Development of a heavy metal sensing boat for automatic analysis in natural waters utilizing anodic stripping voltammetry

Altres ajuts: CERCA Programme/Generalitat de CatalunyaDetermination of the levels of heavy metal ions would support assessment of sources and pathways of water pollution. However, traditional spatial assessment by manual sampling and off-site detection in the laboratory is expensive and time-consuming and requires trained personnel. Aiming to fill the gap between on-site automatic approaches and laboratory techniques, we developed an autonomous sensing boat for on-site heavy metal detection using square-wave anodic stripping voltammetry. A fluidic sensing system was developed to integrate into the boat as the critical sensing component and could detect ≤1 μg/L Pb, ≤6 μg/L Cu, and ≤71 μg/L Cd simultaneously in the laboratory. Once its integration was completed, the autonomous sensing boat was tested in the field, demonstrating its ability to distinguish the highest concentration of Pb in an effluent of a galena-enriched mine compared to those at other sites in the stream (Osor Stream, Girona, Spain)

Earthworm-mycorrhiza interactions can affect the diversity, structure and functioning of establishing model grassland communities.

Both earthworms and arbuscular mycorrhizal fungi (AMF) are important ecosystem engineers co-occurring in temperate grasslands. However, their combined impacts during grassland establishment are poorly understood and have never been studied. We used large mesocosms to study the effects of different functional groups of earthworms (i.e., vertically burrowing anecics vs. horizontally burrowing endogeics) and a mix of four AMF taxa on the establishment, diversity and productivity of plant communities after a simulated seed rain of 18 grassland species comprising grasses, non-leguminous forbs and legumes. Moreover, effects of earthworms and/or AMF on water infiltration and leaching of ammonium, nitrate and phosphate were determined after a simulated extreme rainfall event (40 l m(-2)). AMF colonisation of all three plant functional groups was altered by earthworms. Seedling emergence and diversity was reduced by anecic earthworms, however only when AMF were present. Plant density was decreased in AMF-free mesocosms when both anecic and endogeic earthworms were active; with AMF also anecics reduced plant density. Plant shoot and root biomass was only affected by earthworms in AMF-free mesocosms: shoot biomass increased due to the activity of either anecics or endogeics; root biomass increased only when anecics were active. Water infiltration increased when earthworms were present in the mesocosms but remained unaffected by AMF. Ammonium leaching was increased only when anecics or a mixed earthworm community was active but was unaffected by AMF; nitrate and phosphate leaching was neither affected by earthworms nor AMF. Ammonium leaching decreased with increasing plant density, nitrate leaching decreased with increasing plant diversity and density. In order to understand the underlying processes of these interactions further investigations possibly under field conditions using more diverse belowground communities are required. Nevertheless, this study demonstrates that belowground-aboveground linkages involving earthworms and AMF are important mediators of the diversity, structure and functioning of plant communities

An innovative autonomous robotic system for on-site detection of heavy metal pollution plumes in surface water

Smart monitoring has been studied and developed in recent years to create faster, cheaper, and more user-friendly on-site methods. The present study describes an innovative technology for investigative monitoring of heavy metal pollution (Cu and Pb) in surface water. It is composed of an autonomous surface vehicle capable of semiautonomous driving and equipped with a microfluidic device for detection of heavy metals. Detection is based on the method of square wave anodic stripping voltammetry using carbon-based screen-printed electrodes (SPEs). The focus of this work was to validate the ability of the integrated system to perform on-site detection of heavy metal pollution plumes in river catchments. This scenario was simulated in laboratory experiments. The main performance characteristics of the system, which was evaluated based on ISO 15839 were measurement bias (Pb 75%, Cu 65%), reproducibility (in terms of relative standard deviation: Pb 11-18%, Cu 6-10%) and the limit of detection (4 µg/L for Pb and 7 µg/L for Cu). The lowest detectable change (LDC), which is an important performance characteristic for this application, was estimated to be 4-5 µg/L for Pb and 6-7 µg/L for Cu. The life span of an SPE averaged 39 measurements per day, which is considered sufficient for intended monitoring campaigns. This work demonstrated the suitability of the integrated system for on-site detection of Pb and Cu emissions from large and medium urban areas discharging into small water bodies

Species diversity of legumes, grasses and forbs in mescocosms containing different earthworm species (NoEw…no earthworms, Ac…<i>A. caliginosa</i>, Lt…<i>L. terrestris</i>, AcLt…both species) with and without AMF inoculation.

<p>Lower case letters denote differences between earthworm treatments within each plant functional group and AMF treatment; upper case letters denote differences between total plant species diversity (P<0.05). Means, n = 5.</p

Seedling establishment in mesocosms containing different combinations of earthworm species (NoEw…no earthworms, Ac…<i>A. caliginosa</i>, Lt…<i>L. terrestris</i>, AcLt…both species) without or with AMF inoculation.

<p>P-Values from repeated measurement ANOVAs, different letters denote significant differences at the end of the measurement period (Tukey, P<0.05). Means, n = 5.</p

Biomass production of legumes, grasses and forbs in mescocosms containing different earthworm species (NoEw…no earthworms, Ac…<i>A. caliginosa</i>, Lt…<i>L. terrestris</i>, AcLt…both species) with and without AMF inoculation.

<p>Lower case letters denote differences between earthworm treatments within each plant functional group and AMF treatment; upper case letters denote differences between total plant biomass (P<0.05). Means, n = 5.</p

Density of legumes, grasses and forbs in mescocosms containing different earthworm species (NoEw…no earthworms, Ac…<i>A. caliginosa</i>, Lt…<i>L. terrestris</i>, AcLt…both species) with and without AMF inoculation.

<p>Lower case letters represent differences between earthworm treatments within each plant functional group and AMF treatment; upper case letters denote differences between total plant density (P<0.05). Means, n = 5.</p

Percent root length colonized by AMF of legumes, grasses and non-leguminous forbs in mescocosms containing different earthworm species (NoEw…no earthworms, Ac…only <i>A. caliginosa</i>, Lt…only <i>L. terrestris</i>, AcLt…both species).

<p>Only data from mesocosms inoculated with AMF are shown. Different letters within each row represent significant differences (P<0.05; Tukey-test with sequential Bonferroni correction) between earthworm treatments. Means ± SE, n = 5.</p