Spatial distribution pattern of degree–day factors of glaciers on the Qinghai–Tibetan Plateau

Glaciers have a very obvious feedback effect on the global water cycle and environmental change. The Qinghai–Tibetan Plateau, also known as the “Water Towers of Asia,” provides an important source of freshwater resources derived from glacial meltwater. Changes in glaciers on the Qinghai–Tibetan Plateau are the most important aspect of the research related to global climate change. Because only a few input parameters are available, the degree–day factor model of glacier mass balance has been widely used on the Qinghai–Tibetan Plateau. Study of the spatial distribution pattern of degree–day factors for glaciers on the Qinghai–Tibetan Plateau and the factors that influence glaciers is important scientifically. The study of degree–day factors is important to the calculation of the glacial grid mass balance on the Qinghai–Tibetan Plateau, and this data can be used in the analysis of the response of glaciers experiencing climate change and for predicting future glacial trends. Through an analysis of the degree–day factors related to 24 glaciers on the Qinghai–Tibetan Plateau, one can conclude that the mean value of glacial degree–day factors on the Qinghai–Tibetan Plateau is 8.14 mm day^?1 °C^?1. The glacial degree–day factor shows a longitudinal zonality with values ranging from high to low from east to west, a latitudinal zonality with values ranging from high to low from south to north, and a vertical zonal regularity along with the change of elevation. The spatial distribution pattern of glacial degree–day factors in the Tibetan Plateau is related to the fact that the climate environment across the Qinghai–Tibetan Plateau is mainly affected by the Indian monsoon, the eastern monsoon, and the westerly winds. The climate gradually changes from cold-humid to warm-humid from northwest to southeast. The single-unit glacier of Qinghai–Tibetan Plateau—the Renlongba Glacier—is located in the southeastern portion of the Qinghai–Tibetan Plateau in a warm and humid climate; its degree–day factor is slightly large, averaging at 6.12 mm day^?1 °C^?1. Mountainous barriers exist in the eastern and western parts of the Renlongba Glacier. On the east side, the degree–day factor is small (5.63 mm day^?1 °C^?1) because of large mountains block weather systems. The glacial tongue is affected by valley wind, contributing to glacial ablation, so the degree–day factor is large on the tongue, averaging at 6.56 mm day^?1 °C^?1. The degree–day factor on the west side of the Renlongba Glacier increases gradually increasing radiation and elevation, presenting a vertical zonal feature. In general, the climate of the Qinghai–Tibetan Plateau is mainly affected by the Indian and eastern monsoons and by westerly winds. In dry and cold climatic conditions, the glacial degree–day factor in the Tibetan Plateau is small, while at warm and humid climate conditions, it is large, with latitudinal, longitudinal, and vertical zonality. In addition, the degree–day factor is also affected by blocking, topography, and other local microclimatic conditions.     

Chemical speciation of inorganic pollutants in river–estuary–sea water systems

Monitoring studies and thermodynamic modeling were used to reveal the changes of inorganic chemical species of some water pollutants (nutrients and trace metals such as Fe, Mn, Zn, Cu, Cd and Pb) inthe river-estuary-sea water system. The case studies were two rivers, Kamchiya and Ropotamo, representing part of the Bulgarian Black Sea water catchment area, and having different flow characteristics. There were no major differences in inorganic chemical species of the two river systems. NO3(-) and NO2(-) chemical species showed no changes along the river-estuary-sea water system. Concerning phosphates six different species were calculated and differences between the three parts of the systems were established. The HPO4(2-) and H2PO4(-) species were found to be dominant in river waters. The H2PO4(-) species quickly decreased at the expense of HPO4(2-) and Ca, Mg and Na phosphate complexes in estuary and seawater. Trace metals showed a great variety of chemical species. Fe(OH)2(+) species prevailed in river waters, and Fe(OH)3(0) species--in sea waters. Me2+ and MeCO3(0) (Me = Cu, Pb) and PbHCO3(+) were dominant in river waters, while Cu(CO3)2(2-) and PbCl(-) species appear also in sea waters. Cd2+ species prevailed in river and estuary waters, and CdCln(2-n) (n = 1-3) species, in seawater. Free Zn2+ species predominated in all systems but downstream their percentage decreased at the expense of Zn phosphates, carbonates,sulfates and chlorides complexes. Only free Mn2+ species were dominant along the systems.     

3D Numerical Model of the Thermal Interaction Between Sediment–Water–Atmosphere

This paper describes a three-dimensional numerical model of heat flux using finite-difference approximation for the simulation, prediction, and visualization of sediment, water, and air temperature, applied in Villa del Mar saltmarsh, Bahía Blanca Estuary, Argentina. To make this computation, we develop an open-source software tool called Hemera 1.0 which is characterized by having little complexity and low hardware requirements. The model considers three heat transfer processes: diffusion, convection, and radiation, using bulk aerodynamic formulas as boundary conditions between the interfaces. The aforementioned model was applied for the month of January 2009. The model reproduced adequately the physical processes of the heat balance and showed an adequate response to changes in the boundary conditions. In addition, according to the model design, meteorological and oceanographic data and some soil properties are the only data input used for modeling. It is easily adaptable to other environments such us lakes and reservoirs, among others, in order to carry out similar studies.     

Modelling the Balance of Metals in the Amended Soil for the Case of ‘Atmosphere–Plant–Soil’ System

Changing the concepts of economic development and introducing new amendments can hardly decrease the accumulation in the soil of such pollutants as metals, remaining there for a long time. The predictive models for describing the balance of metals in the soil, which are based on the ‘atmosphere–plant–soil’ system and reflect the complicated physical–chemical nature of the metals’ migration, expressed by coefficients obtained in long-term observations in natural conditions, allow for evaluating long-term concentration of metals in the soil. The model BALANS evaluates self-purification of soil, taking into account the uptake of metals of aerogenic origin by the soil together with amendments, their physical–chemical migration and the type of microrelief determining its intensity as well as the absorbed biomass of plants and the removal of metals with crops. In this model, the half-period of metals’ washing out from the soil, found for the microrelief characteristic of low places, exceeds 200 years for Ni, Cr and Pb and makes 90 and 150 years for Zn and Cu, respectively.     

Evaluation by TCAM Model of Physical–Chemical Properties of Aerosol in Northern Italy

The chemical and size characterisation of aerosol in northern Italy was investigated by means of transport chemical aerosol model (TCAM) multiphase model long-term simulations performed within the frame of the CityDelta-CAFE exercise. The results show a high contribution of secondary inorganic compounds, in particular far from the Milan metropolitan area and in the large rural area of the Po valley where the major chemical fractions are ammonium and nitrates. The sulphate contribution is quite similar throughout this region, with the exception of areas close to SOx point emissions. Primary PM and organic compounds fractions, on the other hand, are greater close to major urban areas, in particular the Milan metropolitan zone. This work also presents a seasonal characterisation analysis of physical and chemical aerosol features. The results show that in winter, due to domestic heating emission of NOx and low temperatures, which favour the formation of secondary nitrate and organic aerosol, the PM10 and PM2.5 concentrations are higher than those in summer, in agreement with experimental data presented in several studies focussing on the same region.     

Study of personal–indoor–ambient fine particulate matters among school communities in mixed urban–industrial environment in India

A sampling program was conducted to investigate the formation of disinfection by-products (DBPs) and dissolved organic carbon (DOC) at two advanced water treatment plants in Kaohsiung City, Taiwan. The results in this study can be used as a reference for the operational control of water treatment plants and the setting of regulations in Taiwan. Samples of drinking water were collected from two advanced water treatment plants from June 2007 to April 2008. Changes in the concentration of dissolved organic carbon, the trihalomethane formation potential, and the haloacetic acids formation potential were measured in raw water samples. Variations in the concentrations of trihalomethanes (THMs) and haloacetic acids (HAA₅) in finished drinking water were evaluated. The major species of HAA₅ were in the order of dichloroacetic acid and trichloroacetic acid and the THM was of trichloromethane. DOC was strongly related to DBPs in raw water. In this investigation, the removal efficiency of DBPs in Plant A (ultrafiltration/reverse osmosis system) exceeded that in Plant B (ozonation/biological activated carbon system). Both advanced water treatment plants greatly improved the quality of drinking water.     

Modelling of a Capillary Rise Height of Biochar by Modified Lucas–Washburn Equation

Environmental Modeling & Assessment - Lucas–Washburn equation is a fundamental expression which is used to describe capillary rise in porous materials according to average pore radius,...     

An Assessment of the Ecological Condition of Long Island Sound, 1990–1993

Data from the Environmental Protection Agency's (EPA) Environmental Monitoring and Assessment Program (EMAP) from 1990 to 1993 were used to assess the condition of the Long Island Sound (LIS) estuary. Ambient water, sediment and biota were collected during the summer months from 53 LIS stations using an unbiased sampling design. The design consists of two LIS subunits, LIS proper, and small estuaries (<2.6 km2) at the margins of the Sound. Selected indicators of condition included: benthic species composition, abundance and biomass; fish species composition and gross external pathology; sediment physical and chemical characterization and sediment toxicity; and water clarity and quality. Results of the four-year sampling indicated that 28(±11)% of the areal extent of LIS proper had a benthic index < zero (impacted) and 51(±12)% of the area of small estuaries was impacted. Analysis of the results of other indicators also shows that small estuaries were particularly affected. For example, 42(±10)% of the areal extent of small estuaries exhibited sediment toxicity, and significant chemical contamination was evident in 22% of the area of small estuaries. Low dissolved oxygen (D.O.) concentrations (<5 ppm), however, appeared to affect only the deeper open waters of western LIS. Approximately 48(±12)% of the areal extent of LIS proper documented exposure to at least moderate D.O. stress (<5 ppm). The overall results of this monitoring study indicate that significant anthropogenic impacts have occurred in LIS and that if remediation was to take place, specific localized sediment problems would need attention. Point source and non-point source nutrient inputs to the Sound, which are believed to be the primary causative factor for the observed hypoxic conditions, would also need attention.     

Exposure Modeling of Benzene Exploiting Passive–Active Sampling Data

The objective of the present study is the exploitation of active sampling personal exposure data in assessing the factors that affect exposure to benzene in combination with the widely accepted scheme of passive sampling—time microenvironment–activity diaries (TMAD). The campaign included personal exposure measurements with both passive and active sampling in several microenvironments, evaluation of TMAD kept by the volunteers, and a variety of environmental data (ambient air benzene determination, traffic and meteorological observations). Due to the relatively elevated benzene traffic emissions, average personal exposure was determined to be equal to 8.9 μg/m³, ranging between 5 and 20 μg/m³, which is a value highly related to the average urban concentration (9.2 μg/m³). The information gained from TMAD was embedded (in terms of spatial and temporal distribution) into three zones respectively, in order to draw statistically significant conclusions about the exposure levels and the activity patterns. The contribution of the activities to the overall amount of exposure was further quantified and refined by active sampling measurements. These data revealed that driving in a traffic-congested road was the main activity leading to elevated exposure levels (up to 70 μg/m³), followed by walking on the roadside of a congested road (up to 35 μg/m³). Indoor exposure to benzene was in general lower than outdoor (indicating that traffic is the dominant source of benzene emissions in the wider area), and it was significantly affected by the presence of environmental tobacco smoke. The higher significance of the regression coefficients obtained by statistical analysis of the active sampling data was fundamental for the development of a regression-based prediction exposure model. The model was evaluated through comparison with the passive sampling data, which were considered as an unknown but realistic data exposure pattern. The model performed very well in terms of expressing the variance of the exposure data with an average score of R ² equal to 0.935. All of the above indicate that active sampling is a necessary albeit more laborious tool that needs to be used as a complement to passive sampling for precise quantification of the factors determining personal exposure patterns.     

Speciation of mercury in mine waste: case study of abandoned and active gold mine sites at the Bibiani–Anwiaso–Bekwai area of South Western Ghana

Speciation determines toxicity, transport pathways and residence time of a metal in different compartments of the environment. This study investigated the speciation of mercury in soils, derived from sites known for dumping of mine wastes in the Bibiani–Anwiaso–Bekwai district, a gold mining community of the Western Region of Ghana. Soil samples were taken from the surface; depths of 20, 40 and 60?cm from mine waste at both abandoned and active mine sites. Each sample was analysed for total mercury, organic mercury and elemental mercury. After sample treatment, digestion and reduction with stannous chloride (SnCl₂), total mercury content was determined using the Inductively Coupled Plasma—Optical Emissions Spectrometer (ICP–OES). Organic mercury content was determined employing a differential technique after disposing of elemental mercury by heating. Total mercury content in samples ranged from 0.067 to 0.876?mg/kg for surface soils. The same soil of depths 20, 40 and 60?cm had total mercury from 0.102 to 1.066, 0.037 to 4.037 and 0.191 to 4.998?mg/kg, respectively. For organic mercury, concentrations range from 0.012 to 0.260?mg/kg for surface soil. Soil depths of 20, 40 and 60?cm had organic mercury concentrations from 0.016 to 0.653, 0.041 to 1.093 and 0.101 to 2.546?mg/kg respectively. Elemental mercury concentrations in surface soils, soils at depths of 20, 40 and 60 cm ranged from 0.043 to 0.780; 0.017 to 0.749; 0.014 to 2.944 and 0.009 to 2.452 mg/kg respectively. Among the sites studied, only galamsey tailings (GM) showed a trend of increasing total mercury level with increasing depth. For the other sites, trends were not defined. There has been no defined trend for elemental mercury with depth at any of the sampling sites. Just as with total mercury, it was only GM that showed an increasing trend of organic mercury concentration with depth.     

Geochemical behavior of heavy metals in a Zn–Pb–Cu mining area in the State of Mexico (central Mexico)

The geochemical behavior of zinc, lead and copper from sulfidic tailings in a mine site with potential to generate acidic drainage (pyrite (55%) and sphalerite (2%)) is reported in this paper. The mining area is divided in two zones, considering the topographic location of sampling points with respect to the tailings pile: (a) outer zone, out of the probable influence of acid mine drainage (AMD) pollution, and (b) inner zone, probably influenced by AMD pollution. Maximum total ions concentrations (mg/L) measured in superficial waters found were, in the outer zone: As (0.2), Cd (0.9), Fe (19), Mn (39), Pb (5.02), SO4(2-) (4650), Zn (107.67), and in the inner zone are As (0.1), Cd (0.2), Fe (88), Mn (13), Pb (6), SO4(2-) (4,880), Zn (46). The presence of these ions that exceeding the permissible maximum limits for human consume, could be associated to tailings mineralogy and acid leachates generated in tailings pile.     

Analysis of spatial–temporal distributions of nitrate-N concentration in Shitoukoumen catchment in northeast China

This article discusses the generation and migration process of nitrate-N pollution in shallow groundwater caused by agricultural nonpoint source pollution in the catchment area of Shitoukoumen Reservoir in northeast China. By monitoring the shallow groundwater nitrate-N in the low-water period, the normal season, and high-flow period in the study area for a year, it was found that the nitrate-N concentration in the shallow groundwater of this area had a seasonal variation in both spatial and time distribution. In the time distribution, the peak value appeared in July, the high-flow period, and the valley value appeared in April, the low-water period, and showed a significant correlation with the time distribution of fertilization rate and rainfall. In the spatial distribution of nitrate-N pollution, when the distribution in shallow groundwater was analyzed separately in the three different periods (low-water period, the normal season, and high-flow period) and the discipline transference and enrichment of nitrate-N pollution in shallow groundwater was determined, this indicated that the region in the southeast study area where runoff conditions were better was less contaminated, and the region where runoff conditions were poor, as well as the region along the river were seriously polluted. The nitrate-N concentration in shallow groundwater was distributed mainly along the path of groundwater flow and was excreted in the drainage region. This showed that the spatial distribution of nitrate-N concentration in the shallow groundwater of the entire region was mainly controlled by the groundwater flow system. At the same time, in the middle and lower reaches of the study area, the seasonal changes in the recharged–excreted relationship between groundwater and river caused seasonal differences in the spatial distribution of nitrate-N pollution in groundwater. The combined effects of the groundwater mobility and the surface river resulted in a poor correlation between the groundwater nitrate-N concentration and land-use types. Only in the plain area where there was little influence from groundwater runoff and the surface river did the groundwater nitrate-N concentration correlate with land-use types. The spatial and time distribution of nitrate-N concentration in the shallow groundwater of the study area was impacted by agricultural nonpoint source pollution, the groundwater flow system, and the surface river and formed a concentration response system which uses basins as a unit.     

Analysis of acidic components, heavy metals and PAHS of particulate in the Changwon–Masan area of Korea

This study is an analysis of the concentrations and components of heavy metals in PM_2.5 and the total suspended particulate (TSP) collected at a mechanical industrial complex (IC) site in Changwon and at a residential site in Masan, Korea. Particulate was collected during two sampling periods, from the late summer to the early fall and from the middle to late fall, at the IC site and one sampling period, from the middle fall to the early winter, at the residential site. PM_2.5 and TSP samples were taken by an annular denuder system and a hi-volume air sampler, respectively. The authors also identified the concentrations and components of heavy metals extracted from the PM_2.5 and TSP filters, the acidic components extracted from the PM_2.5 filters, and the polycyclic aromatic hydrocarbons (PAHs) extracted from polyurethane foam (PUF) plug. The average concentrations of the PM_2.5 collected at the IC and residential sites were very similar. Major sources of PM_2.5 at the study sites, however, were air emissions from vehicles and industry as well as emissions from residential heating and soil origins, respectively. The higher concentrations of the TSP at the IC site, as compared to those at the residential site, were due to either increased suspended dust from vehicle emissions or re-suspended road dust because of increased vehicle speeds near the IC site. Heavy metal concentrations in the TSPs were higher than those in the PM_2.5. The heavy metal concentrations in the PM_2.5 and TSP at the IC site with heavy traffic were substantially greater than those at the residential site. The concentrations of TSP and heavy metals and PAHs in PM during the period of the middle to late fall was much higher than those during the period of the late summer to early fall at the IC site. This is because of the difference in meteorological characteristics and energy uses between two periods. The residential site also showed higher concentrations of acidic anions while the IC site showed higher concentrations of acidic cation. Secondary aerosols or particulates, such as ammonium nitrate or ammonium nitrite, might have been important constituents of the PM_2.5 at the residential site. The PAHs in the TSP collected at the IC site was greatly affected by traffic and industry emissions consisting mostly of high molecular weight PAHs with two to four rings. PAHs in the TSP at the site, however, were affected by residential heating and air emissions from small chemical plants having higher concentrations of low molecular weight PAHs with five to six rings.     

Time trend of Butyl- and Phenyl-Tin contamination in organisms of the Lagoon of Venice (1999–2003)

In the period 1999-2003 a monitoring study on the accumulation of organotin compounds in edible organisms in the Lagoon of Venice was conducted. Butyl and Phenyl derivatives were determined in pooled samples of Mytilus galloprovincialis and Tapes spp. with the aims of assessing organotin contamination in the Lagoon of Venice in the period just preceding their ban in Europe, monitoring the concentrations in organisms with a high commercial use, evaluating a potential hazard for human health due to seafood and identifying the possible contamination sources. Sampling stations (up to 20) were distributed around the Lagoon and particularly concentrated in the area close to the town of Chioggia. Significantly higher (analysis of variance (ANOVA), p < 0.05) tributyltin (TBT) concentrations were found in mussels (from 38 +/- 8 to 6,666 +/- 1,333 microg kg(-1) d.w., as TBT(+)), than in clams (from 6 +/- 1 to 2,256 +/- 451 microg kg(-1) d.w., as TBT(+)). During the 3 years of the survey no increase in average concentrations of the butyltin compounds (tributyltin (TBT) + dibutyltin (DBT) + monobutyltin (MBT)) was observed (ANOVA, p > 0.05) in either species. Furthermore, by analyzing the entire data set, it is evident that most stations show analogous concentrations in the 3 years for both species, whereas few have anomalously higher concentrations. If organotin concentrations in specimens from some sites are compared with the Tolerable Average Residue Level, a possible risk for human health must be considered.     

The long time scales of the climate–economy feedback and the climatic cost of growth

This paper is based on the perception that the inertia of climate and socio-economic systems are key parameters in the climate change issue. In a first part, it develops and implements a new approach based on a simple integrated model with a particular focus on an innovative transient impact and adaptation modeling. In a second part, a climate–economy feedback is defined and characterized. The following results were found. 1) It has a long characteristic time, which lies between 50 and 100 years depending on the hypotheses; this time scale is long when compared to the system's other time scales, and the feedback cannot act as a natural damping process of climate change. 2) Mitigation has to be anticipated since the feedback of an emission reduction on the economy can be significant only after a 20-year delay and is really efficient only after at least 50 years. 3) Even discounted, production changes due to an action on emissions are significant over more than one century. 4) The methodology of the Intergovernmental Panel on Climate Change (IPCC), which neglects the feedback from impacts to emissions, is acceptable up to 2100, whatever is the level of impacts. This analysis allows also to define a climatic cost of growth as the additional climate change damages due to the additional emissions linked to economic growth.

Estimation of riverine loads of nitrogen and phosphorus to the Baltic Sea, 1970–1993

This article presents the results of the first critical examination of time series of riverine nutrient-load data for the entire Baltic Sea drainage area. Water quality data collected by or for the different national environmental agencies were compiled and analysed statistically to identify and remove inconsistent or obviously incorrect observations. Moreover, sampling tours were undertaken to acquire additional information about the present nutrient concentrations in the largest rivers in the study area. Gaps in the time series of approved data were then filled in by employing statistical interpolation and extrapolation methods. Thereafter, the concentration and runoff data were combined to obtain estimates of monthly nutrient loads for the time period 1970–93. The results of the calculations showed that although there had been substantial changes in land use, atmospheric deposition and wastewater treatment in many parts of the study area, the total riverine loads of nitrogen (N) and phosphorus (P) to the Baltic Sea have been fairly constant since 1980, and most likely also since 1970. Moreover, the interannual variation was clearly correlated to the runoff. The mean annual loads for the time period 1980–93 were found to be about 825 000 tonnes N and 41 000 tonnes P, respectively. This implies that (i) several other investigators have strongly underestimated the riverine loads of nutrients, especially the nitrogen, and that (ii) the riverine loads by far exceed the input to the Baltic Sea from other sources, {i.e.} atmospheric deposition, direct emissions from cities and industries along the Baltic Sea coast and nitrogen fixation by marine algae.     

Levels of Heavy Metals in Karelian Wildlife, 1989–91

The levels of mercury, cadmium, lead, copper, nickel, zinc and iron were determined in samples of liver, kidney, skeletal muscle, heart, lungs and hair of moose (N = 67), reindeer (N = 45), brown bear (N = 18), wild boar (N = 10) and squirrel (N = 18) shot in Karelia from 1989 to 1991 during regular hunting. The highest heavy-metal concentrations were found in livers, kidney, lungs and hair samples. The samples of muscle contained lowest levels of these elements. The tissues of moose, reindeer and brown bear were contaminated with heavy metals to a greatest extent. Lowest levels of toxicants were recorded in wild boar. Results indicate a widespread presence of heavy metal in the environment and in wildlife, which may be linked to acid precipitation. There was no evidence of these elements accumulated to toxic levels, but Karelian public have been informed that the eating of moose liver and kidney would probably result in their exceeding WHO standard weekly intake limit for cadmium.     

Assessment of flood-induced changes of phytoplankton along a river–floodplain system using the morpho-functional approach

In this research, we aimed to find out how the differences in hydrological connectivity between the main river channel and adjacent floodplain influence the changes in phytoplankton community structure along a river–floodplain system. The research was performed in the River Danube floodplain (Croatian river section) in the period 2008–2009 characterised by different flooding pattern on an annual time scale. By utilising the morpho-functional approach and multivariate analyses, the flood-derived structural changes of phytoplankton were analysed. The lake stability during the isolation phase triggered the specific pattern of morpho-functional groups (MFG) which were characterised by cyanobacterial species achieving very high biomass. Adversely, the high water turbulence in the lake during the frequent and extreme flooding led to evident similarity between lake and river assemblages. Besides different diatom species (groups of small and large centrics and pennates), which are the most abundant representatives in the river phytoplankton, many other groups such as cryptophytes and colonial phytomonads appeared to indicate altered conditions in the floodplain driven by flooding. Having different functional properties, small centric diatom taxa sorted to only one MFG cannot clearly reflect environmental changes that are shown by the species-level pattern. Disadvantages in using the MFG approach highlight that it is still necessary to combine it with taxonomical approach in monitoring of phytoplankton in the river–floodplain ecosystems.     

Adsorption–desorption of metolachlor and atrazine in Indian soils: effect of fly ash amendment

The effect of two fly ashes as soil amendment on the adsorption–desorption of metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylphenyl)] and atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) was studied in alluvial and laterite soils. The adsorption data for both the herbicides fitted well the Freundlich equation, and Freundlich adsorption coefficient (K _f) increased with an increase of fly ash amount. Both the fly ashes differed in their extent to increase herbicide sorption, and the effect was different in different soils. Atrazine was sorbed more in the soils/soils?+?fly ash mixtures than the metolachlor. The K _f values showed significant correlation with the amount of fly ash amendment (correlation coefficient, R?>?0.982). The desorption isotherms also fitted the Freundlich equation, and desorption showed hysteresis which increased with an increase in the content of fly ash amendment. The free energy change (ΔG) indicated that the sorption process is exothermic, spontaneous, and physical in nature. The study has shown that fly ash as soil amendment significantly increased the sorption of metolachlor and atrazine, but the effect is soil- and fly ash-specific.