Sulfate-reducing bacteria (SRB) are key mediators of sulfur and carbon cycling, with growing recognition of their role in metal immobilization in contaminated environments. This study investigates SRB community structure, abundance, and activity in a historically metal-polluted soil system subjected to seasonal porewater fluctuation and transient redox conditions. Molecular analyses targeting the dsrB gene revealed distinct SRB communities in topsoil and subsoil layers, with Desulfobaccales and Desulfomonilaceae showing a stronger capacity to adapt to high concentrations of As, Cd, Pb, and Zn and prevalent aerobic conditions in the top layers.Microscale geochemical evidence, supported by scanning electron microscopy, sulfur isotopes, and porewater chemistry, indicates that Zn and Cd undergo in situ transformation into poorly soluble ZnCdS phases within transiently anoxic microsites in the topsoil. The spatial distribution of these authigenic sulfides suggests localized SRB activity, independent of sulfide diffusion from deeper layers. In contrast, Pb and As showed no signs of sulfide mineral formation or vertical stratification, remaining largely unaffected by SRB activity.Seasonal changes in sulfate and bicarbonate concentration, alongside sulfur isotope fractionation, document the sensitivity of dissimilatory sulfate reduction to environmental forcing. Sulfide concentration stayed low in bulk porewater, in agreement with the instantaneous precipitation of hardly soluble ZnCdS phases in periods of SRB activity.These findings underscore the ecological resilience and biogeochemical relevance of SRB in anthropogenically disturbed environments and demonstrate their role in the in situ stabilization of toxic metals through microscale redox cycling.

Acid mine drainage (AMD) is one of the most serious threats to aquatic environments in mining areas, leading to low pH, elevated SO42- and Fe concentrations, and enrichment in trace elements (TEs) and rare earth elements (REEs). This study investigates the geochemistry of TEs and REEs in one of the most AMD-impacted areas in Poland - the Colorful Lakes in Wieściszowice. These pit lakes, formed in abandoned pyrite open pits, include Blue, Yellow, Purple, and Green Lakes. Three lakes (Blue, Yellow, Purple) and the Rdzawy Potok stream feeding Blue Lake were examined. The results indicate that pH is the primary factor controlling the geochemistry of both TEs and REEs. Waters of Blue Lake and the Rdzawy Potok stream (pH > 5) show higher concentrations of TEs and REEs in bottom sediments and lower concentrations in the water column compared to Yellow and Purple Lakes (pH < 3). TEs such as As, Mo, Sb, Se, Li, and Tl are associated with the less acidic waters, whereas typical AMD-related elements (Cu, Zn, Ni, Cr, Co, Mn) dominate in highly acidic lakes. Maximum REE concentrations reached 382.0 µg/L in Purple Lake waters and 59.6 mg/kg in bottom sediments of the Rdzawy Potok stream. The Colorful Lakes are characterized by enrichment in HREEs and MREEs, positive Gd anomaly, and distinct Tb anomaly in bottom sediments, indicating fractionation processes. A positive Eu anomaly was observed in less acidic environments, whereas under acidic conditions they occurred in the sediments, suggesting relatively higher mobility of Eu in less acidic settings. These findings highlight the role of AMD-affected pit lakes as natural laboratories for understanding the geochemical behavior of TEs and REEs in water-sediment systems.

The role of hydraulic parameters in sediment transport and heavy metals concentration still needs scientific research. In this study, GIS techniques, IBER (a 2D hydrodynamic modeling system) and statistical analysis were applied to assess heavy metals concentration, spatial distribution and sources. A total number of 30 surface sediment samples were collected from the Stare Miasto two-stage reservoir. Results showed that median values follow order Zn > Pb > Cu > Cr > Ni > Cd, which was characteristic for both parts of the reservoir. The overall calculated median concentrations of Zn, Pb, Cu, Cr, Ni, and Cd were 6.74, 1.66, 1.14, 0.99, 0.8, and 0.04 mg/kg. Analysis of heavy metals concentration shows that higher mean values were observed in the pre-dam part for all of the analyzed heavy metals. The highest risk was observed for Zn, Pb and Cd for all of the analyzed samples. Statistical analysis showed that heavy metals concentration is correlated with the fraction of sediments and distance from the inflow. Spearman’s rank correlation showed that hydraulic parameters affect heavy metals concentration. Critical diameter was negatively correlated with Cu while Froude number and velocity were negatively correlated with Cu and Zn concentrations. Also, it was observed that Cu concentrations in the main zone were positively correlated with specific discharge. Results showed that the two-stage construction of the reservoir has an impact on the limitation of sediments spatial distribution and helps to control pollution related to heavy metals.

Lake tourism includes activities both within the lake itself and in its immediate surroundings. These activities may lead to a range of changes in lake ecosystems, including an increased input of pollutants. Among the most important and still widely studied pollutants are heavy metals (HMs), whose concentrations and potential toxicity were investigated in the waters and bottom sediments of two lakes of different origin near Gorzów Wielkopolski: the natural Kłodawskie Lake and the gravel pit lake Karnin Reservoir. HM concentrations were determined using inductively coupled plasma triple quadrupole mass spectrometry (ICP-QQQ-MS). The results obtained for HMs in water were analyzed in terms of potential toxic effects on humans, whereas HMs in bottom sediments were assessed in terms of their potential toxicity to aquatic biota. The results indicate comparable HM concentrations in the waters of both lakes and show no potential non-carcinogenic and carcinogenic health risk for humans, both in terms of chronic dermal exposure and quantitative assessment. In contrast, HM concentrations in bottom sediments differed significantly between the lakes, with notably higher values recorded in Kłodawskie Lake. The assessment of individual HMs using the modified hazard quotient (mHQ) indicated very low toxicity for Pb and Zn, and to a lesser extent for Cd, Cu, and Ni. Integrated indices indicated no potential combined toxicity of HMs. The presented study provides a basis for conducting similar analyses in lakes used for recreational purposes and highlights the potential of gravel pit lakes for tourism, particularly in regions characterized by a low number of natural lakes.

A high contamination level by microorganic pollutants (contaminants of emerging concern-CECs and pesticides) was docu-mented at the Oborniki River bank filtration site (Poland) recharged by surface water from the Wetna River. The highest con-centration of CECs and pesticides was found in surface water samples. The documented contamination level of Wetna River water (the river draining a small lowland catchment) is higher than that documented in bigger rivers like the Warta, Izera and Elbe. High contamination levels were documented also in wells that are recharged by waterfrom the Wetna Rivervia bank fil-tration. The removal rate observed in wells (compared with source river water) was estimated as 57% for CECs and 74% for pesticides while the removal rate calculated for carbamazepine (a conservative pharmaceutical substance) was 26%. In one well the nicosulfuron concentration was higher than the upper permissible limit. Among the substances detected were also 2 banned constituents: chlorotoluron and izoproturon.

Urbanization and the increasing share of impervious surfaces promote heavy metal (HM) inputs to small urban rivers, mainly via surface runoff and stormwater drainage systems. The aim of the research was to identify HM (Cd, Cr, Cu, Ni, Pb, Zn) pollution in water and bottom sediments within the Bogdanka River catchment in Poznań. Samples from 28 sites were collected in March and June 2024 and were analysed using inductively coupled plasma triple quadrupole mass spectrometry (ICP-QQQ-MS). Data evaluation included selected pollution and toxicity indices and principal component analysis (PCA). The results revealed contamination of bottom sediments in the lower river course, attributed to stormwater drainage, which represents the main HM source in the catchment. Toxicity indices showed that HMs in water and bottom sediments do not pose significant toxicological risk. Additionally, PCA suggests that organic matter content and sediment pHKCl are important factors influencing HM accumulation in sediments.

Turkusowe Lake is a pit lake formed after the extraction of CaCO3 , located within the Wolin National Park (northwestern Poland). The aim of the study was to assess the potential contamination of water and bottom sediments with trace elements (TE) in relation to previous research, which indicated the impact of anthropogenic pressure. To achieve this, basic physico-chemical parameters of the water (pH, temperature, electrical conductivity, oxygen content) were measured, and the concentrations of TEs (Ag, As, Ba, Be, Cd, Co, Cr, Cu, Mo, Ni, Pb, Sb, Tl, V, Zn) in water and bottom sediments. The potential contamination of water by trace elements was evaluated using the trace metal evaluation index (TMEI), while sediment contamination was assessed usingthe geoaccumulation index (Igeo) and contamination factor (CF). The results of the TMEI and Igeo did not indicate contamination, whereas the CF pointed to low, initial contamination of the bottom sediments by Ni and V. It has been demonstrated that the lower layer of the lake becomes contaminated by TEs more quickly, in contrast to the upper layer, which undergoes faster eutrophication. Turkusowe Lake continues to demonstrate significant resistance to TEs contamination due to its alkaline pH, but regular monitoring is recommended.

This study presents results for trace elements (TEs) and rare earth elements (REEs) in five pit lakes located within the Muskau Arch, one of the largest regions in Central and Eastern Europe affected by acid mine drainage (AMD). Concentrations of TEs (Ag, Al, As, Ba, Be, Bi, Cd, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, Pb, Rb, Sb, Sc, Se, Th, Tl, U, V, Zn) and REEs (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) were determined using inductively coupled plasma triple quadrupole mass spectrometry (ICP-QQQ-MS). The highest concentrations were recorded for Fe (0.14-156.9 mg/L), which was the dominant TE in all pit lakes except MA1, where Al was dominant. PCA indicated that TEs such as Al, Be, Co, Fe, Li, Mn, Ni, Rb, Sc, Th, and Zn were strongly associated with pit lakes affected by AMD. Two subgroups were identified: (1) Be, Co, Ni, and Zn, which correlated with Al and low pH, and (2) Fe, Mn, Li, Rb, and Th, which correlated with slightly higher pH and anoxic and more reducing conditions. The toxicity analysis of TEs revealed substantial variation among the pit lakes (from extreme to low toxicity) and indicated that the most important TEs contributing to water toxicity were Al, Mn, Zn, and Ba. Total REE concentrations ranged from 0.15 mu g/L to 149.3 mu g/L, with by far the highest values recorded in MA2, and their concentrations were strongly influenced by pH. The pit lakes generally exhibited LREE (including La to Eu) enrichment, as well as a weaker MREE (including Sm to Dy) enrichment. Positive Gd anomalies were identified at all sampling points. Additionally, positive Eu anomalies were observed in all pit lakes except MA2, which was the most strongly affected by AMD, and positive Tb anomalies were recorded primarily in samples influenced by AMD.

In the river bank filtration systems (RBF) the extracted water quality is strongly depending on source (river or lake) water quality. It is well known that these systems can effectively remove emerging contaminants (pharmaceuticals, personal care products or pesticides) from polluted river waters. The common river water contamination is related to nitrate which is observed at high concentrations commonly. Moreover, the nitrate concentrations in the rivers are usually very changeable seasonally. The current work presents the effectiveness of the RBF system in nitrate removal from polluted source (river) water. For this purpose, the water chemistry changes during filtration between the river and productive wells were used, while for identification of denitrification processes the isotopes of d18O and d15N dissolved in nitrate were used. The RBF site located in Śrem (Wielkopolska region, Poland) was selected for the presented research. The water samples were taken from the river and six continuously pumped wells. The water sample representing ambient groundwater was analysed as well. The wells at a close distance from the river (40-50 m) and the wells located at a greater distance from the river (70 – 95 m) were chosen for investigation. The visible differentiation of nitrate concentration was observed. The highest nitrate concentrations were observed in the river and wells located at a close distance from the river (~5 mg/l) and then the nitrate concentrations decrease (to a level of

Some of deposits parameters, such as lower grade or peculiar composition (i.e. refractory phases, organic compounds) hinder their effective processing for metal recovery. However, bioleaching-based methods could support metal extraction from materials showing either poor metal content or complex mineralogy. In this study, two distinctly different samples of Kupferschiefer shale (LG-with low copper content, HG-organic-rich with high copper content) were examined in terms of metal bioleaching using two bacteria: Acidithiobacillus thiooxidans and Pseudomonas fluorescens. For LG sample, activity of P. fluorescens supports high extraction of Cu and Mo, while A. thiooxidans supports As extraction. For HG sample, activity of A. thiooxidans and P. fluorescens resulted in poor copper recovery of 1.8% and 7.26%, respectively. Alteration on shale surfaces were specific to the applied microorganism, revealing different features of post-leaching sulfides.

One of the most critical issues in soil science is the content of metals and their environmental toxicity. This is especially relevant to soil contamination by metals in industrial and postindustrial areas. The region of Lower Silesia, known for exploitation of Cu and Ag deposits, along with Zn and Pb, is significantly affected by metal contamination near post-flotation waste facilities in both old and new copper districts. Metal concentrations in soils adjacent to abandoned tailings storage facilities in the copper district were measured to identify factors influencing contamination in agricultural and technogenic soils. Concentrations of copper, lead, and zinc were determined in 111 samples taken from nine soil profiles down to a depth of 1.60 m. Significant variation was observed in metal content: in agricultural soils, copper reached up to 2800 mg/kg, lead up to 150 mg/kg, and zinc up to 65 mg/kg. In forest soils, concentrations reached as high as 1700 mg/kg for copper, 1800 mg/kg for lead, and up to 1100 mg/kg for zinc. The metal content increased with proximity to the tailings storage. Soil profiles closest to the emission source showed the highest metal concentrations, while concentrations of Cu, Pb, and Zn decreased with distance.

Lake pollution has attracted concerns worldwide; especially the excessive accumulation of trace elements (TEs) and rare earth elements (REEs) in bottom sediments can pose a serious threat to ecosystem health. However, there is still a knowledge gap on the level of sediment pollution in lakes isolated from the direct impact of pollution sources, their spatial variability, and also on the factors influencing this state. The aim of this study is to investigate the level and spatial variability of TEs and REEs concentrations, as well as to determine their source and the factors determining their distribution in the bottom sediments of Lake Ostrowite. Lake Ostrowite is the largest and deepest water body located in the Bory Tuholskie National Park (in northern Poland), which completely isolates the lake from the direct impact of pollution sources. The study covered analyses of 32 surface samples of bottom sediments. The concentrations of 24 TEs and 14 REEs were determined using inductively coupled plasma mass spectrometry (ICP-QQQ-MS). The assessment of the enrichment of bottom sediments in TEs and REEs employed geochemical background values (GBV) that provided the basis for the calculation of relative concentrations and geochemical indices. The determination of their sources and supply routes was based on the cluster analysis and principal component analysis. The obtained results point to the enrichment of the bottom sediments with TEs and REEs. Relative concentration values of TEs and REEs in reference to geochemical background values were in ranges from 0.01 to 7.31, at an average of 0.99, and from 0.03 to 4.29, averaging 1.76, respectively. The enrichment factor values show moderately severe enrichment of sediments at the study sites. This was primarily determined by the concentrations of Ag (from the TEs group) and Lu (from the REEs group). The metal pollution index values showed an approximate spatial distribution of points in terms of the presence of TEs and REEs. The lowest concentrations of TEs and REEs occurred on the eastern shore of the western basin of Lake Ostrowite. TEs and REEs concentrations in sediments are positively correlated with the content of organic matter and depth and negatively correlated with distance of the sampling point from the river outflow from Lake Ostrowite. On the eastern shore of the western basin, TEs and REEs concentrations are additionally shaped by wind, predominantly from the western direction. With water wave action, organic matter is transported to the central part of the western basin, where it is accumulated. Since the lake is isolated from point and nonpoint pollution sources, relevant from a biogeochemical point of view are dry and wet depositions from the atmosphere as well as aquatic vegetation, shoreline vegetation, forest litter, soil, and groundwater.

Soil constitutes a direct sink for elements mobilized due to mining and smelting activities. One of the desired pathways for reducing the bioavailability and toxicity of the contaminants is their transformation into sparingly soluble solid phases. Here, we report the formation of secondary mineral phases in extremely contaminated (up to 210 g Zn kg-1,102 g Pb kg-1, 5.7 g Cd kg-1, and 6.4 g As kg-1, respectively) organic-rich soil. Combining mineralogical techniques (SEM, XRD), a nonspecific sequential extraction (CISED) with Mo center dot ssbauer and X-ray photoelectron (XPS) spectroscopies evidenced two poorly crystalline goethite components differing in crystallite size and As, Zn, Pb, Ca, Al, P substitutions and minor magnetite associated with plant roots (mainly Deschampsia caespitosa, Equisetum palustre, and Carex rostrate) directly below a layer of smelter-derived particles deposited into the soil. SEM was the only method that unambiguously documented the occurrence of ZnCd sulfide microsize aggregates incrusting plant roots and located in between the (hydrous) Fe oxides. Sequential extraction confirmed a complete As immobilization by goethite, while Cd forms a solid solution with ZnS and is lacking in the Fe hydroxides. The partitioning of Zn and Pb between the goethite and sulfide phases depends on soil water saturation. It is proposed that the coexistence of hydrous Fe oxides and nonferrous metal sulfides in the soil subsurface is possible because of redox heterogeneity of the rhizosphere and the decoupling of sulfur and iron cycles. Low mobility of biogenic sulfide ions and the protecting role of organic matter limits goethite sulfidation. The system remains active, adapting to the seasonally changeable plant roots ecology and fluctuations in water saturation. The obtained results are of value in remediation and managing strategies for contaminated soils and in reconstructing processes related to the formation and/or transformation of low-temperature sulfide deposits.

Flotation tailings originating from copper ore processing were evaluated in terms of chemical and mineralogical features, leaching, and resource potential. The results demonstrated that flotation tailings show varying degrees of the leachability of elements when exposed to different pH conditions (2-13); the Zn, Cu and Co leachabilities decrease as pH increases, whereas Mo, Ag and Sb revealed U-shaped leaching trend as a function of pH. Flotation tailings were found to be fairly reactive when exposed to water leaching and rainfall conditions. The environmental risk analysis demonstrated Zn to be the most susceptible element to liberation from the flotation tailings studied. Recovery tests demonstrated sulfuric acid to be slightly more efficient extracting agent as compared to citric acid. Hybrid approach to metal recovery was rather unsuitable for studied tailings due to lower extraction yield (not exceeding 20%) as compared to chemical treatment (not exceeding 40%).

Protection and restoration of the CaCO3 depositing alkaline fens require an in-depth understanding of these unique and declining ecosystems. The present study investigates the development of the formerly heavy tufa depositing alkaline fen in East-Central Europe after CaCO3 precipitation markedly declined ca. 5400 cal yr BP. By combining palaeoecological and monitoring data, we aim to identify the limiting factors for tufa deposition and to recognise the vegetation and mollusc response to the change. Investigation of the current fen ecosystem included a botanical and malacological inventory and a monthly monitoring of the physicochemical properties of the groundwater emerging at the fen. It was also tested whether CaCO3 precipitates there. Transformations of the fen ecosystem since the mid-Holocene tufa decline were recognized by applying plant macrofossil and malacological analyses supplemented with organic matter and CaCO3 contents and the radiocarbon chronologies of the sediment cores. Although macroscopic tufa is currently not observed at the fen surface, the monitoring study revealed the microscopic calcite crystals at the glass slides during the spring and summer. A combination of cooling, gradual depletion of the Ca2+ pool, acidification of soils, and water table fluctuations was likely responsible for limiting tufa deposition in the mid-Holocene and maintaining this state during the late Holocene. Share of the calciphilous species' macrofossils (e.g. moss Tomentypnum nitens) declined following the sedimentary CaCO3 drop, whereas the contribution of species associated with high nutrient levels raised (e.g. Juncus articulatus). Inspection of the contemporary vegetation of the fen revealed that only Carex paniculata is associated with the calcium-rich substrate. The response of molluscs to the decline in tufa deposition remains unclear as mollusc shells did not preserve in CaCO3-depleted sediments, except for the youngest deposits. The present-day malacofauna consists of 21 species, including two rare and protected calciphilous species, namely Vertigo angustior and V. geyeri.

Calamine susceptibility to dissolution requires a detailed experimental evaluation to uncover an alternative management option for these materials. This study aimed to investigate the (bio)leaching behaviours of Zn/Pb-bearing calamines to quantify their potential as a Zn resource. Chemical treatments, including the application of mineral (H2SO4, HCl and HNO3) and organic acids (citric and oxalic acids), along with biotic treatments involving the bacteria Acidithiobacillus thiooxidans and Pseudomonas fluorescens, were used to analyse the mobilisation mechanisms, namely acidification and complexation. The results showed that HCl and HNO3 were the most efficient chemical agents, with an extraction efficiency as high as 39 % (Zn). A. thiooxidans extracted the largest amount of Zn (40 %), which proves that the efficiency of the biotic process can be nearly the same as that of the chemical process. However, the main mechanism governing element mobility was the pH factor. This study shows the potential of calamines as prospective materials for the recovery of Zn and other elements (Ge, Tl), even in those treatment conditions that require further optimisation.

The paper presents the results of physicochemical analyses of spring waters in the Postomia River valley (Northwest Poland). Multivariate statistical methods, i.e., cluster analysis (CA) and principal component analysis (PCA) were used to assess the spatial distribution of similarities and differences in the concentrations of individual elements. Concentrations of macro elements (MEs), trace elements (TEs) and rare-earth elements (REEs) were analysed concerning the spring’s typology, land use structure and the distance from roads. The results showed that the springs waters are of the Ca2+-HCO3− and Ca2+-HCO3−-SO42− types, medium hardness and low mineralisation. The study revealed differences between valley springs and scarp-foot springs in terms of electrical conductivity and concentrations of F−, SO42−, NO3−, Mg2+, Ba, Zn, and U. Greater variability was observed between the physical and chemical conditions of the spring waters due to their location in terms of land use. Springs located in agricultural areas had lower pH values than those in other areas, and higher NO3− concentrations. The pH values and concentrations of Fe, Mo, Rb, and Th in urban areas were higher than in agricultural areas. Moreover, the concentrations of F−, Cl−, K+, Na+, Mo, Sb, Se, and Sr were higher in urban areas than in forested areas. The study shows that only HCO3− values and SO42− concentrations were related to the distance from the road network. The concentrations of Cl−, SO42−, and K+ were higher in the waters of springs located more than 50 m from the road network. The Ca and PCA analysis did not permit the identification of a single dominant origin of pollutants, suggesting an interaction of different types of pollution sources.

The recharge zone of an aquifer supplying the Tursko well-field (Poland), located in an area of sparse water resources, shows groundwater contamination manifested by high nitrate concentrations and pharmaceutical compounds. This study documents the steady deterioration of groundwater chemistry during one decade of groundwater exploitation, and analyses wastewater impact on the groundwater chemistry using pharmaceutical compounds as anthropogenic tracers, with focus on the influence of treated wastewater and drainage water. These waters infiltrate into groundwater from a drainage ditch located in the water supply aquifer’s recharge zone. It is shown that strongly contaminated water can deliver organic matter and nutrients to the groundwater, activating or intensiying denitrification. As a result, the nitrate concentration has decreased in the groundwater, while concentrations of denitrification products have increased. Associated process of oxidation of organic matter causes periodic exceeding of limits allowed for drinking water. The ability of pharmaceutical compounds to act as anthropogenic tracers shows that infiltration of wastewater is a significant factor influencing drinking groundwater quality

Strontium isotopes have seen common use as a tracer of volcanic-influenced fluids at hydrothermal vents and cold seeps hosted by sedimented rifts. However, for some fluid emissions, no apparent contribution of volcanogenic Sr has been observed, despite geological or seismic evidence suggesting magmatic involvement in the fluid expulsion. Here, we explore the behaviour of Sr during fluid-rock interactions in a sedimented rift based on the isotope and elemental composition of Albian hydrocarbon-seep carbonates of the Basque-Cantabrian Basin, Pyrenees. The basin represents a peri-cratonic rift formed during the opening of the Bay of Biscay and infilled with organic-rich siliciclastics affected by subvolcanic intrusions. The intrusions stimulated thermogenic hydrocarbon generation in the sediments and resulted in enrichment of the associated seep carbonates in volcanic-derived, radiogenic Nd. In contrast, none of the 87Sr/86Srcarbonate ratios observed in this study provide evidence for subseafloor interactions between the seeping fluids and igneous materials. Instead, all four studied seep deposits show various degrees of 87Sr-enrichment, bearing the fingerprint of interactions with the rift-filling siliciclastics, rather than a volcanogenic signature. Furthermore, for three deposits, the observed unusual, positive correlation between the Sr and Nd isotope ratios attests to a presence of an evolved, deep-seated fluid end-member enriched in both 87Sr and 143Nd. This isotope decoupling can be explained by the different responses of Nd and Sr to subseafloor fluid-volcanic interactions, with a moderate degree of elemental exchange able to modify the fluid Nd isotope signal, but insufficient to affect the fluid Sr isotope signature. The study shows that for many sedimented seeps and vents, and especially for low-temperature, hydrocarbon-dominated emissions, volcanic-influenced fluids can be more reliably traced using the Nd isotope system, whereas Sr isotopes cannot provide standalone evidence for their absence.