Geochemical Baseline Research Articles

Quantification of heavy metal contamination and source in urban water sediments using a statistically determined geochemical baseline

Geochemical baselines (GBs) play a crucial role in discerning natural variability from anthropogenic impacts on elemental composition within the environment. However, their applicability in quantifying the contribution of pollution sources to heavy metal contamination in sediments remains understudied. This research aimed to assess the degree of contamination and local pollution source attribution by leveraging geochemical baselines derived from statistical techniques, specifically the relative cumulative frequency (RCF) and 2σ-iterative (2σ-I) methods. In the urban water systems of Ma’anshan City, the major iron ore centre in eastern China, we observed concentration ranges of Cr, Cu, Ni, Pb and Zn in 36 sediment samples ranging from 66.89 to 352.08 mg/kg, 22.01 to 133.37 mg/kg, 22.66 to 50.80 mg/kg, 14.66to 264.37 mg/kg and 73.30 to 2707.46 mg/kg, respectively. RCF and 2σ-I techniques yielded similar GBs with no significant differences (p > 0.05). The geo-accumulation index and contamination factor analysis showed a sediment heavy metal accumulation rank of Zn > Pb > Cr > Cu > Ni. The contribution percentage of pollution sources varied with land functional type of watershed. For industry-influenced sediments, the contribution of local sources to Cr, Cu, Pb and Zn was significant, with shares of 43%–88%. Overall, this study highlights the valuable insights provided by GBs for effective management of urban aquatic environments.

Geochemical baseline establishment and accumulation characteristics of soil heavy metals in Sabaochaqu watershed at the source of Yangtze River, Qinghai-Tibet Plateau

The establishment of soil geochemical baseline and heavy metal pollution assessment in the Qinghai-Tibet Plateau is of great significance for guiding environmental management in the high-cold and high-altitude regions. A total of 126 topsoil samples (0–20 cm) were collected and the contents of Cu, Pb, Zn, Ni, Cr, Cd, As and Hg were determined in the Sabaochaqu basin of the Tuotuo River, the source of the Yangtze River, in the Tibetan Plateau. The baseline values of 8 heavy metals were determined by mathematical statistics, iterative 2times standard deviation method, cumulative frequency and reference element standardization, and the soil heavy metal pollution in the study area was assessed by enrichment factor method and pollution index method. The results showed that the average contents of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn were 31.84, 0.29, 66.07, 17.35, 0.021, 27.86, 49.35 and 88.56 mg/kg, respectively. Baseline values were 22.24, 0.217, 64.16, 15.69, 0.0191, 26.46, 34.91, and 68.62 mg/kg, respectively. There is a great difference between the baseline value of soil heavy metals in study area and the Xizang soil background value, especially the baseline value of Cd was 2.68 times of its background value. The results of the pollution evaluation based on the baseline values showed that the 8 heavy metals were slightly enriched, and the overall pollution status was light pollution, and measures should be taken to control and manage them. The research results can provide a reference value for the evaluation of soil heavy metal pollution in the source region of the Yangtze River, and also provide a theoretical basis for the construction of soil heavy metal baseline values in similar high-cold and high-altitude regions.

Impact of Environmental Conditions on Soil Geochemistry in Southern Kazakhstan

This study investigated the elemental composition of soils in Kyzylorda and Turkestan (southern Kazakhstan), an area rich in natural resources but facing potential environmental threats from industry and agriculture. The goal was to establish baseline geochemical values and assess soil contamination risks. Soil samples were collected from across the region and analyzed using ICP-MS and INAA techniques, providing a comprehensive profile of 72 elements. Statistical analysis revealed significant variations in elemental concentrations, with enrichments observed for specific elements when compared with reference values. Notably, both regions shared a core set of elements including rare earth elements (yttrium series: holmium, erbium, thulium), noble metals (gold, platinum, ruthenium, palladium), and tungsten. Enrichment patterns, however, provided distinct insights. Rare earth element enrichments likely reflect the region’s geology, while elevated radioactive elements necessitate further investigation to understand potential environmental and health risks. Enrichment of iron group elements might be linked to a combination of geological factors and anthropogenic activities like mining or industrial processes. A significantly higher number of elements exceeded background levels in Kyzylorda compared with Turkestan, suggesting greater element accumulation in Kyzylorda’s soil. This difference could be attributed to variations in regional geology or historical anthropogenic activities. The established geochemical baseline for 72 elements and the identified areas of potential contamination will inform land management practices, guide future environmental monitoring efforts, and ultimately contribute to the safeguarding of public health in southern Kazakhstan.

Spatial–Temporal Variations in Soil Organic Carbon and Driving Factors in Guangdong, China (2009–2023)

Spatial–temporal variation in soil organic carbon is an important factor for national targets to mitigate climate change and land degradation impacts. In this research, we took Guangdong Province of China as the study area, evaluated the spatial–temporal distributions of soil organic carbon using data from three China Geochemical Baseline projects (conducted in 2009, 2016, and 2023, respectively), and quantified the main driving factors of spatial–temporal variations in soil organic carbon using the random forest algorithm, further predicting the density and inventories of soil organic carbon. The results demonstrate that the mean value of SOC in Guangdong in 2009 was 0.81%; in 2016 it was 1.13%; and in 2023 it was 1.02%. The inventories of soil organic carbon (0–30 cm) in Guangdong Province were 0.61 Pg in 2009, 0.74 Pg in 2016, and 0.62 Pg in 2023. Soil in Guangdong acted as a carbon sink from 2009 to 2023 as a whole, and the most important driving force behind spatial–temporal variations in soil organic carbon was temperature, followed by precipitation and vegetation cover.

Mapping geochemical domains using stream sediment geochemistry: An approach based on compositional indicators in the Volturno River basin (South Italy)

When dealing with environmental problems, it is of fundamental importance to establish reference values (geochemical baselines) against which to determine the presence or absence of active contamination processes.In the effort to develop a method to assess the geochemical baselines for territories featuring complex geological settings and a well-established anthropic environmental pressure, we combined compositional data analysis (CoDA) with geolithological information to reduce the degree of uncertainty possibly affecting the results. The proposed approach comprises (1) a knowledge-driven step to select a number of sample subsets from a geochemical dataset each with a high probability of having its composition strongly influenced by only one of the lithologies outcropping in the study area; (2) a data-driven step to compute compositional principal balances and define geochemical indicators to be used to assign each of the observations in the dataset to one of the geochemical domains associated to a mayor lithologies outcropping in the study area; (3) the determination for each geochemical domain of baseline values based on the samples assigned to them by the data-driven step.The method was tested using the geochemical data referring to 887 stream sediment samples collected across the Volturno River catchment basin (Southern Italy), featuring a relevant lithological heterogeneity.The results obtained were easily interpretable as they fitted well with the geomorphological, geochemical, and geodynamic processes characterizing the study area.Despite the use of stream sediments for the specific case study presented, the application principles of the method hold for any environmental media and for any territory for which there is a need to define baseline values. However, for a successful application of the method, it is crucial to have a fair knowledge of the geological settings of the study area.

Differentiating anthropogenic effects from natural metal(loid) levels in residential soil near a zinc smelter in South Korea.

Metal(loid)s pose a significant hazard due to inherent toxicity. Individuals are particularly exposed to metal(loid)s in soil through direct or indirect contact. Identifying metal(loid) sources in soil is required for exposure mitigation to anthropogenic metal(loid)s, while metal(loid)s are natural constitutes of soil. Metal(loid) concentrations and Pb isotopes were determined in residential soil profiles impacted by a Zn smelter to distinguish the anthropogenic effect from natural levels. One hundred sixty-nine core soil samples were collected from depths down to 5.5m below ground level at 19 sites and were divided into Zn-Cd-As- and As-contaminated groups based on the worrisome level (WL) of soil contamination. The Zn-Cd-As-contaminated group (n = 62) was observed at depths < 1m, showed high Zn levels (mean of 1168mg/kg) and Cd and As frequently exceeding WLs, and had low 206Pb/207Pb ratios close to the Zn smelter. In contrast, the As-contaminated group (n = 96) was observed at depths > 1m, did not have other metals exceeding WLs, and showed a wide range of 206Pb/207Pb ratios far away from the Zn smelter. The results indicated that the pollution sources of Zn-Cd-As- and As-contaminated soils were fugitive dust emissions from smelter stacks and geology, respectively. The metal(loid)s in host rock set geochemical baselines in soil profiles, while smelting activities affected the upper layers over 50years. This study demonstrated the effectiveness of utilizing the vertical distribution of metal(loid) concentrations and Pb isotopes in soil profiles for distinguishing between anthropogenic and geogenic origins, in combination with baseline assessment.

Historical construction, quantitative source identification and risk assessment of heavy metals contamination in sediments from the Pearl River Estuary, South China

Historical reconstruction of heavy metals (HMs) contamination in sediments is a key for understanding the effects of anthropogenic stresses on water bodies and predicting the variation trends of environmental state. In this work, eighteen sediment cores from the Pearl River Estuary (PRE) were collected to determine concentrations and geochemical fractions of HMs. Then, their potential sources and the relative contributions during different time periods were quantitatively identified by integrating lead-210 (210Pb) radioisotope dating technique into positive matrix factorisation (PMF) method. Pollution levels and potential ecological risks (PERs) caused by HMs were accurately assessed by enrichment factors (EF) based on establishment of their geochemical baselines (GCBs) and multiparameter evaluation index (MPE). HMs concentrations generally showed a particle size- and organic matter-dependent distribution pattern. During the period of 1958–1978, HMs concentrations remained at low levels with agricultural activities and natural processes being identified as the predominant sources and averagely contributing >60%. Since the reform and opening-up in 1978, industrial and traffic factors become the primary anthropogenic sources of HMs (such as Cu, Zn, Cd, Pb, Cr, and Ni), averagely increasing from 22.1% to 28.1% and from 11.6% to 23.4%, respectively. Conversely, the contributions of agricultural and natural factors decreased from 37.0% to 28.5% and from 29.3% to 20.0%, respectively. Subsequently, implementation of environmental preservation policies was mainly responsible for the declining trend of HMs after 2010. Little enrichment of sediment Cu, Zn, Pb, Cr and Ni with EFs (0.15–1.43) was found in the PRE, whereas EFs of Cd (1.16–2.70) demonstrated a slight to moderate enrichment. MPE indices of Cu (50.7–252), Pb (52.0–147), Zn (35.5–130), Ni (19.6–71.5), Cr (14.2–68.8) and Cd (0–9.90) highlighted their potential ecological hazards due to their non-residual fractions and anthropogenic sources.

Contrasting platinum trajectories in three major French rivers using dated sediment cores (1910–2021): From geochemical baseline to emerging source signals

Platinum (Pt) is a Technology Critical Element (TCE) which, since the 1990s, has been mainly used in the industry in catalytic converters for automobile emission control. Previous studies have shown Pt contamination of road-side sediments and surface sediments in urban rivers and lakes but few of them have addressed temporal variations. The present work presents historical Pt concentration trends in 137Cs-dated sediment cores from floodplains or secondary channels at the outlets of three major French watersheds (Loire, Rhone, and Seine Rivers) covering the past ∼110 years, i.e., from the 1910s to 2021. Platinum baseline levels in the sediment were estimated for the Loire River (0.76 ± 0.22 μg kg−1 for the period ∼1910-∼1955) and the Rhone River (1.64 ± 0.41 μg kg−1), and historical Pt variations seem to reflect variations in hydrodynamics and grain size composition. Since the early 2000s, Pt concentrations in the Loire and the Rhone River sediments tend to increase (>2.5 μg kg−1) and were attributed to the use of car catalytic converters, an emerging technology since the 1990s using >50 % of European Pt demand. High and variable historical Pt concentrations (up to 14.6 μg kg−1) in the Seine River sediments may reflect legacy Pt sources due to former anthropogenic activities in this watershed, such as the use of Pt-based catalysts for petroleum refinery since the end of the 1940s, coal handling and precious metals refining, probably concealing the likely presence of an emerging traffic-related Pt signal. This first comparison of historical Pt concentration trends in sediments from contrasting watersheds allows to distinguish signals originating from different natural and anthropogenic sources (background level, historical sources, road traffic).

Continental-scale distribution of tungsten in catchment sediments throughout China: Prospecting implications from the China Geochemical Baselines project

Tungsten (W), known as the “teeth of industry”, is a critical mineral resource for emerging industries worldwide. Given the crucial role of tungsten in various industrial and military applications, its potential as a mineral resource for China must be assessed. Determining the concentration and distribution of tungsten in catchment sediment environments is key to such assessments. Therefore, based on the China Geochemical Baselines (CGB) project, we obtained information on the continental-scale concentrations, variations, and distributions of tungsten throughout mainland China. The tungsten concentrations in the top and deep sediment samples varied from 0.20 to 294 ppm, with a median value of 1.56 ppm, and 0.25 to 216 ppm, with a median value of 1.51 ppm, respectively. The tungsten concentrations varied widely across regions, with the distribution at the catchment scale predominantly controlled by the parent rock, especially granites and alkaline rocks, and the distribution at the continental scale primarily controlled by mineralization. Generally, the spatial distribution of tungsten in the top and deep catchment sediments was relatively consistent, with higher concentrations in South China and lower concentrations in Northwest China. Furthermore, nine large to super-large tungsten prospecting belts were delineated. Numerous well-known tungsten deposits have been located, especially in the South China anomalous belt (with an area of approximately 1.03 million km2), which exhibits an anomalous distribution trend of prospecting tungsten deposits from the south to north, and the east to west. Moreover, the Xizang (Tibet)-Sanjiang anomaly belt (approximately 585,000 km2) represents an important future exploration target for tungsten deposits.

Geochemical baseline establishment, pollution level and health risk assessment of soil heavy metals in the upper Xiaowen River Basin, Shandong Province, China.

This study analyzed the distribution and content of eight heavy metals (Cu, Pb, Zn, Ni, Cr, As, Cd, and Hg) in 221 surface soil samples from the upper reaches of the Xiaowen River. Environmental geochemical baselines were established for the eight heavy metals, and the pollution status was assessed on the basis of these baselines and the soil background value of Weifang City. The calculation results of Nemerow pollution index and the potential ecological hazard index (PEHI)-Ri showed that the overall pollution degree and ecological hazard in the study area were at a slight level. 49% (calculated by baseline value) and 24% (calculated by background value of Weifang City) samples were at moderate or above pollution level. 9% (calculated by baseline value) and 42% (calculated by background value) samples were at the level of moderate potential ecological hazards or above. According to the calculation results of Igeo and PEHI-Ei, the main pollutant in the study area was Hg, followed by Cd. 3% (calculated by baseline value) and 12% (calculated by background value) of Hg samples were at moderate or above contamination levels. 5% (calculated by baseline value) and 38% (calculated by background value) of Hg samples were at the level of strong potential ecological hazard or above. The western, central, and eastern parts of the study area were mainly the primary areas of pollution and ecological hazards. The non-carcinogenic risk was at an acceptable level, the carcinogenic risk was at a tolerable level, and the main risk pathway was oral intake, with Cr being the main contributor. Source apportionment indicated that soil heavy metals primarily originate from soil parent material, transportation, agricultural fertilization, and industrial emissions (waste gas, waste water and solid waste).

Geochemical base for As, Co, Cu, Ni, P, Pb, S, V and Zn in road dust collected in areas of oil industry activity in the Metropolitan Region of Salvador, Bahia, Brazil

Road dust collection was carried out in Salvador and some municipalities in the Metropolitan Region of Salvador (MRS), such as Simões Filho, Candeias, Madre de Deus and São Francisco do Conde, situated within an area of oil activity. In the chemical-physical characterisation of the road dust collected, the average fractions of coarse sand (17.44 %), medium (27.15 %), fine (32.63 %) and very fine (15.54 %) were found in the 17 samples collected. The samples underwent an acid extraction procedure in a closed digester block, with the mixture HCl + HNO3 + H2O2. The extract was analysed and concentrations of Al, As, Co, Cu, Fe, Ni, Pb, P, Sb, V and Zn were determined. Linear regression analysis was applied to the concentrations of As, Co, Cu, Ni, Pb, P, V and Zn, generating the equations of the straight lines, which served as a geochemical baseline for the region of road dust samples. For the enrichment factor (EF), most chemical elements showed values lower than < 1 at the collection points, except for Cu, Mn, and P (10 < EF < 25) and for Co, Cu, P and Ni (5 < EF < 10), in the regions of Candeias and Simões Filho. On the other hand, the geoaccumulation index (Igeo) of most points were evaluated as uncontaminated (class 0) and moderate or uncontaminated (class 1) for Igeo, except for P (class 4) and Mn (class 5). Principal component analysis (PCA) showed accumulated total variance corresponding to 76.45 %. For the hierarchical cluster analysis (HCA), the results agree with those found in the PCA. Points P3 (Candeias) and P16 (Simões Filho) were the points that showed less dissimilarity with the other points analysed, indicating possible enrichment of the chemical elements found at these points, confirmed by the EF values.

Evaluation of succulent plants Echeveria elegans as a biomonitor of heavy metals and radionuclides

This work evaluates the use of Echeveria elegans as a biomonitor of metals and radionuclides, using semi-urban soils as a study area. The study area is exposed to various trace elements of concern for various social groups in nearby localities. The quantification of metals and radionuclides was performed by X-ray fluorescence spectrometry and gamma spectrometry, respectively. Cumulative frequency distribution curves, descriptive statistics, and multivariate analysis were used to estimate the local geochemical baseline and identify geochemical and anthropogenic patterns of metals and radionuclides from topsoil and E. elegans. The evaluation of contaminants and the contribution of possible exposure routes (topsoil and atmospheric deposition) was performed with the enrichment factor (EF) and the relative concentration factor (CFR). The results suggest that the plant does not present significant physical stress due to the environmental conditions to which it was exposed. Likewise, it can bioaccumulate heavy metals from natural and anthropogenic sources. The quantification of radionuclides in the plant is below the detection limits, indicating a low bioavailability and transfer factor. The CFR and EF results showed that the plant accumulates metals from the topsoil and atmospheric deposition. The bioaccumulation mechanism would be related to the functioning of Crassulaceae Acid Metabolism (CAM). In topsoil, the organic acids of the plant would modify the solubility of the metals present in an insoluble form in the soil, acting as ligands and, subsequently, following the transport route of these metabolites. In atmospheric deposition, the metals deposited in the leaves would be incorporated into the plant through the opening of the stomata because of the capture of CO2 (at night, day, or during environmental stress) by the CAM. Overall, the evidence showed that the succulent can be used as a biomonitor of heavy metals. However, additional studies are required to determine its usefulness as a radionuclide biomonitor.

Multi-tracer approach to constrain groundwater flow and geochemical baseline assessments for CO2 sequestration in deep sedimentary basins

Geological storage of gases will be necessary in the push to net zero and the energy transition to reduce carbon emissions to atmosphere. These include CO2 geological storage in suitable sandstone reservoirs. Understanding groundwater flow, connectivity and hydrogeochemical processes in aquifer and storage systems is vital to prevent risk and protect important water resources, such as the Great Artesian Basin. Here, we provide a ‘tool-box’ of geochemical assessment methods to provide information on flow patterns through the basin's aquifers (changes in chemistry along flow path), stagnant versus flowing conditions (cosmogenic isotopes and noble gases), inter-aquifer connectivity and seal properties (major ions, Sr and stable isotopes), water quality (major ions and metals) and general assessments on residence times of groundwater (cosmogenic isotopes and noble gases). This information can be used with reservoir and groundwater models to inform on possible changes in the above-mentioned processes and serve as input parameters for CO2 injection impact modelling. We demonstrate the use and interpretation on an example of a potential CO2 storage geological sequestration site in the Surat Basin, part of the Great Artesian Basin, and the aquifers that overly the reservoir. The stable water isotopes are depleted compared to average rainfall and most likely indicate greater contributions from monsoonal rain events from the northern monsoonal troughs, where amount and rainout effects lead to the depletion rather than colder recharge climates. This is supported by the modern recharge temperatures from noble gases. Inter-aquifer mixing between the Precipice Sandstone reservoir and the Hutton Sandstone aquifer seems unlikely as the Sr isotope ratios are distinctly different suggesting that the Evergreen Formation is a seal in the locations sampled. Mixing, however, occurs on the edges of the basin, especially in the south-east and east where the Surat Basin transitions into the Clarence-Moreton Basin. Groundwater flow appears to be to the south in the Precipice Sandstone, with a component of flow east to the Clarence-Morton Basin. The cosmogenic isotopes and noble gases strongly indicate very long residence times of groundwater in the central south Precipice Sandstone around a proposed storage site. 14C values below analytical uncertainty, R36Cl ratios at secular equilibrium as well as high He concentrations and high 40Ar/36Ar ratios support the argument that groundwater flow in this area is extremely slow or groundwater is stagnant. The results of this study reflect the geological and hydrogeological complexities of sedimentary basins and that baseline studies, such as this one, are paramount for management strategies.

Geochemical exploration and baseline from marine sediments in the fjords, channels and straits of Magellan, Chilean Patagonia

AbstractChilean Patagonia has a complex geological history dominated recently by Quaternary glaciers and rivers that have carried sediments from the mountains to depositional environments within marine fjords and channels. Although much is known about onshore placer deposits, little is known about these deposits and depositional systems in the offshore realm. This study analyzes the chemistry and mineralogy of marine sediments collected in the Strait of Magellan and around the region. This study aims to comprehend the distribution, concentration and provenance of critical/strategic elements and precious metals. In collaboration with the Cabo de Hornos research vessel of the Chilean Navy, 63 sediment samples were collected using a box core sampler, complemented with coastal beach samples. These samples underwent petrographic and geochemical analysis. The predominant opaque minerals identified in these samples are mainly iron oxides (magnetite–hematite‐ilmenite) and sulfides (pyrite, exceptional greigite). A comparison of the average element concentration for all samples for different baseline values revealed the following findings. As, Bi, Li, Re, Sb, Se, Te, and Pd exhibit positive anomalies for the Upper Continental Crust (UCC); Re, Se, and Sr. exhibit positive anomalies for Marine Sediments (MS), and Bi, Cs, Li, Re, Se, Sn, and Te show positive anomalies relative to the Folded Belt (FB). The main contrast anomalies occur in the following locations. Almirantazgo Sound (Sn, Ba, Sb, and Tm); Concepción Channel (Re, Sr., and Te); Smyth Channel (Mn, Re, Sb, Sr., Te, and Se); Almirante Montt Gulf (Mn, Re, and Sb); Nelson Strait (Re, Sr., and Te); Ancho Pass (Ti and Sr); Europa Fjord (Bi and Sn); Del Hambre Pass (Sr); Magdalena Channel and Sound (Sr); Froward Pass (Se), and Whiteside Channel (Mn). Regarding precious metals, silver exhibits contrasting anomalies relative to the UCC in seafloor sediments in the Almirante Montt Gulf (0.161 ppm) and Concepción Channel (0.101 ppm). Palladium contrast anomaly is observed in the Peel Estuary (8 ppb) and Platinum contrast anomalies occur in the Concepción (3 and 5 ppb) and Smyth Channels (4 ppb). Finally, gold, in comparison to the South Patagonian Batholith, reveals contrasting anomalies that occur in the Concepción Channel (8 ppb), Peel Estuary (6.7 and 8 ppb), Nelson Strait (7 ppb), Almirante Montt Gulf (6 ppb), Forward Pass (8 ppb), and Ancho Pass (7 ppb). In summary, the presented results provide valuable insights into the geological and geochemical baseline of the region, offering a better understanding of the relationship with depositional basins and source zones onshore during the late‐Quaternary.

Geochemical baselines of potentially toxic elements in Brunei-Muara soils, Brunei Darussalam: Towards environmental assessment and risk management

We present a comprehensive study on the presence of potentially toxic elements (PTEs) in the topsoil and subsoil of Brunei-Muara District in Brunei Darussalam. Descriptive statistics were employed to analyze the data, and the threshold values for PTEs in both soil layers were determined. Adopting the Tukey's inner fence method, we recommend baselines for PTEs. The study delved into the distribution patterns and potential sources of PTEs in Brunei-Muara, and we identified traffic and agricultural activities as significant contributors to the presence of As, Cr, Cu, and Pb. Industrial and agricultural areas exhibit spatial associations with Mn, Ni and Zn. Cadmium (Cd) was determined to be negligible in Brunei-Muara's soils. Furthermore, geochemical mapping unveiled highly acidic soil conditions in the region, characterized by variations in pH between the topsoil (2.13–8.00) and subsoil (1.89–6.76) layers that generally facilitate mobility of heavy metals. We employed Principal Component Analysis on the log10-transformed data to examine the behavior and mechanisms governing the mobility and retention of PTEs in the soil. This helped us to better characterize the element distribution within the baseline and the recognition of three additional processes enriching the topsoil and subsoil in PTEs. Overall, this study offers valuable insights into the distribution, sources, and behavior of PTEs in the soils of the Brunei-Muara District, which can greatly aid environmental monitoring and management endeavors.

National-scale Geochemical Baseline of 69 elements in Papua New Guinea stream sediments

This study presents the first Papua New Guinea geochemical baseline values of 69 elements. The National-scale Geochemical Baseline project of Papua New Guinea (PNG-NGB) were conducted during 2015–2018, covered an area of approximately 128,000 km2. A total of 1399 stream sediment samples were collected at an average density of 1 sample/100 km2, and 69 elements were analyzed. The results of PNG-NGB values are studied by R-mode factor analysis, and scatter plot analysis, the relationship between the 69 elements and the geological background, mineralization, and human activities are discussed as well. The median values of element contents related to the upper continental crust values were: TFe2O3, TC, Br, Co, Cr, Cu, Hg, Mn, N, Sc, Se, Te, Ti, V and Zn >1.3 times; Na2O, K2O, Ba, Be, Bi, Cl, Cs, F, I, Mo, Rb, S, Sb, Sr, Th, Tl, Zr, La, Ce, Pr and Nd <0.7 times; and SiO2, Al2O3, CaO, MgO, Ag, As, Au, B, Cd, Ga, Ge, Hf, In, Li, Nb, Ni, P, Pb, Sn, Ta, W, U, Y, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, 0.7–1.3 times. R-mode factor analysis based on principal component analysis and varimax rotation showed that they fall into14 factors related to bedrock, mineralization, and human activities. This study provides basic geochemical data for many fields, including geology, mineral exploration, environmental protection, and agricultural production in Papua New Guinea.

Determination of geochemical baselines and evaluation of potentially toxic elements in agricultural soils of Ramhormoz Plain, Iran

ABSTRACT The present study was conducted to investigate the heavy metal pollution status of the agricultural soils in Ramhormoz Plain, Khuzestan province, Iran. A total of 54 samples from the depths (0–20 cm) of the soil were collected from the selected areas in (March) 2021. According to the obtained results, the concentrations of As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Zn, Al in soil samples were 1.3, 0.68, 60, 10.6, 0.01, 218, 23, 3.65, 14 and 0.58 mg/kg, respectively, in which As showed significant soil contamination and Cu, Hg, Mn, Ni, Pb, Zn and Al moderate contamination according to the calculation of contamination factor (CF). PCA analysis revealed that both anthropogenic and natural sources of pollution like agricultural and transport activities contributed to the enrichment of study area. Investigation of ecological risk indicated that Ramhormoz Plain was categorized as a high risk area.

Spatial-temporal variation, source apportionment and risk assessment of lead in surface river sediments over ∼20 years of rapid industrialisation in the Pearl River Basin, China

Lead (Pb) is a highly toxic element and is not essential to the human body. Lead pollution caused by human activities and a high geological background is considered a global environmental issue. According to the China Geochemical Baseline (CGB) project, the Pearl River Basin had the highest Pb content in alluvial sediments of 30 first-level basins in China. For this reason, it is of great significance to determine the temporal and spatial variations in Pb and their influencing factors in the Pearl River Basin. In this study, 956 stream sediment samples collected in the 1980 s (early stage) and 129 river sediment samples collected from 2008 to 2010 (late stage) were used to study the background value and spatial-temporal variation characteristics of Pb in river sediments in the Pearl River Basin. The Pb source apportionment and an ecological risk assessment were also carried out. The background value of Pb (36.2 mg·kg–1) in the river sediments of the Pearl River Basin was significantly higher than that in China (22.1 mg·kg–1). The parent rocks determine the Pb background in sediments and the high Pb background areas mainly comprised carbonate rocks and acid volcanic rocks. Over 20 years of rapid industrialisation, the average Pb increased from 43.3 to 68.3 mg·kg–1 in the Pearl River Basin. The BCR analysis revealed that Pb mainly existed in the reducible phase (48 % on average) and residue phase (42 % on average). The enrichment factor and geo-accumulation index indicated that the late-stage sediments experienced more Pb pollution than the early-stage sediments. However, the risk assessment code (RAC) showed that there was a low ecological risk of Pb in the late-stage sediments. The factor analysis results for the two rounds of data were significantly different. The Pb content in early-stage sediments was closely related to Al2O3 and Zr, while Pb in the late-stage sediments was mainly related to Zn, As, Sb, Au and Hg, indicating that the increase in Pb in the later samples was mainly influenced by human activities. The Pb isotope composition of the late-stage sediments confirmed that low Pb content was mainly controlled by natural sources, while high Pb content was significantly affected by anthropogenic sources. Combining the results of spatial-temporal variation, chemical speciation and source apportionment indicated that the rapid rise of Pb in late-stage sediments in certain areas could be attributed to mining and smelting activities during the process of industrialisation over 20 years. The anthropogenic exogenous Pb could be immobilised by Fe-Mn (hydro)oxides when it entered the soil, so although there was a high background the ecological risk of Pb in river sediments was low. In the future, Pb pollution control and remediation needs to be strengthened in the Pearl River Basin to avoid the outbreak of potential ecological risks linked to Pb.

Spatial distribution of the critical mineral resource element titanium in China and its influencing factors

In China, titanium is found in multi-metal symbiotic ore deposits that present sorting difficulties, low recovery rates, high production costs, and low overall resource utilization rates. The concentration and distribution of titanium in the pedosphere must be better understood to assess the potential titanium resources. The China Geochemical Baseline project obtained harmonized soil and rock geochemical data covering mainland China and provided reliable data for 76 elements (including titanium) from 3382 top (0–25 cm) and 3380 deep (>100 cm) sediment or alluvial soil samples and 12,201 rock samples. In this study, titanium concentrations were determined by X-ray fluorescence spectrometry under strict quality control. The median titanium concentration values in the top and deep samples, which were considered geochemical baseline values, were 3498 mg/kg and 3406 mg/kg, respectively, with mean values of 3661 mg/kg and 3585 mg/kg, respectively. The titanium concentrations ranged from 266 to 24,674 mg/kg and 324 to 25,504 mg/kg in the top and deep soil samples, respectively. The 75 % range (Q25–Q95) of titanium concentrations in the rock ranged from 978 to 8299 mg/kg. The median titanium concentration was 2555 mg/kg in the rock samples, while the mean concentration was 3089 mg/kg. The geochemical map of titanium indicated that low titanium concentrations below Q25 (<3498 and 3406 mg/kg in the top and deep samples, respectively) are primarily distributed in southern Xinjiang, Tibet, Qinghai, Gansu, and Inner Mongolia. The distribution of low titanium content in the soils is likely attributed to these regions being covered by deserts (e.g., Gobi) and glaciers. Soils with high titanium concentrations are widely distributed in the Emeishan large igneous province at the southwest margin of the Yangzi block, which is related to the large distribution of intermediate-basic rock in the area, as well as along the northeast-southwest direction of the Yangtze block, which extends for nearly 1600 km. Moreover, these soils are mainly associated with the black rock system and intermediate-basic dikes. Soil titanium concentrations are affected by various factors, including the occurrence of tectonic activity and distribution of the black rock system, intermediate-basic rock (especially basalt), and VTi magnetite deposits. In particular, the large igneous province area generated by a mantle column represents the main location of VTi magnetite deposit formation and the area with the highest titanium content. In addition to providing detailed information about the titanium distribution in the pedosphere and rock of mainland China, the project can also provide basic geochemical data for the development and utilization of titanium resources and the formulation of critical mineral industry policies.

Hydrochemical Characterization and Quality Assessment of Groundwater in the Southern Plain of Hebei Province, China

The purpose of this research was to understand the hydrogeochemical characteristics and assess the quality of phreatic and confined groundwater in southern Hebei Province. A total of 107 groundwater samples were collected, representing different aquifer conditions over the study area. Multivariate statistical analysis, hydrochemical maps, ionic ratio coefficients, geographic information system (GIS) and geochemical simulation were comprehensively and systematically used to reveal the hydrochemical characteristics of groundwater and its controlling mechanism. The results revealed that both phreatic (pH = 7.02–9.08) and confined groundwater (pH = 7.00–10.60) were slightly alkaline. The hydrochemical types were mainly present as the HCO3-Ca-Mg type in the western premontane area and mixed Ca-Mg-SO4-Cl and Na-Cl-SO4 types in the eastern plains. The hydrochemical composition was dominated by water–rock interactions of natural processes, including silicate weathering, dissolution of sulfate minerals (gypsum, anhydrite), and cation-exchange adsorption. Anthropogenic activities were the main factor causing NO3− content in some groundwater samples to exceed the geochemical baseline. The hydrogeochemistry of groundwater in different aquifers was significantly varied. The average contents of TH, TDS, Na+, Ca2+, Mg2+, Cl− and SO42− in phreatic aquifers were significantly higher than those in confined aquifers. The Entropy Weighted Water Quality Index (EWQI) results revealed that 17.78% of phreatic and 50% of confined water samples were meeting the purpose of drinking water. The groundwater samples with EWQI values exceeding 100 were mainly situated in the Handan urban area and the eastern region of Xingtai City, which should be avoided for direct utilization and needs to be improved through protection and management measures, to enhance the quality of groundwater. Correlation analysis showed that groundwater quality was significantly dominated by TH, TDS, Na+, Mg2+, Cl− and SO42− concentrations.