Regional Geochemical Baseline Research Articles

Regional geochemical baseline based pollution assessment and dominant factors influencing metals in riparian sediment of Yangtze River, China

In this study, we assessed pollution status and potential risk of metals in riparian sediment of Yangtze River with geo-accumulation index (Igeo), ecological risk index (RI) and health risk index (THQ) by calculated regional geochemical baseline (RGB) values. We explored the influence of natural factor (sediment property) and anthropogenic factors (land use composition and landscape configuration) at different buffers (500 m, 1 km and 5 km) on metals in sediment using redundancy analysis (RDA) and variation partitioning analysis (VPA). Results indicated that RGB values can effectively model background values of metals (p < 0.01). Igeo and RI assessment showed that Cd was the primary pollutant, which showed no contamination to moderate contamination (Igeo > 0) and moderate ecological risk (ecological risk factor > 40) in upper downstream of the river. Besides, Cd showed moderate to strong contamination (Igeo > 2) and considerable ecological risk (ecological risk factor > 160) at site 24, which is located in the intersection of Poyang Lake and Yangtze River and strongly affected by natural erosion and human activities of Poyang Lake drainage. THQ assessment indicated low health risk of metals from consuming fish influenced by suspended sediment. RDA and VPA analysis indicated that explanation rate of land use composition, sediment property and landscape configuration on metals was 27.01–55.1 %, 36.66 %, 9.77 %-12.52 %, respectively. The total explanation rate was significantly higher at 1 km scale (82.5 %), which was mainly contributed by land use composition and its interaction with sediment property and landscape configuration (55.11 %). Specifically, percentage of farmland, grassland, wetland and forest, content of TN, TOC, silt and clay in soil and landscape configuration index of NumP were positively correlated with metals, and content of sand in soil and landscape index of MSI negatively correlated with metals in riparian sediment at different buffer scales. Our results offer valuable insights for safeguarding riparian zone.

Regional Geochemical Baseline Based Pollution Assessment and Dominant Factors Influencing Metals in Riparian Sediment of Yangtze River, China

Regional Geochemical Baseline Based Pollution Assessment and Dominant Factors Influencing Metals in Riparian Sediment of Yangtze River, China

Regional Geochemical Baseline Based Pollution Assessment and Dominant Factors Influencing Metals in Riparian Sediment of Yangtze River, China

Regional Geochemical Baseline Based Pollution Assessment and Dominant Factors Influencing Metals in Riparian Sediment of Yangtze River, China

An integrated exploration on health risk assessment quantification of potentially hazardous elements in soils from the perspective of sources

To make pollution evaluation of potentially hazardous elements in the soil more accurately, the regional geochemical baseline concentrations of eight potentially hazardous elements (Cr, Ni, Cu, Zn, As, Cd, Hg, and Pb) were established in Huilai County using cumulative frequency distribution curves. Then, the pollution load index and enrichment factor were applied to estimate the contamination levels, based on these geochemical baseline concentrations. The results suggested that topsoil was moderately polluted by potentially hazardous elements, while Cd pollution in the construction land and As pollution in the farmland was relatively severe. The possible sources of eight potentially hazardous elements were analyzed by correlation analysis, geostatistics and positive matrix factorization. Four sources have been determined and apportioned, namely industrial activities, natural sources, agricultural practices, and traffic emissions. Combining the health risk assessment with the source profiles, the health risks quantified from four sources were estimated under farmland, construction land, and woodland. The results showed that agricultural practices were the most main source of non-cancer and cancer risks under woodland and farmland for adults; industrial activities were the most main source of non-cancer and cancer risks under construction land for adults. Children's health risks, both carcinogenic risk and non-carcinogenic risk, were greater than adults, and the health risk trends of adults and children showed similarities. Therefore, agricultural practices under woodland and farmland should be controlled and managed as a priority, while industrial activities should be given priority to control and management under construction land.

Distribution of potentially toxic elements in soils surrounding abandoned mining waste located in Taltal, Northern Chile

Taltal is a commune located in Northern Chile, where former activities in copper ores processing left large amounts of mining waste enriched with potentially toxic elements, PTE. A soil pollution assessment using geochemistry and spatial distribution maps was conducted. A total of 101 surrounding soil samples from 3 abandoned mining waste sites (S1, S2, and S3) were taken to determine their content of PTE (Cu, Mo, Sb, Hg, Pb, Ni, Co, As, Mn, Cr, Cd, and Zn) and major elements. As guideline values of PTE in soils have not been established, the soil pollution index (PI) was assessed by comparing the soil PTE concentrations with the regional geochemical baseline (GBL) values and, for the first time, health risk for residents near Taltal city was evaluated.The measured PTE concentrations (mgkg−1) were Cu 18–6740, Mo 0.2–44, Sb 0.2–90, Hg 0.005–47, Pb 2.8–1510, Ni 7.0–138, Co 1.1–77.1, As 4.2–2691, Mn 83.4–11,400, Cr 7.7–46.1, Cd 0.05–23, and Zn 14.1–1394. Spatial distributions maps showed greatly polluted zones and under special concern are the concentrations of As, Co, Cu, Mo, Ni, Pb, Sb, Hg, Cd and Zn, which exceeded the GBL, the world-soil average and the USEPA and Finnish soil guidelines. Arsenic in site S2 and Cu and Pb in site S3 are the key factor that influences the potential ecological risk. Moreover, As in sites S1 and S2, and As, Pb and Cu in site S3 may pose non-carcinogenic effects for adults and children. Total cancer risk values were above the acceptable risk limit due to As, Cr, and Cd in sites S1 and S2, and due to As, Cr, Cd and Pb in site S3. Site S3, the largest abandoned site, represents the main environmental concern because of its high volume of waste and content of PTE. Based on the results, it can be suggested that the abandoned mining waste were dispersed and are the source of soil pollution in Taltal city. It is concluded that the abandoned mining waste sites have led to substantial contamination of the surrounding soils with As, Cu, Pb, Cr and Cd, which exceed ecological and/or human health risk guideline concentrations.

Assessment, Distribution and Regional Geochemical Baseline of Heavy Metals in Soils of Densely Populated Area: A Case Study.

To understand the content, pollution, distribution and source and to establish a geochemical baseline of heavy metal elements in soil under the influence of high-density population, the concentrations of heavy metal elements Cr, Mn, Co, Ni, Cu, Zn, As, Cd, Hg, Pb and Fe were determined in 23 soil samples in Suzhou University, and geo-accumulation index, enrichment factor, principal component analysis, spatial analysis and regression analysis were completed. The results showed the following: The elements Cu and As were slightly polluted, while the other heavy metal elements were not. The elements Cd, Cu, Ni and As in soils were mainly caused by agricultural activities of chemical fertilizer, whereas the elements Zn and Hg were impacted by the chemicals and batteries. The heavy metal elements in the north were lower than in the south of the campus, as a whole. The enrichment of elements Cu, As and Cd was caused by the east–west river on the campus, and the enrichment of the elements Mn, Ni and Zn was induced by the reservoir. Biochemical experiments and vehicle parking influenced the spatial enrichment of Cr, Co and Pb, while domestic waste led to the spatial differentiation of Hg concentrations. The regression curve between heavy metal elements and Fe was established, and the background values of the heavy metals Cr, Mn, Co, Ni, Cu, Zn, As, Cd, Hg and Pb are 50.90, 489.37, 11.76, 37.74, 55.70, 58.22, 20.07, 0.09, 0.08 and 24.13 mg/kg, respectively.

Lead Isotopes Combined with Geochemical Baseline in Sediments: A Novel Tool to Trace Anthropogenic Pb Sources.

Traditional Pb isotopic identification only based on total Pb concentration and Pb isotopic ratios, resulted in difficulty for tracing Pb sources in the complex environmental medium, especially for sediment. Herein, a novel approach combining with regional geochemical baseline (RGB) and Pb isotopic ratios are used to directly trace anthropogenic Pb sources and calculate Pb source appointments in sediment. In this study, total Pb concentrations and isotopic ratios were analyzed for a 7-m long sediment core (92 sediment samples) collected from a reservoir. RGB of Pb was used to calculate anthropogenic Pb concentrations (Rd), their contributions (CRd) and screen the sediments influenced by anthropogenic activities. Among those sediments influenced by anthropogenic activities, a positive correlation was found between 206Pb/207Pb ratios and Rd, indicating there were two anthropogenic Pb sources in sediment. Further source identification using 206Pb/207Pb and 208Pb/207Pb indicated that these two anthropogenic Pb sources originated from coal consumption and aerosol input. Finally, CRd and Pb isotopic ratios were used to calculate these two Pb source appointments (1.13% for coal consumption and 7.53% for aerosol input). This study demonstrated that source identification using RGB and Pb isotopes could be a novel attempt for identifying anthropogenic Pb sources in sediment.

Establishment of geochemical baseline and multiple assessment of vanadium pollution in sediment cores from the two cascade reservoirs, North China

Vanadium (V) is a potential toxic pollutant, and thus, V pollution in reservoir sediment should be scientifically evaluated because reservoirs are the main source of drinking water in China. However, the pollution assessment of V in reservoir sediment is often overestimated or underestimated due to the limitation for selecting local background values. In this study, the selection of the V background value in sediments was based on regional geochemical baseline (RGB) model. Multiple methods including geo-accumulation index (Igeo), potential ecological risk index (EI), and health risk assessment were applied to evaluate V pollution in sediment cores collected from the Panjiakou-Daheiting Reservoirs (PDR). The results show that the mean value of V concentrations in the PDR sediment cores was 92.86mg/kg (57.69-141.19mg/kg), which is higher than the soil background in Hebei Province and stream sediment values in China. V concentrations in the Panjiakou Reservoir were higher than those in the Daheiting Reservoir. The RGB value of V was 96.33mg/kg in the PDR sediments. A comparison of the V concentrations and RGB values in the sampling sites indicated that half of these sites are impacted by anthropogenic inputs. Among the sites influenced by human activity, the average anthropogenic contribution was 9.9%, suggesting that majority of V in the PDR sediments originated from natural source. The pollution assessments of V were evaluated using Igeo and EI with RGB as the background value, and results indicated that the sediments in the PDR were not polluted with V. The environmental impact assessment model was also established for calculating V accumulation in fish due to sediment resuspension. Then, health risk assessment model was applied to further calculate the health risk to residents due to fish consumption. The evaluated target hazard quotient demonstrated that local fish consumption produced no adverse effect on human health during sediment disruption.

Novel insights into Pb source apportionment in sediments from two cascade reservoirs, North China

Sediments act as crucial sink and source for metal contamination in aquatic environment of reservoir systems. However, the high complexity and heterogeneity of sediments make it difficult to trace the sources of metals in reservoir sediments. As a toxic metal, how to trace anthropogenic Pb sources in sediments is important for the water quality safety, especially in reservoir. Herein, 98 sediment samples collected from the connected Panjiakou Reservoir (PJKR) and Daheiting Reservoir (DHTR) were analyzed. A novel approach for tracing anthropogenic Pb sources was established by combining the regional geochemical baseline (RGB) and Pb isotopic ratios. The results showed that the mean concentration of Pb in these two reservoirs was 44.59 mg/kg, and the RGB value of Pb was 43.77 mg/kg. Pollution assessments using RGB and enrichment factor indicated that the influence of anthropogenic Pb is greater in DHTR sediments than in PJKR sediments. Based on the RGB model, samples influenced by anthropogenic activities (SS-AA) were screened and found in the DHTR. The anthropogenic Pb contribution in DHTR SS-AA was totally 35.29%. Moreover, the mean value of 206Pb/207Pb in DHTR SS-AA (1.107 ± 0.029) was slightly lower than those of natural inputs, indicating there was a small amount of anthropogenic Pb input in DHTR. The anthropogenic Pb sources were further identified using Pb isotopic ratios (206Pb/207Pb and 208Pb/207Pb) for DHTR SS-AA. Their apportionments were calculated with the help of the RGB model. The results showed that iron mining (20.42%) and coal combustion (14.87%) were the two main anthropogenic Pb sources. Aerosol deposition was likely the main pathway for coal combustion input. The results confirm that the proposed method of combining RGB and Pb isotopic ratios was a good attempt to trace the anthropogenic Pb sources in reservoir sediments.

Geochemical baseline establishment, environmental impact and health risk assessment of vanadium in lake sediments, China

Lakes are essential water resources in China and their water quality is vital to the sustainability. However, the geochemical processes of trace elements, especially those of seldom-monitored trace elements, have not been adequately studied. Here, the regional geochemical baseline (RGB) of vanadium (V) was established using cumulative frequency and normalization methods. Then, the RGB was applied to quantitatively calculate the anthropogenic contribution rate in sediments of the Poyang Lake (PYL), which is the largest freshwater lake in China. The pollution level and ecological risk of V were evaluated using the geoaccumulation index (Igeo) and potential ecological risk index (EI) with respect to three different reference values, namely local soil background values (BV), the RGB, and the median value of V concentrations. The health risk of V accumulation in residents through fish consumption during sediment resuspension was assessed by combining the environmental impact assessment model and health risk assessment model. The mean concentration of V in PYL sediments was 94.37 mg/kg (33.80–148.53 mg/kg), which was slightly higher than the levels in stream sediments in China, but lower than the local BV. The calculated RGB was slightly higher than the average V content in PYL sediments, but similar to the local BV. The average anthropogenic contribution rate was calculated as 11.48%, demonstrating low anthropogenic influence. Moreover, the result of Igeo and EI showed that V in PYL sediments was uncontaminated and posed a low ecological risk. In addition, based on the calculation by the two models, the human health risk result (target hazard quotient <1) indicated that the average human health risk from fish consumption due to sediment resuspension was negligible.

Pollution Characteristic of Ni in Sediments in the Three Gorges Reservoir

The Three Gorges Reservoir (TGR) has achieved the target of water storage of 175 m for eight consecutive years until October 2017. To study the temporal and spatial variation of nickel (Ni) in different water periods under 175 m operating conditions in the TGR area, probe the impact of a large-scale water conservancy project on the Ni enrichment, and establish the pollution evaluation system of Ni in the TGR area, we collected 173 surface sediment samples from the TGR area during four consecutive water periods from December 2015 to June 2017 and measured the Ni concentration by using inductively coupled plasma mass spectrometry (ICP-MS). The mean values of Ni in the four water periods are higher than the background value of Yangtze sediment and soil. At the spatial scale, the Ni content in the mainstream exhibits a clear upward trend from upstream to downstream and is lower than that of the tributary. The tributaries of the lower reaches shows a notably higher Ni content than the tributaries of the upper and middle reaches. At the temporal scale, the water period exerts an insignificant effect on the Ni content. The Ni content is relatively stable and shows a downward tendency at a 175 m water level. The regional geochemical baseline (RGB) value of Ni was obtained through building a geochemical baseline model in the area. The RGB values of Ni in sediments during four consecutive water periods are 47.0, 44.2, 42.9, and 41.9 mg·kg-1, respectively. The Ni contents in the middle and lower reaches of the mainstream and tributary are significantly affected by human activities. Moreover, the pollution evaluations based on global Ni background values, local background values, and geochemical baseline values as reference values were compared and the geoaccumulation index and potential ecological risk of Ni were determined to comprehensively assess its pollution risk. The assessment data indicate that Ni in the aquatic environment of the TGR area is almost uncontaminated and poses a low ecological risk, except for samples in regions around Fengdu County and Guizhou Town in the Zigui County along the mainstream, which were uncontaminated to moderately contaminated. Relative to global and regional background values, the pollution assessment results obtained using the RGB as a reference value are more scientific and better match the temporal and spatial variation of the study area.

Arsenic pollution of sediments in China: An assessment by geochemical baseline

Arsenic (As) contamination in sediments has been reported worldwide. However, few studies have investigated As contamination on a national scale in China. This study aims to address this gap by analyzing the existing literature on As contamination and sediment samples collected from ten main river basins: the Songhua River Basin (SRB), Liao River Basin (LRB), Hai River Basin (HRB), Yellow River Basin (YRB), Huai River Basin (HuRB), Yangtze River Basin (YtRB), Pearl River Basin (PRB), Southeastern River Basin (SeRB), Southwestern River Basin (SwRB), and Northwestern River Basin (NwRB). Regional geochemical baseline (RGB) values of As in the sediments of river basins were calculated to estimate human contributions of As using normalization and cumulative frequency distribution curves. The established RGB values in the SRB, YtRB, and PRB were higher than the corresponding regional soil background (RSB), possibly because of the high intensity of human activities in the SRB, YtRB, and PRB. Taking RGB and RSB values as the background references, contamination assessment yielded important information on As contamination in China. With high As contributions from Yunnan province, the PRB suffered from the highest level of contamination, and the mean human contribution of As in the PRB was 64.4%. The contamination levels in the less developed southwestern regions were even higher than in some river basins in economically developed regions (e.g., YRB). In addition, As in the PRB and YtRB was found to be partially contributed by industrial wastewater discharge, and the response of As contamination in sediments to industrial wastewater discharge was analyzed. The temporal change (2004–2016) of As in sediments from the PRB, YtRB, and YRB corresponded well with that of As discharged in wastewater within the corresponding river basins. This study thus serves as a valuable foundation for policies focused on ameliorating As contamination in China.

Identification of anthropogenic inputs of trace metals in lake sediments using geochemical baseline and Pb isotopic composition

Source identification of trace metals in the water environment is important in understanding its environmental behavior and in the prevention and remediation of further pollution. Here, the regional geochemical baseline (RGB) and Pb isotopic ratios are combined to decipher the anthropogenic contribution rate, main anthropogenic source, and transport pathway of trace metals in sediments collected from the largest freshwater lake in northern China, Baiyangdian (BYD) Lake. The established RGB values of Cr, Ni, Cu, Zn, Cd, and Pb were 63.0, 27.8, 24.7, 46.1, 0.18, and 22.0 mg/kg, respectively, which were slightly different from the regional soil background values. Based on the RGB and actual concentrations of trace metals in the lake sediments, the calculated average anthropogenic contribution were lower than 20% except for Cd. Compared with the other trace metals, Cd was the element most impacted by anthropogenic input, which was mainly caused by the point source pollution in some sites. The risk assessment (geo-accumulation index and potential ecological risk) using the RGB as the regional background values showed that BYD sediments were uncontaminated by the trace metals, and at low ecological risk from the trace metals. The results of these two risk assessments further validated the assessment of the anthropogenic contribution by the RGB. In addition, Pb isotopic ratios result showed that coal combustion was the main potential source of anthropogenic Pb in the BYD sediments and atmospheric deposition was the main transport pathway. This study tried to combine the geochemical baseline and Pb isotopic composition to identify the anthropogenic input of trace metals in the sediments. It will provide a new insight into assessing the anthropogenic contributions, identifying the main anthropogenic sources, and transport pathways of trace metals in water environment.

Multiple assessments of trace metals in sediments and their response to the water level fluctuation in the Three Gorges Reservoir, China

Response of trace metals to the consecutive water level fluctuation in the Three Gorges Reservoir (TGR) sediments remains unclear. Here, we evaluated the influence of consecutive stages of water level fluctuation on trace metal pollution using multiple analytical approaches. The spatio-temporal distributions of trace metals in TGR sediments were investigated for five consecutive water impoundment stages from 2015 to 2017. Anthropogenic contributions and trace metal stocks in the TGR were quantitatively estimated using a combination of a regional geochemical baseline (RGB) and annual sediment load. Results showed that trace metals were accumulated after the construction and impoundment of the TGR. However, after the TGR operated normally for more than five years, trace metals concentrations stabilized in sediments. Trace metal concentrations in the mainstream were slightly higher than those in the tributaries. In the mainstream, metal concentrations in the upstream were lower than those in the midstream and downstream except for Cd. Anthropogenic contributions of trace metals ranged from 8.51 to 24.86% and were highest for Hg and Cd. The sediment load was the main factor influencing trace metal stock in TGR sediments. Although the total Cd stock amount was relatively low, its potential ecological effects are of great concern due to its high mobile fraction percentages and toxicity. The RGB-based geo-accumulation index and potential ecological risk index showed that TGR sediments were uncontaminated, and were subject to low ecological risk from trace metals. This result differs from traditional assessment results, indicating that previous assessments may overestimate the ecological risks of the trace metals in the TGR. The health risks posed by trace metals bio-accumulated in fish, stemming from sediment resuspension, were assessed using an environmental impact assessment model. Results suggested that residents should not experience significant health risks from the intake of individual metals through fish consumption.

Regional geochemical baseline concentration of potentially toxic trace metals in the mineralized Lom Basin, East Cameroon: a tool for contamination assessment

The distribution of trace metals in active stream sediments from the mineralized Lom Basin has been evaluated. Fifty-five bottom sediments were collected and the mineralogical composition of six pulverized samples determined by XRD. The fine fraction (< 150 µm) was subjected to total digestion (HClO4 + HF + HCl) and analyzed for trace metals using a combination of ICP-MS and AAS analytical methods. Results show that the mineralogy of stream sediments is dominated by quartz (39–86%), phyllosilicates (0–45%) and feldspars (0–27%). Mean concentrations of the analyzed metals are low (e.g. As = 99.40 µg/kg, Zn = 573.24 µg/kg, V = 963.14 µg/kg and Cr = 763.93 µg/kg). Iron and Mn have significant average concentrations of 28.325 and 442 mg/kg, respectively. Background and threshold values of the trace metals were computed statistically to determine geochemical anomalies of geologic or anthropogenic origin, particularly mining activity. Factor analysis, applied on normalized data, identified three associations: Ni–Cr–V–Co–As–Se–pH, Cu–Zn–Hg–Pb–Cd–Sc and Fe–Mn. The first association is controlled by source geology and the neutral pH, the second by sulphide mineralization and the last by chemical weathering of ferromagnesian minerals. Spatial analysis reveals similar distribution trends for Co–Cr–V–Ni and Cu–Zn–Pb–Sc reflecting the lithology and sulphide mineralization in the basin. Relatively high levels of As were concordant with reported gold occurrences in the area while Fe and Mn distribution are consistent with their source from the Fe-bearing metamorphic rocks. These findings provide baseline geochemical values for common and parallel geological domains in the eastern region of Cameroon. Although this study shows that the stream sediments are not polluted, the evaluation of metal composition in environmental samples from abandoned and active mine sites for comparison and environmental health risk assessment is highly recommended.

Assessment of Cr pollution in tributary sediment cores in the Three Gorges Reservoir combining geochemical baseline and in situ DGT

The mobility and transfer of trace metals in sediments are vital to understanding trace metals environmental behavior in water environment. However, as a predominant aquatic carcinogen, an effective method for assessing the release and deposition for Cr at the sediment-water interface (SWI) is still not clearly understood. Here we established a comprehensive methodology to evaluate the release risk of Cr at the SWI combining regional geochemical baseline (RGB) and diffusive gradients in thin films (DGT). Sediment cores and water samples were collected in the two tributaries and mainstream of the Three Gorges Reservoir, which is the world's largest man-made hydroelectric station. Results showed that the calculated Cr carcinogenic risks in surface water did not exceed US EPA maximum recommended level. The RGB of Cr (85.53 ± 14.44 mg/kg) were calculated and the differentials between Cr concentration and RGB in surface sediments showed the average anthropogenic contribution rate was 6.03% and the upstream of Meixi River (MX-S) and mainstream were influenced by anthropogenic activities. The net diffusive flux using DGT showed that Cr in the midstream of Caotang River and MX had the potential to move upwards into the overlying water. Furthermore, combining the results of differential (Cr concentration vs. RGB) and the net flux, MX-S was the only site with a risk of Cr release. To the best of our knowledge, this study is the first attempt to combine RGB and DGT to scientifically assess metal release at SWI and provided a new perspective to comprehensively assess metal pollution in water environment.

Applying Bioassay Methods for Ecological Assessment of the Soils from the Brownfield Sites

Biological organisms, used as test objects in pollution tests may be as good, or even more so, in detecting soil contamination, than chemical analyses. In this study, we used five bioassay methods, together chemical and physical-chemical tests, for comprehensive environmental assessment of contaminated soils located at the industrial waste storage sites in North-West Russia. Examined soils have been contaminated with various toxic pollutants at various times in the past. The level of contamination by Hg, Pb, Cd, Zn, Со, As, Cr, Cu, Mn, V, and As in studied soils varied depending on a site type. The concentrations of these elements were 20 to 43 times higher than the regional geochemical baseline at all sites. The organic pollutants (3,4-benzo(a)pyrene and polychlorinated biphenyls) were found at some sites. Ecotoxicological studies were carried out using test organisms from different taxonomic groups: ciliates Paramecium caudatum Ehrenberg, green algae Scenedesmus quadricauda (Turp.) Brebisson, seeds of common oat Avena sativa L.,wheat Triticum aestivum L., and a natural community of microorganisms. All the employed bioassays revealed some of the aspects of contamination, supported or supplemented each other’s estimates, and gave excellent performance at the sampling sites.

Assessment of trace element pollution and human health risks associated with cultivation of mine soil: A case study in the Iberian Pyrite Belt

ABSTRACTA risk-based corrective action (RBCA) approach was conducted to assess the potential health risks associated with occupational and environmental exposures to trace elements in cultivated mine soil, reporting a site-specific environmental health and safety case study in the Spanish sector of the Iberian Pyrite Belt. The median concentrations of As in soil (580 mg kg−1), Cu (635 mg kg−1), Pb (2100 mg kg−1), and Zn (270 mg kg−1) largely exceeded the regional geochemical baseline, reaching values above which adverse health effects may potentially occur. The results of the RBCA analysis suggest the possibility that a median carcinogenic risk (9.3E-04) may be associated to arsenic exposure by ingestion and dermal contact pathways. In addition, the median hazard index was more than four times higher than the acceptable risk level, with As (hazard quotient value of 3.3) being also the largest single contributor to the overall non-carcinogenic risk. However, no detrimental health effects are expected to occur through inhalation of soil particles in people living near the source zone. Preventive measures should be applied to reduce surface soil exposure in the light of the results achieved.

How does temporal variation affect the value of stream water as a medium for regional geochemical survey?

Stream water is a key medium for regional geochemical survey for mineral exploration and environmental protection. However, stream waters are transient, and measurements are susceptible to various sources of temporal variation. In a regional geochemical survey stream water data comprise ‘snapshots’ of the state of the medium at a sample time. For this reason the British Geological Survey (BGS) has included monitoring streams in its regional geochemical baseline surveys (G-BASE) at which daily stream water samples are collected, over variable time intervals, to supplement the spatial data collected in once-off sampling events.In this study we present results from spatio-temporal analysis of spatial stream water surveys and the associated monitoring stream data. We show that the variability of monitoring stream data from the G-BASE surveys has a temporally correlated component which can be treated as independent between streams, and therefore as a component of the nugget (spatially uncorrelated variance) of the spatial variograms of stream water survey data. For the variables examined this component was small relative to the spatial variability, which indicates that the value of stream water data to provide spatial geochemical information is not compromised by temporal variability. However, these conclusions are conditioned on the particular data set which was collected only in the summer months, specifically to limit temporal variability. Temporal variation in stream water analyses may be less tractable in wetter conditions. We show how the spatial data from stream water surveys can be mapped by ordinary kriging, with the predictions interpreted as an estimate of the temporal (summer months) mean, and the kriging variance reflecting the partition of the nugget variance of the spatial variogram between spatial and temporal components.

The regional geochemical baseline soil survey of southern New Zealand: Design and initial interpretation

A multivariate geochemical baseline survey of soils from southern New Zealand has been completed. Soil samples were collected from 0 to 30cm ‘A-depth’ and 50–70cm ‘B-depth’ at 348 sites on an 8km-spaced grid covering 40,000km2 of the Southland and southern Otago regions. The sub-180μm fraction of all samples was analysed by inductively coupled plasma mass spectrometry following aqua regia (partial) digestion for 65 elements, and by Leco CS320 element analyser for total C and S. Sub-sets of the samples were analysed by XRF for 12 oxides/elements. Significant chemical variation in the soil samples can be linked to variations in source geology, soil type, climate and topography. Relatively high concentrations of certain elements (e.g. S, P, Pb, Hg, Cd), particularly in the A-depth, are attributed to anthropogenic sources such as fertilisers, paints, vehicle emissions or industrial emissions. Other elevated element concentrations, especially those in B-depth samples, are probably natural with high As, Bi, Sb and W reflecting proximity to Au mineralisation, Pt and Re near PGE mineralisation, and accumulation of heavy mineral-associated elements such as Cr in alluvium-derived soils related to the effects of both source material and hydraulic effects on flood plains. This study provides an important baseline that will benefit government, environmental, agricultural, forestry and mining sectors through improved regulatory guidelines and understanding of the regional geochemical landscape. This survey design, with minimal modification, is suitable for a national geochemical baseline survey for New Zealand.