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In order to understand the hydrogeochemical pattern, ground (n = 23) and surface water (n = 2) samples were collected from three different landscapes (mountain, plain, valley) of Hidalgo State, Central Mexico. Physicochemical characteristics (pH, electrical conductivity, total hardness, alkalinity, total acidity, total solids, total dissolved solids, total suspended solids, CO2; cations (Ca2+, Mg2+, Na+), anions (NO3−, Cl−, PO43−and SO42−) and dissolved geochemical elements (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd and As) were analyzed. Results illustrated they are neutral to slightly alkaline due to the dissolution of carbonates. Average concentrations of anions and cations presented an order of (in mg/l): Na+ (273) > Ca2+ (206) > SO42− (181) > Cl− (163) > Mg2+ (115) > NO3− (11.07) > PO43− (0.12) revealing the local geogenic and anthropogenic influences. High mean concentrations of dissolved trace metals (0.052 mg/l) in the mountains is attributed to their diverse geochemical environment of the terrain and climatic variability. Concentrations of Cr, Cu, Ni and Zn were below the permissible limits set forth by WHO and the Mexican Government. Piper trilinear diagram revealed that they are mainly of Ca-Mg-HCO3 and Ca-Mg-SO4 type. Sodium Absorption Ratio (SAR) indicated that nearly 96% are of excellent quality, while Magnesium Adsorption Ratio (MAR) showed that 68% of them are unsuitable for irrigation purposes.

The present work represented first study of the spatio-seasonal distribution of the multi-elements in the suspended particulate matter (SPM) of the tropical Hooghly river estuary (HRE), eastern part of India. The high load of SPM (20–3460 mg/l) might have induced negative impact on the phytoplankton density. The relative abundance of the studied elements exhibited the following decreasing trend (concentration in μg/g and %): Si(26.44 ± 3.75%) > Al(7.94 ± 1.52%) > Fe(6.17 ± 1.9%) > K(3.05 ± 1.5%) > Ca(1.97 ± 1.11%) > Mg(1.57 ± 1.71%) > Na(1.45 ± 8.40%) > Mn(1273 ± 2003) > Zn(178.43 ± 130.95) > V(151.54 ± 27.13) > Cr(147.08 ± 32.21) > Cu(62.06 ± 14.03) > Ni(49.64 ± 12.09) > Pb(21.5 ± 10.45). The accumulation of Ni, Cr, Pb, and Cu is mainly controlled by the formation of Fe hydroxides along with particulate organic carbon (POC) and salinity. The average geo-accumulation index (Igeo) and enrichment factor (EF) endorsed the substantial input of Cr (Igeo = 0.037; EF = 1.61) and Zn (Igeo = 0.123; EF = 2.07) from diffused pollution sources. From ecotoxicological point of view, the quality guidelines (QGs) suggested that Cr and Ni might possess frequent adverse biological effects. However, the mean probable effect level (PEL) quotient values revealed 49% probability of toxicity to the aquatic biota for five toxic elements (Cr, Ni, Cu, Zn, and Pb). The geochemical approaches, pollution indices, and statistical evaluation together revealed low to moderate contamination in the estuary. This baseline data would be beneficial in adopting proper management strategies for sustainable utilization and restoration of the water resources. The authors strongly recommend continuous systematic monitoring and installation of treatment plants for management of this stressed estuary.

The main background of this study is that corona virus (COVID-19) has caused a global chaos where there was a complete lockdown of the whole planet as well as the collapse of the health system in many developed, developing and under-developed countries. This situation has caused a public health system and till date no decisive treatment is being confirmed so far. The present study from western Colombia focuses on the importance of traditional, cultural and generations history with reference to the use of importance and significance of medicinal plants, especially to find out a strategy to fight the new virus. The study was designed based on three major novel ethno-environmental strategies based on infusion, hot drinks, fresh baths and jelly types were identified. Based on the generated results, the calculated highest used species in the present pandemia indicates Zingiber officinale Roscoe (1.0), Eucalyptus globulus Labiil. (0.86), Citrus x limon (L.) Osbeck (0.80), Gliricidia sepium (Jacq.) Walp (0.56) and Matricaria recutita L. (0.52) were the species with the highest use. No significant difference was observed between men and women for the level of knowledge on these traditional medicinal plants. Moreover, many of the scientific information demonstrate their effectiveness in treating the respiratory infections caused due to the corona virus. The results infer the importance of traditional medicine, knowledge which needs more attention and research to counter attack the outbreak especially in medically weak health systems., Graphical abstract Unlabelled Image

Investigation on freshwater MPs has increased gradually across the world, since they are main trajectory for the transportation of MPs from inland to ocean. The present study aims to identify the presence, distribution and the type of MPs in the lake Hawassa, Ethiopia. Twenty-five shoreline surface sediments were separated using ZnCl

River Atoyac is considered to be one of the most polluted rivers in Mexico due to the discharges of untreated or partially treated wastewater from industrial and municipal activities. In order to improve the river water quality, it is obligatory to identify the possible contaminant sources for upholding a well-balanced ecosystem. Henceforth, the present study incorporates the application of a continuous real-time monitoring system to identify the provenance of pollutants of the river mainly from anomaly events. Four monitoring stations were installed all along the River Atoyac in the State of Puebla, Central Mexico. The real-time monitoring systems have an ability to measure various water quality parameters for every 15 minutes such as Temperature (T), pH, Conductivity (EC), turbidity (TURB), Dissolved Oxygen (DO), Oxidation Reduction Potential (ORP) and Spectral Absorption Coefficient (SAC). In total, eight water samples of anomaly events (i.e.) 2 per monitoring station during rainy (August–September) and winter seasons (November–December), that were detected using the parameters previously mentioned were procured and also analyzed in the laboratory for evaluating almost 54 physicochemical, inorganic and organic characteristics. Statistical results of factorial analysis explained that 30% of the total variance corresponded to textile effluents, 23% related to discharges produced by automobile and petrochemical industries, and 18% of the total variance defined the agricultural activities. Additionally, indices like Overall Index Pollution, Heavy Metal Evaluation Index, Screening Quick Reference Table and Molecular ratios of hydrocarbons for PAH sources was also calculated to estimate the grade of pollution and associated ecotoxicological risks. The present study also enlightens the fact that the assessed results will definitely provide valuable information for the management of river water quality by developing stringent public policies by governmental agencies for the sustainable conservation of Atoyac River.

Microplastics (MPs) are contaminants of emerging concern in aquatic environments. The abundance, distribution and characteristics (color, morphology, texture) of MPs from Atoyac River basin, a highly urbanized river system located in Central Mexico were investigated in this study. The sediment samples were collected from 29 different sites along the Atoyac River basin in four different zones: Zahuapan River, Atoyac River, Confluence zone and Valsequillo dam and processed for MPs extraction using ZnCl2 density separation method. The total number of MPs in Zahuapan River, Atoyac River, Confluence zone and Valsequillo dam was 1633.34 ± 202.56, 1133.33 ± 72.76, 833.33 ± 80.79 and 900 ± 346.12 items kg−1 respectively. It was found that the concentration of MPs is higher in the downstream section of the river (confluence zone: 833.33 ± 80.79 & Valsequillo dam: 900 ± 346.12 items kg−1), revealing significant impacts of dense population and industrial complex of Puebla City. Colored MPs were predominant accounting for 51% and white MPs for 49% of the total MPs. Films (25.9%) and fragments (22.2%) were the most abundant type followed by fibers (14.8%). Scanning electron microscope images revealed varying disintegration features and energy-dispersive X-ray spectra demonstrated the presence of different metal elements on the surface of MPs. The results highlighted the widespread distribution of MPs in the sediments of Atoyac River basin, Mexico.

Mercury and Selenium concentrations were determined in the muscle and liver tissues of Silky shark (Carcharhinus falciformis) and Smooth Hammerhead shark (Sphyrna zygaena) caught off Todos Santos, Southern Baja California, Mexico during August–December 2014. The average mercury concentrations in C. falciformis [(mg/kg) muscle: 3.04; liver: 3.95] and S. zygaena (muscle: 5.23; liver: 3.39) exceeded the permissible limit of 1.0 mg/kg established by the Mexican government. Biomagnification Factors (BMF) to understand the prey-predator relations were also calculated and it was observed that all BMFs were >1 indicating absolute biomagnification of Hg. Additional Se concentrations were found in C. falciformis: 5.34 mg/kg and S. zygaena: 3.29 mg/kg resulting in a molar excess of Se over Hg. Thus, our results prove to offer the basic strategies of Hg-Se biogeochemical processes in marine sharks.

The study evaluated the spatial and seasonal variations of microplastic abundances in water, sediments, and commercial fishes of a semi-urban tourist impacted estuary in the Gulf of Mexico, Mexico. The prevalence of microplastics (MPs) elucidated diffuse sources namely long-range transport, domestic, agricultural, fishing, industrial and recreational activities and the local climatic conditions. Seasonally, the mean abundances of MPs in both water and sediments were high during Nortes (strong winds) followed by the dry and rainy seasons. Overall, black and blue colored MPs dominated the region and all the recovered plastics were fibers. The commercial fishes (n = 187) contained 881 MPs in their gastrointestinal tracts, suggesting that the food web of the estuary is highly prone to microplastic contamination. SEM images of extracted plastic fibers presented surface morphologies that are impacted by physical strains. Further, the elemental characterization of fibers using EDX displayed significant peaks of Al, As, Cl, Cr, Cu, Pb, and Zn that were used as additives during the production of plastics. The main types of polymers included low-density polyethylene, polyester, polypropylene, polycarbonate, rayon, polyvinyl chloride, polyacrylonitrile, polyamide, nylon and polyethylene terephthalate. MP abundances demonstrated in this study elucidate that estuaries are a major conduit for land-derived plastics to the ocean and the results will aid in implementing remedial/clean up actions of the estuary for better conservation of the ecosystem.

International audience; This study aims to report the short-term coastline dynamics and inundation limits of coastal cities along the Eastern Pacific due to the sea swell events that occurred during April to May 2015. The multi-temporal satellite datasets from Landsat such as Enhanced Thematic Mapper (L7 ETM+) and Operational Land Imager/Thermal Infrared Sensor (L8 OLI/TIRS) of different periods before and after the swell events were used to identify the shoreline changes. The satellite images were pre-processed using ERDAS imagine 9.2, and the coastline was digitized in ArcGIS 10.4.1 for ten cities spread across from Mexico to Chile (in Pacific coast) using the spectral water indices, and the shoreline change rate and erosion/accretion pattern at each transect were estimated using the statistical parameters embedded in Digital Shoreline Analysis System (DSAS). The maximum erosion and accretion were observed in El Salvador (268 m) and Huatulco (Mexico) (115 m), respectively. Likewise, the maximum inundation was observed in El Salvador with 268 m and Acapulco (Mexico) with 254 m, and the tide gauge data suggest a possible relation to the bathymetry and the geomorphological conditions of the coast. Overall, the results indicate that the Eastern Pacific Ocean side sea swell events has led to extreme coastal flooding in recent years due to the increase in the mean sea level and the unpredictable variation in El Niño/Southern Oscillation events.

Microplastics (MPs) existence, identification and source were investigated by studying a total of 2539 particles in 349 sediment samples from nine different tourist beaches [(Sodwana & Richard Bays; Ballito, Mtunzini, Tugela, Zinkwazi, Ballito (north & south) and Durban north & south)] of southeastern coast of South Africa. They are more abundant in the beaches of the Durban city, followed by the Sodwana & Richards Bays, Ballito and Mtunzini. The black particles prevailed over the blue, white, pink, brown, red and green MPs. Supremacy of MPs in the Durban city is mainly due to the longshore coastal Agulhas current in the South eastern side of African coast aiding the degradation of primary plastics coming both from continent and sea. SEM images provided the evidences of weathering/degrading process through grooves, cracks, deep fissures, sharp edges and layered degradation showing signs of oxidation due to long term exposure in the coastal environment. EDS results suggested presence of elements (i.e. C, -O, Si, Al, Fe, Ca, Mg, Na, K, S, Ti, Cu and Zn introduced during the production of plastics as additives. FTIR spectral matches identified from all samples infer polypropylene (PP) (62%), rayon (RY) (17.2%), polycarbonate (PC) (29.8%), nylon (NY) (18.92%), polyester (PES) (31.2%), polyacrylonitrile (PAN) (11.21%) and polystyrene (PS) as well as low (28.9%) & high (36.1%) polyethylene terephthalate (PET). Higher abundance of MPs in the beaches of South Africa in comparison with studies around the world emphasizes the need of dispersal monitoring and use of plastic materials/polymers.

Total mercury (THg) and methylmercury (MeHg) were studied in sediments from 27 abandoned gold mining ponds (AGMPs) through small-scale artisanal gold mining in the district of San Juan in Chocó region of Colombia. The AGMPs were abandoned in the last century (1997) and were grouped into three distinct groups (2–6; 7–12; 13–20 years). Overall concentration (in ng g−1) pattern of THg in sediments varied from 39.06 to 1271.32 (avg. 209.57) with 174.81 (13–20 years), 205.56 (7–12 years) and 248.33 (2–6 yrs) respectively. MeHg concentrations accounted for 3.3–10.9% (avg. 6.5%) of THg and were significantly correlated with THg during all periods. Correlations between organic matter (OM) vs MeHg and THg were negative in the oldest pools, signifying a “dilution effect” or “natural burial” of THg and MeHg. Results for sequential extraction indicate that the fraction of elemental Hg (Hg-e) and organo chelated Hg (Hg-o) represent the main chemical forms of Hg in the sediments, regardless of the abandonment period, whereas the bioavailable fraction was only 0.12–1.65% of THg. The significant statistical relationship between MeHg, THg and OM suggests that these parameters control the distribution, mobility, toxicity and bioavailability of Hg in the sediments of these abandoned ponds. Evaluation of THg with sediment quality guidelines indicates that the values are on the higher side for Threshold effect concentration and Upper continental crust. Comparing of MeHg with many other regions outside Colombia is a worrying factor and needs immediate attention to protect the human health., The authors wish to thank the Administrative Department of Science, Technology and Innovation - “Francisco José de Caldas” (COLCIENCIAS) grant 694-2014 and 849-2018. MPJ thanks Sistema Nacional de Investigadores, CONACyT and Instituto Politécnico Nacional (EDI and COFAA), México. This article is the 109th contribution (partial) from the Earth System Science Group (ESSG), Chennai, India (Participating member: MPJ).

Trace metals Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd, and As were determined on a monthly basis in a total of 52 rain samples collected from six different locations in the central region of Mexico during March 2016&ndash, April 2017. The average concentrations of trace metals (mg/L) in the rainwater samples showed an order of Zn (0.873) &gt, Fe (0.395) &gt, Mn (0.083) &gt, Cr (0.041) &ge, Cu (0.041) &gt, Pb (0.031) &gt, Ni (0.020) &gt, Co (0.013) &gt, As (0.0003) &gt, Cd (0.002). The differences observed in metal concentrations are related to variations in the influence of continental air masses, local transport, regional advection, and the solubility of trace metals. High concentrations of metals were observed in the months of March to May at all sites, probably due to the less extensive removal of air/air pollutants. The values obtained from the enrichment factor (EF) per metal showed relatively high values for Cd, Zn, Cu, Pb, Co, Ni, and Cr, suggesting anthropogenic origin. Pearson&rsquo, s correlation matrix validated the distribution of trace metal sources and their relationships with local/regional meteorological characteristics. This paper presents relevant basic information for the evaluation of the toxic potential of rainwater and the possible health risks when using this source of water for human consumption.

Total mercury (THg), methylmercury (MeHg) in water, sediments, macrophytes, fish and human health risks were analyzed and assessed from abandoned gold mining ponds (AGMPs)/ mining areas in Western Colombia to know its present environmental condition. Concentrations of THg in water (avg. 13.0 ±13.73ng L-1) was above the EPA threshold level (12ng L-1), suggesting possible chronic effects. Sediment sample revealed that the ponds are methylated (%MeHg: 3.3–11%). Macrophyte Eleocharis elegans presented higher THg content in the underground biomass (0.16 ±0.13µg g-1 dw) than in the aerial biomass (0.05 ±0.04µg g-1 dw) indicating accumulation of THg. MeHg was the most abundant chemical species in fish (MeHg/THg: 83.2–95.0%), signifying higher bioavailability and its risk towards human health. Fish samples (15%) indicate that THg were above WHO limit (0.5µg g), particularly in Ctenolucius beani, Hoplias malabaricus) and lowest in Sternopygus aequilabiatus and Geophagus pellegrini. Bioaccumulation and biomagnification of MeHg were higher in the carnivores representing a source of exposure and potential threat to human health. Fulton’s condition factor (K) for bioaccumulation indicate a decrease with increasing trophic level of fishes. Overall results suggest, mercury species found in different AGMPs compartments should be monitored in this region., The authors wish to thank the Administrative Department of Science, Technology and Innovation - “Francisco José de Caldas” (COLCIENCIAS) grant 694-2014 and 849-2018. MPJ thanks Sistema Nacional de Investigadores, CONACyT and Instituto Politécnico Nacional (EDI and COFAA), México. This article is contributed (partial) from the Earth System Science Group (ESSG), Mexico and Chennai, India (Participating member: MPJ).

Cadmium, selenium, and mercury concentrations were measured in muscle and liver of juvenile blue (Prionace glauca) and smooth hammerhead (Sphyrna zygaena) sharks caught on the west coast of Baja California Sur, Mexico, to evaluate the human health risk associated with its consumption. Cd and Hg were lower than the maximum allowable limit for human consumption established by the Mexican government (Hg = 1.0 μg g

Trace element (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd, As, Hg) concentrations were assessed in marine organisms (n = 52) sampled from the Magdalena Bay lagoon complex in Baja California Sur, Mexico, a pristine marine environment. The overall trend of metal concentrations (dry weight) in the organisms was found to be Fe > Zn > Cd > Cu > Mn > Pb > As > Hg > Ni > Cr > Co. Bivalve mollusks (53.83 mg kg−1) contained twofold higher levels of metals than the finfishes (20.77 mg kg−1). Calculated BioConcentration Factor (BCF) values showed that dissolved Mn is readily bioavailable to the organisms, whereas Biota Sediment Accumulation Factor (BSAF) indicated high values for Zn, Cu and Cd. Cd and As levels were observed to be increasing with the trophic levels. Toxic elements, namely Pb, Cd and As in the studied fish species were found to be higher than the values recommended for human seafood consumption. The study provides a comprehensive baseline report on trace element bioaccumulation in several marine organisms that will aid in developing effective conservation strategies of the highly biodiverse lagoon complex.

S.B. Sujitha; M.P. Jonathan; D.C. Escobedo-Urias; Fernando Aguirre-Bahena; S.K. Sarkar; Lorena Elizabeth Campos Villegas, and E. Gonzalez Gomez., 2018. Fate of dissolved trace metals in the waters of Bahia Magdalena lagoon, Baja California Sur, Mexico. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 431–435. Coconut Creek (Florida), ISSN 0749-0208. Concentrations of dissolved trace metals (Fe, Mn, Cr, Cu, Ni, Co, Zn, Cd, As) were determined in forty-one surface and forty bottom water samples procured from Bahia Magdalena lagoon, Baja California Sur, Mexico using an Atomic Absorption Spectrophotometry. In-situ measurements of temperature, salinity, dissolved oxygen and pH were also carried out in each station and high salinities classified the lagoon as Eurihaline. The region witness raised temperatures (avg. 28.92°C) due to their location in an arid s...

Forty nine sediment samples were collected [Upstream section: Zahuapan River (1–12) and Atoyac River (13–20); Confluence Zone (21–31); Valsequillo dam (32–49)] to investigate the geochemical sources, enrichment, contamination and ecological risks of metals in the fluvial sediments of Atoyac River basin, an area experiencing tremendous urban and industrial development in Central Mexico. The sediments were analyzed for 23 major (Al, Fe, Ca, Mg, Na, K, P, S & Ti) and trace (Ba, Mn, As, Co, Cr, Cu, Mo, Ni, Pb, Sc, Sr, V, Zn & Zr) acid leachable metals (ALMs). The grain size results revealed that the sand fraction of sediments accounts for 53.1% and silt for 46.9% respectively. The concentration pattern (avg. values) shows a spatial distribution of metals in the four zones indicating that S (0.10; 0.13; 0.34; 0.80 in %), Ca (0.96; 0.73; 4.98; 1.85 in %), P (0.05; 0.05; 0.16; 0.08 in %), Cr (122; 182; 111; 104 in µg g−1), Mo (5; 9; 6; 10 in µg g−1), Cu (13; 14; 53; 29 in µg g−1), Ni (19; 22; 29; 46 in µg g−1), Pb (9; 12; 21; 14 in µg g−1), Zn (92; 62; 204; 92 in µg g−1) & As (2.63; 2; 3.35; 4.49 in µg g−1) exceeded the local background values primarily attributed to the natural volcanic inputs. Geochemical indices such as enrichment factor (EF), geoaccumulation index (Igeo) and pollution load index (PLI) were used to assess the degree of metal enrichment and the results revealed significant external influences over some metals (As, Cu, Pb and Zn). The calculation of potential ecological hazards index showed that among 23 tested metals, As, Pb, Cu, Ni and Cr were the main potential risk factors that will cause harmful biological effects in the riverine environment. A new complementary approach which integrates metal contamination, enrichment and ecological risks aided in more accurate determination of metal sources and their environmental impacts. Multivariate statistical analysis revealed the groupings of elements as lithogenic (Al, Fe, Ca, Mg, Na, K, P, S, Ti, Ba, Mn, Co, Cr, Ni, Sc, Sr, V & Zr) and external (Cu, Pb, Zn, Mo & As) suggesting that the metal sources are from volcanic events, natural weathering processes and the industrial influences from the Puebla City.

The present work investigated the spatial distribution and ecological risk assessment of total and mild acid-leachable trace elements in surface sediments (top 0–10 cm; grain size ≤ 63 μm) along the Hooghly (Ganges) River Estuary and Sundarban Mangrove Wetland, India. The trace elements, analyzed by ICPMS, showed wide range of variations with the following descending order (mean values expressed in milligrams per kilogram): Fe (25,050 ± 4918) > Al (16,992 ± 4172) > Mn (517 ± 102) > Zn (53 ± 18) > Cu (33 ± 11) > Cr (29 ± 7) > Ni (27 ± 6) > Pb (14 ± 3) > As (5 ± 1) > Se (0.37 ± 0.10) > Cd (0.17 ± 0.13) > Ag (0.16 ± 0.19) > Hg (0.05 ± 0.10). In the acid-leachable fraction, Cd (92%) is dominated followed by Pb (81%), Mn (77%), Cu (70%), and Se (58%) indicating their high mobility, imposing negative impact on the adjacent benthos. The sediment pollution indices (both enrichment factor and contamination factor) suggested severe pollution by Ag at the sampling site Sajnekhali, a wildlife sanctuary in Sundarban. The mean probable effect level quotient indicated that surface sediments in the vicinity of the studied region have 21% probability of toxicity to biota. The result of multivariate analyses affirms lithogenic sources (e.g., weathering parent rocks, dry deposition) for As, Pb, Cr, Cu, and Ni, whereas Cd and Hg originated from anthropogenic activities (such as urban and industrial activities). Both human-induced stresses and natural processes controlled trace element accumulation and distribution in the estuarine system, and remedial measures are required to mitigate the potential impacts of these hazardous trace elements.

The unusual winter storm event of March 2016 brought excess rainfall in the Central part of Mexico and this study attempts to determine the moisture sources by characterizing the rainwater isotopes (δ18O, δ2H) and understanding their monthly spatial variations. Rainwater samples from six different stations (Agua Blanca, Molango, Mexico City, Pachuca, Tula and Tulancingo) of Mexico were sampled in March, April and May 2016. Enriched isotopic signatures in Tulancingo during March exhibited a mixture of moisture sources in which the predominant source was from the North followed by the Gulf of Mexico, while the depleted isotopic levels in Pachuca and Tula moisture from the recycling of inland vapour. However, the isotopic characterization in the month of April presented no much variations in δ18O values irrespective of the station (−2.31 to −2.56‰), signifying that the prime moisture source is mainly from the inland sources and migrated from the central parts to the Gulf of Mexico. In contrast, the inland migration of the vapour source from Gulf of Mexico was witnessed in May with both the continental and the amount effect. However, the enriched δ18O values in Tulancingo and Agua Blanca in May were found to be −0.84‰ and −1.44‰ respectively, with significant lesser d-excess values.

A study on mercury (Hg) and selenium (Se) concentrations in the liver and muscle of brown smooth-hound shark Mustelus henlei and its principal prey items, was conducted in the western coast of Baja California Sur, Mexico. Average Hg concentrations were found to be high in the muscle than in the liver; however, Hg concentrations were below the maximum permissible limits, and hence, the consumption of this species does not constitute a risk to human health. The mean Se concentrations were higher in the liver than in the muscle. The results of Hg: Se molar ratio revealed that Se counteracts the toxicity of Hg in hepatic tissues, whereas the contrary occurs in the muscle. Significant differences in Hg and Se accumulation were observed between females and males. Biomagnification factor values >1 demonstrate a biomagnification process from its principal prey species (i.e., red crab, Pleuroncodes planipes and Pacific mackerel, Scomber japonicus).

The coast of Oaxaca, along the southern Mexican Pacific coastline, is home to diverse ecosystems, which undergoes significant erosion and accretion due to natural and anthropogenic influences. This study aims in analysing the historical shoreline variations and predicting the future changes for better coastal management plans. In order to study the long-term variations in shoreline, Landsat time-series satellite imageries between 1973 and 2020 were evaluated. Overall, the results indicate that the coast is highly dominated by accretion (74%) process, with the most significant changes occurring at the estuarine areas and beaches. Linear Regression Rate (LRR) and Weighted Linear Regression (WLR) methods showed mean variations at rates of 1.2 ± 2.5 and 0.4 ± 2.5 m/yr for the long-term period. The analysis of seven short-term periods (for every 5 years between 1986–2020) identified the maximum mean erosion of −20.6 m during 2005–2010 and accretion of 18.7 m during 2000–2005. However, the forecasted rate of change for the period 2030 and 2040 using End Point Rate (EPR) statistics revealed that the northern region would continue to move seaward at a rate of + 0 . 26 m/yr and the coastline of southern region would move landward at a possible rate of − 0 . 45 m/yr. The natural factors such as rainfall, river discharge, hurricane, and wave dynamics are the main drivers of shoreline changes along the estuarine and wetland areas. Contrarily, the anthropogenic factors such as breakwaters and urbanization are responsible for coastline dynamics along the beaches and ports. Henceforth, the estuarine region, lagoon openings, and tourist beaches require utmost attention as the sediment flow in these regions are not monitored constantly.

The study accentuated the trace metal accumulation and distribution pattern in individual organs of 13 native mangrove plants along with rhizosediments in the Indian Sundarban Wetland. Enrichment of the essential micronutrients (Mn, Fe, Zn, Cu, Co, Ni) was recorded in all plant organs in comparison to non-essential ones, such as Cr, As, Pb, Cd, Hg. Trunk bark and root/pneumatophore showed maximum metal accumulation efficiency. Rhizosediment recorded manifold increase for most of the trace metals than plant tissue, with the following descending order: Fe>Mn>Zn>Cu>Pb>Ni>Cr>Co>As>Cd>Hg. Concentrations of Cu, Ni, Pb and Hg were found to exceed prescribed sediment quality guidelines (SQGs) indicating adverse effect on adjacent biota. Both index of geoaccumulation (Igeo) and enrichment factor (EF) also indicated anthropogenic contamination. Based on high (>1) translocation factor (TF) and bioconcentration factor (BCF) values Sonneratiaapetala and Avicenniaofficinalis could be considered as potential accumulators, of trace metals.

The aim of the study was to evaluate the bioavailability of trace metals (Chromium, Copper, Nickel, Lead, Zinc, Cadmium, Arsenic, and Mercury) in the commercially consumed Crassostrea gigas oysters collected over a 12-month growth period (2011–12) from an experimental cultivation farm in La Pitahaya, Sinaloa State, Mexico. Sediment and water samples were also collected from four different zones adjacent to the cultivation area to identify the concentration patterns of metals. The results revealed that sewage disposals, fertilizers used for agricultural practices and shrimp culture are the major sources for the enrichment of certain toxic metals. The metal concentrations in oysters presented a decreasing order of abundance (all values in mg Kg−1): Zn (278.91 ± 93.03) > Cu (63.13 ± 31.72) > Cr (22.29 ± 30.23) > Cd (14.54 ± 4.28) > Ni (9.41 ± 11.33) > Pb (2.22 ± 1.33) > As (0.58 ± 0.91) > Hg (0.04 ± 0.06). Bioconcentration Factor (BCF) and Biota Sediment Accumulation Factor (BSAF) exhibited that C. gigas in the region are strong accumulators for Zn and Cd respectively. Thus, the present study proves to fulfill the gap in understanding the rate of bioaccumulation of metals in C. gigas which is regarded as the most sought after oyster species globally.

An integrated study using bulk chemical composition, mineralogy and mineral chemistry of sedimentary rocks from the Tukau Formation of Borneo Island (Sarawak, Malaysia) is presented in order to understand the depositional and tectonic settings during the Neogene. Sedimentary rocks are chemically classified as shale, wacke, arkose, litharenite and quartz arenite and consist of quartz, illite, feldspar, rutile and anatase, zircon, tourmaline, chromite and monazite. All of them are highly matured and were derived from a moderate to intensively weathered source. Bulk and mineral chemistries suggest that these rocks were recycled from sedimentary to metasedimentary source regions with some input from granitoids and mafic-ultramafic rocks. The chondrite normalized REE signature indicates the presence of felsic rocks in the source region. Zircon geochronology shows that the samples were of Cretaceous and Triassic age. Comparable ages of zircon from the Tukau Formation sedimentary rocks, granitoids of the Schwaner Mountains (southern Borneo) and Tin Belt of the Malaysia Peninsular suggest that the principal provenance for the Rajang Group were further uplifted and eroded during the Neogene. Additionally, presence of chromian spinels and their chemistry indicate a minor influence of mafic and ultramafic rocks present in the Rajang Group. From a tectonic standpoint, the Tukau Formation sedimentary rocks were deposited in a passive margin with passive collisional and rift settings. Our key geochemical observation on tectonic setting is comparable to the regional geological setting of northwestern Borneo as described in the literature.

Seventy-seven water samples were collected at the surface (S) and bottom (B) water profiles along eight transects (T1–T8) from Bahia Magdalena lagoon, Baja California Sur, Mexico during October 2014 to evaluate the spatial distribution patterns of dissolved inorganic nutrients (nitrates, nitrites and phosphates). Sea water properties (pH, temperature, dissolved oxygen, salinity, density and conductivity) were measured using a CTD instrument to assess their vertical profiling. On average, the lagoonal waters perceived raised temperatures (28.98 °C) and salinities (35.2 PSU) due to its semi-arid environmental setting. The lagoon presented an average pH value of 8.25 due to the high influence of sea water under oxygenated conditions. Due to the impact of wind driven waves and ventilation process, high oxygen saturation value of 96.8% (avg.) was observed in the waters. The average inorganic nutrient levels in the lagoon (nitrites: 0.002 mg/L, nitrates: 0.033 mg/L, phosphates: 0.023 mg/L) is due to the distinctive biogeochemical lagoon processes namely reduced precipitation, upwelling and absence of river input. The present study provides a preliminary data on the hydrographical and nutrient characteristics of a highly productive lagoon on the western coastal margin (Mexico) of the Pacific Ocean.

Geochemical characteristics of stream sediments [n = 31; Upstream section: Zahuapan River (1–12) and Atoyac River (13–20); Downstream section (21–31)] from Atoyac River basin of Central Mexico have been evaluated. The study focuses on the textural, petrography and chemical composition of the fluvial sediments with the aim of analyzing their provenance, the chemical weathering signature and their potential environmental effects. The fluvial sediments are mostly composed of sand and silt sized particles dominated by plagioclase, pyroxenes, amphiboles, K-feldspar, biotite, opaque and quartz. The sediments were analyzed for determination of major (Al, Fe, Ca, Mg, Na, K, P, Si, Ti), trace elements (As, Ba, Be, Co, Cr, Cu, Mo, Mn, Ni, Pb, Sc, V, Y, Zn, Zr, Ga) and compared with Upper continental crust (UCC), source area composition and local background values. The elemental concentrations were comparable with the average andesite and dacitic composition of the source area and the local background values except for enrichment of Cu (56.27 ppm), Pb (34 ppm) and Zn (235.64 ppm) in the downstream sediments suggesting a significant external influence (anthropogenic). The fluvial sediments of Atoyac River basin display low CIA and PIA values implying predominantly weak to moderate weathering conditions in the source region. Based on the provenance discrimination diagrams and elemental ratios, it is understood that the collected sediments are derived from intermediate to felsic volcanic rocks dominated in the study region. Metal contamination indices highlight the enrichment of Cu, Pb, Zn, Mo, Cr and S clearly indicating the influences from natural (weathering and volcanic activity) and external (anthropogenic) sources. Ecological risk assessment results indicate that Cr, Ni and Zn will cause adverse biological effects to the riverine environment.

Sediment metal concentrations were assessed in five different beach regions (n = 183) of KwaZulu-Natal (KZN) province in South Africa. Metal distribution revealed that Cr, Cu, Mo, Cd, Zn, Hg and As exceed the background upper continental crust values suggesting their anthropogenic origin (mining, agricultural and industrial) apart from natural geological inputs (gold placer deposits and heavy minerals). Various geochemical indices (Geoaccumulation index, Enrichment factor and Degree of contamination) confirmed that the sediment samples are extremely contaminated with Cr, Cd and Hg. Further, Hg and Cd were main contributors (60–90%) to the ecological threat in sediments. Hazard index estimated a high hazard potential of Hg in near future. Finally, present study together with our previous results portray the status of KZN coast with special significance to Hg contamination/enrichment. Thus, future researches are recommended to investigate the environmental and human health implications of mercury exposure in this coastal province.

The tourist beaches of Huatulco and Acapulco on the south Pacific coast of Mexico are being overstressed from the high number of tourists visiting the region. Human-induced activities not only contaminate the water, but also the beach sediments and aquatic organisms that are housed in the environment. Various multidisciplinary aspects such as socioeconomical, geochemical, and management issues were studied on almost 40 tourist beaches to evaluate the pollution status and enrichment of different geochemical elements. In addition, the promoting and depromoting factors of each tourist destination were assessed. Beach management practices and several laws put forth by the Mexican government were also emphasized for a better construal of the study regions. Thus, the present chapter defines an integrated approach for defining the tourism status and coastal management of high impacted tourist destinations for a better sustainable conservation of the ecosystem and its services.

The KwaZulu-Natal (KWZ) coast of South Africa hosts some of the finest and most pristine beaches in the world. Tourism has developed in recent years along with rapid urbanization, industrialization, and settlement of the human population near this coast. The existence of numerous ports and the industrial hub of this province exert tremendous changes in the natural existence of beaches. The data on geochemical metal concentration serve as one of the key tools to identify the quality and current pollution status of the beaches. One such geochemical study is statutory for the coastal tourist beaches of KZN, South Africa. Sediment samples were collected from intertidal regions of major tourist beaches in the southern and northern parts of KZN. They were analyzed to identify the occurrence of possible anthropogenic sources and the present natural geochemical indicators that act as a pointer for beach quality assessment. Among the various contaminants, trace metals are of great concern due to their abundance, persistence, and bioaccumulating nature. The beach sediment samples were analyzed for acid leachable trace metals that replicate the intensity and sources of pollution in the study area. The metal concentrations along the coastal beaches of KWZ suggest that the concentration of metals is mainly attributed to the natural source rock composition and the regions near major ports are significantly affected by the external inputs. The marine environments of KWZ need to be regularly monitored in terms of pollution and effectively managed through an integrated coastal management act.

The coastal region of Miri City, Malaysia, in recent years has been excessively occupied by urbanization related to industrial development. The stress and changes in the climatic conditions in the region have induced changes in the shoreline over the last five decades. In this study, the landuse/landcover changes along with spatial and temporal characteristics of the shoreline have been studied for a 74 km coastal belt adjacent to Miri for a period covering 51 years, using geographical information systems (GIS). The landuse/landcover changes between the periods of 1968–2014 are identified and discussed in comparison with the spatial and temporal changes of shorelines in the study area. The results of the landuse/landcover change analysis have highlighted the massive conversion of primary forests as secondary forests, palm oil plantations, and urban areas over the last five decades. Shoreline change detection over the different time periods shows a decade of cyclic reversal of erosion and accretion along the shoreline of Miri. The major accretion spots and erosion hotspots are demarcated and the factors involved in this phenomenon are also identified. The increased sediment delivery through the rivers (the Baram, Miri, and Sibuti rivers) from the upper river catchment region and reclamation activities caused the accretion whereas the erosion hotspots are the results of unscientific development and coastal protection activities.

We examined the presence of microplastics (MPs) in the gut contents of six fish species (Calamus brachysomus, Paralabrax maculatofasciatus, Eucinostomus dowii, Balistes polylepis, Achirus mazatlanus and Mugil curema) procured from Magdalena bay, Pacific Coast, Mexico. A total of 64 MPs were extracted from 87 individual samples, amongst which E. dowii (30 particles) and P. maculatofasciatus (27 particles) species presented the highest number of MPs. Of these, the majority of the MPs were fibrous filaments mainly of size 100 μm. The colour distribution was white-transparent (43%) and blue (36%). SEM imaging revealed the impact of mechanical weathering and disintegration through the presence of angular and irregular edges in the fibers. Likewise, strong carbon and oxygen peaks in the EDX spectra verified the fibers to be plastics. Differences in the ingestion of MPs among species are mainly due to species-specific physiognomies, habitat, feeding strategies and the availability of plastics. The present study contributes with a baseline data and a first assessment of microplastics debris ingested by fishes of Magdalena bay, Mexico.

Oceanic marine plastic contamination was an increasingly global issue due to increased demand. This has a significant effect not only on marine biodiversity, but also on public safety and numerous infectious diseases found in both aquatic and human species. A huge amount of money was spent worldwide on plastic waste. In the 1940s, plastics development began and is increasing massively. This crucial analysis intends to accomplish goals such as defining plastic materials, origins, detecting aggregation, and validating appropriate techniques to analyze plastic abundance spatio-temporal trends. This further addresses the possible impacts of plastics on marine species, humans, and future chemical emission control strategies together with advice. Plastics are primarily distributed along the coasts and mid-ocean vortex in large amounts. The broad variety of plastics, as eaten by aquatic animals finds their way to the human body through the food chain. Research articles should help learn the origins, deterioration mechanisms, and harmful effects of plastics on both the human body and the ecosystem. Until recently, the science community and politicians have generally ignored plastic waste, but ecological implications, as well as plastic pollution’s economic/health effects, have now gained greater global interest.