Kinetics, mechanism, and application of sodium persulfate activated by sodium hydroxide for removing 1,2-dichloroethane from groundwater.

1,2-Dichloroethane (1,2-DCA) is a common compound found in groundwater contaminated with organics. This compound is difficult to remove from groundwater and has the potential to inflict significant harm on human health and the environment. This study used sodium persulfate (Na2S2O8) activated by sodium hydroxide (NaOH) to remove 1,2-DCA from aqueous solutions. Density functional theory was employed to calculate the potential energy surface of the reactants, intermediates, transient states, and products to thoroughly analyze the degradation pathways. The computations were performed in combination with in situ remediation of a 1,2-DCA plume from a point source to verify the industrial applicability of the technology. The results showed the 1,2-DCA removal efficiency was impacted considerably by the Na2S2O8 dosage and the dosing sequence of Na2S2O8 and NaOH, with the mean removal ratio reaching 96.24%. A free radical reaction was the main pathway of 1,2-DCA degradation; superoxide radical (O2•-) existed stably and played a key role in the reaction, and the main transformation proceeded via a vinyl chloride intermediate. The maximum removal of 1,2-DCA reached 91.79% in the in situ remediation. The developed technology exhibits important advantages in enabling flexible control over chemical dosages, long durations of effective activity, and rapid full-cycle remediation.

Biochar performance for preventing cadmium and arsenic accumulation, and the health risks associated with mustard (Brassica juncea) grown in co-contaminated soils.

Cadmium (Cd) and arsenic (As) in co-contaminated soil can enter the human body harming health via the food chain, such as vegetables. Biochar derived from waste has been used to reduce heavy metal uptake by plant, but long-term effects of biochar under Cd and As co-contaminated soil needs to be investigated. A following mustard (Brassica juncea) was grown on co-contaminated soil amended with different raw materials of biochar including biochars pyrolyzed by lignite coal (LCB), rice straw (RSB), silkworm excrement (SEB), and sugar refinery sludge (SSB). The results showed that compared to the control, Cd and As contents of mustard shoot in SSB treatment decreased by 45-49% and 19-37% in two growing seasons, respectively, which was the most effective among 4 biochars. This probably due to SSB owns more abundant Fe-O functional groups. Biochar also altered the microbial community composition, specifically SSB increased proteobacteria abundance by 50% and 80% in the first and second growing seasons, thereby promoted the simultaneous immobilization of Cd and As in soils which may reduce the potential risks to humans. In summary, considering the long-term effects and security of SSB application on mustard, not only is it an effective waste recycle option, but it should also be promoted as a promising approach for safe vegetable production in Cd and As co-contaminated soils.

Effects of foliar applications of Brassinolide and Selenium on the accumulation of Arsenic and Cadmium in rice grains and an assessment of their health risk.

Arsenic and cadmium pose a potential health risk to human beings via rice grain consumption. In the current study, a pot experiment was conducted to evaluate the effect of Br (5 mM and 20 mM) and Se (1 mM) at rice tillering and filling stages on Cd and As accumulation in rice grain and their health risk indices. The results showed that Br or Se applications at different stages of rice improved the photosynthesis, reduce MDA content in flag leaves by 17.41%-38.65%, increased rice biomass and grain yield by 10.50%-29.94% and 10.50%-36.56%, and enhanced grain N and P uptake by 3.25%-34.90%, and 22.98%-72.05%, respectively. Applications of Br and Se effectively decreased Cd and As concentration in rice grain by 31.74%-86.97% and 16.42%-81.13% respectively. Compared to the individual treatment, combined 20 mM Br and 1 mM Se at the filling stage showed the lowest accumulation of As (0.149 mg·kg-1) and Cd (0.105 mg·kg-1) in grain, and its health risk index was below the acceptable limits (HRI < 1). This implies that application of Br and Se at the filling stage is a promising strategy for the safe production of rice in As and Cd co-contaminated regions.

In this study, foliar applications of Br and Se at the grain filling and tillering stage demonstrate their effect on As and Cd accumulation. The findings showed that Br and Se resulted in the Se concentration in grains reaching the Se-enriched level, and the accumulation of As and Cd was the lowest. Furthermore, the application of Br and Se decreased lipid peroxidation, promoted N and P uptake, and increased the rate of photosynthesis in the rice plants, which resulted in increasing rice growth and grain yield. The HRI of heavy metals was below the acceptable limits after application of Br and Se.

Effect of surfactant amendment to PAHs-contaminated soil for phytoremediation by maize (Zea mays L.).

Understanding the uptake of organic pollutants by plants is an important part of the assessment of risks from crops grown on contaminated soils. This study was an investigation of the effects of surfactants added to PAHs-contaminated soil on the uptake and accumulation of PAHs in maize tissues during phytoremediation. The accumulation of phenanthrene (PHE) and pyrene (PYR) by maize plant was not influenced significantly by the surfactant amendment to the soil. The distribution of PHE and PYR in maize tissues was not positively correlated with the corresponding lipid contents. Remarkably, the concentrations of PHE (20.9 ng g(-1)) and PYR (0.9 ng g(-1)) in maize grain were similar to or even much lower than those in some foods. Moreover, surfactants could enhance the removal of pollutants from contaminated soil during phytoremediation, which might be due to surfactant desorption ability and microbial activity in soil. The study suggests that use of maize plant with surfactant is an alternative technology for remediation of PAHs-contaminated soils.

The Effect of Pollination on Cd Phytoextraction From Soil by Maize (Zea mays L.).

A pot experiment was conducted to investigate the effects of pollination on cadmium (Cd) phytoextraction from soil by mature maize plants. The results showed that the unpollinated maize plants accumulated 50% more Cd than that of the pollinated plants, even though the dry weight of the former plants was 15% less than that of the latter plants. The Cd accumulation in root and leaf of the unpollinated maize plant was 0.47 and 0.89 times higher than that of the pollinated plant, respectively. The Cd concentration in the cob was significantly decreased because of pollination. Preventing pollination is a promising approach for enhancing the effectiveness of phytoextraction in Cd-contaminated soils by maize. This study suggested that in low Cd-contaminated soil pollination should be encouraged because accumulation of Cd in maize grains is very little and maize seeds can bring farmers economic benefits, while in high Cd-contaminated soil, inhibition of pollination can be applied to enhance phytoextraction of Cd from soil by maize plant.

Accumulation of Hydrocarbons by Maize (Zea mays L.) in Remediation of Soils Contaminated with Crude Oil.

This study has investigated the use of screened maize for remediation of soil contaminated with crude oil. Pots experiment was carried out for 60 days by transplanting maize seedlings into spiked soils. The results showed that certain amount of crude oil in soil (≤2 147 mg·kg(-1)) could enhance the production of shoot biomass of maize. Higher concentration (6 373 mg·kg(-1)) did not significantly inhibit the growth of plant maize (including shoot and root). Analysis of plant shoot by GC-MS showed that low molecular weight polycyclic aromatic hydrocarbons (PAHs) were detected in maize tissues, but PAHs concentration in the plant did not increase with higher concentration of crude oil in soil. The reduction of total petroleum hydrocarbon in planted soil was up to 52.21-72.84%, while that of the corresponding controls was only 25.85-34.22% in two months. In addition, data from physiological and biochemical indexes demonstrated a favorable adaptability of maize to crude oil pollution stress. This study suggested that the use of maize (Zea mays L.) was a good choice for remediation of soil contaminated with petroleum within a certain range of concentrations.

Comprehensive analysis reveals the underlying mechanism of arbuscular mycorrhizal fungi in kenaf cadmium stress alleviation.

Soil Cadmium (Cd) contamination has become a severe environmental problem around the world. Kenaf has great potential for utilization and phytoremediation of soil contaminated with heavy metal. Arbuscular mycorrhizal fungi (AMF) can help plants alleviate Cd stress, but the underlying mechanism remains completely unknown. In this study, kenaf was inoculated or not inoculated with AMF at cadmium concentrations of 10 mg kg-1 and 50 mg kg-1 from the seedling stage to the vigorous growth stage. The results showed that AMF symbionts improved nutrient transport efficiency and significantly improved plant growth. Additionally, AMF colonization increased cell wall polysaccharide content which help to bind Cd in the cell wall and reduced the transport of Cd to aboveground plant tissues. The increase in soil pH (6.9), total balcomycin and easily extractable balcomycin content facilitated the chelation of metal by mycorrhizal fungi and reduced the biological effectiveness of Cd. Furthermore, AMF upregulated the expression levels of key kenaf genes, such as Hc.GH3.1, Hc.AKR, and Hc.PHR1, which plays an important role in enhancing kenaf Cd tolerance. Our findings systematically revealed the mechanisms by which AMF responds to Cd stress in kenaf, inoculation of AMF with kenaf could be used to enhance the removal of Cd from soil pollution in mining areas by phytoremediation.

Facilitated transport of microplastics and nonylphenol in porous media with variations in physicochemical heterogeneity.

Nonylphenol (Noph) has garnered worldwide concern as a typical endocrine disruptor due to its toxicity, estrogenic properties, and widespread contamination. To better elucidate the interaction of Noph with ubiquitously existing microplastics (MPs) and the potential interdependence of their transport behaviors, batch adsorption and column experiments were conducted, paired with mathematical modeling. Compared with sand, MPs and soil colloids show stronger adsorption affinity for Noph due to the formation of hydrogen bonding and the larger numbers of interaction sites that are available on solid surfaces. Limited amount of soil-colloid coating on sand grains significantly influenced transport behaviors and the sensitivity to solution chemistry. These coatings led to a monotonic increase in Noph retention and a nonmonotonic MPs retention in single systems because of the altered physicochemical properties. The mobility of both MPs and Noph was enhanced when they coexisted, resulting from their association, increased electrostatic repulsion, and competition on retention sites. Limited release of MPs and Noph (under reduced ionic strength (IS) and increased pH) indicated strong interactions in irreversible retention. The retention and release of Noph were independent of IS and solution pH. A one-site model with a blocking term and a two-site kinetic model well described the transport of MPs and Noph, respectively. Our findings highlight the essential roles of coexisting MPs and Noph on their transport behaviors, depending on their concentrations, IS, and physicochemical properties of the porous media. The new knowledge from this study refreshes our understanding of the co-transport of MPs and organic contaminants such as Noph in the subsurface.

Application of Exogenous Iron Alters the Microbial Community Structure and Reduces the Accumulation of Cadmium and Arsenic in Rice (Oryza sativa L.).

Cadmium (Cd) and arsenic (As) contamination of soil has been a public concern due to their potential accumulation risk through the food chain. This study was conducted to investigate the performance of ferrous sulfate (FeSO4) and ferric oxide (Fe2O3) nanoparticle (Nano-Fe) to stabilize the concentrations of Cd and As in paddy soil. Both Fe treatments led to low extractable Cd and the contents of specifically sorbed As contents, increased (p < 0.05) the Shannon index and decreased (p < 0.05) the Simpson diversity indices compared with the control. Nano-Fe increased the relative abundances of Firmicutes and Proteobacteria and decreased the abundances of Acidobacteria and Chloroflexi. Moreover, the addition of both forms of Fe promoted the formation of Fe plaque and decreased the translocation factor index (TFs) root/soil, TFs shoot/root, and TFs grain/shoot of Cd and As. These results suggest that exogenous Fe may modify the microbial community and decrease the soil available Cd and As contents, inhibit the absorption of Cd and As by the roots and decrease the transport of Cd and As in rice grains and the risk intake in humans. These findings demonstrate that soil amendment with exogenous Fe, particularly Nano-Fe, is a potential approach to simultaneously remediate the accumulation of Cd and As from the soil to rice grain systems.

Cotransport of micro- and nano-plastics with chlortetracycline hydrochloride in saturated porous media: Effects of physicochemical heterogeneities and ionic strength.

Global production and use of plastics have resulted in the wide dissemination of micro- and nano-plastics (MNPs) to the natural environment. Potentially acting as a vector, the role of MNPs on the fate and transport of environmental pollutants (e.g., antibiotics such as chlortetracycline hydrochloride; CTC) has garnered global concern recently. Herein, the cotransport of MNPs and CTC in columns packed with uncoated sand or soil colloid-coated sand (SCCS) under different degrees of physicochemical heterogeneity and ionic strength was systematically explored. Our results show that MNPs and CTC inhibit the transport of each other when they coexist. The adsorption of CTC onto sand grains, soil colloids, and MNPs, as well as the aggregation of MNPs in the presence of CTC could be the major contributors to the enhanced retention of CTC and MNPs. In SCCS with different degrees of soil colloid coating, the adsorption of CTC on soil colloids is critical to influence the transport of CTC, and the nonlinear retention of MNPs to soil colloids is mainly attributed to the alteration of collector surface roughness by soil colloids. High ionic strength slightly facilitates CTC transport due to the competition for adsorption sites and the formation of CTC macromolecules, but significantly inhibits MNPs transport by suppressing the electrostatic double layers based on colloid stability theory. Consequently, the cotransport of MNPs and CTC is governed by the coupled interplay of collector surface roughness and chemical heterogeneity, due to the soil colloid coatings and the adsorbed CTC on the surfaces associated with solution chemistries such as ionic strength. Increased cotransport of MNPs and CTC occurred under a higher concentration of MNPs due to a larger number of adsorption sites for CTC. Our findings advance the current understanding of the complex cotransport of MNPs and antibiotics in the environment. This information is valuable for understanding contaminant fate and formulating strategies for environmental remediation due to the contamination of MNPs and co-occurring contaminants.

Decontamination of dense nonaqueous-phase liquids in groundwater using pump-and-treat and in situ chemical oxidation processes: a field test.

Groundwater remediation is difficult because of the complexity of the treatment area and the presence of various pollutants, and it is difficult to achieve using a single process. A combined pump-and-treat (P&T) and in situ chemical oxidation (ISCO) system was used to remove dense nonaqueous-phase liquids (DNAPLs) from groundwater at the field scale in this study. The underground water pH, electrical conductivity, dissolved oxygen concentration, and SO4 2- concentration were used as indirect evidence of in situ chemical reactions. Groundwater remediation using the P&T-ISCO process using 1.5% sodium persulfate and 0.03% sodium hydroxide had a remarkable effect on DNAPLs, and the DNAPL diffusion distance was much higher under pumping conditions than under natural conditions. During groundwater remediation, the pollutant concentration positively correlated with the pH, electrical conductivity, and dissolved oxygen concentration and negatively correlated with the SO4 2- concentration. In summary, P&T-ISCO can effectively accelerate DNAPL degradation to give efficient groundwater remediation.

SLC6A1-miR133a-CDX2 loop regulates SK-OV-3 ovarian cancer cell proliferation, migration and invasion.

The present study assessed the expression of solute carrier 6 member 1 (SLC6A1) in ovarian cancer (OC) tissues and evaluated the effect of silencing SLC6A1 or caudal type homeobox 2 (CDX2) on the proliferation, migration, and invasion of SK-OV-3 OC cells. The levels of caudal type homeobox 2 (CDX2) and SLC6A1 mRNA were also examined in OC SK-OV-3, OVCAR3 and A2780 cell lines. The mRNA levels of CDX2 and SLC6A1 in SK-OV-3 OC cells were assessed following transection with microRNA (miR) 133a mimics; the mRNA and protein levels of SLC6A1 were determined following the silencing of CDX2, and the mRNA expression of CDX2 was gauged following the silencing of SLC6A1. A luciferase reporter assay was performed to assess the effect of miR133a on the CDX2 and SLC6A1 3'-untranslated regions (3'UTRs). The proliferation, migration and invasion rate of SK-OV-3 cells were then examined following the silencing of CDX2 or SLC6A1. The expression of SLC6A1 was increased in OC compared with adjacent tissue. The expression of CDX2 and SLC6A1 in SK-OV-3 and OVCAR3 cells was increased compared with A2780 cells (P<0.05). The level of CDX2 and SLC6A1 mRNA in SK-OV-3 cells decreased when the cells were transected with the miR133a mimics, compared with a negative control (P<0.05). Transfection with the miR133a mimics significantly reduced the luciferase activity of reporter plasmids with the SLC6A1 or CDX2 3'UTRs (P<0.05). The mRNA level of CDX2 was decreased subsequent to the silencing of SLC6A1; the mRNA and protein level of SLC6A1 were decreased when CDX2 was silenced (P<0.05). The proliferation, migration, and invasion of SK-OV-3 cells were significantly reduced following the silencing of CDX2 or SLC6A1 (P<0.05). CDX2 may therefore be inferred to promote the proliferation, migration and invasion in SK-OV-3 OC cells, acting as a competing endogenous RNA.

Drivers and applications of integrated clean-up technologies for surfactant-enhanced remediation of environments contaminated with polycyclic aromatic hydrocarbons (PAHs).

Surfactant-enhanced remediation (SER) is considered as a promising and efficient remediation approach. This review summarizes and discusses main drivers on the application of SER in removing polycyclic aromatic hydrocarbons (PAHs) from contaminated soil and water. The effect of PAH-PAH interactions on SER efficiency is, for the first time, illustrated in an SER review. Interactions between mixed PAHs could enhance, decrease, or have no impact on surfactants' solubilization power towards PAHs, thus affecting the optimal usage of surfactants for SER. Although SER can transfer PAHs from soil/non-aqueous phase liquids to the aqueous phase, the harmful impact of PAHs still exists. To decrease the level of PAHs in SER solutions, a series of SER-based integrated cleanup technologies have been developed including surfactant-enhanced bioremediation (SEBR), surfactant-enhanced phytoremediation (SEPR) and SER-advanced oxidation processes (SER-AOPs). In this review, the general considerations and corresponding applications of the integrated cleanup technologies are summarized and discussed. Compared with SER-AOPs, SEBR and SEPR need less operation cost, yet require more treatment time. To successfully achieve the field application of surfactant-based technologies, massive production of the cost-effective green surfactants (i.e. biosurfactants) and comprehensive evaluation of the drivers and the global cost of SER-based cleanup technologies need to be performed in the future.

[Molluscicidal effect comparison between TDS and MNSC in field].

OBJECTIVE: To compare the molluscicidal effects between "Luo-wei" (TDS), a plant molluscicide in 4 percent, and metaldehyde and niclosamide (MNSC) in the field. METHODS: A natural ecological environment with Oncomelania hupensis was selected as the test area, the test concentrations of TDS and MNSC were 2.5 g/m3 and 2 ml/m3 respectively by the immersion method; the test doses of TDS and MNSC were 3 g/m2 and 2 ml/m2 respectively by the spray method; the doses of WPN in a control group were 2 g/m3 and 2 g/m2 respectively by the two methods above-mentioned. The molluscicidal effects between TDS and MNSC were compared by using the synchronous design method and parallel comparative method. RESULTS: In the TDS group, the death rate of snails was 90.70% by immersion for 24 hours, reached to 81.40% after spraying for 7 days, and there were no significant differences among the observation time points in molluscicidal effects (P > 0.05). One day after the spraying, the death rate of snails was less in the TDS group compared with that in the MSCN group (P < 0.01), but the death rates of snails were similar in both groups 3 days after the spraying (P > 0.05). In the MSCN group, the death rate of snails was 99.17% by immersion for 24 hours, reached to 66.07% by spraying for 1 day. In the WPS group, the death rate of snails was 97.15% by immersion for 24 hours, reached to 71.43% after spraying for 1 day, and there were no significant differences (both P > 0.05). CONCLUSION: TDS has a good molluscicidal activity and stable efficacy, and the molluscicidal effect of TDS is similar to that of MSCN in the filed, but the molluscicidal sensitivity of TDS is lower than that of MSCN.

Uptake and distribution of cd in sweet maize grown on contaminated soils: a field-scale study.

Maize is an economic crop that is also a candidate for use in phytoremediation in low-to-moderately Cd-contaminated soils, because the plant can accumulate high concentration of Cd in parts that are nonedible to humans while accumulating only a low concentration of Cd in the fruit. Maize cultivars CT38 and HZ were planted in field soils contaminated with Cd and nitrilotriacetic acid (NTA) was used to enhance the phytoextractive effect of the maize. Different organs of the plant were analyzed to identify the Cd sinks in the maize. A distinction was made between leaf sheath tissue and leaf lamina tissue. Cd concentrations decreased in the tissues in the following order: sheath > root > lamina > stem > fruit. The addition of NTA increased the amount of Cd absorbed but left the relative distribution of the metal among the plant organs essentially unchanged. The Cd in the fruit of maize was below the Chinese government's permitted concentration in coarse cereals. Therefore, this study shows that it is possible to conduct maize phytoremediation of Cd-contaminated soil while, at the same time, harvesting a crop, for subsequent consumption.

[Comparative evaluation of models for infectious source control of schistosomiasis in lake and marshland regions].

OBJECTIVE: To compare the effect of different models for the control of infectious source of schistosomiasis, so as to explore the control models suitable for lake and marshland regions. METHODS: The models of "replacement of cattle with machine" and "grazing prohibition and establishing fixed pasture" were implemented in 2 towns of Gong'an and Jianli counties, Hubei Province, respectively, and the data of infection situation of human and livestock, Oncomelania hupensis snail situation and the contamination status of wild faeces were collected and analyzed from 2008 to 2010. RESULTS: In 2010, for the model of "replacement of cattle with machine", the infection rate of residents in the observation group decreased by 56.82% comparing to that in 2008, the difference had a statistical significance (chi2 = 78.197, P < 0.01), and the decrease extent in the observation group was larger than that in the control group; the infection rates of cattle and snails, and the density of infected snails of the former were all decreased to 0. No wild faeces were discovered in the observation group, while 58 pieces of wild faeces were discovered but no schistosome eggs were found in these faeces in the control group. In 2010, for the model of "grazing prohibition and establishing fixed pasture", the infection rate of residents in the observation group decreased by 39.00% without a statistic significance (chi2 = 1.594, P > 0.05), and the infection rate of cattle decreased by 43.98% without a statistically significant difference (chi2 = 0.751, P > 0.05) comparing to those in 2008. The density of living snails decreased by 89.83% in the observation group, while that in the control group increased by 6.80%. A total of 11 pieces of wild faeces were collected in the observation group, with a positive rate of 18.18%, and 7 pieces were collected in the control group, all of which were negative. During the 2 years, no acute and advanced schistosomiasis patients were newly discovered. CONCLUSIONS: "Replacement of cattle with machine" and "grazing prohibition and establishing fixed pasture" are the main measures for schistosomiasis control in lake and marshland regions, the former is suitable for inner embankment regions, while the latter is suitable for the outer-embankment areas.

[Survey of causes of infected Oncomelania snails and infectious sources of schistosomiasis in marshland and lake region of Jingzhou City].

OBJECTIVE: To explore the causes of infected Oncomelania snails and the sources of infection of schistosomiasis in marshland and lake regions of Jingzhou City, so as to provide the evidence for the establishment of control strategy. METHODS: The snail environments in villages with or without cattle in Gong'an and Jianli counties, Hubei Province were selected, the snail status, infection status of people and livestock and wildlife reservoir host (mice), as well as the contamination status of wild faeces were surveyed, and the infectivity of water in investigated villages without cattle were detected by sentinel mice. The correlation between the densities of infected snails and positive faeces were tested by the rank correlation method. RESULTS: In villages without cattle, there were no positive faeces and infected sentinel mice discovered, while in the villages with cattle, 374 pieces of wild faeces were collected, the densities of wild faeces were 0.02 - 0.29 pieces/100 m2, and those of the positive ones were 0 - 0.01 pieces/100 m2, and the densities of infected snails were 0.001 - 0.040 snails /0.1 m2. The distribution of infected snails was consistent with that of the positive faeces, but the correlation coefficient between their densities had no statistical significance (r(s) = 0.123 5, P > 0.05). The average infection rates of human in villages with cattle inside embankment of Gong'an and Jianli counties were 2.87% and 1.37%, respectively, while that of the villages outside embankment of Gong'an County was 1.23%, and all the infection rates of cattle were 0. No infected wild mice were discovered. CONCLUSIONS: Human and cattle are the main sources of schistosome infection in the local areas, the possibility of wild mice as source of infection is low, and cattle is an important cause of infected snails in marshland and lake regions in Jingzhou City.