Advancing “Autonomous” sensing and prediction of the subsurface environment: a review and exploration of the challenges for soil and groundwater contamination

Environmental Science and Pollution Research - Can we hope for autonomous (self-contained in situ) sensing of subsurface soil and groundwater pollutants to satisfy relevant regulatory criteria?...     

In situ phytoremediation of heavy metal–contaminated soil and groundwater: a green inventive approach

Environmental Science and Pollution Research - The heavy metal contamination of soil and groundwater is a serious threat to environment worldwide. The survival of human being primarily relies upon...     

Microbial communities to mitigate contamination of PAHs in soil—possibilities and challenges: a review

Background, aim, and scope  

Although highly diverse and specialized prokaryotic and eukaryotic microbial communities in soil degrade polycyclic aromatic hydrocarbons (PAHs), most of these are removed slowly. This review will discuss the biotechnological possibilities to increase the microbial dissipation of PAHs from soil as well as the main biological and biotechnological challenges.     

Agricultural solid waste for sorption of metal ions: part I—characterization and use of lettuce roots and sugarcane bagasse for Cu(II), Fe(II), Zn(II), and Mn(II) sorption from aqueous medium

Sugarcane bagasse and hydroponic lettuce roots were used as biosorbents for Cu(II), Fe(II), Zn(II), and Mn(II) removal from monoelemental solutions in aqueous medium, at pH 5.5, using batch procedures. These biomasses were studied in natura (lettuce roots, NLR, and sugarcane bagasse, NSB) and modified with HNO₃ (lettuce roots, MLR, and sugarcane bagasse, MSB). Langmuir, Freundlich, and Dubinin-Radushkevich non-linear isotherm models were used to evaluate the data from the metal ion adsorption assessment. The maximum adsorption capacities (q_max) in monoelemental solution, calculated using the Langmuir isothermal model for Cu(II), Fe(II), Zn(II), and Mn(II), were respectively 24.61, 2.64, 23.04, and 5.92 mg/g for NLR; 2.29, 16.89, 1.97, and 2.88 mg/g for MLR; 0.81, 0.06, 0.83, and 0.46 mg/g for NSB; and 1.35, 2.89, 20.76, and 1.56 mg/g for MSB. The Freundlich n parameter indicated that the adsorption process was favorable for Cu(II) uptake by NLR; Fe(II) retention by MLR and MSB; and Zn(II) sorption by NSB, MLR, and NSB and favorable for all biomasses in the accumulation of Mn(II). The Dubinin-Radushkevich isotherm was applied to estimate the energy (E) and type of adsorption process involved, which was found to be a physical one between analytes and adsorbents. Organic groups such as O–H, C–O–C, CH, and C=O were found in the characterization of the biomass by FTIR. In the determination of the biomass surface charges by using blue methylene and red amaranth dyes, there was a predominance of negative charges.     

Mercury in sediment and fish communities of Lake Vänern, Sweden: recovery from contamination

The past effluents of mercury (Hg) into Lake V?nern were considerable. The consequences of, and recovery from these have been monitored through continuous measurements of mercury in sediment and fish. Mercury levels in lake sediments in the vicinity of the main source of mercury, a chloralkali plant on the northern shore, have only decreased by slightly more than a half since the mid-1970s, despite a radical decrease in effluents from the source, already during the 1960s. The mercury levels in pike (Esox lucius) have decreased to a similar extent during this time period. They are now about 30% higher in the worst affected parts of the lake compared to the least affected parts. Lower levels have been measured in perch (Perca fluviatilis) and salmonoid fish in the lake. Despite the increased presence of mercury in the sediment of Lake V?nern, the mercury levels in the fish of the lake are relatively low compared to fish in lakes situated in the same region, but not affected by any local mercury effluents. As calculated, the total fish biomass of L. V?nern holds less than 1000th of the amount of mercury contained in the upper, biologically active layers of the bottom sediment of the lake. This demonstrates the potential influence of various environmental factors and motivates continued monitoring of mercury levels in the lake in the future.     

In situ and laboratory bioassays using Poecilia reticulata Peters, 1859 in the biomonitoring of an acidic lake at Camaçari, BA, Brazil

The suitability and viability of acute in situ bioassays were investigated in the biomonitoring program of an acidic lake contaminated with sulphur residues. Responses of organisms observed in laboratory and in situ bioassays were also assessed to determine whether or not they were similar and comparable, regarding accuracy and precision. Newborn Poecilia reticulata were employed as test organisms and exposed to the same water samples under in situ and laboratory conditions. Mortality/immobility was the endpoint assessed and dead/immobile organisms were counted at various time intervals during exposure. The mean calculated LT50 values and 95% confidence intervals were 1.61 (1.36-1.87) h in the laboratory bioassays and 0.72 (0.55-0.89) h in the in situ bioassays. Statistical comparison of these values revealed a significant difference (p<0.05). In situ bioassays were more accurate than those carried out in the laboratory, demonstrating higher sensitivity and better reproduction of what occurs in nature, while laboratory bioassays were more precise.     

Atmospheric dispersion and transport within coastal regions—part I. Tracer study of power plant emissions from the Oxnard Plain

Atmospheric tracer studies were conducted using the Ormond Beach Generating Station in Ventura County during September 21 and 22, 1975. The purpose of this work was to probe the transport and dispersion of atmospheric pollutants between Ventura and Los Angeles counties. The area of interest is characterized by rough terrain and complex, coastal meteorological conditions.The sulfur hexafluoride tracer data clearly show that pollutant transport occurs from the Oxnard Plain along the Malibu coast across the Lennox area into the San Fernando Valley of the Los Angeles Basin, and along an inland route through the Thousand Oaks area into the San Fernando Valley as far east as Reseda. These tracer data were found to be consistent with air parcel trajectories constructed from available meteorological data. Pollutants emitted from the Ormond Beach Generating Station, under the test conditions, were determined to be diluted by approximately 10⁵ upon reaching the San Fernando Valley and upon reaching the Los Angeles Basin. Calculations using the Gaussian plume model yielded a close fit to the tracer data when values of the dispersion terms σ_y, andσ_z, were taken from the experimental results. Close agreement between the tracer data and the model predictions was also obtained using values of σ_y, andσ_z, from the Pasquill-Gifford atmospheric stability class which was one class less stable than that suggested to exist by wind speed and insolation measurements.     

Modeling potential ozone impacts from natural hydrocarbons—I. Development and testing of a chemical mechanism for the nox-air photooxidations of isoprene and α-pinene under ambient conditions

A chemical mechanism has been developed to predict O₃ formation in mixtures of isoprene, α-pinene and NO_x in air. The mechanism was tested against 17 outdoor smog chamber data sets from the University of North Carolina chamber and was shown to predict maximum O₃ concentrations within ±20%. Reasonably good agreement was found between the predicted and measured time-concentration profiles of other species such as NO₂, peroxyacetyl nitrate (PAN) and aldehydes. Due to the greater availability of kinetic and mechanistic data for isoprene and to the more extensive comparison of this mechanism to experimental data, the mechanism is considered more reliable for isoprene than α-pinene.     

Humic substances—part 7: the biogeochemistry of dissolved organic carbon and its interactions with climate change

Background, aim, and scope  

Dissolved organic matter, measured as dissolved organic carbon (DOC), is an important component of aquatic ecosystems and of the global carbon cycle. It is known that changes in DOC quality and quantity are likely to have ecological repercussions. This review has four goals: (1) to discuss potential mechanisms responsible for recent changes in aquatic DOC concentrations; (2) to provide a comprehensive overview of the interactions between DOC, nutrients, and trace metals in mainly boreal environments; (3) to explore the impact of climate change on DOC and the subsequent effects on nutrients and trace metals; and (4) to explore the potential impact of DOC cycling on climate change.     

In situ measurements of NO,NO2, NOy,and O3 in Dinghushan (112°E, 23°N), China during autumn 2008

Measurements of O₃, NO, NO₂, and NO_y mixing ratios were carried out at a station-Dinghushan in Guangdong province of China from Oct. 18th, 2008 to Nov. 7th, 2008. This research shows that under conditions of a strong subtropical high (temperature high, relative humidity low), on Oct. 29th, 2008 the Dinghushan station observed severe photochemical pollution. The Maximum hour average concentration of O₃ reached 128 ppbv, and the serious photochemical pollution is caused by superposition of local photochemical reaction and regional transport. The observation that NO_x ozone production efficiency (OPE) values for high O₃ pollution on Oct. 29–30th, 2008 were 10.5 and 15, which were more than the values of the city source region and lower than that of the surrounding clean areas. It means the sensitivity of O₃ generated was transitioning from VOCs limited condition to NOx-limited regime. By applying a Smog Production Model, the results show that the extent of reaction values less than 0.6 were occurred on 17 days during campaign, and 13 days for the extents of reactions more than 0.6. However, there were no data with values over 0.8, which indicates that the observation station represent a VOCs sensitive system during campaign. Analysis of the extents of reactions and wind data show that the pollution is mostly subject to a southeasterly airflow influence.     

Inventory of aerosol and sulphur dioxide emissions from India: I—Fossil fuel combustion

A comprehensive, spatially resolved (0.25°×0.25°) fossil fuel consumption database and emissions inventory was constructed, for India, for the first time. Emissions of sulphur dioxide and aerosol chemical constituents were estimated for 1996–1997 and extrapolated to the Indian Ocean Experiment (INDOEX) study period (1998–1999). District level consumption of coal/lignite, petroleum and natural gas in power plants, industrial, transportation and domestic sectors was 9411 PJ, with major contributions from coal (54%) followed by diesel (18%). Emission factors for various pollutants were derived using India specific fuel characteristics and information on combustion/air pollution control technologies for the power and industrial sectors. Domestic and transportation emission factors, appropriate for Indian source characteristics, were compiled from literature. SO₂ emissions from fossil fuel combustion for 1996–1997 were 4.0 Tg SO₂ yr⁻¹, with 756 large point sources (e.g. utilities, iron and steel, fertilisers, cement, refineries and petrochemicals and non-ferrous metals), accounting for 62%. PM_2.5 emitted was 0.5 and 2.0 Tg yr⁻¹ for the 100% and the 50% control scenario, respectively, applied to coal burning in the power and industrial sectors. Coal combustion was the major source of PM_2.5 (92%) primarily consisting of fly ash, accounting for 98% of the “inorganic fraction” emissions (difference between PM_2.5 and black carbon+organic matter) of 1.6 Tg yr⁻¹. Black carbon emissions were estimated at 0.1 Tg yr⁻¹, with 58% from diesel transport, and organic matter emissions at 0.3 Tg yr⁻¹, with 48% from brick-kilns. Fossil fuel consumption and emissions peaked at the large point industrial sources and 22 cities, with elevated area fluxes in northern and western India. The spatial resolution of this inventory makes it suitable for regional-scale aerosol-climate studies. These results are compared to previous studies and differences discussed. Measurements of emission factors for Indian sources are needed to further refine these estimates.     

Characterization of PM2.5-bound polycyclic aromatic hydrocarbons in Atlanta—Seasonal variations at urban,suburban, and rural ambient air monitoring sites

Twenty-eight polycyclic aromatic hydrocarbons (PAH) and methylated PAHs (Me-PAH) were measured in daily PM_2.5 samples collected at an urban site, a suburban site, and a rural site in and near Atlanta during 2004 (5 samples/month/site). The suburban site, located near a major highway, had higher PM_2.5-bound PAH concentrations than did the urban site, and the rural site had the lowest PAH levels. Monthly variations are described for concentrations of total PAHs (∑PAHs) and individual PAHs. PAH concentrations were much higher in cold months than in warm months, with average monthly ∑PAH concentrations at the urban and suburban-highway monitoring sites ranging from 2.12 to 6.85 ng m^?3 during January–February and November–December 2004, compared to 0.38–0.98 ng m^?3 during May–September 2004. ∑PAH concentrations were found to be well correlated with PM_2.5 and organic carbon (OC) within seasons, and the fractions of PAHs in PM_2.5 and OC were higher in winter than in summer. Methyl phenanthrenes were present at higher levels than their un-substituted homologue (phenanthrene), suggesting a petrogenic (unburned petroleum products) input. Retene, a proposed tracer for biomass burning, peaked in March, the month with the highest acreage and frequency of prescribed burning and unplanned fires, and in December, during the high residential wood-burning season, indicating that retene might be a good marker for burning of all biomass materials. In contrast, potassium peaked only in December, indicating that it might be a more specific tracer for wood-burning.     

Chronic dietary exposure to pyrolytic and petrogenic mixtures of PAHs causes physiological disruption in zebrafish—part II: behavior

In the last 10 years, behavior assessment has been developed as an indicator of neurotoxicity and an integrated indicator of physiological disruption. Polycyclic aromatic hydrocarbon (PAH) release into the environment has increased in recent decades resulting in high concentrations of these compounds in the sediment of contaminated areas. We evaluated the behavioral consequences of long-term chronic exposure to PAHs, by exposing zebrafish to diets spiked with three PAH fractions at environmentally relevant concentrations. Fish were exposed to these chemicals from their first meal (5 days postfertilization) until they became reproducing adults (at 6 months old). The fractions used were representative of PAHs of pyrolytic (PY) origin and of two oils differing in composition (a heavy fuel oil (HO) and a light crude oil (LO)). Several tests were carried out to evaluate circadian spontaneous swimming activity, responses to a challenge (photomotor response), exploratory tendencies, and anxiety levels. We found that dietary PAH exposure was associated with greater mobility, lower levels of exploratory activity, and higher levels of anxiety, particularly in fish exposed to the HO fraction and, to a lesser extent, the LO fraction. Finally, our results indicate that PAH mixtures of different compositions, representative of situations encountered in the wild, can induce behavioral disruptions resulting in poorer fish performance.     

A step forward using QuEChERS (Quick,Easy, Cheap,Effective, Rugged,and Safe) based extraction and gas chromatography-tandem mass spectrometry—levels of priority polycyclic aromatic hydrocarbons in wild and commercial mussels

A new and fully validated QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) extraction and gas chromatography–tandem mass spectrometry methodology was developed and subsequently implemented for the quantification of 16 polycyclic aromatic hydrocarbons (PAHs) in wild (from Matosinhos Beach, Portugal) and commercial (from Ria de Arousa, Spain) mussels. The method proved to be robust, precise, and accurate, with recoveries ranging from 89.2 to 111.8 %. Total sums of 16 PAHs were 52.91 and 37.58 ng/g of wet weight for wild and commercial specimens, respectively. The three- to four-ring PAHs were the most abundant, and a mixture of petrogenic and pyrolytic sources were suspected to occur in both origin areas. Although the contamination levels were below the European regulated limits, specifically for commercial mussels (this despite wild specimens are also consumed), care should be taken in terms of human health, since we are still not aware of the low-dose versus long-term effects, even more in high-risk population groups.     

Trichloroacetic acid in the vegetation of polluted and remote areas of both hemispheres—Part I. Its formation,uptake and geographical distribution

Trichloroacetic acid (TCA; CCl₃COOH) is a phytotoxic chemical. Although TCA salts and derivatives were once deployed as herbicides against perennial grasses and weeds, their use has since been banned because of their indiscriminate herbicidal effects on woody plant species. However, TCA can also be formed in the atmosphere. For instance, high-volatile C₂-chlorohydrocarbons tetrachloroethene (TECE, C₂Cl₄) and 1,1,1-trichloroethane (TCE, CCl₃CH₃) can react to TCA and other substances under oxidative conditions here. Owing to further industrialisation of Southeast Asia, South Africa and South America, a rise can be expected in the use of TECE as solvents in the metal and textile industries of these regions in the southern hemisphere (SH). The increasing emissions of this substance—together with the rise in the atmospheric oxidation potential caused by urban activities, slash and burn agriculture and forest fires in the SH—will result in the increased input/formation of TCA in the vegetation located on the lee side of these emission sources. By means of biomonitoring studies, inputs/formation of TCA related to the climatic conditions were detected at various locations in South America, Africa, and Europe.     

Biodegradation of hydrocarbons vapors: Comparison of laboratory studies and field investigations in the vadose zone at the emplaced fuel source experiment, Airbase Vaerløse, Denmark

The natural attenuation of volatile organic compounds (VOCs) in the unsaturated zone can only be predicted when information about microbial biodegradation rates and kinetics are known. This study aimed at determining first-order rate coefficients for the aerobic biodegradation of 13 volatile petroleum hydrocarbons which were artificially emplaced as a liquid mixture during a field experiment in an unsaturated sandy soil. Apparent first-order biodegradation rate coefficients were estimated by comparing the spatial evolution of the resulting vapor plumes to an analytical reactive transport model. Two independent reactive numerical model approaches have been used to simulate the diffusive migration of VOC vapors and to estimate degradation rate coefficients. Supplementary laboratory column and microcosm experiments were performed with the sandy soil at room temperature under aerobic conditions. First-order kinetics adequately matched the lab column profiles for most of the compounds. Consistent compound-specific apparent first-order rate coefficients were obtained by the three models and the lab column experiment, except for benzene. Laboratory microcosm experiments lacked of sensitivity for slowly degrading compounds and underestimated degradation rates by up to a factor of 5. Addition of NH3 vapor was shown to increase the degradation rates for some VOCs in the laboratory microcosms. All field models suggested a significantly higher degradation rate for benzene than the rates measured in the lab, suggesting that the field microbial community was superior in developing benzene degrading activity.     

Investigation of a 1000 MW smoke plume by means of a 1.064 μm lidar—I. Lidar calibration procedure from in situ aerosol measurements and vertical lidar shots

From airborne measurements on various days, average size distributions of natural aerosol particles for different heights were obtained at our rural experimental site. Using different aerosol refractive indices and a mean particle size distribution, the backscattering and extinction coefficients β and α were computed for a 1.064 μm wavelength. Assuming the mean refractive index of the aerosol particles over a rural site as equal to 1.5−0.005 i and taking into account size and concentration distributionsof aerosol particles with height, a vertical profile of atmospheric returns from the 1.064 μm laser radiation from the ground has been computed as characteristic of the site.From numerous lidar shots on various days, an average vertical profile of lidar returns was also obtained as characteristic of both the experimental site and the whole lidar system using a laser wavelength of 1.064 μm. The relationship between the atmospheric returns and lidar signals could then be set up and used as the calibration function of the lidar. In this way, distributionsof particle concentration could be monitored from lidar shots.