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Aims: Atmospheric trace metal deposition is an important source in agricultural soils and crops, but a large knowledge gap exists between foliar and root uptake of wet/dry deposition. We aim to distinguish the contribution of dry and wet-deposited trace metals to rice plant via foliar and root uptake and to investigate their accumulations during the full growth season. Methods: We performed an atmospheric exposure experiment using customized open top chambers (OTCs) to distinguish the impacts of wet and dry deposition contribution to foliar and root uptake and their mobility in soils. The foliar uptake and then translocation was hypothesized the major pathway of trace metal accumulation in rice grains. Results: Foliar uptake of wet- and dry-deposited Cu, Zn, and Pb played an important role in their accumulations in rice plant, contributing to 44–47%, 23–25%, and 35–37% in rice grains, respectively. The leaf Cu, Zn, and Pb accumulated from atmospheric deposition can be transported upward to rice grains but nodes seem to restrict them downward translocation. Rice leaves cannot directly take up atmospheric As and the deposited As can only accumulate in rice through the root uptake. The trace metals showed high mobility in atmospheric deposition, which significantly increase the bioavailable trace metal fractions in surface soils and soil solutions. Conclusions: This study provides a new insight of similar or even higher contributions of foliar uptake than root uptake of trace metals from atmospheric deposition and that reducing the accumulation of atmospheric trace metals due to deposition on leaves can effectively decrease the accumulation of trace metals in crops. [ABSTRACT FROM AUTHOR]

Purpose: The three objectives are as follows: (1) to characterize phosphorus (P) adsorption/desorption with a series of representative iron/aluminum (Fe/Al) (hydr)oxides; (2) to assess the cyanobacterial availability of P adsorbed onto Fe/Al (hydr)oxides; and (3) to correlate the cyanobacterial availability of P to its adsorption/desorption onto Fe/Al (hydr)oxides and pH and discuss the related ecological implication. Materials and methods: Using five representative minerals (ferrihydrite, goethite, hematite, bayerite, and corundum), we conducted P isothermal adsorption onto Fe/Al (hydr)oxides with pH changing from 6 to 10. The cyanobacterial availability of P adsorbed onto Fe/Al (hydr)oxides (0.2 mg P g−1) was assessed by using a bioassay method with two cyanobacteria species, Microcystis aeruginosa and Dolichospermum flos-aquae, as test organisms. The 0.1 M NaOH was used to desorb P from Fe/Al (hydr)oxides that adsorbed P with different saturation degree during isothermal adsorption, to compare P desorption and its cyanobacterial availability. Results and discussion: This research verified that P adsorbed onto Fe/Al (hydr)oxides (P@Fe/Al (hydr)oxides) is a direct P source for cyanobacteria, which is available to cyanobacterial cells through desorption from mineral particles by pH regulation. The cyanobacterial availability of P@Fe/Al (hydr)oxides was dependent on mineral desorption, showing the following order: ferrihydrite < goethite < bayerite < corundum < hematite. The cyanobacterial availability of P, at an absorption amount of 0.2 mg P per gram of mineral, ranged from 66.1 to 99.4% and from 58.7 to 85.1% as assessed by Microcystis aeruginosa and Dolichospermum flos-aquae, respectively. With increasing adsorption saturation, the availability of P@Fe (hydr)oxides increased, while the availability of P@Al (hydr)oxides decreased. Conclusion: This research clarifies the relationship between the cyanobacterial availability of P and its adsorption/desorption on/from Fe/Al minerals, providing deeper insight into the ecological function of Fe/Al (hydr)oxides in water bodies. This research implies that we can characterize the buffering function of sediments/suspended particles contained Fe/Al (hydr)oxides by an adsorption–desorption equilibrium with pH regulation, greatly simplifying the complex problems in natural water bodies. [ABSTRACT FROM AUTHOR]

The atmospheric deposition of copper (Cu) and cadmium (Cd) was monitored in eight sites around a Cu smelter with similar distance to verify whether tree leaf and ring can be used as bio-indicators to track spatial pollution record. Results showed that total atmospheric deposition of Cu (103–1215 mg/m2/year) and Cd (3.57–11.2 mg/m2/year) were 4.73–66.6 and 3.15–12.2 times higher than those in background site (164 mg/m2/year and 0.93 mg/m2/year). The frequencies of wind directions significantly influenced the atmospheric deposition of Cu and Cd, and the highest atmospheric deposition of Cu and Cd were at the prevalent northeastern wind (JN), and low frequency south (WJ) and north (SW) winds for the lowest deposition fluxes. Since the bioavailability of Cd was higher than that of Cu, the atmospheric deposition of Cd was more easily adsorbed by tree leaf and ring, resulting in only significant relation between atmospheric Cd deposition and Cinnamomum camphora leaves and tree ring Cd. Although tree rings cannot correctly record the atmospheric Cu and Cd deposition, higher concentrations in the indigenous tree rings than the transplanted tree rings suggested that tree rings can reflect to some extent the variations of atmospheric deposition. Generally, spatial pollution of atmospheric deposition of heavy metals cannot reflect the distribution of soil total and available metals around the smelter, and only camphor leaf and tree ring can bio-indicate Cd deposition. A major implication of these findings is that leaf and tree ring can serve for biomonitoring purposes to assess the spatial distribution of atmospheric deposition metal with high bioavailability around a pollution source with similar distance. [ABSTRACT FROM AUTHOR]

Biotic transformation of imidacloprid (IMD) has been widely investigated in the environments. However, little was known about IMD degradation via abiotic pathways, such as reactive oxygen species (ROS)-based oxidation processes. Here we systematically investigated the mechanism of hydroxyl radical (•OH) production and the associated IMD degradation in the goethite (α-FeOOH)-based Fenton-like systems. Results showed that IMD can be efficiently degraded in the α-FeOOH/H2O2 systems, with degradation rate exceeded 80% within 48 h. Based on the examination of electron paramagnetic resonance (EPR) and chemical probes, •OH was identified as the key ROS that responsible for IMD degradation. IMD can be decomposed via hydroxylation or removal of -N-NO2 to produce hydroxylated IMD, cyclic urea and 6-chloronicotinic acid, with the associated toxicities also evaluated. In addition, the increasing H2O2 concentration and decreasing solution pH both significantly increased IMD degradation. This study provides theoretical understanding for the implications of soil mineral-based Fenton-like reactions in the abiotic transformation of pesticide pollutants. [ABSTRACT FROM AUTHOR]

Develop a broadband, ultra-thin metamaterial absorber based on a carbonyl iron cylinder array to overcome the performance limitations of traditional magnetic absorbers in complex electromagnetic environments. The proposed metamaterial achieves a high absorption rate of 90% across a wide frequency range, spanning from 3.44 GHz to 18 GHz, and effectively covers the C, X, Ku, and 28% of the S bands, with a remarkably thin profile of just 2.4 mm. The impact of adjustments in structural parameters on the material’s absorption intensity is comprehensively analyzed. Additionally, the absorber demonstrates polarization insensitivity and sustains high absorption under oblique incidence, maintaining a rate above 90% at 10.02 GHz with an incident angle up to 50 degrees. Detailed investigations into the electric field, magnetic field, and power loss across frequencies provide insight into the absorption mechanisms. These results highlight an innovative approach to designing high-performance electromagnetic absorbing metamaterials with significant potential for practical applications in complex environments. [ABSTRACT FROM AUTHOR]

Design and analysis of a broadband reflective polarization-converting metasurface is presented. By designing the periodic structure of the metal–dielectric–metal metasurface, the bandwidth is expanded by using the resonance peak generated by an asymmetric rod-shaped ring with a hole resonance unit which exhibits peak resonances at frequencies of 8.26 GHz, 12.57 GHz, and 16.57 GHz. The simulation results indicate that, in the frequency range from 7.76 to 17.14 GHz, the polarization conversion rate of the polarization conversion metasurface reaches more than 90%. The efficiency is kept higher than 80% with a wide incident angle up to 40°. The relative bandwidth reaches 75%. The experimental results agree well with the simulation results. Operating bandwidth covers 95% of the X and Ku bands. A polarization converter with a simple structure and easy to be fabricated has potential applications in fields like radar and optical communications, wireless communications, etc. [ABSTRACT FROM AUTHOR]

In the context of the water environmental protection and local economic sustainable growth, it is of great importance to conduct a comprehensive water quality assessment in Chaohu Lake basin. In this study, dissolved oxygen (DO), permanganate index (CODMn), 5-day biochemical oxygen demand (BOD5), ammonia nitrogen (NH3-N), total nitrogen (TN), and total phosphorus (TP) were investigated monthly at 24 sampling sites in Chaohu Lake basin during 2015 to 2017. Five methods were used to evaluate water quality and identify dominant pollutants. Results showed that the dominant pollutants in Chaohu Lake were TN (4.17~11.61 mg L−1) and TP (0.27~0.75 mg L−1). The upstream of Chaohu Lake was influenced by Nanfei River, Shiwuli River, and Paihe River, and water quality of the upstream (eutrophic) was worse than that of the downstream (mesotrophic) part of Chaohu Lake. Comprehensive Water Quality Identification Index Method (CWQII) can better assess the water quality compared with the other methods by providing qualitative and quantitative analysis. The index values assessed by CWQII method for Nanfei River, Shiwuli River, and Paihe River were 5.819, 5.986, and 5.141, respectively, and water quality were all assessed as grade V. Overall, water quality of Chaohu Lake has been slightly improved during 2015~2017, but water quality of western inflowing rivers was still heavily polluted. These findings provide valuable information and guidance for water pollution control and water resource management in Chaohu Lake basin. Several feasible measures are proposed. [ABSTRACT FROM AUTHOR]

It is well known that alkaline amendments could effectively decrease the bioavailability of heavy metals in soils. However, the vertical distribution of heavy metals and the nutrients enriching in amendments are little concerned during long-term field remediation. Thus, the objective of the present study was to investigate the vertical distribution and availability of Cu, Cd, Ca, and P after a 7-year field experiment. In this study, a single application of lime and apatite was conducted with the rates of 1.71-6.84 and 6.84-19.8 tons/ha, respectively. Soil pH and immobilization efficiency of Cu and Cd were both increased with increasing dosages of lime and apatite (0-50 cm). Applications of lime and apatite decreased the mobility of Cu and Cd although soil Cu and Cd in the surface soil were increased due to the input by atmospheric dry and wet deposition. Moreover, concentrations of Cu and Cd in lime- and apatite-amended soils (0-13 cm) were higher than those in the control group. However, applications of lime and apatite decreased the downward eluviations of heavy metals in soils (13-50 cm). For soil nutrients, the Ca concentrations at 0-13 and 13-30 cm were both enhanced with increasing amendment dosages, while only soil P concentration at 0-13 cm was increased in apatite-treated soils and majority of them presented in stable-P. In addition, resin-P was increased with increasing dosages of the apatite, which suggested that high eutrophication risk was induced by excessive P loss. Thus, more attention should be paid to the nutrients (phosphorus) and pollutants enriching in the amendments during in-situ remediation of heavy metal-contaminated soils. [ABSTRACT FROM AUTHOR]

Phosphate amendments have been used to immobilize heavy metal-contaminated soils. However, phosphate amendments contain large amounts of phosphorus, which could leach out to potentially contaminate groundwater and surface water. A laboratory column leaching experiment was designed to study the effects of simulated acid rain (SAR) on the potential release of copper (Cu), lead (Pb), cadmium (Cd), and phosphorus (P), and their availability after immobilizing with hydroxyapatite (HAP) and potassium dihydrogen phosphate (PDP). The application of HAP and PDP enhanced the leachate electrical conductivity, total organic carbon, and pH. Higher P was found in the PDP- (>4.29 mg L) and HAP-treated (>1.69 mg L) columns than that in untreated (<0.2 mg L) columns, and they were both over the class V limit (0.4 mg L) mandated by the Chinese National Quality Standards for Surface Waters (GB 3838-2002). PDP application decreased the leachate Cu, Pb, and Cd effectively; however, HAP addition increased leachate Cu and Pb. HAP and PDP applications decreased the soil CaCl-extractable and exchangeable fraction of Cu, Pb, and Cd, and increased resin P. However, eluviations transformed the heavy metals from inactive to active fractions and reduced soil labile P. These findings showed that HAP and PDP had a potential risk of excessive P-induced eutrophication. Meanwhile, more attention should be paid to the leaching loss of multiple metals because phosphate amendments might promote the leaching of some metals while immobilizing others. [ABSTRACT FROM AUTHOR]

Only a few studies have been reported on the stability and heavy metal distribution of soil aggregates after soil treatments to reduce the availability of heavy metals. In this study, apatite (22.3 t ha), lime (4.45 t ha), and charcoal (66.8 t ha) were applied to a heavy metal-contaminated soil for 4 years. The stability and heavy metal distribution of soil aggregates were investigated by dry and wet sieving. No significant change in the dry mean weight diameter was observed in any treatments. Compared with the control, three-amendment treatments significantly increased the wet mean weight diameter, but only charcoal treatment significantly increased the wet aggregate stability. The soil treatments increased the content of soil organic carbon, and the fraction 0.25-2 mm contained the highest content of soil organic carbon. Amendments' application slightly increased soil total Cu and Cd, but decreased the concentrations of CaCl -extractable Cu and Cd except for the fraction <0.053 mm. The fractions >2 and 0.25-2 mm contained the highest concentrations of CaCl-extractable Cu and Cd, accounted for about 74.5-86.8 % of CaCl-extractable Cu and Cd in soil. The results indicated that amendments' application increased the wet soil aggregate stability and decreased the available Cu and Cd. The distribution of available heavy metals in wet soil aggregates was not controlled by soil aggregate stability, but possibly by soil organic carbon. [ABSTRACT FROM AUTHOR]

Purpose: In situ immobilization of heavy metal-contaminated soils with the repeated incorporation of amendments can effectively reduce the bioavailability of soil heavy metals. However, the long-term application of amendments would lead to the destruction of soil structure and accumulation of soil toxic elements, ultimately affecting food security and quality. Thus, the sustainability of the amendments in a heavy metal-contaminated soil was evaluated from 2010 to 2012. Materials and methods: Batch field experiments were conducted in the soils, which were amended with apatite (22.3 t ha), lime (4.45 t ha), and charcoal (66.8 t ha), respectively. The amendments were applied only one time in 2009, and ryegrass was sown each year. Ryegrass and setaria glauca (a kind of weed) were harvested each year. Concentrations of copper (Cu) and cadmium (Cd) were determined by batch experiments. Five fractions of Cu and Cd were evaluated by a sequential extraction procedure. Results and discussion: Ryegrass grew well in the amended soils in the first year, but it failed to grow in all the soils in the third year. However, setaria glauca could grow with higher biomass in all the amended soils. The treatment of apatite combined with plants was more effective than lime and charcoal treatments in removing Cu and Cd from the contaminated soils by taking biomass into account. Apatite had the best sustainable effect on alleviating soil acidification. The Cu and Cd concentrations of CaCl-extractable and exchangeable fractions decreased with the application of amendments. Moreover, apatite and lime could effectively maintain the bioavailability of Cu and Cd low. Conclusions: Apatite had a better sustainable effect on the remediation of heavy metal-contaminated soils than lime and charcoal. Although all the amendment treated soils did not reduce soil total concentrations of Cu and Cd, they could effectively reduce the environmental risk of the contaminated soils. The findings could be effectively used for in situ remediation of heavy metal-contaminated soils. [ABSTRACT FROM AUTHOR]

Purpose: Many amendments have been applied to immobilize heavy metals in soil. However, little information is available on the changes of immobilization efficiencies of heavy metals in contaminated soils over time. This work investigated the immobilization efficiencies of copper (Cu) and cadmium (Cd) in contaminated soils in situ remediated with one-time application of three amendments for 1 year and 4 years. Materials and methods: Apatite, lime, and charcoal were mixed with the topsoil of each plot with the amounts of 22.3, 4.45, and 66.8 t/ha, respectively. Soil chemical properties and fractions of Cu and Cd were examined after in situ remediation for 1 year and 4 years. Soil sorption and retention capacities and desorption proportions for Cu and Cd were investigated by batch experiments. Results and discussion: The addition of amendments significantly increased soil pH, but decreased exchange acid and aluminum (Al). The amendments significantly decreased the CaCl extractable Cu and Cd and transformed them from active to inactive fractions. After the application of amendments for 1 year, the maximum sorption capacities ranged from 35.6 to 38.8 mmol/kg for Cu and from 14.4 to 17.0 mmol/kg for Cd, which were markedly higher than those of the application of amendments for 4 years (Cu, 29.6-34.7 mmol/kg; Cd, 10.9-16.4 mmol/kg). Desorption proportions (D) of Cu and Cd using three extractants followed the order of $$ {D}_{{\mathrm{NaNO}}_3}<{D}_{{\mathrm{CaCI}}_2}<{D}_{{\mathrm{MgCI}}_2} $$. Moreover, the retention capacities (R) of Cu and Cd both increased and followed the order of R > R > R, resulting in higher Cu and Cd in the amended soils than the untreated soil. Conclusions: Apatite, lime, and charcoal increased the soil sorption and retention capacities of Cu and Cd and resulted in higher immobilization efficiencies in the amended soils than the untreated soil. However, the immobilization efficiencies of Cu and Cd decreased with the decrease of sorption capacities after 4 years. It was concluded that apatite had the best effect on the long-term stability of immobilized Cu and Cd and can be applied to immobilize heavy metals in contaminated soils. [ABSTRACT FROM AUTHOR]

Purpose: With the rapid development of nanotechnology, hydroxyapatite-based nanoparticles have been applied in wastewater and soil remediation. However, limited studies have been conducted on the remediation of heavy metal-contaminated soils by microhydroxyapatite (MHA) and nanohydroxyapatite (NHA). Thus, we investigated the effects of MHA and NHA on soil pH values and fractions of copper (Cu) and cadmium (Cd). The changes of soil enzymes with application of MHA and NHA were also evaluated. Materials and methods: Pots contained 200 g of the soil with MHA and NHA ranging from 1 % to 5 % incubated for 60 days under greenhouse condition, and maintained at 60 % of soil water holding capacity by adding deionized water. Soil pH, catalase, urease, and acid phosphatase were analyzed at incubation times of 7, 14, 30, and 60 days by chemical assays. The fractions of Cu and Cd were analyzed after 60 days by a sequential extraction procedure. Results and discussion: Application of MHA and NHA significantly increased soil pH values. Especially, we found for the first time that soil pH values with 3 % (pH > 7.90) and 5 % (pH > 8.83) application rates of MHA were larger than that of MHA itself (pH = 7.71). MHA was more effective than NHA in immobilizing Cu and Cd by significantly decreasing exchangeable fractions of Cu and Cd and transforming them from active to inactive fractions. Soil catalase and urease significantly increased, but acid phosphatase apparently decreased with increasing application rates of MHA. However, three enzymes activities changed slightly for NHA treatments. Conclusions: MHA was more effective than NHA in immobilizing Cu and Cd. MHA had a more positive effect on soil catalase and urease activities than NHA. Furthermore, Pearson's correlation coefficients showed that soil pH value was a key factor to influence the bioavailability of Cu and Cd and the activity of soil enzymes. The results of this study provided an efficient method for the remediation of heavy metal-contaminated soils. [ABSTRACT FROM AUTHOR]

The correct presentation of the Figure 1 image is shown in this paper. [ABSTRACT FROM AUTHOR]