To assess impacts of clear-cutting at a pure Acacia plantation on soil and water quality, a 7-year-old Acacia forest within the area of 2.5 ha in Hoa Binh province was selected to investigate at 2 stages: before and after clear-cutting. 03 standard plots (500 m2/plot) at 3 positions (downhill, mid-hill and top-hill) for determining forest characteristics, 30 sampling subplots (1 m2/plot) for monitoring forest covers and some soil properties. 15 of 30 subplots were used to measure infiltration; and 4 points along forest flow were chosen to take water sampling for assessing water quality. Main findings include: (1) Forest cover decreased within the removal of tree, reduction of understory vegetation cover, litter and biomass ranged from 10 to 20%; (2) Soil quality decreased by 8.35% dropped of porosity due to the rise of 8.57% in dry bulk density; (3) Soil nutrients: Organic matter, total Phosphorus and Nitrogen amount decreased at the proportion of 20.91%, 62.86% and 27.86% respectively after clear-cutting; (4) Total infiltration rate decreased after harvesting. The positions that had high infiltration rate before clear-cutting tended to infiltrate noticeably less (Downhill: reducing from 397.7 mm to 201.2 mm); (5) Soil erosion increased significantly after cutting and was remarkably higher in comparison with other research results due to the slope of researching area; (6) Most water quality indicators were at acceptable values, however, TSS and COD were 180-time and 5.6-time higher than water standard at B1 category (water for irrigation) according to QCVN 08:2015/BTNMT; (7) Some solutions suggested for sustainable management are (a) replacing production planted forest at researching site by protection forest or natural forest or (b) remaining commercial plantation forest but adjust management methods.

This study aims to analyze spatial and temporal changes of surface and groundwater quality from March to December 2019, in Son Dong commune, Hoai Duc district, Hanoi. A number of physicochemical parameters were sampled for analysis to give quantitative assessments, and spatial distribution as well as temporal variation were performed. Surface water samples were collected along the commune canal route at different depths (20 and 30 cm) and groundwater samples were taken from drill-wells. From March to December 2019, 10 groundwater samples and 5 surface water samples were collected. 7 surface water parameters including: Fe, NH4+, Mn, NO2-, Cu, TSS and pH, 8 groundwater parameters including: Fe, NH4+, Mn, NO2-, Cu, pH, TDS, and hardness were analyzed. Based on analyzed water quality findings, both surface and groundwater in Son Dong are heavily polluted compared to the standard of Ministry of Natural Resources and Environment. The indicators of pH, TSS, TDS and NO2-, were almost unchanged and lower than the permitted value. Water quality in the study area is contaminated with heavy metals. The analysis results of NH4+, Cu, Fe parameters are higher than the permitted standards QCVN 08: 2015/TNMT for surface water and 09: 2015/TNMT for groundwater. The groundwater quality index (GWQI) was calculated based on the analyzed criteria is higher than 200, which means it is not suitable for drinking. The most polluted areas are in the south and northwest of Son Dong commune. Therefore, in the face of poor water quality, it is necessary to have some suitable solutions to improve water quality in the study area.