Environmental Science: Processes & Impacts blog

There are 200,000 cars fires every year in the United States. The number in the UK is even more impressive: 100,000 car fires every year (which means around 300 fires a day). Car fires are usually short, but also very intense, and release dangerous products that may not only pollute the environment, but also seriously affect the firemen tackling them. Despite the high incidence of this type of fires, very few studies have addressed the hazardous exposures firemen may be suffering.

The sampling platform used for "vacuuming" the fumes

Two researchers from Cincinnati (Ohio) have published a paper in Environmental Science: Processes & Impacts investigating the dangers of ultrafine and respirable particles released during vehicle fire suppression. They set three different cars on fire and asked a crew of firemen to suppress them with water. Meanwhile, a huge “vacuum cleaner”-like machine took samples that were later analysed by the two scientists.

The particle emissions were, like the fires, only present for a short period of time. However, the concentrations measured during the blaze were orders of magnitude bigger than the safe limits. They also found that cabin fire suppression is more dangerous than putting out just the engine compartment. The explanation might be simple: when the whole cabin is burning down, there is more fuel feeding the combustion, leading to more emissions and longer extinction times.

Another key aspect to consider is wind. Usually fire crews are trained to position themselves in an upwind and smoke-free spot, but you can’t control wind. When wind veered, particle emissions went off the chart, consequently increasing the risks.

Further studies will be carried out. In the meantime, the authors conclude that a self-contained breathing apparatus (a mask that works with compressed air generating a positive pressure inside it) should be worn throughout all the phases of extinguishing a vehicle fire. Otherwise, the hazardous vapours and particles released to the atmosphere may increase the risk of cancer in firemen.

Click on the link below to read the full article for free*

Ultrafine and respirable particle exposure during vehicle fire suppression
Douglas E. Evans and Kenneth W. Fent
Environ. Sci.: Processes Impacts, 2015, 17, 1749-1759
DOI: 10.1039/C5EM00233H

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About the webwriter

Fernando Gomollón-Bel is a PhD Student at the ISQCH (CSIC–University of Zaragoza). His research focuses on asymmetric organic synthesis using sugars as chiral-pool starting materials towards the production of fungical transglycosidase inhibitors.

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* Access is free through a registered RSC account.

The re-use of waste waters for crop irrigation is becoming an increasingly popular practice, particularly in arid, water-stressed regions of the world. A new study by researchers from the U.S. Salinity Laboratory and the Institute of Soil and Environmental Sciences at the University of Agriculture in Faisalabad, Pakistan, investigates the potential agronomic and environmental impacts this can have on farmlands, shedding light on the challenges for long-term management of water usage and crop production.

Depletion of freshwater resources is one of the most important issues facing future global development. Finite water resources are becoming increasingly stressed by an ever-growing world population and associated demand for food production. Furthermore, the increased frequency of drought in many areas resulting from climate change and resource degradation due to pollution make the task of ensuring the global population have access to enough clean water increasingly difficult. The United Nations have warned that, under existing climate change scenarios, almost half the world’s population will be living in areas of high water stress by 2030.

An increasingly popular option to cope with increased water demand for agriculture is to re-use waste water or degraded water for crop irrigation. For example, dairy lagoon wastewater has been proposed as an alternate water resource in agriculture, as this can be a plentiful source of essential nutrients and organic matter. Indeed, the Food and Agriculture Organization (FAO) produced a report presenting “an economic framework for the assessment of the use of reclaimed water in agriculture”. This could also have the additional benefit of alleviating the need for the costly and difficult storage, treatment and disposal of large volumes of waste water.

Crop irrigation system (http://www.access-irrigation.co.uk)

However, degraded water will also contain contaminants, particularly salts and heavy metals such as zinc (Zn), copper (Cu), nickel (Ni), arsenic (As), cadmium (Cd), and lead (Pb).  This could mean the benefits of using wastewater could be offset due to increasing soil salinity and accumulation of potentially bioaccumulative toxins, which could have a negative impact on crop yield and quality, as well as wider reaching environmental problems. There is therefore a need for a greater understanding of how using dairy lagoon wastewater could impact the quality of agricultural land and the surrounding environment.

While the physical, chemical, and biological characteristics of degraded waters are generally well studied, the impact of its reuse on agricultural lands over long timescales is not well understood. In this study by Dennis Corwin and Hamaad Raza Ahmad, a field-scale impact investigation of dairy lagoon water reuse on agricultural soil characteristics was carried out. This represents the first study of this kind to be conducted at this spatial or temporal scale.

In the study, soil samples were collected at locations identified from apparent soil electrical conductivity (EC) measurements, a property of soil that reflects several soil physical and chemical properties (including soil salinity, texture, water content, bulk density, organic matter, and cation exchange capacity). Samples were taken at a number of different depth increments in an agricultural area in San Jacinto, California, first in 2007 and again in 2011, to establish the effect of using dairy lagoon water blended with recycled or well water on agricultural land over a 4 year irrigation period.

Chemical analyses of soil samples were carried out to determine key characteristics of the soil. This included the salinity, pH, SAR (sodium adsorption ratio), trace elements (As, B, Mo, Se), and heavy metals (Cd, Cu, Mn, Ni, Zn). The authors note that, from an agronomic perspective, the salinity, SAR, and B are of greatest concern, while from an environmental perspective, the salinity and Cu present the greatest potential effect upon groundwater safety.

The results suggest the reuse of dairy lagoon water presented very little detrimental environmental or agronomic impacts over the 4 years of the study duration. However, there were a number of potential long-term concerns that the study raises. For example, the pH values at all soil depths were shown to decrease. Additionally, potential long-term agronomic effect of salinity, SAR, and B levels, and the long-term environmental threat of salinity and Cu was highlighted. The accumulation of Cd, Mn, and Ni in the soil profile was also observed, raising concerns over the potential for metal contaminants such as these to leach from the soil in the future.

The authors note that, while the results demonstrated the short-term (4 year) viability of dairy lagoon water reuse as an alternative water resource for agriculture, the longer-term sustainability of dairy lagoon water reuse as a viable alternative for crop irrigation requires regular monitoring of soil properties to allow adequate site-specific management.

This study demonstrates that EC-directed soil sampling can be used to monitor spatial and temporal changes in the chemical characteristics of agricultural soils due to degraded water reuse. This could help pave the way for studies over wider spatial and longer temporal scales and can help producers optimise crop yields while at the same time mitigating detrimental environmental impacts. Based on their observations, the authors provide a number of specific recommendations for achieving this most effectively.  This method has clearly delivered an extensive spatio-temporal dataset, which highlights many of the challenges for successfully managing agricultural land irrigated by degraded wastewater.

The authors highlight the broad geographical relevance and impact of this research as it concerns the viability of degraded water reuse on irrigated, agricultural lands in arid regions throughout the world (e.g. northeast China, Middle East, North and Eastern Africa, Eastern Australia, India and Pakistan), where the reuse of degraded water is a major supplemental source of irrigation water.

To read more about this research, download a copy of the manuscript for free* by clicking the link below.

Spatio-temporal impacts of dairy lagoon water reuse on soil: heavy metals and salinity
Dennis L. Corwin and Hamaad Raza Ahmad
Environ. Sci.: Processes Impacts, 2015, Advance Article
DOI: 10.1039/c5em00196j

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About the webwriter

Ian Keyte is a Doctoral Researcher at the University of Birmingham. His research focuses on the sources, behavior and fate of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere.

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* Access is free until 22/10/2015 through a registered RSC account.

Bisphenol A, phtalates, PCBs and other organic pollutants often embedded in plastics have been under the spotlight for a while. However, very few people have studied the degradation pathways of oceanic plastic debris. An article recently published in Environmental Science: Processes & Impacts critically reviews this topic.

Plastics have been widely used since the 1940s. In 2013, global plastic production reached 300 mega tonnes (50 times the Great Pyramid of Giza). We discard most of the plastic right away, within 3 years of its production. Yet, it is engineered to last for hundreds or even thousands of years. Thus, tonnes of plastic debris accumulate in the environment.

Scientists are especially concerned about plastic debris accumulating in the oceans. By 2050, 99% of all seabirds will have ingested, at least, one small piece of plastic. Nowadays, plastics represent more than 60% of all the floating debris in the oceans. All these pieces of plastic may release organic pollutants to the sea, either additives or adsorbed substance. Despite their high stability, plastics might also decompose by the action of different factors, releasing potentially dangerous chemicals.

Polymer degradation is, technically, a decline of its original properties. Usually it can be easily spotted by observing the colour changes or cracking of the surface. Small plastic particles decompose faster, due to their higher surface to volume ratio. Depending on the structure of their backbone, plastics can degrade in very different ways. Plastic with carbon-carbon backbones (i.e. PE, PP, PS, PVC) often suffer abiotic decomposition, usually initiated by UV radiation or thermal processes. Plastics with heteroatoms in their backbones (i.e. PU, PET) may also suffer abiotic decomposition, but in this case hydrolysis is the most common process. Furthermore, enzymes may also break amide and ester bonds, therefore these plastics are also exposed to biodegradation.

If you want to better understand the different degradation pathways, I strongly recommend that you go over this Environmental Science: Processes & Impacts Critical Review where all the mechanisms are carefully examined and explained.

Click on the link below to read the full article for free*:

Pathways for degradation of plastic polymers floating in the marine environment
Berit Gewert, Merle M. Plassmann and Matthew MacLeod
Environ. Sci: Processes Impacts, 2015, 17, 1513-1521
DOI: 10.1039/C5EM00207A

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About the webwriter

Fernando Gomollón-Bel is a PhD Student at the ISQCH (CSIC–University of Zaragoza). His research focuses on asymmetric organic synthesis using sugars as chiral-pool starting materials towards the production of fungical transglycosidase inhibitors.

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* Access is free through a registered RSC account.

Humic substances play an important role in the speciation of metal ions in the aquatic environment. Understanding these processes is important to ensure the safety of drinking water. In this study, Japanese researchers reveal how physiochemical properties and ion-binding behaviour of HSs can differ between surface water and groundwater environments.

Groundwater constitutes the largest reservoir of freshwater in the world, accounting for over 97% (excluding glaciers and ice caps) of all available freshwater on the planet. It is estimated that about 75% of EU inhabitants depend on groundwater for their water supply. Groundwater also plays an integral role in the hydrological cycle, crucial to the maintenance of wetlands and river flows. Maintaining the quality of groundwater resources is therefore of major environmental, social and economic importance. This requires a good understanding of the physical and chemical processes that may influence groundwater environments.

For future use of deep underground space it is necessary to monitor and protect the quality of deep groundwater. The World Health Organisation (WHO) acknowledges the importance of groundwater resources and the potential risks that poor quality groundwater can cause to human health. Indeed, the WHO has produced a guidance document, “analysing hazards to groundwater quality, assessing the risk they may cause for a specific supply, setting priorities in addressing these, and developing management strategies for their control.”

Humic substances (HSs) are a class of natural organic molecules, ubiquitous in various environments including surface and ground water, oceans, soils, and the atmosphere. HSs are known to play an important role in freshwater systems. For example HSs can effectively capture inorganic and organic contaminants due to the tendency of protons and metal ions to readily bind to the functional groups of HS ligands e.g., carboxylic and phenolic groups and to a lesser extent amine- and sulphur-containing groups. This process can therefore alter the reactivity, bioavailability, and mobility of chemical constituents in fresh water.

The physical and chemical nature of HSs is likely to differ between deep underground and surface aquatic systems, due to slower water movement and more prolonged contact with underlying rocks and dissolved/suspended components, low oxygen, and lack of sunlight. However, while some characteristics of groundwater HSs are understood, their ion binding properties over a wide range of conditions is largely unknown. Given that in many areas, deep underground space may be used in the future for such uses as geological disposal of nuclear wastes, the potential deterioration of groundwater quality, the ion binding properties of deep groundwater HSs need to be studied carefully, and mechanistic models developed to describe these processes.

This study by Takumi Saito and co-workers investigates the physicochemical and binding properties of HSs isolated from deep groundwater in a sedimentary rock formation in the Horonobe Underground Research Laboratory of the Japan Atomic Energy Agency (JAEA). Binding isotherms of protons (H⁺) and copper (Cu²⁺) were measured over a wide range of conditions by potentiometric titration and were fitted to the NICA-Donnan model and the obtained parameters were compared with average parameters for HSs from surface environments. The oxidation state and local coordination environment of Cu²⁺ bound to the HA fraction of the HSs were also assessed by X-ray absorption spectroscopy (XAS).

The results clearly indicate distinctive physical and chemical characteristics for the HSs from surface and groundwater environments. It is found that the deep ground HSs were characterised by high aliphaticity and sulphur (S) content and relatively small sizes. Differences in the binding behaviours of H⁺ and Cu²⁺ with the HSs in deepwater and surface water were also observed.

The authors discuss the differences in chemical binding behaviour with reference to the unique chemical nature of the functional groups of groundwater HSs compared with those of surface waters and how the binding sites and binding mode can change with changes in conditions (e.g. pH). X-ray absorption spectroscopy also revealed that Cu²⁺ binds to O/N containing functional groups and to a lesser extent S containing functional groups.

The study therefore demonstrates how HSs could influence freshwater resources differently in deep-ground and surface environments. Although the HSs in this study were derived from a single groundwater source, the authors suggest the outcomes can be applied or be a good starting point to estimate the degree of metal binding to HSs in sedimentary groundwater in general.

The authors also suggest these results should be examined in the future by performing similar investigations for HSs isolated from a range of different groundwater samples and for a wider range of metal ions. This would allow accurate and realistic parameter sets applicable for groundwater HSs to be developed for further modelling for a more extensive range of chemical species.

To read more about this research, download a copy of the manuscript for free* by clicking the link below.

Physicochemical and ion-binding properties of highly aliphatic humic substances extracted from deep sedimentary groundwater
Takumi Saito, Motoki Terashima, Noboru Aoyagi, Seiya Nagao, Nobuhide Fujitake and Toshihiko Ohnuki
Environ. Sci.: Processes Impacts, 2015,17, 1386-1395
DOI: 10.1039/C5EM00176E

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About the webwriter

Ian Keyte is a Doctoral Researcher at the University of Birmingham. His research focuses on the sources, behavior and fate of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere.

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* Access is free until 20/09/2015 through a registered RSC account.