Heavy Metals and Related Human Health Risk Assessment for River Waters in the Issyk−Kul Basin, Kyrgyzstan, Central Asia

The water resources of Central Asia play an important role in maintaining the fragile balance of ecosystems and the sustainable development of human society. However, the lack of research on the heavy metals in river waters has a far−reaching influence on public health and the sustainable development in Central Asia. In order to reveal the possible sources of the heavy metals and to assess the associated human health risks, thirty−eight water samples were collected from the rivers of the Issyk−Kul Basin during the period with low river flow (May) and the period with high river flow (July and August), and the hydrochemical compositions and major ions of heavy metals were analyzed. No changes in hydrochemical facies were observed between the two periods and the river water type was calcium bicarbonate. Carbonate dissolution and silicate weathering controlled the variation of cations and anions in river waters from the Issyk−Kul Basin. There were some differences in the sources of heavy metals in water bodies between the two periods. During the period with low river flow, heavy metals (Cr) were closely clustered with major ions, indicating that they were mainly affected by water–rock interactions. During the period with high river flow, all heavy metals studied in this paper had different sources of major ions, and the heavy metals maybe influenced by human activities. From the human health risk assessment, the hazard quotients for all samples were less than 1, reflecting that there was no noncarcinogenic risk in the river waters of the Issyk−Kul Basin during the two sampling periods. However, the water samples with carcinogenic risk of arsenic exceeding the threshold (10−4) accounted for 21.1% of the total, indicating that there were some certain carcinogenic hazards for human health via water drinking with direct oral ingestion. The results are of certain significance for the utilization and protection of water resources in the basin as well as the protection of public health.

Trace metals in the water and margin sediments of the Rio Doce Basin in Linhares municipality, ES, Brazil

The Rio Doce Basin (DRB) is the largest freshwater source in Espírito Santo (ES) state, Brazil. In November 2015, the disruption of the iron tailings dam in the Mariana municipality, Minas Gerais state, Brazil, severely affected this river. In this study, we showed the trace metals concentrations in the water and margin sediments of the DRB during the dry and wet seasons. This new data was obtained in 2011, prior to the environmental disaster caused by disruption of the dams. We observed Cr, Ni and Pb contaminations in the sediments. The concentrations of these elements in the high river flow (wet season) were higher than the guideline values (GV) of level II and geoacumulation Index (Igeo). However, Fe and Mn concentrations were well above the GV in the wet season. The levels of these two elements were lower than the values found in the region's Haplic Cambisol. Furthermore, the comparison between our data and those of the technical reports released after the dams rupture shows that iron ore mine tailings greatly alter the trace metals concentration in water and sediments. However, we have observed a trend of resilience that requires more systematic and careful studies in DRB.

Anomalies and trends of high river flow under temperate climatic conditions in north-eastern Romania

Regional water resource management plans include various scenarios related to the anomalies and trends of hydro-climatic parameters. Two methods are used for the identification of the anomalies and trends associated with high flow (annual and seasonal) of the rivers in Eastern Romania, namely the quantile perturbation method (QPM) and the partial trend method (PMT). These methods were selected due to the fact that they are suitable for data sets which do not rely on restrictive statistical assumption as common parametric and nonparametric trend tests do. For six of the nine stations analyzed, the decreasing trend in high extremes for annual high flow based on the PTM is the same as the annual trend obtained with the QPM. Using the PI index (associated with PTM) for the estimation of trend intensity, values between −2.280 and −9.015 m3/s were calculated for the decreasing trend of the annual high flow and between +1,633 m3/s (in autumn) and −9.940 m3/s (in summer) for the seasonal high flow. The results obtained on the anomalies and trends of high river flow may represent a starting point in the analysis of the evolution of water resources and their effective management.

Impact of Human Activities and Natural Processes on the Seasonal Variability of River Water Quality in Two Watersheds in Lampung, Indonesia

This study identified seasonal water quality characteristics in two adjacent mountainous rivers (Sangharus and Sekampung Hulu Rivers) in Lampung, Indonesia and determined the impacts of fertilizer application on river chemistry as a result of social forestry management. In 2016, we measured water chemistry and conducted a farmers’ questionnaire survey to obtain information on fertilizer application. The water quality results indicated that several parameters, including nitrate (NO3) and phosphate (PO4), were significantly higher in the Sangharus River than in the Sekampung Hulu River. In addition, several parameters were influenced by dilution from high river flow in the rainy season. Some parameters were likely influenced by the weathering of parent materials. By contrast, electrical conductivity (EC) and NO3 were higher in the rainy season, which was likely linked to the dominant timing of urea fertilizer application during this season. Despite the application of fertilizers in the watersheds, NO3 levels remained below the recommended standard. However, aluminum and iron concentrations were higher than the recommended level for drinking water, which was likely due to elevated soil erosion from improper land management. Therefore, we recommend that effective land management policies be implemented through the adoption of soil conservation practices for nutrient loss prevention.

Expected Future Runoff of the Upper Jordan River Simulated with a CORDEX Climate Data Ensemble

Data from five different RCMs run in two experiments from the Coordinated Regional Climate Downscaling Experiment (CORDEX) are applied together with the Water Flow and Balance Simulation Model (WaSiM) to assess the future availability of water in the upper Jordan River. Simulation results for 1976–2000 show that the modeling system was able to reasonably reproduce the observed discharge rates in the partially karstic complex terrain without bias correction of the precipitation input. For the future climate in the area, the applied CORDEX models indicate an increasing annual mean temperature for 2031–60 by 1.8 K above the 1971–2000 mean and by 2.6 K for 2071–2100. The simulated ensemble mean precipitation is predicted to decrease by 16.3% in the first period and 22.1% at the end of the century. In relation to the mean for 1976–2000, the discharge of the upper Jordan River is simulated to decrease by 7.4% until 2060 and by 17.5% until 2100, together with a reduction of high river flow years.

Nutrient and phytoplankton biomass in the Amazon River shelf waters

The Amazon River estuary is notable at the Amazon Continental Shelf, where the presence of the large amount of water originating from the Amazon during the river's falling discharge period was made evident by the low salinity values and high nutrient levels. Even so, the presence of oceanic waters in the shelf area was significant. Dissolved organic nitrogen was the predominant species of the nitrogen cycle phases, followed by total particulate nitrogen, nitrate, ammonium and nitrite. The chlorophyll a data in the eutrophic area indicated that there is sufficient nitrogen in the area to withstand productivity, though dissolved inorganic nitrogen removal processes are faster than regeneration or mineralization. The anomalous amounts of inorganic dissolved nitrogen showed more removal than addition. The simulations with the bidimensional MAAC-2D model confirmed that high nutrient waters are displaced northwest-ward (two cores at 2.5ºN-50ºW and 4ºN-51ºW) by the stronger NBC during falling river discharge. During high river flow period these nutrient-rich lenses are distributed around 0.5ºN-48.5ºW as well as along the shallow Amazonian shelf (20m-50m depth, 1ºN-3.5ºN), as a result of the spreading of Amazon freshwater outflow.

Identifying resuspended sediment in an estuary using the 228Th/232Th activity ratio: the fate of lagoon sediment in the Bega River estuary, Australia

Thorium-series nuclides (228Th and 232Th) have been used to identify resuspended sediment in the Bega River estuary, south-eastern Australia. A non-conservative increase in concentration of suspended sediment of water in the vicinity of mid-estuary back-flow lagoons was associated with a decrease in the 228Th/232Th activity ratio (AR) of the suspended sediment. The lagoon sediment is characterized by a low estuarine 228Th/232Th signature, distinguishing it from freshwater suspended sediment recently delivered to the estuary, and identifying it as the likely source of the additional suspended sediment. Sediment-core 210Pb profiles show that the lagoons are accumulating sediment, presumably during high river-flow events. However this study indicates that during intervening periods of low flow, 40% of sediment deposited in the lagoons is subsequently resuspended and exported to the lower estuary, and possibly to the ocean. The utility of the 228Th/232Th AR to quantify sediment resuspension in estuaries is likely to be estuary-dependent, and is controlled by the extent of scavenging of dissolved 228Th by suspended particles.