Blue-green roofs as nature-based solutions for urban areas: hydrological performance and climatic index analyses.

The water-regulating capacity of nature-based solutions (NBSs) plays a crucial role in providing a full range of ecosystem services and enhancing the resilience of urban systems. This work focuses on the hydrological performance of a particular NBS, the so-called blue-green roof (BGR). The BGR is designed to collect infiltrated rainfall in a water storage layer beneath the soil to support vegetation maintenance, enhance evapotranspiration and cooling, and minimize runoff and drainage system load. The study aims to evaluate the hydrological performance of the BGR at global and event scale and, for the first time, to model climatic factors (easy to measure using common sensors) that affect its stormwater retention capacity. The data collected over 2 years and 2 months at a 5-min resolution from a pilot study in Central Italy were analysed. Additionally, a new climatic index called AWWP-x (Antecedent Wet Weather Period index) was introduced and calculated. Results show that the BGR has an overall relevant retention rate (67.1%), although the value depends on the rainfall of the observed period. Approximately 50% of the rainfall events did not produce any runoff, and during the dry season, all events were totally absorbed by the BGR. Four climatic variables were identified as significant factors for predicting BGR retention performance (R2 = 0.50). The results suggest that AWWP-130 (number of days to reach 130 mm cumulative precipitation) could be a possible proxy for the BGR stormwater retention rate. In general, this study demonstrates the potential for evaluating, planning, and designing NBSs by considering the annual and interannual climatic variability of the investigated specific location.

The environmental impact of buffalo manure in areas specialized in mozzarella production, southern Italy.

Buffalo livestock plays a central role in the regional economy in some areas of southern Italy, through the production of mozzarella cheese. With about 250,000 heads per utilizable agricultural area (equal to 107,400 ha), livestock husbandry is intensive. An important issue with regard to high animal density is manure management, an activity determined by cost optimization and the laws governing environmental sustainability. According to community, national and international rules (European Directive 91/676, Italian rules 152/99 and 258/00), nitrate leakage is considered a pollution indicator related to breeding activities and must be kept within limits. Simulation studies were carried out in the Italian province of Caserta to evaluate the impact of leakage on groundwater. Manure was also collected from 35 livestock farms and the nitrogen content measured in the laboratory. The results showed an average content of 2 kg/m3 of nitrogen, corresponding to 50 kg per animal and year, while the nitrate concentrations in the groundwater were found to be lower than those predicted by simulation. The nitrogen content found in buffalo manure <60% of the standard content produced by the bovine species (on average 83 kg nitrogen per adult animal per year). The fact that the bovine species is used as the standard reference for legislation on nitrogen production explains the inconsistency observed between the impact of buffalo livestock on the environment predicted by simulation and the nitrate concentration measured in the groundwater. Although it would be out of line with current regulations, it would theoretically be possible to increase the buffalo load on the territory without environmentally negative effects. Therefore, in this context, the common referral points, i.e. the American Midwest Point Service and others usually consulted for the assessment of livestock impact in terms of nutritional excretion and the risk of pollution for the environment, should be revisited.

Spatial assessment of animal manure spreading and groundwater nitrate pollution.

Nitrate concentration in groundwater has frequently been linked to non-point pollution. At the same time the existence of intensive agriculture and extremely intensive livestock activity increases the potential for nitrate pollution in shallow groundwater. Nitrate used in agriculture could cause adverse effects on human and animal health. In order to evaluate the groundwater nitrate pollution, and how it might evolve in time, it is essential to develop control systems and to improve policies and incentives aimed at controlling the amount of nitrate entering downstream water systems. The province of Caserta in southern Italy is characterized by high levels of animal manure loading. A comparison between manure nitrogen production and nitrate concentration in groundwater was carried out in this area, using geostatistical tools and spatial statistics. The results show a discrepancy between modelling of nitrate leaching and monitoring of the groundwater and, moreover, no spatial correlation between nitrogen production in livestock farms and nitrate concentration in groundwater, suggesting that producers are not following the regulatory procedures for the agronomic use of manure. The methodology developed in this paper could be applied also in other regions in which European Union fertilization plans are not adequately followed.