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Chemical Factors
Published in Michael J. Kennish, Ecology of Estuaries Physical and Chemical Aspects, 2019
Calcium and magnesium are two of the major cations in rivers, estuaries, and oceans (Tables 2 and 4). Calcium typically is the most abundant cation in river water, but is less abundant than sodium and magnesium in seawater. River water contains calcium and magnesium in association with bicarbonate; as alluded to previously, calcium gets actively removed from estuarine and oceanic waters by biological processes (e.g., shell secretion by organisms). Magnesium removal from marine waters takes place during the formation of the minerals dolomite, high magnesium calcite, and chlorite (from the transformation of montmorillonite), although these processes may not be quantitatively important.26 The coprecipitation of magnesium with calcium carbonate by shell-secreting organisms also extracts magnesium.
Development of an algorithm for effective design of respirator half-masks and encapsulated particle filters
Published in International Journal of Occupational Safety and Ergonomics, 2022
Serhii Cheberyachko, Yurii Cheberyachko, Mykola Naumov, Oleg Deryugin
The cross-sectional area of the test chamber is – 0.4 m2, as required by the procedure according to the requirements of Standard No. EN 13274-8:2005. The concentration of dolomite dust was provided equal to 500 ± 50 mg/m3. The time of dust contamination was determined by the achievement of the finite pressure difference at the half-masks in accordance with the requirements of Standard No. EN 143:2000/A1. Using the ejector 3 and the compressor 1 at an air flow rate of 60 m3/h, the dolomite dust was fed from the dust generator 10 through the diffuser 4 and dust distributor 11 to the test chamber 13. The diffuser and distributor in the test stand design ensure uniform distribution of dust and air flow over the chamber height. The air flow in the chamber is controlled by the flow meter 6. To remove dust from the chamber and protect the environment, the exhaust fan 7 with the cyclone 5 is installed.
Geochemical assessment of groundwater contaminants and associated health risks in the Shivalik region of Punjab, India
Published in Toxin Reviews, 2021
Sunil Mittal, Ravishankar Kumar, Prafulla Kumar Sahoo, Sunil Kumar Sahoo
The Ca/Mg ratio was <1 in 75% samples which indicated the dominancy of calcite while dolomite (Ca/Mg ∼1 to >1; 17%) and silicate (Ca/Mg >2; 8%) weathering were present in 25% samples. The significant presence of Ca and Mg in groundwater in the Shivalik region is attributed to weathering of gypsum and carbonate-bearing rocks (Kumar et al.2007). Moreover, feldspars have been reported as the sources of Na and K in this region (Singh et al.2011a,b). Further, multivariate analyses were performed to study source apportionment pattern and interaction among groundwater quality parameters.
Evaluation of trace elements concentration in surface sediments of Parishan International Wetland (Fars Province, SW Iran) by using geochemical and sedimentological analysis
Published in Toxin Reviews, 2021
Amir Karimian Torghabeh, Sayed Fakhreddin Afzali, Ashkan Jahandari, Mohamad Hosein Mahmudy Gharaie, Omar Ali Al-Khashman
The mean EF levels are the following (Figure 3): As with (1.54), Cr (1.73), Ni (2.19), Zn (2.75), Pb (4.87), Cu (7.5), Cd (8.44), and Sr (165.64). In this study, the average EF level for As and Cr, being lower than 2, represent a minimal enrichment on those elements, EF values of Pb, Ni, and Zn, among 2 and 5, denote a modest enrichment and the EF values of Cd and Cu (2–20) indicate a significant enrichment. The Strontium EF values, higher than 40, indicate extremely high enrichment. Sr is an alkaline earth metal and due to its geochemistry similar to Calcium; it can substitute Ca in the carbonate minerals, such as calcite or dolomite, to form strontianite (SrCO3). On the other hand, XRD analysis of surface sediments does not show strontianite. Shabafrooz et al. (2010) reported that mean concentration of Sr in the Sedimentary formation of study is range 90–890 mg/kg. Also, Karimian Torghabeh et al. (2018) reported extremely high enrichment of Sr in the Maharlou Lake surface sediments (nearest lake to the studied area) and conducted that Sr was derived from sedimentary host rocks. Hence, the extremely high enrichment of Sr in collected sediment samples is not surprising and shows that carbonate catchment source host rocks are major source of Sr in the surface sediments. Therefore, we suggest that this extremely high enrichment is due to the high concentrations of strontium in the carbonate-bearing catchment source host rocks (Karimian Torghabeh et al.2018). The mean EF values for all the studied heavy metals except Sr were >1.5 in the sediments of the lake, suggesting an unnatural impact on trace elements concentrations in the Parishan Lake. The highest EF values were detected at S1, S2, S3, and S6, close to the Ayaz Abad and Zavali villages’ farmlands with abundant agricultural wastewater discharges, but also at S8, near agricultural activities of Nargeszar, Qaleh Mirzaei, Qalat Niloo, and Deh Pagah villages, and S4, near to the Kazerun-Baladeh road.