Low-salinity Freshwater Research Articles

Hydrochemistry characters and hydrochemical processes under the impact of anthropogenic activity in the Yiyuan city, Northern China

Water resource is a valuable resource for human beings to survive and maintain social stability and development. However, in recent years, the process of urbanization has been accelerated, and many cities and towns have presented groundwater pollution. To investigate the spatial distribution of hydrochemical components in urban areas after groundwater pollution and the hydrogeochemical effects on surrounding areas, using multifarious methods such as classical statistics, geostatistics, saturation index, and stable isotopes, the hydrogeochemical effects along groundwater flow were analyzed and deduced. The results show that the main ions of the groundwater in the Yiyuan are Ca2+ and HCO3−, it is mainly low-salinity fresh water, and the hydrochemistry type is mainly HCO3–Ca·Mg type. Groundwater pollution in urban areas increases the content of inorganic and organic matter in groundwater, the main ions affected are NO3−, Cl−, Ca2+, and SO42−, and their concentrations increased by 12.3, 22.3, 7.6, and 12.3 mg/L, respectively. In the city, negative cation exchange occurs mainly, after leaving the city, cation exchange occurs mainly. The results of the saturation index calculation indicate that groundwater pollution has little effect on the dissolution and precipitation of minerals. After leaving the town, denitrification, desulphurization, and cation exchange occurs in the underground aquifer, which reduces the concentration of pollutants in the groundwater. The study suggests that a variety of hydrogeochemical processes play an important role in the spontaneous reduction of some pollutant concentrations in groundwater away from the pollution source, while the concentration of other substances may rise.

Retrieval and Analysis of Sea Surface Salinity in the Adjacent Waters of the Yangtze River Estuary Based on Multisource Satellite Data

Cao, K.; Sun, W.; Chen, L.; Meng, J., and Zhang, J., 2020. Retrieval and analysis of sea surface salinity in the adjacent waters of the Yangtze River Estuary based on multisource satellite data. Journal of Coastal Research, 36(3), 590–599. Coconut Creek (Florida), ISSN 0749-0208.Moderate Resolution Imaging Spectroradiometer, Sea-Viewing Wide Field-of-View Sensor, and Visible Infrared Imaging Radiometer Suite multisource satellite remote sensing reflectance data are used with in situ sea surface salinity (SSS) measurements in the Yellow Sea and East China Sea. A linear algorithm is developed for the retrieval of summer SSS in adjacent waters of the Yangtze Estuary in the Yellow Sea and East China Sea. The accuracy of SSS retrieval results is validated using independent in situ measurements. Results show that the mean bias of the model is –0.34 psu, the root-mean-square error is 1.55 psu, and the correlation coefficient is 0.80. The linear model is extended to the retrieval of multisource satellite monthly remote sensing reflectance data to obtain monthly SSS products of the Yangtze Estuary. The spatial coverage of fused satellite SSS data is about 10% greater than that of single-satellite monthly retrieved SSS data. The SSS in the Yangtze Estuary research area has lower values nearshore and higher values offshore. The SSS gradually rises from nearshore areas to open water, and an obvious low-salinity water tongue forms in the Yangtze Estuary. The eastward expansion of freshwater flows of the Yangtze River into the sea is mainly affected by the runoff of the Yangtze River, while a southerly wind and northeastward flow in the research area are the main factors responsible for the eastward expansion of the Yangtze River freshwater flows to the NE. The effect of freshwater on the Yellow Sea and East China Sea extends to 125.5° E, and the low-salinity freshwater tongue distributes northeastward. The expansion types of the Yangtze River freshwater include NE expansion, N-NE expansion, E-NE expansion, bidirectional expansion, and nondirectional expansion.

High Nitrate and Phosphate Ions Reduction in Modified Low Salinity Fresh Water through Microalgae Cultivation

The treatment of nitrate and phosphate ions in fresh water such as streams, rivers, lakes, reservoirs, and wetlands through biological treatment has been getting more crucial and popular in recent years. This paper reports the reduction of nitrate and phosphate ions in modified low salinity fresh water via the cultivation of a microalgae strain, e.g., Tetraspora sp. and Spirogyra sp. The low salinity fresh water (9054 to 9992 ppm) was modified with the addition of organic fertiliser (VermiCompost Tea) and used as the cultivation medium to grow microalgae. The microalgae strains were grown under controlled conditions in an indoor laboratory for 14 days. The initial concentrations of nitrate and phosphate ions in the modified fresh water sample were 1.17 mg/L and 0.10 mg/L, respectively. The reduction of nitrate and phosphate ions associated with the effect of cultivation of Tetraspora sp. and Spirogyra sp. in ambient air (0.03% of CO2) and 15% of CO2 was investigated. In ambient air, the cultivation of Tetraspora sp. and Spirogyra sp. greatly reduced the nitrate ions concentration from 5.96 ± 0.28 to 0.37 ± 0.05 mg/L and from 2.35 ± 0.19 to 0.59 ± 0.08 mg/L, respectively. A 100% reduction of phosphate ions was observed in the cultivation of Tetraspora sp. and Spirogyra sp. from 0.52 ± 0.10 mg/L in 13 days of and from 0.63 ± 0.15 mg/L in 6 days, respectively. Meanwhile, with the aeration of 15% of CO2, after the 14 days cultivation of Tetraspora sp. and Spirogyra sp. reduced the nitrate ions concentration from 5.27 ± 0.06 to 1.80 ± 0.20 mg/L and from 4.73 ± 0.12 to 2.80 ± 0.10 mg/L, respectively. The excessive CO2 in water consequently lowered the pH of water medium from 7.18 to 6.60 due to the formation of carbonic acid (H2CO3). It was feasible to couple the removal of nitrogen and phosphorus in Sungai Sura (4°42″28.2° N 103°26″12.1° E) while cultivating microalgae through biological treatment to produce biomass for biofuel production.

Introducing water frogs – Is there a risk for indigenous species in France?

The ecological success of introduced species in their new environments is difficult to predict. Recently, the water frog species Rana ridibunda has raised interest, as different genetic lineages were introduced to various European countries. The aim of the present study was to analyze the potential invasiveness of R. ridibunda and assess the risk of replacement for indigenous water frog species. The investigation of over 700 water frogs from 22 locations in southern France and four locations in Spain shows that the competition with indigenous species is mainly limited to a particular habitat type, characterized by high-oxygen and low-salinity freshwater. The competitive strength of R. ridibunda may be related to a higher growth rate and longevity as compared to the indigenous species R. grafi and R. perezi. Our data suggest that R. ridibunda is a risk to the diversity of indigenous water frog assemblages in France. Future monitoring needs to clarify the distribution of R. ridibunda, its ecological niche, and the risk status for indigenous water frog species. To cite this article: D.S. Schmeller et al., C. R. Biologies 330 (2007).

Isotopic composition of natural thermal discharges on Vulcano island, southern Italy

This paper reviews the isotopic 18 O 16 O and D/H ratios reported in the literature for phreatic waters in the plain of Vulcano island off Sicily and condensates from high-temperature fumaroles at the top of the summit crater. The Vulcano phreatic waters have a rather high average annual temperature (greater than 30|dgC), but do not seem to be heated directly by mixture with condensates of fumarolic steam. They seem to originate from rainwater and to undergo high evaporation, particularly in summer, owing to high conductive heat flow in the island. By comparing the 18 O 16 O and D/H ratios with Cl − (as HCl) content, it is estimated that 75% of the steam from the high-temperature fumaroles comes from seawater and 25% from low-salinity waters. The latter, however, do not seem to come directly from the shallow aquifer of Vulcano because the steam from the fumaroles does not contain radiogenic tritium. This mixing model and the lack of steam condensation in the Vulcano aquifer implies, indirectly, that there are no steam losses during the rise of deep fluids, and that some observed variations in the outlet temperatures without accompanying variations in the composition of the associated gas phase may be due to increased (or decreased) extent of fracturation in the volcanic edifice (as a result, for instance, of tectonic movements), which cause more (or less) vaporization of low-salinity fresh water into the volcanic ducts as well as faster (or slower) outflow of deep gases.