Water Quality Guidelines Research Articles

Tracking down pharmaceutical pollution in surface waters of the St. Lawrence River and its major tributaries

A reconnaissance survey was undertaken to evaluate the occurrence and risks of 27 pharmaceuticals and metabolites in the St. Lawrence watershed. Surface water samples were collected over a five-year period (2017–2021) along a 700-km reach of the St. Lawrence River as well as 55 tributary rivers (overall N = 406 samples). Additionally, depth water samples and sediments were collected near a major wastewater effluent. Caffeine, diclofenac, and venlafaxine were the most recurrent substances (detection rates >80 %), and extremely high levels were found near a municipal effluent (e.g., ibuprofen (860 ng/L), hydroxyibuprofen (1800 ng/L) and caffeine (7200 ng/L)). Geographical mapping and statistical analyses indicated that the St. Lawrence River water mass after the Montreal City effluent was significantly more contaminated than the other water masses, and that contamination could extend up to 70 km further downstream. This phenomenon was repeatedly observed over the five years of sampling, confirming that this is not a random trend. A slight increase in contamination was also observed near Quebec City, but concentrations rapidly declined in the estuarine transition zone. Tributaries with the highest pharmaceutical levels (ΣPharmas ∼400–900 ng/L) included the Mascouche, Saint-Régis, and Bertrand rivers, all located in the densely populated Greater Montreal area. When flowrate was factored in, the top five tributaries in terms of mass load (ΣPharmas ∼200–2000 kg/year) were the Des Prairies, Saint-François, Richelieu, Ottawa, and Yamaska rivers. All samples met the Canadian Water Quality Guideline for carbamazepine. Despite the large dilution effect of the St. Lawrence River, a risk quotient approach based on freshwater PNEC values suggested that four compounds (caffeine, carbamazepine, diclofenac, and ibuprofen) could present intermediate to high risks for aquatic organisms in terms of chronic exposure.

Evaluating land use impacts on water quality: perspectives for watershed management

Human activities threaten the integrity of watersheds. We aimed to investigate the impact of land use on water quality, adopting a multiscale approach. We collected water samples from twelve streams in Southern Brazil and conducted limnological analyses (physical, chemical, and biological) during the dry season. We used the water quality index based on the quality standards of Canada and Brazil. Land use percentage was measured in two groups (local scale and network scale). Environmental variables were summarized through Principal Component Analysis, and we organized them into Linear Models, integrating the percentage of land use classes and terrain slope in the Multifit formula. Statistical analyses were performed using the R software. Results indicated contamination by lead, chromium, copper, nitrogen, and Escherichia coli in water samples. The Canadian Water Quality Guidelines for the Protection of Aquatic Life resulted in an index ranging from 23.3 to 47.3, compared to the Brazilian Resolution No. 357/2005 for Class 2, which had an index ranging from 47.5 to 100. This disparity is attributed to the more rigorous and sensitive monitoring approach adopted by the Canadian guidelines. Riparian forests which are up to 50 m wide are associated with improved water quality. Agricultural and urban activities were the main contributors to water quality degradation in an area extending up to 1000 m from the watershed. We emphasize the importance of a multiscale approach in watershed management and public policies, considering not only riparian forest preservation, but also human activities throughout the watershed. It is crucial to prioritize science-based environmental public policies and strengthen enforcement to prevent increasingly pronounced environmental collapses. We have identified the urgency to reformulate CONAMA Resolution No. 357/2005 with a more conservationist and ecosystem-oriented approach, as well as to propose modifications to the Brazilian Forest Code, particularly regarding the buffer zones of permanent preservation areas. Thus, this study can provide insights, such as incorporating the “effect scale,” to enhance water resource management in landscapes heavily influenced by human action, contributing to the advancement of future research in freshwater ecosystems.

Occurrence, Ecological and Health Risks of Organic Pollution of the Waters from a Tropical Lake System

The monitoring of the organic pollution level and the ecological and health risks of the waters from the Déganobo lake system were the subject of this study. In its implementation, the water samples were collected monthly in this aquatic ecosystem over a year (from August 2021 to July 2022). The organic pollution level of these waters was assessed using their Chemical Oxygen Demand, determined in accordance with NF T 90-101 standard. The ecological and health risks were assessed based on the SEQ-Eau V2 water quality guidelines. Their COD seasonal mean values were between 220,000±51,872 and 361,333±48,273 mg/L O2. So, their organic pollution was relatively very significant, with the corollary of the zero of its seasonal transparencies and of its seasonal dissolved oxygen contents. The seasonal dynamics of organic matter in these waters was essentially linked to the hydroclimate (rainfall and ambient temperature) on the watershed of this lake system. The low meteorite waters inputs in dry seasons favoured the increase of their COD by the important punctual wastes inputs of various origins (domestic, agricultural, industrial, hospital, etc.); in opposite of the important meteorite waters inputs in rainy seasons causing their renewal. The consequences of their important COD values are severe ecological and health risks, as highlighted by SEQ-Eau V2 water quality guidelines. So, this lake system is under the strong anthropogenic pressures. This study could serve as complementary information on its pollution level and contribute to decision-making for its rehabilitation, its protection within the framework of its sustainable development.

Improving toxicity prediction of metal-contaminated sediments by incorporating sediment properties

For the purpose of sediment quality assessment, the prediction of toxicity risk-levels for aquatic organisms based on simple environmental measurements is desirable. One commonly used approach is the comparison of total contaminant concentrations with corresponding water and sediment quality guideline values, serving as a Line of Evidence (LoE) based on chemistry-toxicity effects relationships. However, the accuracy of toxicity predictions can be improved by considering the factors that modify contaminant bioavailability. In this study we used paired chemistry-ecotoxicity data sets for sediments to evaluate the improvement in toxicity risk predictions using bioavailability-modified guidelines. The sediments were predominantly contaminated with metals, and measurements of sediment particle size, total organic carbon (TOC) and acid volatile sulfide (AVS) were used to modify hazard quotients (HQ). To further assess the predictive efficacy of the bioavailability-modified guideline models, sediments with differing contamination levels were tested for toxicity to a benthic amphipod's reproduction. To account for differences between laboratory exposure and field exposure scenarios, where the latter creates greater dilution, both static-renewal and flow-through test procedures were employed, and flow-through resulted in lower dissolved metal concentrations in the overlying waters. We also investigated how lower AVS concentration by oxidation modified the toxicity. This study reaffirmed that consideration of factors that influence contaminant bioavailability improves toxicity risk predictions, however the improvements may be modest. The sediment particle size data had the greatest influence on the modified HQ, indicating that higher percentage of fine particle size (<63 μm) contributed most to a lower predicted toxicity. The comparison of the static-renewal and flow-through test results continue to raise important questions about the relevance of static or static-renewal toxicity test results for risk assessment decisions, as both these test designs may cause unrealistically high contributions of dissolved metals in overlying waters to toxicity. Overall, this study underscores the value of incorporating outcomes from simple and routine sediment analysis (e.g., particle size, TOC, and consideration of AVS) to enhance the predictive efficacy of toxicity risk assessments in the context of sediment quality risk assessment.

Recommended updates to the USEPA Framework for Metals Risk Assessment: Aquatic ecosystems.

In 2007, the USEPA issued its "Framework for Metals Risk Assessment." The framework provides technical guidance to risk assessors and regulators when performing human health and environmental risk assessments of metals. This article focuses on advances in the science including assessing bioavailability in aquatic ecosystems, short- and long-term fate of metals in aquatic ecosystems, and advances in risk assessment of metals in sediments. Notable advances have occurred in the development of bioavailability models for assessing toxicity as a function of water chemistry in freshwater ecosystems. The biotic ligand model (BLM), the multiple linear regression model, and multimetal BLM now exist for most of the common mono- and divalent metals. Species sensitivity distributions for many metals exist, making it possible for many jurisdictions to develop or update their water quality criteria or guidelines. The understanding of the fate of metals in the environment has undergone significant scrutiny over the past 20 years. Transport and toxicity models have evolved including the Unit World Model allowing for estimation of concentrations of metals in various compartments as a function of loading and time. There has been significant focus on the transformation of metals in sediments into forms that are less bioavailable and on understanding conditions that result in resolubilization or redistribution of metals in and from sediments. Methods for spiking sediments have advanced such that the resulting chemistry in the laboratory mimics that in natural systems. Sediment bioavailability models are emerging including models that allow for prediction of toxicity in sediments for copper and nickel. Biodynamic models have been developed for several organisms and many metals. The models allow for estimates of transport of metals from sediments to organisms via their diet as well as their water exposure. All these advances expand the tool set available to risk assessors. Integr Environ Assess Manag 2024;20:924-951. © 2023 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Spatial distribution of drinking and irrigation water quality in different climatic zones of Baluchistan, Pakistan.

Baluchistan's water profile was developed by dividing it into seven zones (Northern Highlands-NH, Southern Highlands-SH, Quetta Valley-QV, Desert-D, Sibbi Plains-SP, Coastal Lasbella-CL, Coastal Gwadar-CG) based on geography, water availability, and climate of the area. A total of 106 water samples were collected from karaiz, spring water, and tube wells. Spatial distribution of EC, TDS, TH, SO42-, Cl-, Na+, and K+ showed an increasing trend in concentration from the highlands towards the desert and coastal zones. For anion, HCO3- is predominant in NH, SH, and QV, Cl- in D, CL, and CG and only SO42- in SP, whereas the cationic trend in overall zones is Na+>Ca2+>Mg2+>K+. In the NH, SH, QV, and SP zones, the physicochemical parameters met the drinking water quality guidelines; however, D, CL, and CG exceeded in almost all quality parameters. Furthermore, the drinking water quality index (WQI) shows excellent to good water quality in NH, SH, QV, and D zones, while CL and CG fall in poor to unsuitable water classes. In terms of hydrogeochemical facies, maximum water samples from NH fall in Ca-Mg-HCO3, and SH, QV, and SP in Ca-Mg-Cl type, where major ion chemistry is controlled by rock-weathering, while D, CL, and CG fall in the NaCl type, where evaporation is dominant. Similarly, irrigation water quality parameters (EC, SAR, RSC, Na%, MH%, PI, SSP, and KR) reveal that NH, SH, QV, and SP have suitable water for irrigation, and D, CL, and CG require proper treatment. Additionally, USSL and Wilcox's diagrams indicated that NH, SH, QV, and SP have "excellent to permissible"; however, D, CL, and CG have "permissible to unsuitable" class water, requiring special management practices. Consequently, appropriate control measures and targetedwater purification programmes should be implemented to protect the publichealth and sustainability of water resources inBaluchistan.

Protecting the invisible: Establishing guideline values for copper toxicity to marine microbiomes

Understanding the rapid responses of marine microbiomes to environmental disturbances is paramount for supporting early assessments of harm to high-value ecosystems, such as coral reefs. Yet, management guidelines aimed at protecting aquatic life from environmental pollution remain exclusively defined for organisms at higher trophic levels. In this study, 16S rRNA gene amplicon sequencing was applied in conjunction with propidium monoazide for cell-viability assessment as a sensitive tool to determine taxon- and community-level changes in a seawater microbial community under copper (Cu) exposure. Bayesian model averaging was used to establish concentration-response relationships to evaluate the effects of copper on microbial composition, diversity, and richness for the purpose of estimating microbiome Hazard Concentration (mHCx) values. Predicted mHC5 values at which a 5 % change in microbial composition, diversity, and richness occurred were 1.05, 0.72, and 0.38 μg Cu L−1, respectively. Threshold indicator taxa analysis was applied across the copper concentrations to identify taxon-specific change points for decreasing taxa. These change points were then used to generate a Prokaryotic Sensitivity Distribution (PSD), from which mHCxdec values were derived for copper, suitable for the protection of 99, 95, 90, and 80 % of the marine microbiome. The mHC5dec guideline value of 0.61 μg Cu L−1, protective of 95 % of the marine microbial community, was lower than the equivalent Australian water quality guideline value based on eukaryotic organisms at higher trophic levels. This suggests that marine microbial communities might be more vulnerable, highlighting potential insufficiencies in their protection against copper pollution. The mHCx values proposed here provide approaches to quantitatively assess the effects of contaminants on microbial communities towards the inclusion of prokaryotes in future water quality guidelines.

Assessment of spring water quality of Khandbari Municipality in Sankhuwasabha District, Eastern Nepal.

The study was carried out in the Khandbari Municipality, Sankhuwasabha District, Eastern Nepal to document the spring location and assess the water quality of the spring water for drinking and irrigation purposes. A total of 85 springs were mapped, which are located from 274 to 2176 m in altitude. Spring water samples were collected from 33 springs in the pre-monsoon (November, 2021) and 31 springs in the post-monsoon (March, 2022). Correlation matrices, t-test, principal component analysis (PCA), Piper diagram, Gibbs diagram, water quality index (WQI), United States Salinity Laboratory (USSL) diagram, and Wilcox diagram were applied for evaluating the spring water. All the physicochemical parameters were within the Nepalese National Drinking Water Quality Standard (NDWQS) and drinking water quality guidelines of the World Health Organization (WHO) except for pH in the pre-monsoon and iron in the post-monsoon season. The main contributors to the groundwater are Na+, Ca2+, Cl-, total dissolved solids (TDS), and total hardness, which exhibit significant correlations with electrical conductivity (EC) similar to TDS, suggesting their common source of origin. Based on the WQI, spring water is excellent in the post-monsoon and excellent and good in the pre-monsoon season. Furthermore, the spring water is excellent for irrigation purposes except for thepercent sodium in the post-monsoon and the magnesium ratio in the pre-monsoon season. Gibbs diagram illustrates that spring water is mainly governed by rock and precipitation dominance in some springs. The PCA indicates that anthropogenic activities (mixing of human waste and agricultural run-off in the spring water) are the main causes of contamination. Piper trilinear diagram demonstrates carbonate dissolution and silicate weathering as major processes for controlling the spring water chemistry. The study reveals that 62.5% of spring water was contaminated with microbes. For benthic macroinvertebrates, 18 springs were sampled, where nine orders and 17 families were recorded in the pre-monsoon and six orders and ten families in the post-monsoon season. The main influencing variables for macroinvertebrate assemblages are elevation, discharge, NO3-, and NH3.

The effects of winter cold acclimation on acute and chronic cadmium bioaccumulation and toxicity in the banded killifish (Fundulus diaphanus)

Temperate freshwater fishes can experience large seasonal temperature fluctuations that could affect their exposure and sensitivity to trace metals. Yet, temperature effects are overlooked in ecotoxicology studies, especially for cold temperatures typical of the winter. In the present study, the effects of long-term cold acclimation on Cd bioaccumulation and toxicity were investigated in a freshwater fish, the banded killifish (Fundulus diaphanus). Killifish were acclimated to 14 °C or gradually cooled (2 °C/week) to 4 °C and cold acclimated for 6 weeks. Then, both acclimation groups were exposed to environmentally realistic waterborne Cd concentrations (0, 0.5 or 5 µg Cd L−1) for a further 28 d at their respective acclimation temperatures. Tissue metal bioaccumulation, fish survival, condition, and markers of oxidative and ionoregulation stress, were measured after 0, 2, 5 and 28 days of Cd exposure. Cadmium tissue accumulation increased over the exposure duration and was typically lower in cold-acclimated fish. In agreement with this lower bioaccumulation, fewer Cd toxic effects were observed in cold-acclimated fish. There was little evidence of a difference in intrinsic Cd sensitivity between 4 °C- and 14 °C-acclimated fish, as Cd toxicity appeared to closely follow Cd bioaccumulation. Our study suggests that current environmental water quality guidelines would be protective in the winter for the abundant and ecologically-important banded killifish.

Relationships between reference site quality and baetid mayfly assemblages in mountainous streams of the Luvuvhu catchment, South Africa

With water quality deteriorating rapidly at a global scale, river sections suited to serve as reference sites are being increasingly lost. It thus becomes critical to develop rapid methods to confirm that previously monitored sites continue meet the requirements of reliable reference sites. In the absence of pristine sites, 9 near-natural sites, as defined by the Kleynhans (1996) classification, were used as reference sites for the Luvuvhu River catchment to compare the quality of physico-chemical factors against a biological metric. Baetid mayfly community structure at a site was chosen as an index of water quality, since this family is common in all types of freshwaters, highly diverse and adapted to unpolluted running water. Baetid larvae were sampled monthly from stones-in-current biotopes across 9 sites for over 1 year, between December 2016 and January 2018. A Spearman’s correlation test was used to evaluate the relationship between physico-chemical factors and identify redundant variables. Water quality standards were measured against the national water quality guidelines for aquatic ecosystems. We used a generalized linear model to determine the effect of physico-chemical variables on baetid species, and canonical correspondence analysis to show the relationships between baetid species, sites, and physico-chemical variables. A total of 3 039 individuals belonging to 12 mayfly species were recorded. Our findings indicated that while the physico-chemical factors were highly variable, they were within favourable ranges to reflect reference site conditions. While water temperature was the most important driver of baetid community structure in general, as it negatively affected their abundances, a subset of species (Pseudoponnota sp., Pseudocloeon sp., Acanthiops varius and Demoulinia crassi) showed clear responses to changes in TDS and stream width. We conclude that specific baetid species show good potential as biological indicators of reference sites and chronic water temperature stress, making assessment of reference sites easier.

Assessment of Borehole Water Quality in Usmanu Danfodiyo University Sokoto (Permanent Site), Nigeria

It is acknowledged that access to high-quality water is crucial for any significant human development. Ten boreholes were used in obtaining the water sample. The samples were analyzed using the American Public Health Association (APHA) suggested procedures. The test parameters were compared to the chemical drinking water quality guideline established by the World Health Organisation. In a situation where the value is not provided, we relied on other pieces of literature. The research shows that the alkalinity, iron (Fe+), calcium (Ca2+), magnesium (Mg+), nitrate (NO3-), pH, conductivity, phosphate (PO43-), and total hardness (CaCO3) are all in line with the guidelines permissible limit which means are within the no-problem zone limits for health. While copper (Cu2+) was found to be within the permissible limit 2 mg/L in all the samples but BH1 (Junior Staff Quarters) 3mg/L which has health problems such as digestive disturbances, problems with the central nervous system, mucosal irritability, Wilson's illnesses, and liver and kidney damage.

Novel insight into ammonium, phosphate, and iron(II) dynamics in the sediment porewater of a constructed wetland under artificial aeration through the diffusive equilibrium in thin films technique

The analysis of porewater concentrations in constructed wetland sediments could help to understand biogeochemical processes, the sources and sinks of nutrients, and their effect on overlying water quality. In this study, we measured high-resolution porewater concentration profiles of ammonium (NH4+-N), nitrate (NO3N), phosphate (PO43--P), and ferrous iron (Fe(II)) in-situ in the Laratinga constructed wetland in Mount Barker (South Australia) using diffusive equilibration in thin films (DET) techniques. Measurements were taken under light and dark conditions, and non-aerated and aerated conditions to determine the effect on sediment porewater nutrient concentrations. Baseline surface water nutrient concentrations (NH4+-N > 36 mg L-1, PO43--P > 0.43 mg L-1) greatly exceeded water quality guideline criteria. Aeration of the water column alleviated night-time hypoxic conditions (i.e. dissolved oxygen increased from a minimum of 0.7 mg L-1 to a minimum of 4 mg L-1), and increased the redox potential in the sediment. Significant differences were present for NH4+-N, PO43--P, and Fe(II) concentrations with depth in the sediment. Ammonium concentrations in the sediment reduced under aerated conditions, presumably due to enhanced nitrification. However it was observed that PO43--P and Fe(II) concentrations increased significantly with aeration, especially under dark conditions, and were strongly correlated (R2>0.8). This was not what was hypothesised and points to complex interactions between Fe and P in the sediment. Nitrate concentrations in the sediment were below the detection limit (<0.9 mg L-1) which suggests limited nitrification-denitrification is occurring. Overall the results suggest that DET techniques are useful tools for quantifying porewater concentrations of nutrients in constructed wetlands under various environmental conditions.

Quantitative microbial risk assessment of the gastrointestinal risks to swimmers at Southeast Asian urban beaches using site-specific and combined autochthonous and fecal bacteria exposure data

Recreational exposure to microbial pollution at urban beaches poses a health risk to beachgoers. The accurate quantification of such risks is crucial in managing beaches effectively and establishing warning guidelines. In this study, we employed a quantitative microbial risk assessment (QMRA) framework to assess marine water quality and estimate the risks associated with Vibrio parahaemolyticus, an autochthonous pathogen that causes gastrointestinal illnesses, and enterococci, a traditional fecal bacteria indicator. The microbial contamination levels of V. parahaemolyticus and enterococci were determined from 48 water samples collected at two beaches in Thailand during dry and wet seasons. The accidentally ingested water volumes were obtained through a survey involving 438 respondents. The probability of illness (Pill) was estimated using dose–response models and Monte Carlo simulation. The results revealed that enterococci posed a higher risk of illness than V. parahaemolyticus at all seven study sites. The median combined gastrointestinal (GI) risk from both bacteria at all sites met the US EPA risk benchmark of 0.036 and the 0.05 benchmark set by the WHO, but the 95th percentile risk data at all sites exceeded the benchmarks. This emphasizes the need for the continuous monitoring and management of microbial pollution at these sites. The site-specific exposure data showed higher estimated risks with increased variations compared to the WHO-referenced values, which highlights the significance of locally measured microbial concentrations and survey exposure data to avoid underestimation. Estimating the risks from recreational exposure to waterborne bacteria can inform beach management policies aimed at reducing public health risks to swimmers. The study findings improve the understanding of the risks associated with water recreation activities at Southeast Asian beaches and offer valuable insights for the development of water quality guidelines, which are crucial for the sustainable development of the blue economy.

A comparative analysis of water quality guidelines for fluoride in Canada and Spain

Although anthropogenic fluoride (F−) pollution is a serious worldwide environmental problem, only a few countries have currently established national water quality criteria for the protection of freshwater biota. Since Canada is a global leader in biodiversity conservation that exhibits restrictive water quality benchmarks, I carry out a comparative analysis of water quality guidelines for fluoride in Canada and Spain. The Canadian water quality benchmark of 0.12 mg F−/l (maximum allowable concentration) prevents Canada’s fresh waters from significant adverse events of fluoride pollution, thereby protecting sensitive native aquatic invertebrates and adult-migrating Pacific salmon. By contrast, the Spanish water quality benchmark of 1.7 mg F−/l (annual mean concentration) allows not only continuous levels of fluoride pollution more than six times higher than natural fluoride concentrations in the fresh waters of mainland Spain, but also much higher discontinuous levels of fluoride pollution (&gt; 15 mg F−/l). This unacceptable scenario is contrary to the current environmental goal of “zero pollution” in the European Union. In view of the existing toxicological data, a Spanish water quality guideline of 0.15−0.3 mg F−/l (maximum allowable concentration) seems much more reasonable. The recommended water quality guideline for fluoride would much better protect sensitive native fish and invertebrate species, and prevent significant bioaccumulation of fluoride in tolerant freshwater organisms.

Long-Term Impact of Historical Mining on Water Quality at Mount Lyell, Western Tasmania, Australia

During the twentieth century, inadequate management of mine waste at the Mount Lyell Copper Mine affected the ecology of the Queen–King Rivers and Macquarie Harbour, western Tasmania, Australia. Over the past two decades, the water quality of the river system has been measured semi-annually to investigate the long-term hydrochemical and environmental impacts caused by these historical mine practices and the waste associated with the Mount Lyell mine to the Queen–King Rivers. At sample sites below the confluence of Haulage Creek, the water pH was below pH 3.5, remaining below pH 5 across all sites to Macquarie Harbour. Local baseline rivers ranged from pH 4.0 to 8.4. Elemental concentrations of dissolved metals in water samples downstream of Haulage Creek were above the Australian and New Zealand Environment and Conservation Council (ANZECC) water quality guidelines. Copper, Fe, and Zn were not attenuated along the length of the river, with concentrations remaining elevated to the King River Delta. Mineralogical analyses demonstrated secondary minerals in sediments at Haulage Creek and pyrite concentrated at the King River Delta. Static tests on mining-affected sediments indicated risk of AMD and metal(loid) leaching in the river system. Since 2016, after flooding of the Prince Lyell mine, dissolved metal levels in the Queen–King Rivers have decreased; however, concentrations remain above guidelines. Almost three decades after legacy mine waste disposal ended, it still poses a long-term risk to the downstream environment, implying that without effective management of these historical mine wastes, the Queen–King Rivers will continue to be severely impacted.Graphical

Acute and chronic toxicity of manganese to tropical adult coral (Acropora millepora) to support the derivation of marine manganese water quality guideline values

Adult corals are among the most sensitive marine organisms to dissolved manganese and experience tissue sloughing without bleaching (i.e., no loss of Symbiodinium spp.) but there are no chronic toxicity data for this sensitive endpoint. We exposed adult Acropora millepora to manganese in 2-d acute and 14-d chronic experiments using tissue sloughing as the toxicity endpoint. The acute tissue sloughing median effect concentration (EC50) was 2560 μg Mn/L. There was no chronic toxicity to A. millepora at concentrations up to and including the highest concentration of 1090 μg Mn/L i.e., the chronic no observed effect concentration (NOEC). A coral-specific acute-to-chronic ratio (ACR) (EC50/NOEC) of 2.3 was derived. These data were combined with chronic toxicity data for other marine organisms in a species sensitivity distribution (SSD). Marine manganese guidelines were 190, 300, 390 and 570 μg Mn/L to provide long-term protection of 99, 95, 90, and 80 % of marine species, respectively.

Implementing approaches to account for metal bioavailability in freshwaters: Current status and future directions.

Implementing approaches to account for metal bioavailability in freshwaters: Current status and future directions.

Water Quality Assessment of Santa Cruz River in 2011 and 2022 in the Vicinity of Liliw and Nagcarlan, Laguna, Philippines

Santa Cruz River has significant importance for the economic development of the Philippines and the inhabitants depending on this river for various purposes. It is also one of the 21 major tributary rivers of Laguna de Bay that has a substantial contribution of 15% to the total lake water. This study aims to determine water quality in part of Liliw-Nagcarlan, Laguna of the Santa Cruz River in 2011 and 2022 and to identify the sub-watershed experiencing changes in water quality. There are three sites used for sampling (Talahibing, Bangkuro, and Lapad rivers). Physicochemical and hydrometry were measured in situ. Temperature, pH, and conductivity are within the normal limits. However, dissolved oxygen was generally above the normal limits based on the DENR Water Quality Guidelines. The results showed that the water quality in 2011 and 2022 was projected to change. The number of settlements, recreational activities, and nature park areas increased while the riparian vegetation decreased. The change in land cover will affect the water quality. The result of the assessment for the temperature and conductivity in 2022 was higher compared to 2011. The increase that occurred was influenced by the reduced dissolved oxygen and the pH level, which can cause fish kills and create significant harm to ecosystems. Flowrate was higher from 2022 compared to 2011, since the temperature increased, and the dissolved oxygen levels decreased from this study. Important correlations between the different parameters and the year of the study were proved.

Reference conditions and threshold values for nitrate-nitrogen in New Zealand groundwaters

ABSTRACT Management of groundwater quality is assisted by an understanding of reference conditions, which describe the concentration ranges expected for key substances in the absence of human impact. This study evaluates reference conditions for NO3–N in New Zealand groundwater based on three complementary methods: hierarchical cluster analysis, relationships to groundwater age, and regression against a measure of land-use impact. The three methods result in very similar national-scale estimates of reference conditions for NO3–N concentration in oxic, minimally impacted groundwater, with the 80th, 90th and 95th percentiles found to be 1.65 ± 0.12, 1.97 ± 0.14 and 2.32 ± 0.14 mg/l, respectively (weighted average ± 95% confidence level), in good general agreement with previous studies from New Zealand and overseas. Anoxic groundwaters were treated separately for definition of reference conditions, with the 80th and 90th percentiles of NO3–N found to be 0.04 ± 0.01 and 0.16 ± 0.01, respectively (the 95th percentile could not be estimated reliably). For both oxic and anoxic groundwater, where a site-specific investigation has not been conducted to estimate reference conditions at a local scale, we suggest that the 80th percentile is an appropriate national-scale default threshold, to match the thresholds used for surface waters under the Australian and New Zealand Guidelines for Fresh and Marine Water Quality.

Successive alkali diffusion ceramic reactor: Long-term removal of acidity and heavy metals in acid mine drainage

A novel alkali diffusion reactor using ceramic porous media (ceram-ADR) was newly developed for long-term treatment of acidity and heavy metals in acid mine drainage (AMD) without external energy. The batch and column tests were performed to investigate the neutralization capabilities of six alkaline chemicals (i.e., MgO, CaCO3, CaO, SiO2, Na2CO3, and NaHCO3) and the effects on pore size and hydraulic retention time (HRT) of ceram-ADRs. Among these six alkaline chemicals, the ceram-ADR containing NaHCO3 yielded a suitable pH range for water quality guideline (pH values from 5.0 to 9.5) for an HRT of 1–2 days as well as had the best efficiency in terms of consistent alkaline diffusion and long-term heavy metal removal (>99 %). The precipitation process was found to be a major mechanism in the removal of heavy metals. Based on the continuous column tests, it was evaluated that the ceram-ADR successfully treated three consecutive runs with approximately 340 bed volumes of AMD for neutralization and heavy metal removal, indicating that the ceram-ADR can be maintained for over three years without a lapse in performance. Capsule abstractAn alkali diffusion reactor based on porous ceramic media is developed for the long-term remediation of acidity and heavy metals in AMD.