Influence of anthropogenic inputs and a high-magnitude flood event on metal contamination pattern in surface bottom sediments from the Deba River urban catchment

The purpose of this study was to assess the influence of anthropogenic factors (infrastructure construction and industrial and wastewater inputs) and hydrological factors (high-magnitude flood events) on metal and organic contamination and on the source variability of sediments taken from the Deba River and its tributaries. The pollution status was evaluated using a sequential extraction procedure (BCR 701), enrichment factor, individual and global contamination factors and a number of statistical analysis methods. Zn, Cu and Cr were found to have significant input from anthropogenic sources, with moderately severe enrichment, together with an extremely high potential risk of contamination. The principal scavenger of Cu and Cr was organic matter, whereas Zn was uniformly distributed among all non-residual fractions. For Fe, the anthropogenic contribution was more obviously detected in bulk sediments (b2 mm) than in fine fractions (b63 μm). Finally, the recent construction of a rail tunnel traversing Wealden Facies evaporites, together with intense rainfalls, was the main reason for the change in the source variability of bottom sediments and metal distribution in headwaters. The occurrence of a high-magnitude flood event resulted in a washout of the river bed and led to a general decrease in finegrained sediment and metal concentrations in labile fractions of channel-bottom sediments, and a consequent downstream transfer of the pollution

Non-target effects of three formulated pesticides on microbially-mediated processes in a clay-loam soil

An experiment was performed to study non-target effects of difenoconazole (fungicide), deltamethrin (insecticide) and ethofumesate (herbicide) on microbial parameters in a clay-loam soil. Pesticides were applied as commercial formulations to soil samples at different concentrations (5, 50 and 500 mg kg−1 DW soil) and then incubated under laboratory conditions for 3 months. Throughout the incubation period, microbial parameters were determined at days 7, 30, 60 and 90. At 5 mg kg−1 DW soil, none of the three pesticides caused significant changes in soil microbial parameters. In contrast, at 500 mg kg−1 DW soil, pesticide application decreased overall soil microbial activity, negatively affecting the activity of soil enzymes. Similarly, at 500 mg kg−1 DW soil, difenoconazole and ethofumesate, but not deltamethrin, caused a pesticide-induced stress on soil microbial communities, as reflected by the respiratory quotient. Besides, deltamethrin and ethofumesate at 50 and 500 mg kg−1 DW soil resulted in lower values of denitrification potential. It was concluded that, although pesticide concentration had a somewhat inconsistent and erratic effect on soil microbial parameters, pesticide application at 500 mg kg−1 DW soil did have an impact on many of the microbial parameters studied here

Links Between Data On Chemical And Biological Quality Parameters In Wastewater-Impacted River Sediment And Water Samples

In many urban catchments, the discharge of effluents from wastewater treatment plants (WWTPs), as well as untreated wastewaters (UWWs), presents a major challenge for the maintenance of river sediment and water quality. The discharge of these effluents cannot only increase the concentration of metals, nutrients and organic compounds in fluvial ecosystems, but also alter the abundance, structure and function of river bacterial communities. Here, we present data on chemical and biological quality parameters in wastewater-impacted and non-impacted river surface sediment and water samples. Overall, the concentration of nutrients (inorganic nitrogen) and some heavy metals (Zn, Ni and Cr) was positively correlated with the nirS/16S rRNA ratio, while nirK- and nosZ-denitrifier populations were negatively affected by the presence of ammonium in sediments. Bacterial community structure was significantly correlated with the (i) combined influence of nutrient and metal concentrations, (ii) the contamination level (non-impacted vs. impacted sites), (iii) type of contamination (WWTP or UWW), and (iv) location of the sampling sites. Moreover, the higher abundance of five genera of the family Rhodocyclaceae detected in wastewater-impacted sites is also likely to be an effect of effluent discharge. The data presented here complement a broader study (Martinez-Santos et al., 2018) [1] and they are particularly useful for those interested in understanding the impact of wastewater effluents on the abundance, structure and function of river bacterial communities involved in nitrogen cycling

Combining punctual and high frequency data for the spatiotemporal assessment of main geochemical processes and dissolved exports in an urban river catchment

The assessment of dissolved loadings and the sources of these elements in urban catchments' rivers is usually measured by punctual sampling or through high frequency sensors. Nevertheless, the combination of both methodologies has been less common even though the information they give is complementary. Major ion (Ca2+, Mg2+, Na+, K+, Cl−, SO42−, and alkalinity), organic matter (expressed as Dissolved Organic Carbon, DOC), and nutrients (NO3−, and PO43−) are punctually measured in the Deba river urban catchment (538 km2), in the northern part of the Iberian Peninsula (draining to the Bay of Biscay). Discharge, precipitation, and Electrical Conductivity (EC) are registered with a high frequency (10 min) in three gauging stations. The combination of both methodologies has allowed the assessment of major geochemical processes and the extent of impact of anthropogenic input on major composition of riverine water, as well as its spatial and temporal evolution. Three methodologies for loading estimation have been assessed and the error committed in the temporal aggregation is quantified. Results have shown that, even though carbonates dominate the draining area, the water major ion chemistry is governed by an evaporitic spring in the upper part of the catchment, while anthropogenic input is specially noted downstream of three wastewater treatment plants, in all nutrients and organic matter. The results of the present work illustrate how the combination of two monitoring methodologies allows for a better assessment of the spatial and temporal evolution on the major water quality in an urban catchment

A model for evaluating continental chemical weathering from riverine transports of dissolved major elements at a global scale

This study presents a process-based-empirical model for the assessment of ionic fluxes derived from chemical weathering of rocks (ICWR) at a global scale. The equations are designed and the parameters fitted using riverine transport of dissolved major ions Ca2+, Mg2+, K+, Na+, Cl−, SO42−, and alkalinity at a global scale by combining point sampling analysis with spatial descriptions of hydrology, climate, topography, lithology and soil variables such as mineral composition and regolith thickness. Different configurations of the model are considered and the results show that the previously reported “soil shielding” effect on chemical weathering (CW) of rocks presents different values for each of the ions considered. Overall, there is good agreement between median and ranges in observed and simulated data, but further analysis is required to downscale the model to catchment scale. Application to the global scale provides the first global ICWR map, resulting in an average cationic flux derived from chemical weathering of 734·106 Mg·y−1, where 58% is Ca2+, 15% is Mg2+, 24% is Na+ and 3% is K+, and an average anionic flux derived from chemical weathering of 2640·106 Mg·y−1, where 74% is alkalinity, 18% is SO42−, and 8% is Cl−. Hyperactive and hotspot areas are elucidated and compared between ions

Links between data on chemical and biological quality parameters in wastewater-impacted river sediment and water samples

In many urban catchments, the discharge of effluents from wastewater treatment plants (WWTPs), as well as untreated wastewaters (UWWs), presents a major challenge for the maintenance of river sediment and water quality. The discharge of these effluents cannot only increase the concentration of metals, nutrients and organic compounds in fluvial ecosystems, but also alter the abundance, structure and function of river bacterial communities. Here, we present data on chemical and biological quality parameters in wastewater-impacted and non-impacted river surface sediment and water samples. Overall, the concentration of nutrients (inorganic nitrogen) and some heavy metals (Zn, Ni and Cr) was positively correlated with the nirS/16S rRNA ratio, while nirK- and nosZ-denitrifier populations were negatively affected by the presence of ammonium in sediments. Bacterial community structure was significantly correlated with the (i) combined influence of nutrient and metal concentrations, (ii) the contamination level (non-impacted vs. impacted sites), (iii) type of contamination (WWTP or UWW), and (iv) location of the sampling sites. Moreover, the higher abundance of five genera of the family Rhodocyclaceae detected in wastewater-impacted sites is also likely to be an effect of effluent discharge. The data presented here complement a broader study (Martínez-Santos et al., 2018) [1] and they are particularly useful for those interested in understanding the impact of wastewater effluents on the abundance, structure and function of river bacterial communities involved in nitrogen cycling. Keywords: Wastewater, River sediment, Nutrients, Metals, Denitrifying genes, Rhodocyclacea

Global carbon sequestration through continental chemical weathering in a climatic change context

This study simulates carbon dioxide (CO2) sequestration in 300 major world river basins (about 70% of global surface area) through carbonates dissolution and silicate hydrolysis. For each river basin, the daily timescale impacts under the RCP 2.6 and RCP 8.5 climate scenarios were assessed relative to a historical baseline (1969–1999) using a cascade of models accounting for the hydrological evolution under climate change scenarios. Here we show that the global temporal evolution of the CO2 uptake presents a general increase in the annual amount of CO2 consumed from 0.247 ± 0.045 Pg C year−1 to 0.261 and 0.273 ± 0.054 Pg C year−1, respectively for RCP 2.6 and RCP 8.5. Despite showing a general increase in the global daily carbon sequestration, both climate scenarios show a decrease between June and August. Such projected changes have been mapped and evaluated against changes in hydrology, identifying hot spots and moments for the annual and seasonal periods

Global carbon sequestration through continental chemical weathering in a climatic change context

This study simulates carbon dioxide (CO2) sequestration in 300 major world river basins (about 70% of global surface area) through carbonates dissolution and silicate hydrolysis. For each river basin, the daily timescale impacts under the RCP 2.6 and RCP 8.5 climate scenarios were assessed relative to a historical baseline (1969–1999) using a cascade of models accounting for the hydrological evolution under climate change scenarios. Here we show that the global temporal evolution of the CO2 uptake presents a general increase in the annual amount of CO2 consumed from 0.247 ± 0.045 Pg C year−1 to 0.261 and 0.273 ± 0.054 Pg C year−1, respectively for RCP 2.6 and RCP 8.5. Despite showing a general increase in the global daily carbon sequestration, both climate scenarios show a decrease between June and August. Such projected changes have been mapped and evaluated against changes in hydrology, identifying hot spots and moments for the annual and seasonal periods

Global carbon sequestration through continental chemical weathering in a climatic change context

International audienceAbstract This study simulates carbon dioxide (CO 2 ) sequestration in 300 major world river basins (about 70% of global surface area) through carbonates dissolution and silicate hydrolysis. For each river basin, the daily timescale impacts under the RCP 2.6 and RCP 8.5 climate scenarios were assessed relative to a historical baseline (1969–1999) using a cascade of models accounting for the hydrological evolution under climate change scenarios. Here we show that the global temporal evolution of the CO 2 uptake presents a general increase in the annual amount of CO 2 consumed from 0.247 ± 0.045 Pg C year −1 to 0.261 and 0.273 ± 0.054 Pg C year −1 , respectively for RCP 2.6 and RCP 8.5. Despite showing a general increase in the global daily carbon sequestration, both climate scenarios show a decrease between June and August. Such projected changes have been mapped and evaluated against changes in hydrology, identifying hot spots and moments for the annual and seasonal periods

Global carbon sequestration through continental chemical weathering in a climatic change context

This study simulates carbon dioxide (CO2) sequestration in 300 major world river basins (about 70% of global surface area) through carbonates dissolution and silicate hydrolysis. For each river basin, the daily timescale impacts under the RCP 2.6 and RCP 8.5 climate scenarios were assessed relative to a historical baseline (1969–1999) using a cascade of models accounting for the hydrological evolution under climate change scenarios. Here we show that the global temporal evolution of the CO2 uptake presents a general increase in the annual amount of CO2 consumed from 0.247 ± 0.045 Pg C year−1 to 0.261 and 0.273 ± 0.054 Pg C year−1, respectively for RCP 2.6 and RCP 8.5. Despite showing a general increase in the global daily carbon sequestration, both climate scenarios show a decrease between June and August. Such projected changes have been mapped and evaluated against changes in hydrology, identifying hot spots and moments for the annual and seasonal periods