Heavy Metals Accumulation in Surface Waters, Bottom Sediments and Aquatic Organisms in Lake Mainit, Philippines

Lake Mainit is one of the largest lakes recognized as Key Biodiversity Areas (KBA) in the Philippines with rich fishery resources. However, the lake is at risk from heavy metal contamination due to inputs of industrial, agricultural effluents and small-scale mining activities. The present work evaluated levels of heavy metals namely cadmium, lead, and mercury from key aquatic fauna and sediments from seven strategic sections of the lake in 2018. Muscle samples of all seven fish species assessed were below detections limits (BDL) for tHg and Cd. Trace concentrations of Pb in the muscles were detected in Oreochromis niloticus, Glossogobius giuris, Channa striata and Vivipara angularis but values were within safe ranges. Trace concentrations of Pb in the riverine crab (Sundathelpusa sp) exceeded safe limits. Both Cd and tHg were below detection limits in the three invertebrates assessed. Traces of Pb were detected in S4 (Magtiaco) and S5 (Jaliobong) below standard limits (0.05 ppm) only during the southwest (SW) monsoon but Pb were not detected across all stations during the NE monsoon of 2018. For Cd, however, trace concentrations were detected only during the NE monsoon wherein Cd in S2 (Mayag), S3 (Magpayang), S4 (Magtiaco), S5 (Jaliobong), S6 (Dinarawan) and S7 (Kalinawan) exceeded standard limits for Cd in waters (0.01 ppm). Concentrations of tHg in the water were not detected across the two sampling seasons in all seven tributary stations. In sediments, Pb were all detected during the southwest monsoon with highest Pb concentrations in S6 (Dinarawan) and S7 (Kalinawan) which exceeded safe limits. Trace Cd in sediments were mostly below detectable limits. Concentrations of tHg in sediments exceeded safe limits during the SE monsoon in S4 (Magtiaco) and S7 (Kalinawan) areas. These findings recommended that continuous heavy metal monitoring must be conducted. It is also strongly suggested to evaluate the presence of heavy metals in other aquatic organisms and assess the ecological risk posed by these heavy metals though heavy metal speciation analysis.

Concentrations of total mercury (THg) and methyl mercury (MeHg) were determined for 32 surface sediments collected along the coastal line of Fujian Province and eastern Guangdong Province. The spatial distributions of THg and MeHg and their environmental impact factors were investigated. The average concentrations of THg and MeHg in the sediments were 31.5 ng/g and 0.096 ng/g, respectively. Both sediment THg and MeHg concentrations showed relatively high value in the Minjiang Estuary and the coastal areas of Quanzhou and Putian. The concentrations overall decreased as the distance to the shoreline increased. The correlations among environmental impact factors and THg, MeHg were analyzed. The sediment THg concentration was highly correlated to the concentrations of organic matter, copper, total nitrogen (TN) and total phosphorus (TP), and significantly correlated to pH value of the bottom seawater and concentration of sediment sulfide. The sediment MeHg concentration was highly correlated to the concentrations of organic matter and copper, and significant correlated to the concentrations of sulfide, TN, TP and pH value of the bottom seawater.

Potential effects of forest fire and storm flow on total mercury and methylmercury in sediments of an arid-lands reservoir

Mercury and methylmercury in aquatic sediment across western North America

Mercury transport between sediments and the overlying water of the St. Lawrence River area of concern near Cornwall, Ontario

Heavy metals and methylmercury in a tropical coastal estuary and a mangrove in Brazil

Abstract: In 2003, the U.S. Geological Survey (USGS) National Water‐Quality Assessment (NAWQA) program and U.S. Environmental Protection Agency studied total mercury (THg) and methylmercury (MeHg) concentrations in periphyton at eight rivers in the United States in coordination with a larger USGS study on mercury cycling in rivers. Periphyton samples were collected using trace element clean techniques and NAWQA sampling protocols in spring and fall from targeted habitats (streambed surface‐sediment, cobble, or woody snags) at each river site. A positive correlation was observed between concentrations of THg and MeHg in periphyton (r2 = 0.88, in log‐log space). Mean MeHg and THg concentrations in surface‐sediment periphyton were significantly higher (1,333 ng/m2 for MeHg and 53,980 ng/m2 for THg) than cobble (64 ng/m2 for MeHg and 1,192 ng/m2 for THg) or woody snag (71 ng/m2 for MeHg and 1,089 ng/m2 for THg) periphyton. Concentrations of THg in surface‐sediment periphyton had a strong positive correlation with concentrations of THg in sediment (dry weight). The ratio of MeHg:THg in surface‐sediment periphyton increased with the ratio of MeHg:THg in sediment. These data suggest periphyton may play a key role in mercury bioaccumulation in river ecosystems.

Mercury and methylmercury distribution in the intertidal surface sediment of a heavily anthrophogenically impacted saltwater-mangrove-sediment interplay zone

This study provided a picture of the spatial and temporal distributions of Cr, Co, Ni Cu, Zn, As, Cd and Pb in bottom sediments of Tolo Harbour. The concentrations of the eight heavy metals differed significantly between sites due to the poor tidal flushing in Tolo Harbour. The levels of Cu, Zn, Cd and Pb were generally enriched in sediments from inner Tolo Harbour, while sediments from outer Tolo Harbour (Tolo Channel) had higher levels of Cr, Co and Ni. The redox sensitive element arsenic showed no distinct spatial pattern in Tolo Harbour. The decreasing levels of Cu, Zn, Pb and Cd in sediments with increasing distance from land demonstrated a typical diffusion pattern from land to the direction of sea. Two hot spots of Cu, Zn, Pb and Cd in sediments were located near Tai Po and Sha Tin new town, indicating that Cu, Zn, Pb and Zn were from land-derived sources. The sites with relatively high levels of Cr, Co and Ni in sediments were located in areas close to waste spoil in sea floor. The natural and anthropogenic inputs from Sha Tin and Tai Po to Tolo Harbour were mostly responsible for Cu, Zn, Cd and Pb enrichment in sediments from inner Tolo Harbour. The waste spoil in sea floor was believed to contribute to the Cr, Co and Ni in outer Tolo Harbour. The results of correlation coefficient between the eight heavy metals showed that Cu, Zn, Cd and Pb were strongly positively correlated, and Cr, Co and Ni were also significantly correlated with each other. The best explanation of strong correlation was their similar source. As, however, is not well correlated with the other seven heavy metals. The average concentrations of Cu and Zn displayed general increasing trends from 1978 to 2006 in Tolo Harbour, while the mean levels of Cr and Pb displayed a substantial decrease from 1978 to 1987, then a slight increase after 1987. No distinct temporal trends of the concentrations of Ni and As were observed from 1978 due to the inconsecutive data. On the other hand, the increasing trends of Cr, Cu, Zn, Cd and Pb were observed since 1996.

Between 1932 and 1968, industrial wastewater containing methylmercury (MeHg) and other mercury (Hg) compounds was discharged directly into Minamata Bay, Japan, seriously contaminating the fishery. Thousands of people who consumed tainted fish and shellfish developed a neurological disorder now known as Minamata disease. Concentrations of total mercury (THg) in recent fish and sediment samples from Minamata Bay remain higher than those in other Japanese coastal waters, and elevated concentrations of THg in sediments in the greater Yatsushiro Sea suggest that Hg has moved beyond the bay. We measured stable Hg isotope ratios in sediment cores from Minamata Bay and the southern Yatsushiro Sea and in archived fish from Minamata Bay dating from 1978 to 2013. Values of δ(202)Hg and Δ(199)Hg in Yatsushiro Sea surface sediments were indistinguishable from those in highly contaminated Minamata Bay sediments but distinct from and nonoverlapping with values in background (noncontaminated) sediments. We conclude that stable Hg isotope data can be used to track Minamata Bay Hg as it moves into the greater Yatsushiro Sea. In addition, our data suggest that MeHg is produced in bottom sediments and enters the food web without substantial prior photodegradation, possibly in sediment porewaters or near the sediment-water interface.

Since late 2011 mercury has been used to extract the gold requiring in artisanal gold mining in Mt. Botak (Buru Island) and resulting in deposition of mercury into Kayeli Bay. In this project, we reported the updated total mercury (THg) concentration in marine sediment and nine species of domersal fish from Kayeli Bay. Nine coastal sampling sites were selected in the Kayeli Bay by purposive sampling. The fish are collected from a traditional market in Buru Island. The total mercury (THg) concentrations in marine sediment were found in all sites, ranging from 0.035 to 4.802 in mg.kg−1 DW). The THg concentrations in sediments from all sites measured were found has exceeded to those shown in the National Oceanic and Atmospheric Administration (NOAA) value. Among fish, the highest THg concentration of 1.667 mg.kg−1 was measured in the muscle species Myripristis kuntee and the lowest THg concentration detected for Lutjanus Lutjanus (0.016 mg.kg−1 DW). The distribution of total mercury (THg) concentrations found in the marine sediment of Kayeli Bay shows a very closed relationship to the artisanal gold mining activity in Mt Botak.

The heavy metals Cu, Pb, Zn, and Cd in the stream sediment of the Tajum River were studied based on 12 sediment samples obtained from upstream to downstream. The artisanal mining activities in the study area generated mining processing waste (tailing) and are the primary source of heavy metal pollution. The samples were analyzed for metal concentration as well as metal mobility based on sequential extraction analysis. Heavy metal analysis for the concentration of the metals showed that the value of Cu, Pb, Zn, and Cd in sediment samples transcends the mean crust. The change of the heavy metal concentrations in stream sediment between the upstream and downstream areas showed that higher levels were located near mining activities in upstream and that these decreased with distance to downstream. The result of the sequential extraction study revealed that Cu and Pb were more found in the exchangeable and carbonate fraction of about 26% and 24%. Meanwhile, Zn and Cd were present in the Fe-Mn oxide, an organic and residual fraction of about 90% and 85%, respectively. The mobility factor assessment revealed that the heavy metals investigated had an average mobility factor of 25.89%, 23.9%, 14.4 %, and 9.24% for Cu, Pb, Zn, and Cd, respectively. Overall, Zn and Cd in sediment in the study area were less mobile compared with Cu and Pb.

Heavy metal pollution caused by small-scale metal ore mining activities: A case study from a polymetallic mine in South China

Mercury contamination in the water bodies of developing countries is a serious concern due to its toxicity, persistence, and bioaccumulation. Vembanad, a tropical backwater lake situated at the southwest coast of India, is the largest Ramsar site in southern India. The lake supports thousands of people directly and indirectly through its resources and ecosystem services. It is highly polluted with toxic pollutants such as heavy metals, as it receives effluent discharges from Kerala's major industrial zone. In the present study, water, pore water, sediment, and fish samples collected from Vembanad Lake were analysed for total mercury (THg) and methyl mercury (MHg) contents. The maximum concentrations of THg and MHg in surface water samples were31.8 and 0.21ng/L, respectively, and those in bottom water samples were 206 and 1.22ng/L, respectively. Maximum concentration of THg in surface sediment was observed during monsoon season (2850ng/g) followed by that in the pre-monsoon season (2730ng/g) and the post-monsoon season (2140ng/g). The highest sediment concentration of MHg (202.02ng/g) was obtained during monsoon season. The spatial variation in the mercury contamination clearly indicates that the industrial discharge into the Periyar River is a major reason for pollution in the lake. The mercury pollution was found to be much higher in Vembanad Lake than in other wetlands in India. The bioaccumulation was high in carnivorous fishes, followed by benthic carnivores. The THg limit in fish for human consumption (0.5mg/kg dry wt.) was exceeded for all fish species, except for Glossogobius guiris and Synaptura orientalis. The concentration of THg was five times higher in Megalops cyprinoides and four times higher in Gazza minuta. Significant variation was observed among species with different habits and habitats. Overall, risk assessment factors showed that the mercury levels in the edible fishes of Vembanad Lake can pose serious health impacts to the human population.

Mercury (Hg) has been regarded as a global pollutant due to its volatility and toxicity. The sediment in the reservoirs or lakes is an important compartment for Hg methylation and it has also been considered as a sensitive area of Hg. In this study, a typical forest reservoir surrounding by evergreen broad-leaved forest in Chongqing of southwest China was selected to investigate the migration and transformation of Hg in unsubmerged soil and sediment. The unsubmerged soil and sediment were also replaced to each other to observe the dynamics of THg and TMeHg concentrations in equilibrium processes. The results were as follows:① The THg and TMeHg mean concentrations in Dahonghai reservoir water were (1.89±0.72) ng·L-1 and (0.13±0.04) ng·L-1, respectively, which were lower than the first class water quality standards in environmental quality standard of China and other reservoirs or lakes, implying that this study area did not affect by Hg pollution. Meanwhile, the THg and TMeHg mean concentrations in unsubmerged soil and sediment were also lower than those in other reservoirs or lakes. ② Seasonal variations of THg and TMeHg concentrations in reservoir water and soil were both observed higher in warm seasons, and more obvious variations occurred for TMeHg which probably influenced by meteorological parameters, such as, temperature and rainfall. ③Compared with unsubmerged soil, the THg and TMeHg mean concentrations in sediment were both elevated, suggesting the sediment was an important sink of Hg. While, the sediment would be a source of Hg (especially TMeHg) with a high THg and TMeHg level. ④ The THg and TMeHg mean concentrations in unsubmerged soil and sediment after situ replacement were equilibrated with ambient soil in a short time (one or two months), implying the hydro-fluctuation belt of reservoir promoting the geochemical cycle of Hg.