Sampling and sub-sampling of granular waste: size of a representative sample in terms of number of particles

This paper elucidates the theoretical principles behind the calculation of the size of a representative sample of granular solid waste. The key concept is the number of particles that must be present in a sub-portion of matter to be representative of a larger portion of matter. This depends on the fraction of particles in the waste batch showing the properties of interest, which shall be measured. A representative sample must include a fraction of particles of interest reliably similar to that of the waste batch to be characterized, with a controlled variability. In this context, it is demonstrated that the number of particles of interest that must be collected in a representative sample is 100. From this requirement, the mass of a representative sample can be calculated based on the knowledge of the frequency of particles of interest of the waste lot to be characterized. Data on particles concentrations in different samples of WEEE plastic scraps exemplifies how the presence in the sample of enough rare particles showing the property of interest is key to ensure reliable measurements. Further, the assumptions made on the controlled degree of variability to determine the minimum number of particles are discussed based on data on achievable intra- and inter-laboratory variability of analytical standards for waste characterization. Accordingly, the mass of laboratory samples and test portions recommended in published sampling plans or analytical standards are assessed for the occurring number of particles.

Use of crushing residue as nutrients source in the cocoa seedlings development in Medicilândia – PA

The use of milled rocks has been postulated as an efficient way to provide nutrients to the plants. The objective of this work was to evaluate the cocoa seedlings agronomic performance in different Diabase Penatecaua powder treatments. The study comprehends the following phases: i) involved waste characterization, ii) treatments definition and sampling; iii) monitoring and evaluation; iv) systematization and results discussion. The experiment was realized with cocoa seedlings germinated in commercial organic substrate in the period from July to September 2019. The used rock dust was extracted at Km 85, Transamazônica highway, Medicilândia municipality – Pa. The extraction area lithology is formed by igneous rocks of Diabase Penatecaua. The experimental delineation was entirely randomized, with four repetitions per treatment, being them respectively in the dosages 0, 25, 50 and 75 (g / plant), being 16 plants per block, totaling 64 plants, and their irrigation done manually in the first hours of the day. Therefore, the results showed that the dosages were absorbed by the cocoa seedlings according to the plant's need allied to pH balance, which was caused by good nutritional cycling with the organic matter high rate present in the commercial substrate when in contact with the Diabase Penatecaua powder worked granulometry. However, the experiment time wasn’t enough to obtain statistically a significant difference. Thus, it is necessary that new studies be done aiming the temporal deepening of the studied doses for the culture.