Combining metal and sulfate isotopes measurements to identify different anthropogenic impacts on dissolved heavy metals levels in river water

Using sulfur and oxygen isotope values to partition riverine sulfate sources and illustrate their responses to hydrological processes

Orogenesis contributes to the elevation of highly eroded rock strata, whose interactions with the atmosphere, water, and biota result in the release of dissolved substances. The fluvial transport of dissolved sulfate (SO42-) from mountains to oceans is a critical component of the global sulfur cycle. However, anthropogenic activities have significantly increased the concentrations of sulfate and altered isotope compositions. It is imperative to delineate the impacts of anthropogenic disturbances and clear their transport mechanisms. To address this issue, spatial and temporal water samples were collected from the Qin River Basin (QRB) between 2012 and 2015. Sulfate sulfur and oxygen isotope values (δ34S-SO42- and δ18O-SO42-), alongside Bayesian isotope mixing models (BIMMs) were employed to identify pathways of anthropogenic inputs and quantify their contributions. The average mainstream SO42- concentration, δ34S-SO42- and δ18O-SO42- values in the upper reaches (n = 18), middle (n = 9), and lower reaches (n = 44) were 1.09 mmol/L, 1.5 ‰ and 5.6 ‰; 1.34 mmol/L, 6.8 ‰ and 6.9 ‰; 2.31 mmol/L, 8.5 ‰ and 7.7 ‰, respectively. BIMMs results from spatial water samples indicated an increasing trend in contributions from gypsum, loess, sewage and chemical fertilizer but a decreasing trend from coal mine drainage (CMD) and pedogenic sulfate sources to riverine sulfate along the river. Results from temporal water samples at the outlet indicated that pedogenic sulfate, CMD, and loess sulfate were transport-limited, conversely, gypsum and chemical fertilizer were source-limited, and sewage has chemostatic behaviors. Despite a significant reduction in annual water discharge since 1956-2000, the average annual sulfate flux from 2013 to 2015 exceeded historical values, with approximately 45 % of riverine sulfate derived from anthropogenic input, and the flow-weighted average δ34S-SO42- and δ18O‒SO42- values changed to 7.9 ± 1.2 ‰ and 6.4 ± 0.2 ‰. These findings illuminated the profound impacts of anthropogenic inputs on riverine sulfate flux in Qin River and offer a robust methodology for partitioning aqueous pollution sources and delineating their transport mechanisms in the complex environmental settings.

Pharmaceutically active micropollutants: origin, hazards and removal

Pharmaceuticals, recognized for their life-saving potential, have emerged as a concerning class of micropollutants in the environment. Even at minute concentrations, chronic exposure poses a significant threat to ecosystems. Various pharmaceutically active micropollutants (PhAMP), including antibiotics, analgesics, and hormones, have been detected in underground waters, surface waters, seawater, sewage treatment plants, soils, and activated sludges due to the absence of standardized regulations on pharmaceutical discharge. Prolonged exposureof hospital waste and sewage treatment facilities is linked to the presence of antibiotic-resistant bacteria. Conventional water treatment methods prove ineffective, prompting the use of alternative techniques like photolysis, reverse osmosis, UV-degradation, bio-degradation, and nano-filtration. However, commercial implementation faces challenges such as incomplete removal, toxic sludge generation, high costs, and the need for skilled personnel. Research gaps include the need to comprehensively identify and understand various types of pharmaceutically active micropollutants, investigate their long-term ecological impact, develop more sensitive monitoring techniques, and explore integrated treatment approaches. Additionally, there is a gap in understanding the socio-economic implications of pharmaceutical pollution and the efficacy of public awareness campaigns. Future research should delve into alternative strategies like phagotherapy, vaccines, and natural substance substitutes to address the escalating threat of pharmaceutical pollution.

Investigation and comparative analysis of ecological risk for heavy metals in sediment and surface water in east coast estuaries of India

The sediments and surface water from 8 stations each from Dhamara and Paradeep estuarine areas were sampled for investigation of heavy metals, Cd, Cu, Pb, Mn, Ni, Zn, Fe, and Cr contamination. The objective of the sediment and surface water characterization is to find the existing spatial and temporal intercorrelation. The sediment accumulation index (I_sed), enrichment index (I_En), ecological risk index (I_EcR) and probability heavy metals (p-HMI) reveal the contamination status with Mn, Ni, Zn, Cr, and Cu showing permissible (0 ≤ I_sed ≤ 1, I_En ˂ 2, I_EcR ≤ 150) to moderate (1 ≤ I_sed ≤ 2, 40 ≤ R_f ≤ 80) contamination. The p-HMI reflects the range from excellent (p-HMI = 14.89-14.54) to fair (p-HMI = 22.31-26.56) in off shore stations of the estuary. The spatial patterns of the heavy metals load index (I_HMc) along the coast lines indicate that the pollution hotspots are progressively divulged to trace metals pollution over time. Heavy metal source analysis coupled with correlation analysis and principal component analysis (PCA) was used as a data reduction technique, which reveals that the heavy metal pollution in marine coastline might originate from redox reactions (FeMn coupling) and anthropogenic sources.