Surface Water Ecosystems Research Articles

Pollution and risk assessment of heavy metals in rivers in the antimony capital of Xikuangshan

Xikuangshan (XKS) is the world's largest antimony mining region, and its exploitation for hundreds of years has also resulted in serious soil erosion, fragile ecology, contaminated water, and shortage water. Through systematic and scientific collection samples from the rivers in XKS, the Nemerow index (NI), modified heavy metal pollution index (m-HPI), ecological risk index, and health risk indexeswere used to evaluate and analyze the water quality, pollution levels and risks of heavy metals (Sb, As, Mn, Pb, Zn, Hg, Cd) to ecology and humans in XKS. The results showed that the average concentrations of TN, TP, Sb, As and Hg in surface water were 0.48 mg/L (0–4.34 mg/L), 2.58 mg/L (0–4.34 mg/L), 1.05 mg/L (0.0009–5.33 mg/L), 1.06 mg/L (BDL–19.60 mg/L) and 0.00084 mg/L (LDBL–0.0036 mg/L), respectively, exceeding the limits of the Chinese surface water quality standards. Based on the m-HPI method, only 8.57% of the sampling points are classified as the worst water quality. However, according to the NI method, about 7.14% and 87.16% of the sampling points in the study area are moderately and severely polluted, respectively. The results of heavy metal pollution based on the NI evaluation is were more serious than that on the m-HPI method. The values of ecological risk assessment varied from 22.69 to 7351.20, revealed that heavy metals pose a very serious risk to the surface water ecosystem at more than 50% of the sampling sites, and Sb and As are the main pollutants, followed by Hg. The total non-carcinogenic risk index (TCR) for adults and children were 47.70 and 90.10 respectively, Sb and As is the main non-carcinogenic risk factor. For adults and children, the average carcinogenic risk (CR) of As was 6.49 × 10–3 and 1.05 × 10–2, respectively, and exceeded the threshold of 1 × 10–4, indicating a high carcinogenic risk.

Tracking the influence of antibiotics, antibiotic resistomes, and salinity gradient in modulating microbial community assemblage of surface water and the ecological consequences

The ecological impacts of antibiotics and antibiotic resistance genes (ARGs) on water ecology remain elusive in natural environments. We investigated the influence of antibiotics, ARGs and salinity gradient on the surface water ecosystem. Cefquinome (104.2 ± 43.6 ng/L) and cefminox (16.2 ± 7.50 ng/L) cephalosporins were predominant in all sites. Antibiotic contamination was increased in the estuary ecosystems compared to the freshwater ecosystems by 6%. Bacterial diversity could resist changes in salinity, but the relative abundance of some bacterial genera; Pseudoalteromonas, Glaciecola, norank_f__Arcobacteraceae, and Pseudohongiella was increased in the estuary zone (salinity>0.2%). The eukaryotic composition was increased in the subsaline environments (<0.2%), but the higher salinity in the saline zone inhibited the eukaryotic diversity. The relative abundance of ARGs was significantly higher in the estuary than in freshwater ecosystems, and ARGs interactions and mobile elements (aac(6′)-Ib(aka_aacA4)-01, tetR-02, aacC, intI1, intI-1(clinic), qacEdelta1-01, and strB) were the predominant factors responsible for the ARGs propagation. Antibiotics associated with corresponding and non-corresponding ARGs and potentially created an adverse environment that increased the predation and pathogenicity of the aquatic food web and inhibited the metabolic functions. Surface water are first-line-ecosystems receiving antibiotics and ARGs hence our findings provided vital insights into understanding their ecological consequences on surface water ecosystems.

A bibliometric analysis of leachate publications by ASEAN authors

Leachates are the aqueous effluent produced from waste filtration of rainwater, biochemical activities in the waste cells, and the unavoidable water content of the waste itself. Leachate can travel into soil and subsoil, seriously affecting the land, surface water, and groundwater ecosystems. Leachates typically contain significant quantities of organic matter, ammonia-nitrogen (NH3-N), toxic chemicals, and organic and inorganic chlorinated salts, which are detrimental to living and biodiversity. Based on the significant risk posed by leachate, many kinds of research have been conducted on these environmental concerns. Therefore, this paper aims to analyse and report leachate-related publications by ASEAN authors based on the data collected from the Scopus database. As of 24th April 2020, a total number of 1133 articles were retrieved and analysed. This study examined publication productivity by analysing descriptive publication patterns and visualising keywords co-occurrences. The results showed that there had been an increase in the literature on leachate growth rate from 1989 until 2020. However, the number of publications slightly dropped in 2011 and 2014. This study revealed the widespread scholarly communication techniques in leachate research, which will assist future researchers in identifying the fundamental parts of this body of knowledge. In conclusion, this study enables researchers to develop innovative solutions to the leachate environmental problem by assessing the bibliometric parameters that provide the study’s crucial and noteworthy findings.

Climatic controls on phosphorus concentrations in The Loch, Loch Vale Watershed, Rocky Mountain National Park, Colorado, USA since the last glacial maximum

AbstractThe alpine–subalpine Loch Vale watershed (LVW) of Colorado, USA, has relatively high natural lithogenic P5+ fluxes to surface waters. For 1992–2018, the largest number of stream samples with P5+ concentrations ([P5+]) above detection limits occurred in 2008, corresponding with the highest frost-cracking intensity (FCI). Therefore, relatively cold winters and warm summers with a comparatively low mean annual temperature partly influence stream [P5+]. Sediment cores were collected from The Loch, an outlet lake of the LVW. Iron-, Al-, and Mn-oxide-bound phosphorus (adsorbed and authigenic phosphates; NP) serves as a proxy measurement for paleolake [P5+]. The highest NP in the core occurred during the cold and dry Allerød interstade. The lowest NP concentrations in the core occurred during climatically very wet periods in the Late Pleistocene and Early Holocene. Therefore, [P5+] are highest with relatively cold winters followed by relatively warm summers, relatively low mean annual temperatures, and relatively little rainfall and/or cryospheric melting. Currently the LVW is experiencing warming and melting of the permanent cryosphere with a rapidly declining FCI since 2008. This has the potential to dramatically decrease [P5+] in surface water ecosystems of the LVW, reducing biological productivity, enhancing P-limitation, and increasing ecosystem reliance on aeolian P5+.

A case study of distribution and characteristics of microplastics in surface water and sediments of the seas around Shenzhen, southern coastal area of China

Microplastics (MPs), known to cause environmental pollution, is attracting a growing attention worldwide owing to their extensive existence and potential risks to biota. The marginal sea areas are suspected to be especially susceptible to MPs pollution. Unfortunately, data on MPs in the surface water and sediments ecosystems are still limited, particularly in the southern coastal areas of China. The study was successfully utilized to explore the distribution and characteristics of MPs below 5 mm collected from 14 sites in the seas around Shenzhen, a typical special economic zone of China. MPs were detected in both surface water and sediments with concentrations ranging from 3.8 to 7.8 items per liter and 2.6 × 103 to 10.0 × 103 items per kilogram, respectively. The highest abundance of MPs appeared in S5/S9 and S14 in surface water and sediments, respectively. Fiber and film with small particle size (<0.5 mm) were identified as typical and abundant MPs type among all samples. In addition, polyethylene (PE) was considered as dominant forms of MPs in surface water and sediment samples. Results from this study indicated a positive correlation with abundance of MPs and urbanization rate, which also showed an evident difference of MPs in different urban functional areas. Based on the types and quantity of detected MPs, we assessed the risk of MPs pollution in this study area, and the ecological risk category of MPs was at a high level. Importantly, our work might be employed as a potential information so as to better understand MPs pollution, source tracing and ecological risk assessment, which enhances the possibility of achieving effective control and supervision of MPs pollution in southern coastal aera of China.

Long-term trends and factors influencing rainwater chemistry in the Tatra Mountains, Poland

The results of rainwater chemistry monitoring in the Tatra Mountains, Poland, during the periods1993–1994 and 2002–2019 were used to determine long-term trends and the factors influencing rainwater chemistry in the last two decades. In the early 1990’s, the study area was characterized by prominent acid rains with a pH of 4.4 that affected surface water, meadows, and forest ecosystems. A rising pH temporal trend has been observed during the following years, indicating improving air quality. This trend has also been observed in measured ionic concentrations and reduced wet deposition loads of sulfur- and nitrogen-containing acid-forming compounds. The neutralization capacity of rainwater in Kasprowy Wierch increased over the last twenty years and has mostly been dominated by NH4+. The ammonium availability index has been steadily increasing between years 2002 and 2019 but remains less than 1. This statistically significant relationship also indicates that a portion of neutralization occurs in the lower part of the atmosphere due to ammonium-related neutralization processes. The acidic potential (AP) and the ratio AP/NP (acidic potential/neutralization potential) have been declining during the same time. The stated trends in rainwater chemistry reflect the transformation to more environmentally sustainable economies in the region. Similar changes have been observed in neighboring countries in the region, including Slovakia, the Czech Republic, and Lithuania.

Deteriorating water quality state on the structural assemblage of aquatic insects in a North-Western NigerianRiver

ABSTRACT Benthic aquatic insects receive the most direct impact when surface waters are perturbed. However, scarce data and understanding about activities’ effects on surface water ecosystems remain a critical challenge for water resource managers and policymakers in tropical regions. In this study, we surveyed the implications of deteriorating physical and chemical parameters on aquatic insects’ structural assemblage to ascertain the ecological health of River Hadejia in North-Western Nigerian. We sampled aquatic insects and physicochemical parameters in three stations influenced by various land-use activities such as informal settlements and agricultural activities for six months. The two-way analysis of variance (ANOVA) revealed physicochemical parameters such as transparency, depth, and nitrate were not significantly affected by sites’ land-use activities (p > .05) in the six months sampled. However, mean electrical conductivity was lowest in Station 3 (104.3 ± 8.04 µS/cm). Dissolved oxygen (DO), five days biochemical oxygen demand (BOD5) values recorded portray a relatively perturbed water system. We recorded four aquatic insects orders belonging to 11 families and taxa. Dytiscus sp. was the most abundant taxon in the study area. A total of 44, 37, and 35 individuals of aquatic insects were recorded in stations 1, 2, and 3 in the river. The Post hoc test performed for all the diversity indices were not significantly different between the studied stations (p > .05). Canonical correspondence analysis (CCA) revealed poor relationship between the physicochemical parameters and the aquatic insects. However, Gyrinus sp. was positively affected by increased water depth, showing a strong negative association with depth. Cluster analysis revealed that aquatic insects’ assemblage structures were mainly grouped by temporal factors (months) rather than spatial differences between the sites. Overall, this study provides further insights and understanding regarding land-use impacts on the ecological health of the River Hadejia, and we recommend more stringent regulations to control human pressure on the river systems within the studied area to enable surface waters in the area to sustain the provision of desired and valued ecosystem services.

The evolving role of weather types on rainfall chemistry under large reductions in pollutant emissions

Long-term change and shorter-term variability in the atmospheric deposition of pollutants and marine salts can have major effects on the biogeochemistry and ecology of soils and surface water ecosystems. In the 1980s, at the time of peak acid deposition in the UK, deposition loads were highly dependent on prevailing weather types, and it was postulated that future pollution recovery trajectories would be partly dependent on any climate change-driven shifts in weather systems. Following three decades of substantial acidic emission reductions, we used monitoring data collected between 1992 and 2015 from four UK Environmental Change Network (ECN) sites in contrasting parts of Great Britain to examine the trends in precipitation chemistry in relation to prevailing weather conditions. Weather systems were classified on the basis of Lamb weather type (LWT) groupings, while emissions inventories and clustering of air mass trajectories were used to interpret the observed patterns. Concentrations of ions showed clear differences between cyclonic-westerly-dominated periods and others, reflecting higher marine and lower anthropogenic contributions in Atlantic air masses. Westerlies were associated with higher rainfall, higher sea salt concentrations, and lower pollutant concentrations at all sites, while air mass paths exerted additional controls. Westerlies therefore have continued to favour higher sea salt fluxes, whereas emission reductions are increasingly leading to positive correlations between westerlies and pollutant fluxes. Our results also suggest a shift from the influence of anthropogenic emissions to natural emissions (e.g., sea salt) and climate forcing as they are transported under relatively cleaner conditions to the UK. Westerlies have been relatively frequent over the ECN monitoring period, but longer-term cyclicity in these weather types suggests that current contributions to precipitation may not be sustained over coming years.

Optimal Allocation Model for Water Resources Coupled with Ecological Value Factors—A Case Study of Dalian, China

The surface water ecosystem has important ecological value and plays an important supporting and guarantee role in the sustainable development of human society. In this study, an inexact two-stage stochastic programming (ITSP) model was developed for supporting water resource allocation for the four main water sectors (industry, municipal, agriculture, and ecological environment). Several scenarios corresponding to different flow patterns, which reflect different probabilities of water resource availability and environmental carrying capacity, were examined. On the basis of traditional water resource allocation, this model adds consideration of ecological value factors, which is conducive to the synergistic efficiency of socio-economic and ecological water consumption. Results revealed that the water resource carrying capacity, ecological value factors, and water environmental capacity are the main factors affecting the optimal allocation of water resources. Furthermore, the optimal allocation scheme for water resources coupled with ecological value factors were determined to realize the coordinated development of social economic benefits and ecological benefits. The current study findings are of great significance for establishing a rational water resource management system for water resource exploitation and utilization. This model can be used to guide various departments in Dalian to formulate an optimal water resources allocation scheme by considering ecological value factors, and provide a basis for realizing the coordinated development of Dalian’s socio-economic development goals, water resource utilization, and environmental quality improvement.

Maastrichtian–Rupelian paleoclimates in the southwest Pacific – a critical re-evaluation of biomarker paleothermometry and dinoflagellate cyst paleoecology at Ocean Drilling Program Site 1172

Abstract. Sea surface temperature (SST) reconstructions based on isoprenoid glycerol dialkyl glycerol tetraether (isoGDGT) distributions from the Eocene southwest (SW) Pacific Ocean are unequivocally warmer than can be reconciled with state-of-the-art fully coupled climate models. However, the SST signal preserved in sedimentary archives can be affected by contributions of additional isoGDGT sources. Methods now exist to identify and possibly correct for overprinting effects on the isoGDGT distribution in marine sediments. Here, we use the current proxy insights to (re-)assess the reliability of the isoGDGT-based SST signal in 69 newly analyzed and 242 reanalyzed sediments at Ocean Drilling Program (ODP) Site 1172 (East Tasman Plateau, Australia) following state-of-the-art chromatographic techniques. We compare our results with paleoenvironmental and paleoclimatologic reconstructions based on dinoflagellate cysts. The resulting ∼ 130 kyr resolution Maastrichtian–Oligocene SST record based on the TetraEther indeX of tetraethers with 86 carbon atoms (TEX86) confirms previous conclusions of anomalous warmth in the early Eocene SW Pacific and remarkably cool conditions during the mid-Paleocene. Dinocyst diversity and assemblages show a strong response to the local SST evolution, supporting the robustness of the TEX86 record. Soil-derived branched GDGTs stored in the same sediments are used to reconstruct mean annual air temperature (MAAT) of the nearby land using the Methylation index of Branched Tetraethers with 5-methyl bonds (MBT'5me) proxy. MAAT is consistently lower than SST during the early Eocene, independent of the calibration chosen. General trends in SST and MAAT are similar, except for (1) an enigmatic absence of MAAT rise during the Paleocene–Eocene Thermal Maximum and Middle Eocene Climatic Optimum, and (2) a subdued middle–late Eocene MAAT cooling relative to SST. Both dinocysts and GDGT signals suggest a mid-shelf depositional environment with strong river runoff during the Paleocene–early Eocene progressively becoming more marine thereafter. This trend reflects gradual subsidence and more pronounced wet/dry seasons in the northward-drifting Australian hinterland, which may also explain the subdued middle Eocene MAAT cooling relative to that of SST. The overall correlation between dinocyst assemblages, marine biodiversity and SST changes suggests that temperature exerted a strong influence on the surface-water ecosystem. Finally, we find support for a potential temperature control on compositional changes of branched glycerol monoalkyl glycerol tetraethers (brGMGTs) in marine sediments. It is encouraging that a critical evaluation of the GDGT signals confirms that most of the generated data are reliable. However, this also implies that the high TEX86-based SSTs for the Eocene SW Pacific and the systematic offset between absolute TEX86-based SST and MBT'5me-based MAAT estimates remain without definitive explanation.

Effects of a natural precipitation gradient on fish and macroinvertebrate assemblages in coastal streams.

Anthropogenic climate change is expected to increase the aridity of many regions of the world. Surface water ecosystems are particularly vulnerable to changes in the water-cycle and may suffer adverse impacts in affected regions. To enhance our understanding of how freshwater communities will respond to predicted shifts in water-cycle dynamics, we employed a space for time approach along a natural precipitation gradient on the Texas Coastal Prairie. In the spring of 2017, we conducted surveys of 10 USGS-gauged, wadeable streams spanning a semi-arid to sub-humid rainfall gradient; we measured nutrients, water chemistry, habitat characteristics, benthic macroinvertebrates, and fish communities. Fish diversity correlated positively with precipitation and was negatively correlated with conductivity. Macroinvertebrate diversity peaked within the middle of the gradient. Semi-arid fish and invertebrate communities were dominated by euryhaline and live-bearing taxa. Sub-humid communities contained environmentally sensitive trichopterans and ephemeropterans as well as a variety of predatory fish which may impose top-down controls on primary consumers. These results warn that aridification coincides with the loss of competitive and environmentally sensitive taxa which could yield less desirable community states.

The importance of early data collection in quarry development consent applications; linking hydrogeological assessment to the decision makers’ legal framework, a case study

The working of superficial deposits frequently interacts with the groundwater table and thus may affect surface water and groundwater dependent terrestrial ecosystems. The Habitats Directive and the Water Framework Directive require detailed consideration of these potential effects during any application for planning consent or other authorizations and during periodic reviews. These assessments need to consider water resources impacts, the potential for pollution and whether the natural water chemistry may be changed in a way that could change ecological conditions. Early recognition of these challenges, and a well-structured hydrogeological investigation programme to properly characterize the site, is essential to facilitate timely progress through the planning process. This case study presents the approach to hydrogeological characterization and assessment used at the proposed Upwood Quarry, Oxfordshire, which is adjacent to a calcareous wetland protected at European level. Through careful characterization and stakeholder engagement, planning consent was obtained. We consider lessons that may be applied to other sites especially with increased regulation of dewatering abstractions and consider the potential impacts of recent court decisions.

Sources and Optical Dynamics of Chromophoric Dissolved Organic Matter in Different Types of Urban Water Bodies

In the past few decades, China's rapid industrial activities and urbanization processes have greatly impacted the urban surface water ecosystem. The changes in the quality of urban surface water directly affect the supply and carbon cycling of urban waters. We collected 50 water samples from urban rivers, lakes, and reservoirs in the city of Changchun in June 2020. Three-dimensional fluorescence spectroscopy coupled with parallel factor analysis (EEMs-PARAFAC) was used to unravel the optical characteristics, composition, and sources of chromophoric dissolved organic matter (CDOM). Our results indicated that the mean concentration of DOC is significantly higher in urban rivers than in reservoirs (t-test, P<0.05), and the mean UV absorption coefficient of CDOM a254 of urban rivers is significantly larger than that of park lakes and reservoirs (t-test, P<0.05), indicating that urban rivers have the highest concentration of CDOM. The spectral slope of CDOM absorption S275-295 and the spectral slope ratio SR were shown to be higher in park lakes than in reservoirs, and even higher than in urban rivers (t-test, P<0.001). Three fluorescent components were obtained using PARAFAC, namely terrestrial human-like (C1), microbial human-like (C2) and tryptophan-like (C3) components. The mean fluorescence intensity of C1-C3 was significantly higher in urban rivers than in both the park lakes and reservoirs (t-test, P<0.005), and the mean fluorescence intensity of C1 in the reservoir water body was significantly higher than that of C2 and C3 (t-test, P<0.005), indicating that the discharge of municipal wastewater likely contributes significantly to the CDOM pool of urban rivers in Changchun, and the contribution percentages of highly bio-labile protein-like components to the CDOM pool in these waters are high. Urban wastewater treatment should be strengthened to effectively protect water quality, as well as the economic, environmental, and ecological functions of urban waters in Changchun City.

Eutrophication causes invertebrate biodiversity loss and decreases cross-taxon congruence across anthropogenically-disturbed lakes

Eutrophication is a major problem currently impacting many surface water ecosystems. Impacts of increased nutrient concentrations on biodiversity may differ between different scales, different organism groups, and different trophic states. Surveys at different spatial scales have suggested that biodiversity of different taxa may exhibit significant cross-taxon congruence. In our study, we examined the diversity of zooplankton and zoobenthos across 261 lakes in the Lake Taihu watershed, an area that is undergoing a severe eutrophication process. We tested the cross-taxon congruence in species richness and Shannon-Wiener diversity between zooplankton and zoobenthos along a nutrient gradient across the lakes. Our findings were consistent with the intermediate disturbance hypothesis, considering nutrient input as the disturbance. Also, we found significant cross-taxon congruence between zooplankton and zoobenthos diversities. Our results confirmed that excess nutrient levels resulted in diversity loss and community simplification. Zoobenthos were more sensitive to nutrient increases compared with zooplankton, which decreased cross-taxon congruence because these organism groups did not respond similarly to the anthropogenic disturbance.

Organic contaminants of emerging concern in leachate of historic municipal landfills.

Many types of contaminants of emerging concern (CECs), including per- and poly-fluoroalkyl substances (PFAS), have been found in leachate of operating municipal landfills. However, there is only limited information on CECs presence in leachate of historic landfills (≥3 decades since closure, often lacking engineered liners or leachate collection systems) at concentrations that may pose a risk to nearby wells and surface water ecosystems. In this study, 48 samples of leachate-impacted groundwater were collected from 20 historic landfills in Ontario, Canada. The CECs measured included artificial sweeteners (ASs), PFAS, organophosphate esters (OPE), pharmaceuticals, bisphenols, sulfamic acid, perchlorate, and substituted phenols. The common presence of the AS saccharin, a known indicator of old landfill leachate, combined with mostly negligible levels of the AS acesulfame, an indicator of modern wastewater, revealed that most samples were strongly influenced by leachate and not cross-contaminated by wastewater (which can contain these same CECs). Several landfills, including ones closed in the 1960s, had total PFAS concentrations similar to those previously measured at modern landfills, with a maximum observed here of 12.7μg/L. Notably elevated concentrations of several OPE, sulfamic acid, cotinine, and bisphenols A and S were found at many 30-60 year-old landfills. There was little indication of declining concentrations with landfill age, suggesting historic landfills can be long-term sources of CECs to groundwater and that certain CECs may be useful tracers for historic landfill leachate. These findings provide guidance on which CECs may require monitoring at historic landfill sites and wastewater treatment plants receiving their effluent.

Potential for Mycorrhizae-Assisted Phytoremediation of Phosphorus for Improved Water Quality.

During this 6th Great Extinction, freshwater quality is imperiled by upland terrestrial practices. Phosphorus, a macronutrient critical for life, can be a concerning contaminant when excessively present in waterways due to its stimulation of algal and cyanobacterial blooms, with consequences for ecosystem functioning, water use, and human and animal health. Landscape patterns from residential, industrial and agricultural practices release phosphorus at alarming rates and concentrations threaten watershed communities. In an effort to reconcile the anthropogenic effects of phosphorus pollution, several strategies are available to land managers. These include source reduction, contamination event prevention and interception. A total of 80% of terrestrial plants host mycorrhizae which facilitate increased phosphorus uptake and thus removal from soil and water. This symbiotic relationship between fungi and plants facilitates a several-fold increase in phosphorus uptake. It is surprising how little this relationship has been encouraged to mitigate phosphorus for water quality improvement. This paper explores how facilitating this symbiosis in different landscape and land-use contexts can help reduce the application of fertility amendments, prevent non-point source leaching and erosion, and intercept remineralized phosphorus before it enters surface water ecosystems. This literature survey offers promising insights into how mycorrhizae can aid ecological restoration to reconcile humans’ damage to Earth’s freshwater. We also identify areas where research is needed.

Use of Postregistration Monitoring Data to Evaluate the Ecotoxicological Risks of Pesticides to Surface Waters: A Case Study with Chlorpyrifos in the Iberian Peninsula.

Chemical monitoring data sets such as those provided by the implementation of the Water Framework Directive (WFD) offer opportunities to evaluate the ecological risks of pesticides under large spatiotemporal scales and to evaluate the protectiveness of the current prospective risk-assessment framework. As a case study, we used the monitoring data set for the insecticide chlorpyrifos to perform a probabilistic risk assessment for Iberian surface-water ecosystems. The specific objectives of the study were 1) to assess the occurrence of chlorpyrifos in relation to different agricultural production land uses, 2) to assess the spatiotemporal variation in the exceedance of the European WFD short- and long-term environmental quality standards (maximum allowable concentration environmental quality standard [MAC-EQS] and annual average [AA] EQS), and 3) to perform a probabilistic risk assessment for freshwater invertebrates. A database that contains chlorpyrifos concentrations from 14 600 surface water samples taken between 2012 and 2017 in the Iberian Peninsula (Spain and Portugal) was analyzed, and chlorpyrifos was detected in 21% of these samples. The MAC-EQS was exceeded in 2% of the cases, whereas the AA-EQS was exceeded in 18% of the cases. The majority of the exceedances took place in the littoral areas of the eastern and southeastern parts of the Iberian Peninsula, particularly in areas with dominant citrus production during late spring, late summer, and autumn. The present study indicates unacceptable risks posed by chlorpyrifos to Iberian surface waters over the study period, although it was approved for use in Europe. The present study supports the need to perform further postregistration monitoring assessments with other pesticides following similar approaches, which can help to identify possible pesticide-misuse practices and improvements of the prospective risk-assessment framework. Environ Toxicol Chem 2021;40:500-512. © 2020 SETAC.

Freshwater Sediment Microbial Communities Are Not Resilient to Disturbance From Agricultural Land Runoff.

Microorganisms are critically important for the function of surface water ecosystems but are frequently subjected to anthropogenic disturbances at either acute (pulse) or long-term (press) scales. Response and recovery of microbial community composition and function following pulse disturbance is well-studied in controlled, laboratory scale experiments but is less well-understood in natural environments undergoing continual press disturbance. The objectives of this study were to determine the drivers of sediment microbial compositional and functional changes in freshwaters receiving continual press disturbance from agricultural land runoff and to evaluate the ability of the native microbial community to resist disturbance related changes as a proxy for freshwater ecosystem health. Freshwater sediments were collected seasonally over 1 year in Kewaunee County, Wisconsin, a region impacted by concentrated dairy cattle farming, manure fertilization, and associated agricultural runoff which together serve as a press disturbance. Using 16S rRNA gene amplicon sequencing, we found that sediments in locations strongly impacted by intensive agriculture contain significantly higher abundances (p < 0.01) of the genera Thiobacillus, Methylotenera, Crenotrhix, Nitrospira, and Rhodoferax compared to reference sediments, and functions including nitrate reduction, nitrite reduction, and nitrogen respiration are significantly higher (p < 0.05) at locations in close proximity to large farms. Nine species-level potential human pathogens were identified in riverine sediments including Acinetobacer lwoffi and Arcobacter skirrowii, two pathogens associated with the cattle microbiome. Microbial community composition at locations in close proximity to intensive agriculture was not resistant nor resilient to agricultural runoff disturbance within 5 months post-disturbance but did reach a new, stable microbial composition. From this data, we conclude that sediment microbial community composition is sensitive and shifts in response to chemical and microbial pollution from intensive agriculture, has a low capacity to resist infiltration by non-native, harmful bacteria and, overall, the natural buffering capacity of freshwater ecosystems is unable to fully resist the impacts from agricultural press disturbance.

Microbial Community and Atrazine-Degrading Genetic Potential in Deep Zones of a Hypersaline Lake-Aquifer System

The chemical composition of groundwater and related surface water ecosystems can be modified by intensive agricultural activities. This is the case of the Natural Reserve of Pétrola saline lake (Albacete, SE Spain), which constitutes the discharge area of an unconfined aquifer. The extended use of fertilizers and pesticides poses a threat to ecosystem sustainability. One of the most applied herbicides worldwide has been atrazine. Despite being prohibited in Spain since 2007 by European regulations, atrazine can still be detected due to its high persistence in the environment. Atrazine degradation pathways are mediated by biological processes performed by microorganisms with adapted metabolic mechanisms that make in situ bioremediation possible. To evaluate the presence of such microorganisms in the unconfined aquifer, groundwater was collected from a flowing 37.9 m deep piezometer. DNA was extracted, and the bacterial 16S rRNA gene was amplified and cloned. Later, 93 clones were sequenced, providing the first molecular assessment of bacterial community structure in the deep zones of the aquifer. Some of these bacteria have been previously described to be involved in atrazine degradation. In addition, 14 bacteria were isolated from the groundwater samples and identified by 16S rRNA gene sequencing. DNA from these bacteria was subjected to PCR assays with primers designed for the genes involved in the atrazine degradation pathway. Positive results in the amplification were found in at least three of these bacteria (Arthrobacter sp., Nocardioides sp. and Pseudomonas sp.). The atrazine-degrading genetic potential was shown to be dependent on the trzN and atzA,B,C gene combination. These results suggest for the first time the adaptation of the bacterial population present in deep aquifer zones to atrazine exposure, even after more than 15 years of its ban in Spain. In addition, this study provides the baseline data about the bacterial communities found in deep aquifer zones from the hypersaline lake-aquifer system.

The joint effect of natural and human-induced environmental factors on surface water quality in the Birim North District of Ghana

Abstract Anthropogenic activities threaten surface water quality across the globe, especially in contexts where monitoring is non-existent or weak. Our understanding of the effect, order and magnitude of natural and human-induced environmental factors on surface water quality is limited. This study assessed the effect, predictive order and magnitude of natural and human-induced environmental variables on surface water quality in the Birim North District of Ghana. Approximately 540 samples were collected from 15 rivers and streams in 2018 and analysed using 31 indicators. Landsat satellite images (2018 and 2019) of the study area were analysed for land use land cover data. The data were fitted to ordinary least squares (OLS) regression model. Season (50%) most accounted for variability in the surface water quality whereas elevation and forest cover accounted for 28% and 21%, respectively. Surface water quality in the Akoase and Nyafoman/Noyem clusters were 30% and 10% respectively better in quality than the Adofokrom/Amenam cluster. The increasing order of magnitude of variables in predicting surface water quality was Buffer, Cultivated area, Built-up, Forest, Rivers and streams cluster, Elevation, and Season. Consequently, management interventions for surface water ecosystems should account for spatio-temporal heterogeneity in the factors that influence surface water quality.