Vegetation Reclamation Research Articles

Aboveground plant biomass drove the reclamation-year dependence of soil quality along a 49-year vegetation reclamation chronosequence

Aboveground plant biomass drove the reclamation-year dependence of soil quality along a 49-year vegetation reclamation chronosequence

The Potential of Recycling and Reusing Waste Materials in Underground Construction: A Review of Sustainable Practices and Challenges

Underground infrastructure projects pose significant environmental risks due to resource consumption, ground stability issues, and potential ecological damage. This review explores sustainable practices for mitigating these impacts throughout the lifecycle of underground construction projects, focusing on recycling and reusing excavated tunnel materials. This review systematically analyzed a wide array of sustainable practices, including on-site reuse of excavated tunnel material as backfill, grouting, soil conditioning, and concrete production. Off-site reuses explored are road bases, refilling works, value-added materials, like aggregates and construction products, vegetation reclamation, and landscaping. Opportunities to recover and repurpose tunnel components like temporary support structures, known as “false linings”, are also reviewed. Furthermore, the potential for utilizing industrial and construction wastes in underground works are explored, such as for thermal insulation, fire protection, grouting, and tunnel lining. Incorporating green materials and energy-efficient methods in areas like grouting, lighting, and lining are also discussed. Through comprehensive analysis of numerous case studies, this review demonstrates that with optimized planning, treatment techniques, and end-use selection informed by material characterization, sustainable practices can significantly reduce the environmental footprint of underground infrastructure. However, certain approaches require further refinement and standardization, particularly in areas like the consistent assessment of recycled material properties and the development of standardized guidelines for their use in various applications. These practices contribute to broader sustainability goals by reducing resource consumption, minimizing waste generation, and promoting the use of recycled and green materials. Achieving coordinated multi-stakeholder adoption, including collaboration between contractors, suppliers, regulatory bodies, and research institutions, is crucial for maximizing the impact of these practices and accelerating the transition towards a more sustainable underground construction industry.

Investigating the Efficiency of (Alhagi graecorum) Plant in Accumulating some Heavy Metals

This study aimed to investigate the efficiency of the alhagi plant in adsorbing and accumulating heavy metals in the plant that grows naturally on both sides of the highway extending between the cities of Diwaniyah and Baghdad, passing through the city of Hilla. Plants grow 50 meters away on the sides of the main highway. The results showed that the lead concentration in the shoot and root system was higher than the permissible limit. The highest lead concentration was in Baghdad’s soil, and the lowest was in Diwaniyah. It is attributed to the momentum and traffic density of the city of Baghdad. The cadmium concentration in the shoots was less than the permissible limit, while it was higher in the root shoots, and the highest concentration appeared in the soil of Baghdad city. The cadmium concentration was less concentrated than the rest of the studied elements, lead, zinc, and nickel. The results showed that nickel was less than the permissible limit in the vegetative and root system. The zinc concentration in shoots was higher than the permissible limit, except in the soils of Hilla and Diwaniya at the right and left sides, respectively, it was less than the permissible limit. As for its concentration in the root system, it was higher than the permissible limit, except for the soil of Al-Diwaniyah city on the right side. The concentrations of the studied elements in the root system were higher than in the shoot system. The results of the plant pollution standards showed that the values of the bio concentration factor and the bioaccumulation factor for all studied elements are less than the value of one, which means that the alhagi plant is not considered one of the plants that accumulate heavy elements. Therefore, it is of limited benefit for the vegetative reclamation of soils contaminated with the studied heavy elements, except for the zinc element, as its values were between 0.1-10, which indicates that the sedum plant is a moderate accumulation of the zinc element. The results also present that the values of the local transmission coefficient for all the studied elements are more significant than the value of one. It indicates the movement and transfer of all elements from the root to the vegetative system.

Microbial Community Structure and Predictive Functional Analysis in Reclaimed Soil with Different Vegetation Types: The Example of the Xiaoyi Mine Waste Dump in Shanxi

We explored the characteristics of soil bacterial communities and their ecological functions under different types of vegetation reclamation in open-pit mines on the Loess Plateau, which is the guiding significance for the selection of vegetation and the improvement of restoration effect in mining areas. The research object was to reclaim the soil of the aluminum mine waste dump in Xiaoyi County, Shanxi. The soil characteristics were measured under different types of vegetation reclamation. The soil bacterial community under different vegetation reclamation was measured using the 16S rRNA gene high-throughput sequencing technology. The ecological function was predicted using the PICRUSt method. The correlation between soil physical and chemical properties and bacterial community structure and function was analyzed. From the results, (1) the bacterial compositions of the reclaimed soil samples were 33 phyla, 90 classes, 121 orders, 207 families, 298 genera, and 140 species. The abundance and diversity of the soil microbial community showed the rule of yellow rose > lespedeza and sweet wormwood herb > alfalfa. (2) Proteobacteria were the dominant bacteria in alfalfa and sweet wormwood herb samples, accounting for 36.09–43.36%. Proteobacteria and actinobacteria were the dominant bacteria in the yellow rose and lespedeza samples accounted for 53.34–53.39%. α-Proteobacteria, actinobacteria, and β-proteobacteria were the dominant bacteria of the four vegetation types. The relative abundance of the α-proteobacteria and β-proteobacteria was positively correlated with soil organic carbon (SOC) and negatively correlated with soil total kalium (TK). Actinobacteria were positively correlated with available kalium (AK) and negatively correlated with SOC and total nitrogen (TN). (3) There was no difference in the primary functions of the soil bacterial community after the reclamation of different plants, and the main functions were metabolism, genetic information processing, and environmental information processing, with the function abundance accounting for 81.52%. (4) The abundance of functional genes in the metabolism of other amino acids, folding, sorting, and degradation and glycan biosynthesis and metabolism were relatively rich in the rhizosphere soil of yellow rose. The abundance of functional genes in signal molecules and interaction, transport, and catabolism in the rhizosphere soil of lespedeza was the highest. The abundance of functional genes in carbohydrate metabolism, translation, and energy metabolism in the rhizosphere soil of alfalfa was the highest. Therefore, there were significant differences in the structure and function of rhizosphere soil microbial communities among yellow rose, lespedeza, sweet wormwood herb, and alfalfa, and they were also affected by the soil properties. Hence, we concluded that the differences and diversity of soil microbial structure and function can help select plants for the sustainable development of soil remediation in mining areas.

Remote Sensing Monitoring of Vegetation Reclamation in the Antaibao Open-Pit Mine

After the regreening of the open-pit mine dump, vegetation usually needs to be managed and protected manually for several years before it reaches stability. Due to the spontaneous combustion of coal gangue, surface collapse, and other reasons, secondary damage may occur at any time. Regreening monitoring plays a vital role in the restoration and reconstruction of the mining ecosystem and can provide support for the timely replenishment of seedlings in the damaged area. In this study, remote sensing images were collected from 1986 to 2020 to obtain the NDVI distribution of dumps in the Antaibao open-pit coal mine. In order to obtain the overall growth law of regreening vegetation over time, the study adopted the unary regression analysis method and tested the correlation between NDVI and time by the Pearson correlation coefficient. However, through the Sen+Mann–Kendall trend analysis, it was found that there were differences in the trends of NDVI within the same dump. Next, by means of the Mann–Kendall mutation test and interactive interpretation, information, such as stable nodes of different regreening vegetation and vegetation growth patterns in degraded areas, were obtained. Through the above methods, the following conclusions were drawn: (1) The earlier the dumps were regreened, the more the areas were covered by significantly improved vegetation. In this study: 97.31% (the proportion of significantly improved vegetation in the south dump) >95.58% (the proportion in the west dump) >86.56% (the proportion in the inner dump) >79.89% (the proportion in the west expansion dump). (2) Different vegetation types have different time nodes for reaching stability. It takes about three years for wood, shrub, and a mix of grass, shrub, and wood to reach stability, but only one year for grass. (3) The destruction in mining areas is expansive and repeatable. Monitoring the growth patterns of regreening vegetation is conducive to understanding the reclamation effect, and provides a scientific basis for land reclamation planning and land management policies in the mining area. At the same time, the trend analysis method in this study can quickly extract problem areas after dump regreening and is applicable in most dumps.

Comparison of the Vegetation Index of Reclamation Mining Areas Calculated by Multi-Source Remote Sensing Data

Following vegetation reclamation in mining areas, secondary damage may occur at any time, especially in locations that have been mined for decades or even hundreds of years. Effective monitoring strategies are required to accurately assess plant growth and to detect the ecological effects of reclamation. Single satellite monitoring is often difficult to ensure vegetation monitoring needs, therefore multi-source remote sensing is preferred. Different sensor parameters and variation in spectral bands can lead to differences in the type of data obtained, and subsequently, methods for evaluating these differences are required for simultaneous sensor/band use. In this study, NDVI was selected to characterize the vegetation growth of the Antaibao Open-pit Coal Mine Dump by analyzing the correlation between different types of sensors (Landsat 8, HJ, Sentinel-2) and vegetation greenness in order to facilitate satellites’ replacement and supplement. Results show that: (1) Landsat 8 and Sentinel-2 satellite have a high relevance for monitoring the vegetation, but the correlation between these two sensors and HJ is relatively low, (2) the correlation between NDVI values varied by vegetation type, tree (R = 0.8698) > combined grass, shrub and tree (R = 0.7788) > grass (R = 0.7619) > shrub (R = 0.7282), and (3) the phenomenon of “Low value is high, high value is low” in the NDVI value with HJ satellite monitoring may have been caused by a weak signal strength and low sensitivity of the HJ sensor. Comparing the correlation of multi-source sensors to monitor the vegetation in the mining areas can be helpful to determine the alternative supplement of sensors through conversion formulas, which are helpful in realizing the long-term monitoring of dumps and detecting reclamation response in mining areas.

Efficiency of Vegetative Reclamation of Coal Spoil Heaps

Efficiency of Vegetative Reclamation of Coal Spoil Heaps

ЭКОЛОГИЧЕСКАЯ БЕЗОПАСНОСТЬ ФОРМИРОВАНИЯ ФИТОГЕННЫХ ПОЛЕЙ НА ТЕРРИКОНАХ УГОЛЬНЫХ ШАХТ

Objective of the study is to research peculiarities of phytogenic fields formation of natural and artificial plantations of shrub and ruderal vegetation on coal mining waste heaps within the Novovolynsk mining area (Ukraine). The biometric analysis of the growth of artificial plantations on tailings has been carried out applying forest inventory methodology, which involves laying temporary experimental areas, measuring the diameter of tree species at a height of 1.3 m, the total height of trees and the parameters of crowns. Variation was applied to study the spatial structure of vegetation on reclaimed and damped waste heaps. The models of artificial phytocenoses and ameliorants on waste heaps of coal mines, which are formed during forest reclamation, have been described. The paper presents an analysis of forest inventory characteristics of the crops phytocenosis on waste heaps. The spatial structure of phytogenic fields basing on variation of the most common species in natural and artificial plantations on waste heaps has been established. This allows us to select an assortment of species to conduct effective vegetative reclamation on the surface of tailings. The article presents result of studies on the formation of phytogenic fields on waste heaps of coal mines, which presuppose formation of aggregations. It has been proved that formation of phytogenic fields is inextricably connected with vegetative reclamation. The conducted research of the origin and distribution of phytogenic fields makes it possible to assess the degree of suitability of tailings for afforestation, regardless of the country in which they are formed. Research of phytogenic fields on tailings and waste heaps of coal mines will improve bioindication research methodology for studying forest crops on their surface and suggest innovative methods of handling. In particular, it is possible to raise the level of environmental safety and aesthetics of the devastated territories, and to reduce cost of vegetative reclamation.

Prospects of using drip irrigation for ecological conservation and reclaiming highly saline soils at the edge of Yinchuan Plain

Reclaiming saline soils at the edge of Yinchuan Plain is of paramount importance for ecological conservation. Therefore, efficiency of drip irrigation method was evaluated in a field experiment. The experiment using drip irrigation as reclamation method was carried out that included five soil matric potentials (SMPs) controlled at −5, −10, −15, −20 and −25 kPa (treatments S1–S5, respectively) directly under drip emitters at 20 cm depth. Measures including vegetation collocation, high-raised ridge and three-stage drip irrigation scheduling were adopted. Results showed that SMP thresholds significantly affected the spatial distributions of both electrical conductivity (ECe) and sodium adsorption ratio (SARe) based on extracts of saturated paste. The low salinity and SARe zones either kept enlarging or remained stable when SMP thresholds were above −20 kPa. However, for treatment S5(−25 kPa), these gradually shrank with time. By the end of the second year, the average ECe values in treatments S1–S5 were 2.05, 2.59, 3.36, 3.05 and 3.9 dS m−1, respectively, indicating that ECe increased linearly as SMP threshold decreased. The SARe showed the same trend, with corresponding values of 9.56, 10.48, 12.26, 12.82 and 15.23 (mmol L−1)0.5. The pH of the saturated soil extract (pHe) in all treatments increased from 7.64 to around 8.00 and was not significantly affected by treatments. Moreover, the two-year survival rates of the dominant trees were >87.5% when SMP threshold was above −20 kPa. The growth indexes of plants reduced with the decrease in SMP thresholds and statistical analysis suggested that −20 to −17 kPa was an important SMP range, below which the forage yield of the herbaceous legume Astragalus adsurgens dropped sharply. This study suggested the SMP threshold of −20 kPa was important for drip irrigation scheduling and the drip irrigation, combined with ridging plantation, was efficient for both vegetation reclamation and reclaiming saline soils in these saline areas with shallow ground water.

Environmental Impact of Devastated Landscapes of Volhynian Upland and Male Polisya (Ukraine)

Львівсько-Волинський вугільний басейн, розташований на території України у межах Волинської височини та Мале Полісся, є одним з найбільших у Європі. Метою нашого дослідження є висвітлення екологічного впливу спустошених ландшафтів вугільних шахт. Зразки едафотопів були зібрані відповідно до існуючих державних стандартів і затверджених методик. Встановлено, що зольність робочих і непрацюючих відвалів різна. Середній вміст золи в породі непрацюючих відвалів становить 79,95%, а в частинках діаметром до 13 мм - 78,22%. У діючих відвалах зольність вуглевмісних частинок є найменшою і коливається в межах 12,5-25,6% (середнє значення 20,08%). Середній вміст золи в діючих відвалах з розмірами частинок породи 1-13 мм становить 86,45%. Середній вміст золи в діючих відвалах з розміром частинок до 1 мм становить 72,25%. Для спонтанного пожежі найбільш відповідальні вугільні породи і породи з розміром частинок до 1 мм. Середній вміст сірки в породі непрацюючих відвалів становить 0,94%. Середній вміст сірки в експлуатованих відвалах з вугільними частинками 1-13 мм становить 1,86%. Найбільш небезпечними з точки зору вмісту сірки, які взаємодіють з іншими компонентами і хімічними елементами і мігрують у навколишнє середовище, є вуглевмісні частинки. Щоб подолати екологічний вплив породних відвалів вугільних шахт, зелені технології повинні бути впроваджені до непрацюючих відвалів. До таких технологій відносяться: біологічна рекультивація, у тому числі лісова і сільськогосподарська вегетативна рекультивація, і моніторинг навколишнього середовища в шахтах.

Spatio-temporal dynamics of vegetation in Jungar Banner of China during 2000–2017

It is known that the exploitation of opencast coal mines has seriously damaged the environments in the semi-arid areas. Vegetation status can reliably reflect the ecological degeneration and restoration in the opencast mining areas in the semi-arid areas. Long-time series MODIS NDVI data are widely used to simulate the vegetation cover to reflect the disturbance and restoration of local ecosystems. In this study, both qualitative (linear regression method and coefficient of variation (CoV)) and quantitative (spatial buffer analysis, and change amplitude and the rate of change in the average NDVI) analyses were conducted to analyze the spatio-temporal dynamics of vegetation during 2000–2017 in Jungar Banner of Inner Mongolia Autonomous Region, China, at the large (Jungar Banner and three mine groups) and small (three types of functional areas: opencast coal mining excavation areas, reclamation areas and natural areas) scales. The results show that the rates of change in the average NDVI in the reclamation areas (20%–60%) and opencast coal mining excavation areas (10%–20%) were considerably higher than that in the natural areas (<7%). The vegetation in the reclamation areas experienced a trend of increase (3–5 a after reclamation)-decrease (the sixth year of reclamation)-stability. The vegetation in Jungar Banner has a spatial heterogeneity under the influences of mining and reclamation activities. The ratio of vegetation improvement area to vegetation degradation area in the west, southwest and east mine groups during 2000–2017 was 8:1, 20:1 and 33:1, respectively. The regions with the high CoV of NDVI above 0.45 were mainly distributed around the opencast coal mining excavation areas, and the regions with the CoV of NDVI above 0.25 were mostly located in areas with low (28.8%) and medium-low (10.2%) vegetation cover. The average disturbance distances of mining activities on vegetation in the three mine groups (west, southwest and east) were 800, 800 and 1000 m, respectively. The greater the scale of mining, the farther the disturbance distances of mining activities on vegetation. We conclude that vegetation reclamation will certainly compensate for the negative impacts of opencast coal mining activities on vegetation. Sufficient attention should be paid to the proportional allocation of plant species (herbs and shrubs) in the reclamation areas, and the restored vegetation in these areas needs to be protected for more than 6 a. Then, as the repair time increased, the vegetation condition of the reclamation areas would exceed that of the natural areas.

PHYSICO-CHEMICAL PROPERTIES OF WASTEWATER FROM TECHNOLOGICAL WASTE DUMPS OF NOVOVOLINSK MINING DISTRICT

Introduction. Waste dumps of mine rocks of Novovolynsky mining area have high acidity, considerable content of various salts, namely sulfate ions. This high mineralization is caused by the movement to the water-collection points and the interaction of such water with rock dumps, and besides, on its way wastewater is enriched with products of rocks destruction (sulphates and salts of alkaline earth elements) and coal. Running through the abandoned places and accumulating mineral and mechanical impurities, such water gets new physical and chemical properties, which strongly influence the qualitative parameters of the environment.&#x0D; Analyzing the ecological situation caused by the wastewater pouring from technological dumps in mines № 2, 4, 9 on the investigated site it should be emphasized that at present, there is no storm sewer system on the investigated mines, therefore, rain water from the surfaces of waste heaps and industrial sites spontaneously flow down the lowlands and concentrate with mineral salts. Although it is known that there are considerable water influences in the main and preparatory mining operations, therefore, the collection of created waste water along the perimeter of existing waste heaps in the form of catchwater drains is made.&#x0D; Purpose. The purpose of the work is to investigate the physicochemical properties of wastewater from technological dumps in the Novovolynsk mining area.&#x0D; Methods. In this work chemical methods of wastewater analysis are used.&#x0D; Results. In all water samples, an increase in the content of ammonium salts was determined. As it is known, the main danger of pollution of the hydrosphere with ammonium salts is the saturation of water with ammonia. The content of ammonium salts above 0.1 mg/dm³ indicates pollution of water, since ammonia is the first compound formed during the decomposition of organic nitrogen-containing substances. Simultaneous presence of ammonia, nitrites and nitrates in samples of water shows a significant pollution of this water due to the oxidation of the rock in the dump and its washing-off with water. The increase in water samples of nitrite and nitrate content without the detection of ammonia indicates the isolation of the source of contamination. The content of ammonia and nitrite in water shows the constant source of pollution from the dumps. The presence of nitrates only indicates the end of mineralization processes. Excess ammonia in samples with the subsequent discharges into the river leads to ecological instability of the ecosystem in general, during the process of displacement of nitrogen-sensitive species, functional connections between all parts of the ecosystem (plants, animals, microorganisms) collapse, which leads to a violation of the self-regulation of the ecosystem. As a result of the conducted researches, significant differences in the physical and chemical composition of wastewater from the technological dumps of the Novovolynsk mining area were revealed. The chemical composition of wastewater of investigated mines is characterized by instability.&#x0D; Conclusion. Accumulation of toxic compounds in wastewater from technological dumps creates a significant man-made danger to the water resource potential of the state. It is also relevant to the wastewater contaminated with substances of the 2nd and 4th class of hazard, such as organic compounds of fluorine, nitrogen and radionuclide’s, which are one of the most dangerous for the hydrosphere. To prevent the hazardous effect of wastewater on the ecological state in the investigated area, it is necessary to use natural resources rationally, to conduct demineralization and remediation, vegetative reclamation of disturbed lands.

Reclamation of Technogenic Disturbed Landscapes of the Far North

The peculiarity of progressive succession in the damaged territories of the Yamburg gas condensate field is considered. It is established that the reclamation of technogenic disturbed landscapes is accelerated by the use of a complex of agro technical measures, including the selection of species of perennial grasses and the optimization of mineral nutrition. Studies carried out in the Yamburg gas condensate field in areas lacking of the biologically active layer have developed elements for soil and vegetation reclamation.

Фітомеліоративна ефективність вуличних фітоценозів як один із параметрів екологічного виміру збалансованого розвитку міста

Запропоновано введення параметра «коефіцієнт фітомеліоративної ефективності насаджень» у розрахунок індексу екологічного виміру збалансованого розвитку міської екосистеми. Проаналізовано особливості архітектурно-планувальної ситуації Львова. Визначено середньодобову інтенсивність руху автомобілів та вивчено фітомеліоративну роль насаджень вздовж вулиць Городоцької, Івана Франка та Євгена Коновальця. Визначено коефіцієнт фітомеліоративної ефективності насаджень вздовж транспортних магістралей, що дає змогу інформаційно доповнити екологічний складник виміру збалансованого розвитку міської екосистеми. Встановлено ступінь виконання фітомеліоративних функцій фітоценозів. Подано пропозиції щодо оптимізації рослинного покриву вулиць.

Effects of Vegetation Reclamation on Temperature and Humidity Properties of a Dumpsite: A Case Study in the Open Pit Coal Mine of Heidaigou

Vegetation cover greatly influences the microclimate of a landscape, which plays an important role in ecosystem function and health. The following study examines the influence of different vegetation types on the microclimate of a surface mine reclamation site. Average soil and air temperatures are significantly lower, while relative humidity is significantly higher in re-vegetated areas of a surface mine dumpsite in the Heidaigou. Vegetation recovery, particularly an increase in herbaceous vegetation cover, is expected to significantly reduce temperature and increase relative air humidity, improving the microclimate of the dumpsite in arid and semi-arid regions.

A floristic study on herbs and climbing plants at Puducherry, South India: an approach to biodiversity conservation and regeneration through eco-restoration

A qualitative floristic exploration with life form classifications and monitoring of flowering and fruiting phenology has been carried out at a restored site near Puducherry, South India in 2009 and 2010. The species were classified into three categories based on their occurrence status, namely, Naturally Occurring, Naturally Regenerated and Introduced. The present study focuses only on two life forms, the Herbaceous and the Climbing plants. The site selected for eco-restoration originally comprised of an eroded and severely degraded landscape with scattered remnant species. However, active human intervention over a thirty year period included the introduction of appropriate plant species and other physical measures to enhance soil fertility and ground water level, and regenerate and conserve the deteriorating typical Tropical dry evergreen forest (TDEF) vegetation. A large number of naturally ccurring herbaceous, climbing species (172) and a consistent number of naturally regenerated species (44) are now observed as a result of eco-restoration. Lowland herbaceous species have also established themselves as a green cover at ground level. At present, parts of the area have fertile soils and rich floristic composition with the herbaceous life form represented by 165 species encompassed in 105 genera and 37 families, and the climbing plants represented by 68 species belonging to 54 genera and 25 families. ‘Genus to family’ and ‘species to genus’ ratios indicate the establishment of diverse vegetation in the study site. Nearly one third of the species have been observed flowering throughout the year and about half of the species were observed fruiting throughout the year. We emphasize that the two fold approach of land and vegetation reclamation has been very effective in helping restore the unique TDEF vegetation at the local level and the same may be extended to help regenerate and conserve the Coromandel Coastal vegetation at the regional scale.

Vegetative bioremediation of calcareous sodic soils: history, mechanisms, and evaluation

Chemical amendments have been used throughout the world for almost 100 years to reclaim saline-sodic and sodic soils. Some amendments supply calcium (Ca2+) directly to the soil, which then replaces excess exchangeable sodium (Na+), while others help solubilize calcite (CaCO3) in calcareous soils. Chemical reclamation has become costly for subsistence farmers in developing countries. Amendment costs have increased because of greater usage by industry and reductions in government subsidies to farmers. Laboratory and field research, as well as farmers' experiences, have shown that calcareous sodic soils can also be reclaimed without the application of amendments through the cultivation of certain salt-tolerant crops. This vegetative reclamation strategy is generally known as bioremediation, phytoremediation, or biological reclamation. The principal contributing mechanisms include: (1) enhanced CO2 partial pressure in the root zone because of root and microbial respiration, which increases the solubility of calcite, and (2) improved soil physical properties due to root growth. Vegetative bioremediation can provide financial benefits from the crops grown which help to support farming operations; to some extent bioremediation is a "pay-as-you-go" option.