Ecological chemical characteristics of deicing materials and technology of their safe application

Industrial city ecology is determined with all region condition. For cities there are definite critical indicators of pollution volumes (so called – ecological capacity), at crossing them the processes of various deformation and instabilities appear. One can speak about critical characteristics for atmosphere, open and underground aquatic medium, soil, green planting, industrial zones, waste dumps, public health.

The necessity to provide the functioning in the atmospheric precipitation conditions at negative temperatures of the environment in winter period appears. It is known that snow cover accumulates the considerable part of atmospheric contaminations; it is an indicator of environmental footprint on the environment. One uses different reagents to struggle with winter snow cover and road slippery surface.

Fresh snow with applied sandy salt mixture is compacted significantly slower and is rolled to vehicles wheels then pure snow. It was proved experimentally that slowing down the process of compacting and rolling of snow is obtained due to the presence of chlorides in sandy salt mixture. Such deicing chemical agents as sodium chlorides, calcium chlorides, magnesium chlorides and potassium chlorides got the widest application. According to their composition they can be homogeneous or mixed in different proportions. These reagents application into snow provides its density increase because at the contact with reagents part of snow changes into solution. This results in snow volume decrease.

Deicing reagents that are used for road processing in winter period are certified and they do not harm populated area ecology.

The list of deicing materials includes - deicing reagents (hard, combined and liquid), and also friction deicing materials, corresponding to the main requirements to the composition and properties. Deicing reagents (DR) are hard (granular), combined (combination of hard chemical and friction components), and also liquid (solutions) chemical artificial means, distributed on the surface of road cover to struggle with winter slipperiness (prevention of its formation and liquidation) by means of interaction with snow-ice depositions. The possibility to support in the admissible state elements Road Facilities Object

(RFO) in the process of their exploitation in winter period is provided with ice (snow) melting and formation of water solutions DR (salts), with freezing temperature lower than water freezing temperature (Table 1).

Friction materials (deicing) - hard, granular, insoluble (slightly soluble) in water materials, distributed along the surface of road covering to liquidate winter slippery formation by means of increase of adhesion coefficient of wheels of vehicles as a result of increase of roughness of snow ice depositions.

Combined materials (combined DR) are hard (granular) means having in their composition chemical deicing reagents (DR), and friction materials.

Liquid reagent is base on calcium chloride and sodium chloride, mass fraction of soluble salts, % (concentration), in the range of 27-29%: calcium chloride – in the range of 22-23%, sodium chloride in the range of 5-6% correspondingly (ХКНж.).

Hard DR is hard polycomponent deicing reagent on the base of composition of calcium chloride with other chlorides (sodium and potassium) and sodium formate: mass fraction of calcium chloride is not less than 20%; sodium chloride is not more than 75%; calcium chloride – not more than 20%; sodium formate – not less than 5% by mass correspondingly (МРКтв.).

Table 1 - Main requirements to chemical deicing reagents

Indicator name	Standard
	Hard                  1	Liquid
Organoleptic:
1. External view	Granulars, crystals, scale	Water solution without mechanical inclusions, sediment and suspension
2. Color	From white to light-grey and lightbrown	Light, transparent (permitted with understaining of yellow or blue color)
3. Smell	Absent	Absent
Physical chemical:
4. Granular content, %, mass fraction of particles of size:
- more than 10 mm	Not permitted
- more than 5 mm to 10 mm included, not more	10
- more than 1 mm to 5 mm included, not more	75
- 1 mm and less, not more	15
5. Mass fraction of soluble salts, % (concentration), in the limits	-	27-29
6. Crystallization temperature, C, not higher	-10	-10
7. Humidity, %, not more	5	-
8. Mass fraction of water insoluble matters, %, not more	2	-
9. Hydrogen index, units (pH)	5-10	5-10
10. Density, g/sm 3	0,8-1,15	1,1-1,3
11. Dynamic viscosity, centipoise, (kg x s)/m 2, not more	4	5
Technological:
12. Melting capacity, g/g, not less	5	2
13. Hydroscopy, %/day.	not more 50	-
14. Slumping	Not permitted	-
Ecologic:
15. Specific effective activity of natural radionuclides, Bk/kg, not more	370	370
16. Corrosion activity for metal (St3), mg/sm 2 x day, not more	0,8	0,8
17. Indicator of cement concrete aggressiveness, %, not more	0,5	0,5

Hard polycomponent deicing reagent on the base of composition of calcium chloride and sodium chloride: mass fraction of calcium chloride is not less than 20%; mass fraction of sodium chloride – not more than 80% by mass correspondingly (ХКНтв.)

Hard polycomponent deicing reagent on the base of composition of calcium chloride with other chlorides (sodium and potassium) and sodium formate: mass fraction of calcium chloride is not less than 15%; sodium chloride - not more than 80%; potassium chloride - not more than 10%; sodium formate - not less than 5% by mass correspondingly (МРтв.).

Friction materials (auxiliary) include: small granite macadam with fraction 2-5 mm, which is considered as ПГМ for definite weather conditions in the traffic way (Table 2).

Table 2 - The basic requirements to friction deicing materials

Indicator name	Standards
1. Granular content, %, mass fraction of particles of size:
- more than 10 mm	Not permitted
- more than 5 mm to 10 mm, not more	5
- more than 1 mm to 5 mm, not less	80
- 1 mm and less, not more	15
2. Mass fraction of dusty and clay particles, %, not more	3
3. Mass fraction of clay in clods, %	Not permitted
4. Hardness grade, not less	600
5. Humidity, %, not more	5
6. Specific effective activity of natural radionuclides, Bk/kg, not more	740

Combined material DR is hard combined deicing reagent on the base of composition of calcium carbonate (crushed marble) and sodium formate (formiate): mass fraction of calcium carbonate is 50-80%; sodium formate - 20-50% by mass correspondingly (КР1тв.) (Table 3).

Table 3 - The basic requirements to the combined deicing reagents

Indicator name	Standards
	Combined DR
1. Granular content, %, mass fraction of particles of size:
- more than 10 mm, not more	Not permitted
- more than 5 mm to 10 mm, not more	60
- more than 1 mm to 5 mm, not less	20
- 1 mm and less, not more	20
2. Friction (insoluble) part in the content of DR	crushed marble
3. Granular content of friction (insoluble) parts in the content of DR, %, mass fraction of particles of size:
- more than 10 mm, not more	Not permitted
- more than 5 mm to 10 mm, not more	60
- more than 2,5 mm to 5 mm, not less	25
- 2,5 mm and less, not more	15
- content of grains of plate and	35
needle-shaped form, not more
4. Mass fraction of dusty particles in friction (insoluble) part in the content of DR, %, not more	3
5. Hardness grade of friction (insoluble) part in the content of DR, not less	200
6. Mass fraction of insoluble in water matters (except crushed marble), %, not more	2
7. Color	From white to light-grey and light-brown
8. Smell
9. Humidity, %, not more	absent
10. Hydrogen index, units (pH)	5-10
11. Specific effective activity of natural radionuclides, Bk/kg, not more	370
12. Slumping	Not permitted
13. Corrosion activity for metal (St3), mg/sm 2 x day, not more	0,8
14. Indicator of cement concrete aggressiveness, %, not more	0,5

Hard combined deicing reagent on the base of composition of calcium carbonate (crushed marble), and sodium formate (formiate) and sodium chloride (eadible salt): mass fraction of calcium carbonate is 20-50%; sodium formate - 10-30%; mass fraction of sodium chloride – not more than 60% by mass correspondingly (КР2тв.).

Hard combined deicing reagent on the base of composition of calcium carbonate (crushed marble), sodium formate (formiate) and sodium chloride (eadible salt) with addition of chlorides (calcium and potassium): mass fraction of calcium carbonate is 20-50%; sodium formate - 10-30%; mass fraction of sodium chloride - more than 50%; mass fraction of chlorides (calcium and potassium) – not more than 20% by mass correspondingly (КР3тв.).

In the frames of state contracts state clients must carry out quality control of deicing materials DM (Table 4).

Table 4 - Permitted content of chemical substances, that do not belong to active substance in the content of DR

N	Chemical indicator name, form	Permitted content of chemical indicator in the content of hard DR (mg/kg)	Permitted content of chemical element/indicator in the content of liquid DR (mg/l)
1	2	3	4
1	Fluorine, water soluble form	Not more than 25,0	Not more than 25,0
2	Zinc, total content	Not more than 198,0	Not more than 66,0
3	Plumb, total content	Not more than 65,0	Not more than 21,0
4	Nickel, total content	Not more than 70,0	Not more than 23,0
5	Cuprum, total content	Not more than 117,0	Not more than 39,0
6	Mercury, total content	Not more than 2,0	Not more than 0,66
7	Molybdenum, total content	Not more than 20,0	Not more than 6,6
8	Cobalt, total content	Not more than 6,0	Not more than 2,0
9	Cadmium, total content	Not more than 2,0	Not more than 0,66
10	Chrome, total content	Not more than 150,0	Not more than 50,0
11	Selenium, total content	Not more than 3,0	Not more than 1,0
12	Arsenic, total content	Not more than 10,0	Not more than 3,3

The sphere of control measures includes obligatory constant, systematic estimation of quality of deicing materials (incoming control), their technological and ecologic characteristics, including chemical content, physical and chemical, physical and radio ecologic indicators. Duration of carrying out the incoming control of the set DM must not exceed 5 (five) working days from the moment of sampling. Sampling must be done monthly not later than 3 (three) working days after the supplier finishes the shipment of the month volume DM according to delivery schedule which is the State contract supplement. It is possible to analyze the DM at the expense of the supplier in some other specialized certified in accordance with procedure established by law laboratories. The laboratories where the quality control is carried out must be certified by the dedicated federal agency of control and supervision in the sphere of environment and ecosystem exploitation.

After passing the procedure of the State Environmental Review of the Federal level and the presence of approved in the established procedure of positive opinion the present technology can be applied in the winter management system of RFO. Control over the implementation of the present technology is executed by the designated authority in the sphere of the environmental protection of the federal level.

Technology and treatment procedure of road covering with deicing materials:

• -    To treat the traffic way of RFO (primary – before snowfall start and basic during carrying out snow clearing activities) one uses hard and liquid DR, which is necessary to

distribute observing strictly the set standard of road covering treatment for one technological cycle. The hard deicing reagents are used as the basic deicing reagents.

• -    Small granite macadam of fraction 2-5 mm is considered as basic or additional deicing material at definite weather conditions on the traffic way. On the pavements, house areas, public transport stops to eliminate the winter slippery only the application of combined DR is permitted.

• -    The traffic way treatment with liquid DR must be carried out by special machines of type «МКДС-2204» (or similar technique), with automatic control of distribution.

• -    The traffic way treatment with hard deicing reagents must be done with the machines of type «КУМ-5551», equipped with the system of automatic control of distribution.

• - The treatment with granite macadam of fraction 2-5 mm and combined DR is done with machines of type «КУМ-5551», and machines of type «ПР-1».

• -    The extension of the prior treated zones of slowing down before crossings, above ground pedestrian crossings, traffic control posts is set for roads with maximum legal speed up to 60 km/h – not less than 150 m, for roads with maximum legal speed more than 60 km – not less than 200 m. To do these technological operations is necessary to keep machines-reagent distributors loaded with DR in the amount sufficient for all attached area treatment.

• -    Deicing reagents DR, distributed on the traffic way surface according to the present technology mixed with snow by the moving transport wheels, during the definite time (up to 3 hours), keep on the road snow pack in loose condition and prevent its rolling to road covering surface.

• -    At mechanized sweeping the treated with reagents snow layer is easily removed from traffic way by plows and brushes of sweeping machines.

If one gets the forewarning about icy sports genesis danger from meteorological authority full treatment of traffic way must be done before the beginning of ice-forming phenomena. When you get warning about possible transfer of air temperature via 0 °C to the negative meanings and possible formation of icy sports (ice film, glassy ice), particularly at night time, preventive DR treatment must be done. It need not be accompanied with sweeping of the traffic way in case of atmospheric precipitation absence. This technological operation is done by order of the strategic city main office. Consumption rates correspond to minimum values for temperature range from 0 to -2°C. At receiving warning about possible glaze formation in the periods of the most intensive movement of vehicle and atmospheric precipitation presence, as a rule, at the day time the DR preventive treatment must be done before traffic way sweeping. This technological operation is done by order of the strategic city main office. At obtaining the forewarning about snowfall from meteorological authority before precipitation the primary DR treatment of the most dangerous for vehicle movement areas of RFO (steeps and up-hill gradients, bridges, overpasses, tunnels, stop ways, etc.) must be done. At snowfalls up to 3 sm: full DR treatment of traffic way is done before snowfall starts and after every cycle of mechanized sweeping of traffic way. This operation must start from the right-hand lane along which traffic routs of public transport take place. Clustering of salt solutions on the bands of electro transport traffic routs is not permitted (Table 5).

Table 5 - Density of treatment with liquid DR regulated by the present technology

Reagent type	Units of measurement	Reagent consumption at air temperatures, °C
		from 0 to -2	from -2 to -4	from -4 to -6	from -6 to -8	from -8 to -10
Liquid	ml/m 2	25-35	35-45	45-55	60-70	70-80
Liquid	g/m 2	30-44	44-56	56-68	75-87	87-100

Note: application of liquid DR at air temperature below from -10 °C to -16 °C is possible only in case of special order of the strategic city main office according to standards: from 80 to 120 ml/m ² (from 100 to 150 g/m ²).

At heavy and long snowfalls and snow cover depth more than 2 sm only hard DR are applied (including combined DR). In case of special order of the strategic city main office hard DR application is done in combination with liquid DR and / or macadam with fraction 2-5 mm.

The possibility of random treatment of traffic way is foreseen, beginning from the most dangerous for vehicle movement areas - stop ways areas at crossings, square foot allocations at the public transport stops; steeps, up-hill gradients, bridges, overpasses, etc. In the periods of snowfalls at accumulated (or predicted) values of fallen snow more than 3 sm full treatment of the RFO traffic way is dine by hard DR. At application of hard DR in combination with liquid DR distribution density of each type of DR is defined according to order of the strategic city main office (Table 6).

Table 6 - Density of treatment with hard DR regulated by the present technology

Reagent type	Units of measurement	Reagent consumption at air temperatures, °C
		from 0 to -4	from -4 to -8	from -8 to -12	from -12 to -16	from -16 to -20
Hard	g/m 2	20-30	30-50	50-60	60-70	70-80

Note: application of hard DR at air temperature from -16 °C to -20 °C is reasonable together with granite macadam with fraction 2-5 mm at special order of the strategic city main office.

At snowfall and air temperature jump (in the range of negative temperatures) the DR consumption rate is determined taking into account air temperature gradient during 6 hours, preceded snowfall by interpolation method (Table 7).

Table 7 - Density of treatment with combined DR regulated by the present technology

Reagent type	Units of measurement	Reagent consumption at air temperatures, °C
		from 0 to -6	below -6
Hard combined DR (at this density of distribution must not exceed 200 g/m 2).	g/m 2	80-100	100-120

Treatment with granite macadam with fraction 2-5 mm:

At air temperatures below -15 °C one should treat the streets areas especially dangerous for vehicle movement, - stop ways areas at crossings, square foot allocations at the public transport stops; steeps, up-hill gradients, etc.

At air temperatures below -20 °C in the periods of snowfalls full treatment of traffic way of RFO is done. The similar technological operation must be done by the recommendation of the strategic city main office with consumption rate marking.

Density of distribution of granite macadam with fraction 2-5 mm is 100-200 g/m 2, total volume of application on the traffic way is not more than 15000 tons in a season. At the necessity of treatment of the traffic way with granite macadam with fraction 2-5 mm in combination with hard DR the density of distribution is defined according to the order of the strategic city main office.

Liquid and hard DR are delivered by the transport of different types according to the working regulations of shipping goods on the given transport type. Production marking is done according to the current standards and marking regulations of the enterprise-producer of reagents.

Liquid deicing reagents must have guaranteed storage life – not less than 24 months starting from the day of manufacture. Storage is realized according to technical standard documents of manufacturing enterprise, stipulated by current legislation, in tanks with capacity from 6m3 and more. After the expiry of guaranteed storage life the product must be inspected for the purpose of guaranteed storage life extension for one year. Filling up the machines-distributors with reagent is done by natural flow or by special pumps.

Hard and combined deicing reagents are left in the specialized soft containers of type «МCR» with a nett capacity up to 1000 kg, in polypropylene bags with weight from 25 kg and/or other types of consumption package, produced according to standard technical documents, stipulated by current legislation. Hard and combined DR must have guaranteed storage life - not less than 24 months from the day of manufacture. After the expiry of guaranteed storage life the product must be inspected for the purpose of guaranteed storage life extension at the condition of observations of rules and sealing capacity of producer’s package.

Hard and combined deicing reagents are kept in closed dry stores excluding direct sunlight penetration. One should not allow reagents having direct long-term contact with air till their consumption moment. In the open platforms the keeping of hard DR packed into special soft sealed containers (packages) located on trays is allowed. The platform on which packages and soft containers must be cleaned from protruding objects.

Deicing reagents and materials, supposed to circulation and delivery according to the state contract, must be accompanied with the following binding instruments, supplied by suppliers:

• -    shipping document with indicating technical conditions, GOSTs, enterprise (organizations) standards or other documents stipulated by current legislation, characterizing DM, and also numbers of the manufactured series;

• -    sanitary-epidemiological inspection report, given according to the procedure of sanitary-epidemiological expertise, inquiries, inspections, tests and toxicological, hygienic and other evaluation types confirmed by the order of the Federal Service for Supervision over Consumer’s Rights Protection and Human Welfare from 21.11.2005 N 776, or the State Registration Certificate, given according to the order provided by the decision of the Customs Union Commission of EurAsEC from 28.05.2010 N 299 «About the application of sanitary measures in Customs Union». For DM, that are beyond the state registration, it is necessary to have Expert report on the correspondence to the state sanitary-epidemiological rules and standards;

• -    document, that confirms quality (certificate of quality) of supplied products with marking DM name, number and amount of series, date of manufacture and manufacturer. In the certificate of quality the test results (including data of analyses of chemical content and properties) confirming the correspondence of DM quality indicators to technical requirements of the state contract and certified by the supervisory services (quality control department) of manufacturer or supplier;

• -    safety certificate

• -    positive findings of a State ecological appraisal of the Federal level (confirmed according to the procedure provided for by the legislation by the specially authorized state federal agency) on the suggested for delivery new DR (that failed the state ecological expertise as part of the conclusion on the present and preceding technologies) with stressing concrete technical conditions, standards of organizations, GOSTs or on identical Technology, with the suggested to the delivery new DR, with indication of concrete technical conditions, standards of organizations, GOSTs.

Without the above mentioned documents application of the DR is not allowed.

Sanitary and ecological requirements on site protection of urban environment:

Soil protection. To prevent accumulation in the city soils endurable and actively migrating components, elements and products of chemical and biological transformation of the DM the executive managers must provide strict observance of the fixed limits, recommendations and requirements on application (consumption rates of reagents and materials, multiplicity, time, method of treatment) of concrete products. Designated authority of environmental control, and also agencies and organizations realizing soil and ecological and technological monitoring, must conduct continuous control in soils for content of residual quantity of DM, possible dangerous metabolites or components of the used DM.

The object of prior and continuous control must be the soil of the territories adjacent to RFO and also the areas of water protective zones, places of public entertainment and the corresponding zones of roadside clear zones.

Open air protection . It is not permitted to apply (distribution on the RFO surface) DR at wind regime more than 4 m/s and without observation of given roadside clear zones.

During the treatments the Department of Housing, Utilities and Amenities and Provision of Urban Amenities (DHUA and PUA) together with other interested bodies organize carrying out random laboratory inspection in accredited laboratories (test centers) for residual content of DR in open air.

Water source protection Application of DM on the road facilities objects is permitted at the condition of meeting the requirements to the organization and observation of the corresponding regulations of the water protective zones (bands) for surface waters and protective sanitary zones of sources of drinking and household and cultural and general water management, provided with active regulatory documents.

Avoid allocating stores for keeping DM in sanitary zone of fisheries waters (not less than 2 km from banks) and at the distance of 300m from surface waters that have no fisheries importance.

Avoid applying DR in the first band of strict access area of the sources of centralized drinking and household and cultural and general water management and in feed zones 2 of band of sanitary protection zone of elevating centralized water sources.

Avoid discharging in water entities hazardous waste water which are formed at washing packing, cars, equipment, vehicle and work wear, used at work with DM. Avoid contamination with DM water entities which are thermal water receivers.

Longer set of observations is required to maintain the DR influence on ground waters. One should take into consideration that the pollutant accumulation process in natural habitat at specific time intervals can result in irreversible changes. It is necessary to develop measures on the mentioned influence, particularly obligatory observation of the requirements of the highways winter cleaning technology, the DR content, reagents consumption at different temperature ranges, and also exclusion of rotary snow clearance with penetration of pollutants into the green areas.

On the ground of the presented assessment of environmental impact, the process of it realization will not result in inadmissible ecological effects.

According to volume and content the DM correspond to ecological requirements legislated by the Russian Federation. Analysis of the given results of assessment of the DM environmental impact testifies to admissibility and ecological safety of anticipated effect.