Cd Loading Research Articles

Genetic Regulation Mechanism of Cadmium Accumulation and Its Utilization in Rice Breeding.

Cadmium (Cd) is a heavy metal whose pollution in rice fields leads to varying degrees of Cd accumulation in rice. Furthermore, the long-term consumption of Cd-contaminated rice is harmful to human health. Therefore, it is of great theoretical significance and application value to clarify the genetic regulation mechanism of Cd accumulation in rice and cultivate rice varieties with low Cd accumulation for the safe use of Cd-contaminated soils. This review summarizes the effects of Cd on rice growth, yield, and quality; the physiological and molecular mechanisms of Cd absorption in the roots, loading, and transport of Cd in the xylem, the distribution of Cd in nodes, redistribution of Cd in leaves, and accumulation of Cd in the grains; the regulation mechanism of the Cd stress response; and the breeding of rice with low Cd accumulation. Future directions on the genetic regulation of Cd in rice and application are also discussed. This review provides a theoretical basis for studies exploring the genetic regulation of Cd stress in rice. It also offers a basis for formulating effective strategies to reduce the Cd content in rice.

Water quality of Bomadi Creek in the Niger Delta of Nigeria: assessment of some physicochemical properties, metal concentrations, and water quality index

In this study, some physicochemical properties, concentrations of metals (Pb, Cd, Cu, Zn, Fe, and Mn), and the overall water quality from Bomadi Creek in the Niger Delta of Nigeria were assessed over two seasons. Water samples were collected from designated areas along the course of the river and were prepared for analysis by standard procedures. The ranges of the mean values for some water quality indicators were found to be as follows: pH: 7.40–8.17, turbidity (NTU): 20.5–42.3, total dissolved solids (mg L−1): 27.5–44.7, total suspended solids (mg L−1): 34.1–61.7, dissolved oxygen (mg L−1): 3.07–6.53, biochemical oxygen demand (mg L−1): 0.13–2.77, total hardness (mg L−1): 28.3–60.0, and nitrate (mg L−1): 0.37–0.92. Only the turbidity values exceeded the permissible limit of 5 NTU. The concentration ranges (mg L−1) for the six metal ions determined were: Pb: 0.01–0.02, Cd: 0.01–0.03, Zn: 0.1–0.3, Cu: 0.03–0.07, Fe: 0.6–0.9, and Mn: 0.01–0.05. There were no significant variations in many of the locations between the wet and dry seasons. The comprehensive pollution index values indicated severe pollution of the Creek, with Cd, Fe, and turbidity, identified as the major contributors to the deteriorated water quality. The sources of high loads of Cd, Fe, and turbidity in this river system include discharges from oil production activities, speed boats, illegal bunkering, and domestic waste dumps. Principal component and cluster analysis were used to establish relationships between the various parameters and sites. The risk assessment indicated adverse non-carcinogenic and carcinogenic risks arising from human consumption of the water. The risk is higher for children than adults. Therefore, the Bomadi water is considered unsuitable for drinking and other domestic purposes, and remediation is required.

Investigation of Cd(II) sorption by mackinawite (FeS) under anoxic conditions

Mackinawite (FeS) was investigated for cadmium ion (Cd(II)) sorption under anoxic conditions. At the surface loading of Cd(II) (i.e., [Cd(II)]0/[FeS]0) ≤ 5 mmol/g, FeS quantitatively immobilized Cd(II). Adsorption and CdS precipitation were responsible for Cd(II) uptake, with their relative importance depending on [Cd(II)]0/[FeS]0. At pH 5.5–6.0, adsorption was more important when [Cd(II)]0/[FeS]0 ≤ 0.05 mmol/g. According to energy dispersive X-ray spectroscopy, Cd(II) exhibited strong spatial correlations with S and Cl. While Cd-S correlations corresponded to CdS precipitation and/or the surface complexation of Cd(II) with sulfhydryl functional sites, Cd–Cl correlations indicated the presence of chloride-complexed Cd(II). Given the strong correlations of both pairs, the adsorbed Cd(II) was likely present in chlorosulfide forms (e.g., ≡FeS–Cd(II)–Cl). When [Cd(II)]0/[FeS]0 exceeded 0.05 mmol/g, CdS precipitation became more important. X-ray diffraction, transmission electron microscopy, and selected area electron diffraction revealed the formation of hawleyite (cubic CdS) at higher surface loadings. The Fe(II) species liberated during CdS precipitation were resorbed through adsorption at acidic pH and the formation of Fe (oxyhydr)oxides at neutral to basic pH. Given the greater stability of CdS than adsorbed Cd(II), the prevalence of the former suggests that FeS can serve as an effective reagent to remedy Cd(II) contamination under anoxic conditions. Due to its ubiquitous presence, FeS may also control the environmental fate and mobility of Cd(II) in sulfidic sediments.

Structural-functional aberrations of erythrocytes in the northern red-backed vole (Clethrionomys rutilus Pallas, 1779) that inhabits the zone of influence of the copper smelter (the Middle Ural).

Red blood cell parameters were assessed in a natural population of the northern red-backed vole (Clethrionomys rutilus Pallas, 1779) in the zone of influence of the Kirovgrad Copper Smelter along a gradient of pollution by heavy metals (Cu, Zn, Cd, and Pb) at three catching sites (polluted [Imp] and controls [Bg-1, and Bg-2]). The difference of the smelter area (Imp group of voles) from both background groups (Bg-1 and Bg-2) was proven by means of a set of 13 parameters in univariate and multivariate analyses. Among the detected erythrocyte disturbances, we noted the following: a decrease in activities of Na+,K+-ATPase and antioxidant enzymes (SOD, GSH-Px, and CAT); an increase in the concentration of lipid peroxidation products, in osmotic fragility, and in intravascular hemolysis; interruption of carbohydrate metabolism; and lowered oxygen-carrying capacity. A higher load of Cd (p = 0.0009) and possibly Pb (p = 0.054) in the Imp animals was confirmed by quantitation of heavy metals in the liver. Most erythrocyte parameters (11 out of 13) covaried with individual Cd load by obeying a semilogarithmic dependence; such a relation was not found for Cu, Zn, and Pb. A decrease in the growth rate of structural and functional erythrocyte aberrations ("resistance improvement") with increasing cadmium load is probably due to compensatory enhancement of the synthesis of metallothioneins in the liver and kidneys and hence a greater proportion of Cd bound to metallothioneins. Problems of differences/similarities in Cd-associated reactivity among the animals are discussed too, taking into account the catching sites (polluted [Imp] and controls [Bg-1, and Bg-2]) and reproductive-age (i.e., immature underyearlings, mature underyearlings, and individuals that overwintered). The persistence of differences in erythrocyte status observed by us between the Imp and background groups after normalization to Cd load may be due to the action of other (unexamined) adverse factors and calls for further ecotoxicological studies.

Integration of Transcriptome and Metabolome Analyses Reveals the Mechanistic Basis for Cadmium Accumulation in Maize.

Cadmium (Cd) pollution in soil has become a major environmental issue worldwide. However, the underlying molecular mechanism of low grain-Cd accumulation (GCA) in maize is still largely unknown. Herein, we report the mechanistic basis for low GCA in maize by a multiomics approach. The low GCA genotype L63 showed normal vacuolar formation and a lower capacity of xylem loading of Cd than the high-accumulator L42 under Cd stress. Transcriptomic sequencing identified 84 low-GCA-associated genes which are mainly involved in the S-adenosylmethionine (SAM) cycle, metal transport, and vacuolar sequestration. A metabolome analysis revealed that L63 plants had a more active SAM cycle and a greater capacity for terpenoid synthesis and phenylalanine metabolism than L42. Combining the analysis of transcriptome and metabolome characterized several genes as key genes involved in the determination of Cd accumulation. Our study identifies a mechanistic basis for low Cd accumulation in maize grains and provides candidate genes for genetic improvement of crops.

Trends in hepatic cadmium concentrations in marine bird species from the Canadian Arctic

Cadmium (Cd) is a trace element of toxicological concern that has been monitored in marine birds inhabiting the Canadian Arctic since 1975. Despite nearly 50 years of monitoring, research to date has largely evaluated single species, locations, or time points, and there is as of yet no holistic overview that jointly considers all available Cd data. We addressed this information gap by combining and analyzing most of the existing data on hepatic Cd concentrations in marine birds from the Canadian Arctic. Using data collected between 1975 and 2018 from eight seabird species from 12 Arctic breeding colonies, we examined temporal, spatial, and interspecific variation in hepatic Cd levels, and we evaluated possible drivers of marine bird Cd loads. Hepatic Cd concentrations ranged from 1.6 to 124 μg/g dry weight across species, and were highest in thick-billed murres (Uria lomvia) and king eiders (Somateria spectabilis), and lowest in black guillemots (Cepphus grylle), black-legged kittiwakes (Rissa tridactyla), and long-tailed ducks (Clangula hyemalis). All sites with multiple years of data showed interannual fluctuations in Cd, which were correlated with the North Atlantic Oscillation (NAO) index and with the previous year's June sea ice coverage, where marine birds exhibited higher Cd concentrations in positive NAO years and following years with lower sea ice coverage. Climate change is likely to shift the NAO to being more negative and to reduce sea ice coverage, and our results thus identify various ways by which climate change could alter Cd concentrations in marine birds in the Canadian Arctic. Understanding variations in marine bird contaminant burdens, and how these may be alters by other stressors such as climate change, is important for long-term marine bird conservation efforts.

Comparison of Heavy Metal Deposition in Edible Muscles of Nile Tilapia (Oreochromis niloticus) and Crucian Carp (Carassius carassius) in Lake Ziway, Ethiopia

Lake Ziway is a fresh Lake playing an important role in the lives of many people in the region. These may make the Lake Ziway to receive various kinds of pollutants enriched with heavy metals through different mechanism. The purpose this study was to conducted analysis of heavy metal accumulation in the edible muscles of Nile Tilapia and curican carp fish species which are among the most common types of fish consumed by the local people and found widespread in the lake Ziway. The analysis of heavy metals including Cd, Pb, Ni, Cu, and Zn were conducted for water samples and from edible muscles of two fish species including Nile tilapia and Curician carp. Data were subjected to statistical analysis. The result of physicochemical properties of the water samples from the study sites in the Ziway lake indicated no significance differences in temperature and pH among the three sites. However, significance differences were observed in other parameters like electrical conductivity (EC), total dissolved solids (TDS) and suspended solids (SS). Site 1 has demonstrated significantly the highest EC (1245.12±5.34 µS/cm), TDS (756.10±1.50mg/L) and SS (24.5±0.15 mg/L). The concentrations of heavy metals in water samples from Lake Ziway at site 1 (close to floriculture industry) presented significantly the highest amount of all the tested metals including Cd (2.71mg/L), Cu (4.88mg/L), Ni (8.10mg/L), Pb (6.06mg/L) and Zn (12.12mg/L). Significantly the highest load of metal accumulations in fish muscles were observed at site 1 (near floriculture industry) in Nile tilapia with load of Zn(100.37), Cd (6.05), Ni(4.70), Pb (5.76) and Cu (47.54)mg/L. The comparison of heavy metal accumulation across lake sites in fish muscle samples indicated that the highest accumulations were obtained for Cu and Zn; small amounts of Cd, Ni & Pb.

Dual-function DEFENSIN 8 mediates phloem cadmium unloading and accumulation in rice grains.

Grain cadmium (Cd) is translocated from source to sink tissues exclusively via phloem, though the phloem Cd unloading transporter has not been identified yet. Here, we isolated and functionally characterized a defensin-like gene DEFENSIN 8 (DEF8) highly expressed in rice (Oryza sativa) grains and induced by Cd exposure in seedling roots. Histochemical analysis and subcellular localization detected DEF8 expression preferentially in pericycle cells and phloem of seedling roots, as well as in phloem of grain vasculatures. Further analysis demonstrated that DEF8 is secreted into extracellular spaces possibly by vesicle trafficking. DEF8 bound to Cd in vitro, and Cd efflux from protoplasts as well as loading into xylem vessels decreased in the def8 mutant seedlings compared with the wild type. At maturity, significantly less Cd accumulation was observed in the mutant grains. These results suggest that DEF8 is a dual function protein that facilitates Cd loading into xylem and unloading from phloem, thus mediating Cd translocation from roots to shoots and further allocation to grains, representing a phloem Cd unloading regulator. Moreover, essential mineral nutrient accumulation as well as important agronomic traits were not affected in the def8 mutants, suggesting DEF8 is an ideal target for breeding low grain Cd rice.

Colloid-facilitated mobilization of cadmium: Comparison of spring freeze-thaw event and autumn freeze-thaw event

Freeze-thaw action has the potential to facilitate the mobilization of colloid-associated contaminants in soil. However, the differences in colloid-associated contaminants following autumn freeze-thaw (AFT) events and spring freeze-thaw (SFT) events remain unclear. In this study, the potential influence mechanisms of AFT and SFT on both the generation and migration of colloids and colloid-associated cadmium (Cd) in soil were explored. Higher aggregate stabilities were found in soils after AFT compared with after SFT. After SFT, lower Cd concentrations were found in soil aggregates of 0.25–0.50 mm and <0.106 mm and higher concentrations were found in 0.106–0.25 mm aggregates. Moreover, SFT generated higher amounts of colloidal Cd than AFT, while AFT increased the total Cd concentration in leachates. Additionally, compared with SFT, AFT led to higher Cd concentrations in dissolved and colloid-associated forms in leachates. These findings demonstrate that higher amounts of colloid and fewer loadings of Cd in colloids in Cd contaminated soil can be found after SFT events. Thus, to better understand the environmental risk of contaminants in areas subject to seasonal freeze-thaw cycles, the differences between freeze-thaw processes in spring and autumn should be considered.

Cosmopolitan cadmium hyperaccumulator Solanum nigrum: Exploring cadmium uptake, transport and physiological mechanisms of accumulation in different ecotypes as a way of enhancing its hyperaccumulative capacity

The non-essential element cadmium (Cd) is one of the most problematic priority soil pollutants due to multitude of pollution sources, mobility in the environment and high toxicity to all living organisms. This strongly limits also the number and occurrence of species – Cd hyperaccumulators to be used for soil phytoremediation. However, efficient Cd hyperaccumulator Solanum nigrum L. appeared to commonly occur worldwide as a representative of Solanum nigrum complex of a great taxonomic diversity. This led to the idea that the search among different ecotypes of Solanum nigrum L. may result in the identifying the most efficient Cd hyperaccumulator without applying to soil any additional measures such as chemical ligands. In this first pioneering comparative study, three randomly selected ecotypes of S. nigrum L. ssp. nigrum from Shenyang (SY) and Hanzhong (HZ) in China, and Kyoto (KY) in Japan were used in pot experiments at soil treatments from 0 to 50 mg Cd kg−1. The Cd accumulation capacity appeared to represent KY > HZ > SY range, KY ecotype accumulating up to 73%, and HZ ecotype up to 67% bigger total Cd load than SY ecotype. At Cd content in soil up to 10 mg kg−1, no significant effect on the all ecotype biomass, photosynthetic activities, contents of first line defense antioxidant enzymes (CAT, SOD, GPX), and scavenging antioxidants ASA, GSH, was observed. At Cd in soil>10 mg kg−1all these parameters showed decreasing, and cell damage indicator MDA increasing trend, however total accumulated Cd load further increased up to 30 mg kg Cd in soil in all ecotypes in the same KY > HZ > SY sequence. The study proved the great potential of enhancing Cd accumulation capacity of S. nigrum species by selecting the most efficient ecotypes among commonly occurring representatives of S. nigrum complex worldwide. Moreover, these first comparative experiments convinced that the cosmopolitan character and great variety of species/subspecies belonging to Solanum nigrum complex all over the world opens the new area for successful soil phytoremediation with the use of the most appropriate eco/genotypes of S. nigtum as a tool for the best Cd-contaminated soil management practice.

Iron(II)-activated phase transformation of Cd-bearing ferrihydrite: Implications for cadmium mobility and fate under anaerobic conditions

The factors and mechanisms affecting the fate of the associated Cd during the Fe(II)-activated Cd-bearing ferrihydrite transformation remain poorly understood. Herein we have conducted a series of batch reactions containing ferrihydrite with diverse pH values and initial Fe(II) and Cd concentrations coupled with chemical analyses and spectroscopic examination on the transformation products to probe the mechanisms of the Cd partitioning and the processes of Fe(II)-activated Cd-bearing ferrihydrite transformation under anaerobic conditions. Chemical analyses, Fourier transform infrared spectroscopy (FTIR), and powder X-ray diffraction (PXRD) results show that the initial Fe(II) and Cd concentrations as well as pH values all have significant effects on the rates and pathways of ferrihydrite transformation. Increasing Cd loading enhances the inhibition of the Fe(II)-activated ferrihydrite transformation rates. High Cd loading alters the Fe(II)-activated ferrihydrite transformation pathways by hindering the recrystallization of both ferrihydrite to more stable iron minerals and the newly formed lepidocrocite to goethite. Chemical analyses show that the release of Cd to solutions during ferrihydrite transformation is accompanied by a reduction in the 0.4 M HCl extractable Cd fraction and that a significant amount of the released Cd is transformed to a 0.4 M HCl unextractable form. Moreover, enhanced Cd release during the Fe(II)-activated ferrihydrite transformation is observed by reducing the pH value or increasing the initial Cd concentration. Results from synchrotron X-ray absorption spectroscopy (XAS) confirm that the majority of the 0.4 M HCl unextractable Cd form is associated with structural incorporation into the recrystallized iron (hydr)oxides via isomorphous substitution for Fe(III). These findings not only provide molecular-level understanding on the behavior of Cd under natural anoxic environments, but also are useful in predicting the geochemical cycling of Cd and developing long-term Cd contaminant management strategies.

Effect of Cd on Pyrolysis Velocity and Deoxygenation Characteristics of Rice Straw: Analogized with Cd-Impregnated Representative Biomass Components.

The pyrolysis characteristics of cadmium (Cd)-impregnated cellulose, hemicellulose, and lignin were studied to elucidate the pyrolysis velocity and deoxygenation characteristics of Cd-contaminated rice straw. The results show that Cd significantly affects the pyrolysis characteristics of a single biomass component. With a heating rate of 5 °C·min−1 and a Cd loading of 5%, the initial pyrolysis temperature of cellulose and hemicellulose decreases while that of lignin increases. The maximum pyrolysis velocity of cellulose, hemicellulose, and lignin is decreased by 36.6%, 12.4%, and 15.2%, respectively. Cd increases the pyrolysis activation energy of the three components and inhibits their deoxygenation. For the pyrolysis of Cd-contaminated rice straw, both the initial depolymerization temperature and the pyrolysis velocity of hemicellulose is reduced, while the pyrolysis velocity of cellulose is accordingly increased. When Cd loading amplifies to 0.1%, 1%, and 5%, the maximum pyrolysis velocity of hemicellulose is decreased by 7.2%, 10.5%, and 21.3%, while that of cellulose is increased by 8.4%, 62.1%, and 97.3%, respectively. Cd reduces the release of volatiles and gas from rice straw, such as CO2, CO, and oxygen-containing organics, which retains more oxygen and components in the solid fraction. This research suggested that Cd retards the pyrolysis velocity and deoxygenation of rice straw, being therefore beneficial to obtaining more biochar.

Factors controlling the temporal variability and spatial distribution of dissolved cadmium in the coastal Salish Sea

Cadmium (Cd) is a transition metal that can be toxic to aquatic biota even at low levels. The adverse effects of Cd are of particular concern in waterbodies along the eastern margin of the Pacific Ocean, where anthropogenic inputs are superimposed on the naturally elevated oceanic concentrations. While the accumulation of Cd in marine bivalves is well documented, few studies have investigated the cycling of dissolved Cd in estuarine and coastal waters that are susceptible to Cd enrichment. Here we examine the temporal and spatial variations of dissolved Cd in the coastal waters of Salish Sea in the northeast Pacific, with a focus on the Strait of Georgia (SoG). We find that the distribution of dissolved Cd in the Salish Sea is largely governed by conservative mixing between the upwelled Pacific water and freshwater discharge from the Fraser River, with a biological overprint transferring some of Cd from surface to deep water. Anthropogenic loadings of Cd from municipal effluent are negligible compared to natural inputs. Spatially, dissolved Cd and salinity gradually decrease as the Pacific source water flows landward from Juan de Fuca Strait into the SoG. Time-series sampling in the southern SoG reveals a small but significant decrease of dissolved Cd concentrations in the SoG deep layer over a winter stagnation period. We attribute this decline to diffusive removal, as driven by Cd sulfide precipitation in suboxic porewaters. The intermittent stagnation of the SoG deep layer provides a natural “benthic chamber” to estimate elemental exchange between deep water and sediment on a basin-scale, which could be valuable for studying the biogeochemical cycling of other trace metals.

Simulation of heavy metals behaviour during Co-processing of fly ash from municipal solid waste incineration with cement raw meal in a rotary kiln

Fly ash produced from incineration of municipal solid wastes (MSW) contains heavy metals, such as Cd and Pb, that make this material difficult to manage and dispose of safely. Because the composition of fly ash is similar to cement raw meal, partial replacement of raw meal with fly ash may be a feasible way to reduce the health and environmental hazards of the ash, provided that the heavy metals can be effectively stabilized in the solid phase. This research employs proprietary thermochemical software to simulate the thermodynamic behavior and single-step fixation of Cd and Pb in industrial cement kilns. The effect of Cd, Pb and Cl loadings on the fixation and/or evaporation of Cd and Pb during the sintering process is analyzed using data from industrial cement kilns. A simplified model is created based on elemental mass balance to evaluate multi-step fixation of Cd and Pb with cement kiln dust recycle.The results indicate that Cd forms Cd(OH)2(g) in a highly alkaline environment, while nearly 90% Pb is volatilized as PbCl2(g). In the clinker, increased Cl−1 decreased the proportion of Pb and Cd, moreover, Pb and Cd increased in kiln dust with Cl−1 increased; Calculations using a kiln dust recycle model showed that, the concentrations of Pb and Cd in both kiln dust and clinker increased sharply after recycling of kiln dust in steady state. Under unstable conditions, the concentrations of Pb and Cd in kiln dust increased, as well as the heavy metals re-entering the cement kiln.

Effects of soil aging conditions on distributions of cadmium distribution and phosphatase activity in different soil aggregates

Aging behaviors of metals in the field differ from those in a controlled laboratory environment. Whether aging conditions influence the fates of metals in soil remains unclear. In this study, distributions of cadmium (Cd) and phosphatase activity were compared in soil aggregates (i.e., >2, 1–2, 0.25–1, and <0.25 mm) along a profile (0–5, 5–10, and 10–15 cm) at the end of 500-day aging experiments under both controlled laboratory and field conditions. Cd concentration in the 0–5 cm layer was lower and Cd concentration in the 5–10 cm layer was higher in field-aged soil compared to laboratory-aged soil. 25.26–35.62% of soil Cd was loaded in >2 mm aggregates of field-aged soils, and 58.41–66.95% was in laboratory-aged soils. Higher loadings of Cd in 0.25–1 and <0.25 mm aggregates were found in field-aged soil. A higher proportion of exchangeable Cd fraction (20.93% of total soil Cd) was found in the 0–5 cm layer of field-aged soil than in laboratory-aged soil (17.63%), while the opposite tendency was found in deeper soil layers. Soil phosphatase activities in field-aged soils were 1.13–1.26 times higher than in laboratory-aged soils. Phosphatase loadings in the >2 mm aggregates were lower and loadings in both the 1–2 and 0.25–1 mm aggregates were higher in field-aged soils than in laboratory-aged soils. Furthermore, correlation analysis and principal component analysis indicated that available Cd fractions accounted for most of the variations in phosphatase activities. In summary, the fates of the exogenous metal Cd differed between field and controlled laboratory conditions. To better understand the behaviors of heavy metals in soil, especially in a seasonal freeze-thaw area, further field studies are needed.

Fibrinogen mediates cadmium-induced macrophage activation and serves as a predictor of cadmium exposure in chronic obstructive pulmonary disease.

The etiologies of chronic obstructive pulmonary disease (COPD) remain unclear. Cadmium (Cd) causes both pulmonary fibrosis and emphysema; however, the predictors for Cd exposure and the mechanisms by which Cd causes COPD remain unknown. We demonstrated that Cd burden was increased in lung tissue from subjects with COPD and this was associated with cigarette smoking. Fibrinogen levels increased markedly in lung tissue of patients with smoked COPD compared with never-smokers and control subjects. Fibrinogen concentration also correlated positively with lung Cd load, but inversely with the predicted % of FEV1 and FEV1/FVC. Cd enhanced the secretion of fibrinogen in a cdc2-dependent manner, whereas fibrinogen further mediated Cd-induced peptidylarginine deiminase 2 (PAD2)-dependent macrophage activation. Using lung fibroblasts from CdCl2-treated Toll-like receptor 4 (TLR4) wild-type and mutant mice, we demonstrated that fibrinogen enhanced Cd-induced TLR4-dependent collagen synthesis and cytokine/chemokine production. We further showed that fibrinogen complexed with connective tissue growth factor (CTGF), which in turn promoted the synthesis of plasminogen activator inhibitor-2 (PAI-2) and fibrinogen and inhibited fibrinolysis in Cd-treated mice. The amounts of fibrinogen were increased in the bronchoalveolar lavage fluid (BALF) of Cd-exposed mice. Positive correlations were observed between fibrinogen with hydroxyproline. Our data suggest that fibrinogen is involved in Cd-induced macrophage activation and increases in fibrinogen in patients with COPD may be used as a marker of Cd exposure and predict disease progression.

Interaction of Divalent Metals with Struvite: Sorption, Reversibility, and Implications for Mineral Recovery from Wastes

Phosphorus (P) recovered from wastewater as struvite (MgNH4PO4·6H2O) can meet high P demands in the agricultural sector by reuse as a P fertilizer. Heavy metals are prevalent in wastewaters and are common fertilizer contaminants, therefore struvite as a sorbent for metals requires evaluation. Struvite sorption experiments were conducted in model solutions with cadmium (Cd), cobalt (Co), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) at 1-5 μM concentrations from pH 7-10. The struvite metal loading increased with dissolved metal concentration and pH, ranging from 2-493 mg kg-1. Highest loadings were observed for 5 μM Pb, which exceeded the 120 mg kg-1 European Union (EU) struvite fertilizer limit at all pH values. At 5 μM concentrations, Ni and Cd loadings exceeded EU limits of 100 mg kg-1 at pH 10, and 60 mg kg-1 at pH 8-10, respectively. In desorption experiments, 10-85% metal was released after resuspension in metal-free solutions, with a positive correlation between initial loading and amount desorbed. Distortions of the struvite phosphate band, by Fourier transformation infrared (FTIR) spectroscopy, indicated lowered symmetry of phosphate vibrations with metal sorption. X-ray absorption fine structure spectroscopy (XAFS) analysis of pH 9 solids indicated tetrahedral coordination for Cu and Zn, octahedral coordination for Co and Ni, and Pb in 9-fold coordination. Precipitation of Pb-phosphate minerals was a primary mechanism for Pb sorption. The results provide insight into metal contaminant sorption with struvite in wastewaters, and the potential for metal desorption after recovery.

Integrated Assessment of Land-to-River Cd Fluxes and Riverine Cd Loads Using Swat-Hm to Guide Management Strategies

Integrated Assessment of Land-to-River Cd Fluxes and Riverine Cd Loads Using Swat-Hm to Guide Management Strategies

The relative contributions of root uptake and remobilization to the loading of Cd and As into rice grains: Implications in simultaneously controlling grain Cd and As accumulation using a segmented water management strategy

Cadmium (Cd) and arsenic (As) are loaded into rice grain via two pathways: i) root uptake from the soil and then translocation to the grain, and ii) remobilization of Cd and As previously accumulated within the vegetative tissues to the grain. However, the relative contributions of the two pathways are not well understood in soil-grown rice plants. In this study, we used eight different water management regimes applied at different growth periods to manipulate the concentrations of Cd and As in porewater and then established a mathematical model to estimate the relative importance of the two pathways. Different water management regimes had dramatic and opposite effects on the solubility of Cd and As in soil, and their subsequent accumulation in both straw and grain. Water management applied at different growth periods had markedly different impacts on grain Cd and As concentrations. Water management during grain filling had a much greater impact on grain Cd than on grain As concentrations, whereas water treatment during the vegetative growth stage had a larger effect on grain As concentrations. Under the typical water management practice (i.e. flooding through the vegetative stage followed by drainage during grain filling), grain filling is the key period for the accumulation of Cd in the grain, with 98% of the grain Cd from root uptake during this period and the contribution of remobilization being very limited. In contrast, 95% of the grain As was remobilized from that accumulated within the plant prior to the grain filling, with the tillering, jointing, and heading period each contributing 20–40% of the grain As, whereas root uptake during grain filling contributed minor. These differences can be harnessed to design a segmented water management strategy to control grain Cd and As accumulation simultaneously.

In search of the exclusion/low-accumulation mechanisms: Cadmium uptake and accumulation from soil by cultivated (Solanum melongena L.) and wild eggplants (Solanum torvum L.)

The use of Cd-excluding cultivars on the most widespread soils moderately polluted with Cd is a sustainable solution for the safe agricultural production. In order to explore the defense mechanisms and differences in the cadmium (Cd) uptake from soils and accumulation in plant tissues between low-accumulator and excluder plants, Cd concentrations/loads in plant tissues and impact on plant growth and physiological properties (photosynthetic characteristics, antioxidant enzymes and related indices) of the cultivar Solanum melongena Liaoqie No.3 (SML) and the wild species Solanum torvum (STO) grown in soils containing from 0.24 to 18.61 mg kg−1 Cd (i.e. from the natural Cd content through moderate to high pollution level) were studied in the pot experiments carried out under natural light conditions. It was found that the major protective barrier in the more sensitive to Cd toxicity excluder species (STO) was a root system accumulating 2-3-fold lesser Cd loads through the induction of dehydration/drought stress than a more Cd-tolerant low-accumulating plant (SML). A supportive defense mechanism appeared to be a reduced Cd enrichment of a xylem sap and its increased flow rate during long-distance transport from roots to leaves, occurring in the both types of plants, but with a lesser intensity in a more Cd-tolerant low-accumulating species. Due to maintaining plant-specific Cd-adaptive level, growth and biomasses of both species were basically the same, while due to the considerably lower Cd accumulation, photosynthetic parameters were higher in Cd-excluder STO species, and the amounts of lipid peroxidation (MDA) and free proline were higher in Cd low-accumulating SML cultivar. Concurrence of Cd and drought-resistance mechanism and better physiological parameters in Cd-excluder suggest promotion of this mechanism in cultivars under the climate change conditions.