Small ponds comprise a substantial portion of the total area of the Earth's inland waters. They can be powerful carbon sinks or sources, potentially significant processors of organic carbon. Our ...understanding of their role is constrained by the absence of information regarding their CO.sub.2 fluxes (F CO.sub.2) and how these change with wet or dry phases and across distinct pond plant communities. We monitored the F CO.sub.2 from 26 neighbouring small ponds over a 2-week drying period in late summer in 2014. The mean F CO.sub.2 on day 1 (-641 ± 1490 mg m.sup.-2 day.sup.-1) represented a net intake across the site. As ponds dried they switched to becoming CO.sub.2 sources resulting in a net site emission of CO.sub.2 by day 12 (3792 ± 2755 mg m.sup.-2 day.sup.-1) although flux rates did not vary systematically between plant communities. Significant variability in the F CO.sub.2 was observed amongst adjacent ponds on individual sampling days, resulting in marked spatial heterogeneity in CO.sub.2 processing. This large degree of temporal and spatial heterogeneity across short time periods and small distances highlights the variability in the F CO.sub.2 from temporary systems, making it hard to generalize their role in carbon cycle models.
It has come to the attention of IOP Publishing that this article should not have been submitted for publication, and consequently, this paper has been retracted by IOP Publishing on 11 August 2020. ...Retraction published: 11 August 2020
History of the solar ponds: A review study El-Sebaii, A.A.; Ramadan, M.R.I.; Aboul-Enein, S. ...
Renewable & sustainable energy reviews,
08/2011, Letnik:
15, Številka:
6
Journal Article
Recenzirano
Solar pond was discovered as a natural phenomena around the turn of the last century in the Medve Lake in Transylvania in Hungary. In this lake, temperatures up to 70
°C were recorded at a depth of ...1.32
m at the end of the summer season. The minimal temperature was 26
°C during early spring. The bottom of this lake had a salt NaCl with concentration of 26 percent. Solar pond is artificially constructed. To prevent convection, salt water is used in the pond. Those ponds are called “salt gradient solar pond”. Nowadays, mini solar ponds are also being constructed for various thermal applications. It was concluded that the optimum value of salinity in the mini solar pond is 80
g/kg of water.
Small ponds—farm ponds, detention ponds, or impoundments below 0.01 km2—serve important human needs throughout most large river basins. Yet the role of small ponds in regional nutrient and sediment ...budgets is essentially unknown, currently making it impossible to evaluate their management potential to achieve water quality objectives. Here we used new hydrography data sets and found that small ponds, depending on their spatial position within both their local catchments and the larger river network, can dominate the retention of nitrogen, phosphorus, and sediment compared to rivers, lakes, and reservoirs. Over 300,000 small ponds are collectively responsible for 34%, 69%, and 12% of the mean annual retention of nitrogen, phosphorus, and sediment in the Northeastern United States, respectively, with a dominant influence in headwater catchments (54%, 85%, and 50%, respectively). Small ponds play a critical role among the many aquatic features in long‐term nutrient and sediment loading to downstream waters.
Plain Language Summary
Reservoirs created by river damming have extensive impacts on downstream water quality but are not necessarily the most important elements of a diverse aquatic landscape. Many more small ponds have been constructed to serve important human needs ranging from farm irrigation in agricultural areas to flood control and trapping of nutrients and fine sediment in urban areas. The number of human‐influenced small ponds is projected to rise worldwide, yet their role in the delivery of nutrients and sediment from headwaters to oceans is currently unresolved. Here we used new data sets and found that small ponds are collectively responsible for trapping a substantial amount of the nutrients and sediment that are exported annually from headwaters. These findings support the need to jointly consider features such as urban detention ponds, farm ponds, and beaver ponds in managing headwaters to decrease long‐term nutrient and sediment loading to downstream waters and sensitive coastal areas.
Key Points
Small ponds located in headwater catchments dominate nutrient and sediment retention compared to streams, rivers, lakes, and reservoirs
Small ponds located directly adjacent to streams or away in upland positions have distinct effects on nitrogen, phosphorus, and sediment
Finer‐scale small streams are minor net sources of phosphorus and major net sources of sediment where soil erodibility is high
•An assessment of salinity gradient stability of an industrial solar pond was performed.•Two methodologies based on the stratification principle were adapted and used.•The boundaries of the salinity ...gradient appeared as the main source of instability.•The methodology based on coefficients of expansion is useful to control the solar pond.
In this study, an assessment of salinity gradient stability of an industrial solar pond during two operation seasons (2014 and 2105) is presented. An industrial solar pond was constructed to supply a low-temperature heat (up to 60 °C) to achieve the temperature requirements of the flotation stage in a mineral processing plant (Solvay Minerales in Granada (Spain)). Along the first season, the salinity gradient was considered technically destroyed in April 2015 as the height to the upper convective zone increases from 0.3 m in July 2014 to 0.8 m. Two different methodologies based on the stratification principle were adapted and used in order to evaluate the salinity gradient stability. The boundaries of the salinity gradient appeared as the main source of instability. In the upper zone it is associated with the environmental parameters (e.g., rain and wind) that affect the upper convective zone and the upper layers of the non-convective zone that subsequently transmit the instability to the lower layers. In the bottom zone it is caused by operation parameters, such as the heat extraction or the addition of salt. Both methodologies provided similar predictive capability of stability results. However, the results provided by the stability analysis using the thermal and salinity expansion coefficients are a more useful tool in the control of the salinity gradient for solar pond technology.
Euxinic conditions, which are defined by the presence of sulfide in the water column, were common in ancient oceans. However, it is not clear how the presence of sulfide in the water column affects ...the balance between rates of sulfide oxidation and sulfate reduction, which plays a major role in regulating the net redox state of the ocean-atmosphere system. Euxinia could lead to higher rates of sulfide oxidation because sulfide may diffuse more rapidly into the oxic zone in solution than in sediment. Alternatively, sulfide oxidation could be inhibited by low overall availability of suitable oxidants in euxinic settings. Here, we constrain rates of sulfide oxidation versus sulfate reduction in four euxinic water columns in coastal ponds by modeling the evolution of the concentration and sulfur and oxygen isotope compositions of sulfate from post-hurricane, well-oxygenated conditions to modern, euxinic conditions. The results of the one-dimensional, depth-dependent models of water column sulfate geochemistry indicate that the fraction of sulfate reduced that is subsequently reoxidized is low (0.11–0.42) in euxinic systems relative to the modern well-oxygenated ocean (0.75–0.90). This implies that sulfide reoxidation rates are low in euxinic systems because of oxidant limitation and physical transport. Low fractional sulfide reoxidation in euxinic systems has important implications for exploring how oxygen levels in the ocean and atmosphere have changed through Earth history. We use a marine sulfate isotope box model to explore how low reoxidation rates in euxinic systems affect marine sulfate sulfur and oxygen isotope records. Model results indicate that marine sulfate sulfur and oxygen isotope compositions increase during the expansion of euxinia with patterns that are distinct from other isotopic changes to the marine sulfate reservoir. Thus, marine sulfate sulfur and oxygen isotope box models can be applied to ancient isotope records in order to evaluate the expansion of euxinia in ancient oceans because sulfide oxidation rates are low relative to sulfate reduction rates.
Economics of alternative catfish production technologies Kumar, Ganesh; Engle, Carole R.; Hanson, Terry R. ...
Journal of the World Aquaculture Society,
December 2018, 2018-12-00, 20181201, Letnik:
49, Številka:
6
Journal Article
Recenzirano
Odprti dostop
The US catfish industry has shown increasing trends toward intensification of production as a means of achieving cost efficiencies on farms. Previous studies depicted the potential for cost ...efficiencies in alternative technologies such as split‐pond systems, intensively aerated ponds, and in‐pond raceway systems. This study provides an economic comparison of these systems under a uniform set of economic assumptions using a standard enterprise budget analysis. Cost of production of hybrid catfish raised in these systems ranged from $2.03 to $2.91/kg, the highest cost being that of in‐pond raceways and the lowest from split ponds. Positive annual net cash flows from split‐pond systems and intensively aerated ponds were sufficient to make the investment profitable. Cumulative effects of high investment cost (high annual fixed costs), poor survival, and lower yields from the in‐pond raceway systems made it economically infeasible. However, the feed conversion ratio (FCR) was the best among these technologies. Risk analysis showed stochastic dominance of intensively aerated ponds and split‐pond systems over in‐pond raceway systems. Variations in catfish price, yield, and FCR were the major contributors to economic risk. Implementing combinations of intensively aerated ponds and split‐pond systems should be viewed as a strategy to respond to production and market needs.
Waste stabilization ponds (WSPs) and their variants are one the most widely used wastewater treatment systems in the world. However, the scarcity of systematic performance data from full-scale plants ...has led to challenges associated with their design. The objective of this research was to assess the performance of 388 full-scale WSP systems located in Brazil, Ecuador, Bolivia and the United States through the statistical analysis of available monitoring data. Descriptive statistics were calculated of the influent and effluent concentrations and the removal efficiencies for 5-day biochemical oxygen demand (BOD
), total suspended solids (TSS), ammonia nitrogen (N-Ammonia), and either thermotolerant coliforms (TTC) or Escherichia coli for each WSP system, leading to a broad characterization of actual treatment performance. Compliance with different water quality and system performance goals was also evaluated. The treatment plants were subdivided into seven different categories, according to their units and flowsheet. The median influent concentrations of BOD
and TSS were 431 mg/L and 397 mg/L and the effluent concentrations varied from technology to technology, but median values were 50 mg/L and 47 mg/L, respectively. The median removal efficiencies were 85% for BOD
and 75% for TSS. The overall removals of TTC and E. coli were 1.74 and 1.63 log
units, respectively. Future research is needed to better understand the influence of design, operational and environmental factors on WSP system performance.
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