Zn Contamination Research Articles

Rhizosphere fungi regulate the expression of metal tolerance genes in Solanum lycopersicum L. (Solanaceae) growing in a metal(loid)-contaminated soil

In this study, eight fungal strains were isolated from the rhizosphere of Oenothera picensis Phil., a plant that grows naturally in soil contaminated with metal (loid)s in central Chile. The capacity of the strains to tolerate copper and zinc was evaluated, and their effect on the expression of genes related to metal tolerance in Solanum lycopersicum co-inoculated with arbuscular mycorrhizal fungi. Among the isolates, Lecythophora sp. and Hormonema viticola showed the highest tolerance to Cu (1150 mg kg|−1) and Zn (3200 mg kg−1), respectively. We detected the highest lactic and oxalic acid production lactic and oxalic acid production in Lecythophora sp. against Cu contamination. In contrast, a higher malic, lactic, and citric acid production was detected in H. viticola against Zn contamination. Regarding the expression involved in metal tolerance, we showed that both fungi reduce the expression of the genes MT, PCS, HSP, and NRAMP in S. lycopersicum growing under metal stress. We did not observe a significant positive effect of the co-inoculation with the arbuscular mycorrhizal fungus Rhizophagus irregularis in the relative expression genes in leaves, but a positive impact was detected in roots. The results showed that the co-inoculation of rhizosphere metal-tolerant fungi isolated from metallophyte species and mycorrhizal fungi decreased the expression of metal tolerance genes in S. lycopersicum growing under toxic Cu and Zn levels.

Treatment of cadmium and zinc-contaminated water systems using modified biochar: Contaminant uptake, adsorption ability, and mechanism

Cd and Zn contamination in water occurs frequently that threatens water supply, human health, and food production. MnFeB, a novel absorbent biochar modified using KMnO4 and hematite, was prepared and used for the treatment of Cd2+ and Zn2+solutions. MnFeB exhibits a rough surface structure, large specific surface area, higher total pore volume, massive functional groups, and abundant iron oxide, all of which contribute to higher Cd2+ and Zn2+ adsorption capacity. In single metal systems, maximum Cd2+ and Zn2+ adsorption capacities of MnFeB were 1.88 and 1.79 times higher than those of unmodified biochar (CSB). The maximum Cd2+ and Zn2+ adsorption capacities of MnFeB were 2.73 and 2.65 times higher than CSB in the binary metal system. Key adsorption mechanisms of Cd2+ and Zn2+ by MnFeB included electrostatic interaction, co-precipitation, π-π interaction, complexation, and ion exchange. Thus, MnFeB can be used as a novel absorbent to treat Cd and Zn-polluted water.

Characterization and Risk Assessment of Heavy Metals in Surface Sediments From Jian and Moyang Rivers in Western Guangdong

The river environment is complex and receives a variety of contaminants from numerous sources that are persistent, bioaccumulative, and toxic. The distribution, source, contamination, and ecological risk status of Zn, Pb, Cu, Ni, Cr, and Cd were evaluated in the surface sediments at 45 sites on the Moyang and Jian rivers in Western Guangdong, China. Single pollution indices, including contamination factor (CF) and enrichment factor (EF), revealed that Zn, Pb, Ni, Cu, and Cd showed moderate to significant enrichment. To overcome the limitation of the single element indices, a range of sediment quality indices, including modified contamination index (mCd), pollution index (PI), and modified pollution index (MPI), were utilized to ascertain the sediment quality. The sediment in the study area is deemed to be slightly to extremely polluted. The sediment quality guidelines (SQGs), potential ecological risk index (RI), and modified ecological risk index (MRI) were used to assess possible ecological risks. According to the SQGs, Pb, Ni, and Cu have the potential to induce biological effects. The RI indicated that the sediment poses a low ecological risk. However, the MRI indicated that the ecological risk of the sediment was moderate to very high. The accuracy of the single and multi-element indices and ecological risk assessment were evaluated in the river using the principal component analysis (PCA) and cluster analysis (CA), showing an anthropogenic impact. Results demonstrate the need to pay attention to the ecological environment of small rivers, which are sensitive to their surroundings.

Assessment of Soil Physicochemical Characteristics and As, Cu, Pb and Zn Contamination in Non-Active Mines at the Portuguese Sector of the Iberian Pyrite Belt

This study aimed to evaluate soil physicochemical characteristics (pH, electrical conductivity, organic matter, total N, and extractable P and K), and potentially toxic elements (As, Cu, Pb, and Zn), in non-active mines located in the Portuguese sector of the Iberian Pyrite Belt (IPB). A total of 70 sampling sites were surveyed at Aljustrel and Lousal, in areas already rehabilitated, and at São Domingos, where rehabilitation was only beginning. The soils at São Domingos were very heterogeneous, with extreme values for some properties (e.g., minimum soil pH 2.0 and maximum As concentration, 4382.8 mg kg−1 dry weight basis (DW)). Aljustrel was the site that presented soils with a higher total As, Cu, Pb, and Zn concentration (median values: 441.5, 545.9, 1396.8, and 316.5 mg kg−1 DW, respectively), above the soil quality guidelines values proposed by the Portuguese Environmental Agency (18, 230, 120, and 340 mg kg−1 DW, respectively). A principal component analysis identified the most relevant soil properties to explain the data variance, which were the soil pH and Pb total concentration, followed by Cu and Zn total concentrations, allowing a separation of Aljustrel from the other mines. Pearson correlation coefficients revealed very strong associations between Pb and As, markedly found at higher concentrations in São Domingos, whereas Aljustrel had an elevated concentration of As and Pb, but also of Cu and Zn. It is evident the risk that persists in the Aljustrel mine area, which was not alleviated by the “dig, dump, and cover” techniques that were implemented to rehabilitate the area.

Distribution, risk assessment, and source identification of trace metal pollution along the Babolsar coastal area, Caspian Sea.

The Caspian Sea is exposed to numerous anthropogenic activities such as untreated wastewater discharge and agricultural activities which increased trace metals contamination. The current study was employed to assess the distribution, ecological risk assessment, and source identification of some trace metals in 125 samples of surface sediments and soil from 6 distinctive sections of Babolsar in the coastal line of the Caspian Sea. The sediment quality guidelines (SQGs) and individual risk assessment indices including enrichment factor (EF), geo-accumulation index (Igeo), contamination factor (Cf), and potential risk factor (Er) suggested a hazardous level of Cd and Cr contamination. There was a relatively high level of Pb contamination while other studied trace metals were at a low contamination level. Cumulative risk indices such as modified degree of contamination (mCD), pollution load index (PLI), and the potential ecological risk index (RI) identified that the river, wetland, and farmland sites were more contaminated compared to the Caspian Sea samples which exhibited a moderate level of contamination. The lowest level of contamination was recorded in the coastline and river delta sites. Two analytical methods including Pearson's correlation coefficient and multivariate clustering dendrogram were also applied to identify the potential sources of contamination. The results suggested that wastewaters, nitrogen, and phosphate fertilizers were the main anthropogenic source of Cd, Co, Pb, and Ni while fossil fuels and transportation activities were the predominant sources of anthropogenic Cu, V, and Zn contamination. Further studies about trace metals risk assessment and fractionation could contribute to more effective decisions for reducing the anthropogenic trace metal pollution in the Caspian Sea.

Combining collagen extraction with mineral Zn isotope analyses from a single sample for robust palaeoecological investigations

Collagen extraction from bones or dentine, commonly used for radiocarbon (14C) dating and stable carbon and nitrogen isotope (δ13C and δ15N) analyses, involves the dissolution of the bioapatite of skeletal elements. This fraction is typically disposed of during pretreatment. Here, we test the possibility of utilising this dissolved mineral solution for analysis of the bioapatite zinc isotope composition (δ66Zn). Bioapatite δ66Zn is a novel trophic level indicator similar to collagen δ15N but with isotopic fractionation independent from nitrogen, thus providing additional dietary information. We tested ways to minimise Zn contamination of the dissolved mineral phase during collagen extraction. We then used archaeological bone samples from Ain Difla (Jordan) and Ranis (Germany) to compare δ66Zn values of dissolved bioapatite following our collagen extraction protocol with δ66Zn values from the same sample material dissolved in a metal-free cleanroom. Our results demonstrate that with only minor adjustments to minimise Zn contamination, the dissolved mineral solution from collagen extraction protocols commonly employed for 14C dating and (palaeo)dietary analysis can be used for additional δ66Zn analyses even when collagen extraction does not take place in a cleanroom. Our protocol allows us to gain an additional dietary proxy to complement δ15N trophic level interpretations and perform more robust (palaeo)ecological investigations without further destructive sampling.

Soil degradation and Cu, Cr, Ni, Pb and Zn contamination in dumpsites of humid and semiarid tropical regions in northeastern Brazil.

We investigated soil characteristics and heavy metal content changes in 12 inactive dumpsites in humid and semiarid tropical climates in Northeast Brazil. The metals Cu, Cr, Ni, Pb and Zn in soil samples were determined by atomic absorption spectrophotometry. Other parameters measured include pH, electric conductivity, soil texture, soil organic carbon, total porosity and available P. The soil contents of sand, clay, soil organic carbon, available P and heavy metals, and soil bulk density, total porosity and pH were efficient indicators of soil degradation. We found no influence of current use, soil class or climate on the soil response. The mean concentrations of heavy metals in the dumpsite soils followed the order Zn (49.96mgkg-1) > Cu (38.48mgkg-1) > Pb (24.64mgkg-1) > Cr (21.94mgkg-1) > Ni (7.77mgkg-1). They were 6- to 36-fold higher than the background values for the region and were above the Brazilian guideline values for metals. The four dumpsite soils that showed simultaneous contamination with two or more heavy metals were located in the semiarid region. This challenges the assumption that soil impacts in the semiarid region are minimal due to lower leaching and high evaporation. Soil changes increase with time under activity, size and decommission time of the dumpsite. These data are important for local authorities to establish more effective targeting policies for closure of dumps and control of the spread of contaminants in areas impacted by the disposal of municipal waste.

Occurrence, contamination level and ecological risk assessment of dissolved and particulate trace elements in rivers entering the southwestern Mediterranean Sea

Metal pollution in rivers should not be overlooked before their entry into the sea. However, there are few studies for estimating such contamination in rivers entering the Algerian coastal waters. Semimonthly quantification of dissolved and particulate metals, near the mouths of two industrial-tainted rivers, El Harrach and Mazafran rivers, was carried out during a period of one year. All the trace metals analyzed are originating from anthropogenic sources (EF > 1.5), with higher contamination of dissolved Pb, Cd, Zn and Ni and a slight degree of contamination of particulate Cu and Zn (0 < Igeo < 1). Particulate metals show a stable complex with the particulate phase (e.g. 2 < LogKd < 6). The risk assessment results indicate that particulate Pb and Zn have a 33% likelihood of toxicity for adverse biological effects. A significant toxicity effect (ΣTUi >4) of the combined particulate metals (Pb, Cd, Cu, Zn, Cr, Ni and As) was primarily due to the higher particulate Cd, Zn, and Cr availability.

Distribution pattern of Pb and Zn contamination in rivers near industrial zone in Aceh, Indonesia, revealed by principal component analysis (PCA)

The research aims to evaluate the pollution of Pb and Zn in water, sediment, and Faunus ater samples collected from Krueng Balee (KB) and Kreung Reuleung (KR) Rivers, Aceh, Indonesia. The samples were collected at the upstream, midstream, and downstream of each river and analyzed using Atomic Absorption Spectrophotometry (AAS). The distribution of Pb and Zn pollution was analyzed using Principal Component Analysis (PCA). Our investigation revealed that the presence of Pb and Zn is still safe for water and sediment samples. Nevertheless, Pb and Zn contamination found in F. ater samples had exceeded the national safety limit for food. PCA analysis revealed correlations between samples suggesting the roles of physical and chemical properties of the river in the pollutant retainment. The analysis also indicated the possible antagonism between Pb and Zn accumulation in F. ater which has never been reported previously. We suggest routine monitoring of Pb and Zn concentrations. The role of the surrounding industry in the Pb and Zn pollution should be further studied.

Comparative Spatial Assessment of Trace Metal(loid) Pollution in the Sediments of the Lower Olifants River Basin in South Africa

Globally, many freshwater ecosystems are facing chemical pollution from both natural and anthropogenic sources. The Olifants River Basin in South Africa is experiencing degradation due to mining, industrial, agricultural, and domestic activities. The impacts of these activities coupled with climate change is likely to shift the hydrological cycle that may increase accumulation of toxic chemicals in the sediments. The aim of the study was to assess the contamination of As, Cr, Cu, Fe, Mn, Ni, Pb, and Zn in the sediments collected at the upstream, midstream and downstream of four rivers of the Lower Olifants River Basin; the Blyde, Mohalpitsi, Ga-Selati, and Steelpoort rivers. The highest concentrations of most of the trace metal (loid)s assessed were from the Steelpoort River followed by the Blyde River. Significant differences in metal concentrations were found across study sites and rivers. The overall assessment of the sub-catchment, which is characterised mainly by mining and agricultural activities shows significantly elevated levels of As, Cr, Mn, and Ni in the sediments and may cause secondary pollution in the water. Using enrichment factor (EF) and geo-accumulation index (Igeo), some of the sediments were severely enriched and extremely contaminated respectively with As, Cr, and Ni. This may risk the lives of aquatic biota and humans, especially rural communities that rely on these rivers for drinking water. The findings provide baseline information for effective management control of metal(loid) pollution in the Olifants River Basin.

Mobility, bioaccessibility, pollution assessment and risk characterization of potentially toxic metals in the urban soil of Lahore, Pakistan.

The present study is based on the measurement of potentially toxic metal contents employing various extraction methodologies aimed at the evaluation of their mobility, bioaccessibility and bioavailability in the urban soil (n = 56) of Lahore, Pakistan. Selected metal levels in the soil were quantified using flame atomic absorption spectrometry. On the average basis, aqua regia and glycine extracts revealed comparatively higher contents for most of the metals; average concentrations of Fe, Mn, Zn, Pb, Cu, Cr, Co and Cd were found at 1566, 451.1, 114.8, 52.84, 39.15, 24.82, 12.59 and 3.953mg/kg in aqua regia extract, while in glycine extract the metal levels were found at 579.6, 174.2, 74.72, 49.74, 19.28, 7.103, 4.692 and 3.357mg/kg, respectively. However, Cd, Pb, Cu and Zn showed significantly higher mobility and bioavailability in the soil, while Co, Fe and Mn were least mobile/bioavailable. The pollution index was assessed in terms of enrichment factor and modified degree of contamination which revealed severe to significant contamination and anthropogenic enrichment of Cd, Pb, Cu and Zn. Multivariate analysis showed mostly anthropogenic contributions for Zn-Cu-Cr-Pb-Cd. Health risk assessment revealed relatively higher exposure of the metals through ingestion, while only minor contributions were noted for inhalation and dermal contact. Hazard quotient index was within the safe limit (< 1.0) in all soil extractions, thereby indicating no significant non-carcinogenic health risks. The incremental lifetime cancer risk for Cr (4.1E-06) through ingestion was comparatively higher than the safe limit which showed significant lifetime cancer risk to the local population.

Wood vinegar facilitated growth and Cd/Zn phytoextraction of Sedum alfredii Hance by improving rhizosphere chemical properties and regulating bacterial community

Soil Cd and Zn contamination has become a serious environmental problem. This work explored the performance of wood vinegar (WV) in enhancing the phytoextraction of Cd/Zn by hyperaccumulator Sedum alfredii Hance. Rhizosphere chemical properties, enzyme activities and bacterial community were analyzed to determine the mechanisms of metal accumulation in this process. Results demonstrated that, after 120 days growth, different times dilution of WV increased the shoot biomass of S. alfredii by 85.2%–148%. In addition, WV application significantly increased soil available Cd and Zn by lowing soil pH, which facilitated plant uptake. The optimal Cd and Zn phytoextraction occurred from the 100 times diluted WV (D100), which increased the Cd and Zn extraction by 188% and 164%, compared to CK. The 100 and 50 times diluted WV significantly increased soil total and available carbon, nitrogen and phosphorus, and enhancing enzyme activities of urease, acid phosphatase, invertase and protease by 10.1–21.4%, 29.1–42.7%,12.2–38.3% and 26.8–85.7%, respectively, compared to CK. High-throughput sequencing revealed that the D 100 significantly increased the bacterial diversity compared to CK. Soil bacterial compositions at phylum, family and genera level were changed by WV addition. Compared to CK, WV application increased the relative abundances of genus with plant growth promotion and metal mobilization function such as, Bacillus, Gemmatimonas, Streptomyces, Sphingomonas and Polycyclovorans, which was positively correlated to biomass, Cd/Zn concentrations and extractions by S. alfredii. Structural equation modeling analysis showed that, soil chemical properties, enzyme activities and bacterial abundance directly or indirectly contributed to the biomass promotion, Cd, and Zn extraction by S. alfredii. To sum up, WV improved phytoextraction efficiency by enhancing plant growth, Cd and Zn extraction and increasing soil nutrients, enzyme activities, and modifying bacterial community.

Metal enrichment in sediments and bioaccumulation in edible bivalve Saccostrea cucullata from mudflats of a tropical estuary, India: a study to investigate toxicity and consumption suitability

Mudflat sediment cores from lower (C-1), middle (C-2), and lower regions of upper (C-3) Chapora Estuary were investigated for grain size composition, total organic carbon, total and bioavailable Fe, Mn, Cu, Co, Ni, and Zn to assess metal contamination. Accumulation of metals by Saccostrea cucullata was studied to understand metal toxicity. In core C-1, Fe, Mn, Cu, Co, Ni, and Zn showed an average concentration of 1.73%, 648ppm, 12ppm, 12ppm, 16ppm, and 25ppm, respectively, while core C-2 revealed their average concentration as 1.34%, 709ppm, 10ppm, 11ppm, 13ppm, and 28ppm respectively. In core C-3, an average concentration of Fe, Mn, Cu, Co, Ni, and Zn was 1.72%, 907ppm, 14ppm, 13ppm, 18ppm, and 31ppm respectively. Metals in sediments varied within the estuary due to hydrodynamics, discrepancies in metal sources and sand mining-induced remobilization of metals. Correlation and principal component analysis revealed Fe oxides as the key regulator of trace metal distribution in sediments along with clay and total organic carbon. Enrichment factor (EF) and geo-accumulation index (Igeo) showed more or less moderate contamination of Mn in core C-3. Also, the potential contamination index (PCI) indicated moderate contamination of Mn in core C-3 using the shale value as background concentration, whereas the application of upper crustal value revealed moderate contamination of Fe, Mn, Cu, Co, and Ni in core C-1, Mn, Co, and Ni in core C-2 and of Cu, Co, and Ni in core C-3. Mn was severely to very severely contaminated in core C-3. The mean probable effect level quotient and mean effect range median quotient showed medium to low-level contamination of Cu, Ni, and Zn. Metals were considerably allied to Fe-Mn oxide and organic/sulphide fractions which revealed their bioavailability. Mn was 36% in labile form (lower estuary) and indicated a high risk to biota. Mn, Ni, and Zn in Saccostrea cucullata exceeded the permissible limit and suggested toxicity and non-suitability for human consumption.

Characteristics, source apportionment and health risk assessment of heavy metals in urban road dust of the Pearl River Delta, South China

To investigate the characteristics of heavy metals (As, Cd, Cr, Cu, Pb, Hg, Ni and Zn) in urban road dust from different cities and functional areas in the Pearl River Delta (PRD), South China, a total of 294 dust samples were analyzed. The contamination characteristics and health risk of heavy metals in the dust were assessed, their chemical speciation were distinguished, and their sources were identified by the correlations, cluster and principal component analysis (PCA). The mean concentrations of As (15.89 mg/kg), Cd (1.59 mg/kg), Cr (143.75 mg/kg), Cu (184.42 mg/kg), Pb (114.82 mg/kg), Hg (0.11 mg/kg), Ni (41.53 mg/kg) and Zn (645.94 mg/kg) in urban road dust were in high or moderate levels compare with other previous researches. In this case, the contamination of Cr, Cu, Ni and Zn in the industrial area (IA) and the contamination of Cd and Hg in the commercial area (CA) were significantly higher relative to other functional areas (P < 0.05), and the contamination of heavy metals in Foshan City was significantly higher than other cities (P < 0.01). The order of mobility of the heavy metals with higher concentration in urban road dust of the Pearl River Delta declined in the following order: Zn, Ni, Cu, Pb and Cr. Statistical analysis result showed the contaminated heavy metals in urban road dust were mainly contributed by industrial activities, traffic activities and building pollution. There were no significant carcinogenic and noncarcinogenic risks for adults, children however showed significant noncarcinogenic effect caused by As and Cr in partial points, albeit with low contamination level of the two metals. The ingestion was a principal pathway for heavy metals via urban road dust to exposure population. More protection measures should be considered to reduce children’s exposure to the dust, especially in the CA and IA.

Coastal macrophytes as bioindicators of trace metals in the Asia's largest lagoon ecosystem

Coastal trace metal contamination is of serious concern and the role of new bioindicator species in monitoring of trace metals is essential. The present study quantified the concentration of trace metals (Co, Cr, Cu, Mn, Ni, Pb and Zn) in the sediment and the macrophytes of Chilika lagoon, India, and investigated the bioindicator potential of the seagrasses, saltmarshes and macroalgae. The Igeo values for sediment indicated significant contamination of Cu and Zn in seagrass, Cu, Ni and Zn in saltmarsh and moderate contamination of Cr, Cu and Pb in macroalgal ecosystems. In general, the Bio-Sediment Accumulation Factor (BSAF) indicated that the macrophytes accumulated higher concentration of Mn and Ni from the sediments. The high concentration of trace metals in the sediment of the three macrophytes ecosystems did not result in higher accumulation of the same metals in the tissues of the respective macrophytes suggesting metal specific and species-specific behaviour.

River morphology redistributes potentially toxic elements in acid mine drainage-impacted river sediments: Evidence, causes, and implications

River morphology plays a vital role in the transport of substance within them. However, our understanding of how natural and artificial morphologies redistribute different potentially toxic elements in acid mine drainage (AMD)-contaminated rivers remains poor. In this study, we linked morphological river features and physicochemical sediment characteristics to trace the redistribution of various potentially toxic elements and elucidate their implications for remediating rivers prone to AMD pollution. A dense network of sediment/soil samples was collected from different river morphological units, such as channels, dam reservoirs, pools, floodplain sandbars and wetlands in an AMD-impacted river. The analyses showed that the contaminant levels in channel generally decreased downstream from the headwater mine site, however, local fluctuations in certain areas were observed due to the trapping effect of various dams along the river. The As and Pb concentrations were higher at floodplain sandbars, while river channels exhibited higher Cd and Zn contamination. The concentrations and geochemical fractions of As, Cd, Cu, Pb and Zn in sediment/soil cores from sandbar and river channel also varied. Additionally, structural equation modeling analysis indicated that spatial variations in contaminant distributions were directly affected by physicochemical properties (such as the soil/sediment Fe, Zn, and S concentrations, and pH), which are indirectly affected by river morphology. The diverse morphology of the river redistributed AMD-derived contaminants and could be used to identify contamination hotspots. Our analyses suggested that the feasibility and efficiency of previously proposed countermeasures varied for contaminants in different geomorphological units. In river channels, As uptake from sediments by aquatic plants may be less efficient than Cd, Cu, and Zn uptake due to its lower bioavailability. Moreover, vegetation prevented contaminant enriched soil particle erosion more than it aided in the phytoremediation of As- and Pb-contaminated sandbars. Thus the finding of this study provide a theoretical foundation for further studies on the transport and storage of AMD-derived contaminants in similar rivers, along with the development of targeted remediation methods.

Historical trends in atmospheric metal(loid) contamination in North China over the past half-millennium reconstructed from subalpine lake sediment

Trace metal (loid) contamination in the atmosphere is widely monitored, but there is a gap in understanding its long-term patterns, especially in North China, which is currently a global contamination hotspot mainly caused by heavy industry emissions and coal combustion. Herein, historical trends of atmospheric As, Cd, Cr, Cu, Hg, Ni, Pb and Zn contamination in North China over the past ∼500 years are comparatively studied with sediment cores from two subalpine lakes (Gonghai and Muhai). Arsenic, Pb, Cd and Hg were main pollutants according to Pb isotopes and enrichment factors. Mercury contamination has increased continuously since the late 1800s and increasing As, Pb and Cd contamination started in the 1950s in Gonghai. In contrast, the contamination in Muhai lagged two decades for As, Cd and Pb and a half-century for Hg behind that in Gonghai, although the trends were similar. This contamination lag was attributed to the low sensitivity of Muhai sediment to early weak atmospheric metal contamination under 2.1-fold higher detrital sedimentation. As, Pb and Cd contamination has intensified since the 1980s, and the metals showed similar sedimentary fluxes in the cores. However, sedimentary fluxes of Hg contamination were 3.4-fold higher in Gonghai than in Muhai due to combination with organic matter. No obvious Cr, Cu and Ni contamination in the cores was mainly because of the low atmospheric deposition from anthropogenic sources relative to detrital input, although some of their atmospheric emissions were higher than those of As, Cd and Hg. Atmospheric As, Pb and Cd contamination was mainly from domestic sources of coal combustion and nonferrous smelting. Mercury contamination was mainly from global and Asian sources in the first half of the 20th century, and domestic emissions gradually dominated Hg contamination after the mid-1900s.

Anthropogenic Zn contamination dispersion in Sepetiba Bay evidenced by Zn isotopes

Sedimentary processes in coastal environments play a key role in the spatial dispersion of metal contaminants, including Zn. Combining Zn stable isotope signatures (δ66Zn) with traditional proxies of sedimentary sources and dispersal and post-depositional processes is a promising approach to understanding Zn anthropogenic dynamics in coastal systems that remains untested. To this end, we coupled geochemical and isotope tools to infer sedimentary contributions on Zn fate and behavior in surface sediments of Sepetiba bay, a tropical lagoon in Rio de Janeiro state chronically contaminated by an old stake of electroplating wastes Zn-enrich. Our results show high variability in δ66Zn values (0.43‰ to 0.89‰) and Zn enrichment factors (1 to 23-fold), evidencing a gradient in mixing sedimentary sources. The biplot δ66Zn versus 1/[Zn] highlights that the Zn isotope variability of most samples fell within a mixing source trend involving natural Zn (+0.29‰, 67 mg.kg-1) and anthropogenic Zn (+0.89‰, 3,440 mg.kg-1), the latter attributed to the Sepetiba bay’s historical Zn metallurgical contamination. Based on the isotope mixing model and geochemical proxies (e.g., Ti/Al ratio), we calculated that Zn excess in the Sepetiba Bay varies from 42% to 98%. The Zn enrichment distribution across the bay confirmed anthropogenic Zn dispersal from the Saco de Engenho, mainly controlled by the clock direction water current. Sediments mineralogical composition and correlations between Zn isotope and Al concentrations indicate that the high content of anthropogenic Zn is associated with silt and clay sediment particles composed of gibbsite and clay minerals such as kaolinite and organic matter. Our findings demonstrate that combining Zn isotope ratios with other geochemical proxies may help pinpoint Zn anthropogenic origins and behavior as well as track its dispersion in the land-sea continuum. In this case, this approach provides more accurate results on Zn contamination dispersion in the Sepetiba Bay and avoids possible misleading interpretations concerning anthropogenic Zn origins at low Zn concentration levels.

Effects of Cu and Zn contamination on chicken manure-based bioponics: Nitrogen recovery, bioaccumulation, microbial community, and health risk assessment

In bioponics, although chicken manure is an efficient substrate for vegetable production and nitrogen recovery, it is often contaminated with high Cu and Zn levels, which could potentially cause bioaccumulation in plants and pose health risks. The objectives of this study were to assess nitrogen recovery in lettuce- and pak choi-based bioponics with Cu (50–150 mg/kg) and Zn (200–600 mg/kg) supplementation, as well as their bioaccumulation in plants, root microbial community, and health risk assessment. The supplementation of Cu and Zn did not affect nitrogen concentrations and plant growth (p > 0.05) but reduced nitrogen use efficiency. Pak choi showed higher Cu and Zn bioconcentration factors than lettuce. Bacterial genera Ruminiclostridium and WD2101_soil_group in lettuce roots and Mesorhizobium in pak choi roots from Cu and Zn supplemented conditions were significantly higher (p < 0.05) than controls, suggesting microbial biomarkers in plant roots from Cu and Zn exposure bioponics depended on plant type. Health risk assessment herein revealed that consumption of bioponic vegetables with Cu and Zn contamination does not pose long-term health risks (hazard index <1) to children or adults, according to the US EPA. This study suggested that vegetable produced from chicken manure-based bioponics has low health risk in terms of Cu and Zn bioaccumulation and could be applied in commercial-scale system for nutrient recovery from organic waste to vegetable production; however, health risk from other heavy metals and xenobiotic compounds must be addressed.

Assessment of heavy metals should be performed before the development of the selenium-rich soil: A case study in China

The use of selenium (Se)-rich soils in China is an effective method for rural revitalization, but assessment of heavy metals is essential prior to the development of Se-rich soils. This study was focused on the Jiangjin district, a typical Se-rich area located in Sichuan Basin of China, to investigate contamination, influencing factors, and sources of As, Cr, Cu, Cd, Ni, Pb, Sb, and Zn based on 156 topsoil samples. This study analyzed and compared the enrichment factor (EF), Nemerow index (PN), geographical information system (GIS), and positive matrix factorization (PMF). Results demonstrate that the average values of As, Cu, Cd, Sb, and Zn in topsoil were higher than the soil background values of western Chongqing by approximately 1.75, 1.11, 1.27, 1.71, and 2.58 times, respectively, indicating that some heavy metals have been enriched in the soils. The polluted areas of As, Cu, Cd, and Zn in topsoil were mainly distributed in the northern and central Jiangjin district, whereas high-Sb soils were located in the southeast. The Cr, Cu, Cd, Pb, and Sb were concentrated in Se-rich soils, indicating that heavy metals pollution should be carefully considered for the utilization of Se-rich soils. Four potential sources of heavy metals were found in this study area: 1) the parent materials (Cr, Ni, Cu); 2) industrial activities with high coal consumption (As); 3) mechanical and chemical industrial activities (Zn, Sb); and 4) transportation and agricultural activities (Pb, Cd). These observations provide a scientific basis for the development, utilization, and protection of Se-rich soil resources.