Effect of mine tailing on the spatial variability of soil nematodes from lead pollution in La Union (Spain)

Potentially toxic element bioaccumulation in consumed indoor shrimp farming associated with diet, water and sediment levels

Shrimp production is an important industry for many countries and shrimp consumption is increasing worldwide. Shrimps are a highly nutritional food, but can pose a risk for human health if subject to high levels of environmental contaminants. This work studies the presence of As, Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn in shrimps from Ecuador and compares them to such contents noted in other shrimp-production areas in the world to evaluate the possible risks associated with these elements for consumer health, and to relate them to potentially toxic element (PTE) contents in water, sediments and diets, and also to animal biometric parameters. The PTE levels (mg kg-1 DM) obtained are as follows: in the head-As (3.52-6.11), Cd (0.02-0.10), Co (0.14-0.49) Cr (0.23-4.89), Cu (99.9--233.0), Ni (0.52-1.86), Pb (0.24-1.09), Zn (51.8-100.5) and Hg (μg kg-1 DM) (10.00-66.81); in the tail-(0.91-3.21), Cd (0.01-0.02), Co (0.01-0.43) Cr (0.01-6.52), Cu (20.0-72.44), Ni (0.15-2.03), Pb (0.01-0.69), Zn (31.2-66.1) and Hg (μg kg-1 DM) (10.00-67.18). The concentration of all the PTEs is generally lower than the limits set for seafood by European regulations, except for As in the cephalothorax (4.63 mg kg-1). Different behaviours for PTE accumulation in shrimps were found, which preferentially tend to accumulate in the cephalothorax, except for Hg (40.13 μg kg-1 DM), which accumulates in muscle (body) and is associated with contents of proteins, lipids and total shrimp weight. Nonetheless, the target hazard quotient (THQ) values for PTEs indicate that the consumption of shrimp muscles from Ecuador does not pose a human health risk because the values of these indices are below 1 in all cases.

Characteristics and pollution risks of potentially toxic elements and nematode community structure on farm soil near coal mines

As one of the most important coal-producing provinces of China, Shanxi Province has been concerned about soil potentially toxic elements (PTEs) contamination in recent years. The study aimed to determine the status and sources of PTEs contamination and evaluate the quality of the soil ecology. This study investigated the degree of 13 PTEs contamination. The sources and contributions of PTEs were traced by the absolute principal component score followed by a multiple linear regression model (APCS-MLR). And the status of the soil ecosystem was verified by evaluating the soil nematode community around the coal mining areas in Jinzhong. The results showed that the mean PTEs concentration of 5 trace elements were higher than the background values of Shanxi, and safe to considerable was indicated by the pollution and ecological risk values. Soil Hg was the most contaminated element, followed by Cd. The distribution of PTEs was determined by coal mining activities (44.72%) followed by agricultural practice (32.37%) and coal transportation (21.37%). The nematode genera Acrobeloides (4.01%), Aphelenchus (20.30%), Meloidogyne (11.95%) and Aporcelaimus (2.74%) could be regarded as bioindicators of soil PTEs contamination by their tolerance. Concentrations of soil Cr, Mn, Ti and Cd showed remarkable influences on the total nematode abundance, maturity index, enrichment index, structural index, Shannon-Wiener diversity index and Pielou index of soil nematode. It is an appropriate method to evaluate the status of soil PTEs contamination combining the response of a single nematode genus and the nematode community evaluation index.

Spatial Distribution Profiles and Human-Health Risks of Heavy Metals in Surrounding Area Surface Soils of a Petrochemical Complex

Despite the growing concern raised by organic pollutants from the petrochemical industry to the surrounding soils, the heavy metal (HM) pollution in these soils remains understudied. This study investigated the levels, potential sources, and human-health risks of 12 HMs in soils inside and in surrounding areas of a petrochemical complex. Generally, the levels of 12 HMs in all soil samples were lower than the national standard of China, except for the Cd in one surrounding soil sample. Approximately 40.9% and 98.1% of soils around and inside the petrochemical complex, respectively, were at slightly contaminated levels. The HM pollution in 94.4% of soils inside and 32% of soils in surrounding areas were mainly affected by petrochemical production. Human-health risk showed that although As posed an acceptable cancer risk for adults both in and around the complex, high cancer risk for surrounding children from As was observed. Moreover, around the complex, Cr, Cd, and Pb posed acceptable cancer risks for children, while Cd posed an acceptable cancer risk for adults. The spatial distribution of the health risks decreased with increasing distance from the complex. Overall, our results demonstrate that it is essential to minimize human exposure to HMs originating from the petrochemical industry, especially As, Cr, Cd, and Pb.

Life in a Contaminated Environment: How Soil Nematodes Can Indicate Long-Term Heavy-Metal Pollution

We investigated the genera, trophic groups, and functional guilds of soil nematodes at five alluvial meadows along the Litavka River in the Czech Republic to assess their usefulness as indicators of heavy metal pollution in soils. The Litavka River flows around the waste-sedimentation pond of a smelter in the city of Příbram in the Central Bohemian Region. Lead, zinc, and arsenic are the main pollutants in the soils in the vicinity of the smelter. The alluvial meadows closest to the pond and mine waste were the most heavily polluted sites, and contamination decreased downstream along the river with increasing distance from the sources of pollution. The nematode communities were sensitive to pollution, with the most contaminated sites having considerably fewer nematode individuals, fewer genera, and a less diverse and more degraded food web with less nematode biomass. Arsenic, lead, and zinc contents were significantly negatively correlated with the numbers of bacterivores, predators, omnivores, plant parasites, and fungivores, which were significantly less abundant at highly polluted sites. This correlation suggests that nematode groups with higher c-p values, and those with c-p 1 and 2 designations, can be useful indicators of high heavy-metal contamination in areas polluted for a long time. In contrast, the abundance of c-p 3 plant parasitic nematodes was positively correlated with copper, nickel, and zinc contents and with soil-moisture content in the alluvial meadows. Maturity index (MI) and MI2-5 were the most sensitive indices of the degree of disturbance of the soil ecosystem, with enrichment index, structure index, and basal index indicating the altered decomposition channels and diminished structure of the food web.

Multiple metals influence distinct properties of the Arabidopsis circadian clock

Circadian rhythms coordinate endogenous events with external signals, and are essential to biological function. When environmental contaminants affect these rhythms, the organism may experience fitness consequences such as reduced growth or increased susceptibility to pathogens. In their natural environment plants may be exposed to a wide range of industrial and agricultural soil pollutants. Here, we investigate how the addition of various metal salts to the root-interaction environment can impact rhythms, measured via the promoter:luciferase system. The consequences of these environmental changes were found to be varied and complex. Therefore, in addition to traditional Fourier-based analyses, we additionally apply novel wavelet-based spectral hypothesis testing and clustering methodologies to organize and understand the data. We are able to classify broad sets of responses to these metal salts, including those that increase, and those that decrease, the period, or which induce a lack of precision or disrupt any meaningful periodicity. Our methods are general, and may be applied to discover common responses and hidden structures within a wide range of biological time series data.

Nematodes as Ghosts of Land Use Past: Elucidating the Roles of Soil Nematode Community Studies as Indicators of Soil Health and Land Management Practices

Soil health is a matter of growing concern because of its degradation due to unsustainable anthropogenic activities over the last few decades. It is maintained by interactions among the components of the soil food web commonly concentrated in the vicinity of the plant roots, called the rhizosphere. The soil food web is dominated by nematodes. They occupy various trophic positions because of their diverse feeding habits. The free-living forms are mainly dependent on soil bacteria and fungi for their nutrition, while the parasitic forms feed on plant roots. The population of these two groups is regulated by the activities of predatory nematodes which can be carnivorous or omnivorous. The soil nematodes thereby partake responsibilities in nutrient cycling, mineralization and decomposition pathways which, in turn, affects the aboveground productivity. This intricately connected food web structure is vulnerable to disturbances like increased soil salinity, acidity, nitrogen enrichment, tillage, crop rotations, fertilizers, pesticides, soil amendment techniques and heavy metal pollution. The effects are reflected by alterations in the abundance and diversity of soil nematodes belonging to various trophic groups. These alterations have been formulated into measurable indices like maturity index (MI), structure index (SI), enrichment index (EI) and channel index (CI). The faunal profile and metabolic footprints of soil nematodes are latest developments in the field of nematode community analyses. Though these indices cannot replace the conventional soil ecotoxicological assays, they can give added information about soil biology which can be utilized to design sustainable land use practices.

Spatial distribution and assessment of the human health risks of heavy metals in a retired petrochemical industrial area, south China

Petrochemical industries are widely distributed in China. As a negative consequence, heavy metals in petrochemical area can result in soil contamination. However, the relevant research of heavy metals contamination in petrochemical area was few. In this study, a total of 103 topsoil samples (<20 cm) and 25 profile soil samples were collected and examined in a retired petrochemical industrial area, South China. The results showed the mean contents of Hg, Cd, As, Pb, Ni and Cu were 0.18, 0.69, 16.22, 47.24, 31.62 and 93.06 mg kg^-1, respectively. The spatial distribution of six metals in topsoil was largely attributed to the industrial activities during the petroleum refining and transshipment process. Ni was the main pollutant in the petroleum refining process. While, the contamination of other metals mainly were caused by the leakage of the oil during transshipment. The migration of six metals to subsoil layers was also observable. In accordance, Hg, Cd, As, Pb, Cu, and Ni dropped by 95.02, 71.91, 89.45, 90.88, 99.22, and 65.07%, respectively, compared to their contents in topsoil. The contamination of the heavy metals was mainly caused during the process of petroleum refining and transshipment. The distribution of heavy metals in the factory was mainly affected by the industrial activities or the lateral infiltration of Lianhuashan River. Soil ingestion was the primary pathway for children and adults exposure to heavy metals. The total non-cancer human health risk induced by heavy metals was within the limit of USEPA (10^-6 a^-1). While the cancer risks alone induced by As through soil ingestion to children was 1.14 × 10^-6 a^-1, which exceeded the limit of USEPA. This study indicated that not only petroleum hydrocarbon but also heavy metals can cause soil contamination in a retired petrochemical industrial area, which provides a novel cognition. Altogether, measures should be taken in practice to substantially improve the soil quality in petrochemical industrial area.

Cd and Pb bioaccumulation in Eurasian watermilfoil (Myriophyllum spicatum) in relation to the role of metal contents in wetland sediments

The Choghakhor Wetland in Chaharmahal and Bakhtiari Province (Iran) has a significant role in maintaining water and sediment quality, because the wetland acts as a sink for contaminants that can pollute the aquatic ecosystem and affect human health. The present study uses a simple geostatistical technique to investigate the spatial variability of Cd and Pb in the Choghakhor Wetland to link the spatial variations of sediments to heavy metal contents in Myriophyllum spicatum. It was hypothesized that the heavy metal contents in the Choghakhor Wetland sediments impacted the concentration values in macrophytes. The value of heavy metals in sediments ranges from 0.54- to 1.84-μg/g dry weight (dw) for Cd, and from 1.32- to 2.46-μg/g dw for Pb, with a mean value of 1.12- and 1.82-μg/g dw, respectively. The mean value of Cd and Pb was 1.14- and 1.67-μg/g dw, respectively, in the aquatic macrophyte Myriophyllum spicatum, with corresponding ranges of 0.9-1.83-μg/g dw and 1.33-1.95-μg/g dw. There was a spatial structure in the Cd and Pb contents in the wetland sediments, with lower contents in the northern zone despite the values quantified in the south. We observed a direct spatial relationship between the Cd content in sediments and the Cd concentration in M. spicatum, and confirmed an effect of plant uptake for Cd. However, there were no significant differences between Pb in sediments and Pb in samples of M. spicatum, which implied that other factors like discharged industrial waste could also affect the accumulation of metals in plants. It can be concluded that spatial patterns indicated differences in the territory of the sediment Cd content at the Choghakhor Wetland localization in association with sediment enrichment. However, it was surprising that Pb did not show this pattern despite anthropic pressure.

Accumulation of heavy metals in phytoliths from reeds growing on mining environments in Southern Europe

In Southern Europe, soil contamination by heavy metals (HM) due to mining and industrial activities is a long-known problem. Yet, despite soils being widely contaminated through decades, some plants are still able to grow. Some of these plants, like giant reed (Arundo donax) or common reed (Phragmites australis) are capable of accumulating substantial amount of HM. These reeds also contain small silica structures in their shoots, called phytoliths. However, the role of phytoliths in reducing stress caused by these HM remains unknown. The aim of this work is then to determine if phytoliths represent a preferential structure for the bioacccumulation of HM in plants. Therefore, plants from mining-contaminated sites in Spain and France were sampled and HM concentrations in total plant shoots were compared to those in phytoliths for eight metal(oid)s: As, Cd, Cu, Mn, Pb, Sb, Sn and Zn. Results show that Arundo donax and Phragmites australis tend to accumulate Cd, Sb and Sn but limit the uptake of As, Cu, Mn, Pb and Zn in plant shoots despite that the concentration of these HM in soil is quite high. Therefore, reeds appear as tolerant to high metal concentrations in soils, and phytoliths are identified as preferential structures for encapsulation of As, Cu, Mn, Pb and Zn, while Cd, Sb and Sn were mainly found to be accumulated in organic tissues rather than in phytoliths.

Distribution and Contamination Assessment of Soil Heavy Metals in the Jiulongjiang River Catchment, Southeast China

A total of 63 soil samples were collected from three soil profiles (yellow soil, red loam, red soil) from Jiulongjiang river catchment to investigate the distribution, controlling factors, and toxic risks of heavy metals, including Cr, Mn, Fe, Cu, Zn, Cd, Pb, and Ni. The results showed that Cr and Cd in soils were enriched. The relationships between heavy metals and soil properties were assessed by principal component analysis. The results indicated that soil organic matter (SOM) played a fundamental role in controlling Cd and Pb in yellow soil and red loam sites. The Cd was significantly correlated with Pb and Cu, and Cr, Zn, Ni, Fe displayed strong correlations with each other, however, no statistical correlation was found between Cd and Cr. The enrichment factor and geoaccumulation index analyses showed that the soils in the study area were contaminated by Cd. Potential ecological risk analyses indicated that Cd posed a considerable ecological risk in yellow soils, and posed a moderate ecological risk in red loams and red soils.

Assessment of the human health risks of heavy metals in nine typical areas

Human health risks of five different heavy metals were assessed in nine typical areas in Asia, Europe, and Africa. The geoaccumulation index (I_geo) of arsenic (As) in Hyderabad (HB), cadmium (Cd) in Veles (VL), and lead (Pb) in Murcia (MC) were found to be 5, indicating extreme contamination. This is related to their high concentrations in soil. The concentration of As in wheat in Niger Delta (ND) and European Union (EU) areas were 3.3 and 2.55 mg/kg, which were 22 and 17 times respectively of the World Health Organization (WHO)/Food and Agriculture Organization (FAO) criteria. In general, the concentrations of heavy metals in wheats were higher than those in corns, indicating that heavy metals were easier to accumulate in wheats than in corns. The human risks induced by the carcinogenic metals As and Cd were much higher than those induced by noncarcinogenic metals in different exposure ways. The human health risks of heavy metals in different exposure ways were R_w-ing > R_c-ing > R_s-ing > R_s-der > R_s-inh. The human health risks induced by wheat ingestion for adults and children accounted for 67.75-97.52% and 69.52-98.04%, respectively, of the total human health risks. The total human health risks in the VL and MC areas were 1.58 × 10^-4 a^-1 and 1.3 × 10^-4 a^-1 for adults and 1.14 × 10^-4 a^-1 and 9.47 × 10^-5 a^-1 for children, respectively, which were significantly high according to the Environmental Protection Agency and International Commission on Radiological Protection. The ranking of the total human health risks in different areas were R_VL > R_MC > R_ND > R_EU > R_HB > R_KY > R_TB > R_MLV > R_NHM. The total human health risks of adults were higher than those of children.

Estimating the Spatial Distribution of Soil Properties Using Environmental Variables at a Catchment Scale in the Loess Hilly Area, China

A comprehensive understanding of the spatial distribution and dynamic changes of soil properties are the basis for sustainable land management. Topography and land use types are key factors affecting soil property variability. This study analyzed the effects of land use types and landscape locations on soil properties, based on data from 111 points of surface soil (0–20 cm) in the Zhujiagou catchment on the Loess Plateau of Northwest China. Soil properties include clay, silt, bulk density (BD), soil organic matter (SOM), total nitrogen (TN) and total phosphorus (TP). Land use types include slope farmland (SFL), terrace farmland (TFL), check-dam farmland (CDL), woodland (WL), shrub land (SL) and grassland (GL). Landscape locations include crest (CT), upper slope (US), middle slope (MS), lower slope (LS) and flat valley (FV). Topographical attributes were divided into primary and secondary (or compound) attributes. Correlation analyses were carried out between soil properties and terrain attribute, and multiple-linear regression models were established to estimate soil properties using land use types and topographic attributes as independents. Results indicated that significant differences in soil properties existed between six land use types, except for bulk density. Higher values of clay, silt, SOM and TN occurred in soils from check-dam farmland, but lower values in soils from shrub land. Significant differences among landscape positions were observed for clay, BD, SOM and TN. Clay, SOM and TN contents on flat valley (FV) positions were higher than those of other positions. Different correlations were found between soil properties and terrain attributes. The regression models explained 13% to 63% of the variability of the measured soil properties, and the model for Clay had the highest R² value, followed by TN, silt, BD, SOM and TP. Validation results of the regression models showed that the model was precise for soil bulk density, but the variation was large and a high smoothing effect existed for predicted values of other soil properties. For TP, the predicted result was poor. Further observations suggested that land use was the dominant factor affecting soil chemical properties. But for soil physical properties, especially for BD, topography was the dominant factor.

Sublethal and chronic effects of reclaimed water on aquatic organisms. Looking for relationships between physico-chemical characterisation and toxic effects

The use of reclaimed water for irrigation and aquaculture purposes is generally considered a reliable alternative for sustainable water management in regions with water scarcity. Many organic compounds, generally called compounds of emerging concern (CECs), have been detected in reclaimed water, which implies continuous exposure for aquatic organisms. To date no quality criteria have been proposed for this group of compounds. This work aims to assess the acute, sublethal and chronic effects of reclaimed water using two representative organisms of the aquatic compartment; the green alga Chlorella vulgaris and the microcrustacean Daphnia magna. The study comprises the 72 h-algal growth inhibition test, the D. magna feeding bioassay and the D. magna reproduction test. The results highlighted, for the selected characterised compounds, no differences in the concentrations between the different tertiary WWTP treatments, except for the particular case of carbamazepine. Considering seasonality, no differences were observed between the two different sample collection campaigns. The sublethal and chronic effects observed for these samples could not be explained by the lower concentrations found in the chemical characterisation. However, in the majority of cases, dilution of raw reclaimed water reduced the toxic effects of these samples. Several interactions among compounds can affect the mixture's toxicity. Canonical correlation analyses (CCA) were included to explore the potential relationships between the physico-chemical characterisation of reclaimed water and effects on aquatic organisms. The results corroborated the toxic effect of some pharmaceuticals, in particular beta-blockers and antibiotics, on the growth and yield of green algae, as well as inhibition of daphnia reproduction. Thus the CCA methods could help to elucidate the potential relationships between the physico-chemical characterisation and toxic effects by considering all the potential interactions.

Provenance and environmental risk of windblown materials from mine tailing ponds, Murcia, Spain

Atmospheric particulates play a vital role in the transport of potentially toxic metals, being an important exposure pathways of people to toxic elements, which is faster and can occur in a much larger scale than water, soil and biota transport. Windblown materials in abandoned tailing ponds have not been well examined. The objectives of this investigation were: to study the major physical and geochemical properties of the materials eroded by wind inside the tailing ponds, and to understand the relative contribution of different sources to its heavy metals concentration. Study area is located in Cartagena-La Union mining district (SE Spain), where metallic mining of Fe, Pb and Zn has been developed for more than 2500 years. Wind-eroded particulates were monthly collected at 3 different heights (20, 50, and 80 cm) from the ground for a period of a full year using 4 dust collectors. Four tailing samples and 4 surface soil samples from the surrounding hills were also taken. Dust, soil, and tailing samples were examined for pH, particle size distribution, electrical conductivity, calcium carbonate content, Pb, Cu, Zn, Cd, Mn, Co, Ni, Ti and Zr concentrations. The results indicated that very coarse textured, slightly saline, and almost neutral wind-eroded deposits were generated with a very high temporal variability throughout the year. They also showed that the concentration of Cd, Mn, Pb and Zn, in the dust samples is extraordinarily high (18, 1254, 1831, and 5747 mg kg^-1 respectively), whereas Co, Ni, and Cu had concentrations into the range of background concentrations found in the Earth's crust (3.8, 12, and 60 mg kg^-1 respectively). Besides, the concentration of both categories of heavy metals in the dust samples was higher than that in tailing and less than that of the soils. The barren surfaces of tailing ponds and also the surface soils of the surrounding area seem to be the major contributors to the dust collected. Therefore, abandoned mines as well as their tailing ponds should be rehabilitated by proper technologies and then well stabilized and/or covered by appropriate plant vegetation to control the transfer, particularly by air, of environmentally hazardous materials to other areas.

Mercury contents in relation to biometrics and proximal composition and nutritional levels of fish eaten from the Western Mediterranean Sea (Almería bay)

Total liver and muscle mercury, and muscular composition, biometrics and trophic levels, were determined in four species (Mullus surmuletus, Merluccius merluccius, Auxis rochei and Scomber japonicus) of the Mediterranean Sea (Almería Bay, Spain). Mercury levels did not exceed the maximum residue limit, and M. merluccius obtained the highest level in muscle. Considerable variations in Hg content among individuals were observed in non-gregarious species. A positive correlation between Hg and trophic level or length was found in muscle, but not in liver. Organs (liver or muscle) with major Hg accumulation depend on species; muscle in M. merluccius and liver in S. japonicus. The results indicate that Hg levels in fish depend on intra- and interspecies factors that should be taken into account in systems to monitor Hg levels.

Wood and bark of Pinus halepensis as archives of heavy metal pollution in the Mediterranean Region

Natural levels of heavy metals (HM) have increased during the industrial era to the point of posing a serious threat to the environment. The use of tree species to record contamination is a well-known practice. The objective of the study was to compare HM levels under different pollution conditions: a) soil pollution due to mining waste; b) atmospheric pollution due to coal-fired power plant emissions. We report significant HM enrichment in Pinus halepensis tissues. Near a burning power plant, Pb content in a tree wood was 2.5-fold higher that in natural areas (no pollution; NP). In mining areas, Cd content was 25-fold higher than NP. The hypothesis that HM contents in tree rings should register pollution is debatable. HM uptake by pines from soil, detoxification mechanisms and resuspended local soil dust is involved in HM contents in wood and bark.

The effects of vegetation cover on soil nematode communities in various biotopes disturbed by industrial emissions

Better understanding of interactions among belowground and aboveground components in biotopes may improve our knowledge about soil ecosystem, and is necessary in environment assessment using indigenous soil organisms. In this study, we proposed that in disturbed biotopes, vegetation play important role in the buffering of contamination impact on soil communities and decrease the ecological pressure on soil biota. To assess the effects of these interactions we compared nematode communities, known for their bioindication abilities, from four types of disturbed and undisturbed biotopes (coniferous forest, permanent grassland, agricultural field, clearings), where the main stress agent was represented by long-term acidic industrial emissions containing heavy metals (As, Cd, Cu, and Pb). To understand the ecological interactions taking place in studied biotopes, we studied abiotic factors (soil properties) and biotic factors (vegetation, nematode communities). Except significant increase in metals total and mobile concentrations in disturbed biotopes soil, we found acidification of soil horizon, mainly in the clearings (pH=3.68), due to SO₂ precipitation. These factors has caused in clearings degradation of native phytocoenoses and decrease in decomposition rate characterized by high amount of organic matter (C_ox=4.29%). Nematodes reacts to these conditions by shifts in trophic structure (bacteriovores to fungal feeders), increase in c-p 2 genera (Aphelenchoides, Acrobeloides, and Cephalobus), absence of sensitive groups (c-p 3-5, omnivores, predators), and decrease in ecological indices (SI, MI, MI2-5, H'). Similar contamination was found in forest biotope, but the nematodes composition indicates more suitable conditions; more complex community structure (presence of sensitive trophic and higher c-p groups), higher abundance and indices values, comparable with less stressed field and grassland biotopes. As showed our results, the vegetation undoubtedly plays an important role not only as a resource of services indispensable for the ecosystem, but also as a significant buffer of negative impacts acting within.

Entomopathogenic nematode food webs in an ancient, mining pollution gradient in Spain

Mining activities pollute the environment with by-products that cause unpredictable impacts in surrounding areas. Cartagena-La Unión mine (Southeastern-Spain) was active for >2500years. Despite its closure in 1991, high concentrations of metals and waste residues remain in this area. A previous study using nematodes suggested that high lead content diminished soil biodiversity. However, the effects of mine pollution on specific ecosystem services remain unknown. Entomopathogenic nematodes (EPN) play a major role in the biocontrol of insect pests. Because EPNs are widespread throughout the world, we speculated that EPNs would be present in the mined areas, but at increased incidence with distance from the pollution focus. We predicted that the natural enemies of nematodes would follow a similar spatial pattern. We used qPCR techniques to measure abundance of five EPN species, five nematophagous fungi species, two bacterial ectoparasites of EPNs and one group of free-living nematodes that compete for the insect-cadaver. The study comprised 193 soil samples taken from mining sites, natural areas and agricultural fields. The highest concentrations of iron and zinc were detected in the mined area as was previously described for lead, cadmium and nickel. Molecular tools detected very low numbers of EPNs in samples found to be negative by insect-baiting, demonstrating the importance of the approach. EPNs were detected at low numbers in 13% of the localities, without relationship to heavy-metal concentrations. Only Acrobeloides-group nematodes were inversely related to the pollution gradient. Factors associated with agricultural areas explained 98.35% of the biotic variability, including EPN association with agricultural areas. Our study suggests that EPNs have adapted to polluted habitats that might support arthropod hosts. By contrast, the relationship between abundance of Acrobeloides-group and heavy-metal levels, revealed these taxa as especially well suited bio-indicators of soil mining pollution.

Effect of soil properties, heavy metals and emerging contaminants in the soil nematodes diversity

Among soil organisms, nematodes are seen as the most promising candidates for bioindications of soil health. We hypothesized that the soil nematode community structure would differ in three land use areas (agricultural, forest and industrial soils), be modulated by soil parameters (N, P, K, pH, SOM, CaCO3, granulometric fraction, etc.), and strongly affected by high levels of heavy metals (Cd, Pb, Zn, Cr, Ni, Cu, and Hg) and emerging contaminants (pharmaceuticals and personal care products, PPCPs). Although these pollutants did not significantly affect the total number of free-living nematodes, diversity and structure community indices vastly altered. Our data showed that whereas nematodes with r-strategy were tolerant, genera with k-strategy were negatively affected by the selected pollutants. These effects diminished in soils with high levels of heavy metals given their adaptation to the historical pollution in this area, but not to emerging pollutants like PPCPs.

Soil as an archive of coal-fired power plant mercury deposition

Mercury pollution is a global environmental problem that has serious implications for human health. One of the most important sources of anthropogenic mercury emissions are coal-burning power plants. Hg accumulations in soil are associated with their atmospheric deposition. Our study provides the first assessment of soil Hg on the entire Spanish surface obtained from one sampling protocol. Hg spatial distribution was analysed with topsoil samples taken from 4000 locations in a regular sampling grid. The other aim was to use geostatistical techniques to verify the extent of soil contamination by Hg and to evaluate presumed Hg enrichment near the seven Spanish power plants with installed capacity above 1000 MW. The Hg concentration in Spanish soil fell within the range of 1-7564 μg kg(-1) (mean 67.2) and 50% of the samples had a concentration below 37 μg kg(-1). Evidence for human activity was found near all the coal-fired power plants, which reflects that metals have accumulated in the basin over many years. Values over 1000 μg kg(-1) have been found in soils in the vicinity of the Aboño, Soto de Ribera and Castellon power plants. However, soil Hg enrichment was detectable only close to the emission source, within an approximate range of only 15 km from the power plants. We associated this effect with airborne emissions and subsequent depositions as the potential distance through fly ash deposition. Hg associated with particles of ash tends to be deposited near coal combustion sources.

A label-free and portable graphene FET aptasensor for children blood lead detection

Lead is a cumulative toxicant, which can induce severe health issues, especially in children's case due to their immature nervous system. While realizing large-scale monitoring of children blood lead remains challenging by utilizing traditional methods, it is highly desirable to search for alternative techniques or novel sensing materials. Here we report a label-free and portable aptasensor based on graphene field effect transistor (FET) for effective children blood lead detection. With standard solutions of different Pb(2+) concentrations, we obtained a dose-response curve and a detection limitation below 37.5 ng/L, which is three orders lower than the safe blood lead level (100 μg/L). The devices also showed excellent selectivity over other metal cations such as, Na(+), K(+), Mg(2+), and Ca(2+), suggesting the capability of working in a complex sample matrix. We further successfully demonstrated the detection of Pb(2+) ions in real blood samples from children by using our aptasensors, and explored their potential applications for quantification. Our results underscore such graphene FET aptasensors for future applications on fast detection of heavy metal ions for health monitoring and disease diagnostics.

Nematode communities as indicators of the status of a soil ecosystem influenced by mining practices in Brazil

This study evaluated the effects of mining practices using soil nematodes as bioindicators. Soil samples represented four different subsystems found in the CeBio Research Center, including natural/undisturbed (rainforest (RF) and savannah (SA)) and disturbed (Eucalyptus spp. (EU) and grassland (GR)) subsystems. Ecological descriptors S (3.5-9.5), d (1.22-4.23) and MI (1.9-3.23) significantly differentiated the subsystem GR (high impact) from the other subsystems. Additionally, poorly covered soil (i.e., subsystem GR) negatively influenced the composition of nematode assemblages, and primarily so for nematodes with high c-p values. Among soil variables, pH strongly influenced the distribution of soil nematodes, negatively affecting the abundance of all c-p groups and diversity of nematodes. On the other hand, pH also positively affected FF and PP trophic groups in the subsystem GR. The similarity of subsystem EU and natural subsystems (RF and SA) suggests that soil restoration with Eucalyptus spp. appears to be an adequate management practice to promote the recovery of areas subjected to mining practices.

Climate change effects on enchytraeid performance in metal-polluted soils explained from changes in metal bioavailability and bioaccumulation

Climate change may alter physical, chemical and biological properties of ecosystems, affecting organisms but also the fate of chemical pollutants. This study aimed to find out how changes in climate conditions (air temperature, soil moisture content) affect the toxicity of metal-polluted soils to the soft-bodied soil organism Enchytraeus crypticus, linking enchytraeid performance with changes in soil available and body metal concentrations. Bioassays with E. crypticus were performed under different combinations of air temperature (20 and 25 °C) and soil moisture content (50% and 30% of the soil water holding capacity, WHC) in dilution series of three metal-polluted soils (mine tailing, forest and watercourse). After 21 d exposure, enchytraeid reproduction was determined, and soil available (extracted with 0.01 M CaCl2) and body Cd, Cu, Pb and Zn concentrations in surviving adults were determined. In general, Cd, Pb and Zn availability decreased upon incubation under the different climate scenarios. In the watercourse soil, with initially higher available metal concentrations (678 µg Cd kg(-1), 807 µg Pb kg(-1) and 31,020 µg Zn kg(-1)), decreases were greatest at 50% WHC probably due to metal immobilization as carbonates. Enchytraeid reproduction was negatively affected by higher available metal concentrations, with reductions up to 98% in the watercourse soil compared to the control soil at 30% WHC. Bioaccumulation of Cd, Pb and Zn was higher when drier conditions were combined with the higher temperature of 25 °C. Changes in metal bioavailability and bioaccumulation explained the toxicity of soil polluted by metal mine wastes to enchytraeids under changing environmental conditions.

Trace elements in different land use soils of Bangladesh and potential ecological risk

Bogra city is highly susceptible to environmental pollution due to overpopulation, rapid industrialization, and urbanization during the last decades. The levels of six trace elements (chromium, nickel, copper, arsenic, cadmium, and lead) in seven different land use soils in Bangladesh were assessed. The ranges of Cr, Ni, Cu, As, Cd, and Pb in studied soils were 6.3-256, 8.3-271, 13-279, 7.5-87, 0.09-29, and 5.3-624 mg/kg, respectively. The pollution load index (PLI) values for all land uses were higher than 1, indicating the progressive deterioration of soil due to trace elements contamination. In view of the potential ecological risk (PER), soils from all land uses showed moderate to very high potential ecological risk. Among the elements, As and Cd showed a higher potential ecological risk than the others.

Temperature-based bioclimatic parameters can predict nematode metabolic footprints

Nematode metabolic footprints (MFs) refer to the lifetime amount of metabolized carbon per individual, indicating a connection to soil food web functions and eventually to processes supporting ecosystem services. Estimating and managing these at a convenient scale requires information upscaling from the soil sample to the landscape level. We explore the feasibility of predicting nematode MFs from temperature-based bioclimatic parameters across a landscape. We assume that temperature effects are reflected in MFs, since temperature variations determine life processes ranging from enzyme activities to community structure. We use microclimate data recorded for 1 year from sites differing by orientation, altitude and vegetation cover. At the same sites we estimate MFs for each nematode trophic group. Our models show that bioclimatic parameters, specifically those accounting for temporal variations in temperature and extremities, predict most of the variation in nematode MFs. Higher fungivorous and lower bacterivorous nematode MFs are predicted for sites with high seasonality and low isothermality (sites of low vegetation, mostly at low altitudes), indicating differences in the relative contribution of the corresponding food web channels to the metabolism of carbon across the landscape. Higher plant-parasitic MFs were predicted for sites with high seasonality. The fitted models provide realistic predictions of unknown cases within the range of the predictor's values, allowing for the interpolation of MFs within the sampled region. We conclude that upscaling of the bioindication potential of nematode communities is feasible and can provide new perspectives not only in the field of soil ecology but other research areas as well.

Impact of 70 years urban growth associated with heavy metal pollution

Historical trends in trace element deposition were analyzed using herbaria specimens. We determined Al, Fe, Mg, Mn, Ca, Na, P, K, S, As, Cd, Cr, Cu, Ni, Pb and Zn contents in leaves of eight specimens collected in 1941. To assess changes, we collected the same plants from a botanical garden in 2012. The concentrations of major elements showed large species variability. However, temporal trends were predominately detected for heavy metals. The Cd, Ni and Cr contents in the 2012 leaves were 10, 13 and 16 times higher, respectively, than in 1941. Urban activities have substantially raised the levels of these metals in urban atmospheres due to changes in human activities over 70 years of urban growth. Nevertheless, Pb has decreased (126%) in recent decades thanks to controlled lead fuel combustion. In short, metal deposition trend to increase Cr, Ni and Cd levels.

Levels and variability of metals in soils of the province of Golestan (Iran)

Studying the concentration distribution of metals is necessary for soil pollution monitoring and maintaining environmental quality. To date, very little large-scale research has been performed to investigate metal contamination in developing countries. In this study, the content and spatial distributions of five metals (cadmium [Cd], copper [Cu], nickel [Ni], lead [Pb], and zinc [Zn]) were quantified based on 346 topsoil samples from 12 districts in the province of Golestan (northeast [NE] Iran). The concentration levels (mg/kg) of Cd, Cu, Pb, Ni and Zn varied from 0.02 to 0.36, 9.3 to 93.7, 6.8 to 44, 9.5 to 85.35, and 25 to 417.4, respectively. The average concentrations (mg/kg) obtained were as follows: Cd 0.12 ± 0.07, Cu 23.9 ± 9.07, Ni 34.88 ± 11.59, Pb 15.42 ± 5.81 and Zn 82.08 ± 30.87. Significant differences in the distribution of trace elements among districts were detected. The AzadShahr and BandarGaz districts displayed the highest metal concentrations. Greater metal values were obtained in the central, south, west, and NE areas, although Zn concentration was also high to the north of the province. Values of contamination factor and contamination degree indicated that the metal pollution level was on the order of Zn > Cd > Pb > Cu > Ni and that all of the metals belonged to a low or moderate pollution category. Ni and Cu levels derived from natural sources, whereas Cd, Pb, and Zn derived from anthropogenic activities with greater mean concentrations than reference concentrations.