The adverse health effects associated with the inhalation and ingestion of naturally occurring radon gas produced during the uranium decay chain mean that there is a need to identify high-risk areas. This study detected radon-prone areas using a geographic information system (GIS)-based probabilistic and machine learning methods, including the frequency ratio (FR) model and a convolutional neural network (CNN). Ten influencing factors, namely elevation, slope, the topographic wetness index (TWI), valley depth, fault density, lithology, and the average soil copper (Cu), calcium oxide (Cao), ferric oxide (Fe₂O₃), and lead (Pb) concentrations, were analyzed. In total, 27 rock samples with high activity concentration index values were divided randomly into training and validation datasets (70:30 ratio) to train the models. Areas were categorized as very high, high, moderate, low, and very low radon areas. According to the models, approximately 40% of the study area was classified as very high or high risk. Finally, the radon potential maps were validated using the area under the receiver operating characteristic curve (AUC) analysis. This showed that the CNN algorithm was superior to the FR method; for the former, AUC values of 0.844 and 0.840 were obtained using the training and validation datasets, respectively. However, both algorithms had high predictive power. Slope, lithology, and TWI were the best predictors of radon-affected areas. These results provide new information regarding the spatial distribution of radon, and could inform the development of new residential areas. Radon screening is important to reduce public exposure to high levels of naturally occurring radiation.

Nitrogen pollution of groundwater has created problems worldwide. Riparian zones form a connection hub for terrestrial and aquatic ecosystems. As a potential source of ammonium in groundwater, aquitards have an important effect on the environment of riparian zones. The spatial distribution and factors influencing the ammonium content in the riparian zone aquitard of a small watershed were analyzed through three geological boreholes with increasing distances from the river: boreholes A > B > C. The results show that the distribution of ammonium was closely related to the lithology of sediments. Under the influence of the river and floods, the average content of ion exchange form of ammonium of sediments in borehole A (stable sedimentary environment) was 94.31 mg kg⁻¹, accounting for 21.2% of the transferable ammonium. The average proportions of ion exchange form of ammonium in the transferable ammonium of boreholes B and C (unstable sedimentary environment) were 19.1% and 17.4%, respectively. The carbonate and iron-manganese oxide forms of ammonium content of sediments in three boreholes were 0.96–15.28 mg kg⁻¹ and 2.3–54.4 mg kg⁻¹, respectively; this was mainly affected by the pH and Eh of the sedimentary environment. Organic sulfide, the form of transferable ammonium of sediments mainly exists in organic matter. The ammonium content in pore water generally increased with depth and was mainly derived from the mineralization of humic-like organic matter in borehole A. The ammonium in pore water in boreholes B and C mixed with ammonium from the mineralization of organic matter and the desorption of ion exchange form ammonium within sediments. The ammonium content in the pore water (up to 5.34 mg L⁻¹) was much higher than the limit for drinking water of 0.5 mg L⁻¹ in China. Therefore, the aquitard has a high risk of releasing ammonium and poses a certain threat to the quality of groundwater.

The present study attempts to decipher the seasonal variations in hydro-geochemistry of groundwater in the Terekhol River Basin, western coastal region, Maharashtra, India. A total of 65 groundwater samples of post-monsoon (POMS) and pre-monsoon (PRMS) seasons were collected and analyzed for major ion composition using standard analytical procedures of APHA. Piper and Gibbs plots is used to elucidate the controlling factors which altering the groundwater composition. Scatter plots of ions indicate that major ions from lithologies exposed in the study area and anthropogenic activities are altering the groundwater chemistry. Statistical analysis includes correlation, factor analysis and cluster analysis used to interpret the hydrochemical data. As compared to the WHO drinking standards, all the groundwater samples are fit for drinking. Irrigation water suitability was ascertained based on SAR, %Na and KR indices. Overall, the groundwater chemistry in study area is reflects changes in natural processes rather than anthropogenic inputs.

Lanthanoids in the southern Gulf of California (GC) seawater are reported for the first time. Lanthanoids showed differences between peninsular and continental coastline, coastal or marine ecosystems, and dry or rainy season. The chondrite-normalized values showed high variability but followed a same pattern. Light lanthanoids were more enriched than heavy ones. Values of ∑Ln and La/Lu were higher in continental than peninsular coastlines, coastal than adjacent marine ecosystems, and rainy than dry season. Differences were related to the lithology and perturbation degree of the ecosystem watersheds. The chondrite-normalized patterns are typical of geological origin. Slightly negative Ce anomaly was related to the low levels of oxygen in water for the oxidation of Ce (III) to Ce (IV) and its posterior scavenging. Negative δEu anomaly is explained by an influx of fluvial and eolian materials from the upper continental, while a positive Eu anomaly related to hydrothermal vent inputs was non-evidenced.

Beach sediments of Kanyakumari at the southernmost India were evaluated for metals and trace elements and to assess their possible impact on coastal ecosystems. Positive correlations (except for Cd and Sr) between them indicated metamorphic lithologies and heavy mineral deposits as possible sources. Significant-extremely high enrichment and very high contamination of Th, Zr, Mo, Ti and U reflected the presence of different heavy minerals. The geo-accumulation index, however, mirrored their variable abundances at different sites. Association of Cd with P suggested the influence of anthropogenic solid waste from fishing industry. It might have caused >41-fold enrichment of Cd and the Fe- Mn-oxides possibly acted as scavengers for 13-fold enrichment of As compared to UCC. Concentrations of Zn and Cr between ERL and ERM in 13% and 93% of the samples, and Ni > ERM in 87% of sediments suggest their bioavailability to seawater with a potential risk for coastal aquifers.

Microplastics are contaminants of great concern all over the world. Microplastics constitute pollutants themselves; moreover, other contaminants such as metals are easily absorbed on their plastic surface, becoming bioavailable to marine biota such as zooplankton.We collected marine zooplankton from Mediterranean Sea to investigate trace elements associated with microplastics. Samples were subjected to visual sorting by a stereomicroscope, collected with sterile tweezers, pooled and subjected to sonication, filtration, and drying before being subjected to acid extraction. An ICP-MS was utilized for multi-elemental determination.Aluminum, iron, chromium, zinc, nickel, molybdenum, manganese, lead cobalt, and copper were found at concentrations of mg/kg while arsenic, vanadium, rubidium, and cadmium at level of μg kg⁻¹. Other elements such as silver, beryllium, bismuth, selenium, tin, and thallium were under the limit of quantitation. Lower levels of iron and manganese in samples from Italy were found in comparison to England and Brazil, while aluminum, copper, and zinc registered comparable values. The presence of metals in marine waters is strictly related to sediment lithology and anthropogenic inputs, but plastic plays a key role as vectors for metal ions in the marine system, being able to concentrate metals several order of magnitude higher than in surrounding waters and exerting potential toxicity for living beings after chronic exposure.

In addition to global population growth due to migration from rural areas to urban areas, population density is constantly increasing in certain regions, thereby necessitating the introduction of new settlements in these regions. However, in the selection of settlement areas, no sufficient preliminary examinations have been conducted; consequently, various natural disasters may cause significant life and property losses. Herein, the most suitable settlement areas were determined using GIS (geographic information systems) in Canik District, where the population is continuously increasing. Therefore, this study aimed to incorporate a new perspective into studies on this subject. Within the scope of the study, landslide and flood risks, which are among the most important natural disasters in the region, were primarily evaluated, and high-risk areas were determined. Elevation, slope, aspect, curvature, lithology, topographic humidity index (TWI), and proximity to river parameters were used to produce flood susceptibility maps. A digital elevation model (DEM) of the study area was produced using contours on the 1/25,000 scaled topographic map. The elevation, slope, aspect, curvature, and TWI parameters were produced from the DEM using the relevant analysis routines of ArcGIS software. The raster map of each parameter was divided into 5 subclasses using the natural breaks classification method. In the reclassified raster maps, the most flood-sensitive or flood-prone subclasses were assigned a value of 5, and the least sensitive subclasses were assigned a value of 1. Then, the reclassified maps of the 7 parameters were collected using the “map algebra” function of ArcGIS 10.5 software, and the flood susceptibility index (FSI) map of the study area was obtained. The flood susceptibility map of the study area was obtained by dividing the FSI into 5 subclasses (very low, low, moderate, high, and very high) according to the natural breaks classification method. Thereafter, suitable and unsuitable areas in terms of biocomfort, which affects people’s health, peace, comfort, and psychology and is significant in terms of energy efficiency, were determined. At the last stage of the study, the most suitable settlement areas that were suitable in terms of both biocomfort and low levels of landslide and flood risks were determined. The calculated proportion of such areas to the total study area was only 2.1%. Therefore, because these areas were insufficient for the establishment of new settlements, areas that had low landslide and flood risks but were unsuitable for biocomfort were secondarily determined; the ratio of these areas was calculated as 56.8%. The remaining areas were inconvenient for the establishment of settlements due to the risk of landslides and floods; the ratio of these areas was calculated as 41.1%. This study is exemplary in that the priority for the selection of settlement areas was specified, and this method can be applied for selecting new settlements for each region considering different criteria. Due to the risk of landslides or flooding in the study area, the areas unsuitable for establishing a settlement covered approximately 41.1% of the total study area. The areas that had low flood and landslide risks but were suitable for biocomfort constituted only 2.1% of the study area. In approximately 56.8% of the study area, the risk of landslides or floods was low, and these areas were unsuitable in terms of biocomfort. Therefore, these areas were secondarily preferred as settlement areas. The most suitable areas for settlements constituted only 0.19% of the total study area, and these areas will not be able to meet the increasing demand for settlement area. Therefore, it is recommended to select areas that do not have the risk of landslides and floods but are unsuitable for biocomfort. This study reveals that grading should be performed in the selection of settlement areas. When choosing a settlement area in any region, possible natural disasters in the region should be identified first, and these disasters should be ordered in terms of their threat potential. Moreover, biocomfort areas suitable for settlements should be considered. In the next stages of settlement area selection, the criteria that affect the peace and comfort of people, such as distance to pollution sources, distance to noise sources, and proximity to natural areas, should also be evaluated. Thus, a priority order should be created for the selection of settlement areas using various other criteria.

One hundred and ninety-six drinking water samples from the different regions of Tarragona province (Catalonia, Spain) were analysed to determine the gross alpha and beta activity. Individual alpha emitting isotope activities were also determined to evaluate a possible relationship between their radiological content and the lithological and hydrogeological formations present in the studied area. The results obtained showed that approximately 23% of the analysed samples, mainly from five of the evaluated regions, had a gross alpha index exceeding the parametric value of 0.1 Bq/L for waters intended for human consumption according to the current legislation. This could be related to the presence of natural radionuclides in these water samples. The differences between the radiological content in these samples could be related to the different lithological conditions of the areas included in this study. High activity levels of ²³⁴U, ²³⁸U, ²²⁴Ra, ²²⁶Ra and ²²⁸Ra were detected in specific samples, mainly from granitic and carbonate areas. This research also focuses on evaluating the radiological risk associated with water ingestion. In this regard, consuming 95.5% of the drinking water samples analysed would not imply a health risk to the population as the annual effective doses calculated were below 0.1 mSv/year. There was only one sample that exceeded this level with a value of 0.33 mSv/year. ²²⁶Ra activity concentration was the radionuclide that mainly contributed to this dose.

The present study provides surface water types and water quality indices (WQI) for 70 large coastal rivers of the Western Ghats (WG). Irrespective of seasons and lithology, concentration of cations (Ca²⁺ > Na⁺ > Mg²⁺ > K⁺) and anions (HCO₃⁻ > Cl⁻ >SO₄²⁻ > NO₃⁻ > PO₄³⁻) follow a typical trend all along the coast. The WG rivers can broadly be classified as calcium-bicarbonate-chloride (Ca²⁺-HCO₃⁻-Cl⁻) type. Pearson correlation analysis of major ions demonstrates natural sources influence on the riverine water composition across the WG region. Gibbs plot suggests water composition of these rivers is the result of the interaction of rock and precipitation. It means that ionic contributions from precipitation and chemical weathering of rock-forming minerals largely determine surface water quality. This biodiversity hotspot is facing high population pressure and anthropogenic activities. Despite it, quantitatively, all the physical parameters and chemical constituents are within the permissible limits of the World Health Organization (WHO) and Bureau of Indian Standards (BIS), thus making it suitable for drinking and domestic purposes. About 86% of the surface water samples are found to be suitable for irrigation (KR < 1) in non-monsoon seasons. Rivers near to Goa coast are only found unsuitable (KR > 1) for irrigation exclusively during non-monsoon seasons. From the majority of the calculated indices, it may be inferred that the river waters draining from the WG region are suitable for irrigation. Overall, the calculated WQI for studied rivers showed excellent to good water quality for drinking, agriculture, and aquatic life in monsoon seasons, which are then ranked from good to marginal in non-monsoon seasons.

The present study illustrates the delineation of the groundwater potential zones in one of the most critical and drought-affected areas under Bundelkhand region of Uttar Pradesh (India). Hydrological evaluations were carried out using GIS tools and remote sensing data which ultimately yielded several thematic maps, such as lineament density, land use/land cover, drainage density, lithology, slope, geomorphology, topographic wetness index (TWI), DEM, and soil. Thematic layers were assigned relative weightages as per their groundwater potential prospects under multi-criteria decision making (MCDM) method through analytical hierarchy process (AHP). To recognize the groundwater potential zone, weighted overlay analysis was also performed. Additionally, for testing of the Dempster-Shafer model, 16 wells in the study area have been selected. Based on the probability of the groundwater occurrence, the belief factor was equated to delineate groundwater potential zones which illustrate five different potential zones. According to the AHP model, the northwest side of the study area is characterized with very high potential zones whereas the northeast and southeast regions constitute medium and low groundwater potential zones respectively. According to the DS model, very high groundwater potential zones constitute 17% and the remaining area falls under low potential. Overall accuracy of the DS model is higher than AHP model.