David O'Connor

Biochar application for the remediation of heavy metal polluted land: A review of in situ field trials

Polluted land is a global issue, especially for developing countries. It has been reported that soil amendment with biochar may reduce the bioavailability of a wide range of contaminants, including heavy metal(loids), potentially reclaiming contaminated soils for agricultural use. However, there have been only limited reports on the in situ application of biochar at the field scale. This review was devoted to providing preliminary scientific evidence from these field trials, based on a review of 29 publications involving field applications of biochar in 8 different countries. The data show that biochars effectiveness in reducing the impacts of pollution depends on a myriad of factors in the field, including the application time period, site-specific factors (e.g. climate, biochar dosage rate, and mixing depth), biochar feedstock type, and biochar properties. The results of this review indicate that biochar application can potentially reduce contaminant bioavailability in the field; for instance, a significant decrease (control normalized mean value=0.55) in the Cd enrichment of rice crops was observed. It was found that the use of biochar may help increase crop yields on polluted land, and thus reduce the amount of mineral fertilizer used in the field. However, in order to maximize the benefits of biochar addition, farmers need to accept that the dosage rates of mineral fertilizers should be reduced. This review also revealed that the effectiveness of biochar in mitigating pollution may decrease with time due to ageing factors, such as leaching of biochar alkalinity.

High efficiency removal of methylene blue using SDS surface-modified ZnFe 2 O 4 nanoparticles

Recent studies have shown that hazardous organic dye substances can be removed from aqueous solutions by spinel ferrite nanomaterials. We found that Sodium Dodecyl Sulfonate (SDS) surface-modified mesoporous ZnFe2O4 nanoparticles (10-50nm) have a remarkably high maximum adsorptive capacity (∼699.30mg/g) for aqueous Methylene Blue (MB) removal at T of 288K and pH of 12. Unmodified ZnFe2O4 nanoparticles suffer from particle agglomeration, which reduces surface area, thus reducing their adsorptive capacity. Here it is shown that when modified with SDS, the specific surface area increased by ∼34%. It is also shown that the anionic SDS surfactant significantly increased the electrostatic attraction to the cationic MB compound. Moreover, it was found that adsorption of MB positively correlated with the aqueous solutions pH, which is attributed to a stronger negative charge on the SDS modified ZnFe2O4 surface at high pHs. The SDS-modified ZnFe2O4 adsorption of MB fitted well with the Langmuir adsorption isotherm model, and kinetic data fitted into a pseudo-second-order model. Thermodynamic parameters indicated that the adsorption was spontaneous and exothermic in nature, and physisorption dominated the adsorption of MB. The findings of this study demonstrate the potential for enhanced removal of MB contamination from aqueous solutions by SDS-modified ZnFe2O4 nanoparticles and, therefore, the potential for them to remove cationic organic dye from wastewater.

Sustainable in situ remediation of recalcitrant organic pollutants in groundwater with controlled release materials: A review

&NA; The removal of recalcitrant organic pollutants in groundwater is a challenge being faced around the world. Achieving effective long‐term remediation of contaminated aquifers faces a variety of significant issues such as back diffusion, tailing, and rebound. In recent years, some researchers have proposed the use of controlled release materials (CRMs) as a new approach to counteracting such issues. The novelty of CRMs lies in that they release their active products slowly, over prolonged periods of time, in order to sustain in situ treatments and long‐term effectiveness. Here we review the main constituents of CRMs, analyze their production, characterization, and applications, with a focus on reaction mechanisms, effectiveness, and secondary effects. This review shows that the reactive components of CRMs most commonly involve either: (i) chemical oxidants to treat contaminants such as TCE, PCE, BTEX, and 1,4‐Dioxane; (ii) sources of dissolved oxygen to stimulate aerobic biodegradation of contaminants such as BTEX and 1,4‐Dioxane; or, (iii) substrates that stimulate reductive dechlorination of contaminants such as TCE and 1,2‐DCA. It was found that in some studies, CRMs provided sustained delivery of CRM treatment reagents over several years, and achieved complete contaminant removal. However, lower removal rates were apparent in other cases, which may be ascribed to insufficient dispersion in the subsurface. There are a relatively limited number of field‐scale applications of CRMs in contaminated land remediation. Those conducted to date suggest that CRMs could prove to be an effective future remediation strategy. Lessons learned from field applications, suggestions for future research directions, and conclusions are put forward in this review. Graphical abstract Figure. No Caption available. HighlightsLong‐term remediation of groundwater remains very challenging.Researchers have proposed the use of a variety of controlled release materials.They can release chemical oxidants, sources of dissolved oxygen, or substrates.Some controlled release materials can sustain reagent release for several years.Future research needs are put forward to help further develop these materials.

Lead-based paint in children's toys sold on China's major online shopping platforms

Lead in paint is a major public health concern and has drawn much attention from international organizations such as the World Health Organization (WHO) and the United Nations Environmental Programme (UNEP). However, there is limited research on lead-based paint, especially its use in toys, which poses an explicit health risk to vulnerable children. The present study sampled 100 different toys purchased from the three largest online shopping platforms in China: JD, Taobao (TB) and Tmall (TM). These selected toys have been sold nearly 3 million times in total, suggesting that they may have reached the dwellings of millions of children. It was found that the toys sold by JD and TM, which are considered organized sellers, had average lead concentrations of 25 mg/kg and 32 mg/kg, respectively, much lower than that of toys sold by unorganized sellers on the TB platform, at 219 mg/kg. Approximately 12% of the toys purchased from TB contained paint with total lead concentrations exceeding Chinas regulatory standard for paints in toy manufacturing, and nearly 36% of the toys purchased from TB exceeded the equivalent US regulatory standard and EU standard. These results suggest that further action is needed to verify the health and safety standards of toys sold by such unorganized sellers. Moreover, this study found that Chinas regulatory standard (90 mg/kg) based on soluble lead may underestimate the risk posed by lead in paints, and it is suggested that future regulatory thresholds for lead levels in paints for toy manufacture be based on total rather than soluble lead concentrations. The present study also explored various influencing factors on lead concentration, and found that lead concentrations were related to toy price, age group, color, and sales volume.

Lead-based paint remains a major public health concern: A critical review of global production, trade, use, exposure, health risk, and implications

Human exposure to lead (Pb) is a growing global public health concern. Elevated blood lead is thought to cause the mental retardation of >0.6 million children globally each year, and has recently been attributed to ~18% of all-cause mortality in the US. Due to the severe health risk, the international community, led by the United Nations Environment Programme (UNEP) and the World Health Organization (WHO), is actively supporting the global phase-out of lead-based paint by 2020. However, there are many significant hurdles on the way to achieving this goal. In light of the importance of the lead-based paint issue, and the urgency of achieving the 2020 phase-out goal, this review provides critical insights from the existing scientific literature on lead-based paint, and offers a comprehensive perspective on the overall issue. The global production and international trade of lead-based paints across Asia, Africa, Latin America, and Europe are critically discussed - revealing that lead-based paints are still widely used in many low and middle-income developing countries, and that the production and trade of lead-based paint is still wide-spread globally. In India, as well as many south-east Asian, African, Latin American and European countries, lead concentrations in paints often exceed 10,000 mg/kg. This will certainly pose a serious global threat to public health from surfaces painted with these products for many decades to come. The sources and pathways of exposure are further described to shed light on the associated health risk and socioeconomic costs. Finally, the review offers an overview of the potential intervention and abatement strategies for lead-based paints. In particular, it was found that there is a general lack of consensus on the definition of lead based paint; and, strengthening regulatory oversight, public awareness, and industry acceptance are vital in combating the global issue of lead based paint.