China
Africa
Explore chapters and articles related to this topic
Nature's Response to Land Contamination
Published in Daniel T. Rogers, Environmental Compliance Handbook, 2023
Other VOC compounds, such as benzene, toluene, ethyl benzene, and xylenes (BTEX), are not typically as persistent in the environment and have been known to biodegrade in a few months to years if conditions are favorable (Rogers 1995; USEPA 1996a). The VOC compound MTBE is persistent in the environment. Its relatively high solubility in water and low sorptive properties compared to other common VOC contaminants have resulted in significant MTBE-contaminated groundwater supplies at many urban locations throughout the United States (USGS 2006a). The trihalomethane VOCs include chloroform, bromoform, bromodichloro-methane, and dibromochloromethane. These compounds have been detected in the groundwater of many US aquifers (USGS 2006a). Trihalomethanes have high relative vapor pressures and commonly evaporate quickly when in contact with the atmosphere. Therefore, exposure to trihalomethanes is of special concern during showering and washing (ATSDR 1997a, 2005a). They degrade by photolysis when exposed to direct sunlight and can also be degraded by microorganisms (ATSDR 1997a, 2005a).
Chemistry of Contaminants
Published in Daniel T. Rogers, Environmental Compliance Handbook, 2023
Other VOC compounds, such as benzene, toluene, ethyl benzene, and xylenes (BTEX), are not typically as persistent in the environment, especially in air, and have been known to degrade in a few hours to a few months to years if conditions are favorable (Rogers 2020; USEPA 1996a). The VOC compound MTBE is persistent in the environment. Its relatively high solubility in water and low adsorptive properties compared to other common VOC contaminants have resulted in significant MTBE-contaminated groundwater supplies at many urban locations throughout the United States (USGS 2006a). The trihalomethane VOCs include chloroform, bromoform, bromodichloro-methane, and dibromochloromethane. Trihalomethanes have high relative vapor pressures and commonly evaporate quickly when in contact with the atmosphere. They degrade by photolysis when exposed to direct sunlight and can also be degraded by microorganisms (ATSDR 1997a, 2005b).
Computational Evaluation of Third-Order Optical Nonlinearities
Published in Hari Singh Nalwa, Seizo Miyata, Nonlinear Optics of Organic Molecules and Polymers, 2020
static and dynamic polarizability and hyperpolarizabilities for fluoroform CHF3, chloroform CHCI3, bromoform CHBr3, and iodoform CHI3. All dynamic quantities were calculated at the optical wavelength ?. = 694.3 nm except CHI3 where y(THG) was obtained at 911.3 nm. The frequency-dependent second hypcrpolarizabilities were calculated for optical Kerr effect (OKE) y ( " (">; 0, 0, ?), DC-electric-field- induced second harmonic generation (EFISH) y("2?; 0, ?, ?). third-harmonic generation (THG) ?, ?, ?), intensity-dependent refractive index (IDRI) y(~?; ?, ?, "?) and DC-electric-field- induced optical rectification (EFIOR) y("0; 0, ?, "?). Both a and yincrease in going from fluoroform to iodoform; in particular, yincreases by 2 orders of magnitude. The dispersion of a and yincreases as the atomic number of the halogen atoms in the haloform increases and the dispersion of yin CHI3 increases with an increase in the applied optical frequency. The dispersion of y(EFISH) in CHI3 was larger than that in OKE or IDRI. The CHI3 shows large optical nonlinearities because of polarizable lone-pair electrons of the iodine atoms.
Studies on low-grade coking coal characterisation, flotation response and process optimisation
Published in International Journal of Coal Preparation and Utilization, 2023
Gayatri Hazare, Soumya Sucharita Pradhan, Nilima Dash, Ranjan Kumar Dwari
Sink and float tests are carried out using 1.5 specific gravity liquid comprised of acetone and bromoform with different size fractions of sample two coal. The physical segregation characteristics of a sink and float product are shown in Fig. 10. The result indicates that for different particle sizes, the ash content of float and sink fraction varies between 7.5–8% and 78–88%, respectively. The yield of float and sink fractions varies between 54–63% and 36–46%, respectively. The sink float studies indicate that 89% combustible is possible to recover. A point that could take here is that at least 89% of the carbonaceous material should have been reported in the froth phase. However, at 0.53 kg/ton and 1.32 kg/ton collector dosage, the combustible recovery for sample 2 is 49% and 84%, respectively. The combustible recovery for sample 1 at 0.53 kg/ton and 1.32 kg/ton collector dosage is 84% and 88.47%, respectively. Another point is that the yield of concentrate at a lower collector dosage for sample two is much less than for sample one and coarse size fraction. It may be due to maceral composition, liberation and surface oxidation.
Predicting health risk from exposure to trihalomethanes in an Olympic-size indoor swimming pool among elite swimmers and coaches
Published in Journal of Toxicology and Environmental Health, Part A, 2019
Pedro Gouveia, Fátima Felgueiras, Zenaida Mourão, Eduardo De Oliveira Fernandes, André Moreira, Marta Fonseca Gabriel
Swimming pool water is the obvious source of THM contributing to indoor air; it is, thus, expected that the pattern of individual THM quantified in the pool surrounding air is correlated with the individual THM levels present in the swimming pool water. From the results presented, this relationship was valid for chloroform and bromoform, but not entirely for DCBM and CDBM. Differences in the sensitivities of the quantification methodologies and high rate of volatilization might exceed compound formation rates and thus not enable accumulation in water. This might explain the detection of DCBM and CDBM in some of the air samples but not in pool water, which is the apparent source for these compounds. The THM content of all the water samples was in compliance with the maximum concentration of total THM in swimming pool water recommended by the Portuguese Health Authority (DGS, Directorate-General of Health – Portuguese Ministry of Health 2009). Previously, Maia et al. (2014) showed that water samples collected from 4 out of the 27 swimming pools in Portugal exceeded the recommended limit and, similar to our results, chloroform was the only THM detected.
Species-specific interaction of trihalomethane (THM) precursors in a scaled-up distribution network using response surface methodology (RSM)
Published in Environmental Technology, 2018
Sajida Rasheed, Imran Hashmi, Jong. K. Kim, Qizhi Zhou, Luiza C. Campos
A water distribution network (DN) acts as a large chemical and biological reactor where numerous reactions take place. Chlorination of drinking water containing natural organic matter (NOM), mainly humic substances, leads to disinfection of by-products’ formation [1,2] such as total trihalomethane (TTHM), that is, chloroform (CHCl3), bromodichloromethane (BDCM) (CHCl2Br), dibromochloromethane (DBCM) (CHClBr2) and bromoform (BF) (CHBr3). The later three brominated trihalomethanes (Br-THMs) are produced by reaction of hypo-bromite with humic acid (HA) [3]. Hassani et al. [4] showed that higher TTHM concentrations formed within DN, while El-Shafey et al. [5] reported that 45% of TTHMs were formed in treatment plant; the rest formed in pipelines. The carcinogenic and non-carcinogenic health effects showed an association between ingestion of chlorinated water and esophagus, pancreas, urinary tract, stomach, colon and rectal cancers and reproductive/developmental anomalies in laboratory animals [6–9]. Therefore, recommended TTHM concentration in drinking water is set to be ≤80 µg/L by World Health Organization (WHO) [10]. This has led to the monitoring of their presence in drinking water for regulatory compliance, health risk assessment, epidemiological evaluation and water quality control purposes so measures may be taken to minimize or eliminate their presence. Moreover, as bromide ion concentration is not lowered by conventional drinking water treatment processes [11], the effect of Br− concentration on trihalomethane formation potential is an important area of study.