Table 02 - Evaluation of parameters according to the classification of CONAMA Resolution No. 357/05

The analysis of the physicochemical and microbiological parameters of the stream reveals significant water quality degradation, consistently exceeding the limits set for Classes 2, 3, and 4 (likely based on Brazilian environmental standards). The Dissolved Oxygen (DO) had an average concentration of $4.7\ \text{mg/L}$, which is below the threshold of $> 5\ \text{mg/L}$ required for Class 2 waters, indicating conditions of stress for aquatic life, and reached a critical minimum value of only $0.5\ \text{mg/L}$. Nutrient pollution is highly evident, as the mean concentration of Total Phosphorus ($4.8\ \text{mg/L}$) and Total Nitrogen ($26.2\ \text{mg/L}$) drastically surpassed the established limits of $0.1\ \text{mg/L}$ and $2.18\ \text{mg/L}$ for all classes, respectively. Furthermore, the Biochemical Oxygen Demand (BOD) reached an average of $21.3\ \text{mg/L}$ and peaked at $73.4\ \text{mg/L}$, values far above the $5\ \text{mg/L}$ permitted for Class 2, signifying a substantial organic load. The most critical indicator of sanitary contamination is the mean of Thermotolerant Coliforms ($325,833.0\ \text{NMP/100mL}$), which exceeds the Class limits of $1,000$ to $4,000\ \text{NMP/100mL}$ by hundreds of times, confirming the discharge of raw sewage into the stream. Most of the other parameters (pH, Turbidity, and Total Solids) remained, on average, within or near the limits established for their respective Classes.对该溪流的理化与微生物学参数开展分析后发现，其水质出现显著退化，各项指标持续超出巴西环境标准规定的2、3、4类水体限值。溶解氧（Dissolved Oxygen，DO）平均浓度为4.7 mg/L，低于2类水体要求的＞5 mg/L阈值，表明水生生物生存已面临胁迫，最低临界浓度仅达0.5 mg/L。营养盐污染问题极为突出：总磷（Total Phosphorus）平均浓度为4.8 mg/L、总氮（Total Nitrogen）平均浓度为26.2 mg/L，分别大幅超出所有类别水体设定的0.1 mg/L与2.18 mg/L限值。生化需氧量（Biochemical Oxygen Demand，BOD）平均值为21.3 mg/L，峰值达73.4 mg/L，远高于2类水体允许的5 mg/L限值，表明水体有机负荷严重超标。卫生污染最具代表性的关键指标为耐热大肠菌群平均浓度（325,833.0 NMP/100mL），其数值较1000~4000 NMP/100mL的类别限值高出数百倍，证实该溪流存在未经处理的生活污水直排情况。其余多数参数（pH、浊度与总固体）的平均水平处于或接近对应类别的限值范围。