Levels, distribution, and risk assessment of organochlorines in surficial sediments of the Red Sea coast, Egypt

The analyses of environmentally persistent pollutants like polychlorinated biphenyls (PCBs), hexachlorocyclohexane (HCH) isomers, and dichlorodiphenyltrichloroethane (DDT) and its metabolites in surficial sediment samples collected from 17 locations along with the coast of the Red Sea in Egypt were carried out using gas chromatography–mass spectrometry. Several potential organic contaminants from agricultural (e.g., DDT and its breakdown products, lindane, endrin, dieldrin, and endosulfan) and industrial (PCBs) sources were measured. The levels of 20 organochlorine pesticides (OCPs) and ten PCB congeners in sediment collected from 17 stations along ~1,200 km were investigated. Concentrations of PCBs, HCHs, DDTs, and cyclodienes ranged from 0.40 to 6.17, 0.01 to 0.09, n.d. to 0.46, and 0.08 to 0.90 ppb dry weight. Two statistical programs were applied on the data (principal component analysis, PCA, and cluster analysis, CA), and it was concluded that it is impossible to predict the distribution patterns of the OCPs in a contaminated area. Risk assessment of the organochlorines contaminated in the sediments of the studied area was investigated.     

Delineating shallow saline groundwater zones from Southern India using geophysical indicators

A geophysical survey was conducted over an industrial belt encompassing 80 functional leather factories in Southern India. These factories discharge untreated effluents which pollute shallow groundwater where electrical conductivity (EC) value had a wide range between 545 and 26,600 μS/cm (mean, 3, 901 μS/cm). The ranges of Na⁺ and Cl^? ions were from 46 to 4,850 mg/L (mean, 348 mg/L) and 25 to 10,390 mg/L (mean, 1,079 mg/L), respectively. Geoelectrical layer parameters of 37 vertical electrical soundings were analyzed to demarcate fresh and saline water zones. However, the analysis not did lead to a unique resolution of saline and fresh waters. It was difficult to assign a definitive value to the aquifer resistivity of any area. Thus, geophysical indicators, namely longitudinal unit conductance (S), transverse unit resistance (T), and average longitudinal resistivity (R _s), were calculated for identifying fresh and saline waters. Spatial distributions of S, T, and R _s reflected widely varying ranges for the saline and fresh water zones. Further, the empirical relation of formation factor (F) was established from pore-water resistivity and aquifer resistivity for fresh and saline aquifers, which may be used to estimate local EC values from the aquifer resistivity, where well water is not available.     

A pragmatic approach to study the groundwater quality suitability for domestic and agricultural usage,Saq aquifer,northwest of Saudi Arabia

The present study deals with detailed hydrochemical assessment of groundwater within the Saq aquifer. The Saq aquifer which extends through the NW part of Saudi Arabia is one of the major sources of groundwater supply. Groundwater samples were collected from about 295 groundwater wells and analyzed for various physico-chemical parameters such as electrical conductivity (EC), pH, temperature, total dissolved solids (TDS), Na⁺, K⁺, Ca²⁺, Mg²⁺, CO₃ ^?, HCO₃ ^?, Cl^?, SO₄ ^2?, and NO₃ ^?. Groundwater in the area is slightly alkaline and hard in nature. Electrical conductivity (EC) varies between 284 and 9,902?μS/cm with an average value of 1,599.4 μS/cm. The groundwater is highly mineralized with approximately 30 % of the samples having major ion concentrations above the WHO permissible limits. The NO₃ ^? concentration varies between 0.4 and 318.2 mg/l. The depth distribution of NO₃ ^? concentration shows higher concentration at shallow depths with a gradual decrease at deeper depths. As far as drinking water quality criteria are concerned, study shows that about 33 % of samples are unfit for use. A detailed assessment of groundwater quality in relation to agriculture use reveals that 21 % samples are unsuitable for irrigation. Using Piper’s classification, groundwater was classified into five different groups. Majority of the samples show Mix-Cl-SO₄- and Na-Cl-types water. The abundances of Ca²⁺ and Mg²⁺ over alkalis infer mixed type of groundwater facies and reverse exchange reactions. The groundwater has acquired unique chemical characteristics through prolonged rock-water interactions, percolation of irrigation return water, and reactions at vadose zone.     

Diversity of bacterial isolates during full scale rotary drum composting

Bacterial diversity of full scale rotary drum composter from biodegradable organic waste samples were analyzed through two different approaches, i.e., Culture dependent and independent techniques. Culture-dependent enumerations for indigenous population of bacterial isolates mainly total heterotrophic bacteria (Bacillus species, Pseudomonas species and Enterobacter species), Fecal Coliforms, Fecal Streptococci, Escherichia coli, Salmonella species and Shigella species showed reduction during the composting period. On the other hand, Culture-independent method using PCR amplification of specific 16S rRNA sequences identified the presence of Acinetobacter species, Actinobacteria species, Bacillus species, Clostridium species, Hydrogenophaga species, Butyrivibrio species, Pedobacter species, Empedobactor species and Flavobacterium species by sequences clustering in the phylogenetic tree. Furthermore, correlating physico-chemical analysis of samples with bacterial diversity revealed the bacterial communities have undergone changes, possibly linked to the variations in temperature and availability of new metabolic substrates while decomposing organics at different stages of composting.     

Correction to: Municipal wastewater viral pollution in Saudi Arabia: effect of hot climate on COVID-19 disease spreading

Environmental Science and Pollution Research -     

The semiochemically mediated interactions between bacteria and insects

In natural environment, semiochemicals are involved in many interactions between the different trophic levels involving insects, plants and hosts for parasitoids or prey for predators. These volatile compounds act as messengers within or between insect species, inducing particular behaviours, such as the localisation of a source of food, the orientation to an adequate oviposition site, the selection of a suitable breeding site and the localisation of hosts or prey. In this sense, bacteria have been shown to play an important role in the production of volatile compounds which ones act as semiochemicals. This review, focusing on the semiochemically mediated interactions between bacteria and insects, highlights that bacterial semiochemicals act as important messengers for insects. Indeed, in most of the studies reported here, insects respond to specific volatiles emitted by specific bacteria hosted by the insect itself (gut, mouthparts, etc.) or present in the natural environment where the insect evolves. Particularly, bacteria from the families Enterobacteriaceae, Pseudomonaceae and Bacillaceae are involved in many interactions with insects. Because semiochemicals naturally produced by bacteria could be a very interesting option for pest management, advances in this field are discussed in the context of biological control against insect pests.     

A lysimeter experimental study and numerical characterisation of the leaching of incinerator bottom ash waste

Incinerator bottom ash (IBA) is a residual produced from incinerating municipal solid waste. In the past, IBA presented a big waste disposal problem; however, various recycling approaches have been adopted in recent years to mitigate this problem, as well as to provide a useful alternative to using primary aggregate resources. The use of IBA as an alternative to conventional aggregates in different civil engineering construction applications helps to conserve premium grade aggregate supplies; however, when IBA is in contact with water in the field, as a consequence of precipitation events or changes in water table, elements, such as salts and heavy metals, may be released to the soil and ground water. In this work, IBA waste was mixed with limestone aggregate to produce a blend with acceptable mechanical properties and minimum environmental risks for use as road foundation. The study focused on evaluating potential environmental impacts of some constituents, including sulphate, chloride, sodium, copper, zinc and lead in IBA blends using a lysimeter as a large scale leaching tool. Moreover, a specific scenario simulating field conditions was adopted in the lysimeter to assess the potential impact of changing conditions, such as IBA content in the blend, liquid to solid ratio (L/S) and pH value, on long-term release of heavy metals and salts. Then, numerical modelling was used to predict the release of the aforementioned constituents from IBA based on initial measurement of intrinsic material properties and the kinetic desorption process concept. Experimental results showed that zinc and lead were released in very low concentrations but sodium and sulphate were in high concentrations. The control limestone only blend also demonstrated low release concentrations of constituents in comparison to IBA blends, where constituent concentrations increased with increase in IBA content. Experimental results were compared with numerical results obtained using a non-equilibrium desorption model. Good agreement was found between the two sets of data.     

Blood nickel and chromium levels in association with smoking and occupational exposure among head and neck cancer patients in Tunisia

Chronic exposure to chromium (Cr) and nickel (Ni) has long been recognized as being capable to increase head and neck cancer (HNC) incidence among exposed human populations. This study represents the first biomonitoring of Cr and Ni exposure in Tunisia and focuses on a possible association with HNC risk. The aim of the present study was to evaluate the concentrations of Cr and Ni in the blood of HNC patients and controls. Metals blood levels of 169 HNC patients and 351 controls were determined using a Perkin-Elmer Analyst 800 Atomic Absorption Spectrometer. Mean blood levels of Cr and Ni in HNC cases (52.15 and 111.60 μg/L, respectively) were significantly higher than those of controls (37.04 and 30.50 μg/L, respectively). Cases’ blood levels of Cr and Ni were significantly higher than those of controls after controlling for the other risk factors of HNC, including smoking, shisha consumption, occupational exposure, and nearby environment (P?<?0.05). Among these risk factors, smoking and occupational exposure presented the most significant association with HNC (odds ratio (OR)?=?6.54 and 7.66, respectively, P?<?0.001). Cr and Ni levels in blood sample of cases and controls that are smoker/occupationally exposed were higher than that of non-smoker/non-occupationally exposed (P?<?0.05). Smokers who are occupationally exposed present the most significant association with HNC (OR?=?25.08, P?<?0.0001). High levels of blood Cr (OR?=?2.09) and high levels of blood Ni (OR?=?8.87) were strongly associated with HNC after other potential confounders were controlled (P?=?0.004 and P?<?0.0001, respectively). This study suggested a potential role of Cr and Ni in the mechanism of HNC development.