Enrichment Of Pb Research Articles

Impact of different industrial activities on heavy metals in floodplain soil and ecological risk assessment based on bioavailability: A case study from the Middle Yellow River Basin, northern China

Understanding the impact of different industrial activities on heavy metals and conducting scientific ecological risk assessments are critical to the management of heavy metal pollution. The present study compared soils affected by different industrial activities in three types of industrial cities (coal city, oil-gas city, and economic city) to control samples and examined the ecological risk based on bioavailability in the Middle Yellow River Basin. The findings revealed that the impact characteristics of different industrial activities on soil heavy metals in the research area were different. Both coal-based and oil-gas industry activities had a minor impact on soil heavy metals, whereas economic industry activities in the southern part had a major impact, as evidenced by significant enrichment of Cd, Hg, Cu, Pb, and Zn. In principal component analysis, the soil heavy metals affected by economic industry activities designated a distinct source from the control samples, particularly the anthropogenic sources represented by Hg and Cd. In the context of heavy metals in chemical form, three types of industrial activities all had an effect on bioavailability (0.72–24.27%) and could increase migratory activity in the environment. Furthermore, both traditional and improved assessments, based on total content and bioavailability, showed a low ecological risk near coal cities and oil-gas cities in the middle and northern parts, while there was a medium-high ecological risk near economically developed cities in the south, particularly Tianshui, Baoji, Qishan, Xianyang, Xi'an, and Tongchuan. In comparison, improved risk assessment based on bioavailability tends to not only compensate for an overestimation in traditional risk assessment from the perspective of total content, but additionally achieve a more reasonable, effective, and advanced assessment of heavy metal risks in scientific research. The outcome of this study has significance for the ecological conservation and high-quality development of the Yellow River Basin.

Geochronology, geochemistry, and Sr–Nd isotopes of Permian dike swarms in the Beishan orogenic belt, southernmost Central Asian Orogenic Belt: Petrogenesis and implications for geodynamic setting

ABSTRACT Permian mafic dikes crop out widely within Beishan area in the southernmost Central Asian Orogenic Belt (CAOB). These mantle-derived products provide important clues for elucidating the genesis and geodynamic setting of Permian magmatism. The mafic dikes within the Beishan area display zircons U–Pb ages of 281 ± 4 Ma. Characterized by low SiO2 (44.88–47.73 wt.%) and high Mg# values (62.2–68.6), the type 1 dikes are relatively depleted in light rare earth elements (LREEs; (La/Yb)n = 0.72–1.43) but enriched in large ion lithophile elements (LILEs). They show high positive εNd(t) values (6.6–8.5) with a range of (87Sr/86Sr) i (0.703477–0.705789) ratios. In contrast, the type 2 dikes have higher SiO2 content (47.47–51.13 wt.%) and lower Mg# (40.9–63.0). They are enriched in LREEs ((La/Yb)n = 1.79–5.02) and LILEs, and have lower εNd(t) values (3.8–7.4) with a variable range of (87Sr/86Sr) i (0.702873–0.706949) ratios. Thus, the type 1 dikes resulted from lower degrees of fractional crystallization and contamination than the type 2 dikes. Considering the LILEs and Pb enrichments, high field strength elements depletions, and high Ba/Th (86–460) ratios, the mantle source was metasomatized by subduction-related fluids. These dikes should be derived from high degrees (>20%) of partial melting of a Sr–Nd isotope-depleted, phlogopite-bearing spinel lherzolite lithospheric mantle according to their high Rb/Sr (0.04–0.24), low Ba/Rb (0.9–3.3), low La/Sm, and constant Sm/Yb ratios in addition to Sr–Nd depletion. Combined with the coeval evidence of regional geology and novel tectonic discriminate diagrams, we suggest that the mafic dikes in Beishan area formed in arc-related setting rather than intracontinental setting during the Permian. The metasomatized lithospheric mantle by subduction-related fluids were heated by upwelling asthenosphere mantle triggered by the slab roll-back, resulting in the formation of the parental magma of the mafic dikes.

Effect of sodium alginate–gelatin–polyvinyl pyrrolidone microspheres on cucumber plants, soil, and microbial communities under lead stress

Lead is highly persistent and toxic in soil, hindering plant growth. Microspheres are a novel, functional, and slow-release preparation commonly used for controlled release of agricultural chemicals. However, their application in the remediation of Pb-contaminated soil has not been studied; furthermore, the remediation mechanism involved has not been systematically assessed. Herein, we evaluated the Pb stress mitigation ability of sodium alginate–gelatin–polyvinyl pyrrolidone composite microspheres. Microspheres effectively attenuated the Pb toxic effect on cucumber seedlings. Furthermore, they boosted cucumber growth, increased peroxidase activity, and chlorophyll content, while reducing malondialdehyde content in leaves. Microspheres promoted Pb enrichment in cucumber, especially in roots (about 4.5 times). They also improved soil physicochemical properties, promoted enzyme activity, and increased soil available Pb concentration in the short term. In addition, microspheres selectively enriched functional (heavy metal-tolerating and plant growth promoting) bacteria to adapt to and resist Pb stress by improving soil properties and nutrients. These results indicated that even a small amount (0.025–0.3 %) of microspheres can significantly reduce the adverse effects of Pb on plants, soil, and bacterial communities. Composite microspheres have shown great value in Pb remediation, and their application potential in phytoremediation is also worth evaluating to expand the application.

Occurrence, source identification and ecological risk assessment of heavy metals in water and sediments of Uchalli lake – Ramsar site, Pakistan

Uchalli Lake is an internationally significant Ramsar site that needs protection for supporting migratory birds. The current study aimed to assess wetland health by examining water and sediments utilizing total and labile heavy metals concentration, pollution indices, ecological risk assessment, water recharge and pollution induction sources through isotope tracer techniques. Al concentration in water was of serious concern as it was 440 times higher than the maximum acceptable concentration of Environmental Quality Standard of the UK for aquatic life in saline waters. Labile concentration predicted very severe enrichment of Cd, Pb, and moderate enrichment of Cu. Modified ecological risk index predicted very high ecological risk in sediments. The δ 18O, δ2H and D-excess values indicate that the lake was mainly recharged by local meteoric water. Enriched values of δ 18O and δ2H suggest a high evaporation of lake water, making lake sediments more enriched with metals. Isotopic and D-excess values of groundwater suggest a quick rainwater recharge to groundwater around the Uchalli Lake. Nitrates isotopes indicate that the rainwater runoff is main source of induction of fertilizers, pesticides and soil bonded metals in the lake system. The lake is recharged by rainwater runoff, from catchment areas, that erode the soil particles and agricultural residual waste dumped in the lake.

Environmental Geochemistry of Potentially Toxic Metals in Phosphate Rocks, Products, and Their Wastes in the Algerian Phosphate Mining Area (Tébessa, NE Algeria)

This study is focused on the environmental geochemistry of potentially toxic metals (PTMs)-bearing products and wastes in a mining area in Djebel Onk (NE Algeria) and their potential ecological and health risk assessment. Representative samples from (i) commercial products and (ii) grain size classes of wastes were mineralogically characterized using X-ray diffraction. The major and PTMs elements in the samples were chemically analyzed via ICP-AES and ICP-MS, respectively. The results reveal that the samples were mostly composed of carbonate fluorapatite (P2O5 > 24 wt %) and yielded PTM concentrations within the average range of phosphorites in neighboring countries and worldwide deposits as well. The concentrations of V, Cd, As, Ni, and Pb in the products were found to be within the acceptable values according to various standards, such as the Canadian and German Fertilizer Ordinance policies. Geochemically, PTMs distribution is linked to the main sub-composition of phosphate rock (apatite, clay, and dolomite). The Enrichment Factors (EF) display very-high-to-extremely-high enrichment of PTMs (Cr, Zn, As, Sr, Mo, Cd, Sb, Tl, Th, and U), while V, Co, Cu, Ni, Zr, Ga, Nb, and Pb show minor and moderate-to-high enrichments. Among all the PTMs, Cd, Tl, and U display a very high ecological risk (PERI) and contribute most to the total risk index (RI). The human health risk assessment of PTMs represented by the Hazard Index (HI) indicates that the non-carcinogenic risks are below the threshold values (HI < 1), while the HI values are higher for children than they are for adults. However, the cancer index (life time cancer risk) for Cr, Ni, As, and Cd for children and Cd for adults is greater than the acceptable threshold. These results are useful for phosphate beneficiation via removing these PTMs from the commercial product for efficient waste management.

Enrichment Characteristics of Heavy Metals and Health Risk in Different Vegetables

The health risk caused by heavy metal accumulation in vegetables is of great concern. In this study, a database of heavy metal content in a vegetable-soil system in China was constructed through literature review and field sample collection. A systematic analysis of seven heavy metal contents in edible parts of vegetables and their bioaccumulation capacity among different vegetables was also performed. Additionally, the non-carcinogenic health risks of four types vegetables were assessed by using Monte Carlo simulation (MCS). The mean values of Cd, As, Pb, Cr, Hg, Cu, and Zn in the edible parts of the vegetables were 0.093, 0.024, 0.137, 0.118, 0.007, 0.622, and 3.272 mg·kg-1, and the exceedance rates of the five toxic elements were:Pb (18.5%)>Cd (12.9%)>Hg (11.5%)>Cr (4.03%)>As (0.21%). Leafy vegetables showed high Cd enrichment, and root vegetables showed high Pb enrichment, with mean bioconcentration factors of 0.264 and 0.262, respectively. Generally, legumes vegetables and solanaceous vegetables showed lower bioaccumulation for heavy metals. The health risk results indicated that the non-carcinogenic risk for single elements of vegetable intake was within the acceptable range, with the health risk for children being higher than that for adults. The mean non-carcinogenic risk for single elements were:Pb>Hg>Cd>As>Cr. The multi-element combined non-carcinogenic risks of four types vegetables were:leafy vegetables>root vegetables>legume vegetables>solanaceous vegetables. Planting lower-heavy metal bioaccumulation vegetables in heavy metal-contaminated farmland is an effective method to minimize the health risk.

Integrated environmental assessment of iron ore tailings in floodplain soils and plants after the Fundão Dam disaster in Brazil.

Previous studies of the Doce River basin (Brazil) seem to be contradictory regarding the contamination of soils with potentially harmful elements (PHE). This research aimed to perform an integrated assessment of PHE in the soil-plant-tailing system from the area most affected by the iron waste after the Fundão Dam disaster in 2015. Different fractions of PHE (exchangeable, nonexchangeable, reducible, and pseudo-total) were determined on deposited iron waste (DIW), soil waste mixture (SWM), and control soil (CS) samples. Total contents of PHE in Poaceae were also determined, and Allium cepa bioassays were performed to determine DIW and CS cytotoxicity and/or genotoxicity to plants. The Fe and Mn contaminations were the only ones related to the deposition of DIW on floodplains, and other harmful element content (such as As, Hg, Ni, Cd, Cr, and Pb) was not found above baseline values for soils. In addition, a significant part of the Fe and Mn in DIW is readily available or subject to acidification and prolonged flood reduction processes. The high available content of Fe favored its excessive accumulation by Brachiaria. The DIW chemical conditions reduced biological functions of A. cepa under a controlled environment. However, more drastic effects, such as genetic damage, were not seen. The postdisaster action of covering DIW with CS resulted in undesirable enrichment of Pb on the floodplain soils. The integrated results allow the conclusion that the iron waste is not a time bomb for PHE contamination of soils between the Fundão and Risoleta Neves Hydroelectric Dam (~100 km away from Fundão). Integr Environ Assess Manag 2024;20:117-132. © 2023 SETAC.

Electrokinetic-Assisted Phytoremediation of Pb-Contaminated Soil: Influences of Periodic Polarity Reversal Direct Current Field

The effect of electric stimulation on the phytoremediation of Pb-contaminated soil by tall fescue and wheat seedlings was investigated by monitoring the time-dependent changes in soil properties and Pb accumulation in plants with or without a direct current (DC) exchange field. The results showed that plants could strengthen electrical conductivity (EC) and current in the soil environment. The periodic exchange electrode helped maintain a stable soil pH. Electric stimulation enhanced phytoremediation efficiency, and the enhancement effect increased with plant growth. Compared with the treatments without a DC exchange electric field, the Pb content in plots with tall fescue and wheat seedlings under DC exchange electric field increased 107–250.6% and 32.7–84.4%, respectively, after 30 d of planting. DC exchange electric field significantly increased the Pb enrichment coefficient of tall fescue and wheat seedlings. The upward transport of Pb from wheat seedling roots to shoots was greatly promoted by electric stimulation for 18 d. However, Pb transport in both plants was restrained after 18 d of electric stimulation. Additionally, DC exchange electric stimulation can improve the phytoremediation of heavy-metal-contaminated soil. More attention should be paid to the selection and testing of promising hyperaccumulators for electrokinetic-assisted phytoremediation of Pb-contaminated soil.

Comparison of Trace Element Deposition in Cupressus macrocarpa Leaves and Soils from a High-Pollution Area in the Puchuncaví Valley (Chile) Using a Biomonitoring Method

Located in the Puchuncaví Valley (PV) in central Chile is one of the most important and oldest industrial complexes (ICs) in the country. The PV is affected by anthropogenic emissions from the IC where the most important industry is a copper smelter and refinery. In this context, this study assessed the profile, concentration, and enrichment factors of the trace elements, both in the soil and in Cupressus macrocarpa leaves from this high-pollution-load area. The soil and leaf samples were taken from five selected sites, located between 0.8 and 15 km away from the IC. A total of 24 elements were analyzed by ICP-MS and examined by enrichment factor (EF), and PCA source analysis. Leaf concentrations of Ba, Ca, Cd, Cu, K, and Sr showed statistically significant differences between sampling sites (p-value < 0.05). In soil, element concentrations of Al, As, Ba, Cr, Cu, K, Li Mg, Mn, Na, Ni, Pb, and Ti showed statistically significant differences between sampling sites (p-value < 0.05). The source analysis of EFs in the samples of both soil and leaves detected three and four factors, respectively, related mainly to the industrial complex’s copper smelter and refinery, coal-fired power plants, and geogenic sources. According to the PCA, the leaf EFs of anthropogenic elements from copper smelting showed that La Greda (LG, site closest to the IC) was significantly enriched in the elements Cu, Zn, As, Mo, and Pb, while the EF in the soil from LG showed high enrichment in Cu and significant enrichment in Pb.

Effects of Chelating Agents Addition on Ryegrass Extraction of Cadmium and Lead in Artificially Contaminated Soil

This study investigated the removal of cadmium (Cd) and lead (Pb) from the soil through phytoremediation using ryegrass combined with chelating agents. Soil leaching experiments were employed to determine the extraction efficiencies of chelating agents, including ethylenediaminetetraacetic acid (EDTA), citric acid (CA), sodium glutamate tetra acetate (GLDA), oxalic acid (OA), and diethylenetriaminepentaacetic acid (DTPA) on Cd and Pb. Soil pot experiments were conducted to determine the effects of five different chelating agents—GLDA, EDTA, DTPA, CA, and OA—on the growth of ryegrass and the enrichment of Cd and Pb. The main findings were as follows: (1) the extraction efficiencies for Cd and Pb in soil were found to be GLDA > EDTA > DTPA > CA > OA and EDTA > DTPA > GLDA > CA > OA, respectively. (2) The aminopolycarboxylic acid class of chelating agents significantly reduced Cd and Pb contents in the weak acid extractable and reducible states in the studied soil, yet were less effective in the extraction of their residue state. Using chelating agents increased the proportion of residual heavy metals while reducing those in the weak acid extractable and reducible states in the soil, thereby mitigating the harmful effects of these heavy metals on the soil ecology.

Graphene oxide/Fe3O4@β-lactoglobulin nanocomposite for the enrichment of trace Pb(II) from real samples

A new GO/Fe3O4@β-lactoglobulin sorbent was prepared for selective extraction of trace Pb(II). The GO/Fe3O4@β-lactoglobulin packed column advantageously permeates samples faster than nascent GO column ca. 5 fold. We experimentally demonstrated the developed SPE method for the enrichment of Pb(II) from real samples (tap, river and packaged drinking water) before ICP-OES determination. The sulfhydryl groups of the vicinal cysteine and the carboxylic groups were led to successful chelate formation with Pb(II) ions. The method shows a detection limit of 0.30 ng mL−1 for Pb(II) ion. The prepared sorbent has a surface area and pore volume of 1460.37 m2g−1 and 1.36 ccg−1, respectively. The preconcentration limit and preconcentration factor for Pb(II) was found to be 0.37 μg L−1 and 900, respectively using 3 mL of eluent. At 95% confidence level, the Student's t-test was less than the critical Student's t value (4.303). A coefficients of variation for five replicate measurements is 3.45%, indicates good precision of the method.

Niche separation, dynamics, and transport pattern of trace elements along Antarctic krill (Euphausia superba) to its exclusive predator, mackerel icefish (Champsocephalus gunnari)

In this study, the dynamics of the trophic niches and the accumulation and transfer of four trace elements—Cu, Cd, Zn, and Pb—from Antarctic krill (Euphausia superba) to mackerel icefish (Champsocephalus gunnari) were investigated. The results demonstrated that the average concentrations of Zn, Cu, Cd, and Pb in E. superba were significantly higher than those of the corresponding elements in C. gunnari. These trace elements have a biodilution effect through E. superba to C. gunnari, and Cu has the lowest biomagnification factor among those four trace elements. It is observed that the Cu concentration in E. superba is correlated with its δ15N and δ13C, and the enrichment of Pb in C. gunnari is affected by its δ15N.

Trace element variations of pyrite in orogenic gold deposits: Constraints from big data and machine learning

Orogenic gold deposits represent key global gold resources, yet its internal differences are poorly constrained. Pyrite is ubiquitous in orogenic gold ores, and its trace element geochemistry has significant implications for the ore-forming processes. However, the diffusion regularity and controlling factors of pyrite trace element geochemistry of orogenic gold deposits lack effective constraints. To address these issues, pyrite trace element geochemical data (4092 sets of data) from 67 orogenic gold deposits were compiled for big- data and machine learning analyses. The principal component analysis (PCA) divides the pyrite data into four groups according to trace element correlations: I) Au-As; II) Sb-Cu; III) Ag-Pb-Bi; and IV) Co-Ni-Te-Se-Mo. This division is likely ascribed to the element occurrence in pyrite. Partial least squares-discriminant analysis (PLS-DA) and Random Forests classification were used to identify pyrite trace elemental variations among orogenic deposits of different mineralization ages, wallrocks, and tectono-metallogenic settings. The results show that the influence on pyrite geochemistry from temporal variation is not obvious, and only Triassic and Jurassic orogenic-type auriferous pyrite shows enrichments of Cu, Pb, and Sb, which may reflect the multiple mineralization events in these deposits as Pb commonly occurs as cation in the fluids, while Sb usually occurs in the melt. The spatial difference is more distinct with less overlapping of confidence circles in PLS-DA and higher accuracy in Random Forests, which may have been associated with fluid source variation influenced by the geodynamic setting (mantle model, supposed by distinctive geodynamic variation from metallogenic belts in China) and source strata (metamorphic model, supposed by Archean deposits mostly hosted in green-schist phase besides China). Pyrite in orogenic gold ores hosted in different wallrocks can be differentiated by the different As, Pb, and Cu contents, as the contents of these elements vary widely in the wallrocks and participate in pyrite lattice through fluid-rock reactions. Random Forests regression reveals that pyrite As-Sb contents in pyrite show distinct negative correlations with ore-forming temperature, but Se content shows a non-linear influence. This suggests that the pyrite As-Sb-Se contents in orogenic gold ores can be used as a geothermometer. Furthermore, we suggest that the pyrite Co-Ni contents are not good indicators for the ore-forming temperature, as the low salinity fluid in orogenic gold systems makes Co-Ni difficult to form chloride complexes which is sensitive to temperature variation.

Geochemical Evidence of Ediacaran Phosphate Nodules in the Volyno-Podillya-Moldavia Basin, Ukraine

The sedimentary basin of Podillya (Volyno-Podillya-Moldavia) is situated in the southwest of the Ukrainian crystalline shield and belongs to the middle part of the Upper Neoproterozoic section of the Moguiliv-Podilska Group. By analyzing the primary oxide, trace, and rare-earth element compositions of the phosphate nodules in the area, this study sought to shed light on the potential precipitation characteristics of the Ediacaran Sea, where phosphate nodules were created. The mean major oxide contents of the nodules were 50.8 wt.% CaO, 34.2 wt.% P2O5, 5.29 wt.% SiO2, 4.77 wt.% LOI, 1.69 wt% Fe2O3, 1.63 wt% Al2O3, and 0.35 wt.% MnO. The average trace element concentrations were 183 ppm Ba, 395 ppm Sr, 13.4 ppm Ni, 32.7 ppm Cr, 62.2 ppm Zn, 764 ppm Y, 16 ppm V, 10.8 ppm As, 75.8 ppm Cu, 84 ppm Pb, 2.1 ppm U, 1.7 ppm Th, and 4.2 ppm Co. The trace element contents were generally low and indicated an assemblage of Cu, Y, As, Cd, and Pb enrichments in comparison to PAAS. The total REE concentrations varied from 1638 ppm to 3602 ppm. The nodules had medium REE (MREE) enrichments and showed similar REE patterns normalized to PAAS. All the nodules had strongly negative Ce, Pr, and Y anomalies and substantially negative Eu anomalies, with four samples being exceptions. These abnormalities suggest that oxic and suboxic sea conditions existed at the time the nodules formed. The extremely high REE concentrations are thought to be the result of REEs being redistributed between the authigenic and detrital phases that were created during the diagenetic equilibration of phosphate with pore water. The genetic hypothesis for phosphate nodule formation states that the nodules were generally formed in oxic and suboxic seawater and were precipitated on slopes in response to a significant upwelling from a deeper basin with abundant organic matter under anoxic/suboxic conditions. The majority of the organic material at the water–sediment interface of the seafloor underwent oxidation before phosphate was released into the pore water of the sediment.

Provenance and transport mechanism of gravity core sediments in the deep-water area of the Qiongdongnan Basin, northern South China Sea

Reconstructing the role of provenance and transport mechanism of sediments deposited in deep-water environments is often complex because of myriad of factors such as variability in sediment sources, tectonics, bottom morphology, climatic changes and sea level fluctuations as well as current regime. The South China Sea (SCS) is situated at the tectonic intersection of the Pacific, Eurasian, and Indo-Australian plates, and provides an excellent natural laboratory for understanding source-to-sink transport processes of fluvial sediments. The Qiongdongnan Basin (QDNB) is located in the northern part of the SCS, and the deep-water area (>300 m) of the QDNB has a good hydrocarbon source and hydrocarbon accumulation conditions with a tremendous thickness since the late Miocene-Quaternary. However, the complex sources and transport mechanisms of sediments in the QDNB are undefined. In previous study QDNB may have a major provenance or a mixture of sources. In this paper, the sediments of two cores from the deep-water area of QDNB have been analyzed using several sedimentological and geochemical approaches, including measurements of grain size distribution(433 samples), the occurrence of minerals, and trace element geochemistry(37 samples)as well as strontium and neodymium isotopes(20 samples).The granularity analysis results first show that the 19S37 core can be divided into three stages while the 19S40 core is divided into two stages by clear vertical variations in grain size characteristics. Chlorite (62.0%) and Muscovite (33.6%) appear to be the predominant minerals in the 19S37 core, while the mineral assemblage of sediments from 19S40 mainly consists of kaolinite (37.4%), muscovite (29.2%) and chlorite (27.1%). The primitive mantle standardization curves and chondrite standardized distribution patterns of 19S37 and 19S40 are consistent and display enrichments in Th, U, Pb, and Nd and depletions in Ba, Nb, Sr, and Eu. In addition, the content of Sr fluctuates greatly with depth, which should reflect the influences of sea level changes and the relative proportion of various provenance components. The 143Nd/144Nd ratios and εNd values of the sediments from 19S37 are higher than those of the sediments from 19S40, and all the εNd values show narrow variations and range from −10.085 to −11.080. We conclude that the sediments of the deep-water area in the upper Pleistocene-Holocene were mainly from the sources of the Red River, Taiwan, Pearl River, Hainan Island, and Vietnam. The transport mechanism of the sediments from Hainan Island can be explained by the short distance between the source region and the sedimentary site, while the large amounts of terrigenous sediment inputs derived from the Red River and advantageous morphology make the Red River the largest sediment source to cores 19S37 and 19S40. The transport distance and amount of Deep Water Current could be even more powerful to make Taiwan be the second largest source of modern sediments in QDNB.

Heavy metals contamination in sediments of Bharalu river, Guwahati, Assam, India: A tributary of river Brahmaputra.

This study aimed to assess heavy metals in the surface sediments of the Bharalu river, India. Metal concentrations ranged from 6.65-54.6 mg/kg for Ni, 25.2-250.0 mg/kg for Zn, 83.3-139.1 mg/kg for Pb, and 11940.0-31250.0 mg/kg for Fe. The level of metal contamination was assessed using sediment quality guidelines, geo-accumulation index (Igeo), enrichment factor (EF), pollution Load Index (PLI),Nemerow's pollution index (PIN), and potential ecological risk index. Pb exceeded the sediment quality guidelines at all sites indicating a potential threat to the river ecosystem. (Igeo) and EF also showed moderate to severe enrichment for Pb. Potential ecological risk (RI) showed low risk in the sediments, and Pb is the major contributor to ecological risk. Overall, pollution indices revealed comparably higher contamination of the sediments in the downstream sites than in the upstream site. PCA and correlation matrix analysis indicated both anthropogenic and natural origins for metals. Among anthropogenic sources, urban discharges and waste dumping could be mainly attributed to metal contamination in the river sediments. These findings may aid in developing future river management methods explicitly aimed at tackling heavy metal pollution to prevent further damage to the river ecosystem.

The accumulation and release characteristics of heavy metals on the cultivation environment in Gracilaria litters during decay process

Gracilaria bioremediates heavy metals (Cd, Cr, Pb, Ni, Cu, Zn, Fe, and Mn) and improves water quality in mariculture zones. However, Gracilaria litter produced during the growth and harvest process has become a critical bottleneck problem that limits the sustainable development of the Gracilaria cultivation industry. Experiments of decaying dried (dead) and frozen fresh (falling and dying) G. lemaneiformis and G. lichenosdies were carried out using the litterbag technique under laboratory-controlled and in situ conditions. The results showed that decay rates (k), decomposed time in 50 % (t50) and in 95 % (t95) varied between dried and frozen fresh Gracilaria and were different between G. lemaneiformis and G. lichenosdies. All Gracilaria samples showed an 80 %–90 % weight loss in 15–45 d. The variation in MAIs (accumulation index of metals) between the dried and frozen fresh Gracilaria litters differed significantly and provided evidence that metals could be imported or exported from litter to the environment. Based on our estimates from the 15–45 d experiment, the decay of Gracilaria can release and adsorb heavy metals. The enrichment of Fe, Pb, and Mn was more significant than the release, but the release of Cr, Zn, Cd, Pb, Cu, and Ni was more significant than the enrichment. Heavy metals in Gracilaria litters were accumulated and released simultaneously during decay. The present study simulated and underscores that Gracilaria cultivation intensely influences heavy metals recycled in marine environments It provides a theoretical basis for seaweed management for the sustainable development of the seaweed industry in the mariculture zone.

The last Neoproterozoic rift magmatism on the western margin of Yangtze block, South China: New insights of Marinoan onset from low-δ18O magmatic events

The geological record preserves evidence of “Snowball Earth” glaciations during the Cryogenian Period, the Sturtian onset at ca. 720 Ma and the Marinoan onset at ca. 650 Ma. Compared to the Sturtian, the trigger for the Marinoan is still unclear due to the absence of large igneous provinces (LIPs). This study first discovered low-δ18O Luoluobuzi (LLBZ) granite which emplaced on the eve of the Marinoan at the Yangtze Block in South China. The granite with U-Pb age of 651.2 ± 2.1 Ma and has εHf (t) values between + 6.8 to + 13.3, and low-δ18O values between + 2.74 to + 5.34 ‰. Granite samples show Ba, Nb, Ta, Sr, Eu, and Ti depletion and enrichment in Rb, U, Th, and Pb, modeling calculations to suggest they originated from partial melting of nearby Neoproterozoic mafic rocks and formed in a continental rift. We systematically compiled data and found an interglacial period between the Sturtian-Marinoan glaciations is absent of magmatic activities. Extensional magmatic activity similar to the LLBZ granite started at ca. 651 Ma, which within errorsoverlapped the onset of the Marinoan. Such temporal ruling also existed in other worldwide rift-related magmatic activities. After combining chemical index of alteration (CIA) and palaeomagnetic results, we found the last episode of Rodinia breakup played an important role in the onset of the Marinoan.

Effects of mowing on Pb accumulation and transport in Cynodon dactylon (L.) Pers

Bermudagrass is a perennial herb with the potential to remediate Pb pollution in soils, and it has mechanical resistance to shearing. However, the effects of mowing on Pb absorption and accumulation in bermudagrass are still unclear. In this study, we investigated the effects of different quantities (0, 1, 2, 4 applications) of mowing treatments under 200mg L-1 Pb application on Pb accumulation and transport in bermudagrass and explored the related mechanisms. Compared to the Pb treatment, all of the mowing treatments greatly decreased root Pb concentration/accumulation, significantly enhanced Pb concentrations/accumulations in stubble stems and stubble leaves, and ultimately promoted Pb enrichment and transport. Of the treatments in this study, two applications of mowing best promoted Pb enrichment, and four applications of mowing best promoted Pb transport efficiency. Furthermore, mowing mediated the microdistribution and physiological patterns of Pb in bermudagrass and affected the Pb transport by changing the subcellar distribution patterns and chemical forms of Pb in various tissues. Additionally, mowing promoted the transport of all mineral elements and showed a synergistic relationship with Pb absorption and transport. The change in mineral element metabolism patterns may be an important reason why mowing promoted Pb accumulation in bermudagrass. Our study provides the first comprehensive evidence regarding mowing facilitating the absorption, accumulation and transport of Pb in bermudagrass. Moderate mowing may be an effective strategy to assist in soil Pb remediation using bermudagrass.

Potential roles of the rhizospheric bacterial community in assisting Miscanthus floridulus in remediating multi-metal(loid)s contaminated soils

Phytoremediation technology is an important approach applied to heavy metal remediation, and how to improve its remediation efficiency is the key. In this study, we compared the rhizospheric bacterial communities and metals contents in Miscanthus floridulus (M. floridulus) of four towns, including Huayuan Town (HY), Longtan Town (LT), Maoer Village (ME), and Minle Town (ML) around the lead-zinc mining area in Huayuan County, China. The roles of rhizospheric bacterial communities in assisting the phytoremediation of M. floridulus were explored. It was found that the compositions of the rhizospheric bacterial community of M. floridulus differed in four regions, but majority of them were heavy metal-resistant bacteria that could promote plant growth. Results of bioconcentration factors showed the enrichment of Cu, Zn, and Pb by M. floridulus in these four regions were significantly different. The Zn enrichment capacity of ML was the strongest for Cu and stronger than LT and ME for Pb. The enrichment capacity of LT and ML was stronger than HY and ME. These bacteria may influence the different heavy metals uptake of M. floridulus by altering the soil physiochemical properties (e.g., soil peroxidase, pH and moisture content). In addition, co-occurrence network analysis also showed that LT and ML had higher network stability and complexity than HY and ME. Functional prediction analysis of the rhizospheric bacterial community showed that genes related to protein synthesis (e.g., zinc-binding alcohol dehydrogenase/oxidoreductase, Dtx R family transcriptional regulators and ACC deaminase) also contributed to phytoremediation in various ways. This study provides theoretical guidance for selecting suitable microorganisms to assist in the phytoremediation of heavy metals.