Surface Soil Concentrations Research Articles

Quantitative assessment of Cd sources in rice grains through Cd isotopes and MixSIAR model in a typical e-waste dismantling area of Southeast China

Identification of Cd sources and quantification of their contribution to rice grain Cd is crucial for controlling accumulation of this toxic metal in rice grains. However, accurate assessment of the contribution of different Cd sources to grain Cd concentration in rice under actual field conditions is a challenge. In this study, we determined Cd concentration and their isotopic compositions in rice grains with respect to three potential Cd sources around an e-waste dismantling area in Taizhou City, Zhejiang Province, China. Results demonstrated that average Cd concentrations in grains, surface soils, atmospheric deposition and surface water were 0.32, 0.91, 1.99 mg kg−1 and 2.02 μg L−1, respectively. The δ114/110Cd values of grains, surface soils, surface water and atmospheric deposition ranged from 0.00 ‰ to 0.31 ‰, −0.21 ‰ to 0.14 ‰, −0.04 ‰ to 0.47 ‰, and − 0.25 ‰ to −0.18 ‰, respectively. The MixSIAR model indicated that contribution of soils, irrigation water and atmospheric deposition to grain Cd was 56.8 %, 24.8 % and 18.4 %, respectively, demonstrating soils as the major source of grain Cd in the study area. This study also highlighted significant contribution of irrigation water and atmospheric deposition to Cd concentration in rice grains. The Cd isotopic analysis provides a practical approach for source apportionment of grain Cd and data support for controlling Cd accumulation in rice around the e-waste dismantling area.

Microbial Proxies for Anoxic Microsites Vary with Management and Partially Explain Soil Carbon Concentration.

Anoxic microsites are potentially important but unresolved contributors to soil organic carbon (C) storage. How anoxic microsites vary with soil management and the degree to which anoxic microsites contribute to soil C stabilization remain unknown. Sampling from four long-term agricultural experiments in the central United States, we examined how anoxic microsites varied with management (e.g., cultivation, tillage, and manure amendments) and whether anoxic microsites determine soil C concentration in surface (0-15 cm) soils. We used a novel approach to track anaerobe habitat space and, hence, anoxic microsites using DNA copies of anaerobic functional genes over a confined volume of soil. No-till practices inconsistently increased anoxic microsite extent compared to conventionally tilled soils, and within one site organic matter amendments increased anaerobe abundance in no-till soils. Across all long-term tillage trials, uncultivated soils had ∼2-4 times more copies of anaerobic functional genes than their cropland counterparts. Finally, anaerobe abundance was positively correlated to soil C concentration. Even when accounting for other soil C protection mechanisms, anaerobe abundance, our proxy for anoxic microsites, explained 41% of the variance and 5% of the unique variance in soil C concentration in cropland soils, making anoxic microsites the strongest management-responsive predictor of soil C concentration. Our results suggest that careful management of anoxic microsites may be a promising strategy to increase soil C storage within agricultural soils.

Gross alpha/beta and radionuclide activity concentrations in soil, plant and some fruits around the Tehran Research Reactor

Human activities usually have some contamination as effluents from chemical industries and radionuclides from nuclear reactors. For assessing the probable radioactive contamination in vicinity of Tehran Research Reactor, The gross alpha and beta radioactivity concentrations in soil, pine and cedar leaves and some selected fruits (fig, apple, berry and pomegranate) were investigated using an alpha/beta spectrometer during 2021–2022. Also, the concentrations of artificial and natural radionuclides in samples were investigated by the method of gamma spectroscopy. The gross alpha activity concentrations in soil, pine and cedar leaves and some selected fruits samples are from 0.05 to 0.35 Bq/gr and 0.07–0.31 Bq/gr and 0.04–0.18 Bq/gr, respectively. The gross beta activity concentrations in soil, pine and cedar leaves and some selected fruit samples are from 0.73 to 4.25 Bq/gr and 0.21–3.97 Bq/gr and 1.01–2.71 Bq/gr, respectively. Average activities concentration of natural radionuclide 232Th, 238U and 40K in soil, pine and cedar leaves and some selected fruits are 31.89–16.23–582.73 Bq/kg and 1.84–0.99–84.60 Bq/kg and 1.98–1.09–72.08 Bq/kg respectively. From artificial radionuclides, just 137Cs is recognized in soil sample and the range of 137Cs concentration in surface soils was observed to vary in the range 0.85–2.21 (Bq/kg). The result showed that the Tehran Research Reactor activities not have increased the environmental radioactivity and radiation level in the area.

Effects of Chinese “double carbon strategy” on soil polycyclic aromatic hydrocarbons pollution

Polycyclic aromatic hydrocarbons (PAHs) and carbon dioxide primarily originate from the combustion of fossil fuels and biomass. The implementation of the Chinese “double carbon strategy” is expected to impact the distribution of PAH emissions, consequently influencing the spatial distribution trend of PAHs in surface soil. Therefore, it is crucial to quantitatively evaluate the effectiveness of the Chinese “double carbon strategy” on soil PAH pollution for the purpose of “the reduction of pollution and carbon emissions”. This study utilized 15,088 individual PAH concentration data from 943 soil samples collected between 2003 and 2020 in China, in conjunction with PAH emissions at a 10 km resolution, for meta-analysis. The calculated PAH emissions in this study are in line with the global PAH emission inventory (PKU-PAH-2007), with a relative standard deviation at the provincial level of less than 25 %. Subsequently, a novel method was developed using emission density and Kow of PAHs to predict PAH concentrations in surface soil based on a least-squares regression model. Compared to other environmental models, the method established in this study significantly reduced the percent sample deviation to less than 70 %. Furthermore, energy consumption data for China were simulated based on the implementation plan of the “double carbon strategy” to project PAH emissions and soil PAH levels for the years 2030 and 2060. The predicted PAH emissions in China were estimated to decrease to 41,300 t in 2030 and 10,406.5 t in 2060 from 78,815 t in 2020. Moreover, the heavily contaminated areas of soil PAHs (i.e., total PAH concentrations in soil exceeding 1000 μg kg−1) were projected to decrease by 45 % and 82 % in 2030 and 2060, respectively, compared to levels in 2020. These findings suggest that the implementation of the “double carbon strategy” can fundamentally reduce the pollution of PAHs in surface soil of China.

Lagging pollution of polycyclic aromatic hydrocarbons in the rebuilt e-waste site: From the perspective of characteristics, sources, and risk assessment

Little information is known regarding how the lagged pollution of polycyclic aromatic hydrocarbon (PAH) influenced the environment and human health after an e-waste dismantling site was rebuilt. This study investigated the characteristics, sources, and risk assessment of PAHs in a rebuilt e-waste site and its surrounding farmland by analyzing the samples of soil, dust, water, and vegetable. Concentrations of PAHs in soil, vegetable and water in the rebuilt site were relatively higher than in its surrounding farmland. The concentrations in surface soils, soil columns, dust, vegetables, and water varied from 55.4 to 3990 ng g−1, 1.65 to 5060 ng g−1, 2190 to 2420 ng g−1, 2670 to 10,300 ng g−1, and 46.8 to 110 μg L−1 in the e-waste site, respectively. On the farmland, PAH concentrations in surface soils, vegetables, and water ranged from 41.5 to 2760 ng g−1, 506 to 7640 ng g−1, and 56.6 to 89.2 μg L−1, respectively. A higher proportion of high-molecular-weight PAHs (HMW-PAHs) appeared in all multimedia compared with low-molecular-weight PAHs (LMW-PAHs). Diagnostic ratio together with positive matrix factorization (PMF) revealed that vehicle emission was the primary source in this area, and the activity of e-waste disposal was another important source in the rebuilt e-waste site. Based on the deterministic health risks, people working in the reconstructed e-waste site were exposed to low risks, whereas the residents living near the surrounding farmland were exposed to low risk. Sensitivity analyses indicated that exposure frequency and PAH concentrations were the main factors that influenced exposure risk. This study provides valuable insight into the comprehension of the lagging pollution effects of PAH on the environment and human health after the e-waste site was rebuilt.

Pesticide extraction from soil into runoff in North American and Australian croplands

Context Do some pesticides run off more than others? How does pesticide runoff vary with pesticide properties? Aims Improve understanding of pesticide runoff from croplands. Methods Concentrations in surface soil and in runoff from three Australian rainfall simulation studies and three rainfall simulation and five catchment studies in North American croplands were used. The ratio of event averaged runoff concentrations and the surface soil concentrations is the runoff extraction ratio. Key results Pesticide runoff concentrations were closely related to soil surface concentrations at the start of rainfall. Runoff extraction ratios were not significantly different for 13 pesticides with a wide range of properties, on gentle slopes (0–3%), but were significantly lower for three pesticides. On steeper slopes, runoff extraction was significantly greater for atrazine but lower for glyphosate and metolachlor. Low sloping, furrow irrigated fields had low sediment concentrations and low pesticide runoff concentrations for more tightly sorbed pesticides, but not for less sorbed pesticides. Runoff extraction was not significantly different for simulated and most catchment studies. Conclusions Similar runoff extraction ratios were due to similar hydrology and limited sediment concentrations. Different runoff extraction occurs on bare soil if (a) pesticides are leached from the runoff-mixing layer, requiring sorption coefficients less than two and significant infiltration, and no interflow, (b) sediment concentrations are either low (<2 g L−1) or high (>100 g L−1) and (c) pesticides have different concentration profiles in the runoff-mixing layer. Implications Conditions studied apply for croplands in the North American mid-west on silty soils and for Australian clay soils.

Contamination risk assessment and distribution of rare trace metal(loid)s in surface soil of Cerrito Blanco, Mexico using various contamination indices

In many regions of the world, soil contamination of trace metal(loid)s has become a serious problem. Several studies have used contamination risk indices to identify potential risks arising from excessive pollution, but the majority of these analyses have only focused on anthropogenic sources, making data from these studies less meaningful than those from the added past mining sites, which are considered in the present study. The main objective of this study was to examine the contamination of rare trace metal(loid)s in surface soil near the vicinity of historical mining activities. The concentrations and contamination risks of five rare trace metal(loid)s (B, Ba, Sb, Sn, and V) in surface soils were analysed for 39 soil samples collected from the surrounding areas of the past mining areas of Cerrito Blanco, Matehuala in San Luis Potosi, Mexico. The region has a long history of mining activities that has resulted in the release of trace metal(loid)s into the environment. The evaluation of the contamination risk was performed using single standard indices (i.e., geo-accumulation index and contamination factor) and multi-element standard indices (i.e., degree of contamination, modified degree of contamination, pollution load index, metal pollution index, and Nemerow pollution index). The mean trace metal(loid)s concentration in surface soils followed in the decreasing order barium (Ba) > boron (B) > vanadium (V) > antimony (Sb) > tin (Sn), with corresponding values of 48.15, 12.37, 5.36, 1.62, and 1.58 mg/kg, respectively. Evaluated contamination indices revealed that most of the soil samples were not polluted and were below the reference value. The measured values obtained from these indices revealed that the contamination is only caused by past mining activities and natural geological formations. The GIS interpolation technique was used to assess the spatial distribution patterns and mapping process of trace metal(loid)s. However, the contaminated area was less than 10 % of the studied area calculated using a traditional technique, which relies on the proportion of contaminated samples. The significance of this study lies on the processes contributing to soil contamination in Mexico's historical mining regions. The findings offer essential insights for developing appropriate remediation strategies and safeguards to improve soil quality. By considering not only anthropogenic sources but also historical mining activities, this work contributes to a more comprehensive understanding of soil contamination risks and broadens the scope of research in this field.

Source characteristics of polycyclic aromatic hydrocarbons and polychlorinated biphenyls in surface soils of Shenyang, China: A comparison of two receptor models combined with Monte Carlo simulation

The surface soil concentrations of 16 PAHs and 15 PCBs were simultaneously determined by gas chromatography-tandem mass spectrometry in 21 locations of urban areas of Shenyang. The average concentrations of PAHs and PCBs were 26.40 ± 34.68 mg/kg and 48.03 ± 27.47 μg/kg, respectively. Factor analysis with nonnegative constraints (FA-NNC) and absolute principal component score with multiple linear regression (APCS-MLR) model were used to explore and evaluate the sources of PAHs and PCBs in the study area. The results of FA-NNC showed that PAHs in soils were mainly from traffic emissions (49.64%), coal combustion (46.88%) and petrogenic source (3.49%). The PCBs in soils were mainly from commercial and high temperature combustion mixed sources (20.3%), combustion and industry emission mixed sources (21.1%), electrical equipment sources (22.2%) and traffic emission sources (36.4%). The results of APCS-MLR were consistent with those of FA-NNC. The uncertainty of FA-NNC and APCS-MLR model was analyzed by Monte Carlo simulation method. The results revealed the reliability of the two receptor models on source apportionment. The estimated carcinogenic risks indicated that the risks of PAHs in soils exceed the acceptable range (10−6-10−4), while the risks of PCBs were below the acceptable risk level of 10−6.

Atta mexicanawaste dumps are hot spots of soil nutrients in an urbanNeotropicalcloud forest environment

AbstractLittle is known about the activity of leaf‐cutter ants such asAtta mexicanain urban environments.This study evaluated the soil nutrient concentration ofA. mexicananests and waste dumps compared with adjacent soils to the nests as a control in a Neotropical urban environment.The high nutrient concentration values in waste dumps, such as total C (360%), total N (340%), ammonium (900%) and nitrate (270%) higher than those found in the adjacent soils, except for total P, P‐Bray and sulphates, indicate thatA. mexicanawaste dumps may be hot spots of high nutrient concentrations in surface soil of an urban ecosystem.

Soil Microbial Community and Soil Abiotic Factors Are Linked to Microorganisms’ C:N:P Stoichiometry in Larix Plantations

Ecological stoichiometry is an essential tool to understand carbon (C), nitrogen (N), and phosphorus (P) cycles and nutrient limitations. Plantations are usually managed to maintain specific age structures, but the impact of such management on microbial biomass and stoichiometric ratios remains unclear. We compared the stand ages of four Larix principis-rupprechtti Mayr. Plantations that were 15 years old, (young plantation, Lar15), 24 years old, (middle aged plantation, Lar24), 40 years old, (near-mature plantation, Lar40), and 50 years old, (mature plantation, Lar50), respectively, to determine the main factors that drive differences in the C:N:P stoichiometry of microorganisms. We demonstrated that the temperature, moisture, and nutrient concentrations in surface soil increased significantly with forest age. The stoichiometric ratios of elements in soil and microorganisms reached their maxima in the Lar40 and Lar50 plantations. Additionally, forest stand ages had a great influence on the biomass of microbial communities. Moreover, soil microbial community and soil abiotic factors are closely related to soil microorganisms’ C:N:P stoichiometric ratios. Specifically, changes in the microbial biomass C:N (MBC:MBN) were primarily correlated with bacteria, Gram-positive bacteria (G+), temperature, NH4+-N, and moisture in soil. Shifts in G+, actinobacteria, soil temperature, and total phosphorus were primarily associated with variation in microbial biomass C:P (MBC:MBP). Alterations in microbial biomass N:P (MBN:MBP) were correlated with bacteria, NH4+-N, water content, Gram-negative bacteria, and soil temperature. Overall, these results suggest that microbial elemental stoichiometric ratios could be affected by stand age and emphasize the importance of microbial communities and soil abiotic factors in shifting this dynamic change process.

Methylmercury content in soil and litter from the Amazonian rainforest and its potential fate during forest fires

Methylmercury in soils and vegetation from the Amazonian rainforest is still poorly studied. Hence, the aim of this work was to determine the total mercury [THg] and methylmercury [MeHg] concentrations in litter and surface soil, MeHg deposition via litterfall, and the MeHg fate during a forest fire in the Amazonian rainforest. Sampling of litter, soil (0–1, 1–2, and 2–5 cm), and ash was carried out before (BB) and after (AB) a prescribed forest fire. The results showed a low [THg] (34 ± 8 ng g-1) and [MeHg] (0.16 ± 0.03 ng g-1) value in litter, with a correspondingly low estimate of the MeHg litterfall flux (0.13 ± 0.03 μgm-2yr-1) which has been probably underestimated due to potential losses during the field experiment. In ashes, [THg] and [MeHg] values were 23 ± 8 ng g-1and 0.11 ± 0.04 ng g-1, respectively. Although a significant part of Hg contained in the biomass was lost during the fire, the [MeHg]/[THg] ratio was not affected by it and was the same in litterfall and ash (∼0.5%). In soil, the average [THg] BB value was 149 ± 12 ng g-1in the three layers and [MeHg] was between 0.8 and 1.0 ng g-1. The forest fire only affected the superficial soil, with a significant decrease of [THg] and [MeHg] in the 0-1 cm layer. Similarly, the decrease of the [MeHg]/[THg] ratio in the surface soil layer suggested that MeHg was more readily emitted or degraded than the other Hg species present.

Effects of simulated warming on soil properties and bacterial community composition in the Bashania faberi ecosystem

The terrestrial environment is significantly impacted by global warming. Uncertainty exists on how the Bashania faberi ecosystem, which contains the staple-food bamboo for giant pandas, respond to climate change. A two years OTC (open-top chamber) experiment was conducted in the Bashania faberi ecosystem to measure the impact of warming on soil properties and composition of bacterial community across four different warming levels in surface (0–10 cm) and subsurface (10–20 cm) soil. In 0–10 cm soil layer, warming had significant impact on nitrate nitrogen (NO3−-N). In 10–20 cm soil layer, warming significantly increased the soil organic carbon (SOC), total nitrogen (TN), and soil carbon to phosphorus ratio (C/P), while reduced bacterial diversity and nitrification. The nitrate nitrogen concentration in surface soil first decreased and then increased with increasing temperature, whereas it exhibited the opposite trend in subsurface soil. Warming significantly reduced bacterial α diversity and nitrification function in the subsurface soil. pH, SOC, C/N, and C/P were the main factors affecting the bacterial community, according to redundancy analysis (RDA). Overall, our research revealed that warming altered soil properties and bacterial community, with subsurface soil being more strongly affected than surface soil in terms of these changes, which further impacted the Bashania faberi ecosystem functions.

Short- and medium-chain chlorinated paraffins in agricultural and industrial soils from Shanghai, China: surface and vertical distribution, penetration behavior, and health risk assessment.

The widespread contamination of chlorinated paraffins (CPs) of the soil environment has raised global concern due to their highly persistent and toxic properties. However, little information is available regarding these industrial toxicants' spatial-vertical distribution and penetration potentials. In this study, short- and medium-chain chlorinated paraffins (SCCPs and MCCPs, respectively) were analyzed in pooled surface and core soils (0-45cm) samples collected from agricultural and industrial areas in Shanghai. ∑SCCP concentrations in agricultural and industrial surface soils ranged from 52.6 to 237.6 and 98.3 to 977.1ng/g dry weight (dw), respectively. ∑MCCP levels were comparatively higher and ranged from 417.2 to 1690.8 and 370.9 to 10,712.7ng/g dw in agricultural and industrial soils, respectively. C10Cl5-10 SCCPs and C14-15Cl5-7 MCCPs were the predominant homologues in all samples. Analysis of the soil vertical profiles revealed that MCCP concentrations decreased significantly with depth (P < 0.01). SCCPs more efficiently penetrated into thesoils than MCCPs because of their higher water solubility and less octanol-water partition coefficient (Kow) values. A preliminary risk assessment suggested no potential health risks caused by non-dietary exposure. The daily exposure doses of CPs via ingestion were significantly (P < 0.01) higher for children (5.41 ± 2.11 × 10-3 and 1.68 ± 1.03 × 10-2μgkg-1day-1) and adults (2.56 ± 0.99 × 10-4 and 7.94 ± 4.87 × 10-4μgkg-1day-1) than dermal permeation exposure. Furthermore, CPs at current levels posed low ecological risks (0.1 ≤ RQ < 1) according to the risk quotient model. This study enhanced our understanding of the fates and behaviors of CPs in the terrestrial environment.

Radiological risk assessment of outdoor 222Rn and 220Rn around rare earth element and uranium mines from northern Vietnam

The outdoor 222Rn and 220Rn concentrations at 320 sampling points at 1 m above the ground in different sites surrounding rare earth element (REE) and uranium mines from northern Vietnam were measured using the RAD7. Results showed that 222Rn concentrations were always higher than 220Rn concentrations with large variation ranges from 25.7 to 573 Bq m−3 and from 18.5 to 385 Bq m−3, respectively. The high correlation between 220Rn and 228Ra concentrations in surface soil of the studied sites were observed. The highest 220Rn and 222Rn concentrations are found at the sampling points of the REE NX-Lai Chau site. The 220Rn and 222Rn activities surrounding the REE mines were found to be higher than those surrounding the uranium mines. The average annual committed effective doses originated from the inhalation of 220Rn and 222Rn outdoor concentrations is about five times higher than the worldwide average value.

Source apportionment of heavy metals in the soil at the regional scale based on soil-forming processes

Source apportionment is crucial to the prevention and control of heavy metals in the soil. The major methods focus on the identification of soil heavy metals from different pollution sources. However, they are unsuited to the source apportionment at a regional scale due to ignoring the spatial heterogeneity of heavy metal content caused by soil formation. Thus, we built a source apportionment model by introducing the weathering and leaching coefficients as the key parameters of soil-forming processes. In this study, we selected Liaohe Plain in China as the study area, which was the starting point of China's industrial development, with dense industrial areas and high levels of heavy-metal emission. Heavy metals concentrations in surface and deep soil of reference and grid points were collected as model data. The results showed that the average contribution rates of soil-forming process to Cd, Hg, As, and Pb were 82.7%, 85.2%, 88.6%, and 91.7%, respectively, and those of anthropogenic activities were 17.3%, 14.8%, 11.4%, and 8.3%, respectively. Spatial distribution of contribution rates showed the superposition of soil environmental background and pollution sources. This study provides a feasible method to quantify heavy metals contents from natural and anthropogenic sources at a regional scale.

The persistence of time: the lifespan of Bacillus anthracis spores in environmental reservoirs

Anthrax is a lethal bacterial zoonosis primarily affecting herbivorous wildlife and livestock. Upon host death Bacillus anthracis vegetative cells form spores capable of surviving for years in soil. Anthrax transmission requires host exposure to large spore doses. Thus, conditions that facilitate higher spore concentrations or promote spore survival will increase the probability that a pathogen reservoir infects future hosts. We investigated abiotic and pathogen genomic variation in relation to spore concentrations in surface soils (0–1 cm depth) at 40 plains zebra (Equus quagga) anthrax carcass sites in Namibia. Specifically, how initial spore concentrations and spore survival were affected by seasonality associated with the timing of host mortality, local soil characteristics, and pathogen genomic variation. Zebras dying of anthrax in wet seasons—the peak season for anthrax in Etosha National Park—had soil spore concentrations 1.36 orders of magnitude higher than those that died in dry seasons. No other variables considered affected spore concentrations, and spore survival rates did not differ among sites. Surface soils at these pathogen reservoirs remained culture positive for a range of 3.8–10.4 years after host death. Future research could evaluate if seasonal patterns in spore concentrations are driven by differences in sporulation success or levels of terminal bacteremia.

Anthropogenic Contribution and Migration of Soil Heavy Metals in the Vicinity of Typical Highways

To reveal the secondary anthropogenic contribution and accumulation rate of heavy metals in highway-side soils, we studied soil heavy metals on three representative highways in Southeast China, with different traffic intensities, service years, land use patterns and distances from roads, with high-resolution sampling of soil profiles. Concentrations of soil Cu, Zn, Pb and Cd were measured. The comparison of concentrations in surface soils with original values and their vertical distributions shows that soils within 150 m of the highway side are contaminated by heavy metals, with surface accumulation and possible movement down the profiles. The transferring depth of heavy metals was 10–30 cm. The contribution ratios of heavy metals were 1.0–30.5% in the surface at 30 cm, with the sequence of Cd &gt;&gt; Cu &gt; Zn &gt; Pb. The accumulation rates were 1.27–2.03 kg Cu ha−1 y−1, 2.44–5.27 kg Zn ha−1 y−1, 0.71–1.40 kg Pb ha−1 y−1 and 0.010–0.018 kg Cd ha−1 y−1 in soils within 50 m range. Furthermore, the accumulation of these metals varied with the traffic intensity, service years and land use patterns. Soils under forest have less heavy metal accumulation, which suggests a protective forest to set beside highways at a distance of at least 50 m to prevent soils from being contaminated.

Characterization of Tidally Accumulated Plastic Waste and the Effect on Mangrove Ecosystems at Eagle Island, Niger Delta, Nigeria

Numbere, A.O. and Aigberua, A.O., 2023. Characterization of tidally accumulated plastic waste and the effect on mangrove ecosystems at Eagle Island, Niger Delta, Nigeria. Journal of Coastal Research, 39(2), 275–283. Charlotte (North Carolina), ISSN 0749-0208. Plastic pollution has become a global problem with the proliferation of numerous plastic goods. This study hypothesized that accumulated plastic waste will have a negative effect on the mangrove ecosystem and associated organisms. The study was performed in a sand-filled and deforested mangrove forest at Eagle Island, Niger Delta. Ten soil samples (n = 10) were collected under and around accumulated plastic waste at five different georeferenced sites. Samples of fish, crab, plastic, and foil from each site were collected and sent to the laboratory for physicochemical analysis of total hydrocarbon content (THC) and heavy metals, i.e. zinc (Zn), lead (Pb), and cadmium (Cd), using the HACH DR 890 colorimeter (wavelength 420 nm) and microwave accelerated reaction system (MARS Xpress, North Carolina, U.S.A.), respectively. Furthermore, microbial analysis was completed for the soil samples. A germination experiment was conducted in the laboratory using seedlings of Rhizophora racemose and Rhizophora mangle grown in plastic and nonplastic waste soils. The results show that no significant difference occurs in THC and heavy metal concentration in surface soils, subsurface soils (F1,30 = 1.83, P = 0.186), and soils collected around plastic waste (F3,28 = 0.60, P = 0.619). In contrast, a significant difference occurs in seedling growth between the control and plastic soils (F4,200 = 65.24, P < 0.001). Microbial population showed significant difference horizontally, i.e. some distance away from plastic waste (near, middle, and far; F3,11 = 3.86, P = 0.04) but not vertically (surface vs. subsurface; F1,11 = 4.60, P = 0.055). These results indicate that chemicals in plastic waste can migrate outwardly to contaminate neighboring organisms. Thus, plastic waste should be quickly removed from the forest to prevent its decomposition and deposition of chemicals that will move up the food chain, affecting humans who consume seafood.

Source Analysis of Heavy Metal Pollution Using UNMIX and PMF Models in Soils along the Shuimo River in Urumqi, China.

Eight kinds of heavy metals in soil within 0-2 km from the banks of Shuimo River in Urumqi were analyzed by using an X-ray fluorescence spectrometer and national standard detection methods. Unmix and PMF models are comprehensively used to analyze potential pollutant sources and contribution rates. Soil samples are sampled in three layers of 0-20, 20-40, and 40-60 cm, and each group of sample points in each layer is 5 m, 1 km, and 2 km away from the riverbank, respectively. Only the average concentration of Mn in each layer of soil is lower than the background value, according to the analytical results, while the average concentration of other heavy metals surpasses the background value. The highest proportion of exceeding the background value is Ni in the 40-60 cm soil layer, up to 1.92 times. Unmix and PMF models are used to analyze pollutants' source quantity and contribution rate, respectively. The results show that the two models can identify two pollution sources at the three soil layers, and their contribution rates are similar, and each index of the analysis results of the two models is within the required range of model reliability. By comparing with the Pearson correlation coefficient and distribution map of heavy metal concentration in surface soil, it is concluded that Zn, Pb, Cr, and Cu are mainly from industrial sewage and air pollution from coal combustion, while As, Mn, Ni, and V are mainly from agricultural pollution and light industrial pollution. In future research, it is necessary to investigate the change of heavy metal concentration in detail from the time dimension to further quantitatively calculate the potential pollutant source and contribution rate.

Characterization of polycyclic aromatic hydrocarbons in soil in a coal mining area, East China: Spatial distribution, sources, and carcinogenic risk assessment

The polycyclic aromatic hydrocarbon (PAH) pollution process in mining areas, particularly coal mining areas, has accelerated because of coal chemical production and gangue accumulation. In this study, PHAs concentrations in surface soil was determined via gas chromatography–mass spectrometry. The composition, spatial distribution and sources of PAHs were analyzed, and their potential carcinogenic risks were evaluated.Results showed a wide PAH concentration range (218–1548 ng g−1). The high molecular weight proportion in contaminated areas was significantly higher than in uncontaminated areas. Clear differences in PAH distribution were detected in contaminated areas, with higher concentrations in the soils near an industrial park and coal gangue piles. The results of positive matrix factorization (PMF) in contaminated area revealed that coking, oil and biomass combustion, and vehicle emissions and coal combustion, contributed 31%, 26%, 24%, and 19%, respectively, to the detected PAHs. In contrast with the 10% contribution rate of the coking source in uncontaminated areas. The Monte Carlo method was used to assess the cancer risk to residents in the study areas. The carcinogenic health risk values for adults in the contaminated areas was higher than the safety standard (2.92 × 10−6) prescribed by the United States Environmental Protection Agency at 95% confidence level. Sensitivity analysis showed that the relative exposure duration (ED) and soil surface area of skin exposure were the most significant parameters for adults, and ED and body weight for children. The cancer risk for both adults and children in contaminated areas was five times than that in uncontaminated areas.