The complexation of heavy metals with dissolved organic matter (DOM) in the environment influences the solubility and mobility of these metals. In this paper, we measured the complexation of Cu, Cd, Zn, Ni, and Pb with DOM in the soil solution at pH 3.7-6.1 using a Donnan membrane technique. The results show that the DOM-complexed species is generally more significant for Cu and Pb than for Cd, Zn, and Ni. The ability of two advanced models for ion binding to humic substances, e.g., model VI and NICA-Donnan, in the simulation of metal binding to natural DOM was assessed by comparing the model predictions with the measurements. Using the default parameters of fulvic and humic acid, the predicted concentrations of free metal ions from the solution speciation calculation using the two models are mostly within 1 order of magnitude difference from the measured concentrations, except for Ni and Pb in a few samples. Furthermore, the solid-solution partitioning of the metals was simulated using a multisurface model, in which metal binding to soil organic matter, dissolved organic matter, clay, and iron hydroxides was accounted for using adsorption and cation exchange models (NICA-Donnan, Donnan, DDL, CD-MUSIC). The model estimation of the dissolved concentration of the metals is mostly within 1 order of magnitude difference from those measured except for Ni in some samples and Pb. The solubility of the metals depends mainly on the metal loading over soil sorbents, pH, and the concentration of inorganic ligands and DOM in the soil solution.

Complexation with dissolved organic matter and solubility control of heavy metals in a sandy soil.

Prediction of the fate of metals in soil requires knowledge of their solid―liquid partitioning. This paper reviews analytical methods and models for measuring or predicting the solid―liquid partitioning of metals in aerobic soils, and collates experimental data. The partitioning is often expressed with an empirical distribution coefficient or K d , which gives the ratio of the concentration in the solid phase to that in the solution phase. The K d value of a metal reflects the net effect of various reactions in the solid and liquid phases and varies by orders of magnitude among soils. The K d value can be derived from the solid― liquid distribution of added metal or that of the soil-borne metal. Only part of the solid-phase metal is rapidly exchangeable with the solution phase. Various methods have been developed to quantify this 'labile' phase, and K d values based on this phase often correlate better with soil properties than K d values based on total concentration, and are more appropriate to express metal ion buffering in solute transport models. The in situ soil solution is the preferred solution phase for K d determinations. Alternatively, water or dilute-salt extracts can be used, but these may underestimate in situ concentrations of dissolved metals because of dilution of metal-complexing ligands such as dissolved organic matter. Multi-surface models and empirical models have been proposed to predict metal partitioning from soil properties. Though soil pH is the most important soil property determining the retention of the free metal ion, K d values based on total dissolved metal in solution may show little pH dependence for metal ions that have strong affinity for dissolved organic matter. The K d coefficient is used as an equilibrium constant in risk assessment models. However, slow dissociation of metal complexes in solution and slow exchange of metals between labile and non-labile pools in the solid phase may invalidate this equilibrium assumption.

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Partitioning of metals (Cd, Co, Cu, Ni, Pb, Zn) in soils: concepts, methodologies, prediction and applications ― a review

We report the soil solution speciation of Cd in 64 field-collected contaminated soils containing between 0.1 and 38 mg Cd kg-1. The soils were analyzed for pH (3.5−8.1), soil organic matter (8.0−108 g C kg-1), total dissolved Cd (0.03−182 μg Cd L-1), dissolved organic carbon (1.5−12 mg C L-1), and free Cd2+ (10-10−2 × 10-7 M). Free Cd2+ activity in solution was determined using differential pulse anodic stripping voltammetry (DPASV), assuming DPASV is sensitive to easily dissociated inorganic ion-pairs and free Cd2+ while excluding organic complexes. The solid/liquid partition coefficient (Kd) varied over a range from 10 to 100 000, and the fraction of the dissolved Cd present in solution as the estimated free Cd2+ species varied between 0 and 60% but averaged about 20%. The dissolved concentrations of Cd and the free Cd2+ activity in the soil solutions of contaminated soils of different origins can be predicted with reasonable accuracy using a simple competitive adsorption model dependent on pH and total...

Speciation and Complexation of Cadmium in Extracted Soil Solutions

Mobilisation of heavy metals by deicing salts in a roadside environment.

Soil phosphatase levels strongly control the biotic pathways of phosphorus (P), an essential element for life, which is often limiting in terrestrial ecosystems. We investigated the influence of climatic and soil traits on phosphatase activity in terrestrial systems using metadata analysis from published studies. This is the first analysis of global measurements of phosphatase in natural soils. Our results suggest that organic P (Porg), rather than available P, is the most important P fraction in predicting phosphatase activity. Structural equation modeling using soil total nitrogen (TN), mean annual precipitation, mean annual temperature, thermal amplitude and total soil carbon as most available predictor variables explained up to 50% of the spatial variance in phosphatase activity. In this analysis, Porg could not be tested and among the rest of available variables, TN was the most important factor explaining the observed spatial gradients in phosphatase activity. On the other hand, phosphatase activity was also found to be associated with climatic conditions and soil type across different biomes worldwide. The close association among different predictors like Porg, TN and precipitation suggest that P recycling is driven by a broad scale pattern of ecosystem productivity capacity.

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Global patterns of phosphatase activity in natural soils.

The pH dependence of free ionic activities and total dissolved concentrations of copper and cadmium in soil solution

The activities of acid and alkaline phosphatases, β-glucosidase and urease were determined in soils under different land-use systems after deforestation in hilly areas of West Lampung, South Sumatra, Indonesia. Soil samples (topsoils, 0–20 cm and subsoils, 20–40 cm) were collected from 5 different locations, each consisting of 4 different land-use systems: i.e. primary forests, secondary forests, coffee plantations, and cultivated lands (upland fields and paddy fields). Enzyme analyses showed that the activities of phosphatases, β-glucosidase, and urease were significantly higher in most cases in the primary forests or in the secondary forests than in the other two land-use systems, indicating that clearing the forests and converting them to other land-use systems significantly disturbed the growth of enzyme-producing organisms. There was no significant difference in the enzymatic activities between cultivated upland fields and paddy fields. The activity of alkaline phosphatase showed the most dr...

https://www.tandfonline.com/doi/pdf/10.1080/00380768.1998.10414429

Activities of some soil enzymes in different land use systems after deforestation in hilly areas of West Lampung, South Sumatra, Indonesia

We monitored the land use changes in a hilly area of West Lampung, South Sumatra, Indonesia, from 1970 to 1990. The main data sources were the land use maps produced in 1970, 1978, 1984, and 1990 covering on area of 27 km2. The area was divided into 108 × 108 cell squares (0.25 km × 0.25 km) and the largest land use form in the respective squares were mapped using a computer program. Fifty-seven percent of the study site was covered with primary forests in 1970, against 13% in 1990. Areas under plantation which were not recorded in 1970, increased to 60% in 1990. In addition, the change from monoculture plantations (mostly coffee plantation) to mixed plantations was noticeable from 1984 to 1990. Total upland area including upland area under shifting cultivation and upland fields with crops and vegetables only with fruit trees decreased from 21% in 1970 to 0.1% in 1990, clearly suggesting the establishment of plantation agriculture, mainly coffee plantations, in the hilly areas, and the transfer o...

Land use and cover changes in a Hilly Area of South Sumatra, Indonesia (from 1970 to 1990)

Changes in the activities of several soil enzymes due to land-use conversion from forests to cultivated lands in the middle terrace areas in Lampung Province, South Sumatra, Indonesia, were monitored. Soil samples were collected from 5 locations in the northern and northeastern regions of Lampung, each comprising several land-use systems (secondary forests, cacao plantations, pineapple plantations, rubber plantations, mixed gardens, cassava fields, corn fields, a rice field, etc.) depending on the distribution of the respective land-use systems at each location. Enzyme assays showed that, with a few exceptions, the activities of acid and alkaline phosphatases, beta-glucosidase, and arylsulfatase in the topsoils (0 to 20cm depth) were higher than, and well correlated with, those in the subsoils (20 to 40 cm depth). Activities of soil enzymes were in general well correlated with the content of total soil nitrogen. No distinct differences in enzymatic activities in soils were observed among the land-use systems. Among the soil enzymes studied, acid phosphatase activity showed a significant relationship only with alkaline phosphatase activity in the topsoils. In contrast, alkaline phosphatase activity showed a significant relation with the other enzymatic activities tested in the topsoils and with arylsulfatase and beta-glucosidase activities in the subsoils. Arylsulfatase activity also showed a high correlation with beta-glucosidase activity in both topsoils and subsoils

https://www.tandfonline.com/doi/pdf/10.1080/00380768.1999.10409326

Activities of soil enzymes in different land-use systems in middle terrace areas of Lampung province, South Sumatra, Indonesia

Kartahadimaja J, Utomo SD, Yuliadi E, Salam AK, Warsono, Wahyudi A. 2021. Agronomic characters, genetic and phenotypic diversity coefficients, and heritability of 12 genotypes of rice. Biodiversitas 22: 1091-1097. The achievement of national rice production is always below the target. One of the causes is the low productivity of the varieties grown due to the stagnant g enetic capacity of these varieties. The assembly of new lines through breeding is one solution that can increase the genetic capacity of new varieties. Genetic diversity is one of the factors that influence the success of plant breeding. Ten new F9 rice lines were s uccessfully assembled showing various phenotypes. The identification of the specific advantages of each of these new rice lines was based largely on the phenotypic response. The research objective was to identify the genetic advantages of each line through the analysis a pproach of genetic diversity coefficient (GDC), Phenotific Diversity Coefficient (PDC), and broad-sense heritability. The research was designed on a randomized completely block design (RCBD) with ten new F9 rice lines and two comparison varieties as treatments, repeated three times. The variables observed were plant height, maximum number of tillers, number of productive tillers, flowering time, harvesting time, panicle length, number of grain per panicle, number of filled grains per panicle, number of empty grain p er panicle, grain length, grain width, grain thickness, and grain yield per hectare. The data were analyzed using Analysis of Variance (ANOVA), if there was a difference between the mean values, it was continued with a 5% LSD test. The results showed that (i) the genotypes tested showed wide genetic and phenotypic diversity, (ii) based on the analysis of GDC, PDC, and broad sense heritability, the appearance of phenotypes of several agronomic characters was controlled by genetic factors.

Keywords: Agronomic characters, genetic diversity, heritability, phenotypic diversity, rice production

Abbreviations: GDC: diversity coefficient; PDC: phenotypic diversity coefficient

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Abdul Kadir Salam

Papers

The pH dependence of free ionic activities and total dissolved concentrations of copper and cadmium in soil solution

Activities of some soil enzymes in different land use systems after deforestation in hilly areas of West Lampung, South Sumatra, Indonesia

Land use and cover changes in a Hilly Area of South Sumatra, Indonesia (from 1970 to 1990)

Activities of soil enzymes in different land-use systems in middle terrace areas of Lampung province, South Sumatra, Indonesia

Agronomic characters, genetic and phenotypic diversity coefficients, and heritability of 12 genotypes of rice