The selection of paired watersheds affects the assessment of wildfire hydrological impacts.

Wildfires strongly alter hydrological processes and surface and groundwater quality in forested environments. The paired-watershed method, consisting of comparing a burnt (altered) watershed with an unburnt (control) watershed, is commonly adopted in studies addressing the hydrological effects of wildfires. This approach requires a calibration period to assess the pre-perturbation differences and relationships between the control and the altered watershed. Unfortunately, in many studies, the calibration phase is lacking due to the unpredictability of wildfires and the large number of processes that should be investigated. So far, no information is available on the possible bias induced by the lack of the calibration period in the paired-watershed method when assessing the hydrological impacts of wildfires. Through a literature review, the consequences of the lack of calibration on the assessment of wildfire hydrological changes were evaluated, along with the most used watershed pairing strategies. The literature analysis showed that if calibration is lacking, misestimation of wildfire impacts is likely, particularly when addressing low-severity or long-term wildfire effects. The Euclidean distance based on physical descriptors (geology, morphology, vegetation) was proposed as a metric of watersheds similarity and tested in mountain watersheds in Central Italy. The Euclidean distance proved to be an effective metric for selecting the most similar watershed pairs. This work raises awareness of biases exerted by lacking calibration in paired-watershed studies and proposes a rigorous and objective methodology for future studies on the hydrological effects of wildfires.

Bioaccumulation and biomagnification in elasmobranchs: A concurrent assessment of trophic transfer of trace elements in 12 species from the Indian Ocean.

We provided the first multi-species study investigating the presence and organotropism of trace elements in three tissues of 12 elasmobranch species. Shark species showed comparable TE loads, although milk sharks and juvenile scalloped hammerhead sharks exhibited the highest Cd and Hg levels, respectively. Fins accumulated higher levels of Pb, Co, and Cr; muscles higher V, As, and Hg; livers higher Se and Cd levels. The organotropism of TEs calls for cautious when choosing a tissue to be sampled since certain tissues, like fin clips, do not provide reliable surrogate for the internal loads of some TEs. Strong correlations between essential and toxic TEs indicated detoxification mechanisms, while the TMF provided evidence for Hg, As and Se biomagnification along the food-web. Considering the difficulties in assessing elasmobranchs contamination from different areas, the proposed multi-species approach represents a valuable way to estimate the species-specific accumulation and transfer of pollutants in sharks.

Stable isotope analysis of archaeological oak charcoal from eastern Anatolia as a marker of mid-Holocene climate change.

Comparison between modern trees and archaeological charred wood is an under-explored method to study climate change, which may help to infer past environmental changes. The stable carbon content of deciduous oak charcoals was analysed for five periods covering more than a 1000 years (3350-2000 BC) at the site of Arslantepe, Turkey, together with modern deciduous oak specimens from five rare arboreal patches still present in the area (17-64 km from the site). In studies of past climate change it is difficult to distinguish human-induced changes from independent variations, such as the impact of past populations on the landscape and their relationship with climate changes in the mid-Holocene. Archaeology can evaluate climate signals preserved in fossil plants in light of past human life. This paper will contribute to understanding environmental changes that can be attributed to climate variation and those linked to human activities. We compared (13) C/(12) C of modern and fossil oaks in order to correlate the (13) C-content to environmental features of Arslantepe, both today and between 3350 and 2000 BC. At present, this area is semi-arid. The results show important similarities to palaeoenvironmental records for the rest of the Near East. The climate trend can be divided in three main phases: instability phase from ca. 3200 to 2900 BC; a phase of relative stability (until 2350 BC); and a final increase in aridity. The comparison of Δ(13) C values between fossil and modern plants shows that present climate is more arid than that between the end of the fourth and the whole third millennium BC.

A simple model to assess nitrogen and phosphorus contamination in ungauged surface drainage networks: application to the Massaciuccoli Lake Catchment, Italy.

Modeling is a common practice to evaluate factors affecting water quality in environmental systems impaired by point and nonpoint losses of N and P. Nevertheless, in situations with inadequate information, such as ungauged basins, a balance between model complexity and data availability is necessary. In this paper, we applied a simplified analytical model to an artificially drained floodplain in central-western Italy to evaluate the importance of different nutrient sources and in-stream retention processes and to identify critical source areas. We first considered only a set of chemical concentrations in water measured from February through May 2008 and from November 2008 through February 2009. We then broadened available data to include water discharge and hydraulic-head measurements to construct a hydrogeological model using MODFLOW-2000 and to evaluate the reliability of the simplified method. The simplified model provided acceptable estimates of discharge (ranging from 0.03-0.75 m s) and diffuse nutrient inputs from water table discharge and in-stream retention phenomena. Estimates of PO-P and total P retention (ranging from 1.0 to 0.6 µg m s and from 1.18 to 0.95 µg m s for PO-P and total P, respectively) were consistent with the range of variability in literature data. In contrast, the higher temporal variability of nitrate concentrations decreased model accuracy, suggesting the need for more intensive monitoring. The model also separated the dynamics of different reaches of the drainage network and identified zones considered critical source areas and buffer zones where pollutant transport is reduced.