Lowest Effect Level Research Articles

Relative Impact of Incorporating Pharmacokinetics on Predicting In Vivo Hazard and Mode of Action from High-Throughput In Vitro Toxicity Assays

The use of high-throughput in vitro assays has been proposed to play a significant role in the future of toxicity testing. In this study, rat hepatic metabolic clearance and plasma protein binding were measured for 59 ToxCast phase I chemicals. Computational in vitro-to-in vivo extrapolation was used to estimate the daily dose in a rat, called the oral equivalent dose, which would result in steady-state in vivo blood concentrations equivalent to the AC 50 or lowest effective concentration (LEC) across more than 600 ToxCast phase I in vitro assays. Statistical classification analysis was performed using either oral equivalent doses or unadjusted AC 50 /LEC values for the in vitro assays to predict the in vivo effects of the 59 chemicals. Adjusting the in vitro assays for pharmacokinetics did not improve the ability to predict in vivo effects as either a discrete (yes or no) response or a low effect level (LEL) on a continuous dose scale. Interestingly, a comparison of the in vitro assay with the lowest oral equivalent dose with the in vivo endpoint with the lowest LEL suggested that the lowest oral equivalent dose may provide a conservative estimate of the point of departure for a chemical in a dose-response assessment. Furthermore, comparing the oral equivalent doses for the in vitro assays with the in vivo dose range that resulted in adverse effects identified more coincident in vitro assays across chemicals than expected by chance, suggesting that the approach may also be used to identify potential molecular initiating events leading to adversity.

Toxicity of five antibiotics and their mixtures towards photosynthetic aquatic organisms: Implications for environmental risk assessment

The individual and combined toxicities of amoxicillin, erythromycin, levofloxacin, norfloxacin and tetracycline have been examined in two organisms representative of the aquatic environment, the cyanobacterium Anabaena CPB4337 as a target organism and the green alga Pseudokirchneriella subcapitata as a non-target organism. The cyanobacterium was more sensitive than the green alga to the toxic effect of antibiotics. Erythromycin was highly toxic for both organisms; tetracycline was more toxic to the green algae whereas the quinolones levofloxacin and norfloxacin were more toxic to the cyanobacterium than to the green alga. Amoxicillin also displayed toxicity to the cyanobacterium but showed no toxicity to the green alga. The toxicological interactions of antibiotics in the whole range of effect levels either in binary or multicomponent mixtures were analyzed using the Combination Index (CI) method. In most cases, synergism clearly predominated both for the green alga and the cyanobacterium. The CI method was compared with the classical models of additivity Concentration Addition (CA) and Independent Action (IA) finding that CI could accurately predict deviations from additivity. Risk assessment was performed by calculating the ratio between Measured Environmental Concentration (MEC) and the Predicted No Effect Concentration (PNEC). A MEC/PNEC ratio higher than 1 was found for the binary erythromycin and tetracycline mixture in wastewater effluents, a combination which showed a strong synergism at low effect levels in both organisms. From the tested antibiotic mixtures, it can be concluded that certain specific combinations may pose a potential ecological risk for aquatic ecosystems with the present environmentally measured concentrations.

Elimination Kinetics of Domoic Acid from the Brain and Cerebrospinal Fluid of the Pregnant Rat

Domoic acid (DA) causes neurological effects in multiple species upon exposure, including status epilepticus in pregnant sea lions and an epileptic disease state that commonly develops in juveniles. This study aims to define brain toxicokinetic parameters in the pregnant rat in the larger context of maternal-fetal toxin transfer. Specifically, Sprague-Dawley rats were exposed to a low observable effect level of 1.0 mg DA/kg intravenously at gestational day 20, and plasma, brain, and cerebrospinal fluid (CSF) samples were taken at discrete time points over 24 h. Domoic acid concentrations were determined by a tandem LC/MS method recently optimized for brain tissue and CSF. Data showed that 6.6% of plasma DA reached the brain, 5.3% reached the CSF, and DA levels were nearly identical in both brain and CSF for 12 h, remaining above the threshold to activate isolated hippocampal neurons for 2 h. The calculated terminal half-life of CSF was 4 h, consistent with the time for complete CSF regeneration, suggesting that CSF acts as a mechanism to clear DA from the brain.

Acute toxicity of naturally and chemically dispersed oil on the filter-feeding copepod Calanus finmarchicus

Following oil spills in the marine environment, natural dispersion (by breaking waves) will form micron-sized oil droplets that disperse into the pelagic environment. Enhancing the dispersion process chemically will increase the oil concentration temporarily and result in higher bioavailability for pelagic organisms exposed to oil-dispersant plume. The toxicity of dispersed oil to pelagic organisms is a critical component in evaluating the net environmental consequences of dispersant use or non-use in open waters. To assess the potential for environmental effects, numerical models are being used, and for these to reliably predict the toxicity of chemically dispersed oil, it is essential to know if the dispersant affects the specific toxicity of the oil itself. In order to test the potential changes in specific toxicity of the oil due to the presence of chemical dispersant, copepods (Calanus finmarchicus) were subjected to a continuous exposure of chemically (4 percent Dasic w/w dispersant) and naturally dispersed oil (same droplet size range and composition) for four days. On average the addition of dispersant decreased 96h LC50-values by a factor of 1.6, while for LC10 and LC90 these factors were 2.9 and 0.9, respectively. This indicates that after 96h of exposure the dispersant slightly increased the specific toxicity of the oil at median and low effect levels, but reduced the toxicity at high effect levels. Decreased filtrations for the exposed groups were confirmed using particle counting and fluorescence microscopy. However, no differences in these endpoints were found between chemically and naturally dispersed oil. The ultimate goal was to evaluate if models used for risk and damage assessment can use similar specific toxicity for both chemically and naturally dispersed oil. The slight differences in toxicity between chemically and naturally dispersed oil suggest that risk assessment should be based on the whole concentration response curve to ensure survival of C. finmarchicus.

Evaluation of trace element concentration (acid leachable) in sediments from River Pánuco and its adjacent lagoon areas, NE México

A set of forty-one surface sediment samples were collected in River Panuco and its adjoining lagoon areas in NE Mexico to identify the enrichment pattern of trace elements. The samples were analyzed for sediment texture, carbonates, organic carbon and acid leachable trace elements (ALTEs) using autoclave method [Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd, V, Be, Ba, Sr, As]. Geochemical results of Fe, Cr, Ni, Co, V and Sr in zone 1 indicate that erosion in the upland region (Sierra Madre Oriental Mountains) is very high. The above feature is supported by the supremacy of finer sediments (82.12 %), carbonates (44.67 %) and organic carbon (10.74 %), which are brought down from the drainage basin. The overall average concentration of ALTEs Mn (607 μg g−1), Cu (28.29 μg g−1), Ni (16.56 μg g−1), Pb (46.11 μg g−1), Cd (1.81 μg g−1) and Zn (92.18 μg g−1) indicates higher values than the lowest effect level (LEL) and effects range low (ERL) of environmental indicators. The results suggest that they are due to the increase in oil refineries, metal based industries, shipping activities and the effluent input which could enter the biological cycle and might create human health problems.

Polychlorinated biphenyls (PCBs) in the sediments of the River Chenab, Pakistan

Polychlorinated biphenyl (PCBs, sum of 31 congeners) concentrations (ng g−1 dry weight) in sediments collected from the River Chenab during two years of monitoring ranged from 9.33 to 129.45 in winter and from 12.55 to 144.23 in summer. Levels of PCBs in sediments from the feeding tributaries were relatively greater. Sediments from the mainstream sites were dominated by tetra-CBs and penta-CBs, while hepta-CBs and octa-CBs were predominant in industrial and urban sites near tributaries. Factor analysis based on principal component analysis (FA/PCA) and correlation analysis suggested surface run-off from surrounding agricultural soils, direct discharge of industrial and municipal effluents without prior treatment into the aquatic ecosystem, and atmospheric deposition as the main sources of PCB contamination. Risk assessment was carried out by comparing the results with established sediment quality guidelines; PCB concentrations in 35% of sediments exceeded effect range low (ELR) and threshold effect level (TEL) values, however, none of sediments showed PCB concentrations greater than the effect range median (ERM) and probable effect level (PEL) with the exception of site S-20 (144.23 ng g−1, dry weight), which showed values higher than ERL and TEL.

Nitrogen, Phosphorus and Heavy Metals Contents and Releasing of Dahuangpu Wetland Sediment

Dahuangpu Wetland is the nature reserve of Tianjin City. The nitrogen, phosphorus and heavy metals contents and releasing of sediment in Dahuangpu Natural Wetland were studied in this paper. The results indicated that the contents of TN and TP in the wetland sediment were lower than the Lowest Effect Level (LEL) in the Guidelines for the Protection and Management of Aquatic Sediment Quality in Ontario, Canada (PSQGs), which means the sediment had no great eco-toxicity on dwelling organisms. Meanwhile the contents of heavy metals, namely Cr, As, Zn, Ni, Pb, Cu, Hg and Cd, in Dahuangpu Wetland sediment were lower than LEL of PSQGs and lower than primary standard of Environmental quality standard for soils (GB15618-1995). Moreover the influence of nitrogen, phosphorus and heavy metals releasing on wetland water qualities were trivial.

Effectiveness of lipid-lowering therapy with statins for secondary prevention of atherosclerosis – guidelines vs. reality

BackgroundThe aim of the study was to analyze the effectiveness of lipid-lowering therapy and therapeutic decisions made by physicians for patients not achieving LDL targets. Methods11,768 patients undergoing therapy with statins for secondary prevention of atherosclerosis participated in a two-visit survey. In subjects not achieving the LDL-target (< 100mg/dl), further therapeutic decisions made by physicians were recorded. ResultsInitially the LDL-target was achieved by 7.8% of patients on simvastatin and by 18.0% on atorvastatin, of which 20.8% were treated with at least a 40mg dose. The most common changes in therapy to improve effectiveness was substituting simvastatin for another statin (75.2%, usually atorvastatin), or increasing atorvastatin dosage (59.8%). Intensification of a low fat diet and weight reduction were more frequently recommended in treatment with atorvastatin than with simvastatin (59.8% vs. 55.9%, p<0.001). After enhanced therapy, the LDL-target was achieved by 27.8% on simvastatin and by 35.0% on atorvastatin (p<0.001). In those with LDL levels remaining above the target, substitution of simvastatin with atorvastatin (49.9%), or the increase of atorvastatin dose (41.4%) was recommended. As previously, life-style counseling was more frequent in patients on atorvastatin (66.1% vs. 45.7%; p<0.001). Conclusions1. The use of low dose statins and noncompliance with behavioral modification guidelines are responsible for the low levels of effectiveness found with lipid-lowering therapies. 2. Physicians prefer substitution of less effective statins over the increase of dose in patients not achieving LDL targets. 3. Life-style changes are under-prescribed by physicians and under-implemented by their patients.

Evaluation of Phosphorus Species in the Bed Sediments of an Atlantic Basin: Bioavailability and Relation with Surface Active Components of the Sediment

In this study, total phosphorus (P) concentrations and P fractions in the bed sediments of the Anllóns River (NW Spain) have been examined. The Lowest Effect Level of the Ontario Sediment Quality Guidelines was trespassed for total phosphorus (600 mg kg−1) at three out of the five sampling sites which, in addition, showed an average of 43% of bioavailable phosphate. The inorganic P fractions (loosely bound P, redox-sensitive P, metal oxide-bound P, carbonate and apatite P, and residual P) showed that inorganic P was mostly found as metal oxide bound P. The difference between total phosphorus and the sum of the inorganic P forms determined in these extracts is attributed to P associated to organic compounds being solubilized in some of the extractants, and represented in average 58% of total phosphorus. With the exception of loosely bound P, all the P fractions showed significant positive correlations with each other and with total phosphorus.

PENERAPAN NILAI – NILAI DASAR BUDAYA KERJA DAN PRINSIP-PRINSIP ORGANISASI BUDAYA KERJA PEMERINTAH DENGAN BAIK DAN BENAR

Organisational culture is important when faced with efforts to improve organizational performance and employees therein. Many people do not realize that a work keberhsilan rooted in those values originated from the customs, habits, religious and other rules into confidence and then became a habit in people's behavior in carrying out the work. The values that have become a habit is called culture. Because culture is associated with higher levels of quality work, then called the culture of work culture, both inside and outside the organization. In connection with the professional values espoused, the employee should be adaptive to changes in the value of organizational culture. Attitudes toward the organization's culture becomes more meaningful in accelerating or slowing down of this adaptive ability. If employees have individual values that conflict with organizational culture, this suggests a low level of effectiveness, and vice versa. In this case there should be clear how the fact that employee attitudes towards the prevailing organizational culture. If an employee shows a good attitude towards the organization's culture, it is expected to easily form an organization of social behavior.

Metal enrichment in beach sediments from Chennai Metropolis, SE coast of India

A survey on the Partially Extracted Trace Metals (PETMs) concentration (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd) in beach sediments is reported for the first time from 57 different locations in Chennai Metropolitan City of Southeast coast of India. The concentration of PETMs suggests that they are mainly concentrated with organic matter in the crowded part of the industrial regions in the beaches from the northern part rather than the tourist beaches in the southern part of the city. The comparison on enrichment of trace metals indicates higher values of Pb, Ni in the beaches than lowest effect level (LEL) and effects range low (ERL) than the tourist beaches.

Elemental composition of sediments in Lake Jinzai, Japan: Assessment of sources and pollution

Bottom sediments from Lake Jinzai in southwest Japan were analyzed to determine their chemical compositions and to assess the potential for ecological harm by comparison with sediment quality guidelines. The pollution status of lake sediments was evaluated by employing contamination factor (CF), pollution load index (PLI), and geoaccumulation index (I(geo)), focusing on a suite of elements in lakebed and core sediments. Elevated concentrations of As, Pb, Zn, Cu, TOC, N, and P were present in several layers of the upper core and other surface sediments. The elevated metal concentrations are likely related to the fine-grained nature of the sediments, reducing bottom conditions produced by abundant organic matter, and possibly minor non-point anthropogenic sources. Moreover, correlations between the concentrations of trace metals and organic carbon, nitrogen, phosphorus, and iron, suggest that these elements play a role in controlling abundances. Calculated CF, PLI, and I(geo) indicate that the sediments are strongly polluted with respect to As, moderately to strongly polluted with Zn, and moderately polluted with Pb and Cu. Metal concentrations exceed the New York State Department of Environmental Conservation (NYSDEC) lowest effect level and the Canadian Council of Ministers of the Environment (CCME) interim sediment quality guidelines that indicate moderate impact on aquatic organisms in the study area.

Differences in emotional intelligence between effective and ineffective leaders in the public sector: an empirical study

The literature supporting leadership as the most important factor related to organizational success or failure is burgeoning. To a large extent, this may explain why so much research focuses on factors influencing leadership effectiveness. A crucial aspect of leadership research is to determine why some individuals perform effectively in leadership roles while others demonstrate mediocre or low levels of effectiveness. Once measures of individual characteristics have been validated within a relevant context, they become useful sources of information for selecting, placing, and promoting people into leadership positions. The aim of this study was to determine if there are statistically significant differences in emotional intelligence between effective and ineffective leaders. The sample included 114 leaders at the middle management level in a public sector institution in South Africa. Each leader’s effectiveness was rated by themselves (self-rating), as well as by four subordinates, thus involving 570 participants. The EQ-i® was used as a measure of emotional intelligence, while Spangenberg and Theron’s Leadership Behaviour Inventory was used to determine leadership effectiveness. Multivariate analysis of variance indicated that the effective leaders scored significantly higher on the total emotional intelligence measure. They also scored significantly higher on two emotional intelligence composite scales (Interpersonal EQ and Stress Management EQ) and six sub-scales (Self-actualization, Empathy, Social Responsibility, Stress Tolerance, Problem-solving, and Optimism). Points for practitioners The relationship between emotional intelligence and leadership effectiveness seems to warrant organizational consideration of the possible inclusion of emotional intelligence, among other competencies, as a selection and promotion criterion for future leaders. Job analyses and the subsequent identification of job competencies can be used in order to determine, among others, the emotional intelligence requirements of specific leadership tasks, duties, and behaviours at different managerial levels within the organization. Based on such predetermined criteria, valid measures of emotional intelligence could be included as part of the selection and promotion process, along with other desirable individual attributes, such as verbal and numerical abilities, personality attributes, and specific managerial and leadership competencies required for effective leadership specifically within public sector institutions. Leadership development courses may also include programmes to develop emotional intelligence competencies. Potential candidates nominated to attend these courses could be equipped with a vital understanding of their own emotional functioning as well as an awareness of their influence on their followers. The continuous provision of feedback, mentoring, and modelling is also a key consideration in the development of emotional intelligence.

Evaluation of sediment quality guidelines derived using the screening-level concentration approach for application at uranium operations in Saskatchewan, Canada

Sediment quality guidelines (SQGs) can be derived using different approaches and are commonly used in environmental management, reclamation, and risk assessment. The screening-level concentration (SLC) approach has been used in Ontario, Canada, to derive lowest effect levels (LELs) and severe effect levels for use as SQGs. This approach was adopted by the Canadian Nuclear Safety Commission (CNSC) to set guidelines for metals (As, Cr, Cu, Pb, Mo, Ni, Se, U, and V) and radionuclides (Ra-226, Pb-210, and Po-210) in sediment at northern Saskatchewan uranium mining and milling operations. The SLC approach is based on total metal and radionuclide concentrations in sediment, and corresponding benthic community composition data for a specific sampling site. In this study, sediment chemistry (total metals and radionuclides) and benthic community data from northern Saskatchewan uranium operations were compiled and examined. Results indicate that the CNSC-derived SQGs had limited relationships to observed effects, or lack thereof, on benthic invertebrate communities near uranium operations in Saskatchewan. The LELs were found to correctly align with effects at 95% of the sites that had effects, on a general basis, but on an element-specific basis many of the elements had concentrations at effect sites below their LELs. Furthermore, concentrations of the evaluated elements exceeded at least one LEL at 60% of the no-effect sites. The high number of exceedences of LELs at reference and no-effect sites (false-positives) calls to question the appropriateness of the CNSC-derived SQGs. It is suggested that alternatives to the SLC approach be explored.

Toxicity of uranium, molybdenum, nickel, and arsenic to Hyalella azteca and Chironomus dilutus in water-only and spiked-sediment toxicity tests

A series of laboratory spiked-sediment toxicity tests with the amphipod Hyalella azteca and the midge Chironomus dilutus were undertaken to determine acute and chronic toxicity thresholds for uranium (U), molybdenum (Mo), nickel (Ni), and arsenic (As) based on both whole-sediment (total) and pore water exposure concentrations. Water-only toxicity data were also generated from separate experiments to determine the toxicities of these metals/metalloids under our test conditions and to help evaluate the hypothesis that pore water metal concentrations are better correlated with sediment toxicity to benthic organisms than whole-sediment metal concentrations. The relative toxicity of the four elements tested differed depending on which test species was used and whether whole-sediment or pore water metal concentrations were correlated with effects. Based on measured whole-sediment concentrations, Ni and As were the two most acutely toxic elements to H. azteca with 10-d LC50s of 521 and 532 mg/kg d.w., respectively. Measured pore water concentrations indicated that U and Ni were the two most acutely toxic elements, with 10-d LC50s to H. azteca of 2.15 and 2.05 mg/L, respectively. Based on pore water metal concentrations, the no-observed-effect concentrations (NOECs) for growth were ( H. azteca and C. dilutus, respectively) 0.67 and 0.21 mg/L for U, <0.37 and 0.60 mg/L for Ni, and 16.43 and <0.42 mg/L for As. Pore-water lowest-observed-effect concentrations (LOECs) for growth were ( H. azteca and C. dilutus, respectively) 2.99 and 0.48 mg/L for U, 0.37 and 2.33 mg/L for Ni, and 58.99 and 0.42 mg/L for As. For U and Ni, results from 96-h water-only acute toxicity tests correlated well with pore water metal concentrations in acutely toxic metal-spiked sediment. This was not true for As where metalloid concentrations in overlying water (diffusion from sediment) may have contributed to toxicity. The lowest whole-sediment LOEC reported here for As was 6.6- and 4-fold higher than the Canadian Council of Ministers of the Environment interim sediment quality guideline and the Canadian Nuclear Safety Commission (CNSC) lowest effect level (LEL), respectively. The lowest whole-sediment LOECs reported here for Ni, U and Mo were 4-, 17.5-, and >260-fold higher, respectively, than the CNSC LELs for these metals/metalloids. Data on pore water metal concentrations in toxic sediment would be a useful addition to future Guidelines documents.

A modeling assessment of contaminant fate in the Bay of Quinte, Lake Ontario: Part 1. Metals

A mass balance model of contaminant fate-transport was used to assess the fate of four metals: As, Cd, Cu and Zn, in the Bay of Quinte for hydrologic conditions and loadings in 2000. Results were compared with previous model results of 1988. The model was based on the QWASI (Quantitative Water Air Sediment Interaction) approach and the fugacity/aquivalence concept. The Bay was divided into five geographic segments based on hydrodynamics and chemical loadings. The model identified tributaries and Lake Ontario as the major sources of metal loadings to the Upper and Lower Bays, respectively. Metal concentrations in water decreased by 40–75% in the tributaries between May 1988 and 2000, which resulted in decreased metal concentrations that were, in 2000, all below the Provincial Water Quality Objectives. Measured sediment concentrations exceeded the Lowest Effect Levels (LEL) for all metals at many sites in the Upper and Lower Bays. Using 2000 metal loadings from tributaries and Lake Ontario, the model predicted that sediment concentrations will meet or come within 20% of LELs for all metals in segment 1, As in segments 2 and 3, and Zn in segment 3 within 40 years. Although the model predicted that sediment concentrations would decline to the LEL for all segments within 26 (Zn) to 54 (Cu) years, evidence suggests that benthos are now not impaired by ambient sediment concentrations (excluding “hot spots”). Reducing sediment concentrations faster is expected to be very difficult because their loadings originate from diffuse sources in the watersheds of tributaries and Lake Ontario.

Effectiveness of retail joint promotions under different channel structures

We investigate the effects of horizontal joint promotions (HJP) initiated by competing retailers on the supply chain’s strategies and profits and address the following questions; can HJP be profitable for competing retailers and for the whole channel? Under what market conditions and for which channel structures? We develop a game theoretic model to address these issues. We study market conditions conducive for profitable joint retail promotions under different channel structures; when both retailers are decentralized, centralized and when one is centralized and its competitor is decentralized. We find that for low levels of promotional effectiveness, HJP improves each channel member’s profits through demand expansion and higher margins under all channel structures. However, a highly effective HJP can only be initiated by decentralized retailers. In particular, for low levels of cross price effects, demand decreases with HJP and so do the retailers’ profits since the latter’s gain in margins are not sufficient to neither pay for the lost unit sales nor cover the promotion’s cost. However, for higher levels of cross price effects, HJP boosts demand and although it might still lead to lower retailers’ profits, it will increase the manufacturers’ and the total channel’s profits. Manufacturers supplying products to decentralized retailers might lose from HJP. However, when that is the case, retailers do not have an incentive to invest in such a promotion. On the opposite, when manufacturers benefit from HJP, retailers could, in most cases, implement the HJP promotion even if they lose profits because the total channel profits are improved.

Moderators of weight gain in the early stages of outpatient cognitive behavioral therapy for adults with anorexia nervosa

Treatments for anorexia nervosa have relatively low levels of effectiveness. This prospective study examines the impact of patients' characteristics on their early responses to cognitive behavioral therapy (CBT) for anorexia nervosa. Patients' eating attitudes, body mass index, and comorbid characteristics at the outset of treatment were used to predict drop-out and changes in weight across the first 10 sessions of CBT. Forty anorexic patients (28 full syndrome and 12 atypical cases--body mass index range = 12.8-18.4) entered CBT for anorexia nervosa. Early drop-outs (N = 6) had relatively low levels of anxiety at the beginning of therapy, but there were no other moderators. Weight gain was slower in the 6th to 10th sessions among patients with relatively unhealthy eating attitudes (restraint and shape concerns). Higher levels of anxiety at the start of treatment were associated with poorer weight gain across these first 10 sessions. Early anxiety levels should be attended to closely in CBT for anorexia nervosa, with low levels indicating a high risk of drop-out and a greater need for engagement and motivational work, and high levels, indicating that clinicians should work explicitly with the patient on anxiety reduction techniques in order to enhance their level of early weight gain.

Assessment of heavy metal pollution in wetland soils from the young and old reclaimed regions in the Pearl River Estuary, South China

Soils were sampled in three types of wetlands from the young (A) and old (B) reclaimed regions of the Pearl River Estuary. They were analyzed for total concentrations of heavy metals to investigate their distributions and pollution levels in both regions. Results showed that most heavy metals in ditch and riparian wetlands did not significantly differ from those in reclaimed wetlands in A region, while significantly lower for Cd, Cu, Pb, and Zn in reclaimed wetlands in B region, suggesting higher effects of long-term reclamation. Iron, Cr and Cu were identified as metal pollutants of primary concern and had higher contributions to the total toxic units compared to other metals. Almost all metals exceeded their lowest effect levels and Fe and Cr even exceeded the severe effect levels. Multivariate analysis shows that Fe and Mn are controlled by parent rocks and other metals mainly originate from anthropogenic source.

Metal and oxalate contamination in a suburban watershed in the greater Toronto area: The benefits of combining acid leach and selective extraction procedures

Environmentally available concentrations of Fe, Mn, Zn, Cu, Pb, Cr and Ni in soils and sediments from a small suburban catchment, obtained using an acid leach procedure, are compared to the Ontario Ministry of the Environment lowest effect level (LEL) and severe effect levels (SEL) and to Provincial sediment quality guidelines (PSQG’s). These data are then compared to the bioavailability, potential bioavailability and non-bioavailability of the same metals, plus oxalate concentration, identified using a selective extraction procedure. This combination of techniques enhanced analytical interpretation with respect to metal mobility and potential metal contamination. Selective extraction highlighted the presence of oxalate as a potential contaminant, especially in poorly drained valley floor deposits (33,633 mg kg−1 and 26,284 mg kg−1) and lakeshore sediments (27,095 mg kg−1 and 13,729 mg kg−1). These levels are considerably in excess of those previously documented in a similar study from Rio de Janeiro, where contamination of urban sediment by sewage is a recognised environmental problem, and could possibly be used both as an indicator of similar contamination and the identification of those areas that warrant further investigation.