SentiNet: Detecting Physical Attacks Against Deep Learning Systems

SentiNet is a novel detection framework for physical attacks on neural networks, a class of attacks that constrains an adversarial region to a visible portion of an image. Physical attacks have been shown to be robust and flexible techniques suited for deployment in real-world scenarios. Unlike most other adversarial detection works, SentiNet does not require training a model or preknowledge of an attack prior to detection. This attack-agnostic approach is appealing due to the large number of possible mechanisms and vectors of attack an attack-specific defense would have to consider. By leveraging the neural network's susceptibility to attacks and by using techniques from model interpretability and object detection as detection mechanisms, SentiNet turns a weakness of a model into a strength. We demonstrate the effectiveness of SentiNet on three different attacks - i.e., adversarial examples, data poisoning attacks, and trojaned networks - that have large variations in deployment mechanisms, and show that our defense is able to achieve very competitive performance metrics for all three threats, even against strong adaptive adversaries with full knowledge of SentiNet.Comment: 15 page

The role of afforestation species as a driver of Hg accumulation in organic horizons of forest soils from a Mediterranean mountain area in SW Europe

Forest areas are a primary sink of atmospheric mercury (Hg) within terrestrial ecosystems, whereas forest vegetation plays a key role in atmospheric Hg transfer to soil horizons. This study assessed variations in total Hg contents (HgT) and accumulation (HgRes) in the soil organic horizons of a forest area in NE Portugal, where post-wildfire afforestation led to the substitution of the native deciduous species (Quercus pyrenaica) by fast-growing coniferous species (Pseudotsuga menziesii and Pinus nigra). The study also evaluated, for each species, the links between Hg contents and other biophilic elements of soil organic matter (C, N, S) present in organic subhorizons (OL, OF, OH). Mean HgT in the organic horizons of the different tree species follow the sequence: P. nigra (88 μg kg−1) < Q. pyrenaica (101 μg kg−1) < P. menziesii (141 μg kg−1). The highest HgRes for the entire organic horizon was found under P. menziesii (471 μg m−2), followed by P. nigra (253 μg m−2) and Q. pyrenaica (189 μg m−2). Among the organic subhorizons, values of HgT and HgRes follow the sequence OL < OF < OH, which is consistent with the degree of organic matter humification. Indeed, HgT and HgRes correlated significantly with the C/N and C/S ratios for all species and organic subhorizons, suggesting that the quality of organic matter may influence strongly the Hg fate in these forest soils. Soils from P. menziesii plots have shown an HgRes 2.5 times higher than in plots dominated by the native Q. pyrenaica. Hg accumulation in the organic horizons, promoted in the coniferous species, may increase the risk of Hg mobilization due to wildfires and forest management practices. Therefore, forest management plans should select cautiously the tree species for afforestation in order to minimize adverse environmental effects caused by changes in the biogeochemical cycle of contaminants such as Hg.M. Méndez-López acknowledges the predoctoral grant FPU of Ministerio de Educación y Formación Profesional (FPU17/05484). It is also recognized the financial support of the Consellería de Cultura, Educación e Universidade (Xunta de Galicia) through the contract ED431C 2021/46-GRC granted to the research group BV1 of the University of Vigo and the research project ED431F2018/06-EXCELENCIA.info:eu-repo/semantics/publishedVersio

Variation of Hg concentration and accumulation in the soil of maritime pine plantations along a coast-inland transect in SW Europe

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGClimatic conditions have been shown as a major driver of the fate of Hg in forest ecosystems at a global scale, but less is known about climatic effects at shorter scales. This study assesses whether the concentration and pools of Hg in soils collected from seventeen Pinus pinaster stands describing a coastal-inland transect in SW Europe vary along a regional climatic gradient. In each stand, samples of the organic subhorizons (OL, OF + OH) and the mineral soil (up to 40 cm) were collected and some general physico-chemical properties and total Hg (THg) were analyzed. Total Hg was significantly higher in the OF + OH than in the OL subhorizons (98 and 38 μg kg−1, respectively), favored by a greater organic matter humification in the former. In the mineral soil, mean THg values decreased with depth, ranging from 96 μg kg−1 in the 0–5 cm layers to 54 μg kg−1 in the deepest layers (30–40 cm), respectively. The average Hg pool (PHg) was 0.30 mg m−2 in the organic horizons (92% accumulated in the OF + OH subhorizons), and 27.4 mg m−2 in the mineral soil. Changes in climatic factors, mainly precipitation, along the coast-inland transect resulted in a remarkable variation of THg in the OL subhorizons, consistent with their role as the first receiver of atmospheric Hg inputs. The high precipitation rate and the occurrence of fogs in coastal areas characterized by the oceanic influence would explain the higher THg found in the uppermost soil layers of pine stands located close to the coastline. The regional climate is key to the fate of mercury in forest ecosystems by influencing the plant growth and subsequent atmospheric Hg uptake, the atmospheric Hg transference to the soil surface (wet and dry deposition and litterfall) and the dynamics that determine net Hg accumulation in the forest floor.Ministerio de Educación y Formación Profesional | Ref. FPU17/05484Ministerio de Ciencia e Innovación | Ref. PID 2021-125114OB-I00Consellería de Cultura, Educación e Universidade (Xunta de Galicia) | Ref. ED431C2021/46- GRCUniversidad de Vigo/CISU

Mercury mobilization in shrubland after a prescribed fire in NE Portugal: insight on soil organic matter composition and different aggregate size

Soils constitute the major reservoir of mercury (Hg) in terrestrial ecosystems, whose stability may be threatened by wildfires. This research attempts to look at the effect of prescribed fire on the presence of Hg in a shrubland ecosystem from NE Portugal, delving into its relationship with soil aggregate size and the molecular composition of soil organic matter (SOM). During the prescribed fire, on average 347 mg Hg ha 1 were lost from the burnt aboveground biomass of shrubs and 263 mg Hg ha 1 from the combustion of the soil organic horizon. Overall, Hg concentration and pools in the mineral soil did not show significant changes due to burning, which highlights their role as long-term Hg reservoirs. The higher Hg concentrations found in smaller aggregates (<0.2 mm) compared to coarser ones (0.5–2 mm) are favored by the higher degree of organic matter decomposition (low C/ N ratio), rather than by greater total organic C contents. The Hg-enriched finest fraction of soil (<0.2 mm) could be more prone to be mobilized by erosion, whose potential arrival to water bodies increases the environmental concern for the Hg present in fire-affected soils. The SOM quality (molecular composition) and the main organic families, analyzed by Fourier-transform infrared spectroscopy in combination with multivariate statisticalThis work was supported by the Interreg V-A Spain-Portugal program (POCTEP) 2014–2020 (Project 0701_TERRAMATER_1_E) funded by the European Regional Development Fund (FEDER), the EROFIRE project (PCIF/RPG/0079/2018) funded by FCT, Portugal and the InMerForEcos project (PID 2021-125114OB-I00) funded by Ministerio de Ciencia e Innovaciónn and Agencia Estatal de Investigaciónn (MCIN/ AEI) and FEDER. M. Méndez-López was supported by the predoctoral grant FPU (FPU17/05484) funded by the Ministerio de Educaciónn y Formación Profesional. N.T. Jiménez-Morillo was supported by a “Ramón y Cajal” contract (RYC2021-031253-I) funded by MCIN/AEI/10 .13039/501100011033 and the European Union “NextGenerationEU”/ PRTR”. The financial support of the Consellería de Cultura, Educación e Universidade (Xunta de Galicia) through the contract ED431C2021/46- GRC granted to the research group BV1 of the University of Vigo is also recognized. Open-access funding for this research has been provided by the University of Vigo/CISUG.info:eu-repo/semantics/publishedVersio

Needle age and precipitation as drivers of Hg accumulation and deposition in coniferous forests from a southwestern European Atlantic region

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGVegetation and climate are critical in the biogeochemical cycle of Hg in forest ecosystems. The study assesses the influence of needle age and precipitation on the accumulation of Hg in needle biomass and its deposition by litterfall in thirty-one pine plantations spread throughout two biogeographical regions in SW Europe. Welldeveloped branches of Pinus pinaster were sampled and pine needles were classified according to 4 age classes (y0, y1, y2, y3). The concentration of total Hg (THg) was analyzed in the samples and Hg content in needle biomass and its deposition by litterfall were estimated. The concentration of total Hg (THg) increased with needle age ranging from 9.1 to 32.7 μg Hg kg−1 in the youngest and oldest needles, respectively. The rate of Hg uptake (HgR) three years after needle sprouting was 10.2 ± 2.3 μg Hg kg−1 yr−1, but it decreased with needle age probably due to a diminution in photosynthetic activity as needles get older. The average total Hg stored in needle biomass (HgWt) ranged from 5.6 to 87.8 mg Hg ha−1, with intermediate needle age classes (y1 and y2) accounting for 70% of the total Hg stored in the whole needle biomass. The average deposition flux of Hg through needle litterfall (HgLt) was 1.5 μg Hg m−2 yr−1, with the y2 and y3 needles contributing most to the total Hg flux. The spatial variation of THg, HgWt and HgLt decreased from coastal pine stands, characterized by an oceanic climate, to inland pine stands, a feature closely related to the dominant precipitation regime in the study area. Climatic conditions and needle age are the main factors affecting Hg accumulation in tree foliage, and should be considered for an accurate assessment of forest Hg pools at a regional scale and their potential consequences in the functioning of terrestrial ecosystems.Ministerio de Educación y Formación Profesional | Ref. FPU17/05484Xunta de Galicia | Ref. ED431C 2021/46-GRCXunta de Galicia | Ref. ED431F2018/06-EXCELENCIAXunta de Galicia | Ref. ED431C2018/0

Mercury in a birch forest in SW Europe: Deposition flux by litterfall and pools in aboveground tree biomass and soils

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGAtmospheric mercury (Hg) is largely assimilated by vegetation and subsequently transferred to the soil by litterfall, which highlights the role of forests as one of the largest global Hg sinks within terrestrial ecosystems. We assessed the pool of Hg in the aboveground biomass (leaves, wood, bark, branches and twigs), the Hg deposition flux through litterfall over two years (by sorting fallen biomass in leaves, twigs, reproductive structures and miscellaneous) and its accumulation in the soil profile in a deciduous forest dominated by Betula alba from SW Europe. The total Hg pool in the aboveground birch biomass was in the range 532–683 mg ha−1, showing the following distribution by plant tissues: well-developed leaves (171 mg ha−1) > twigs (160 mg ha−1) > bark (159 mg ha−1) > bole wood (145 mg ha−1) > fine branches (25 mg ha−1) > thick branches (24 mg ha−1) > newly sprouted leaves (20 mg ha−1). The total Hg deposition fluxes through litterfall were 15.4 and 11.7 μg m−2 yr−1 for the two years studied, with the greatest contribution coming from birch leaves (73 %). In the soil profile, the pool of Hg in the mineral soil (37.0 mg m−2) was an order of magnitude higher than in the organic horizons (1.0 mg m−2), mostly conditioned by parameters such as soil bulk density and thickness, total C andNcontents and the presence of certain Al compounds.Ministerio de Educación y Formación Profesional | Ref. FPU17/05484Xunta de Galicia | Ref. ED431C2021/46-GRCXunta de Galicia | Ref. ED431F2018/06- EXCELENCI

Soil erosion in mountain shrub areas: effect of prescribed fire

Atualmente, um dos maiores problemas ambientais ao nível do globo é a perda de solo por erosão hídrica. O agente erosivo pode provocar perdas significativas de nutrientes e matéria orgânica, principalmente quando a superfície do solo suporta um reduzido coberto vegetal. Em Portugal, o fogo controlado é uma prática comumente utilizada no controlo da disponibilidade de combustível e consequente redução do risco de incêndio. Contudo, esta prática remove em grande parte a cobertura vegetal, deixando o solo mais exposto aos processos erosivos. Neste sentido, o presente trabalho tem como objetivo avaliar o efeito do fogo controlado na erosão hídrica em áreas de matos do Parque Natural de Montesinho, NE Portugal. Após o fogo, foram instaladas 6 parcelas de erosão de 4 m2 cada (4 × 1 m), para avaliação da perda de solo e do escoamento superficial na área queimada. Os resultados englobam 8 meses de ensaio (março a dezembro de 2021), e as colheitas foram realizadas por cada evento de precipitação, perfazendo um total de 6 avaliações. O volume de água de escoamento e a perda de solo (massa de sedimentos) foram obtidos através de cálculos que englobaram o escoamento, os sedimentos transportados para o interior dos reservatórios de colheita do escoamento e os sedimentos depositados na parte frontal das parcelas de erosão (colocação de um dispositivo que permite a recolha dos sedimentos transportados). A quantidade média de perda de solo foi de 15,4 g m-2, o escoamento superficial médio foi de 1,4 mm, traduzindo-se num coeficiente de escoamento de 4,2%. Para avaliação das perdas de C e N, os sedimentos foram separados em 4 classes de tamanho (2mm) e analisadas em laboratórios as concentrações de C e N. A baixa precipitação total, durante o período de ensaio, ocasionou baixos valores de escoamento e, portanto, baixos valores de perda de solo, de C e de NCurrently, one of the biggest environmental problems at the global level is the soil loss by water erosion. The erosive agent can cause significant losses of nutrients and organic matter, especially when the soil surface supports a reduced vegetation cover. In Portugal, prescribed fire is a commonly used practice to control the fuel availability and consequently reduce the wildfires risk. However, this practice removes the vegetation cover, leaving the soil more exposed to erosive processes. In this sense, the present work aims to evaluate the effect of prescribed fire on water erosion in shrub areas of the Montesinho Natural Park, NE Portugal. After the fire, 6 erosion plots of 4 m2 each (4 × 1 m) were installed to assess soil loss and runoff in the burned area. The results encompass 8 months (March to December 2021), and samples were collected for each rainfall event, making a total of 6 evaluations. The runoff and soil loss (sediment mass) were obtained through calculations that encompassed the runoff, the sediments transported into the runoff collection reservoirs and the sediments deposited on the front of the erosion plots (placement of a device that allows the collection of transported sediments). The average of soil loss was 15.4 g m-2, the average of runoff was 1.4 mm, corresponding to a runoff coefficient of 4.2%. To evaluate C and N losses, the sediments were separated into 4 size classes (2mm) and analyzed in laboratory the C and N concentrations. The low total precipitation, during the test period, caused low runoff values and, therefore, low losses of soil, C and N.TERRAMATER- Innovative preventive recovery measures in burnt areas, 0701_TERRAMATER_ 1_E, co-funded by FEDER through Interreg V-A España-Portugal (POCTEP) 2014–2022. Fundação para a Ciência e a Tecnologia (FCT, Portugal) e fundos nacionais FCT/MCTES (PIDDAC) pelo apoio financeiro ao CIMO (UIDB/00690/2020 e UIDP/00690/2020) e SusTEC (LA/P/0007/2020).info:eu-repo/semantics/publishedVersio

Hg levels in the litterfall of nothofagus pumilio (lenga) forests from Tierra del Fuego, Argentina

Se estudió la contribución de la hojarasca en la transferencia de Hg al suelo de tres bosques vírgenes de lenga en Tierra del Fuego (Argentina): Río Olivia (RO), Parque Nacional 1 y 3 (PN1, PN3). El flujo promedio de hojarasca en las zonas de estudio fue de 266 g m-2, siendo mayor en RO y menor en PN3. Las hojas fueron el principal componente de la hojarasca (84%) y, junto con las misceláneas, constituyeron las fracciones con mayor concentración de Hg (20- 31 ng g-1). Debido a su escaso flujo de biomasa (8%), las misceláneas sólo contribuyeron al 7% de la deposición de Hg al suelo, frente al 88% de las hojas. El mayor flujo de deposición de Hg a través de la hojarasca (8±1 μg m-2) se registró en el bosque RO. Los valores hallados son relativamente menores a los encontrados en bosques de otras partes del mundo.Centro de Investigaciones Geológica

Hg levels in the litterfall of nothofagus pumilio (lenga) forests from Tierra del Fuego, Argentina

Se estudió la contribución de la hojarasca en la transferencia de Hg al suelo de tres bosques vírgenes de lenga en Tierra del Fuego (Argentina): Río Olivia (RO), Parque Nacional 1 y 3 (PN1, PN3). El flujo promedio de hojarasca en las zonas de estudio fue de 266 g m-2, siendo mayor en RO y menor en PN3. Las hojas fueron el principal componente de la hojarasca (84%) y, junto con las misceláneas, constituyeron las fracciones con mayor concentración de Hg (20- 31 ng g-1). Debido a su escaso flujo de biomasa (8%), las misceláneas sólo contribuyeron al 7% de la deposición de Hg al suelo, frente al 88% de las hojas. El mayor flujo de deposición de Hg a través de la hojarasca (8±1 μg m-2) se registró en el bosque RO. Los valores hallados son relativamente menores a los encontrados en bosques de otras partes del mundo.Centro de Investigaciones Geológica

Hg levels in the litterfall of nothofagus pumilio (lenga) forests from Tierra del Fuego, Argentina

Se estudió la contribución de la hojarasca en la transferencia de Hg al suelo de tres bosques vírgenes de lenga en Tierra del Fuego (Argentina): Río Olivia (RO), Parque Nacional 1 y 3 (PN1, PN3). El flujo promedio de hojarasca en las zonas de estudio fue de 266 g m-2, siendo mayor en RO y menor en PN3. Las hojas fueron el principal componente de la hojarasca (84%) y, junto con las misceláneas, constituyeron las fracciones con mayor concentración de Hg (20- 31 ng g-1). Debido a su escaso flujo de biomasa (8%), las misceláneas sólo contribuyeron al 7% de la deposición de Hg al suelo, frente al 88% de las hojas. El mayor flujo de deposición de Hg a través de la hojarasca (8±1 μg m-2) se registró en el bosque RO. Los valores hallados son relativamente menores a los encontrados en bosques de otras partes del mundo.Centro de Investigaciones Geológica