Concentrations Of Manganese In Water Research Articles

Disparities in Drinking Water Manganese Concentrations in Domestic Wells and Community Water Systems in the Central Valley, CA, USA.

Over 1.3 million Californians rely on unmonitored domestic wells. Existing probability estimates of groundwater Mn concentrations, population estimates, and sociodemographic data were integrated with spatial data delineating domestic well communities (DWCs) to predict the probability of high Mn concentrations in extracted groundwater within DWCs in California's Central Valley. Additional Mn concentration data of water delivered by community water systems (CWSs) were used to estimate Mn in public water supply. We estimate that 0.4% of the DWC population (2342 users) rely on groundwater with predicted Mn > 300 μg L-1. In CWSs, 2.4% of the population (904 users) served by small CWSs and 0.4% of the population (3072 users) served by medium CWS relied on drinking water with mean point-of-entry Mn concentration >300 μg L-1. Small CWSs were less likely to report Mn concentrations relative to large CWSs, yet a higher percentage of small CWSs exceed regulatory standards relative to larger systems. Modeled calculations do not reveal differences in estimated Mn concentration between groundwater from current regional domestic well depth and 33 m deeper. These analyses demonstrate the need for additional well-monitoring programs that evaluate Mn and increased access to point-of-use treatment for domestic well users disproportionately burdened by associated costs of water treatment.

Ecological State of Lake Gusinoe—A Cooling Pond of the Gusinoozersk GRES

The study of the transformation of substances in the basin of the Selenga River—the main tributary of Lake Baikal—under anthropogenic pressure and in the context of global climate change, is especially important for the lake, a globally important source of drinking water. The ecosystem of Lake Gusinoe is one of the key objects in the Selenga River basin that is exposed to significant anthropogenic pressure. This study presents the results of an analysis of water level changes and physicochemical parameters of the water mass of Lake Gusinoe; literature data from 1951 to 2017 and own data from 2017 to 2021. The water level in the lake had depended on natural factors before the Gusinoozersk GRES was launched; however, since the plant has begun using the lake as a cooling pond, its level has actually been regulated by the economic entity. Over the years, there has been a significant increase in mineralization, sulfate, sodium, fluoride and organic matter fractions resistant to oxidation. Seasonal increases in iron and manganese concentrations in water were detected. Increased concentrations of nutrients and organic matter fractions resistant to oxidation were registered at the wastewater discharge sites. Heavy metals in the bottom sediments of Lake Gusinoe accumulate mainly in the silt of the deep zone of the lake. Plants growing in the zones of influence of the Gusinoozersk GRES and Gusinoozersk wastewater discharge accumulate the largest amount of metals.

Low Temperature Ammonia Nitrogen Removal from an Iron, Manganese, and Ammonia Groundwater Purification Process with Different Concentrations of Iron and Manganese

In a groundwater plant, removal of iron, manganese, and ammonia nitrogen was performed via a purification process using a filter column at a low temperature (5-6℃). Iron, manganese and ammonia [Fe(Ⅱ) 0-19.26 mg·L-1, Mn(Ⅱ) 0.52-2.05 mg·L-1, and NH4+-N 0.37-2.59 mg·L-1] were analyzed to explore the ammonia nitrogen removal efficiency under different iron and manganese concentrations. The results showed that when the concentration of manganese in the inlet water was maintained at approximately 0.6 mg·L-1 and the concentration of ferrous iron in the inlet water was increased, with the increase of iron oxides in the filter layer, the ratio of ammonia nitrogen removed by adsorption of iron oxides increased, while the ratio of ammonia nitrogen removed by nitrification will decreased and adsorption preceded nitrification. When the concentration of ferrous iron in the water was maintained at approximately 8 mg·L-1and 11 mg·L-1, and the concentration of manganese in the water was increased, the proportion of ammonia nitrogen removed by adsorption did not increase with the increase of manganese oxide, and the removal route of ammonia nitrogen hardly changed. This is because less manganese oxides were formed 20 cm before the filter layer, which had little effect on the ammonia nitrogen adsorbed in this range. The production area of manganese oxides was concentrated below 20 cm of the filter layer, and most ammonia nitrogen was removed by adsorption and nitrification before this area, and the manganese oxides in this area did not adsorb ammonia nitrogen.

Chronic exposure to heavy metals from informal e-waste recycling plants and children's attention, executive function and academic performance

E-waste contains valuable metals that require appropriate waste management plans. However, rudimentary e-waste processing methods are a source of heavy metals environmental pollution. This study has characterised concentrations of heavy metals in soil (n = 10), water (n = 10) and hair (n = 44) of children in areas surrounding Jakarta (Indonesia), where e-waste is being or has been conducted in the past, and in a reference unexposed site. Chronic exposure to Mn, Pb, Hg, As and Cd and its associations with attention and executive function, characterised with the Trail Making Test (TMT), along with academic performance scores was conducted using multivariate regression analysis. Models were adjusted for age, gender, parental education, environmental tobacco smoke and residential traffic. Lead (3653 ± 3355 mg/kg), cadmium (3.4 ± 0.9 mg/kg) and mercury (15.2 ± 28.5 mg/kg) concentrations from soil and manganese concentrations in water (1.43 ± 0.64 mg/L) in the exposed sites were higher than current regulations. Heavy metal concentrations in hair of children living near e-waste facilities was higher than for children living in non-exposed areas (Pb: 0.155 ± 0.187 vs 0.0729 ± 0.08 mg/g; Mn: 0.130 ± 0.212 vs 0.018 ± 0.045 mg/g; Hg: 0.008 ± 0.0042 vs 0.002 ± 0.0011 mg/g) suggesting chronic exposure to heavy metals. Manganese exposure was associated with worse cognitive performance in the domains of attention (TMT-A score: 66 s, 95% CI 0.09, 132), executive function (TMT-B score: 105 s, 95% CI 11.5, 198) and social sciences (−29%, 95% CI −54, −4.7) (per unit of Mn in hair mg/g). These results suggest that informal e-waste activities contribute to local heavy metal soil contamination, and could be an important source of metal exposure to children living in the vicinity of these facilities with putative impacts on their cognitive performance. E-waste management regulation and remediation programmes should be implemented to reduce environmental pollution and associated health effects.

Performance of colorimetric methods for the analysis of low levels of manganese in water

The present paper describes a laboratory investigation conducted with the main aim to compare two colorimetric methods (1-(2-pyridylazo)-2-naphthol (PAN) from HACH® and porphyrin ligand (T-(4CP)P)) with ICP analyses for the evaluation of low concentrations of manganese in water. The colorimetric porphyrin method was found to provide reliable results compared to those obtained by inductively coupled plasma - optical emission spectroscopy (ICP-OES) even at low Mn2+ concentrations (<10 µg L−1). The presence of MnO2 particles results in an overestimation of the dissolved Mn2+ if unfiltered samples are analyzed by ICP and PAN methods. The presence of particles does not significantly impact sample analysis by porphyrin (T-(4CP)P) colorimetry. Although ICP-OES is still the analytical approach of reference, the porphyrin colorimetric method displays a high detection range and precision and could be a suitable on-site alternative to the current widespread use of the PAN method. In all cases, for both colorimetric methods, the use of Rochelle salt is recommended to alleviate calcium cation interference.

Manganese incorporation in living (stained) benthic foraminiferal shells: a bathymetric and in-sediment study in the Gulf of Lions (NW Mediterranean)

Abstract. Manganese geochemistry in deep-sea sediments is known to vary greatly over the first few centimeters, which overlaps the in-sediment depth habitats of several benthic foraminiferal species. Here we investigated manganese incorporation in benthic foraminiferal shell carbonate across a six-station depth transect in the Gulf of Lions, NW Mediterranean, to unravel the impacts of foraminiferal ecology and Mn pore water geochemistry. Over this transect water depth increases from 350 to 1987 m, while temperature (∼13 ∘C) and salinity (∼38.5) remained relatively constant. Manganese concentrations in the tests of living (rose bengal stained) benthic foraminiferal specimens of Hoeglundina elegans, Melonis barleeanus, Uvigerina mediterranea, and Uvigerina peregrina were measured using laser ablation inductively coupled mass spectrometry (laser ablation ICP-MS). Pore water manganese concentrations show a decrease from shallow to deeper waters, which corresponds to a generally decreasing organic-matter flux with water depth. Differences in organic-matter loading at the sediment–water interface affects oxygen penetration depth into the sediment and hence Mn pore water profiles. Mn ∕ Ca values for the investigated foraminiferal species reflect pore water geochemistry and species-specific microhabitat in the sediment. The observed degree of variability within a single species is in line with known ranges in depth habitat and gradients in redox conditions. Both the Mn ∕ Ca ratio and interspecific variability hence reflect past Mn cycling and related early diagenetic processes within the sediment, making this a potential tool for bottom-water oxygenation and organic-matter fluxes. Dynamics of both in-sediment foraminiferal depth habitats and Mn cycling, however, limit the application of such a proxy to settings with relatively stable environmental conditions.

Heavy metals in water, fishes and sediments in Derbendikhan reservoir, Kurdistan Region-Iraq

The present study carried out from June 2006 to August 2007 in eleven sites within Darbendikhan reservoir/ Sulaimany provence to determine heavy metals concentration in water, fish muscle and sediments. Nickel concentration in water was ranged from 0.148 to 3.317 mg l⁻ 1 , in fish muscle was from 29.6 to 88.851 µg g -1 and in sediment was from 59.234 to 355.404 µg g -1 . Cadmium ranges in water , fish muscle and sediment were 0.063 - 0.083 mg l⁻ 1 , 0.024 - 19.592 µg g -1 and 19.592 - 44.082 µg g -1 respectively. Cupper concentration in water was 0.01 - 0.072 mg l⁻ 1 , while in fish muscles was 0.031 - 78.281 µg g -1 and in the sediment was at level of l37.08- 133.302 µg g -1 . Iron in the water samples was 0.103 - 11.268 mg l⁻ 1 , in fish muscle was 0.93 to 651.294µg g -1 and in sediment were 6461.25 and 6967.812 µgg -1 . Manganese concentrations in water, fish muscle, and sediment samples were ran studied heavy metals are relatively approach to WHO standards.

Low level exposure to manganese from drinking water and cognition in school-age children

BackgroundManganese (Mn) is an element found in the environment and certain geographic areas have elevated concentrations in soil and water du to natural conditions or anthropic activities. A growing body of data suggests that exposure to manganese in drinking water could be neurotoxic. ObjectiveFirstly, we aimed to examine the association between exposure to manganese from drinking water and cognition in children consuming well water. Secondly, we also aimed to examine the relation between cognition and manganese concentrations in children’s hair, nail, and saliva. MethodsA total 259 children from 189 households consuming well water were included in the present study (ages 5.9 to 13.7 years). We assessed children’s cognition with the WISC-IV, and we used five indicators of manganese exposure: concentration in tap water, intake from the consumption of water divided by child’s weight, manganese concentration in children’s hair, toe nail, and saliva. We used General Estimating Equation analysis to assess the relation between manganese exposure indicators and IQ scores, adjusting for potential confounders, and taking into account family clusters. ResultsDrinking water manganese concentrations were generally low, with 48% of children consuming water <5μg/L, 25% >50μg/L, and 4% >400μg/L. Results differed by sex. In girls, higher manganese concentration in water, hair, and toe nail were associated with poorer Performance IQ scores but this was significant only for toe nail (for a 10-fold increase in manganese, β: −5.65, 95% CIs: −10.97, −0.32). Opposite associations were observed in boys, i.e., better Performance IQ scores with higher manganese concentration hair, toe nail, and water, the latter being significant (β: 2.66, 95% CIs: 0.44, 4.89). Verbal IQ scores did not seem to be associated with manganese exposure indicators. ConclusionsDrinking water manganese levels were considerably lower than in previous studies reporting neurotoxic effects. There was no clear indication of an association between exposure to manganese and cognitive development in this sample of school-age children although the data suggest there might be sex-specific associations. Given the low levels of exposure and sex-specific associations, a larger sample size would have been required to increase the statistical power and better characterize the relations.

Manganese in Drinking Water and Cognitive Abilities and Behavior at 10 Years of Age: A Prospective Cohort Study.

Background:Cross-sectional studies have indicated impaired neurodevelopment with elevated drinking water manganese concentrations (W-Mn), but potential susceptible exposure windows are unknown.Objectives:We prospectively evaluated the effects of W-Mn, from fetal life to school age, on children’s cognitive abilities and behavior.Methods:We assessed cognitive abilities and behavior in 1,265 ten-year-old children in rural Bangladesh using the Wechsler Intelligence Scale for Children (WISC-IV) and the Strengths and Difficulties Questionnaire (SDQ), respectively. Manganese in drinking water used during pregnancy and by the children at 5 y and 10 y was measured using inductively coupled plasma mass spectrometry.Results:The median W-Mn was (range 0.001–6.6) during pregnancy and () at 10 y. In multivariable-adjusted linear regression analyses, restricted to children with low arsenic (As) exposure, none of the W-Mn exposures was associated with the children’s cognitive abilities. Stratifying by gender (p for interaction in general ) showed that prenatal W-Mn () was positively associated with cognitive ability measures in girls but not in boys. W-Mn at all time points was associated with an increased risk of conduct problems, particularly in boys (range 24–43% per mg/L). At the same time, the prenatal W-Mn was associated with a decreased risk of emotional problems [odds ratio (OR)=0.39 (95% CI: 0.19, 0.82)] in boys. In girls, W-Mn was mainly associated with low prosocial scores [prenatal W-Mn: OR=1.48 (95% CI: 1.06, 1.88)].Conclusions:Elevated prenatal W-Mn exposure was positively associated with cognitive function in girls, whereas boys appeared to be unaffected. Early life W-Mn exposure appeared to adversely affect children’s behavior. https://doi.org/10.1289/EHP631

Exposure to manganese from drinking water and IQ in school-age children

Background: Manganese is a naturally occurring element and can be found in underground water at high concentrations. This element is a known neurotoxicant, although this has mostly been documented with workplace airborne exposure. A growing body of data suggests that exposure to manganese in drinking water could be neurotoxic. Our objective was to examine the association between exposure to manganese from drinking water and cognitive function in children. Methods: We recruited 262 children consuming groundwater, and assessed their cognition with the WASI (yielding Performance, Verbal and Full Scale IQ scores). To estimate exposure, we measured manganese concentration in home tap water and in children’s hair and toenail. We used linear regression analysis to assess the relation between log10 manganese exposure indicators and IQ scores in boys and girls, adjusting for potential confounders. Results: Drinking water manganese concentrations were generally low, with 48% of children consuming water below 5 μg manganese/L, 25% above 50 μg/L, and 4% above 400 μg/L. In girls, higher levels of exposure as indicated by all indicators (manganese concentration in water, hair, and toe nail) were consistently associated with poorer Performance IQ scores. However, these relations were not statistically significant after covariate adjustment, except for the association between log10 toe nail manganese concentration and Performance IQ (: -5.9, 95% CI: -11.8, -0.04). In boys, there was no clear association between manganese exposure indicators and IQ scores. Conclusions: Drinking water manganese levels were considerably lower than in previous studies reporting neurotoxic effects. Manganese exposure appeared associated in a dose-dependent way with lower Performance IQ scores in girls but not in boys. Studies should further examine the risks of manganese-contaminated drinking water, with a sample size sufficient to detect sex-specific effects.

Manganese exposure through drinking water during pregnancy and size at birth: A prospective cohort study.

The essential element manganese (Mn) might be toxic at excess exposure. We assessed the impact of elevated Mn exposure through drinking water during pregnancy on birth size in a population-based cohort(n = 1695) in rural Bangladesh. Concentrations of water Mn (median = 236 μg/L, range = 7.1-6336; n = 1177) and erythrocyte Mn (median = 30 μg/kg, range = 6.3-114; n = 758) were measured using ICP-MS. In regression analyses, newborns of women in the highest tertile of water Mn (median = 1495 μg/L) were 0.49 cm (0.20 SD) shorter (B = -0.42; 95% CI: -0.77, -0.08) than those in the lowest tertile (56μg/L). The inverse association was significant in girls and also in boys of mothers with lowest hemoglobin values, likely due to higher absorption of Mn. Manganese concentrations in water and erythrocytes did not correlate, and the associations of the latter with birth size were less obvious. This study suggests that consumption of water with highly elevated Mn levels during pregnancy may impair fetal growth.

Type 1 diabetes epidemic in Finland is triggered by zinc-containing amorphous silica nanoparticles

Type 1 diabetes (T1D), an autoimmune disease, breaks out in some of the children who has genetic susceptibility to T1D. Besides genetic susceptibility some environmental factor(s) are required to trigger the disease. The incidence of T1D in Finland is highest in the world, so we must seek an environmental factor, that is typical for Finland and can declare many aspects of T1D epidemiology and biology. In the literature most popular trigger has been enterovirus infections. It is difficult however to find why enteroviruses would be in this role in Finland in contrary to neighbouring countries e.g. Sweden.Colloidal amorphous silica (ASi) is typical for Finnish environment in consequency of the geohistory of Finland, great part of Finland is an ancient lake and sea bottom. ASi concentrations in natural waters are high in April–June and in November, only traces can be found in the rest of months. Pure colloidal ASi is not a strong trigger for T1D, but ASi particle which has surface adsorbed tetrahedrally coordinated zinc (ASiZn) is probably the trigger which has kept it’s secret up to date. Zn functions as address label which conducts the ASiZn particle to the beta cell, whose content of zinc is highest in the body. ASi particle adheres to membrane proteins distorting their tertiary structure revealing new epitopes. If the fetus has not met these epitopes at proper time during intrauterine development, the consequence is that the negative selection of lymphocytes in the thymus and bone marrow and fetal liver is not perfect. When a child later in postnatal life becomes predisposed to ASiZn particles the immune system reacts to these as to nonself proteins. As a consequence the insulin producing beta cells are destroyed.Many observations from diabetes research support the hypothesis, some to mentioned. 1. Three common autoantigens (ZnT8, ICA512/IA-2, GAD65) are membrane proteins whose function zinc regulates. 2. Geographical variation in Finland is convergent with surface water manganese concentrations. Manganese is the principal Zn scavenger and high manganese in water reduces ASiZn particle formation and the incidence of T1D. 3. The incidence of T1D depends of drinking water pH. The highest incidence can be found within water pH 6.2–6.9. Zn coordination changes from octahedral (unphysiologic) to tetrahedral (physiologic) at pH 6.56. In the text are presented five more supporting observations e.g. the similarity between the soils in Sardinia and Finland in respect to ASi.

Neurobehavioral function in school-age children exposed to manganese in drinking water.

Background: Manganese neurotoxicity is well documented in individuals occupationally exposed to airborne particulates, but few data are available on risks from drinking-water exposure.Objective: We examined associations of exposure from concentrations of manganese in water and hair with memory, attention, motor function, and parent- and teacher-reported hyperactive behaviors.Methods: We recruited 375 children and measured manganese in home tap water (MnW) and hair (MnH). We estimated manganese intake from water ingestion. Using structural equation modeling, we estimated associations between neurobehavioral functions and MnH, MnW, and manganese intake from water. We evaluated exposure–response relationships using generalized additive models.Results: After adjusting for potential confounders, a 1-SD increase in log10 MnH was associated with a significant difference of –24% (95% CI: –36, –12%) SD in memory and –25% (95% CI: –41, –9%) SD in attention. The relations between log10 MnH and poorer memory and attention were linear. A 1-SD increase in log10 MnW was associated with a significant difference of –14% (95% CI: –24, –4%) SD in memory, and this relation was nonlinear, with a steeper decline in performance at MnW > 100 μg/L. A 1-SD increase in log10 manganese intake from water was associated with a significant difference of –11% (95% CI: –21, –0.4%) SD in motor function. The relation between log10 manganese intake and poorer motor function was linear. There was no significant association between manganese exposure and hyperactivity.Conclusion: Exposure to manganese in water was associated with poorer neurobehavioral performances in children, even at low levels commonly encountered in North America.Citation: Oulhote Y, Mergler D, Barbeau B, Bellinger DC, Bouffard T, Brodeur ME, Saint-Amour D, Legrand M, Sauvé S, Bouchard MF. 2014. Neurobehavioral function in school-age children exposed to manganese in drinking water. Environ Health Perspect 122:1343–1350; http://dx.doi.org/10.1289/ehp.1307918

Core-cladding mode resonances of long period fiber grating in concentration sensor

Long period fiber grating (LPFG) is photoinduced fiber device that facilitates the coupling of core mode to different cladding modes resulting into series of transmission dips in the transmission spectrum. Here we present LPFG chemical sensor to determine the concentration of Manganese in water at ppm level. We fabricated LPFG of period 600µm in single mode communication fiber using 12W carbon dioxide laser applying point by point method. The fabricated LPFG is directly used as chemical sensor since cladding modes coupled to core mode directly come in contact with surrounding chemicals. Concentration of manganese in our collected sample is found to be 0.0329ppm. The result is verified with sophisticated Atomic Absorption Spectrometer (AAS).

Detection and determination of manganese concentration in water using a fiber Bragg grating coupled with nanotechnology

Through this paper we experimentally demonstrate the fabrication of a fiber Bragg grating (FBG) chemical sensor to detect and determine the manganese concentration in water and compare our results with sophisticated spectroscopic methods, such as atomic absorption spectrometry and the inductively coupled plasma method. Here we propose a simple method to develop a thin layer of gold nanoparticles above the etched grating region to enhance the sensitivity of the reflected spectrum of the FBG. By doing so, we achieve a sensitivity of 1.26 nm/parts per million in determining the trace level of Mn in water. Proper reagents are used to detect manganese in water.

Spatial and temporal variations of manganese concentrations in drinking water

The objective of this study was to assess the variability of manganese concentrations in drinking water (daily, seasonal, spatial) for eight communities who participated in an epidemiological study on neurotoxic effects associated with exposure to manganese in drinking water. We also assessed the performance of residential point-of-use and point-of-entry devices (POE) for reducing manganese concentrations in water. While the total Mn concentrations measured during this study were highly variable depending on the location (< 1 – 2,700 μg/L), daily or seasonal variations were minimal. Flushing the tap for 5 minutes did not significantly reduce total manganese concentration for 4 out of 5 sampling locations. The efficiency of reverse osmosis and ion exchange for total Mn removal was consistently high while activated carbon provided variable results. The four POE greensand filters investigated all increased (29 to 199%) manganese concentration, indicating deficient operation and/or maintenance practices. Manganese concentrations in the distribution system were equal or lower than at the inlet, indicating that sampling at the inlet of the distribution system is conservative. The decline in total Mn concentration was linked to higher water residence time in the distribution system.

オホーツク海中央海底の堆積物直上海水の全可溶マンガン・鉄濃度

オホーツク海中央部の堆積物直上海水中の全可溶マンガンや鉄濃度を調査する目的で，8本のマルチプルコア試料が採取された．堆積物直上海水のpH, 溶存酸素濃度，全可溶マンガン及び鉄量の測定を行なった．溶存酸素と全可溶鉄濃度には，強い負の相関が認められた．また，これまでの研究にて報告された結果と比べて，いくつかの地点では本研究で示された全可溶鉄量が比較的高いことが明らかとなった．以上から，これらの地点の海水－堆積物境界では比較的還元的な状態にあり，鉄が堆積物からが溶出していることが示唆される.

Manganese as a Potential Confounder of Serum Prolactin

de Burbure et al. (2006) elegantly demonstrated that dopaminergic markers in the serum, namely prolactin and homovanillic acid, are affected in children exposed to cadmium, lead, mercury, and arsenic. These findings, at low environmental exposure levels, reinforce the potential of these metals to perturb dopaminergic function and optimal development. In spite of the strengths of the article, de Burbure et al. (2006) overlooked an important potential confounder. Specifically, the authors should consider the possibility that manganese confounded their data; if so, the data set should be reexamined. A strong relationship between manganese exposure and serum prolactin levels has been raised in multiple studies. Although prolactin levels serve as a direct measurement of monoamines or their metabolites in peripheral tissues (e.g., blood platelets, plasma, urine), plasma prolactin is also an indirect indicator of dopaminergic functioning, a target for excessive exposure to manganese (Mutti and Smargiassi 1998; Smargiassi and Mutti 1999). A concordance between neurocognitive deficits and manganese exposure also exists, including a recent study in children exposed to water manganese concentrations exceeding 300 μg/L (Wasserman et al. 2006). A significant and positive correlation between blood manganese concentrations and prolactin levels in cord blood has also been established (Tasker et al. 2004). Other examples abound, although negative relationships between manganese and prolactin have also been reported (Roels et al. 1992). The potential that exposure to manganese contributed to or confounded the effects of the four metals on serum prolactin levels in the cohorts studied by de Burbue et al. (2006) should be considered. If samples are available for additional analysis, correlations between manganese exposure and prolactin would be beneficial and welcomed by various health forums as the debate on safe manganese exposure levels and sensitive health effect biomarkers continues.

Bioaccumulation of manganese in selected tissues of the freshwater crab, Potamonautes warreni (Calman), from industrial and mine-polluted freshwater ecosystems

Manganese concentrations in water and sediments of the Bronkhorstspruit River, Nooitgedacht Dam and especially in the Natalspruit River, did not fall within stated limits for the protection of aquatic life. Tissue manganese concentrations in Potamonautes warreni from the Natalspruit River were generally higher than those in the tissues of crabs from the other two aquatic ecosystems. The highest mean manganese tissue concentration in crabs from the three systems was detected in the carapace (587± 445 µg g-1 wet weight). It appears that the carapace in these animals acts as a sink in which manganese can be deposited, thus also playing an important role in the detoxification of manganese in these crustaceans. No seasonal or sex-related variation was detected. Body size of the crabs, however, seems to be an important influencing factor in manganese bioaccumulation. A significant increase in carapace manganese concentrations was detected with an increase in body size. However, muscle manganese concentrations were higher in the smaller groups. The concentration factors (BF) calculated for the different tissues with respect to the water were highest in the carapace and ranged from 280.9 to 742.8. The BF with respect to the sediment was comparatively low for all the tissues (0.1 to 0.7). As the manganese concentration in the tissues reflects to some extent the degree of manganese contamination of the surrounding aquatic environment, it appears that P. warreni may be useful as a potential biomonitor of manganese pollution.

Dissolved trace metals in the southwestern Indian Ocean

Dissolved trace metal concentrations are reported for a section in the southwestern Indian Ocean, extending from 7 to 27°S around the 56°E meridian. Overall distributions conform to those found in other oceans, with Cd, Cu, Ni and Zn showing recycled, or nutrient-like, behaviour, whereas Mn is enriched in the mixed layer relative to deep water. Deep-water concentrations of the recycled elements are intermediate between those for the North Atlantic and North Pacific Oceans, as would be expected from known patterns of deep-ocean circulation. For Cd and Zn, depletion in the surface layer approaches detection limits while for Cu and Ni significant near-surface concentrations (0.9 and 2.1 nM, respectively) are found. Relationships between the concentrations of metals and nutrients are similar to those described in the literature for the recycled metals for other regions, although significant variations exist from ocean to ocean. Maximum manganese concentrations in the upper water column are about or below 1 nM, as expected for a region remote from continental sources of airborne particulaet material. Minor variations in maximum concentration with latitude are evident as a result of the complex geochemistry of this element. Deep water manganese concentrations are uniformly low, showing no evidence for benthic or hydrothermal sources.