Unravelling the photoprotective effects of freshwater alga Nostoc commune Vaucher ex Bornet et Flahault against ultraviolet radiations

Environmental Science and Pollution Research - Several studies have suggested the direct relationship between skin complications, air pollution, and UV irradiation. UVB radiations cause various...     

Dye decomposition and air de-pollution performance of TiO2/SiO2 and N-TiO2/SiO2 photocatalysts coated on Portland cement mortar substates

Environmental Science and Pollution Research - In this study, the newly synthesized TiO2 and N doped TiO2 clusters were added to silica sol to synthesize N-TiO2/SiO2 composites via the...     

Polyaniline films for efficient removal of aromatic acids from water

Adsorbents in the form of powders are commonly used to filtrate organic compounds in waters. However, this technique requires the separation of the solid phase from the solution after adsorption experiments. Here we propose the use of films as adsorbents. We synthesized polyaniline films by chemical oxidative polymerization of aniline on red ceramic brick. This film was tested to remove trimellitic, hemimellitic and pyromellitic acids as model molecules of the biodegradation of aquatic humic substances. We evaluated the effect of pH, contact time and initial concentration. Our results show that optimal adsorption conditions required 45 min of solid/liquid contact at pH 7 and an initial concentration of 20 mg/l. The maximum adsorption capacities for hemimellitic, trimellitic and pyromellitic acids are 154.83 for hemimellitic acid, 161.88 for trimellitic acid and 175.26 mg/g for pyromellitic acid. The adsorption efficiency of the polyaniline film decreased only by 13 % after four cycles. Overall, we conclude that polyaniline films are promising separable adsorbents compared to conventional adsorbents for removal of aromatic polycarboxylic acids from water.     

Comparative sensitivities of the tropical cladoceran,Ceriodaphnia rigaudii and the temperate species Daphnia magna to seven toxicants

The toxicities of seven chemicals [cadmium (Cd) chloride, potassium dichromate, sodium dodecyl sulfate, potassium chloride (KCl), Triton X-100, zinc (Zn) chloride and copper (Cu) (II) sulfate] were determined using the tropical freshwater cladoceran, Ceriodaphnia rigaudii and the temperate species, Daphnia magna. Data generated was subsequently used to determine the relative sensitivities of both species, using interspecies correlation to compare the 48?h LC50 values for both species. The 48?h LC50 values for C. rigaudii ranged from 0.002?mg?L^?1 (potassium dichromate) to 21.1?mg?L^?1 (KCl), whereas those for D. magna ranged from 0.3?mg?L^?1 for Cu to 418.87?mg?L^?1 for KCl. The LC50 values for C. rigaudii were significantly less than that for D. magna for six of the compounds tested. The interspecies correlation also showed a low, positive correlation suggesting that the sensitivities of both species were not similar for the compounds tested. The sensitivity factors for C. rigaudii and D. magna ranged between 0.01 and 12.3. These values further suggested that for six of the compounds tested, C. rigaudii appeared to be more sensitive than D. magna. It is therefore possible that because of these differences in relative sensitivities, toxicity data generated with D. magna may not be appropriate for Trinidad.     

An approach for assessing the suitability of Ceriodaphnia rigaudii as an indigenous tropical toxicity test species

Although the selection criteria for toxicity test species are well-documented, they do not provide a clear approach for establishing the suitability of a species for regulatory testing. This study looks at the approach used to determine if Ceriodaphnia rigaudii, an indigenous tropical cladoceran species, may be designated as a suitable freshwater test species for regulatory testing in Trinidad and Tobago. The approach involved species identification, life cycle characterization, salinity tolerance, toxicological responses to standard chemicals, and comparative sensitivity evaluation with an established test species. The results showed that C. rigaudii (0.45 mm) was significantly smaller in size, had a shorter life cycle and matured faster than temperate cladoceran species such as Ceriodaphnia dubia and Daphnia magna (3–6 mm). Ceriodaphnia rigaudii has a life span of about 10–15 days and reached sexual maturity within 2 days, whereas D. magna had a life span of about 40–50 days and attained sexual maturity within 6–10 days. The LC₅₀ values for C. rigaudii were significantly less than D. magna for the six compounds tested. Interspecies correlation also showed a low positive correlation, suggesting that the sensitivities of both species were not similar for the compounds tested. The sensitivity factors of C. rigaudii and D. magna for the toxicants ranged 0.01–12.3, suggesting that C. rigaudii was more sensitive than D. magna. This study was useful in defining a stepwise approach to help establish C. rigaudii as an indigenous tropical toxicity test species in Trinidad.     

Comparative sensitivity of three life stages of the tropical mysid,Metamysidopsis insularis to six toxicants

Test protocols citing mysids as a standard test species often recommend juveniles (48 h) as the most appropriate life stage for testing. Acute toxicity tests were conducted with six standard toxicants, with three life stages of Metamysidopsis insularis; juveniles (48 h), late juveniles (7–12 days) and adults (>13 days), to determine whether there were significant differences in the sensitivity between life stages. Three of the compounds tested (sodium dodecyl sulphate, potassium dichromate, and potassium chloride) showed a significantly higher 96 h-LC₅₀ for the adults when compared to the juveniles and late juveniles. Four of the compounds tested showed significantly higher 24 h- and 48h-LC₅₀ for the adults when compared to both the late juveniles and juveniles. Twenty-four hour-LC₅₀ values for juveniles were also significantly higher than the 48 and 96 h values. However, for the late juveniles and adults this was only true of a few compounds. Further, the 48 and 96 h values were statistically similar. Therefore, for M. insularis it may be appropriate to conduct acute toxicity test with juvenile for a 48 h period.     

Characteristics and potential environmental impacts of sand material from sand dunes and uplifted marine terraces as potential borrow sites for beach nourishment along the Jordanian coast of the Gulf of Aqaba

The coastal zone management and development plans which include tourism development necessitate among many other management practices, the extension of the available area of the present natural but narrow, limited and widely eroded beaches by implementing some type of nourishment practices. The present work is providing information on selected sites as possible sources of suitable sand, chemical and granulometric characteristics of their sand, and the potential direct and long-term environmental effects and consequences of its use in any future nourishment practices. Seven sites located within the up-lifted terraces area along the Jordanian portion of the Gulf of Aqaba, were selected as potential sources or borrow sites for sand that may be used in any future nourishment projects. Two sites were selected at the northeastern side of Aqaba region to represent sand dunes. Sand material from these sites were analyzed for their physical characteristics (grain size) as well as their content of heavy metals, organic carbon, total nitrogen, total phosphorous, and calcium carbonate. Standard methodological techniques were used during analysis of all constituents. The results were compared with those obtained from the analysis of sand deposits of six beaches along the Jordanian coastline of the Gulf of Aqaba. Results indicate that sand of the selected borrow sites has grain size fractions that are suitable for use in beach nourishment. Results of the measured pollution indicators indicate that their levels in the sand of the potential borrow sites are within or lower than their levels in the marine and coastal sediments of the Gulf of Aqaba and the Red Sea. These properties, in addition to the wide occurrence and availability of such sources along the coasts of the Red Sea and the Gulf of Aqaba, suggest that it will be a cheep source of sand for beach extension and restoration and their use in large amounts in beach nourishment project will not pose major hazards on the quality of seawater of the Gulf of Aqaba area     

An assessment of contamination and ecological risk of metals in sediments of the Guaracara,Caparo and Couva rivers in Trinidad,West Indies

The presence of metals in an aquatic environment can serve as a biomarker for pollution and can be used to evaluate its contamination status. Rapid industrialisation in recent decades has propelled Trinidad and Tobago to be one of the most developed nations within the Caribbean region and has stimulated the awareness of potential ecological risks from various industrial activities affecting the rivers of Trinidad. Sediment samples from three rivers along the West coast of Trinidad were analysed for Cd, Cr, Cu, Mn, Ni, Pb and Zn. For all three rivers, the metal concentrations in sediments were in the range of 0.40–2.31?μg/g, 12.77–33.04?μg/g, 14.51–72.89?μg/g, 224.90–4472.83?μg/g, 8.20–43.08?μg/g, 22.63–38.34?μg/g and 92.0–5462.60?μg/g for Cd, Cr, Cu, Mn, Ni, Pb and Zn, respectively. Assessment of the pollution status indicated that all three rivers were considered polluted, with significant contributions from Cr, Cu, Mn, Ni and Zn. The potential ecological risk for all three rivers, however, was low and multivariate statistics revealed that mainly anthropogenic sources contributed to the metal concentrations in sediments of all three rivers.     

Managing Mediterranean soil resources under global change: expected trends and mitigation strategies

Regional Environmental Change - The soils of the Mediterranean Basin are the products of soil processes that have been governed by a unique convergence of highly differentiated natural and...     

Coastal types of graben: the Gulf of Gökova,Mugla-SW Turkey

Grabens are formed under the influence of extensional forces in a normal fault system. The Gulf of Gökova is an active graben located in SW Turkey. Active grabens such as the Gökova enclose highly faulted rocky coasts. Despite the existence of these rocky coasts, examination of google earth images, field studies, DEM analysis and previous studies in the Gulf of Gökova graben revealed that there could be different types of coasts in the region. In this study the factors causing the occurrence and potential environmental effects of the diverse coast types are evaluated. By using the Fairbridge (2004) coastal classification system, the coast types identified in the Gulf of Gökova graben can be classified as; A. Soft-less consolidated-erodible; A1: relatively Insoluble: detrital and loose beach, A2: soluble: beachrock and eolinite B. hard-cliffed-rocky, B1: longevity of hard-rock coast and B2: fault controlled cliffs. The percentages of these classes generally decreased from B1 (79%), A1 (12.4%), B2 (8.3%) and A2 (0.3%) in the study area. As a result of longshore currents, A1-type coasts usually develop as large plain adjacent streams and also in pocket beaches as narrow-long strips near rocky coasts. A2 type is observed in one location within the Gökova region, possibly due to local environmental conditions. However, B1 type developed in peridotites, cherty limestone and cliffs probably because of the active fault system and where the fault plane cut the coast, B2 type occurred. Possible threats to the Gökova region can be attributed to sea level rise owing to tectonism and global warming. It is anticipated that inundation, coastal erosion and salt water intrusion may also affect it.