Nanomaterials in sunscreens: Potential human and ecological health implications.

Inorganic nanomaterials such as TiO2 and ZnO provide significant benefits in terms of UV protection, and their use generally has increased in commercial sunscreens. However, more recently there have been concerns about their potential human and ecological health implications, mostly driven by perception rather than by formal assessments. The large and increasing body of literature on these nanomaterials indicates that in most circumstances their risk are minimal. Penetration of the human epidermis is minimal for these nanomaterials, significantly reducing the potential effects that these nanomaterials may pose to internal organs. The excess Zn ion dose is very small compared to normal dietary consumption of Zn, which is a necessary element. The levels of residual nanomaterials or released ions in public swimming pools is also low, with minimal effect in case this water is ingested during swimming or bathing. In natural environments with significant water flow due to wind and water currents, the concentrations of nanomaterials and released ions are generally well below levels that would cause effects in aquatic organisms. However, sensitive habitats with slow currents, such as coral reefs, may accumulate these nanomaterials. The number of studies of the levels and effects of nanomaterials in these sensitive habitats is very small; more research is needed to determine if there is an elevated risk to these ecosystems from the use of sunscreens with these nanomaterials.

Les nanomatériaux inorganiques, comme le dioxyde de titane (TiO2 ) et l'oxyde de zinc (ZnO), offrent des avantages significatifs en ce qui concerne la protection UV, et leur utilisation a généralement augmenté dans les protections solaires commerciales. Cependant, plus récemment, il y a eu des préoccupations concernant leurs implications potentielles sur la santé humaine et écologique, motivées principalement par la perception plutôt que par des évaluations formelles. L'importante quantité croissante de littérature sur ces nanomatériaux indique que dans la plupart des circonstances, leur risque est minime. La pénétration dans l'épiderme humain est minimale pour ces nanomatériaux, ce qui réduit significativement les effets potentiels de ces nanomatériaux sur les organes internes. La dose d'ions Zn en excès est très faible par rapport à la consommation alimentaire normale de Zn, qui est un élément nécessaire. Les niveaux de nanomatériaux résiduels ou d'ions libérés dans les piscines publiques sont également faibles, avec un effet minime dans le cas où cette eau est ingérée pendant la natation ou la baignade. Dans les environnements naturels caractérisés par un flux d'eau important en raison de courants éoliens et de courants aquatiques, les concentrations de nanomatériaux et d'ions libérés sont généralement nettement inférieures aux niveaux qui pourraient avoir des effets sur les organismes aquatiques. En revanche, des habitats sensibles à courants lents, comme les récifs coralliens, peuvent accumuler ces nanomatériaux. Le nombre d'études sur les niveaux et les effets des nanomatériaux dans ces habitats sensibles est très faible. Des recherches supplémentaires sont nécessaires pour déterminer s'il existe un risque élevé pour ces écosystèmes lié à l'utilisation de crèmes solaires comportant ces nanomatériaux.

Giving credit to reforestation for water quality benefits.

While there is a general belief that reforesting marginal, often unprofitable, croplands can result in water quality benefits, to date there have been very few studies that have attempted to quantify the magnitude of the reductions in nutrient (N and P) and sediment export. In order to determine the magnitude of a credit for water quality trading, there is a need to develop quantitative approaches to estimate the benefits from forest planting in terms of load reductions. Here we first evaluate the availability of marginal croplands (i.e. those with low infiltration capacity and high slopes) within a large section of the Ohio River Basin (ORB) to assess the magnitude of the land that could be reforested. Next, we employ the Nutrient Tracking Tool (NTT) to study the reduction in N, P and sediment losses from converting corn or corn/soy rotations to forested lands, first in a case study and then for a large region within the ORB. We find that after reforestation, N losses can decrease by 40 to 80 kg/ha-yr (95-97% reduction), while P losses decrease by 1 to 4 kg/ha-yr (96-99% reduction). There is a significant influence of local conditions (soils, previous crop management practices, meteorology), which can be considered with NTT and must be taken into consideration for specific projects. There is also considerable interannual and monthly variability, which highlights the need to take the longer view into account in nutrient credit considerations for water quality trading, as well as in monitoring programs. Overall, there is the potential for avoiding 60 million kg N and 2 million kg P from reaching the streams and rivers of the northern ORB as a result of conversion of marginal farmland to tree planting, which is on the order of 12% decrease for TN and 5% for TP, for the entire basin. Accounting for attenuation, this represents a significant fraction of the goal of the USEPA Gulf of Mexico Hypoxia Task Force to reduce TN and TP reaching the dead zone in the Gulf of Mexico, the second largest dead zone in the world. More broadly, the potential for targeted forest planting to reduce nutrient loading demonstrated in this study suggests further consideration of this approach for managing water quality in waterways throughout the world. The study was conducted using computational models and there is a need to evaluate the results with empirical observations.

EDTA functionalized magnetic nanoparticle sorbents for cadmium and lead contaminated water treatment.

Cadmium (Cd(2+)) and lead (Pb(2+)) are toxic to human beings and other organisms, and the U.S. Environmental Protection Agency (EPA) has classified both as probable human carcinogens. In this study, a regenerable magnetic ligand particle (Mag-Ligand) which includes a metal-binding organic ligand (EDTA) attached to an iron oxide nanoparticle was developed for rapid removal of Cd(2+) and Pb(2+) as well as other metals from contaminated water. Mag-Ligand showed fast removal ability for both Cd(2+) (<2 h) and Pb(2+) (<15 min) with relatively high sorption capacity (79.4 and 100.2 mg/g for Cd(2+) and Pb(2+), respectively). The removal performance of Mag-Ligand was high across a wide pH range (3-10) as well as in the presence of competitive metal ions (Ca(2+) and Mg(2+)). In addition, Mag-Ligands can be easily regenerated (washed by 1% HCl) and reused several cycles with high sorption capacity. This study indicated that Mag-Ligand is a reusable sorbent for rapid, convenient, and efficient removal of Cd(2+) and Pb(2+) from contaminated aquatic systems.

Attenuation coefficients for water quality trading.

Water quality trading has been proposed as a cost-effective approach for reducing nutrient loads through credit generation from agricultural or point source reductions sold to buyers facing costly options. We present a systematic approach to determine attenuation coefficients and their uncertainty. Using a process-based model, we determine attenuation with safety margins at many watersheds for total nitrogen (TN) and total phosphorus (TP) loads as they transport from point of load reduction to the credit buyer. TN and TP in-stream attenuation generally increases with decreasing mean river flow; smaller rivers in the modeled region of the Ohio River Basin had TN attenuation factors per km, including safety margins, of 0.19-1.6%, medium rivers of 0.14-1.2%, large rivers of 0.13-1.1%, and very large rivers of 0.04-0.42%. Attenuation in ditches transporting nutrients from farms to receiving rivers is 0.4%/km for TN, while for TP attenuation in ditches can be up to 2%/km. A 95 percentile safety margin of 30-40% for TN and 6-10% for TP, applied to the attenuation per km factors, was determined from the in-stream sensitivity of load reductions to watershed model parameters. For perspective, over 50 km a 1% per km factor would result in 50% attenuation = 2:1 trading ratio.

Magnetic pollen grains as sorbents for facile removal of organic pollutants in aqueous media.

Plant materials have long been demonstrated to sorb organic compounds. However, there are no known reports about pollen grains acting as sorbents to remove hydrophobic organic compounds (HOCs) such as pesticides, polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) from contaminated waters. We report a facile and effective method to remove HOCs from water using magnetized short ragweed (Ambrosia artemisiifolia) pollen grains. We dispersed the magnetized pollen grains in two different water samples - deionized (DI) and natural storm water to mimic real environmental conditions likely to be encountered during treatment. The magnetized pollen grains were readily separated from the aqueous media via a magnetic field after adsorption of the HOCs. We measured the adsorption of five representative HOCs (acenaphthene, phenanthrene, atrazine, diuron, and lindane) onto magnetized ragweed pollen in different aqueous matrices. We demonstrate that the adsorption capacity of the magnetized ragweed pollen can be regenerated to a large extent for reuse as a sorbent. Our results also indicate that the magnetized pollen grains are as effective as activated carbon (AC) in removing HOCs from both types of contaminated waters. The high HOC sorption of the ragweed pollen allows it to have potential remediation application in the field under realistic conditions.

Chemically enhanced primary treatment (CEPT) for removal of carbon and nutrients from municipal wastewater treatment plants: a case study of Shanghai.

With Chemically Enhanced Primary Treatment (CEPT) as the short-term process, the capacity of Bailonggang Wastewater Treatment Plant accounts for almost 25% of the total capacity of wastewater treatment in Shanghai, China. However, shortly after this plant was placed in operation in 2004, it was found that the effluent of CEPT couldn't meet the new national discharge criteria. Although the removal of phosphate is almost 80%, chemical oxygen demand (COD) and ammonia nitrogen (NH3-N) in the effluent is frequently found to exceed the standards. The primary goal of this research is to investigate the possibility of optimizing the CEPT to make it meet the discharge criteria before it is upgraded to a secondary treatment. An oxidant is adopted to remove NH3-N, and a high performance polyaluminum chloride (HP-PACl) is synthesized to enhance the removal of COD. It is found that HP-PACl improves the removal of COD, and the oxidant enhances NH3-N removal effectively. However, to meet the requirement of a newly implemented stricter discharge standard, it is necessary to upgrade this CEPT to a secondary treatment. The results of this study provide scientific evidence for the upgrade of the Bailonggang Wastewater Treatment Plant.

Improved mechanical oil spill recovery using an optimized geometry for the skimmer surface.

The primary objective of this research was to improve the efficiency of mechanical oil spill response equipment by optimizing the geometry of the oleophilic skimmer recovery surface. Another objective of this work was to study the relation between the operational variables and the oil spill recovery efficiency in a full-scale oil spill recovery test, comparing novel and conventional oleophilic drum skimmer configurations. The study showed that using the new surface pattern in the recovery unit can increase the skimmer oil recovery efficiency up to three times. The improved surface pattern was found to be efficient on oils with a wide range of viscosities, including diesel oil, which is a challenging liquid to recover due to its low viscosity. The effect of the surface pattern dimensions on the recovery efficiency was explored. Guidelines for the design of a more efficient surface geometry tailored to the properties of the recovered oil were developed.