shifts.     

Results of the UNDP (SF)/FAO Regional Fisheries Survey in West Africa. report No. 2. Preliminary note on dissolved oxygen in the Canary Current

While examining historical data on dissolved oxygen in the Canary Current area and the Central Atlantic Ocean (areas of activity of the UNDP/FAO Regional Fisheries Survey in West Africa), a quite different pattern of distribution was found in the dissolved oxygen/water temperature relationship in two adjacent Marsden squares (MS)¹, 074 and 038. Not only were the dissolved oxygen values in MS 038 considerably lower than in MS 074 but, in the former square, the oxgen/temperature distribution showed 2 dissolved oxygen minima, the latter only 1 minimum. In MS 335, situated below the Equator, near the African coast, the oxygen/temperature distribution differs from the two former squares in that the dissolved oxygen value decreased steadily, and no oxygen minimum was found down to a depth where the water temperature was 6°C.     

Behavioral response of fish larvae to low dissolved oxygen concentrations in a stratified water column

Density stratification and respiration lead to vertical gradients in dissolved oxygen in many aquatic habitats. The behavioral responses of fish larvae to low dissolved oxygen in a stratified water column were examined during 1990–1991 with the goal of understanding how vertical gradients in dissolved oxygen may directly affect the distribution and survival of fish larvae in Chesapeake Bay, USA. In addition, the effects of low oxygen on 24-h survival rates were tested so that results of behavior experiments could be interpreted in the context of risk to the larve. Naked goby [Gobiosoma bosc (Lacépède)] and bay anchovy [Anchoa mitchilli (Valenciennes)] larvae strongly avoided dissolved oxygen concentrations <1 mg 1^-1, which were lethal within 24 h at 25 to 27°C. In addition, naked goby larvae, whose behavior was tested at a wider range of dissolved oxygen concentrations, also showed a reduced preference for an oxygen concentration of 2 mg 1^-1, which leads to reduced survival during long-term exposures and to reduced feeding rates. There were no major differences in behavior or survival between the two species, or between the two age classes of naked gobies tested. Results suggest that behavioral responses to oxygen gradients will play a large role in producing marked vertical changes in abundance of feeding-stage larvae in Chesapeake Bay; mortality from direct exposure to low oxygen will likely be much less important in producing vertical patterns of larval abundance.     

Nitrogen export from an agriculture watershed in the Taihu Lake area, China

Temporal changes in nitrogen concentrations and stream discharge, as well as sediment and nitrogen losses from erosion plots with different land uses, were studied in an agricultural watershed in the Taihu Lake area in eastern China. The highest overland runoff loads and nitrogen losses were measured under the upland at a convergent footslope. Much higher runoff, sediment and nitrogen losses were observed under upland cropping and vegetable fields than that under chestnut orchard and bamboo forest. Sediment associated nitrogen losses accounted for 8-43.5% of total nitrogen export via overland runoff. N lost in dissolved inorganic nitrogen forms (NO(3-)-N + NH4+-N) accounted for less than 50% of total water associated nitrogen export. Agricultural practices and weather-driven fluctuation in discharge were main reasons for the temporal variations in nutrient losses via stream discharge. Significant correlation between the total nitrogen concentration and stream discharge load was observed. Simple regression models could give satisfactory results for prediction of the total nitrogen concentrations in stream water and can be used for better quantifying nitrogen losses from arable land. Nitrogen losses from the studied watershed via stream discharge during rice season in the year 2002 were estimated to be 10.5 kg N/ha using these simple models.     

苯酚的超临界水氧化试验

以自建的一套连续式超临界水氧化装置的温度，压力，溶氧量和流量等参数的可控性进行了实验，并在此基础上进行了苯酚的超临界水氧化研究。结果表明：所建立的装置能比较精确控制各种条件参数，是可靠的超临界水氧化试验研究装置。在氧气过量的条件下，停留时间是影响苯酚在超临界水中氧化分解的主要因素，反应的温度和压力升高导致苯致苯酚去除率的增大，只要有足够的氧气，苯酚起始浓度的增加对苯酚的转化率影响不明显，在实验条件下，溶液中苯酚的去除动力学对苯酚是一级，氧气是零级。     

Nitrogen saturation in stream ecosystems

The concept of nitrogen (N) saturation has organized the assessment of N loading in terrestrial ecosystems. Here we extend the concept to lotic ecosystems by coupling Michaelis-Menten kinetics and nutrient spiraling. We propose a series of saturation response types, which may be used to characterize the proximity of streams to N saturation. We conducted a series of short-term N releases using a tracer (15NO3-N) to measure uptake. Experiments were conducted in streams spanning a gradient of background N concentration. Uptake increased in four of six streams as NO3-N was incrementally elevated, indicating that these streams were not saturated. Uptake generally corresponded to Michaelis-Menten kinetics but deviated from the model in two streams where some other growth-critical factor may have been limiting. Proximity to saturation was correlated to background N concentration but was better predicted by the ratio of dissolved inorganic N (DIN) to soluble reactive phosphorus (SRP), suggesting phosphorus limitation in several high-N streams. Uptake velocity, a reflection of uptake efficiency, declined nonlinearly with increasing N amendment in all streams. At the same time, uptake velocity was highest in the low-N streams. Our conceptual model of N transport, uptake, and uptake efficiency suggests that, while streams may be active sites of N uptake on the landscape, N saturation contributes to nonlinear changes in stream N dynamics that correspond to decreased uptake efficiency.     

Effect of enclosure in large plastic bags on diurnal change in oxygen concentration in tropical ocean water

From November 1980 to February 1981 the concentration of oxygen dissolved in the surface mixed layer of the oligotrophic Caribbean Sea off Curaçao was quite constant (420.77±1.98 g at l^-1). However, immediately following enclosure in 4500-1 plastic bags reaching to a depth of 5 m the oxygen concentration began to decrease, down to values below saturation (405 g at l^-1) within 48 h. Autotrophic and heterotrophic nanoplankton cell numbers and algal pigments in bags remained constant or increased slightly during the first 24 h of enclosure. The rate of decrease in oxygen concentration in bags was significantly higher during daylight hours than in the night, which suggests that photo-oxidative processes were involved in the additional daytime loss of oxygen. The dramatic enclosure effect on the oxygen content of the water in the bags can be taken as evidence of the dependence of the oxygen concentration near the tropical ocean's surface on supply from below: in water freely circulating in the euphotic zone deviations from the mean oxygen concentration during a diurnal cycle were 0.47% at most, differential losses near the surface being counteracted through vertical exchange; while in water separated from the rest of the mixed layer in the plastic bags losses due to respiration of the enclosed plankton community plus an even greater loss, assigned to non-biological, photosensitized oxidation processes, were up to 10 g at O₂ l^-1 in 24 h. Although photo-oxidation is confined to the very surface the oxygen flux involved may be important enough to necessitate consideration of a photochemically induced loss factor in oxygen budget calculations, e.g. when primary production is to be estimated from diurnal oxygen curves.     

Acute nitrate poisoning in two cattle

Abstract

The rate and product composition during photooxidation of aromatic hydrocarbons (toluene, o‐, m‐, p‐xylene and cumene) dissolved in n‐hexane and spread as a liquid film on water is reported. The photo degradability of these chemicals is 10–20%. The products identified are oxygenated aromatic compounds. It is observed that the absorption bands of the compounds under investigation depend upon the partial pressure of dissolved oxygen and these bands extend up to 290 nm. The new absorption band around 290 nm is probably due to broadening of ¹L_b bands which is responsible for direct photolysis.

stream. We have been especially interested in investigating the rate of disappearance and distribution of main oxidation products in two phases. Besides that an attempt has been made to throw some light on the reaction mechanism.     

On-line determination of respiration rates of aquatic organisms in a mono-phase oxystat at steady-state dissolved oxygen tensions

On-line determination of respiration rates at steady-state dissolved oxygen tensions was performed in a thermostatted measuring chamber equipped with a galvanic oxygen electrode. The measuring chamber is designed to completely exclude gas bubbles from the liquid phase and is named a mono-phase oxystat. Additions of oxygenated water to maintain steady-state dissolved oxygen tensions are controlled by a computer, and the respiration rate is determined from the rate of these additions. An external loop with a flow cell in a spectrophotometer makes it possible to determine and control the concentration of algal cells in the mono-phase oxystat and allowed simultaneous determination of respiration and filtration rates of filter-feeding invertebrates. Because the system maintains steady-state conditions the experiments do not suffer from time limitations. The response time of the system is negligible compared to the response time of other open systems. Received: 7 November 1996 / Accepted: 6 December 1996     

Gender- and oxygen-related irrigation behaviour of the decapod Nephrops norvegicus

The Norway lobster Nephrops norvegicus (L.) inhabits burrows in muddy clay sediments (e.g. on the Swedish west coast), where an autumnal oxygen deficiency in the bottom water can occur. Our experiments investigated whether the irrigation of the burrows would reflect a behavioural adaptation to hypoxia, and whether any gender differences of such behaviour exist. Irrigation is performed by the pleopods which may compensate for a decreasing oxygen tension. Pleopod activity (total number of strokes per sampling time), associated with oxygen concentration and gender, was studied in N. norvegicus kept in artificial burrows resembling their natural habitat. Male and female lobsters were separately exposed to either normoxia (70% oxygen saturation) or hypoxia (30% oxygen saturation). A sexual difference in behaviour was found, where females irrigated the burrow less than males during normoxia. Females showed a significant increase of pleopod activity in hypoxia compared with normoxic conditions, which was not displayed by the males probably due to the degree of individual variation found. However, when only males were studied during progressive hypoxia (from 60 to 5% oxygen saturation), following any changes of irrigational behaviour, a significant increase of accumulated pleopod activity occurred. A major increase of pleopod activity appeared between 60 and 50% oxygen saturation, below which the activity remained high until a critical point (<10% saturation, 11 °C, 33 psu) where irrigation dropped to a level close to that of normoxic values. Activity sessions during hypoxia were longer and had a higher stroke rate than during normoxia. Received: 22 October 1997 / Accepted: 26 February 1998