Effects of combined microplastics and heavy metals pollution on terrestrial plants and rhizosphere environment: A review.

Microplastics (MPs) can enter the soil environment through industry, agricultural production and daily life sources. Their interaction with heavy metals (HMs) poses a significant threat to a variety of terrestrial ecosystems, including agricultural ones, thereby affecting crop quality and threatening human health. This review initially addresses the impact of single and combined contamination with MPs and HMs on soil environment, including changes in soil physicochemical properties, microbial community structure and diversity, fertility, enzyme activity and resistance genes, as well as alterations in heavy metal speciation. The article further explores the effects of this pollution on the growth characteristics of terrestrial plants, such as plant biomass, antioxidant systems, metabolites and photosynthesis. In general, the combined contaminants tend to significantly affect soil environment and terrestrial plant growth, i.e., the impact of combined contaminants on plants weight ranged from -87.5% to 4.55%. Similarities and differences in contamination impact levels stem from the variations in contaminant types, sizes and doses of contaminants and the specific plant growth environments. In addition, MPs can not only infiltrate plants directly, but also significantly affect the accumulation of HMs in terrestrial plants. The heavy metals concentration in plants under the treatment of MPs were 70.26%-36.80%. The co-occurrence of these two pollution types can pose a serious threat to crop productivity and safety. Finally, this study proposes suggestions for future research aiming to address current gaps in knowledge, raises awareness about the impact of combined MPs + HMs pollution on plant growth and eco-environmental security.

High-efficiency combination washing agents with eco-friendliness simultaneously removing Cd, Cu and Ni from soil of e-waste recycling site: A lab-scale experiment.

Soil washing technology plays an important role in the removal of heavy metals, and the efficacy of this process depends on the washing agent used. Due to the difficulty in treating soils contaminated by multiple heavy metals, there is still a need for further exploration of efficient washing agents with low environmental impact. Although single washing agents, such as chelators, can also effectively remove heavy metals from soil, combining efficient washing agents and determining their optimal washing conditions can effectively improve their removal efficiency for multiple heavy metals in soil simultaneously. Based on the previous research, the present study was carried out to combine different types of washing agents to remediate contaminated soils at a commonly e-waste recycling site. The objectives were to investigate their efficient washing conditions and assess the impact of the washing process on the speciation distribution and pollution level associated with heavy metals in soil. The results showed that the combination of HEDP (1-hydroxyethylidene-1,1-diphosphonic acid) and FeCl3 at a ratio of 6:4 exhibited the most effective removal of Cd, Cu and Ni from the contaminated soil at an e-waste recycling site. Under optimal washing conditions, with a soil-to-liquid ratio of 1:20 and a washing time of 48 h, the removal rates of Cd, Cu and Ni were 96.72%, 69.91% and 76.08%, respectively. It needed to be emphasized that the combination washing agents were able to remove most of the acid-soluble, reducible and oxidizable fractions of heavy metals, and even the removal rates of the stable residual fraction (e.g., of Cd) was at a relatively high level. In addition, the washing process significantly reduced the pollution level associated with heavy metals in soil. This study aid in the development of combined efficient washing agents and explores optimal washing strategies for the remediation of Cd, Cu, and Ni-contaminated soil at e-waste recycling sites. The findings may play a role in enhancing the remediation capabilities for soils contaminated with multiple heavy metals, due to its characteristics of and high-efficiency and environmental friendliness.

Effect of ammonium sulfate combined with aqueous bio-chelator on Cd uptake by Cd-hyperaccumulator Solanum nigrum L.

The efficacy of using plants to phytoremediate heavy metal (HM) contaminated soils can be improved using soil amendments. These amendments may both increase plant biomasses and HMs uptake. We aimed to determine the composite effect of ammonium sulfate ((NH4)2SO4) combined with the application of an aqueous stem-extracted bio-chelator (Bidens tripartita L) on the plant biomasses and cadmium (Cd) phytoextraction by Solanum nigrum L. The constant (NH4)2SO4 application mode plus bio-chelator additives collectively enhanced the shoot Cd extraction ability owing to the increased plant biomass and shoot Cd concentration by S. nigrum. The shoot Cd extraction and the soil Cd decreased concentration confirmed the optimal Cd phytoextraction pattern in K8 and K9 treatments (co-application of (NH4)2SO4 and twofold/threefold bio-chelators). Accordingly, Cd contamination risk in the soil (2 mg kg-1) could be completely eradicated (<0.2 mg kg-1) after three rounds of phytoremediation by S.nigrum based on K8 and K9 treatments through calculating soil Cd depletion. The microorganism counts and enzyme activities in rhizosphere soils at treatments with the combined soil additives apparently advanced. In general, co-application mode of (NH4)2SO4 and aqueous bio-chelator was likely to be a perfect substitute for conventional scavenger agents on account of its environmental friendliness and cost saving for field Cd contamination phytoremediation by S. nigrum.

The effect of exogenous plant growth regulators on elevated Cd phytoremediation by Solanum nigrum L. in contaminated soil.

Maximizing amendment potential is an emphasis in the HM-contaminated field of phytoremediation by hyperaccumulators due to the low bioavailability of HMs in soils and small biomass yields of plants. This study investigated the influence of different types and concentrations of plant growth regulators on Cd phytoremediation by Solanum nigrum in contaminated soil. Our conclusions showed that the shoot Cd extractions (µg plant-1) and the root and shoot biomasses at all the treatments remarkedly increased compared with that of the CK (p < 0.05), while the Cd concentrations at root and aboveground parts by S. nigrum, the extractable Cd concentrations, and pH value of soils did not change significantly compared with the CK (p < 0.05). Furthermore, correlation analysis showed that the shoot Cd phytoaccumulation and the root and aboveground biomasses of S. nigrum were particularly dependent upon the application of CTK and GA3 concentration gradient (p < 0.05). Moreover, some related physicochemical indexes were determined for supervising the growth conditions of plants, and these results pointed out that after exogenous PGRs treatments, the chlorophyll content and antioxidative enzymes POD and SOD activities in vivo of plants clearly advanced, while the H2O2 and MDA contents and CAT apparently declined. These consequence demonstrated that the exogenous PGR addition prominently reinforced the Cd phytoextraction capacity of S. nigrum in contaminated soil by stimulating plant growth and increasing shoot yields.

[Analysis of the Environmental Risk of Livestock Manure Pollution and Resource Treatment Technology].

Rapid development of the livestock and poultry industry has greatly promoted the rural economic prosperity of China. However, the problems resulting from the livestock manure, such as large emissions, low utilization rate, and environmental pollution are also becoming increasingly serious. Based on the current situation of livestock manure discharge in China, the typical contaminants in livestock manure and their pollution characteristics in soil, water, and air were systematically analyzed in this study. Taking heavy metals and antibiotics as the characteristic pollutants, the common risk assessment methods for livestock manure pollution were described. Moreover, the main harmless disposal and recycling treatment technologies of livestock and poultry manure at home and abroad were compared and analyzed. The application prospect and value of these technologies such as the thermochemical conversion method and the biological method in energization or fertilization were evaluated. Furthermore, the prominent problems in the pollution control of livestock manure are discussed, and the development trends in the resource treatment technology of livestock manure were also prospected.

Photochemical degradation in natural attenuation of characteristics of petroleum hydrocarbons (C10-C40) in crude oil polluted soil by simulated long term solar irradiation.

Photodegradation process plays an important role in the natural attenuation of petroleum hydrocarbons (PHs) in oil contaminated soil. The photodegradation characteristics of PHs (C10-C40) in topsoil of crude oil contaminated soil irradiated by simulated sunlight in 280 d without microbial action were investigated. The results showed that photodegradation rate of PHs was increased with increasing the light intensity and decreased with increasing the initial concentration of PHs. Moreover, the photodegradation capacity of tested PHs was relevant to the length of carbon chain. The photodegradation rates of C10-C20 were higher than that of C21-C40 in photoperiod. C21-C40 showed an obvious trend of photodegradation after 56 d, although their photodegradation rates were less than 20% at the early stage. And, the redundancy analysis indicated that lighting time was the primary factor for photodegradation of PHs under abiotic conditions. The photodegradation rate was well interpreted by a two-stage, first-order kinetic law with a faster initial photolysis rate. The EPR spectrums showed that simulated solar irradiation accelerated the generation of superoxide radicals, which could react with PHs in soil. Also, the function groups in PHs polluted soil were changed after light exposure, which might imply the possible photodegradation pathway of PHs.

[Research Progress on the Remediation Technology of Herbicide Contamination in Agricultural Soils].

Asthe most-used pesticides in the agricultural production process, herbicides are mainly applied to protect crops from weeds. However, with the increased global demand for food, the dosage of herbicides is rising annually, and the efficacy of herbicides is getting stronger, which can cause some environmental issues including the accumulation, migration and transformation, and toxic effects of herbicides in agricultural soils. According to the characteristics of herbicide contamination and regional agricultural production, developing green and low-carbon technologies to reduce the ecological risks of herbicides to the soil-crop systems is a current concern in the ecological environment field. In this paper, relevant studies in recent years on herbicide pollution management in agricultural soils were identified and reviewed, the research progress and application cases of remediation technologies for herbicide pollution was analyzed and demonstrated, and future research and development tendency regarding the remediation of herbicides pollution was also prospected. Current remediation technologies for herbicides mainly include bioremediation technologies (e.g., microbial remediation, enzyme remediation, and phytoremediation), adsorption, and immobilization technologies (e.g., biochar-based materials). The bioremediation technologieswere rather mature and had been applied to the herbicide-contaminated soil in fields. Additionally, many successful bioremediation cases have been reported. Moreover, in order to enhance the remediation effect on herbicide pollution in agriculture soils, remediation technologies have been gradually developed from a single model to a coupled model with physical,chemical, and biological technology, which can maximize the synergy of the multi-technology application.

Influencing Factors of Bidens pilosa L. Hyperaccumulating Cadmium Explored by the Real-Time Uptake of Cd2+ Influx around Root Apexes under Different Exogenous Nutrient Ion Levels.

Though Bidens pilosa L. has been confirmed to be a potential Cd hyperaccumulator, the accumulation mechanism is not yet clear. The dynamic and real-time uptake of Cd2+ influx by B. pilosa root apexes was determined using non-invasive micro-test technology (NMT), which partly explored the influencing factors of the Cd hyperaccumulation mechanism under the conditions of different exogenous nutrient ions. The results indicated that Cd2+ influxes at 300 µm around the root tips decreased under Cd treatments with 16 mM Ca2+, 8 mM Mg2+, 0.5 mM Fe2+, 8 mM SO42- or 18 mM K+ compared to single Cd treatments. The Cd treatments with a high concentration of nutrient ions showed an antagonistic effect on Cd2+ uptake. However, Cd treatments with 1 mM Ca2+, 0.5 mM Mg2+, 0.5 mM SO42- or 2 mM K+ had no effect on the Cd2+ influxes as compared with single Cd treatments. It is worth noting that the Cd treatment with 0.05 mM Fe2+ markedly increased Cd2+ influxes. The addition of 0.05 mM Fe2+ exhibited a synergistic effect on Cd uptake, which could be low concentration Fe2+ rarely involved in blocking Cd2+ influx and often forming an oxide membrane on the root surface to help the Cd uptake by B. pilosa. The results also showed that Cd treatments with high concentration of nutrient ions significantly increased the concentrations of chlorophyll and carotenoid in leaves and the root vigor of B. pilosa relative to single Cd treatments. Our research provides novel perspectives with respect to Cd uptake dynamic characteristics by B. pilosa roots under different exogenous nutrient ion levels, and shows that the addition of 0.05 mM Fe2+ could promote the phytoremediation efficiency for B. pilosa.

Toxicity of emerging contaminant antibiotics in soil to Capsicum annuum L. growth and their effects on it accumulating copper.

Antibiotics are a kind of emerging contaminant in soil. Tetracycline (TC) and oxytetracycline (OTC) in soil are often detected, even with very high concentration in the soils of facility agriculture due to their good effect, low price and large usage. Copper (Cu) is common heavy metal pollutant in soil. The toxicity roles of TC, OTC and/or Cu in soil on a commonly consumed vegetable Capsicum annuum L. and its Cu accumulation were not clear till now. The results of pot experiment showed that the TC or OTC added in soil alone didn't produce poison effects for C. annuum after 6 weeks and 12 weeks growth reflected by some physiological index like SOD, CAT and APX activities changes, while the biomass changes affirmed them either. Cu contaminated soil significantly inhibited the growth of C. annuum. Furthermore, combined pollution of Cu with TC or OTC was with more serious suppression of C. annuum growth. The suppression role of OTC was heavier than TC in Cu and TC or OTC contaminated soil. Such phenomenon was relevant with the role of TC or OTC increased Cu concentration in C. annuum. The improvement role of TC or OTC on Cu accumulation in C. annuum caused by the increased extractable Cu concentration in soil. The study demonstrated that TC or OTC added in soil alone was without any toxicity to C. annuum. But they may aggravate the hurt of C. annuum caused by Cu through increased its accumulation from soil. Thus, such combine pollution should be avoided in safe agricultural product.

The effects of salinity and pH variation on hyperaccumulator Bidens pilosa L. accumulating cadmium with dynamic and real-time uptake of Cd2+ influx around its root apexes.

Bidens pilosa L. has been confirmed to be a potential Cd hyperaccumulator by some researchers, but the dynamic and real-time uptake of Cd2+ influx by B. pilosa root apexes was a conundrum up to now. The aim of our study was to investigate the effects of salinity and pH variations on the characteristics of Cd2+ influx around the root apexes of B. pilosa. The tested seedlings of B. pilosa were obtained by sand culture experiments in a greenhouse after 1 month from germination, and the Cd2+ influxes from the root apex of B. pilosa under Cd treatments with different salinity and pH levels were determined with application of non-invasive micro-test technology (NMT). The results showed that Cd2+ influxes at 300 µm from the root tips decreased under Cd treatments with 5 mM and 10 mM NaCl, as compared to Cd stress alone. However, Cd treatments with 2.5 mM NaCl had little effect on the net Cd2+ influxes, as compared to Cd treatments alone. Importantly, Cd treatments at pH = 4.0 markedly increased Cd2+ influxes in roots, and Cd treatment at pH = 7.0 had no significant effect on the net Cd2+ influxes compared to Cd treatments at pH = 5.5. Results also showed that Cd treatments with 10 mM NaCl significantly decreased concentrations of chlorophyll (Chl) a and b in leaves and root vigor of B. pilosa relative to Cd treatments alone, while there were no significant differences between Cd treatments with 2.5 mM NaCl and Cd treatments alone. But root vigor was inhibited significantly under Cd treatments with 5 mM and 10 mM NaCl. A significant increase of root vigor was observed in Cd treatments at pH = 4.0, as compared to pH = 5.5. The Cd treatments with high and medium concentrations of NaCl inhibited the uptake of Cd by B. pilosa roots and affected the Chl and root vigor further. But the Cd treatments at pH = 4.0 could promote the Cd uptake and root vigor. Our results revealed the uptake mechanisms of B. pilosa as a potential phytoremediator under different salinity and pH levels combined with Cd contamination and provided a new idea for screening ideal hyperaccumulator and constructing evaluation system.

Cadmium phytoextraction efficiency of hyperaccumulator as affected by harvest stage in three continuous years.

Phytoremediation which mainly using hyperaccumulator is a very popular and environmental-friendly clean method. Long term continuous test is very important due to its low remediation efficiency in a growth period. Cd hyperaccumulator Rorippa globosa (Turcz.) Thell. Was used to explore the effect of two remediation modes (harvests at flowering and maturity stages) on the continuous remediation efficiency in a 3-year experiment using pot experiment with real Cd contaminated soil. The results showed that the biomass in maturity-harvest treatments was 1.12 times of that in flowering-harvest treatments due to the short vegetation time. Shoot Cd concentrations in the flowering-harvest treatments were on average 15.4% lower compared to the maturity-harvest treatments either. However, the Cd phytoextraction efficiency (PE) in the flowering-harvest treatments was 13.8% higher compared to the harvests at the maturity stage due to the growth cycle of R. globosa harvested at the flowering was 34.5% of shorter compared to those in the maturity harvest treatments. After three consecutive years of R. globosa phytoextraction, the concentration of extractable Cd decreased on average by 28.7% and corresponding PEs lower either. It was suggested that cultivation modes of R. globosa and low-accumulation crop rotation, or three times flowering harvests of R. globosa per year seemed to be a good choice in practical solution.

Ecotoxicological effects and bioaccumulation in Eichhornia crassipes induced by long-term exposure to triclosan.

In this study, the ecotoxicological effects and bioaccumulation of triclosan (TCS) in Eichhornia crassipes (E. crassipes) were investigated with 28 d exposure experiments. The results showed that chlorophyll content was increased after 7 d exposure to 0.05-0.1 mg L-1 TCS, while it was inhibited significantly by 0.5 mg L-1 TCS after 21 d exposure. The concentrations of soluble protein in the leaves increased during the initial stage (7 d and 14 d), whereas they decreased during 21 d and 28 d. The concentrations of soluble protein in the roots gradually reduced during the exposure time. The antioxidant enzyme activities in roots decreased continually with the exposure time. However, the antioxidant enzyme (SOD and CAT) activities in leaves decreased after exposure longer than 14 d. Moreover, differentially expressed genes (DEGs) were observed in the root of E. crassipes after a 28 d exposure to 0.5 mg L-1 TCS, with 11023 DEGs down-regulated and 3947 DEGs up-regulated. 5 SOD down-regulated genes and 3 CAT down-regulated genes were identified from transport and catabolism in cellular processes. After 28 d exposure, the TCS content in roots and leaves stressed by 0.5 mg L-1 TCS were up to 13.04 µg g-1 and 1.97 µg g-1, respectively. SOD in leaves was negatively correlated with TCS content in leaves, CAT in roots was negatively correlated with TCS content in roots. These results provide experimental data to assess the ecological risk of TCS with long exposure in aquatic systems.

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.

Mechanism exploration of Solanum nigrum L. hyperaccumulating Cd compared to Zn from the perspective of metabolic pathways based on differentially expressed proteins using iTRAQ.

It is challenging to determine the mechanism involved in only Cd hyperaccumulation by Solanum nigrum L. owing to the uniqueness of the process. Isobaric tags for relative and absolute quantitation (iTRAQ) were used to explore the mechanism by which S. nigrum hyperaccumulates Cd by comparing the differentially expressed proteins (DEPs) for Cd and Zn accumulation (non-Zn hyperaccumulator). Based on the comparison between the DEPs associated with Cd and Zn accumulation, the relative metabolic pathways reflected by 17 co-intersecting specific proteins associated with Cd and Zn accumulation included phagosome, aminoacyl-tRNA biosynthesis, and carbon metabolism. Apart from the 17 co-intersecting specific proteins, the conjoint metabolic pathways reported by 21 co-intersecting specific proteins associated with Cd accumulation and 30 co-intersecting specific proteins associated with Zn accumulation, the most differentially expressed metabolic pathways might cause Cd TF (Translocation factor)> 1 and Zn TF< 1, including protein export, ribosome, amino sugar, and nucleotide sugar metabolism. The determined DEPs were verified using qRT-PCR with the four key proteins M1CW30, A0A3Q7H652, A0A0V0IFB9, and A0A0V0IAC4. The plasma membrane H+-ATPase protein was identified using western blotting. Some physiological indices for protein-related differences indirectly confirmed the above results. These results are crucial to further explore the mechanisms involved in Cd hyperaccumulation.

Enhanced Cd Phytoextraction by Solanum nigrum L. from Contaminated Soils Combined with the Application of N Fertilizers and Double Harvests.

It is very important to increase phytoremediation efficiency in practice in suitable climatic conditions for plant growth through multiple harvests. Solanum nigrum L. is a Cd hyperaccumulator. In the present experiment, after applying different types of N fertilizers (NH4HCO3, NH4Cl, (NH4)2SO4, CH4N2O), root and shoot biomasses and Cd phytoextraction efficiency of S. nigrum effectively improved (p < 0.05). Shoot biomasses of S. nigrum harvested at the first florescence stage plus the amounts at the second florescence stage were higher than those harvested at the maturation stage, which indicates that S. nigrum Cd phytoaccumulation efficiency was higher in the former compared to the latter as there was no clear change in Cd concentration (p < 0.05). The pH value and extractable Cd contents showed no changes, regardless of whether N fertilizer was added or not at different growth stages. In addition, after N fertilizer was applied, H2O2 and malondialdehyde (MDA) contents in S. nigrum in vivo were lower compared to those that had not received N addition (CK); similarly, the concentration of proline was decreased as well (p < 0.05). The activity of the antioxidant enzyme catalase (CAT), harvested at different growth periods after four types of N fertilizer applications, obviously decreased in S. nigrum shoots, while peroxidase (POD) and superoxide dismutase) (SOD) activities increased (p < 0.05). Our study demonstrated that (NH4)2SO4 treatment exerted the most positive effect and CH4N2O the second most positive effect on S. nigrum Cd phytoremediation efficiency in double harvests at florescence stages, and the growth conditions were better than others.

Cadmium removal potential of hyperaccumulator Solanum nigrum L. under two planting modes in three years continuous phytoremediation.

Solanum nigrum L. is a Cd hyperaccumulator, but the potential for continuous remediation, or different planting methods have not been fully characterized. The potential for continuous phytoremediation of Cd-contaminated farmland soil (2.08 mg kg-1 Cd) by 2 planting methods (flowering harvest twice a year and maturity harvest once a year) was studied in a 3-year pot experiment. The total Cd accumulation (ug plant-1) of the 3-year flowering stage treatments was 26.3% higher than that of the maturity stage treatments, which was mainly due to that flowering harvest twice a year caused 65.5% increase of shoot biomass. Similarly, the Cd decreased concentration in soil and Cd removal rate in the flowering stage treatments were 29.2% and 27.9% higher than that in the maturity stage treatments, respectively. After 3 years of phytoremediation, the extractable Cd concentration in soil was reduced by 36.4% in the flowering stage treatments and by 27.6% in the maturity stage treatments, which also led to the same decreasing trend of Cd accumulation of S. nigrum. In conclusion, the study results have demonstrated that the planting mode of two harvests a year at the flowering stage seems to be a viable option to apply for continuous phytoremediation of Cd-contaminated farmland soil.

Co-high-efficiency washing agents for simultaneous removal of Cd, Pb and As from smelting soil with risk assessment.

Soil washing is considered a highly efficient technology due to its higher removal rate of multiple heavy metals from contaminated soil. However, previous studies on Cd, Pb and As washing agents for soils with complex contaminations did not consider the differences in As and Cd/Pb properties, resulting in the lack of effective washing compounds and washing conditions for soils with complex contaminations. Moreover, most traditional washing agents can cause secondary pollution. In this study, HEDTA and lactic acid (LA) treatments resulted in a higher Cd and Pb removal, while 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) was more effective in As removal. Most importantly, a new washing strategy was proposed with a new combined high-efficiency washing agents consisting of HEDP + LA + FeCl3 with a ratio of 6:3:1. Considering washing efficiency and consumption under optimal washing conditions, i.e. the soil/liquid (S/L) ratio of 1:20 and washing time of 48 h, the rates of Cd, Pb and As removal were 79.93%, 69.84% and 61.55%, respectively. In addition, washing process could influence the speciation of heavy metals, especially oxidizable and residual Cd and Pb fractions, as well as reducible As fraction. The washing process using the new washing agent can significantly reduce the pollution level and health risk of Cd, Pb and As contamination. The results of this study can provide an efficient washing agent for the remediation of heavy metal-contaminated soils at smelting sites, which will help protect human health.

Integrated survey on the heavy metal distribution, sources and risk assessment of soil in a commonly developed industrial area.

The Jiangzhe Area was relatively common area that rely on industrial process for rapid development with serious heavy metals contamination. This study investigated the spatial, vertical and speciation distribution, correlation of heavy metals, as well as assessed pollution and health risks in three representative contamination industries at Jingjiang (electroplating site), Taizhou (e-waste recycling site) and Wenzhou (leather production site) in the Jiangzhe Area. The results indicated that the Cr(VI) pollution was serious in all three sites and there was a tendency to gradually decrease with depth. As for other heavy metals, not only the total concentration, but also the addition of acid soluble and reducible speciation generally decreased with soil depth at Jingjiang and Taizhou sites. Significantly positive correlations supported by correlation analysis were detected between the following elements: Cu-Ni (p < 0.01), Cr(VI)-Ni (p < 0.05) and Cr(VI)-Cu (p < 0.05) at Jingjiang site, Cu-Ni (p < 0.01), Cu-Cd (p < 0.01) and Ni-Cd (p < 0.05) at Taizhou site indicating possibly the same sources and pathways of origin, while the significantly negative correlation of Cd-Ni (p < 0.05) at Wenzhou site meaning the different sources. As regards the pollution assessment of topsoil, the mean PI value indicated that Cr(VI) contaminated severe in all three sites. In general, Jingjiang site was severe pollution (4.06), while Taizhou and Wenzhou (2.27 and 2.66) were moderate pollution, as NIPI value shown. In terms of health risk assessment that received much attention, non-carcinogenic risks caused by Pb contamination were significant for children at Jingjiang and Taizhou sites, with the HI values of 3.42E+ 00 and 2.03E+ 00, respectively. Ni caused unacceptable carcinogenic risk for both adults and children at all three sites. The present study can help to better understand the contamination characteristics of heavy metals in the commonly developed industrial area, and thus to control the environmental quality, so as to truly achieve the goal of "Green Deal objectives ".

Difference in Cd2+ flux around the root tips of different soybean (Glycine max L.) cultivars and physiological response under mild cadmium stress.

The purpose of the study was to compare differences in Cd2+ flux in the vicinity of root tips of 20 soybean cultivars under mild Cd stress conditions using non-invasive micro-test technology (NMT). The results indicated that Cd2+ influx to the root tips under mild Cd treatment was higher compared to controls. Cd2+ influx showed an obvious spatial distribution, with the highest Cd2+ influx measured 300 µm from the root tips, and a gradually decrease above and below this site. The cultivar Liaodou32 had a lower Cd uptake (3.40 pmol cm-2 s-1), while Liaodou23 had a relatively higher Cd uptake (66.37 pmol cm-2 s-1). Cluster analysis showed that the order of the average Cd2+ influx of the cultivars at a distance of 300 µm from the root tips was as follows: high-uptake cultivars (61.80 pmol cm-2 s-1)>medium-high-uptake cultivars (33.92 pmol cm-2 s-1)>medium-low-uptake cultivars (19.78 pmol cm-2 s-1)>low-uptake cultivars (4.84 pmol cm-2 s-1). We also analyzed physiological responses of different soybean cultivars to mild Cd stress. The results indicated that mild Cd stress could inhibit soluble protein production and root vigor among individual soybean cultivars. Moreover, stress increased SOD, CAT and POD activities and MDA content in root tissues. It should be noted that the physio-biochemical indicators of low-uptake cultivars did not change significantly after exposure to mild Cd stress compared to controls. Pearson's correlation analyses showed that all physio-biochemical indicators were significantly positively associated with influx, except of root SP and biomass. PCA analysis demonstrated that root vigor was a dominant factor causing the differences in Cd tolerance among different soybean seedling cultivars. NMT is of great significance for safe utilization of contaminated soil to distinguish the cultivars with different enrichment capacity for heavy metals from different crop cultivars.

The effects of different electrode materials on seed germination of Solanum nigrum L. and its Cd accumulation in soil.

The effects of different electrode on Solanum nigrum L. seed germination were determined. The result showed that germination percentage (GP) of seeds in treatment T2 (titanium electrode) was 26.6% higher than in control (CK, without electric field). High potassium and calcium concentrations were beneficial for seed enzymatic activity in treatment T2, which could partly explain the increase in GP. Cd accumulation (µg/pot) in S. nigrum treated with any electric field was significantly higher (p<0.05) than in CK without electric field. Specifically, Cd accumulation under the treatment T3 (stainless steel electrode) was the highest both in roots and shoots; this accumulation in shoots and roots were 74.7 % and 67.4 % higher for stainless steel than in CK. This increase must have been associated with a higher Cd concentration in plants and did not exert a significant effect on the biomass. In particular, Cd concentrations in roots and shoots under stainless steel treatment were both significantly higher than in CK (p<0.05), which had to be related to the higher available Cd concentration in the soil in the middle region. Furthermore, it could be attributed to altered soil pH and other soil properties. Moreover, none of the biomasses were significantly affected (p<0.05) by different electrode materials compared to CK.