S.K. Reza

Hazard assessment of heavy metal contamination by the paper industry, north-eastern India

The spatial distribution and hazard assessment of heavy metals in the paper mill contaminated area of Jagiroad, Assam, India were investigated using statistics, geostatistics and geographic information system techniques. The amounts of Cr, Cd, Ni and Pb were determined from 188 samples collected within the contaminated area. Log-transformation was applied in order to achieve normality in the data-set. The ordinary kriging estimates of Cr, Cd, Ni and Pb maps showed that high concentrations of heavy metals were located in the low-lying areas like bils (lakes). Indicator kriged probability maps of soil Cr, Cd, Ni and Pb were prepared based on the concentrations to exceed the respective Food and Agriculture Organization maximum permissible limit (MPL) value of 100, 3, 30 and 50 mg/kg, respectively. It was seen that more than 80% of the studied area has a higher than 50% probability to exceed the MPL value of Ni. Smaller areas in the north and west side of the study area displayed a higher concentration than the MPL value of Pb. For Cr, only a small portion at the centre of the study area had a higher concentration than the MPL value. In an attempt to identify the source of heavy metals through multivariate analysis, it was concluded that Cr, Ni and Pb mainly originated from paper mill effluent and soil Cd was associated with natural concentration.

Distribution of forms of potassium in relation to different agroecological regions of North-Eastern India

Distribution of potassium (K) in soils is governed by the agroecological region (AERs), as the operational intensity of factors and processes of soil formation vary with AER. Therefore, we aimed at finding out the relationship between the forms of K(K forms) with AER and the association of K forms with soil properties in the North-Eastern region of India. For this, horizon-wise soil samples were collected from pedons, three each from three AERs (15 (hot sub-humid to humid), 16 (warm per-humid) and 17 (warm per-humid with less cool winter)) in the North-Eastern India. The water balance diagram for AER shows that precipitation (P) exceeds the potential evapo-transpiration (PET) from June to October, AER 16 shows almost no period when the PET is more than the P and AER 17 shows that the region experiences only a short water deficit of 100–150 mm during post-monsoon period. Soil samples were analysed for physical and chemical properties and K forms. The soils were acidic to neutral with low cation exchange capacity (CEC). The water-soluble K ranged between 0.006 and 0.144 cmol kg−1, exchangeable K between 0.07 and 0.54 cmol kg−1, fixed K from 16.7 to 61.3 cmol kg−1 and total K from 17.4 to 63.6 cmol kg−1 in soils of different horizons. Further, the results revealed that all the K forms followed the trend of AER 16 > AER 17 >AER 15. Exchangeable K showed higher correlation with clay (r = 0.519**), while fixed K with organic carbon (r = 0.390*).

Multivariate Approaches for Soil Fertility Characterization of Lower Brahmaputra Valley, Assam, India

The aim of this study was to characterize the soil fertiltiy like pH, organic carbon (OC), available nitrogen (N), available potassium (P) and available phosphorus (K), and DTPA extractable iron (Fe), manganese (Mn), zinc (Zn) and copper (Cu) of lower Brahmaputra valley of Assam using multivariate statistics (principal component, correlation matrix and cluster analysis). A total of 2753 soil samples from a depth of 0–25 cm at an approximate interval of 1 km were collected from Barpeta, Bongaigaon and Nalbari districts of Assam. Soil properties showed large variability with greatest variation was observed in DTPA-Zn (120%), whereas the smallest variation was in pH (17.5%). The principal component analysis (PCA) applied on the investigated soil properties identified three components with eigen values greater than 1, which explained 65% variability and same grouping was also obtained from cluster analysis. Cluster 1 includes Zn, Cu, pH, Fe, P and Mn, which has highest loading in PC1 and also showed strong significant relationship. Cluster 2, which contains OC and N, and had highest loading in PC2 and also showed the significant positive relationship with each other. Cluster 3 contain only K, which is equally distributed both in PC1 and PC2 and also significantly and positively correlated with pH, Fe, Zn and Cu of cluster 1 and OC and N of cluster 2.