Remediation actions by a risk assessment approach: a case study of mercury contamination

The risk assessment procedure for identifying the remediation actions which may be adopted at a mercury contaminated site, when the plants are upgraded in the future, is proposed. The potentially active exposure/migration pathways in the future arrangement of the area will be due to Hg contaminated subsoil as a primary source (vapor inhalation and groundwater leaching) and to groundwater as a possible secondary source (transport to the point of compliance). The data of mercury concentration in the soil were acquired through environmental monitoring campaigns, and were processed to establish the three-dimensional distribution of contamination in subsoil, to locate sources and to define their geometrical and chemical characteristics. Speciation tests of mercury in the soil indicated that the most abundant species present were poorly leachable under the site-specific environmental conditions, confirming the coefficient distribution value obtained by the leaching tests. Analytical and numerical fate and transport modeling tools were used to locate digging zones in the contaminated subsoil, so as to reduce the possible groundwater contaminant loading and to avoid the down-gradient exceeding the concentration limit according to regulations. Remediation actions additional to civil works were required, which consists of soil digging within one contamination source, for about 22,200 m3 of soil. In order to evaluate the Hazard Index (HI) for human receptors due to Hg vapor inhalation, the air concentration of volatile mercury at the exposure point was estimated, based on direct measurements carried out at the site. Simulation gave HI values below 1 for all tested scenarios, suggesting that public health is protected without any additional actions to the already scheduled plant upgrading and digging for groundwater protection

Bisphenol A, nonylphenols, benzophenones, and benzotriazoles in soils, groundwater, surface water, sediments, and food: a review

Contaminants of emerging concern (CECs) are not commonly monitored in the environment, but they can enter the environment from a variety of sources. The most worrying consequence of their wide use and environmental diffusion is the increase in the possible exposure pathways for humans. Moreover, knowledge of their behavior in the environment, toxicity, and biological effects is limited or not available for most CECs. The aim of this work is to edit the state of the art on few selected CECs having the potential to enter the soil and aquatic systems and cause adverse effects in humans, wildlife, and the environment: bisphenol A (BPA), nonylphenol (NP), benzophenones (BPs), and benzotriazole (BT). Some reviews are already available on BPA and NP, reporting about their behavior in surface water and sediments, but scarce and scattered information is available about their presence in soil and groundwater. Only a few studies are available about BPs and BT in the environment, in particular in soil and groundwater. This work summarizes the information available in the literature about the incidence and behavior of these compounds in the different environmental matrices and food. In particular, the review focuses on the physical-chemical properties, the environmental fate, the major degradation byproducts, and the environmental evidence of the selected CECs

BIOELECTROCHEMICAL SYSTEM FOR REMOVING HEXAVALENT CHROMIUM FROM WATERS

BES include a set of technologies that exploit the ability of certain microorganisms to use electrodes as the electrons acceptors/donors and to catalyze redox reactions in order to promote a flow of electrons. In the present study, we have assessed the possibility to remove Cr(VI) in a biocathodic chamber of a dual-chamber (2C) Microbial Electrolysis Cell (MEC) with cathode as the sole electron donor. The cathode was first put into the anodic compartment of a 2CMicrobial Fuel Cell (MFC) inoculated with sludge from an anaerobic digester. After the acclimation period, the electrode was transferred into the cathodic chamber to work at -300 mV (vs. Standard Hydrogen Electrode - SHE) as the biocathode in a Cr(VI)-reducing MEC with 2000 μg Cr(VI)/L. The acclimation phase in the 2C-MFC allowed to shorten the time for the electroactive-biofilm growth, and to increase the efficiency of the Cr(VI)-reducing MEC. The bioelectrochemical system ensured higher removal efficiency than the pure chemical process

BISPHENOL A AND NONYLPHENOL TRANSFER TO VEGETABLES CULTIVATED ON CONTAMINATED SOIL

A research program, financed by the Italian Ministry of Education, University and Research, started early 2013 to investigate the occurrence and fate of selected emerging contaminants in soil, water, sediments and food in Italy, in order to assess health risks and to develop control measures. Bisphenol A (BPA) and Nonylphenol (NP) are both emerging pollutants listed as endocrine disrupters, for which diet seems the major exposure route for humans. In this specific work, the transfer of BPA and NP to edible vegetables cultivated on polluted soil was investigated. Lettuce and tomatoes were selected due to their high worldwide per capita consumption rates. Plants were cultivated in pots filled with agricultural soil artificially contaminated with BPA or 4-NP and in pots with uncontaminated soil (blank pots). After filling (time T0), the pots were located in greenhouses, daily monitored and periodically watered. Lettuce was cultivated for about 55 d (T1). Tomatoes were collected at different times (T1 = 52 d, T2 = 66 d, T3 = 79 d and T4 = 89 d) due to the different ripening time of the fruits. Soil samples were also collected, by coring the soil next to the plants. Commercial pre-washed lettuce, raw lettuce and tomatoes from conventional farming and organic farming were also bought at a local store and analyzed for BPA and 4-NP quantification. Contamination of soil with BPA resulted in a very rapid (2 days) degradation of this contaminant and the production of two byproducts (p-HBA and p-HAP). No BPA was found at all sampling times in the vegetables from either the blank pots or the BPA pots. p-HBA was found at high concentrations in the vegetables from the contaminated pots; the concentration in the lettuce produced in the experiment was higher than in the commercial samples. Though p-HAP was found in some soil samples from the contaminated pots, it was never found in the vegetables. As for 4-NP pots, a huge decrease in 4-NP concentration occurred in the contaminated soils between T0 and T1. Vegetables from the contaminated pots had high 4-NP concentrations. p-Cresol was the most frequently detected byproduct, which was found in the vegetables from the contaminated pots at concentrations higher than in the commercial samples. Phenol was found in the tomatoes from the contaminated pot, at concentrations higher than in the commercial tomatoes

Transfer of Benzophenones from Soil to Plants

Benzophenones (BPs) include different compounds whose molecular structure is based on diphenyl ketone (benzophenone, BP). Some benzophenones have been reported to have estrogenic activity and some compounds have been classified as possibly carcinogenic to humans. Specific studies should be carried out about possible pollution of soils due to the use of biosolids and/or treated wastewater in agriculture practices, in particular to understand the transport of BPs to the edible parts of plants and risk for humans due to their consumption. In this work, the transfer of BP and BP-3 to edible vegetables cultivated on polluted soil was investigated. Lettuce and tomatoes were selected due to their high worldwide per capita consumption rates. Plants were cultivated in pots filled with agricultural soil artificially contaminated with BP or BP-3 and in pots with uncontaminated soil (blank pots). At the beginning of tests (time T0) three soil samples from each pot were collected and analyzed. Lettuce was cultivated for about 55 d; at the end of this period (time T1), the edible part of each plant was collected and analyzed. Tomatoes were collected at different times (T1 = 54 d, T2 = 70 d, T3 = 83 d and T4 = 92 d) due to the different ripening time of the fruits; in the BP-3 pot, tomatoes could be collected only at time T3 and T4, because no ripe fruits were available before. Soil samples were also collected at the different times, by coring the soil next to the lettuce plant roots or the plants from which tomatoes had been grabbed. Commercial pre-washed lettuce, raw lettuce and tomatoes from conventional farming and organic farming were also bought at a local store and analyzed. BP concentrations in the contaminated soils remained constant over time except for the tomato pot from time T3, while BP-3 concentrations decreased over time. As for the vegetables, BP (at T2) and BP-3 (at T3 and T4) in tomatoes were higher than in the Blank. BP and BP-3 concentrations found in the vegetables cultivated in this study were similar to those measured in the commercial vegetables, except for BP-3 in tomatoes at T3

Do Emerging Contaminants Translocate from Soil to Lettuce?

Bisphenol A (BPA), nonylphenol (4-NP), benzophenone (BP), and benzophenone-3 (BP-3) are emerging contaminants (ECs) having the potential to enter the soil and food, and cause adverse effects in humans, wildlife, and the environment. In order to understand the potential translocation to edible vegetables and risk for humans due to their consumption, lettuce was cultivated for 54 d on artificially polluted soils and uncontaminated (blank) soil. BPA contamination in soil resulted in a very rapid degradation and no BPA was found in the vegetable. Lettuce from the 4-NP contaminated pot had higher concentrations compared to the vegetables from the blank pot; p-cresol was the most frequently detected 4-NP degradation product. BP and BP-3 concentrations in lettuce from the contaminated pot and the uncontaminated pot were similar

An integrated human health risk assessment framework for alkylphenols due to drinking water and crops' food consumption

The increasing overexploitation and pollution of fresh water resources are potential threats for public health, causing cross-contamination among the interconnected environmental compartments (freshwater, soil, crops). In particular, contaminants of emerging concern (CECs) originating from anthropic activities are not completely removed by wastewater treatments plants. This leads to their presence in drinking water (DW) sources, soil and crops intended for human consumption due to discharges of treated wastewater in surface waters and direct wastewater reuse practices. Currently, health risk assessments are limited to single exposure sources without considering the multiple exposure routes to which humans are subjected. For instance, among CECs, bisphenol A (BPA) and nonylphenol (NP), respectively, adversely affect immune and renal systems and have been frequently detected in DW and food, their major exposure sources for humans. Here, an integrated procedure is proposed to quantitatively assess health risk from CECs due to multiple exposure from the consumption of both DW and food, considering the relevant inter-connected environmental compartments. This procedure was applied to BPA and NP to calculate their probabilistic Benchmark Quotient (BQ), showing its potential in quantitatively apportioning the risk between contaminants and exposure sources, and its use as a decision support tool for prioritizing mitigation measures. Our results indicate that, even though the human health risk due to NP is not negligible, the estimated risk due to BPA is significantly higher, and the consumption of food from edible crops determines a higher risk compared to tap water. Hence, BPA is undoubtedly a contaminant to be prioritized, especially through mitigation actions aimed at its prevention and removal from food

In Situ Hexavalent Chromium Reduction by Injection of Organic Substrates in the Aquifer

Among the innovative technologies for in situ remediation of hexavalent chromium in groundwater, bio-induced reduction is under investigation. In this process the reduction of Cr(VI) is stimulated by a strongly reducing environment, created by the injection of organic substrates that are rapidly degraded by autochthonous heterotrophic microorganisms. Tests were performed at the laboratory scale to investigate the behavior of two different organic substrates from food industry (permeate from cheese whey ultrafiltration and a waste from the brewing process), in terms of dissolved Cr(VI) abatement and kinetics, also as a function of the initial Cr(VI) concentration (5000 or 10000 μg/L). The tests showed that, under proper conditions, very low Cr(VI) concentrations (1.3 g/L) and removal efficiency up to about 100% can be obtained after 36 d incubation

The effects of electric, magnetic and electromagnetic fields on microorganisms in the perspective of bioremediation

Some studies show how exposure to fields can enhance or reduce cell activity, with possible applicative consequences in the field of biotechnology, including biological techniques for depollution. In order to identify full-scale conditions that are suitable and potentially applicable for use in electromagnetic fields to stimulate and accelerate bioremediation processes, this paper offers an examination of the scientific literature that is available on the effects of fields on microorganisms, and a critical analysis of it. The biological effects at times contrast with each other

Soil Gas Sampling for Identification of CAHS Sources in Groundwater: A Case Study

Groundwater contamination studies involving possible multiple sources of contaminants poses a considerable challenge. When the contaminants of interest are chlorinated aliphatic compounds (CAHs), soil gas sampling can be precious for focusing site investigations. Soil gas monitoring at a former industrial site in Milan in an area of diffuse groundwater contamination demonstrates the usefulness of soil gas data together with groundwater and soil data for the correct reconstruction of the conceptual site model. Repeated gas sampling at different locations and depths provided data on the spatial and vertical concentration gradients of contaminants, which were useful to distinguish between background and local sources. In all the soil gas monitoring wells, CAH concentrations increased with depth, clearly indicating groundwater as the source of vapors at the site. Moreover soil gas and groundwater concentrations showed a similar pattern, with the highest soil gas concentrations recorded in the probes located in the area overlying highly contaminated groundwater. The data suggested groundwater contamination at the site was to be traced to the diffuse plume, but a discernible plume of PCE appeared to originate from a local off-site cross gradient source, which was responsible for the high PCE concentrations in the eastern portions of the site