Surface Water Concentrations Research Articles

Toxicity of selected pharmaceuticals and their mixtures to the aquatic indicators Daphnia magna and Aliivibrio fischeri.

Despite the benefits derived from the use of pharmaceuticals, these compounds are currently considered contaminants of emerging concern because of their presence and persistence in the environment. This study aimed to determine the toxicity of 27 pharmaceuticals and the interaction effects of binary mixtures of selected compounds towards two model organisms: the microcrustacean Daphnia magna and the bacterium Aliivibrio fischeri (Microtox test). Six compounds, namely polymyxin B, polymyxin E, fluoxetine, diphenhydramine, clenbuterol and ketoprofen exhibited moderate toxicity towards D. magna. Additionally, three compounds (cefotaxime, polymyxin B, polymyxin E) also showed a moderate toxic effect on A. fischeri. The comparison of such results with model estimations showed inaccuracy in the predicted data, highlighting the relevance of experimental ecotoxicological assays. The assayed mixtures contained four selected drugs of high-hazard according to their reported concentrations in wastewater and surface water (diphenhydramine, trimethoprim, ketoprofen, and fluoxetine); data revealed interactions only in the fluoxetine-containing mixtures for D. magna, while all mixtures showed interactions (mostly synergistic) for Microtox. Chronic effects on the reproduction of D. magna were observed after exposure to fluoxetine and diphenhydramine, although higher sensitivity was determined for the latter, while the mixture of these compounds (which showed acute synergy in both models) also affected the reproduction patterns. Nonetheless, all the effects described at the acute or chronic level (for individual compounds or mixtures) were determined at concentrations higher than commonly reported at environmental levels. This work provides valuable ecotoxicological information for the risk assessment of pharmaceuticals and their mixtures in the environment.

Optimizing surface water quality parameters in monitoring networks in a developing sub-tropical region with high anthropogenic pressure (São Paulo State Brazil).

Efficient water quality monitoring is a central aspect of water resources management, especially in developing countries, where water quality is under high anthropogenic pressure and resources for monitoring are usually limited. Here, we evaluated an alternative to optimize water quality parameters (WQPs) in the water quality monitoring network (WQMN) of the most populous state in Brazil (São Paulo State). We focused on the monitoring goal of identifying water quality temporal trends, selecting WQPs with high statistical explanatory power and those that were particularly sensitive to natural and anthropogenic perturbations. We considered 12 initial WQPs (dissolved copper, total zinc, total lead, total chromium, total mercury, total nickel, total cadmium, total iron, total manganese, total aluminum, total copper, and surfactant) with data from 2004 to 2018 for 56 monitoring sites distributed across four major watersheds with contrasting land uses in the state. We performed principal component analysis, followed by objective criteria to refine WQPs recommendation for the WQMN. Our results indicated the opportunity of reducing at least one parameter from the initial set of WQPs in all watersheds. Total iron, total manganese, and total aluminum were the most relevant initial WQPs, since their maintenance in monitoring were indicated in all the analyzed cases. Natural watershed conditions (e.g., geomorphology and water geochemistry) potentially governed their concentrations in surface water. On the other hand, total mercury, total chromium, and dissolved copper had the maintenance indicated in only one watershed, especially due to concentrations consistently below the respective limits of quantification (LoQs). Future investigations can complement our recommendations for these parameters, since changes in LoQs could throw another light on water quality spatial and temporal variations and the need for reference areas for assessing baseline conditions can also be relevant. Moreover, we argue that depending on the monitoring goals of the WQMN, additional sampling of biota and sediments could be useful as many of the studied WQPs' bioconcentrate. Our results illustrated an alternative approach towards adaptive monitoring in São Paulo state in accordance with the intended monitoring goal (i.e., water quality temporal trends), converging with the more flexible monitoring adopted in well-structured networks worldwide. While we did not cover other monitoring goals in our study (as the control of illegal discharge of effluents or industrial spills, for example), we expect our methodology can contribute to establishing technical guidelines for reviewing the existing WQMNs in Brazil and other developing countries with similar challenges.

Mechanisms of Irrigation Water Levels on Nitrogen Transformation and Microbial Activity in Paddy Fields

Nitrogen is a vital nutrient for rice growth; however, its inefficient use often results in nutrient loss, environmental degradation, and the emission of greenhouse gases. In this study, a rice paddy simulation was conducted under different water levels (1–4 cm), incorporating a comprehensive analysis of nitrogen dynamics, environmental factors, and microbial communities to evaluate the impact of water levels on nitrogen concentrations and microbial composition. The results indicated that the water level had a greater impact on nitrogen concentrations in surface water than in soil water. Compared to low water level conditions (1 cm), the average concentrations of ammonium nitrogen, nitrate nitrogen, and nitrite nitrogen in surface water under 2–4 cm water levels decreased by approximately 53.8%, 36.7%, and 78.9%, respectively. Water levels also influenced the microbial composition and nitrogen cycling in paddy soil, with lower water levels promoting aerobic processes such as nitrification, while higher water levels facilitated anaerobic processes such as denitrification and dissimilatory nitrate reduction to ammonium. Correspondingly, microbial composition shifted, with aerobic bacteria predominating in shallow water conditions and anaerobic bacteria flourishing under deeper water. These findings suggest that optimized water management, particularly through shallow irrigation, may mitigate nitrogen loss and improve nitrogen use efficiency. Nevertheless, additional field studies are necessary to validate these results and explore their interaction with other agricultural practices.

Groundwater-surface water exchanges in an alluvial plain in southern France subjected to pumping: A coupled multitracer and modeling approach

Study regionThe study was conducted in an alluvial plain between the Rhône and the Ouvèze Rivers (in the southeast of France) extensively exploited for drinking water. The research area is characterized by significant groundwater-surface interactions influenced by groundwater pumping activities. Study focusThe aim of this study is to enhance the understanding of interactions between rivers and alluvial aquifers by combined multi-tracer and numerical modeling approaches. Over an 18-month period, groundwater temperature, piezometric levels, and river surface water levels were continuously monitored. Field campaigns focused on conductivity, stable isotopes of water, and radon-222 activity concentration in both groundwater and surface water. Radon-222 was used to quantify water exchanges between the river and the aquifer. A MODFLOW model, calibrated using piezometric data and PEST, was employed to simulate groundwater flow and reactive transport of radon-222 using MT3DMS. New hydrological insights for the regionThe study reveals that river water recharges the aquifer, with radon-222 data delineating this recharge zone. The methodology extended the interpretation of periodic groundwater temperature signals to isotopic signals, allowing the identification of dispersivity and Darcy's velocity. The Ouvèze River was found to contribute approximately 55 % of the pumping water supply, alongside the Rhône. These findings provide valuable insights for sustainable water resource management, demonstrating the relevance of using natural tracers in scenarios where artificial tracers are impractical.

Delving into nitrogen and phosphorus dynamics in shallow eutrophic lakes: Multi-interface response to freeze-thaw cycles

Assessing the impact of freeze-thaw cycles on nutrient transfer in lakes is crucial for addressing the global eutrophication of freshwater ecosystems in cold and arid regions. However, available information about the dynamics of nitrogen (N) and phosphorus (P) release during intact freeze-thaw cycles, especially in the sediment–porewater–water column continuum of lakes, is limited. This study collected the samples during ice-covered (January) and non-ice-covered (April, July, and October) periods. The changes in total nitrogen (TN) and total phosphorus (TP) were analyzed to estimate their release fluxes from the sediment-water interface. Both redundancy analysis (RDA) and variance partitioning analysis (VPA) were used to explore the effects of environmental variables on N and P. The results indicated that during the ice-covered period (ICP), the surface water content of different forms of N and P was lower than that of the overlying water, whereas the opposite was true during the non-ice-covered period (NICP). The overall trend for the different forms of N was TN > DIN > NH4-N > NO3-N > NO2-N, and for P, it was TP > PP > DTP > DOP>DIP. The vertical profiles of the porewater TN and TP generally demonstrated an increase followed by a decrease from the surface to the bottom, with an inflection point at 15 cm. Sediment TN and TP trends over time matched porewater trends, with both being spatially highest at the lake inlet. ICP sediments acted as sinks for TN and TP, and NICP sediments acted as sources. N and P in the water column were significantly correlated mainly with physicochemical indicators, whereas sediment contributed positively to TN and TP in the porewater. VPA indicated that environmental factors explained 46.45 % of the variation in TN and TP in the porewater. These findings emphasize the importance of freeze-thaw cycling processes in driving N and P nutrient enrichment, source-sink effects, and multi-media coupling in shallow lakes in arid plateau regions.

Fate and mass budget of microplastic in the Beibu Gulf, the northern South China sea

This study investigated the distribution, abundance, and mass budget of microplastics (MPs) in the Beibu Gulf, Northern South China Sea, focusing on their ecological significance and anthropogenic influence. Microplastics were found in all water and sediment samples, with concentrations in surface water ranging from 0.10 to 0.89 items/m³, and in bottom water from 0 to 0.85 items/m³. Sediment samples exhibited higher levels, ranging from 13.12 to 155.59 items/kg. The spatial distribution revealed higher concentrations along the northern Gulf and Guangxi Province, suggesting significant human influence from coastal activities, such as mariculture and industrial discharges. The study utilized both field data and a mass balance box model to estimate the MPs mass budget, revealing that oceanic flow and riverine discharge are major contributors, accounting for 49% and 52% of MPs, while Atmospheric deposition and sedimentation represents 8% and 1%, respectively. The inventory estimation calculated that 0.24 tons of MPs exist in the water column, and 137 tons in the sediment, emphasizing the substantial environmental burden posed by these pollutants. The significance of this research lies in its comprehensive assessment of MPs in a semi-enclosed gulf, providing critical insight into the role of coastal and hydrodynamic processes in MP distribution. This study highlights the urgent need for better waste management practices in coastal regions to mitigate microplastic pollution and its detrimental effects on marine ecosystems.

Substantial trace metal input from the 2022 Hunga Tonga-Hunga Ha’apai eruption into the South Pacific

The January 2022 eruption of the Hunga Tonga-Hunga Ha’apai (HTHH) volcano discharged 2,900 teragrams of ejecta, most of which was deposited in the South Pacific Ocean. Here we investigate its impact on the biogeochemistry of the South Pacific Gyre (SPG) using samples collected during the GEOTRACES cruise GP21 in February-April 2022. Surface water neodymium isotopes and rare earth element compositions showed a marked volcanic impact in the western SPG, potentially extending to the eastern region. Increasing trace metal concentrations in surface waters and chlorophyll-a inventories in euphotic layers between the eastern and western SPG further suggest that the volcanic eruption supplied (micro)nutrients potentially stimulating a biological response. We estimate that the HTHH eruption released up to 0.16 kt of neodymium and 32 kt of iron into the SPG, which is comparable to the annual global dust-borne Nd flux and the annual dust-borne Fe flux to the entire SPG, respectively.

Metabolic pathways regulated by strigolactones foliar spraying enhance osmoregulation and antioxidant defense in drought-prone soybean

BackgroundDrought stress is a significant abiotic stressor that hinders growth, development, and crop yield in soybeans. Strigolactones (SLs) positively regulate plant resistance to drought stress. However, the impact of foliar application of SLs having different concentrations on soybean growth and metabolic pathways related to osmoregulation remains unknown. Therefore, to clarify the impact of SLs on soybean root growth and cellular osmoregulation under drought stress, we initially identified optimal concentrations and assessed key leaf and root indices. Furthermore, we conducted transcriptomic and metabolic analyses to identify differential metabolites and up-regulated genes.ResultsThe results demonstrated that drought stress had a significant impact on soybean biomass, root length, root surface area, water content and photosynthetic parameters. However, when SLs were applied through foliar application at appropriate concentrations, the accumulation of ABA and soluble protein increased, which enhanced drought tolerance of soybean seedlings by regulating osmotic balance, protecting membrane integrity, photosynthesis and activating ROS scavenging system. This also led to an increase in soybean root length, lateral root number and root surface area. Furthermore, the effects of different concentrations of SLs on soybean leaves and roots were found to be time-sensitive. However, the application of 0.5 µM SLs had the greatest beneficial impact on soybean growth and root morphogenesis under drought stress. A total of 368 differential metabolites were screened in drought and drought plus SLs treatments. The up-regulated genes were mainly involved in nitrogen compound utilization, and the down-regulated metabolic pathways were mainly involved in maintaining cellular osmoregulation and antioxidant defenses.ConclusionsSLs enhance osmoregulation in soybean plants under drought stress by regulating key metabolic pathways including Arachidonic acid metabolism, Glycerophospholipid metabolism, Linoleic acid metabolism, and Flavone and flavonol biosynthesis. This study contributes to the theoretical understanding of improving soybean adaptability and survival in response to drought stress.

The character of Lake Kishkensor contamination in the area of underground nuclear explosions at the Semipalatinsk Test Site territory

The timely identification of areas where man-made radionuclides migrate through water streams is highly important for the territory of the former Semipalatinsk Test Site since the aquatic environment is currently a source of secondary contamination of environment. This article presents research findings on radioactively contaminated Lake Kishkensor located at the Semipalatinsk Test Site territory. As a result of this research, a new locally contaminated spot was discovered in the vicinity of the “Balapan” test site. Lake Kishkensor was found to be contaminated with man-made 3H and 90Sr. The 3H activity concentration in surface waters reached 430 kBq/L, and the concentration of 90Sr reached 100 Bq/L. In the sediments, the 3H activity concentration reached 700 kBq/kg, while that of 90Sr and 239+240Pu reached 310 Bq/kg and 250 Bq/kg, respectively. Ground water was found to be a source of surface water and sediment contamination. The monitoring results showed that the contamination level of the lake largely depended on the season and the inflow of contaminated ground water.

Hydrological processes in multi-layered aquifers of a karst watershed with coal mining activity: Insights from hydrochemistry and isotopes

Study regionThe Laochang Karst watershed (LCKW) is located in eastern Yunnan Province, southwestern China. It is the representative karst area affected by coal-mining activities in southwestern China. Study focusIdentifying hydrological processes of multi-layered aquifers in karst watersheds is challenging due to complex natural and anthropogenic processes. This study attempts to clarify the hydrological conceptual model of the LCKW using hydrochemistry and D, O, Sr, S, and C isotopes. New hydrological insights for the regionSurface water and multi-layered groundwater have the hydrochemical types of SO4-Ca·Mg, HCO3·SO4-Ca, and HCO3-Ca. Meteoric water and condensate were the major recharge sources. The main processes dominating hydrochemical compositions consist of sulfide oxidative dissolution, carbonate dissolution, positive cation exchange, and agricultural activities. Elevated SO42− concentration in the mine water, river water and shallow coalbed water mainly originated from the oxidation of pyrite in the coal-bearing strata of the Longtan Formation. whereas the deeper layers and groundwater away from the mines were hardly contaminated by SO42− due to the presence of aquiclude. HCO3− concentrations of surface water and multi-layered groundwater were mainly derived from carbonate dissolution and soil CO2, and mine water was also influenced by atmospheric CO2. Positive cation exchange contributed to increasing Na+ concentration. Agricultural activities contributed NO3−, Cl−, and K+ ions in aquifers, especially near large karst fallout caves. A hydrological model of multi-layered aquifers in the LCKW was built based on the above results. These findings will provide valuable guidance for understanding the hydrological processes of complex karst watersheds worldwide.

Assessment of the activity concentration of radon and its health hazard in surface water around the Rooppur Nuclear Power Plant (RNPP) site, Bangladesh

ABSTRACT Radon is a colourless, unscented, radioactive inert gas. As a gaseous element, Rn-222 can be effectively breathed in, leading to a health hazard. The main objective of this study is to measure the amount of Rn-222 concentration in surface water and its associated health hazards around the Rooppur Nuclear Power Plant (RNPP) construction site area in Bangladesh. Twenty water samples were collected each year (2022 and 2023) from different specific locations of the Padma River and investigated for radon concentration through a Durridge RAD7 detector with RAD H2O accessories. The range of radon activity in surface water measured from 0.070 ± 0.035 to 0.385 ± 0.211 BqL−1 with a mean activity of 0.194 ± 0.114 BqL−1 in the year 2022 and in the year 2023, the range of radon activity in surface water measured from 0.035 ± 0.070 to 0.455 ± 0.239 BqL−1 with an average activity of 0.228 ± 0.140 BqL−1. All the radon concentration results were below the recommended limits of WHO (100 BqL−1) and USEPA (11.1 BqL−1). The ranges of annual effective dose (AED) were from 0.1911 to 1.051 µSvy−1 and from 0.095 to 1.242 µSvy−1 in the years 2022 and 2023, respectively, which were lower than the AED recommended by WHO (0.1 mSvy−1). The mean values of excess lifetime cancer risk are 0.0021 × 10−3 and 0.0025 × 10−3 in the years 2022 and 2023, respectively, which were lower than the average standard value recommended by UNSCEAR (0.29 × 10−3). The result of this investigation can be applied as baseline data for radon concentration measurement in the under-construction nuclear power plant site area vicinity of Bangladesh.

Agricultural Contribution of Chloride to a Saturated Riparian Buffer System: A Case Study in Central Illinois

ABSTRACT Increases in chloride concentrations in surface water and groundwater from anthropogenic sources is a growing concern throughout the world. In the midwestern United States, the agriculture contribution of chloride may elevate concentrations in surface and groundwater systems. A saturated riparian buffer (SRB), installed to reduce nutrient input into an adjacent stream, and the groundwater water upgradient were investigated to identify sources of chloride and to quantify the agricultural contribution. During a 7-year period, over 2,200 water samples collected from 35 wells, a diversion box, and a stream were analyzed for major anions. Additionally, the waters from four quarterly (seasonal) samplings (n = 155) during the seventh year were analyzed for cations. A cumulative probability curve identified three populations of chloride: (1) upgradient shallow groundwater; (2) diversion box (waters drained from an agricultural field), downgradient shallow groundwater (representing the SRB), diamicton groundwater (waters collected deeper from within the unweathered parent material); and (3) stream water. A background chloride concentration was established at 3.9 mg/L. Elevated concentrations above the background level coupled with principal component analysis suggest agricultural contribution from the diverted tile-drainage waters was a source of chloride. In winter and spring, chloride concentrations were highest in the diversion box, while up-gradient wells were the lowest. Waters downgradient of the diversion tiles had chloride concentrations lower than the tile but higher than the upgradient waters due to mixing of the diverted tile water and the upgradient groundwater. For the specific site, agriculture contributes chloride, but at concentrations below the chronic threshold of 230 mg/L.

Subsurface influences on watershed nutrient concentrations and loading in a clay dominated agricultural system

Water quality issues in the Great Lakes Basin persist despite management and monitoring efforts. With changing land use and climatic conditions, the need for improved understanding of nutrient loss from agricultural field to surface water is imperative to reduce consequences on human and aquatic life, such as perpetual algal blooms and contaminated drinking water. There remains a gap in holistic rural water management studies that investigate the understanding of the water cycle in rural settings and the interconnections between different components of the water cycle, including artificial drainage. In the current study, a year-round paired investigation of subsurface and nutrient dynamics was conducted in a small, intensively managed agricultural watershed within southwestern Ontario, Canada. Nutrients (Nitrate and Phosphorus) and stable isotopes of water (δ2H and δ18O) were sampled at varying scales (i.e., field and watershed), from multiple hydrologic components (e.g., groundwater, surface water, tile flow, and soil water), from 2020 to 2022. Results indicate that nutrient concentrations in surface water were elevated during the growing season, while nutrient loading was greater during the non-growing season in surface water. Monthly nitrate loads were found to be significantly (p < 0.01) related to groundwater elevation, soil moisture and tile flow, whereas total phosphorus loading was found to be significantly (p < 0.01) related to soil moisture and tile flow. δ2H and δ18O signatures revealed that during the growing season nutrient movement was predominantly through interflow pathways (including tile drainage) comprised of event-water. In the non-growing season, there was an increased subsurface influence on nutrient transport. This study highlights the importance of including subsurface characterization in nutrient management studies. A comprehensive understanding of varying seasonal hydrologic mechanisms that control nutrient movement within an agricultural watershed is essential to sustain growing rural communities.

Hydrocarbons in waters and bottom sediments of the coastal areas of the Caucasian sector of the Black Sea (2021–2023)

The current level of aliphatic and polycyclic aromatic hydrocarbons was determined in suspended particulate matter of waters (mainly in surface waters) and in upper layer of bottom sediments of coastal areas in the Caucasian sector of the Black Sea of the Russian Federation (September 2021, May and September 2022, March 2023). IR method was used to determine the aliphatic hydrocarbons, and the method of high performance liquid chromatography was employed for PAHs. The average concentration of aliphatic hydrocarbons was ≈20 μg/L and for polycyclic aromatic hydrocarbons ≈130 ng/L in suspended particulate matter in open surface waters of Gelendzhik and Golubaya bays. Their content naturally increased as they approached the coast. Despite the decrease in hydrocarbon concentrations in surface waters in recent years, the Kerch Strait and Novorossiysk remain the most polluted areas as before. Higher concentrations in the waters of the Taman Peninsula may be caused by the seepage of hydrocarbons from the sedimentary layer. Hydrocarbons are accumulated in bottom sediments, that leads to their rising portion in total organic carbon (e.g., aliphatic hydrocarbons up to 14.2 % in the Tuapse region and 13.1 % in the Novorossiysk region). Along with contamination from anthropogenic sources, natural processes also affect the hydrocarbon levels such as high biological productivity of the area and fluid flows from the sediment layer.

Nitrate sources and transformation in surface water and groundwater in Huazhou District, Shaanxi, China: Integrated research using hydrochemistry, isotopes and MixSIAR model

Global water resources affected by excessive nitrate (NO3−) have caused a series of human health and ecological problems. Therefore, identification of NO3− sources and transformations is of pivotal significance in the strategic governance of widespread NO3− contaminant. In this investigation, a combination of statistical analysis, chemical indicators, isotopes, and MixSIAR model approaches was adopted to reveal the hydrochemical factors affecting NO3− concentrations and quantify the contribution of each source to NO3− concentrations in surface water and groundwater. The findings revealed that high groundwater NO3− concentration is concentrated in the southwestern region, peaking at 271 mg/L. NO3− concentration in the Wei River and Yuxian River exhibited an increase from upstream to downstream, but in the Shidi River and Luowen River, its concentration was highest in the upstream. Groundwater NO3− has noticeable correlation with Na+, Ca2+, Mg2+, Cl−, HCO3−, TDS, EC, and ORP. In surface water, NO3− level is significantly correlated with NH4+ and ORP. Major sources of NO3− in surface and groundwater comprise manure & sewage and soil nitrogen. Source contribution for surface water was calculated by MixSIAR model to obtain soil nitrogen (57.7%), manure & sewage (23.8%), chemical fertilizer (12%), and atmospheric deposition (6.4%). In groundwater, soil nitrogen and manure & sewage accounted for 19% and 63.8% of nitrate sources, respectively. Both surface water and groundwater exhibited strong oxidation, with nitrification the primary process. It is expected that this study will provide insights into the dynamics of NO3− and contribute to the development of effective strategies for mitigating NO3− contaminant, leading to sustainable management of water resources.

Comparative Analysis of Concentrations of Heavy Metals in Surface Water of Nafada, Ashaka and Almakashi Corridors of River Gongola, Nigeria

A study on comparative analysis of heavy metals concentrations in surface water was carried out in three selected stations: Nafada, Ashaka and Almakashi along the corridors of River Gongola in Gombe state for a period of eighteen months. The water samples were collected in triplicate from the sampling stations. Water samples were collected using sampling bottles of 250ml dipped below the water surface for water collection. Zinc, lead, copper, cadmium and manganese were determined using Atomic Absorption Spectrophotometer. The result elucidates that most of the heavy metals were found to be within the recommended ranges as compared to standard limits. The result of concentrations of heavy metals in the surface water elucidates that there was a significant difference (P&gt;0.05) among the months with respect to zinc and there was no significant difference in the concentration of lead (P&lt;0.05). The concentrations follow the order (Zn &gt;Cd&gt;Cu&gt;Mn&gt;Pb). The higher concentration of heavy metals was found in Ashaka corridors with Zinc concentration ranging between 0.99±0.01 and 0.33±0.01, Cadmium 0.88±0.02 and 0.03±0.00, Cupper 0.58±0.02 and 0.14±0.02, Manganese 0.87±0.56 and 0.17±0.01, Lead 0.28±0.36 and 0.01±0.01. The wastewater from the cement effluent factory in Ashaka might have impacted negatively on the water chemistry by elevating the levels of some heavy metals. Therefore, more intensive treatment of the factory effluents before discharging into the River Gongola is recommended.

Quantitative assessment of Cd sources in rice grains through Cd isotopes and MixSIAR model in a typical e-waste dismantling area of Southeast China

Identification of Cd sources and quantification of their contribution to rice grain Cd is crucial for controlling accumulation of this toxic metal in rice grains. However, accurate assessment of the contribution of different Cd sources to grain Cd concentration in rice under actual field conditions is a challenge. In this study, we determined Cd concentration and their isotopic compositions in rice grains with respect to three potential Cd sources around an e-waste dismantling area in Taizhou City, Zhejiang Province, China. Results demonstrated that average Cd concentrations in grains, surface soils, atmospheric deposition and surface water were 0.32, 0.91, 1.99 mg kg−1 and 2.02 μg L−1, respectively. The δ114/110Cd values of grains, surface soils, surface water and atmospheric deposition ranged from 0.00 ‰ to 0.31 ‰, −0.21 ‰ to 0.14 ‰, −0.04 ‰ to 0.47 ‰, and − 0.25 ‰ to −0.18 ‰, respectively. The MixSIAR model indicated that contribution of soils, irrigation water and atmospheric deposition to grain Cd was 56.8 %, 24.8 % and 18.4 %, respectively, demonstrating soils as the major source of grain Cd in the study area. This study also highlighted significant contribution of irrigation water and atmospheric deposition to Cd concentration in rice grains. The Cd isotopic analysis provides a practical approach for source apportionment of grain Cd and data support for controlling Cd accumulation in rice around the e-waste dismantling area.

Molecular and Dissociative Adsorbed Water Concentration and Surface Protonic Conduction in Nanocrystalline TiO2.

Surface protonic conduction in porous nanocrystalline oxides is commonly involved in catalytic processes. The configuration of surface adsorbed water on oxides plays a crucial role in surface protonic conduction. However, studies on the impact of complex surface adsorbed water configuration on the surface water concentration and diffusivity remain limited, and hinder an in-depth understanding of surface proton transport mechanisms, and the design of better surface proton conductors. Here, in situ Raman spectroscopy is utilized to quantitatively identify the contribution of dissociative and molecular adsorbed water components on porous nanocrystalline TiO2 surfaces between 25 and 200°C. The variations in molecular and dissociative adsorbed water concentration agree with the predominant surface proton conduction mechanisms at three different temperature stages. From 40 to 125°C, the reduced coverage of molecular adsorbed water layer results in the decreasing proton diffusivity. Water dissociation on the nanocrystalline TiO2 surface is easier in wet N2 than in wet O2, resulting in higher proton conductivity in wet N2; while the surface proton diffusivities in these two atmospheres are similar. The in situ spectroscopy technique enables the improvement of surface proton conducting oxides through quantitative evaluation and modulation of the surface proton concentration and diffusivity.

Multi-evidences investigation into spatiotemporal variety, sources tracing, and health risk assessment of surface water nitrogen contamination in China

A comprehensive understanding of nitrogen pollution status, especially the identification of sources and fate of nitrate is essential for effective water quality management at the local scale. However, the nitrogen contamination of surface water across China was poorly understood at the national scale. A dataset related to nitrogen was established based on 111 pieces of literature from 2000 to 2020 in this study. The spatiotemporal variability, source tracing, health risk assessment, and drivers of China's surface water nitrogen pollution were analyzed by integrating multiple methods. These results revealed a significant spatiotemporal heterogeneity in the nitrogen concentration of surface water across China. Spatially, the Haihe River Basin and Yellow River Basin were the basins where surface water was seriously contaminated by nitrogen in China, while the surface water of Southwest Basin was less affected. Temporally, significant differences were observed in the nitrogen content of surface water in the Songhua and Liaohe River Basin, Pearl River Basin, Southeast Basin, and Yellow River Basin. There were 1%, 1%, 12%, and 46% probability exceeding the unacceptable risk level (HI＞1) for children in the Songhua and Liaohe River Basin, Pearl River Basin, Haihe River Basin, and Yellow River Basin, respectively. The primary sources of surface water nitrate in China were found to be domestic sewage and manure (37.7%), soil nitrogen (31.7%), and chemical fertilizer (26.9%), with a limited contribution from atmospheric precipitation (3.7%). Human activities determined the current spatiotemporal distribution of nitrogen contamination in China as well as the future development trend. This research could provide scientifically reasonable recommendations for the containment of surface water nitrogen contamination in China and even globally.

Practical estimation and use of natural background concentrations in surface waters for nickel in Europe.

Estimates of ambient background concentrations in surface waters, referred to as natural background concentrations (NBCs) in European guidance documents, may be an important factor in determining whether a monitoring site meets the legally binding Environmental Quality Standard (EQS) when assessing naturally occurring substances. Here, we focus on utilizing routine regulatory surface water monitoring data to provide risk assessors and environmental practitioners with a transparent, implementable, repeatable, and resource-effective approach to estimate NBCs. The methodology does not use additional environmental sampling beyond that which is routine or require advanced statistical methods, or the incorporation of highly specialist, and not always readily accessible, local knowledge. It determines both whether a site is suitable for NBC assessment as well as the identification of suitable surrogate sites and local NBCs using 11 criteria: six for identifying if a site is suitable for NBC correction, and five for identifying suitable surrogate sites for local NBC values. The criteria consider both the extent of any EQS exceedance, after accounting for bioavailability in line with the European guidance and potential anthropogenic impacts at the site, and can be applied in a simple sequential procedure. The method has been applied to derive NBCs for nickel on three case-study countries-Cyprus, France, and Spain-to determine its useability and impact on compliance. The methodology presented addresses a gap in the current guidance regarding the practical and consistent implementation of NBCs and could be applied to other naturally occurring substances in an EQS or Water Quality Guideline compliance assessment process. Integr Environ Assess Manag 2024;00:1-14. © 2024 WCA Environment Ltd and NiPERA Inc. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).