Uncontaminated Conditions Research Articles

Nanostructure-transportation relation to PEMFCs activity and durability degradation

The Proton exchange membrane (PEM) is a crucial component in the membrane electrode assembly (MEA), playing a vital role in providing a channel for water transport and acting as a bridge for proton conduction. However, during the long-term operation of fuel cells, PEM is susceptible to attack from metal ions such as Cr3+ originating from the corrosion of metallic bipolar plates, leading to changes in its transport properties. Here, we report on the impact of Cr3+ on the microstructure and mechanical properties of PEM and then correlate it with changes in water uptake and proton conductivity, studying the effect of Cr3+ contamination on fuel cell performance and durability. The study reveals that Cr3+ forms a dense cross-linking structure with sulfonic acid groups inside the ionomer, resulting in an increase in storage modulus due to the larger ion radius and higher valence state, leading to a decrease in water uptake and proton conductivity. The membrane transport properties are primarily dependent on its water content. It is observed that Cr3+ contamination reduced the fuel cell voltage and maximum power density by 47.6 % and 57.1 %, respectively, with a voltage attenuation rate up to 2.9 mV/h, nearly 14 times that of the uncontaminated condition (0.21 mV/h). These findings provide valuable insights for developing high-transmission PEMs and aid in predicting the degradation and lifespan of fuel cells under actual operating conditions.

Evaluation of heavy metal contamination in the tidal flat sediments of Nantong, East China

Heavy metals in sediments from the tidal flats of northern Nantong are investigated for the first time. Twelve sediment cores were analyzed to learn the vertical profiles of heavy metals. Averagely, the sediment cores contain 67.77 mg/kg of Cr, 20.13 mg/kg of Cu, 61.95 mg/kg of Zn, 0.13 mg/kg of Cd, 16.49 mg/kg of Pb, 7.36 mg/kg of As, and 0.005 mg/kg of Hg. To assess the contamination levels of heavy metals, geo-accumulation index (Igeo) and enrichment factor (EF) values were calculated. The Igeo values of heavy metals range from −6.721 to 0.957, showing that most sediments are in uncontaminated condition and a few are moderately contaminated by heavy metals. EF values of most samples are smaller than 1.5, which indicates that most heavy metals in the samples are from natural weathering processes. Also, Pearson correlation coefficients and principal component analysis is applied to find out the sources of the heavy metals. The correlation further indicates that Pb, As, and Hg are likely from natural weathering processes while Cu, Cr, and Zn have both natural and a small portion of anthropogenic sources. Additionally, anthropogenic sources such as vehicles and agricultural irrigations mainly contribute to the slight Cd contamination in Haimen tidal flats.

Heavy metals, radionuclides activity and mineralogy of soil samples from an artisanal gold mining site in Ile-Ife, Nigeria: implications on human and environmental health

The Ife-Ilesha schist belt of the Nigerian Basement Complex is renowned for artisanal gold mining activities owing to the occurrence of gold-bearing eluvial deposits within and around the belt. However, gold mining operations in Ile-Ijesha axis are carried out haphazardly without consideration of probable health risks that might be posed to the miners and local community by heavy metals and naturally occurring radionuclides materials (NORMs) contents in the soil. This study was therefore conducted to determine the mineralogy, heavy metals contents and radionuclide activity of soil samples collected from a gold mining site in Ile-Ife with a view to assessing the consequential health and radiological risks. Thirty-five (35) soil samples were collected from abandoned and active excavating pits over the entire area using stainless-steel spade. The heavy metals and radionuclides concentrations and mineralogical compositions of the samples were obtained by Atomic Absorption Spectroscopic (AAS), gamma ray spectrometry and X-ray diffraction (XRD) methods, respectively. The contamination indices consisting of Enrichment Factor (EF) and Index of geoaccumulation (Igeo) were calculated from heavy metals concentrations. The sequence of the average concentrations of heavy metals in the soil samples decreases as follows: Pb (72.93 ± 4.60) > Cd (58.26 ± 3.25) > Cr (42.81 ± 3.00) > Zn (33.66 ± 2.71) > Mn (24.60 ± 1.80) > Ni (23.93 ± 2.51). The mean EF values of the measured heavy metals occurred in the order of Cr > Pb > Zn > Cd > Ni. The Igeo values of the measured heavy metals (except Pb) were less than one (< 1) revealing practically uncontaminated condition of the studied soil. The radiation dose and radiological hazard risks were estimated by employing absorbed dose, effective dose, radium equivalent, gamma index, external hazard index, excess life cancer risk and representative level. The hazard index values of all the measured heavy metals were < 1 indicating no significant non-carcinogenic effects. The average activity concentrations of 40 K, 238U and 232Th are 259.23 ± 84.20 Bqkg−1, 185.48 ± 73.31 Bqkg−1, 11.93 ± 4.68 Bqkg−1, respectively. All the radiological indices were below the world average values stipulated by the radiation monitoring bodies. The result of the XRD indicates the preponderance of quartz, and biotite, as well as subordinate amounts of plagioclase, kaolinite, ilmenite, andradite, actinolite and microcline in the soil samples, pointing to a schistose source rock, which is probably gold-bearing. The current study indicated practically low contamination of the Ile-Ife gold mining site soils by heavy metals, low radiological risk from NORMs and prospect of mineral exploration in the area if well-established procedure is followed.

Exposure to copper during larval development has intra- and trans-generational influence on fitness in later life

Anthropogenic pollution has a disadvantageous influence on various life-history traits. Although direct effects are well known, potential fitness-related trans-generational costs are less studied. Previously, empirical findings have demonstrated that environmental conditions faced by the parental generation have an effect on the traits expressed by their offspring. Here, to study this conjecture larvae of the common fruit fly (Drosophila melanogaster) were either exposed to a sub-lethal concentration of copper or reared on uncontaminated larval medium. Adult flies were kept under uncontaminated conditions. For the next generation, individuals were mated with their own group and their offspring were either exposed to copper or fed with uncontaminated larval medium. We found that in the parental generation copper exposure reduced fecundity compared with uncontaminated controls. In the progeny, females suffered impaired fecundity only if their larval condition differed from the conditions experienced by their parents. If the progeny was raised under similar conditions than the parental generation, no effect on fecundity was discovered, suggesting acclimatization to the prevailing conditions after short-time copper exposure (two generations). Our results demonstrate that exposure to an environmental stressor like heavy metals causes intra-and trans-generational fitness costs. Further, individuals may be able to acclimatize in prevailing contaminated conditions, but this might in turn debase fitness under uncontaminated conditions. Our findings are consistent with the prediction of the adaptive parental effects hypothesis which states that parents may produce offspring that are more successful under conditions faced by their parents.

Effects of a Systemic Pesticide Along an Aquatic Tri-Trophic Food Chain.

Systemic pesticides, such as the neonicotinoid imidacloprid, can be introduced into aquatic ecosystems through contaminated plant material, which is the basis for detrital (brown) aquatic food-webs. With the aim of exemplarily assessing for indirect effects on the level of predators, we first offered imidacloprid contaminated and uncontaminated alder leaves to the stonefly shredder Protonemura sp. for 72 h. Shredder survival, leaf decomposition, body length and biomass were all between 20% and 50% lower under imidacloprid exposure compared to uncontaminated conditions, indicating physiological implications. Subsequently, these shredders were provided as prey to stonefly predators (Isoperla sp.) kept in cages in a stream. Predator biomass and length decreased by up to 11% and 4.3%, respectively, when feeding on imidacloprid exposed prey. Our study hence suggests that plant material contaminated with systemic pesticides can exert adverse effects in aquatic predators when preying on shredders consuming such leaves, which warrants a further consideration of this pathway.

Does the previous exposure to copper alter the pattern of avoidance by zebrafish in a copper gradient scenario? Hypothesis of time-delayed avoidance due to pre-acclimation

The traditional ecotoxicity assays (forced exposure) tend to use organisms that are cultured under controlled conditions or that come from undisturbed ecosystems, with no (or negligible) previous contact with contamination. The same occurs in the non-forced approach, in which organisms are exposed to a contamination gradient and can move between different concentrations choosing the less toxic one. Considering that organisms inhabiting contaminated ecosystems tend to be gradually exposed to contamination, an abrupt exposure from uncontaminated conditions to a contaminated environment might present two problems: lack of ecological relevance to a scenario where the contamination occurs gradually and a magnification of the toxicity due to the sudden change in the environmental conditions. Therefore, a key question should be addressed: might a previous exposure to contamination reduce the organisms' perception of the danger of a contaminant (hypothesis of time-delayed avoidance due to pre-acclimation-TDADP), altering their avoidance response pattern? We tested the avoidance of zebrafish (Danio rerio: ±2 months old) populations when exposed to a copper gradient (0–400 μg/L). The populations differed according to the period (24 h and 7 and 30 days) in which they were acclimated to copper (ca. 400 μg/L). The avoidance in the 2 h experiments changed as a consequence of the acclimation period. In the population that was not previously acclimated, 40% of the fish moved to the less contaminated compartment and only 6.7% stayed in the most contaminated one; for the other populations those values were, respectively, 31 and 11% (24 h-acclimation), 28 and 26% (7 day-acclimation) and 19 and 27% (30 day-acclimation). An abrupt exposure to a contaminant might overestimate the response if this is analyzed in the short-term. When the avoidance tests were prolonged to 24 h, the avoidance tended to reach similar values to those of the non-acclimated population, thus supporting our TDADP hypothesis.

Distributions of endocrine cell clusters during porcine pancreatic development.

BackgroundPancreatic islet xenotransplantation is a potential treatment for diabetes mellitus, and porcine pancreas may provide a readily available source of islets. Islets in juvenile pigs are smaller than those in young adult pigs, but the insulin content is very similar. In addition, as juvenile pigs are more easily reared in uncontaminated conditions, many researchers have conducted studies using pancreatic islets from juvenile pigs. We aimed to analyze the distributions of endocrine cell clusters by comprehensively evaluating juvenile porcine pancreatic development and to propose an appropriate age at which islets could be isolated from the juvenile porcine pancreas.MethodsSplenic (SL) and duodenal lobe (DL) samples were collected from the pancreases of pigs aged 0–180 days (n = 3/day after birth). The chronological changes in endocrine cell clustering were analyzed in relation to morphological changes, cell characterization, numbers, islet areas, and gene expression.ResultsIn juvenile pigs aged 0–21 days, the pancreas contained numerous endocrine cells, and compact islets appeared from 21 days of age. Well-defined small islets were seen at 28 days of age, and the clusters were denser in the SL than in the DL. At 35 days of age, the islets were morphologically similar to those observed at 180 days of age, and the greater number of islets was similar to that seen at 90 days of age. The differences in the islets’ cytoarchitecture between the lobes were negligible. The expression of β-cell-related genes was higher in the juvenile pancreas than in the adult pancreas, and the expression of neurogenin-3 decreased dramatically over time.ConclusionsThese findings may have implications for attempts to refine the most appropriate age for islet isolation from porcine donors. Focusing on porcine pancreatic islets isolated at around 35 days after birth may offer benefits regarding their xenotransplantation potential.

Assessment of sperm DNA integrity within the Palaemon longirostris (H. ) population of the Seine estuary

The interpretation of biomarkers in natura should be based on a referential of expected values in uncontaminated conditions. Nevertheless, to build a reference data set of biomarker responses in estuarine areas, which receive chronic pollution loads due to their transition position between continent and sea, is impossible. In this context, the aim of the present work was to propose the use of laboratory recovery period to define a baseline for the measurement of sperm DNA damage by Comet assay in the estuarine prawn Palaemon longirostris. For that, sperm DNA integrity was observed after both a passive (i.e. 20 days in a clean environment) and an active (i.e. forced renewal of spermatophores) recovery of wild P. longirostris specimens from the Seine estuary, in laboratory conditions. Then, the levels of sperm DNA damage recorded within the P. longirostris population of the Seine estuary, during six campaigns of sampling from April 2015 to October 2017, have been interpreted according to the defined threshold values. The results showed a persistence in the level of DNA damage after 20-day in clean environment with the passive recovery. This strategy was inconclusive to reach a baseline level but it revealed the lack of DNA repair mechanisms. For the active recovery, a decrease of 54% of the level of DNA damage has been observed after the first renewal of spermatophores and this level stabilized after the second renewal. On the basis of this second strategy, we defined a mean basal value of sperm DNA damage of 54.9 A.U. and a maximum threshold of 69.7 A.U. (i.e. 95 %CI). The analysis of the results using the reference value highlighted significant abnormal sperm DNA damage within the native population of P. longirostris from the Seine estuary on all stations during the six-sampling campaigns.

Seasonal and spatial changes in water and sediment quality variables in Bafa Lake

The brackish Bafa Lake located in the southwestern part of Turkey is under stress because of both natural and untreated wastewater effluents. The purpose of this research is to determine spatiotemporal distributions of some physicochemical variables in water column (temperature, salinity, pH, conductivity, dissolved oxygen, NH4–N, NO2–N, NO3–N, oPO4–P, TPO4–P, chlorophyll-a, total suspended solids) and sediment (TN, TC, TOC, TP) and their relationships at coastal stations. In the water column, nitrate and phosphate concentrations showed seasonal variations with high values recorded in winter period. Ammonium was determined as a main source of TIN component. During summer period, a large amount of total phosphorus was found as dissolved organic form. However, in the winter period, inorganic phosphate levels increased at sampling stations. N limitation was a common feature throughout the lake where P-limitation was only observed in summer period. The total phosphorus levels which showed hypereutrophic condition at the western part of the lake changed between 1.55 and 4.99 μM and did not remain in the range for uncontaminated condition. In the lake sediment, a strong relationship was found between TOC and TC levels. Generally, the mean TOC concentrations constitute small amount of TC values in the sampling stations. The results also indicated that a strong correlation exists between TOC and TN values, and TN was greatly regulated by organic sources. In the lake, TOC:TN ratios changed between 5 and 13; the ratio greater than 10 could be an indicator of algal and land plant sources mixing as an organic matter.

2D sandbox experiments of surfactant foams for mobility control and enhanced LNAPL recovery in layered soils

The ability of surfactant foam to enhance mobility control and LNAPL recovery in a heterogeneous porous media was investigated through sandbox experiments with p-xylene used as LNAPL. A layered heterogeneous porous media was represented in a 2D sandbox filled with two layers of coarse and medium silica sand. Based on previous tests, the surfactant solution used was Ammonyx Lo at a concentration of 0.1% (w/w). The sandbox experimental program included tracer tests done under both uncontaminated and contaminated conditions, foam injection under uncontaminated conditions and surfactant solution and foam injection under contaminated conditions. Tracer tests indicated that the permeability contrast between sand layers was increased by LNAPL contamination. Foam injection under uncontaminated conditions presented a S-shaped front that indicated a better mobility control than the piston-shaped front obtained during tracer tests. During foam injection, complete sweep of the sandbox was achieved with 1.8pore volume (PV) compared to 2.8PV during tracer injection, thus indicating better mobility control with foam. Pre-flush of the contaminated sandbox with surfactant solution initiated p-xylene mobilization but no free phase was recovered at the effluent. A negligible p-xylene residual saturation was reached following foam injection in the contaminated sandbox. However, mass balance indicated a total recovery of only 48% of the initial p-xylene, thus indicating an underestimation of the recovery by volatilization. Recovery by volatilization was corrected, which gave the following proportions of LNAPL recovery mechanisms: 19% by mobilization, 16% by dissolution and 65% by volatilization. Results show the potential efficiency of foam remediation of LNAPL source zones in heterogeneous porous media. Still, further developments are needed prior to field scale application, which could benefit from in situ foam production that would simplify on-site operations.

Effects of Elevated In Ovo Selenium Exposure on Late Stage Development of Xenopus laevis Tadpoles.

The effects of elevated in ovo selenium (Se) exposure on late stage larval Xenopus laevis development were investigated. Adult females were fed diets augmented with selenomethionine for 68days and bred with untreated males to obtain embryos with measured concentrations of 1.6 (control), 10.8, 28.1 and 81.7μgSe/g dry mass. Embryos were reared under uncontaminated conditions until 50% of individuals within an aquarium had completed metamorphosis. The highest in ovo Se exposure group exhibited greater froglet body mass and snout to vent length while having a higher proportion of tadpoles at earlier stages of development. No differences were detected among treatment groups for mortality or metamorphic timing during the rearing period. This research suggests that in ovo Se exposure has minimal effect on the survival and development of late stage larval X. laevis in a controlled laboratory environment with adequate food availability.

Effect of heavy metals combined stress on growth and metals accumulation of three Salix species with different cutting position

ABSTRACTThis study aimed to compare growth performance and heavy metal (HM) accumulation at different cutting positions of Salix species grown in multi-metal culture. Three Salix species stems cut at different positions (apical to basal) were grown hydroponically for four weeks. The plants were then treated for three weeks with 0, 5, 10, and 20 μM Cd, Cu, Pb, and Zn, resulting in total metal concentrations of 0, 20, 40, and 80 μM. The growth parameters and HM content in shoots and initial cutting were measured. Results showed that, compared with S. fragilis, S. matsudana grew more poorly in uncontaminated condition but grew better and accumulated lower metal in shoots under mixed HM treatment. In addition, cuttings from apical parent stem position exhibited poorer growth performance before and after treatment, as well as greater metal content in shoots than base parts under the HM treatment. These results suggest that S. matsudana may undergo a special mechanism to hinder metals in the initial cutting, thus mitigating growth damage. The apical portion also showed poor resistance against the invasion of mixed HMs because of the immature structure. Therefore, in the selection of phytoremediation plants, metal accumulation ability is not proportional to growth performance.

Combination effects of pyrethroids and neonicotinoids on development and survival of Chironomus riparius

Standard ecotoxicological risk assessments are conducted on individual substances, however monitoring of streams in agricultural areas has shown that pesticides are rarely present alone. In fact, brief but intense pulse events such as storm water runoff and spray drift during application subject freshwater environments to complex mixtures of pesticides at high concentrations. This study investigates the potential risks to non-target aquatic organisms exposed to a brief but intense mixture of the neonicotinoid pesticides imidacloprid and thiacloprid and the pyrethroid pesticides deltamethrin and esfenvalerate, compared to single substance exposure. All four of these pesticides have been detected in surface waters at concentrations higher than benchmark values and both classes of pesticides are known to exert adverse effects on non-target aquatic organisms under single substance exposure scenarios. First instar midge larvae of the non-target aquatic organism, Chironomus riparius, were exposed to combinations of these four pesticides at 50% of their LC50 (96h) values in a 1h pulse. They were then reared to adulthood in uncontaminated conditions and assessed for survival, development time and fecundity. Our results show that the risk of disruption to survival and development of non-target aquatic organisms under this scenario is not negligible on account of the significant increases in mortality of C. riparius found in the majority of the pesticide exposures and the delays in development after pyrethroid exposure. While none of the deleterious effects appear to be amplified by combination of the pesticides, there is some evidence for antagonism. No effects on fecundity by any of the pesticide treatments were observed.

Shear bond strength of moisture-insensitive and self-etching primers under contaminated and uncontaminated conditions

The bonding procedure in orthodontics is an important aspect that leads to a successful outcome of the treatment. Traditionally the bonding procedure demands for the least contaminated field. This procedure is technically sensitive due to the presence of various contaminants in the operative field such as moisture and saliva. Various bonding materials have evolved to overcome the difficulties in the bonding procedures such as the Moisture-Insensitive Primer (MIP) and Self-Etching Primer (SEP) with orthodontic adhesives, Composite and Resin modified glass ionomer cement (RMGIC). The shear bond strengths of these materials were examined in our study. Fresh extracted 80 human premolars were collected and divided equally into 8 groups of 10 teeth each, and brackets were bonded with composite and RMGIC under different experimental conditions such as groups (1) etch/dry/MIP/composite, (2) etch/dry/MIP/saliva/composite, (3) etch/dry/MIP/RMGIC (4) etch/dry/MIP/saliva/RMGIC, (5) dry/SEP/composite, (6) dry/SEP/saliva/composite, (7) dry/SEP/RMGIC, (8) dry/SEP/saliva/RMGIC. The shear bond strength of each sample was tested with a universal testing machine. The bond strength in the uncontaminated groups had the highest mean shear bond strengths when compared to the contaminated groups although there was no significant difference in bond-failure sites amongst the 8 experimental groups. The composite with SEP have higher bond strength up to 16.66 MPa in an uncontaminated field as compared to all other groups. The self etching primer with resin modified glass ionomer cement showed higher bond strength up to 12.79 MPa compared to other groups of salivary contamination. The presence of saliva contamination significantly lowers the shear bond strength of all groups of bonding procedures. Although contamination plays a major setback in bonding procedures, the bond strength of these newer products remains acceptable in most of the conditions

Copper tolerance mechanisms of Mesorhizobium amorphae and its role in aiding phytostabilization by Robinia pseudoacacia in copper contaminated soil.

The legume-rhizobium symbiosis has been proposed as an important system for phytoremediation of heavy metal contaminated soils due to its beneficial activity of symbiotic nitrogen fixation. However, little is known about metal resistant mechanism of rhizobia and the role of metal resistance determinants in phytoremediation. In this study, copper resistance mechanisms were investigated for a multiple metal resistant plant growth promoting rhizobium, Mesorhizobium amorphae 186. Three categories of determinants involved in copper resistance were identified through transposon mutagenesis, including genes encoding a P-type ATPase (CopA), hypothetical proteins, and other proteins (a GTP-binding protein and a ribosomal protein). Among these determinants, copA played the dominant role in copper homeostasis of M. amorphae 186. Mutagenesis of a hypothetical gene lipA in mutant MlipA exhibited pleiotropic phenotypes including sensitivity to copper, blocked symbiotic capacity and inhibited growth. In addition, the expression of cusB encoding part of an RND-type efflux system was induced by copper. To explore the possible role of copper resistance mechanism in phytoremediation of copper contaminated soil, the symbiotic nodulation and nitrogen fixation abilities were compared using a wild-type strain, a copA-defective mutant, and a lipA-defective mutant. Results showed that a copA deletion did not affect the symbiotic capacity of rhizobia under uncontaminated condition, but the protective role of copA in symbiotic processes at high copper concentration is likely concentration-dependent. In contrast, inoculation of a lipA-defective strain led to significant decreases in the functional nodule numbers, total N content, plant biomass and leghemoglobin expression level of Robinia pseudoacacia even under conditions of uncontaminated soil. Moreover, plants inoculated with lipA-defective strain accumulated much less copper than both the wild-type strain and the copA-defective strain, suggesting an important role of a healthy symbiotic relationship between legume and rhizobia in phytostabilization.

Effects of saliva contamination on bonding performance of self-etching adhesives

Purpose: This study investigated the effects of saliva contamination on bonding performance of two self-etching adhesives. Materials and Methods: Forty caries-free extracted human third molars’ cusps were cut off to expose mid-coronal dentin surfaces. Two one-step self-etching adhesives and the respective resin composite from the same manufacturer (Adper Easy One + Filtek Z350 (3 M ESPE); Clearfil S3 Bond + Clearfil Majesty (Kuraray Co.)) were applied onto the dentin surfaces for micro-tensile bond strength (MTBS) test. The dentin surfaces were not contaminated (A), were contaminated with saliva before/after priming (B/C), or they were water-sprayed after saliva contamination occurred before/after priming (D/E). The resin–dentin interfaces were analyzed by scanning electron microscopy. After the two adhesives were polymerized on saliva-contaminated or uncontaminated conditions, they were determined by Fourier transform infrared spectroscopy for degree of conversion (DC), and analyzed by AFM spectroscopy for spatial homogeneity of the adhesives. The data were analyzed using factorial design ANOVA and one-way ANOVA. Results: Compared with control group (A), the saliva contamination after priming significantly reduced both dentin MTBS (p < 0.05). Thorough water-spraying could significantly improve the MTBS of the saliva-contaminated dentin (p < 0.05) or completely restore it. Saliva contamination deteriorated the resin–dentin adaptation, DC, and spatial homogeneity of adhesives. Conclusions: Saliva contamination had a negative effect on bonding performance of self-etching adhesives regarding their dentin MTBS, resin–dentin adaptation, DC, and spatial homogeneity. However, the effect of saliva contamination on the dentin MTBS was related to the individual adhesive used and the time point of contamination.

Total phosphorus reference condition for subalpine lakes: A comparison among traditional methods and a new process-based watershed approach

Different methods for estimating the total phosphorus (TP) reference conditions of lakes have rarely been compared. This work tests the uncertainty and accuracy of the most frequently used approaches (Morpho-edaphic index -MEI-, export coefficient, diatoms and pigment-inferred TP models) for 35 subalpine lakes. Furthermore, we propose a new process-based watershed approach that was tested on a subalpine environment and consists of combining a space for time substitution with a space for space substitution. The possible presence of uncontaminated or less contaminated environments inside or next to the watershed can be exploited by training a hydrological transport watershed model according to the uncontaminated conditions and then applying the calibration to the entire watershed, which reconstructs a natural or semi-natural TP load scenario. We found that the root mean square error (RMSE) for the MEI is 4 μg L−1. However, its application is limited for lakes that present with an alkalinity ≤1 meq L−1. For lakes with a higher alkalinity, we observed a loss of predictive capability that results from the lower solubility of phosphorus under conditions of high calcium content. The export coefficient model was applied with a mean export coefficient and presents similar prediction capabilities as the MEI. The chlorophyll-inferred TP model shows a higher uncertainty (RMSE = 8 μg L−1); however, it produced fewer underestimations and overestimations. With regards to the diatom-inferred TP model, we are only able to evaluate an uncertainty of 5 μg L−1 at the European level. Finally, the proposed process-based watershed approach adequately predicted the reference condition of the selected lake and had an uncertainty lower than the other methods (2 μg L−1). We conclude by revealing the potential and limitations of this approach in the field of ecological lake modelling more and more attracted by TP pristine load inputs in studies on the effects of climate change and eutrophication of lakes.

Effect of cadmium on growth, photosynthesis, mineral nutrition and metal accumulation of bana grass and vetiver grass

An experiment was conducted to evaluate the differential effects of Cd contamination on the growth, photosynthesis, mineral nutrition and Cd accumulation of bana grass (Pennisetum americanum×Pennisetum purpureum) and vetiver grass (Vetiveria zizanioides). Bana grass accumulated 48–453 and 25–208mgkg−1 in plant roots and shoots, respectively, at 15–100mgkg−1 soil Cd concentration, while vetiver grass accumulated 167–396 and 0.13–9.0mgkg−1. These results indicated that bana grass was a Cd accumulator while vetiver grass was a Cd excluder. The ratio of root to shoot biomass was significantly increased in vetiver grass, while it was unchanged in bana grass by Cd pollution. This suggests that excluders may allocate more energy to roots than shoots under Cd pollution compared to un-contaminated condition, while accumulators may allocate equal proportions of energy to roots and shoots. For bana grass, soil Cd pollution significantly decreased the concentration of Fe and Mn in roots as well as the translocation factors of Zn and K. For vetiver grass, soil Cd pollution significantly decreased the concentration of Fe in roots and had no influence on the translocation factors of Fe, Mn, Cu, Zn, Mg, K and Ca. Soil Cd pollution showed no significant effect on chlorophyll content and photosynthetic rates in either of the grasses. The water content and leaf transpiration rate were significantly increased by Cd pollution in bana grass, while they were unchanged in vetiver grass. The results indicated that the energy allocation and mineral nutrition characteristics may aid in screening suitable plant species for phytoremediation.

Contamination of Heavy Metals and other Organic Pollutants in Perna viridis from the Coastal Waters of Malaysia: A Review Based on 1998 Data

Since 1990s until today, the Asia-Pacific Mussel Watch approach has been widely used for biomonitoring purpose in Malaysia by using the green-lipped mussel Perna viridis in particular. This paper reviewed the concentrations of heavy metals (Cd, Cu, Pb and Zn), Linear Alkylbenzenes (LABs), Polycyclic Aromatic Hydrocarbons (PAHs), phenolic Endocrine Disrupting Chemicals (EDCs) [nonylphenol (NP), octylphenol (OP), and bisphenol A (BPA)] and organochlorine (OC) compounds (PCBs, DDTs, CHLs, HCHs and HCB) in nine mussel populations collected in 1998 (because I involved in the sampling field trip when I was a trainee researcher) from the coastal waters of Malaysia. In fact, all of these data were published separately in five different peer-reviewed journals in the literature (see Yap et al. [6,7]; Tsutsumi et al. [14]; Isobe et al. [15]; Monirith et al. [16]). Since they discussed only based on the group of contaminants which they focused upon, this review paper aimed to see a holistic picture and understanding of the impacts of the different chemical contaminants in relation to the description of the sampling sites. Based on seven mussel populations with complete 11 chemicals (ranging from heavy metals, LABs, PAHs, phenolic EDCs and OCs), a dendrogram was established using single linkage cluster analysis. A dendrogram was established using single linkage cluster analysis showing two major subclusters. The first subcluster comprised Tanjung Rhu, Trayong, Kuala Penyu and Pasir Panjang populations, indicating relatively uncontaminated conditions while the other subcluster consists of Penang, Kg. Pasir Puteh and Anjung Batu which indicated contaminated conditions as it is well supported by the elevated levels of some chemicals. The subcluster combining Penang and Kg. Pasir Puteh populations were mainly due to the elevated levels of LABs and PAHs in both sites while Kg. Pasir Puteh also had elevated levels of Cu, Pb, PCBs and CHLs. Anjung Batu, which is also clustering together with Penang and Kg. Pasir Puteh population can be explained by its elevated levels of three OC compounds namely DDTs, CHLs and HCHs.

Enhancing Degradation of Total Petroleum Hydrocarbons and Uptake of Heavy Metals in a Wetland Microcosm Planted with Phragmites Communis by Humic Acids Addition

The effects of humic acid (HA) on heavy-metal uptake by plants and degradation of total petroleum hydrocarbons (TPHs) in a wetland microcosm planted with Phragmites communis were evaluated by comparing waterlogged soils and water-drained upland soils. Experiments were conducted on soils artificially contaminated with heavy metals (Pb, Cu, Cd, Ni) and diesel fuel. HA showed a positive influence on biomass increase for all conditions, but more for belowground than aboveground biomass, and lower in contaminated than uncontaminated soil. The bioavailability and leachability factor (BLF) for all heavy metals except Ni increased with HA addition in both the control and the P. communis planted microcosms, suggesting that more heavy metals could be potentially phytoavailable for plant uptake. Microbial activities were not affected by both heavy metals and TPH contamination, and HA effects on stimulating microbial activities were much greater in the contaminated soil than under uncontaminated conditions. HA addition enhanced the degradation of TPH and n-alkane in waterlogged conditions. The results show that HA can increase the remedial performance in P. communis dominated wetlands simultaneously contaminated with heavy metals and petroleum hydrocarbons and thus prevent contamination of groundwater or other adjacent ecosystems.