Effects of the 2021 La Palma volcanic eruption on groundwater hydrochemistry: Geochemical modelling of endogenous CO2 release to surface reservoirs, water-rock interaction and influence of thermal and seawater

Volcanic islands face unique challenges in protecting and managing their water resources due to their small size, limited freshwater availability, and vulnerability to natural hazards. The recent 2021 eruption of the Tajogaite volcano on La Palma Island in the Canary Islands, Spain, raised concerns regarding the potential impact on groundwater hydrochemistry. This work aimed to characterize and model the processes that lead to the measured hydrochemical impacts in the groundwater of La Palma as a consequence of the volcanic eruption. The study involved conducting three groundwater sampling campaigns during the eruption, and six after the eruption ceased. A total of 15 monitored points, including piezometers, wells, water galleries, and the main gully collector of the island, all relatively close (2 to15 km) to the erupted volcano, were sampled for the analysis of major solutes and SiO2. Unpublished hydrochemical data previous to the eruption were provided by the local water management authorities of La Palma (CIALP) and the Geological Survey of Spain (IGME). Statistical analyses were performed to assess the differences in groundwater composition before, during, and after the eruption, and a Principal Component Analysis (PCA) mixing model was calculated. Three compositional extreme waters were defined as end members in the system: (1) a high SiO2 computed thermal end member; (2) a low salinity computed fresh groundwater; (3) and seawater. The results of the mixing model showed two main events of maximum mixing ratios in the fresh groundwater reservoirs of La Palma after the eruption; the first one of seawater in July 2022, and the next one of thermal fluids in December 2022. This water mixing during and after the eruption, together with a volcanic CO2 input to the reservoirs, led to significant increases in the concentrations of Na, Ca, SiO2 and SO4 in fresh groundwater, as well as a drop in pH. The significance of these findings relies in improving our understanding of the effects of volcanic eruptions on groundwater, emphasizing the necessity for frequent monitoring and evaluation, given the scarcity and vulnerability of groundwater resources in volcanic islands.

Volcanic tephra deposition dataset based on interpolated field measurements following the 2021 Tajogaite Eruption on La Palma, Canary Islands, Spain

In 2021, the Tajogaite Volcano erupted along the western slope of the Cumbre Vieja on the island of La Palma, Canary Islands, Spain. Volcanic tephra blanketed a substantial proportion of the island. By our estimations, approximately 23,000,000 m3 of pyroclastic ashes and more coarse-grained particles were deposited unto La Palma's land surface in addition to the lava flow. Five months following the initial eruption, we measured the depth of the new ash layer across the island. We combined this data with drone-based observations to compile a dataset comprising the point distribution of ash depth. A spatial interpolation was then performed using Inverse Distance Weighting (IDW) to estimate the ash depth across the island at a 2 m spatial resolution. The interpolation performed well, yielding a root mean squared error (RMSE) value of 0.34 and thus, the dataset offers immense reuse potential for spatial inquiries related to evolutionary traits, vegetation patterns, and vegetation response to disturbance on oceanic islands. In addition, the data can be used to test different spatial interpolation techniques in an effort to improve the accuracy achieved using IDW.

Modeling landslide activity and sediment connectivity after eruptions: Insights from the Blanco River (Chile)

Volcanic eruptions can disrupt entire river basins by affecting the hydro-geomorphic characteristics of channel networks and hillslopes. Reports suggest a pulsed and delayed increase in landslide activity following the eruptions, which, depending on the degree of linkage between hillslopes and channels, i.e. sediment connectivity, can represent a massive source of sediment input for the fluvial system. Therefore, predicting landslide occurrence and sediment connectivity is fundamental for management risk strategies, especially in such dynamic and complex environments. The aim of this work is to develop and offer a more reliable approach to map the areas susceptible to landslides and connected to the active channel in a catchment impacted by volcanic eruption. The analyses were carried out in the Blanco River catchment in southern Chile, affected by the Chaitén eruption (2008-09). A combined approach is presented, based on landslide susceptibility models, carried out multi-temporally (from 2010 to 2019), and a threshold-based sediment connectivity map. The results showed that the highest landslide occurrence was reported 4 years after the eruption, whereas the faster increase in the overall area affected was observed only after 7 years. Landslide susceptibility models showed high accuracy when applied in the same year, but were less accurate in predicting future occurrences. This result is ascribed to the dynamic conditions of the vegetation, regenerating quickly after the mass movements. Nevertheless, considering the potential sources of error, the combined landslide susceptibility-connectivity map for the year 2019 well-identified relevant areas for catchment management. The largest part of the catchment was found non-susceptible and disconnected, while areas classified as susceptible and connected represent only 3.1 %. The application of this novel approach allowed to unravel the geomorphic trajectory of the study area and, more importantly, can represent a benchmark for future applications in other catchments affected by large disturbances.

Impact of the 2021 La Palma volcanic eruption on air quality: Insights from a multidisciplinary approach

The La Palma 2021 volcanic eruption was the first subaerial eruption in a 50-year period in the Canary Islands (Spain), emitting ~1.8 Tg of sulphur dioxide (SO₂) into the troposphere over nearly 3 months (19 September-13 December 2021), exceeding the total anthropogenic SO₂ emitted from the 27 European Union countries in 2019. We conducted a comprehensive evaluation of the impact of the 2021 volcanic eruption on air quality (SO₂, PM₁₀ and PM_2.5 concentrations) utilising a multidisciplinary approach, combining ground and satellite-based measurements with height-resolved aerosol and meteorological information. High concentrations of SO₂, PM₁₀ and PM_2.5 were observed in La Palma (hourly mean SO₂ up to ~2600 μg m^-3 and also sporadically at ~140 km distance on the island of Tenerife (> 7700 μg m^-3) in the free troposphere. PM₁₀ and PM_2.5 daily mean concentrations in La Palma peaked at ~380 and 60 μg m^-3. Volcanic aerosols and desert dust both impacted the lower troposphere in a similar height range (~ 0-6 km) during the eruption, providing a unique opportunity to study the combined effect of both natural phenomena. The impact of the 2021 volcanic eruption on SO₂ and PM concentrations was strongly influenced by the magnitude of the volcanic emissions, the injection height, the vertical stratification of the atmosphere and its seasonal dynamics. Mean daily SO₂ concentrations increased during the eruption, from 38 μg m^-3 (Phase I) to 92 μg m^-3 (Phase II), showing an opposite temporal trend to mean daily SO₂ emissions, which decreased from 34 kt (Phase I) to 7 kt (Phase II). The results of this study are relevant for emergency preparedness in all international areas at risk of volcanic eruptions; a multidisciplinary approach is key to understand the processes by which volcanic eruptions affect air quality and to mitigate and minimise impacts on the population.

The ASHES study protocol

INTRODUCTION

Volcanic eruptions emit gases and particulate matter into the atmosphere which, if inhaled, can have an impact on health. The eruption of the volcano situated in the Cumbre Vieja Nature Reserve (La Palma, Canary Islands, Spain) affords a unique opportunity to study the effect of such a phenomenon on health. The aim of the proposed study is to assess the short-, medium- and long-term respiratory health effects of exposure to volcanic emissions from the eruption in three different population groups.

METHODS

We propose to undertake a multidesign study: an ambispective cohort study to analyze the effect of the eruption on the general population, the highly exposed population, and the childhood population; and a pre-post quasi-experimental study on subjects with previously diagnosed respiratory diseases. The information will be collected using a personal interview, biologic specimens, air pollution data, data from medical records, respiratory tests and imaging tests. The study has an envisaged follow-up of five years, to run from the date of initial recruitment, with annual data-collection. This study has been approved by the Santa Cruz de Tenerife Provincial Research Ethics Committee (Canary Island Health Service) on March 10, 2022.

CONCLUSIONS

This study will make it possible to advance our knowledge of the effect a volcano eruption has on population health, both short- and long-term, and to assess the potential respiratory injury attributable to volcanic eruptions. It may serve as a model for future studies of new volcanic eruptions in the coming years.

Measuring air pollution from the 2021 Canary Islands volcanic eruption

The eruption of the Cumbre Vieja volcano on the island of La Palma (Canary Islands, Spain) began on September 19, 2021 and ended on December 13, 2021. It lasted continuously for 85 days with short periods of calm when lava did not exit the cone of the volcano. Vast amounts of volcanic material, including ash and gases, were emitted into the environment. This research focuses on these emissions. The main objective is to use available open-source data to examine the impact on regional and local air quality. Data from the following sources were used: 1) Copernicus Atmosphere Monitoring Service (CAMS) data was used to track the transfer of volcanic SO₂ in the troposphere in early October over long distances from the source of the eruption, including Western and Eastern Europe, across the Atlantic Ocean and the Caribbean; 2) Data from ground monitoring stations measured the concentrations of SO₂ and PM₁₀ near the source; 3) AErosol RObotic NETwork (AERONET) data from the La Palma station that showed high Aerosol Optical Depth (AOD) values (over 0.4) during the active phase of emissions on September 24 and 28, as well as on October 3; 4) Ångström Exponent (AE) values indicated the presence of particles of different sizes. On September 24, high AE values (>1.5), showed the presence of fine-mode fraction scattering aerosols such as sulfates; 5) Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data additionally confirmed the presence of sulfate and dust aerosols in the atmosphere over the region. However, the influence of Saharan dust on the atmosphere of the entire region could not be excluded. This research helps forecast air pollution resulting from large-scale volcanic eruptions and associated health risks to humans.

Water quality monitoring with Sentinel-2 and Landsat-8 satellites during the 2021 volcanic eruption in La Palma (Canary Islands)

In this study, seawater quality was monitored with high-resolution satellite imagery during the 2021 volcanic eruption (September-December) on La Palma Island (Spain), the longest recorded in the history of the island, and the most destructive in the last century in Europe. The Sentinel-2A/B twin satellites and Landsat-8 satellite were jointly used as an optical constellation, which allowed us to successfully characterize the short- and medium-term evolution of the new lava delta and subsequent impact on the seawater. Robust atmospheric and sunglint correction approaches were applied to thoroughly quantify the environmental changes caused on the adjacent coastal waters. The cloud and volcanic ash coverage remained very high over the coast during the event, so restricted information with 14 images (45% of the total scenes) was retrieved from the multi-sensor approach. Nevertheless, the availability of pre-, syn-, and post-eruption satellite products allowed us to map and detect the main water quality variations in the marine environment. On the one hand, during the eruption, a change in the properties of the water quality was observed, with a markedly increased turbidity on the western side of the island near the new lava delta due to the deposition of volcanic ash and material. On the other hand, chlorophyll-a concentration did not significantly increase, algal blooms were not observed, and oligotrophic conditions were not swiftly altered towards eutrophic conditions. This information offered an excellent opportunity to characterize the emplacement of the new lava delta and its impact on the marine environment in La Palma. The present multi-sensor strategy is an excellent opportunity to highlight the potential of remote sensing technology as a relevant and powerful tool for future hazard monitoring and assessment during catastrophes and for a better interpretation of their impact on the marine environment.

Long-term responses of macroinvertebrate assemblages to the 2011 eruption of the Puyehue-Cordón Caulle volcanic complex, Chile

In June 2011 the Puyehue-Cordón Caulle volcanic complex (PCCVC) erupted, ejecting around 950 million metric tons of volcanic ash and pyroclastic rock, generating habitat destruction, environmental deterioration and devastation of ecological communities in rivers near the volcanic fissure. We evaluate the long-term effect of this eruptive event on the recovery of the diversity of aquatic macroinvertebrates, collecting biological and environmental information from 2011 to 2018 in visibly impacted Chilean rivers (Gol-Gol and Nilahue) and not visibly impacted rivers (Calcurrupe and Chanleufu). With the macroinvertebrate records we developed a recovery coefficient based on their diversity before and after the eruption. The results show that before the eruption (2009-2010), the accumulated family richness and mean diversity in the Gol-Gol River were higher than that observed post-eruption in rivers visibly impacted and not visibly impacted. Between 2013 and 2018, 17 families recolonized the Gol-Gol River, as well as 10 new families that were not recorded before the eruption. The richness of families post-eruption was negatively related to the increase in the concentration of total suspended solids, affecting the successional changes and recovery in the medium term. The recovery coefficient indicates that seven years after the eruption the diversity of macroinvertebrates still shows lower levels than those recorded before the eruptive event, with predominance of a slow recovery phase. Families of orders Ephemeroptera, Plecoptera and Trichoptera that were dominant before the eruption of the PCCVC began to recover the richness of taxa two years later, Plecoptera reaching 50% recolonization in 2018, Ephemeroptera 33.3% and Trichoptera 30%. In contrast, Diptera reached 100% recovery by 2018 and chironomids increased since 2015, becoming the dominant taxon during intermediate recovery in the Gol-Gol River. The recovery of macroinvertebrates in the Gol-Gol River is related to their modes of dispersal, feeding and the decrease in ash concentration.

Burn lessons learned from the Whakaari White Island volcanic eruption

New Zealand's most active volcano, Whakaari White Island was a common tourist attraction prior to its eruption on 9 th December 2019. At the time of the eruption, there were 47 people on the island from three tour groups. 39 people survived the initial eruption and were extracted. 31 entered into the New Zealand National Burn Service across four hospitals. The median age of the patients treated at the National Burn Centre was 45.5 years (range: 14 - 67 years) and median total body surface area burn was 49.5% (range: 9% - 90%). The three month survival of this eruptive event was 55%, which subsequently fell to an overall rate of 53% following one late death of an early survivor after repatriation home. Of the patients who survived the initial eruption for long enough to be admitted to the National Burn Service, the overall survival rate was 71% at three months. We describe 12 lessons we have learnt from our management of the survivors. The key surgical lessons among these are: The injuring mechanism combined ballistic trauma, thermal and acidic burn components, with the acid component being the most problematic and urgent for management. Volcanic ash burns result in on-going burn depth progression, deep underlying tissue damage and significant metabolic instability. Early skin grafting was not successful in many cases. Reconstructive strategy needed adjusting to cope with the high operative demand and limited donor sites in all patients. Protect yourself from potential dangers with additional personal protective equipment (PPE) in an unfamiliar setting.

The role of parameters in Bayesian Online Changepoint Detection: detecting early warning of mount Merapi eruptions

Indonesia is a country that is surrounded by active volcanoes, which may erupt at any time; therefore, an online early warning system of volcanic eruption is crucial. In this paper, an online early warning system is constructed based on the changepoints detection on earthquake magnitude time series. This online early warning system is built using a Bayesian Online Changepoint Detection (BOCPD) method. One of the method's advantages is that one can customize the parameters (initial hyper-parameters and hazard-rate parameter) of BOCPD to follow a chosen constraint. These parameters determine the time and number of changepoints. An algorithm, called Appropriate Parameters of Bayesian Online Changepoint Detection for Early Warning (APBOCPD-EW), is proposed to get the parameters that lead the detection to the early warning points before eruption. We apply the algorithm for online early warning of mount Merapi eruptions. The results show that the proposed method produces parameters that give good estimation time for early warnings of mount Merapi's eruptions.

Severe volcanic SO2 exposure and respiratory morbidity in the Icelandic population - a register study

BACKGROUND

The Holuhraun volcanic eruption September 2014 to February 2015 emitted large amounts of sulfur dioxide (SO₂). The aim of this study was to determine the association between volcanic SO₂ gases on general population respiratory health some 250 km from the eruption site, in the Icelandic capital area.

METHODS

Respiratory health outcomes were: asthma medication dispensing (AMD) from the Icelandic Medicines Register, medical doctor consultations in primary care (PCMD) and hospital emergency department visits (HED) in Reykjavík (population: 215000) for respiratory disease from 1 January 2010 to 31 December 2014. The associations between daily counts of health events and daily mean SO₂ concentration and high SO₂ levels (24-h mean SO₂ > 125 μg/m3) were analysed using generalized additive models.

RESULTS

After the eruption began, AMD was higher than before (129.4 vs. 158.4 individuals per day, p < 0.05). For PCMD and HED, there were no significant differences between the number of daily events before and after the eruption (142.2 vs 144.8 and 18.3 vs 17.5, respectively). In regression analysis adjusted for other pollutants, SO₂ was associated with estimated increases in AMD by 0.99% (95% CI 0.39-1.58%) per 10 μg/m³ at lag 0-2, in PCMD for respiratory causes 1.26% (95% CI 0.72-1.80%) per 10 μg/m³ SO₂ at lag 0-2, and in HED by 1.02% (95% CI 0.02-2.03%) per 10 μg/m³ SO₂ at lag 0-2. For days over the health limit, the estimated increases were 10.9% (95% CI 2.1-19.6%), 17.2% (95% CI 10.0-24.4%) for AMD and PCMD. Dispensing of short-acting medication increased significantly by 1.09% (95% CI 0.49-1.70%), and PCMD for respiratory infections and asthma and COPD diagnoses and increased significantly by 1.12% (95% CI 0.54-1.71%) and 2.08% (1.13-3.04%).

CONCLUSION

High levels of volcanic SO₂ are associated with increases in dispensing of AMD, and health care utilization in primary and tertiary care. Individuals with prevalent respiratory disease may be particularly susceptible.

Comparison of Predictive Model of Care Requirements for Burns Patients with Operative Requirements Following Volcanic Burns

On December 9th 2019, Whakaari / White Island volcano in New Zealand erupted with 47 people on the island. 31 people survived long enough to enter the New Zealand National Burn network - 13 were repatriated to Australia within 72 hours and 14 of the remaining 18 were treated at the National Burn Centre at Middlemore Hospital in Auckland. Our department has previously published a model to calculate the total operative requirements for any given burn surface area for the first four weeks of burn treatment. From this model we calculated the predicted surgical time and operative visit requirements for each patient and compared this to their actual requirements. Actual requirements were also recorded beyond four weeks until discharge. Results show average variance for operative minutes was significantly above predicted with both the full thickness burn model (average variance 3.24) and the electrical burn model (average variance 2.65). There was a wide range in both cases (0.54 to 6.17 and 0.44 to 5.06 respectively). There was less variance from predicted values of operative visits required than operative minutes (mean: 1.58; range 0.9 - 3.02). Overall, the values for patients with smaller burns showed the greatest variability from predictions with regards to the total number of operative visits over the first four weeks of care. Additionally, patients with burn sizes greater than 50% TBSA required significant theatre access beyond four weeks. Analysis of these findings will assist with future planning in both disaster and non-disaster settings in the provision of burn care.

[Metal content and trace elements in groundwater supply of the island of El Hierro (Canary Islands, Spain).]

OBJECTIVE

Volcanic eruptions are a natural source of substances potentially dangerous to human health. The island of El Hierro (Canary Islands, Spain) suffered a marine volcanic eruption in 2012, making it necessary to monitor the levels of certain elements that can alter the quality of groundwater supply. The objective of this work was to determine the content of metals and trace elements in the groundwater supply of the Isla del Hierro and to check if they met the quality parameters established in Spanish legislation.

METHODS

The content of metals and trace elements (aluminum, lead, cadmium, calcium, potassium, sodium, magnesium, boron, barium, cobalt, chromium, copper, iron, lithium, manganese, molybdenum, nickel, strontium, vanadium, zinc, fluorine) in a total of 60 samples of groundwater supply and agriculture from six different sampling points on the island. The determination was carried out by inductively coupled plasma optical emission spectrophotometry (ICP-OES) and by fluoride ion selective potentiometry. The data were statistically analyzed applying the Kolmogorov-Smirnov test, Levene's statistic, Kruskal-Wallis, Mann-Whitney U, ANOVA and Tukey's test. Significant differences were those that met p<0.05.

RESULTS

The highest mean concentration of lead was recorded in the Tigaday samples (0.003±0.0005 mg/L), finding statistically significant differences (p<0.05) in the lead levels between the sampling points. The elements analyzed were below the parametric values set in Royal Decree 140/2003.

CONCLUSIONS

The results obtained reflect that, in all the samples analyzed, the quality parameters established in the Spanish legislation (RD 140/2003) are met, being, therefore, waters suitable for human consumption.

Modeling the role of marine protected areas on the recovery of shallow rocky reef ecosystem after a catastrophic submarine volcanic eruption

Modeling is a useful approach to learn about the capacity of the systems to recover after disturbances. In October 2011, a submarine volcanic eruption in The Punta Restinga-Mar de Las Calmas Marine Protected Area (RMC-MPA) caused catastrophic mass mortality. We modeled the recovery dynamics of the fully protected (no-take zone), partially protected (buffer zone), and unprotected (fished zone) areas to evaluate their resilience and their potential to restore fishing resources. Recovery varied with species and levels of protection. Benthic macroalgae and parrotfish populations recovered the fastest. Piscivore fishes, macroinvertebrate feeders, and macroinvertebrate detritivores required more extended recovery periods. The levels of protection played a significant role in recovery, with the no-take zone showing more resilience than the buffer and fished zones. Our results suggest that no-take zones are crucial in the recovery process after catastrophic events. Regular monitoring of benthic communities provided the necessary data to model these communities and to point to the regulation of the artisanal fleet activity in restricted fishing areas as a mechanism to further enhance the recovery of fishing stocks.

Diatom ecological response to deposition of the 833-850 CE White River Ash (east lobe) ashfall in a small subarctic Canadian lake

A <5 mm thick volcanic ashfall layer associated with the White River Ash (east lobe [WRAe]) originating from the eruption of Mount Churchill, Alaska (833-850 CE; 1,117-1,100 cal BP) was observed in two freeze cores obtained from Pocket Lake (62.5090°N, -114.3719°W), a small subarctic lake located within the city limits of Yellowknife, Northwest Territories, Canada. Here we analyze changes in diatom assemblages to assess impact of tephra deposition on the aquatic biota of a subarctic lake. In a well-dated core constrained by 8 radiocarbon dates, diatom counts were carried out at 1-mm intervals through an interval spanning  1 cm above and below the tephra layer with each 1 mm sub-sample represented about 2 years of deposition. Non-metric Multidimensional Scaling (NMDS) and Stratigraphically Constrained Incremental Sum of Squares (CONISS) analyses were carried out and three distinct diatom assemblages were identified throughout the interval. The lowermost "Pre-WRAe Assemblage (Pre-WRAeA)" was indicative of slightly acidic and eutrophic lacustrine conditions. Winter deposition of the tephra layer drove a subsequent diatom flora shift to the "WRAe Assemblage (WRAeA)" the following spring. The WRAeA contained elevated abundances of taxa associated with oligotrophic, nutrient depleted and slightly more alkaline lake waters. These changes were only apparent in samples within the WRAe containing interval indicating that they were short lived and only sustained for a single year of deposition. Immediately above the WRAe horizon, a third, "Post-WRAe Assemblage (Post-WRAeA)" was observed. This assemblage was initially similar to that of the Pre-WRAeA but gradually became more distinct upwards, likely due to climatic patterns independent of the WRAe event. These results suggest that lacustrine environments are sensitive to perturbations such as deposition of ash fall, but that ecological communities in subarctic systems can also have high resilience and can recover rapidly. If subsampling of the freeze cores was carried out at a more standard resolution (0.5-1 cm) these subtle diatom ecological responses to perturbation associated with the WRAe depositional event would not have been observed. This research illustrates the importance of high-resolution subsampling when studying the environmental impact of geologically "near instantaneous" events such as episodic deposition of ashfalls.

Sunshine duration reconstruction in the southeastern Tibetan Plateau based on tree-ring width and its relationship to volcanic eruptions

Sunshine is as essential as temperature and precipitation for tree growth, but sunshine duration reconstructions based on tree rings have not yet been conducted in China. In this study, we presented a 497-year sunshine duration reconstruction for the southeastern Tibetan Plateau using a width chronology of Abies forrestii from the central Hengduan Mountains. The reconstruction accounted for 53.5% of the variance in the observed sunshine during the period of 1961-2013 based on a stable and reliable linear regression. This reconstructed sunshine duration contained six sunny periods (1630-1656, 1665-1697, 1731-1781, 1793-1836, 1862-1895 and 1910-1992) and seven cloudy periods (1522-1629, 1657-1664, 1698-1730, 1782-1792, 1837-1861, 1896-1909 and 1993-2008) at a low-frequency scale. There was an increasing trend from the 16th century to the late 18th and early 19th centuries and a decreasing trend from the mid-19th to the early 21st centuries. Sunshine displayed inverse patterns to the local Palmer drought severity index on a multidecadal scale, indicating that this region likely experienced droughts under more sunshine conditions. The decrease in sunshine particularly in recent decades was mainly due to increasing atmospheric anthropogenic aerosols. In terms of the interannual variations in sunshine, weak sunshine years matched well with years of major volcanic eruptions. The significant cycles of the 2- to 7-year, 20.0-year and 35.2-year durations as well as the 60.2-year and 78.7-year durations related to the El-Niño Southern Oscillation, the Pacific Decadal Oscillation and the Atlantic Multidecadal Oscillation suggested that the variation in sunshine duration in the southeastern Tibetan Plateau was possibly affected by large-scale ocean-atmosphere circulations.

Temperature reconstruction and volcanic eruption signal from tree-ring width and maximum latewood density over the past 304 years in the southeastern Tibetan Plateau

This study presents a 304-year mean July-October maximum temperature reconstruction for the southeastern Tibetan Plateau based on both tree-ring width and maximum latewood density data. The reconstruction explained 58% of the variance in July-October maximum temperature during the calibration period (1958-2005). On the decadal scale, we identified two prominent cold periods during AD 1801-1833 and 1961-2003 and two prominent warm periods during AD 1730-1800 and 1928-1960, which are consistent with other reconstructions from the nearby region. Based on the reconstructed temperature series and volcanic eruption chronology, we found that most extreme cold years were in good agreement with major volcanic eruptions, such as 1816 after the Tambora eruption in 1815. Also, clusters of volcanic eruptions probably made the 1810s the coldest decade in the past 300 years. Our results indicated that fingerprints of major volcanic eruptions can be found in the reconstructed temperature records, while the responses of regional climate to these eruption events varied in space and time in the southeastern Tibetan Plateau.

Characteristics of pristine volcanic materials: Beneficial and harmful effects and their management for restoration of agroecosystem

Eruption of Sinabung volcano in Indonesia began again in 2010 after resting for 1200 years. The volcano is daily emitting ash and pyroclastic materials since September 2013 to the present, damaging agroecosystems and costing for management restoration. The objective of the study was to assess properties and impacts of pristine volcanic material depositions on soil properties and to provide management options for restoring the affected agroecosytem. Land satellite imagery was used for field studies to observe the distribution, thickness and properties of ashfall deposition. The pristine ashfall deposits and the underlying soils were sampled for mineralogical, soluble salt, chemical, physical and toxic compound analyses. Results showed that uneven distribution of rainfall at the time of violent eruption caused the areas receiving mud ashfall developed surface encrustation, which was not occur in areas receiving dry ashfall. Ashfall damaged the agroecosytem by burning vegetation, forming surface crusts, and creating soil acidity and toxicity. X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses of encrustated layer indicated the presence of gypsum and jarosite minerals. Gypsum likely acted as a cementing agent in the formation of the encrustation layer with extremely low pH (2.9) and extremely high concentrations of Al, Ca and S. Encrustation is responsible for limited water infiltration and root penetration, while the extremely high concentration of Al is responsible for crop toxicity. Mud ashfall and dry ashfall deposits also greatly changed the underlying soil properties by decreasing soil pH and cation exchange capacity and by increasing exchangeable Ca, Al, and S availability. Despite damaging vegetation in the short-term, the volcanic ashfall enriched the soil in the longer term by adding nutrients like Ca, Mg, K, Na, P, Si and S. Suggested management practices to help restore the agroecosystem after volcanic eruptions include: (i) the application of lime to increase soil pH, increase cation exchange capacity and decrease Al and S toxicities, (ii) the selection of crops which are tolerant to low pH and high concentrations of soluble Al and S, (iii) physically disrupting the hard surface crusts that form on some soils (if <2 cm thick) to allow water infiltration and root penetration, (iv) application of N and K fertilizers, and (v) incorporation of dry ashfall into the soil (if <5 cm thick) to exploit the newly deposited nutrients.

Rising from the ashes: Changes in salmonid fish assemblages after 30 months of the Puyehue-Cordon Caulle volcanic eruption

Events such as volcanic eruptions may act as disturbance agents modifying the landscape spatial diversity and increasing environmental instability. On June 4, 2011 the Puyehue-Cordon Caulle volcanic complex located on Chile (2236 m.a.s.l., 40° 02' 24" S- 70° 14' 26" W) experience a rift zone eruption ejecting during the first day 950 million metric tons into the atmosphere. Due to the westerly winds predominance, ash fell differentially upon 24 million ha of Patagonia Argentinean, been thicker deposits accumulated towards the West. In order to analyze changes on stream fish assemblages we studied seven streams 8, 19 and 30 months after the eruption along the ash deposition gradient, and compare those data to pre eruption ones. Habitat features and structure of the benthic macroinvertebrate food base of fish was studied. After the eruption, substantial environmental changes were observed in association with the large amount of ash fallout. In western sites, habitat loss due to ash accumulation, changes in the riparian zone and morphology of the main channels were observed. Turbidity was the water quality variable which reflected the most changes throughout time, with NTU values decreasing sharply from West to East sites. In west sites, increased Chironomid densities were recorded 8 months after the initial eruption as well as low EPT index values. These relationships were reversed in the less affected streams farther away from the volcano. Fish assemblages were greatly influenced both by habitat and macroinvertebrate changes. The eruption brought about an initial sharp decline in fish densities and the almost total loss of young of the year in the most western streams affecting recruitment. This effect diminished rapidly with distance from the emission center. Thirty months after the eruption, environmental changes are still occurring as a consequence of basin wide ash remobilization and transport.