How do properties and heavy metal levels change in soils fertilized with regulated doses of urban sewage sludge in the framework of a real agronomic treatment program?

Purpose

This field study was performed to assess the variation in chemical and agronomic properties and total and extractable concentrations of heavy metals in soils fertilized with regulated doses of urban sewage sludge (USS) for 6 consecutive years in the framework of an agronomic treatment program.

Materials and methods

Chemical and agronomical properties, total contents and extractable concentrations of Cd, Cr, Cu, Hg, Ni, Pb and Zn were determined in agricultural soils treated with USS for 6 consecutive years, agricultural soils cultivated using mineral fertilizers and uncultivated soils representative of the local geochemical background.

Results and discussion

USS application caused a decrease in pH and an increase in extractable concentrations of Cr, Cu, Pb and Zn. No organic carbon, total nitrogen and total phosphorus enrichment trend was observed in the treated soils due to biodegradation of the organic compounds supplied by USS. The decomposition of USS organic matter was presumably the main process responsible for the pH decrease in the USS-fertilized soils. There was no heavy metal accumulation in treated soils, and total heavy metal contents were below the corresponding maximum threshold concentrations set by European and Italian legislation. Increased availability of Cr, Cu, Pb and Zn was found in treated soils due to an increase in their extractable concentrations in the treatment period.

Conclusions

The results of this study suggest that the environmental risks related to the accumulation and availability of heavy metals in agricultural soils fertilized with USS are limited when treatment observes recommended doses in agronomic treatment programs.

     

Artisanal fishing,dolphins, and interactive pinger: A study from a passive acoustic perspective

1. Dolphins interact with many types of fishing gear, causing damage to fishing activities and in some cases facing harm and becoming entangled as bycatch.
2. In this study, the behaviour of bottlenose dolphins during their interaction with set nets, equipped with and without interactive pingers, was investigated. Acoustic monitoring of the nets was conducted for a total of 56 hauls and 814.9 hr of recordings, from the 16 October to 13 November 2015, along the coast of Lampedusa island (Sicilian Channel, Italy, Mediterranean Sea).
3. The level of interaction between dolphins and the nets was evaluated considering the number of dolphin clicks grouped over time (single acoustic incursion on each net), the duration of every acoustic incursion, and the number of dolphin clicks per incursion. Moreover, the catch rate was measured as the number of fish per hour for each net.
4. Based on the recording time of dolphin clicks, the spatio-temporal development of the interaction with the nets located in different bays of the island was assessed.
5. The duration of the interaction between dolphins and nets significantly increased over the study period, with a concomitant reduction in catch rate. The interactive pinger showed efficacy in protecting the nets from dolphin depredation during the first period of 36 hauls and 11 fishing days (higher catch rates and lower incursion durations), whereas no differences were found in any interaction parameters between pinger and control nets in the second period (20 hauls and six fishing days).
6. Interactive pingers may be an effective, short-term (2–3 weeks) tool in deterring depredation by bottlenose dolphins in small-scale artisanal fisheries. Other mitigation approaches, such as gear modification, lessons learned through outreach, and passive acoustic monitoring of the nets, could improve the management of the interactions between fisheries and bottlenose dolphins.

     

Predicting changes in soil organic carbon in mediterranean and alpine forests during the Kyoto Protocol commitment periods using the CENTURY model

Six Italian research sites, representative of Mediterranean and mountain forests and equipped with eddy covariance towers, were used in this study to test the performance of the CENTURY 4.5 model in predicting the dynamics of soil organic carbon (SOC) changes during the commitment periods (CP) of the Kyoto Protocol (2008–2012; 2013–2017). We show that changes in SOC stocks over short periods of time are difficult to detect, and explore the potential for models to be used for reporting SOC changes for forests that will remain forests, under Article 3.4 of the Kyoto Protocol. As the eddy covariance flux sites have been active for 10 yr on average, being initiated over the period between 1996 and 1998, the model was evaluated by comparing the modelled SOC stocks with those directly measured at each site in different years. Since long term series of observed values for soil carbon were not available, the validation of other model outputs such as net primary production (NPP) and soil nitrogen stocks, gives some confidence in long term simulations. Once the model performance was evaluated, two climate change scenarios, A1F1 (world markets‐fossil fuel intensive) and B2 (local sustainability), were considered for prediction of C stock changes during the commitment periods of the Kyoto Protocol. In general, despite the need to consider the uncertainties in the direct measurements, at each site model fit with measured SOC stocks was good, with the simulated values within the standard deviation of the measurements. In this regard, the similarity between the SOC measured in 2008 and that predicted for the two forthcoming commitment periods points out the difficulty of detecting carbon stock changes by direct measurements, given the closeness in time to the present of the commitment periods. In any case, all sites show positive variations that are possibly related to the fertilization effects of increasing CO₂ and to longer growing seasons, since no change in management occurred. Compared with the SOC measured in 2008, at the end of the second commitment period, the modelled SOC variations were smaller than 2% in the Mediterranean forests and comprised between 2% and 7% in the mountain forests. These variations, although small, indicate it might be possible to statistically detect differences after 10 yr in mountain forests with a reasonable number of samples. In conclusion, this work shows that since SOC stock changes are minimal within both CP, models can be effective tools for estimating future changes in SOC amounts, as an alternative to, or in support of, direct measurements when a short period of time is considered.     

Whistle variability of the Mediterranean short beak common dolphin

1. The short-beaked common dolphin is a highly vocal species, with a wide distribution in all oceans, including the Mediterranean and the Black Seas. In the Mediterranean Sea, the short-beaked common dolphin inhabits both pelagic and neritic waters.
2. Osteological collections and the literature show that short-beaked common dolphins were widespread and abundant in much of the Mediterranean Sea until the late 1960s. During recent decades the species has declined in the whole basin, and, in 2003, it was listed as Endangered in the IUCN Red List.
3. Genetic studies strongly suggest that the Mediterranean and the Eastern North Atlantic populations are isolated from each other. Genetic differentiation within the Mediterranean Sea, between the Eastern Mediterranean (Ionian Sea) and Western Mediterranean populations, is also reported.
4. The aim of this study was to investigate the geographical variation in the characteristics of whistles of free-ranging short-beaked common dolphins living in the Mediterranean Sea, and to evaluate if whistle acoustic structure is the result of adaptation to local environment characteristics or of a possible genetic diversification.
5. Recordings were collected from 1994 to 2012 throughout the basin, employing multiple platforms. Twenty-six independent acoustic detections were made, and 704 whistles were extracted and considered for statistical analysis.
6. Whistle analysis enabled the identification of distinct geographical units of short-beaked common dolphin within the Mediterranean Sea. Genetic isolation is probably the major cause of the geographic variance of the Mediterranean short-beaked common dolphin whistle structure, which may reflect some evolutionary adaptations to particular ecological conditions or may be the by-product of morphological evolution.
7. The results of the present study show that intra-Mediterranean variability of whistle structure reflects the path of genetic studies, highlighting the possible use of acoustic data in combination with other sources of data (genetic, morphological, etc.) to identify geographic areas where discrete management units occur.