## 3 Results
### The Pattern of Copper Quantity Changes
\begin{table}
\begin{tabular}{c c c c c c c} \hline
**Cu** & **C** & \(p\)**-Value** & \multicolumn{4}{c}{**Phase**} \\ \hline  & & & **1** & **2** & **3** & **4** \\ \hline Fr. II & 1 & \(2.25\times 10^{-7}\) *** & c & a & b & a \\ \hline  & 2 & \(2.82\times 10^{-10}\) *** & d & c & b & a \\ \hline  & 3 & \(3.24\times 10^{-7}\) *** & c & b & ab & a \\ \hline Fr. III & 1 & \(4.64\times 10^{-6}\) *** & c & d & b & a \\ \hline  & 2 & \(5.47\times 10^{-9}\) *** & c & b & a & a \\ \hline  & 3 & \(1.28\times 10^{-11}\) *** & c & c & b & a \\ \hline Fr. IV & 1 & 0.00054 *** & cb & b & b & a \\ \hline  & 2 & 0.365 & & & & \\ \hline  & 3 & 0.291 & & & \\ \hline  & bioava & 1 & \(1.14\times 10^{-7}\) *** & c & c & a & b \\ \hline  & 2 & \(1.64\times 10^{-12}\) *** & c & b & a & a \\ \hline  & 3 & \(8.34\times 10^{-11}\) *** & c & a & a & b \\ \hline Ni & Fr. I & 1 & \(1.63\times 10^{-6}\) *** & a & b & c & c \\ \hline  & 2 & \(5.74\times 10^{-6}\) *** & a & b & bc & c \\ \hline  & 3 & \(7.23\times 10^{-7}\) *** & a & b & b & b \\ \hline  & Fr. II & 1 & 0.0578 & & & \\ \hline  & 2 & 0.0179 * & b & a & ab & a \\ \hline  & 3 & \(3.3\times 10^{-6}\) *** & b & b & b & a \\ \hline Fr. III & 1 & \(1.21\times 10^{-5}\) *** & c & b & b & a \\ \hline  & 2 & 0.00162 ** & b & a & a & a \\ \hline  & 3 & 0.00348 ** & b & a & a & a \\ \hline Fr. IV & 1 & \(2.54\times 10^{-8}\) *** & d & c & b & a \\ \hline  & 2 & 0.0266 * & a & ab & b & ab \\ \hline  & 3 & \(4.65\times 10^{-5}\) *** & c & b & ab & a \\ \hline bioava & 1 & \(1.57\times 10^{-6}\) *** & a & ab & b & c \\ \hline  & 2 & \(6\times 10^{-4}\) *** & a & a & c & ba \\ \hline  & 3 & 0.144 & & & & \\ \hline Signif. codes: 0 \({}^{\prime\prime\prime\prime}\) 0.001 \({}^{\prime\prime\prime\prime}\) 0.01 \({}^{\prime\prime\prime\prime}\) 0.05 \({}^{\prime\prime}\).0 1 \({}^{\prime\prime}\) 1. & & & & \\ \hline \end{tabular}
\end{table} 
Table 4: _Cont._and C2, with the highest values occurring in the cooling phase (Table 5, Figure 2). In C1, greater increases in Cu content were recorded in Fr. III (21.33%) than in C2 (8.96%). In C3, the smallest increase in the amount of Cu Fr. III was found in the cooling phase (1.76%), while the largest increase was at the beginning of the thermophilic phase (36.03%). The content of Cu Fr. IV at the end of the mesophilic phase in C1 was comparable to the values observed up to the end of the cooling phase and was significantly greater than the values observed in the mature compost (Table 4). In C2, the Cu residual amounts at the end of the mesophilic phase were comparable to the values observed up to the end of the thermophilic phase and were significantly lower than the values observed in the mature compost. In C3, the Cu content of fraction IV increased significantly after the end of the mesophilic phase. The rate of change in the Cu content in Fr. IV was significantly influenced by the tested composts (Table 5, Figure 2). In C1, the residual Cu content decreased, and the rate of reduction was the highest in the mature compost, reaching a value of 25.01%. In C2, the Cu Fr. IV content successively increased, but the greatest increase (25.41%) was observed in the initial part of the process in the thermophilic phase. At C3, there was a 53.89% increase in the residual copper content in the thermophilic phase, followed by a 4.47% decrease and a slow increase in the mature compost, reaching 11.50%. In all compost mixtures, the bioavailable amounts of Cu observed at the end of the mesophilic phase were significantly lower than the values observed in the subsequent composting stage (Table 4). An analysis of the chain relative increments in the bioavailable copper content revealed an increase in the copper content in all phases. The greatest increases in its content were recorded in the thermophilic phase, with values of 109.21% (C1), 55.02% (C2), and 97.01% (C3). Regardless of the type of compost, the amount of bioavailable copper increased further in the composting process, not exceeding 29.55% for C2 and the cooling period (Table 5, Figure 2).