Experimental study on the impact of temperature on the dissipation process of supersaturated total dissolved gas

Water temperature not only affects the solubility of gas in water but can also be an important factor in the dissipation process of supersaturated total dissolved gas （TDG）. The quantitative relationship between the dissipation process and temperature has not been previously described. This relationship affects the accurate evaluation of the dissipation process and the subsequent biological effects. This article experimentally investigates the impact of temperature on supersaturated TDG dissipation in static and turbulent conditions. The results show that the supersaturated TDG dissipation coefficient increases with the temperature and turbulence intensity. The quantitative relationship was verified by straight flume experiments. This study enhances our understanding of the dissipation of supersaturated TDG. Furthermore, it provides a scientific foundation for the accurate prediction of the dissipation process of supersaturated TDG in the downstream area and the negative imp）acts of high dam projects on aquatic ecosystems.     

Summer total phosphorus in lakes: A map of Minnesota,Wisconsin, and Michigan,USA

A map of summer total phosphorus in lakes has been compiled for Minnesota, Wisconsin, and Michigan to clarify regional patterns in attainable lake trophic state. Total phosphorus was used as a measure of lake trophic state because: (1) phosphorus plays a central role in controlling the overall fertility of most lakes, (2) total phosphorus values are available for a great number of lakes, and (3) phosphorus is measured in a consistent manner. The maps were compiled using patterns of total phosphorus data and observed associations between these data and geographic characteristics including physiography, land use, geology, and soils. Regions depicted on the map represent areas of similarity in phosphorus concentrations in lakes, or similarity in the mosaic of values, as compared to adjacent areas. Within each region, differences in total phosphorus can be compared to natural and anthropogenic factors to determine the types of lakes representative of each region, the factors associated with differences in quality, and the realistically attainable phosphorus levels for each type of lake.     

Microbiological Monitoring of Marine Recreational Waters in Southern California

An inventory was conducted to assess the number, type, spatial distribution, and costs of microbiological monitoring programs in southern California marine waters from Point Conception to the US/Mexico International Border. The location of each sampling site was determined using global positioning system (GPS), and estimates of geographic coverage were determined using geographic information system (GIS) techniques. Twenty-one programs conducted 87,007 tests annually at 576 sites in the study area. The largest number of sites was sampled in Orange County, whereas the largest number of analyses was performed in Los Angeles County because monitoring programs in this area focused on daily monitoring. Fifteen of the 21 programs were managed by National Pollutant Discharge Elimination System (NPDES) permitted sewage effluent dischargers who sampled both offshore and shoreline waters and typically tested for three indicator bacteria (total coliform, fecal coliform, and enterococcus). Their combined efforts comprised 82% of all of the microbiological indicator analyses conducted on an annual basis. Five of the remaining monitoring organizations were public health agencies, which typically focus their efforts on testing only total coliforms. Laboratory methodology also varied considerably, with NPDES permittees predominantly utilizing membrane filtration while public health agencies generally used multiple tube fermentation or premanufactured test kits. Nearly three quarters of all the effort expended in southern California occurred along the shoreline as opposed to offshore locations. Two thirds of this shoreline effort was focused on high-use sandy beaches and in proximity to perennial freshwater outlets (storm drains and creeks). Most sampling occurred at a set of fixed sites that were revisited frequently, but only represented about 7% of the total shoreline. We estimated that roughly $3 million is spent annually on monitoring bathing water quality in southern California, exceeding that spent in any other part of the country.     

CALIBRATION OF STORM LOADS IN THE SOUTH PRONG WATERSHED,FLORIDA, USING BASINS/HSPF1

ABSTRACT: The South Prong watershed is a major tributary system of the Sebastian River and adjacent Indian River Lagoon. Continued urbanization of the Sebastian River drainage basin and other watersheds of the Indian River Lagoon is expected to increase runoff and nonpoint source pollutant loads. The St. Johns River Water Management District developed watershed simulation models to estimate potential impacts on the ecological systems of receiving waters and to assist planners in devising strategies to prevent further degradation of water resources. In the South Prong system, a storm water sampling program was carried out to calibrate the water quality components of the watershed model for total suspended solids (TSS), total phosphorous (TP), and total nitrogen (TN). During the period of May to November 1999, water quality and flow data were collected at three locations within the watershed. Two of the sampling stations were located at the downstream end of major watercourses. The third station was located at the watershed outlet. Five storm events were sampled and measured at each station. Sampling was conducted at appropriate intervals to represent the rising limb, peak, and recession limb of each storm event. The simulations were handled by HSPF (Hydrologic Simulation Program‐Fortran). Results include calibration of the hydrology and calibration of the individual storm loads. The hydrologic calibration was continuous over the period 1994 through 1999. Simulated storm runoff, storm loads, and event mean concentrations were compared with their corresponding observed values. The hydrologic calibration showed good results. The outcome of the individual storm calibrations was mixed. Overall, however, the simulated storm loads agreed reasonably well with measured loads for a majority of the storms.     

Alternative strategies for a father with a small brood: mate, cannibalise or care

Brood cycling, the alternation of periods of courtship and mating activity ("mating phase") with days of full brood care ("parental phase"), and total filial cannibalism, the consumption of all current offspring by a parent, have been interpreted as a response to the conflicting demands faced by parental males during the breeding season. Under the assumption that these two behaviours result from trade-offs among mating, caring and feeding, the strategy adopted by the male should depend on egg number and age. This hypothesis was tested in the scissors-tail sergeant (Abudefduf sexfasciatus), a common tropical damselfish. Observations of undisturbed males and a brood reduction experiment confirmed all theoretical predictions. The shift from the mating to parental phase occurred when an appropriate number of eggs had been obtained. When the brood was reduced on the first day of the parental phase, males often reverted to the mating phase, but never did so if the manipulation occurred on the second or third day. Only broods that were smaller than average were consumed by the parental male. Artificial reduction of the brood increased the incidence of total filial cannibalism, but the probability of cannibalism decreased with brood age. Electronic Publication     

总量控制区内功能区排放负荷的风频分配法研究

在总量控制A值法（GB／T13201－91）的基础上,考虑了总量控制区“气象资料”和各功能区位置及污染物“影响范围”等因素的影响,提出了“平均下风距离”的概念,从而建立了功能区排污负荷分配方法。通过与面积分配方法相比较,验证了新方法的合理性和有效性。     

原子荧光法测定水中总汞的测量不确定度分析

以测定水中汞含量为例,对其在分析过程中产生的不确定度进行识别和计算,对原子荧光法测量水中总汞的不确定度加以分析评定。     

污染物减排的措施与对策探讨

污染减排涉及到技术、经济、管理等一系列要素和环境、经济、企业等不同部门,是一项系统工程,要实现减排目标,必须结合国情和地方实际,实施源头控制、末端治理、监督管理等三大措施与对策。     

Seasonal differences in mercury accumulation in Trichiurus lepturus (Cutlassfish) in relation to length and weight in a Northeast Brazilian estuary

Background, aim, and scope  At tropical latitudes, and especially on the semi-arid coasts of the Brazilian Northeast, the rainfall regime governs the water quality of estuaries due to the pronounced difference between the rainy and dry seasons. These changes may be responsible for seasonal changes in bioavailability of mercury (Hg) and other pollutants to the estuarine and coastal biota. Mercury bioaccumulates along estuarine–marine food chains usually result in higher concentrations in tissues of top predators and posing a risk to both marine mammals and humans alike. The Goiana River Estuary (7.5° S) is a typical estuary of the semi-arid tropical regions and supports traditional communities with fisheries (mollusks, fish, and crustacean). It is also responsible for an important part of the biological production of the adjacent coastal waters. Materials and methods   Trichiurus lepturus (Actinopterygii: Perciformes) is a pscivorous marine straggler. Fish from this species (n = 104) were captured in a trapping barrier used by the local traditional population and using an otter trawl net along the main channel of the low estuary during two dry seasons (D1 = November, December 2005, January 2006; D2 = November, December 2006, January 2007) and the end of a rainy season (R = August, September, October 2006). Fish muscle samples were preserved cold and then freeze-dried prior to analysis of its total mercury (Hg-T) contents. Total mercury was determined by cold vapor atomic absorption spectrometry (CV-AAS) with sodium borohydride as a reducing agent. Results  The studied individuals (n = 104) were sub-adult (30–70 cm, 71 ind.) and adult fish (>70 cm, 33 ind.). Weight (W) (204.1 ± 97.9 g, total biomass = 21,229.7 g) and total length (TL) (63.1 ± 10.1 cm, range 29.5–89.0 cm) presented a significant (p < 0.05) correlation. Two-way ANOVA (n = 81) showed that TL and W had significant differences (p < 0.05) among seasons, being higher in D1 than in D2 and R, respectively. Moreover, season vs. month interaction were detected for the variables length and weight. For the variable weight was detected significant difference for the factor month (p < 0.05). It suggests that the fish enter the estuary at the end of the rainy season and increase in length and weight during the time they spend in the estuary. Fish from this estuary are shown to be fit for human consumption (125.3 ± 61.9 μgHg-T kg^–1 w.wt.; n = 104). Fish mercury contents increased with size and weight. Correlations between TL and Hg-T (r = 0.37286) and between W and Hg-T (r = 0.38212) were significant (p < 0.05). Dryer months showed higher mercury concentrations in fish (D1 773.4 ± 207.5 μgHg-T kg^–1 d.wt., n = 27; D2 370.1 ± 78.8 μgHg-T kg^–1 d.wt., n = 27; R 331.2 ± 138.5 μgHg-T kg^–1 d.wt., n = 27). The variable mercury concentration showed differences in relation to the factor season (p < 0.05), where fish captured during the first dry season showed the highest concentration of mercury. The correlation between Hg-T and rainfall (Rf) showed a negative correlation (r = –0.56; p < 0.05). Discussion  The main likely source of mercury to this estuary is diffuse continental run off, including urban and industrial effluents. Since concentration of mercury in fish tissue is negatively correlated to rainfall, but positively correlated with fish length and weight, it suggests that fish growth in this estuary results in mercury uptake and concentration on the fish tissue. In the dry season of 2005–2006, when rainfall remained below the historic average, fish bioaccumulated significantly more mercury than in the dry season 2006–2007, when rainfall was within the predictable historic average. It is suggested that less rainfall, and consequently less particulate matter and less primary production in the estuary, make mercury more available to the higher levels of the estuarine food chain. In the case of higher rainfall, when river flow increases and water quality in the estuary is reduced, mercury probably is quickly exported associated to the particulate matter to the adjacent coastal waters where it then disperses. This species is a potential routine bioindicator for mercury contamination of the biota, but so far was used only with a limited number of individuals and contexts. Conclusions  Fish from the Goiana River estuary can still be safely consumed by the local population. However, any further contamination of this resource might lead to total mercury levels above the recommended limits for pregnant women and small children. The proposed heavy dependency of total mercury levels in fish on water quality indicates that land use and water quality standards must be more closely watched in order to guarantee that best possible practices are in place to prevent bioaccumulation of mercury and its transfer along the food chain. Human interventions and climatic events which affect river water flow are also playing a role in the mercury cycle at tropical semi-arid estuaries. Recommendations and perspectives   T. lepturus is largely consumed by coastal populations of tropical and sub-tropical countries all over the world. It is also consumed by a number of marine mammals over which we have a strong conservation interest. This species is also a link among different ecosystems along the estuarine ecocline. Therefore, knowledge of its degree of contamination might contribute to public health issues as well as marine conservation actions. Studies on mercury and other contaminants using this species as bioindicator (cosmopolitan, readily available) could help elucidating mechanisms through which pollutants are being transferred not only through the food chain, but also from estuarine–coastal–open waters. In addition, using the same species in marine pollution studies, especially as part of a mosaic of species, allows for wide range comparisons of marine food chain contamination.     

Macroergonomics and Total Quality Management: How to Improve Quality of Working Life?

Abstract

In this paper, we present a macroergonomic model of work design that is applied and tested to examine Total Quality Management (TQM) in the public sector. According to the model, TQM can influence different aspects of work design and quality of working life (QWL), Questionnaire data collected in 2 public sector organizations in the USA show that TQM can have both positive and negative impact on work design and QWL. The main positive impact of TQM was found on job content, job control and participation, and social relationships. The main negative impact of TQM was on workload, uncertainty, and clarity of job duties. The impact of TQM on QWL was mixed. Our results show that the impact of TQM on work design and QWL varied very much across the 6 participating departments, as well as within the departments. Further research is warranted to assess the human impact of TQM, in particular research on the linkage between various aspects of TQM, on one hand, and work design and QWL, on the other hand.