Relative contribution of atmospheric and riverine inputs of metals, nutrients and POPs into the Lagoon of Venice.

Atmospheric deposition in the lagoon of Venice and river inputs from the watershed were collected and analysed over more than one year (1999-2000) using the same analytical methods. The input from riverine sources largely prevails (>70%) over that from the atmosphere for As, Cr, Fe, Mn, Ni, nitrogen and phosphorus. Equivalent amounts of Hg, Pb, PCB, HCB are discharged into the lagoon from the two sources, whilst atmospheric inputs prevail for Cd, ammonia and dioxins. A comparison with figures of maximum allowable discharges (MAD) for various compounds, recently set by the Italian Ministry for the Environment, showed that total inputs (riverine + atmospheric) of trace metals were lower than the MAD only for Cr, Cu, Ni and Zn. The total inputs of Cu and Ni, and Cr and Zn were approximately 20% and 40% of the MAD limit, respectively. The total phosphorus input of 284 t was close to the imposed limit, whilst the total inorganic nitrogen load (>4000 t) was much higher than the MAD. For those metals and POPs (As, Cd, Hg, Pb, PCDD/Fs) where the MAD states that the load should tend to “0” (no discharge), the measured inputs of 4.8 (As) and 5.1 t (Pb), 151 (Cd) and 39 kg (Hg), 18 g (PCDD/F) and 440 mg (TEQPCDD/F) are by definition “above” the MAD. Using principal component analysis (PCA) data have been compared with available input profiles (markers) related to production typologies, both in the watershed and in the industrial zone located on the lagoon border (Porto Marghera). PCA showed that river and atmosphere contributions can be easily separated and recognised due to their different fingerprints. In particular, riverine inputs were more similar to chemical and glass work production markers, whereas atmospheric ones appeared to be mainly influenced by industry (PVC and VCM production), metallurgy and paper-mill. These results highlight the need to implement improved technologies in order to arrive at a “good ecological status” for all surface and ground water bodies by 2015, as stated by the EU Water Framework Directive

Understanding the degradation of methylenediammonium and its role in phase-stabilizing formamidinium lead triiodide

Formamidinium lead triiodide (FAPbI3) is the leading candidate for single-junction metal-halide perovskite photovoltaics, despite the metastability of this phase. To enhance its ambient-phase stability and produce world-record photovoltaic efficiencies, methylenediammonium dichloride (MDACl2) has been used as an additive in FAPbI3. MDA2+ has been reported as incorporated into the perovskite lattice alongside Cl-. However, the precise function and role of MDA2+ remain uncertain. Here, we grow FAPbI3 single crystals from a solution containing MDACl2 (FAPbI3-M). We demonstrate that FAPbI3-M crystals are stable against transformation to the photoinactive δ-phase for more than one year under ambient conditions. Critically, we reveal that MDA2+ is not the direct cause of the enhanced material stability. Instead, MDA2+ degrades rapidly to produce ammonium and methaniminium, which subsequently oligomerizes to yield hexamethylenetetramine (HMTA). FAPbI3 crystals grown from a solution containing HMTA (FAPbI3-H) replicate the enhanced α-phase stability of FAPbI3-M. However, we further determine that HMTA is unstable in the perovskite precursor solution, where reaction with FA+ is possible, leading instead to the formation of tetrahydrotriazinium (THTZ-H+). By a combination of liquid- and solid-state NMR techniques, we show that THTZ-H+ is selectively incorporated into the bulk of both FAPbI3-M and FAPbI3-H at ∼0.5 mol % and infer that this addition is responsible for the improved α-phase stability

Harmful Elements in Estuarine and Coastal Systems

Estuaries and coastal zones are dynamic transitional systems which provide many economic and ecological benefits to humans, but also are an ideal habitat for other organisms as well. These areas are becoming contaminated by various anthropogenic activities due to a quick economic growth and urbanization. This chapter explores the sources, chemical speciation, sediment accumulation and removal mechanisms of the harmful elements in estuarine and coastal seawaters. It also describes the effects of toxic elements on aquatic flora and fauna. Finally, the toxic element pollution of the Venice Lagoon, a transitional water body located in the northeastern part of Italy, is discussed as a case study, by presenting the procedures adopted to measure the extent of the pollution, the impacts on organisms and the restoration activities